Zoogeography
A SYMPOSIUM PRESENTED ON AUGUST 26-27, 1957,
AT THE STANFORD UNIVERSITY JOINT MEETING OF
THE AMERICAN INSTITUTE OF BIOLOGICAL SCIENCES
AND THE PACIFIC DIVISION OF THE AMERICAN
ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE
AND
A SYMPOSIUM PRESENTED ON DECEMBER 28, 1957,
AT THE INDIANAPOLIS MEETING OF THE AMERICAN
ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE
Edited by
CARL L. HUBBS
Publication No. 51 of the
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE
WASHINGTON, D. C. 1958
© 1958
The American Association for the
Advancement of Science
Library of Congress Catalog
Card Number 59-59993
Printed in the United States of America
The Horn-Shafer Company
Baltimore, Maryland
This volume is dedicated
to the memory of
two great zoo geographers,
CHARLES DARWIN and
ALFRED RUSSEL WALLACE
Whose observations and reflections on the distribu-
tion of animals provided much of the evidence that
led them, just one hundred years ago, to propose to
the world the epochal concept of Organic Evolution,
which unshackled the minds of men and helped in-
augurate the Age of Science.
Preface-
i\s science expands and fragments, reviews and
syntheses of broad areas become increasingly useful and necessary.
Among the more effective means of review and synthesis are the
symposia that are being held in increasing numbers at scientific
meetings. Two such symposia, in 1957, encompassed the field of
zoogeography, with due attention to the underlying data of geo-
morphology, paleoclimatology, paleontology, and physiology. The
fifteen papers that have become available from these two symposia
comprise a notable and rather comprehensive, though somewhat
diverse contribution to zoogeography and to its background sciences.
The extent of the contribution is greatly enhanced by the publica-
tion of these assembled papers as one of the symposium volumes of
The American Association for the Advancement of Science.
The first of these two symposia (Part I) was held under the prime
auspices of the Pacific Section of The Society of Systematic Zoology,
as a feature of the joint meeting of the American Institute of Biologi-
cal Sciences and the Pacific Division of the American Association
for the Advancement of Sciences, at Stanford University, in August,
1957. The symposium, bearing the ample title "The Origins and
Affinities of the Land and Freshwater Fauna of Western North
America," was abundantly cosponsored by the American Society of
Ichthyologists and Herpetologists (Western Division), American
Society of Zoologists, California Academy of Sciences, Pacific Coast
Entomological Society, Society for the Study of Evolution, and
Western Society of Naturalists. The fourteen papers ran through well-
attended morning and afternoon sessions on August 26 and 27, plus a
final panel discussion that nearly filled a spacious hall on the evening
of the second day. The large and attentive audiences demonstrated
the liveliness of the subject. Audience contribution was so spirited
at the panel discussion that I had difficulty in closing the session at
a reasonable hour.
It was my pleasure and privilege to act as general chairman of this
symposium. In conducting the sessions I was ably joined by the late
Karl P. Schmidt, as one of the last of his many generous acts, and
by George F. Edmunds, Jr. Panel members William H. Burt, Alden
H. Miller, Robert W. Pennak, Herbert H. Ross, and Dr. Schmidt
helped enliven the informal discussion.
VI PREFACE
Gratitude is expressed to the fifteen participants, all of whom
made notable contributions. Most of the contributors made an ex-
tensive and thorough analysis of their chosen subjects, and some
treated their topics in exhaustive and carefully documented style.
Credit for the success of this symposium goes to the symposium
committee, all of the University of California, Los Angeles: John N.
Belkin, chairman, Donald Heyneman, and Marietta Voge. These
zoologists were the prime actors in the conception of the idea, in
lining up the able speakers, in arranging and managing the sessions,
and, as not the least difificult task, in extracting manuscripts from
thirteen of the participants. They also helped in processing the manu-
scripts. I am sure that the officers of the meetings, the speakers, the
audiences, and, now, the scientific public, join me in expressing
hearty thanks to these tireless and self-efTacing workers.
The second symposium (Part II), which is herein represented by
three of the six papers, was a feature of the American Association
for the Advancement of Science meeting at Indianapolis, and was
held on December 28, 1957. It was entitled "Geographic Distribution
of Contemporary Organisms," and constituted Part I of the general
symposium, "Some Unsolved Problems in Biology, 1957." This was
a joint program of AAAS sections F (Zoological Sciences) and G
(Botanical Sciences), and was extensively cosponsored, by the
Society of Systematic Zoology, Ecological Society of America,
Genetics Society of America, American Society of Naturalists, and
Botanical Society of America. The program was arranged by Harold
H. Plough, of Amherst College, as Secretary of Section F, ably
assisted by Ernst Mayr of Harvard University and E. Raymond
Hall of the University of Kansas. Dr. Hall presided at the sym-
posium and contributes the introductory remarks.
We of the Pacific Section of the Society of Systematic Zoology
welcome the privilege of combining the papers resulting from our
symposium with the three submitted from the Indianapolis sym-
posium. As editor of the combined symposia, I want to express the
feeling that they very nicely complement the contributions from the
first symposium.
Carl L. Hubbs
Scripps Institution of Oceanography,
University of California,
La Jolla
October 1958
Contributors-
George A. Bartholomew, Department of Zoology, University of
California, Los Angeles
W. Frank Blair, Department of Zoology, University of Texas,
Austin
William H. Burt, Museum of Zoology, University of Michigan,
Ann Arbor
E. Raymond Hall, Museum of Natural History, University of
Kansas, Lawrence
William Hovanitz, Department of Biology, California Institute of
Technology, Pasadena
Carl L. Hubbs, Scripps Institution of Oceanography, University
of California, La Jolla
Philip B. King, General Geology Branch, United States Geological
Survey, Menlo Park, California
E. Gorton Linsley, Department of Entomology and Parasitology,
University of California, Berkeley
H. D. MacGinitie, Department of Biology, Humboldt State Col-
lege, Areata, California
Paul S. Martin, Geochronology Laboratories, L^niversity of
Arizona, Tucson
Alden H. Miller, Museum of Vertebrate Zoology, University of
California, Berkeley
Robert Rush Miller, Museum of Zoology, University of Michi-
gan, Ann Arbor
Kenneth C. Parkes, Carnegie Museum, Pittsburgh, Pennsylvania
Frank E. Peabody, Department of Zoology, University of Cali-
fornia, Los Angeles
Robert W. Pennak, Department of Zoology, University of
Colorado, Boulder
James A. G. Rehn, Academy of Natural Sciences of Philadelphia,
Pennsylvania
VI 1
Viil CONTRIBUTORS
Herbert H. Ross, Illinois Natural History Survey, Urbana
Donald E. Savage, Museum of Paleontology, University of Cali-
fornia, Berkeley
Jay M. Savage, Department of Biology, University of Southern
California, Los Angeles
Robert C. Stebbins, Museum of Vertebrate Zoology, University of
California, Berkeley
Contents-
Part I The Origins and Affinities of the Land and Freshwater Fauna
of Western North America
1 Evolution of Modern Surface Features of Western North
America
Philip B. King 3
2 Climate Since the Late Cretaceous
H. D. MacGinitie 61
3 The Role of Physiology in the Distribution of Terrestrial
Vertebrates
George A. Bartholomew 81
4 Evidence from Fossil Land Mammals on the Origin and
Affinities of Western Nearctic Fauna
Donald E. Savage 97
5 The History and Affinities of the Recent Land Mammals
of Western North America
William H. Burt 131
6 Origin and Affinities of the Birds of Western North
America (Editor's Note)
Alden H. Miller 155
7 Origin and Affinities of the Present Western North
American Reptile and Amphibian Fauna (Abstract)
Robert C. Stebbins 157
8 Evolution of a Coast Range Corridor in California and
Its Effect on the Origin and Dispersal of Living
Amphibians and Reptiles
Frank E. Peabody and Jay M. Savage 159
9 Origin and Affinities of the Freshwater Fish Fauna of
Western North America
Robert Rush Miller 187
10 Some Problems of Freshwater Invertebrate Distribution
in the Western States
Robert W. Pennak 223
ix
75401
X CONTENTS
11 Affinities and Origins of the Northern and Montane
Insects of Western North America
Herbert H. Ross 231
1 2 The Origin and Affinities of the Dermaptera and Orthop-
tera of \\^estern North America
James A. G. Rehn 253
13 Geographical Origins and Phylogenetic Affinities of the
Cerambycid Beetle Fauna of Western North America
E. Gorton Linsley 299
14 Distribution of Butterflies in the New World
William Hovanitz 321
Part II Geographic Distributioji of Contemporary Organisms
Introduction E. Raymond Hall 371
15 Pleistocene Ecology and Biogeography of North America
Paul S. Martin 375
16 The Palaearctic Element in the New World Avifauna
Kenneth C. Parkes 421
17 Distributional Patterns of Vertebrates in the Southern
United States in Relation to Past and Present En-
vironments
W. Frank Blair 433
General Conclusions
Carl L. Hubbs 469
Author Index 479
Index of Scientific Names 487
PAMTI
The Origins and Affinities of the
Land and Freshwater Fauna
of Western North America
1
Evolution of Modern Surface Features
of Western North America' /<- ^o^s Hn^-^
Philip B. King ^*^jl
United States Geological Survey, "
Menlo Park, California
In preparing a summary of the geological
background of the origins and affinities of the land and fresh-
water faunas of western North America, I am faced with several
difficulties.
First is the well-known lack of communication between the
sciences — a difference in language, in thinking, and in emphasis.
Thus, items that may be decisive to a zoologist may receive little
attention from a geologist. I welcome this opportunity to bridge a
gap between the zoological and geological sciences, to make a con-
tribution to a problem shared by both of us, and to enhance my own
education. At the same time, I must admit my present ignorance of
facets of the problem which are not geological, so that my analysis
in this paper must be mainly geological.
Then, too, even in making a purely geological analysis of the
problem one discovers wide gaps in the record, much evidence that is
equivocal rather than decisive, and much divergence among geolo-
gists as to what the evidence means. Broadly, the subject here
treated is the evolution through time of the geological features of
western North America, but the aspect of most zoological interest is
evolution of the surface forms only. For the record up to the middle
Tertiary, the surface forms must be deduced from rocks and struc-
tures of various ages, since none of the landscape of that time is
now preserved. Some fragments of surface forms as old as middle
Tertiary are preserved, and younger ones are preserved in in-
1 Publication authorized by the Director, United States Geological Survey.
3
p. B. KING
creasingly larger entitles, but even these surface forms are diversely
interpreted.
Finally, in so large a subject as western North America, I cannot
hope to do justice to all items and problems in a single paper. The
best one can do is to make a sampling and to hope that the samples
will be sufficiently representative of the whole. In this paper, the
samples will be chosen mainly from the segment in the United
States, partly because this is the region I know best, partly because
it is the region best known to geologists in general.
PRESENT GEOGRAPHY
Western North America is the region of the Cordilleran system of
mountain ranges, which extend unbroken along the Pacific Coast
from Alaska to Central America, and beyond, and inland 400 to 1,000
miles (Fig. 1). In Canada and the western United States they front
eastward on the Great Plains of the continental interior, but in
Alaska they front northward on a coastal plain at the edge of the
Arctic Ocean, and in Mexico they front northeastward on a coastal
plain at the edge of the Gulf of Mexico.
Geographically, the Cordillera north of Mexico is commonly
divided into two chains of ranges, one along the coast on the west,
another fronting the Great Plains on the east, with lower, more
broken ranges and plateaus intervening. Highest summits in North
America and in the United States are in the chain nearest the coast,
Mount McKinley in Alaska at 20,300 feet and Mount Whitney in
California at 14,495 feet. The summit of the interior chain. Mount
Elbert in Colorado at 14,431 feet, is somewhat lower. Many other
peaks in both chains project to heights nearly as great as the ab-
solute summits, and some of these have greater relief relative to
their immediate surroundings.
The western mountain chain includes the Alaska Range of Alaska,
and the Coast Mountains of British Columbia. In the United States
the chain is double, with low Coast Ranges on the west separated
by the Puget Trough, Willamette Valley, and Great Valley of
California from the higher Cascade Range and Sierra Nevada on the
east. A comparable pattern is expressed to the north, in Canada and
southeastern Alaska, by the offshore islands and Inland Passage,
and to the south, in Mexico, by the peninsula of Baja California
and the Gulf of California.
WO'
Miles
Fig. 1. Generalized map of North American Cordillera, showing
present topographic configuration. 1, Principal ranges. 2, Minor ranges.
3, Plateaus. 4, Lowlands, including plains of continental interior. 5, Sub-
merged areas, mainly ocean basins, but including continental shelves.
5
p. B. KING
The lower intermontane belt begins on the north with the wide
depression along the Yukon River in Alaska, continues southward
through various plateaus and ranges in Yukon Territory and British
Columbia, and includes the Columbia Plateau, Colorado Plateau,
and Basin and Range province in the western United States.
The eastern mountain chain is represented in Alaska by the Brooks
Range, and farther south, in Canada and the western United States,
by ranges that go under the general title of Rocky Mountains. The
Rocky Mountains end as a continuous barrier in northern New
Mexico, and for considerable distances southward the eastern ranges
are discontinuous and are of Basin and Range type.
In Mexico, the tripartite division of the Cordillera farther north
is lost. Here the Cordillera is essentially a high plateau, breaking off
in ranges on the east, west, and south, which form the three Sierra
Madres of that country — Oriental, Occidental, and del Sur.
These are the gross geographic forms of the Cordillera today, yet
to some extent they are accidental, and at most reflect only latest
warping of the crust. They have slight utility in an analysis of the
evolution of the surface features of the Cordillera, as each consists
of diverse geological features that have developed at different times
and in different ways. For example, the Sierra Nevada is an uplifted
block of crystalline rocks, whereas the Cascade Range, its orographic
continuation on the north, was built primarily by volcanic erup-
tions.
Present surface forms, rocks, and structures of the Cordillera have
developed through a long span of geologic time. Mountains arose
first in the western part of the region, in the middle of Mesozoic
time; others farther east developed in later Mesozoic and early
Tertiary times. Subsequently, in Tertiary and Quaternary times,
the initial mountains of the whole region were modified into the
forms we now see — by a continuation of crustal mobility, supple-
mented by volcanism, erosion, and sedimentation. The eastern part
of the Cordillera appears to be attaining stability now, so that the
modifying processes are becoming less active. On the west they are
still at work, as may be seen by the seismic and volcanic unrest near
the Pacific Coast, and one may anticipate continuing rearrangements
of the geography there. It is my purpose in the pages that follow to
elaborate on the sequence of events thus briefly outlined.
EVOLUTION OF MODERN SURFACE FEATURES 7
CONTROLLING PRINCIPLES
Nature of Mountain-Building Processes
Ultimate cause of mountain building is to be sought, not in such
merely superficial processes as erosion, sedimentation, glaciation, or
volcanism (however much these may shape the landscape in detail),
but in forces within or beneath the crust of the earth, which have
deformed the rocks and raised or lowered large areas of the surface.
Little is known about these forces themselves, but much has been
learned about their effects.
Some of the orogenic phases have been referred to as "revolu-
tions," because they are supposed to have brought about drastic
rearrangements of the geography and climate, and so modified the
environments as to cause far-reaching changes in distribution and
kinds of life. Detailed study shows, however, that the different
phases merge into each other, and that the changes they brought
about were evolutionary rather than revolutionary. Operation of
crustal forces was persistent through time, and although there were
certain crescendos, development was orderly and progressive, rather
than catastrophic.
Nature of Continental and Oceanic Crusts
In North America, at least, mountain building was a feature of the
edge of the continent — the border zone between the continental
platform and the adjacent ocean basins.
Sequentially, the processes may be divided into an initial or
geosynclinal phase, followed by an orogenic phase and a post-
orogenic phase, the nature of which will be examined later. The
phases were prolonged. In the Cordilleran region the geosynclinal
phase endured for at least 350 million years, from Cambrian to
Triassic; the orogenic phase, for about 100 million years, from
Jurassic to Paleocene; and the post-orogenic phase, for about 50
million years, from Eocene to present (Table I).
Continental platforms and ocean basins are fundamentally
different elements of the crust of the earth (the crust is the relatively
thin skin of rocks that overlies the dense material of the interior of
the earth). Their surfaces stand today at different levels: the con-
tinental averages about half a mile above sea level; the oceanic, 3
miles or more below sea level. The two levels reflect contrasting
8
p. B. KING
average compositions of the crust beneath the two areas (Ewing and
Press, 1955). Crust of the ocean basins is made up of relatively
dense rock, called sima, with an average composition about like
basalt, and with a thickness beneath the ocean water of about 6
miles. Simatic material like that beneath the oceans also forms the
base of the thicker crust of the continental platforms, but most of
the thickness of the platforms consists of lighter rock, called sial,
of about the composition of granite. Continental crust has a thick-
ness on the order of 20 miles.
Table I. Subdivisions of Later Geologic Time, and Their Relation to
the Phases of the Evolution of the Cordilleran Region
Era
System
Series
Phases in Evolution
of the Cordillera
Quaternary
Recent
Pleistocene
Cenozoic
Tertiary
Pliocene
Miocene
Oligocene
Eocene
Paleocene
Post-orogenic phase
Mesozoic
Cretaceous
Jurassic
Triassic
Orogenic phase
Paleozoic
Permian
and older
Geosynclinal phase
These differences in composition and thickness of the crust under-
score a widely held belief in the permanence of continents and ocean
basins, and give little comfort to notions of vanished lands within
the ocean areas. To create and destroy such lands would involve not
merely changes in level, but changes in crustal composition. It is
agreed that the Pacific Ocean basin, in particular, was a permanent
crustal and topographic feature throughout known geologic time.
Even the relatively modest ''borderlands" that some geologists have
believed once existed along or off the present coasts must each be
EVOLUTIOX OF MODERN SURFACE FEATURES 9
appraised critically on their individual merits. Thus, the supposed
borderland of "Cascadia" which has been postulated along the
Pacific Coast of North America, if it existed, could hardly have
extended beyond the edge of the present continental shelf, the sub-
merged part of the continental crust.
This is not to say that certain modifications of the doctrine of
permanence are unworthy of consideration :
Some geologists believe that the plates of continental crust, al-
though permanent, have drifted through time across the subcrust, so
that their positions have shifted with respect to other continents,
and to the poles. Although there is a great deal of persuasive evi-
dence for such an interpretation, much more evidence, both geologi-
cal and geophysical, is against it. The possibility of continental drift
need not concern us greatly in our present problem ; even under such
an hypothesis North America has long retained about the same
position with respect to Asia, South America, and the Pacific Ocean.
Other geologists believe that, although present oceanic areas are
unlikely ever to have been continental, the continental plates may
have increased in area through time by processes of accretion — by
building of sediments over the edges of the oceanic crust, and their
subsequent consolidation into continental crust during mountain
building. Western North America may have increased in area,
rather than diminished through recorded geologic time, by incre-
ments along its Pacific margin, especially during the orogenic period
of the latter half of Mesozoic time. The area of the Coast Ranges of
California, for example, may have been continental during only the
last 100 million years of geologic time; before that, open ocean.
GEOSYNCLINAL PHASE
General Concepts
Growth of a mountain system ordinarily begins with a geosynclinal
phase, or time of quiet preparation, when marine sedimentation
went on over the site of the future mountain belt. A geosyncline is an
area where sedimentation proceeded actively, to the accompaniment
of more or less crustal movement (Kay, 1947). Many geologists have
believed that the geosynclines of North America were features that
developed within the continental platform, between a central nucleus
and the "borderlands" along the edge. Now, there is a growing
10 p. B. KING
suspicion that geosynclines were features marginal to the continental
platform, that overlapped its edges, it is true, but that, on the farther
side, may have been built outward into the ocean basins (Longwell,
1950, pp. 420-422).
The part of the geosyncline toward the continent, termed the
miogeosyndine, was a shelf underlain by continental crust that re-
ceived various sorts of shallow-water sediments. Mobility of the
crust beneath it was greater than that in the continental interior, yet
was expressed mainly by subsidence during sedimentation, which
permitted gradual accumulation of a thick body of sediments.
The part of the geosyncline toward the ocean, termed the eugeo-
syncline, was a more mobile area, even during early phases of its
history, with deeps, shallows, and strips of land that were shaped by
crustal forces, and with volcanic eruptions whose products were
mostly spread on the sea floor, but which in places were built up
into islands. Later, parts of the geosynclinal phase in this area
blended w^th the succeeding orogenic phase. The extent to which the
eugeosyncline formed over a continental or over an oceanic crust is
uncertain, as the basement on which the eugeosynclinal deposits
were laid has seldom been raised to the surface; at least the outer
edge of the eugeosyncline was probably built over an oceanic area.
Our study of western North America can best begin at the start of
the Mesozoic era, or late in the geosynclinal phase of development
of the Cordillera, and immediately before the orogenic phase.
Eugeosynclinal Area of the Cordillera
A eugeosynclinal environment persisted for a long period in much
of the western part of the Cordilleran region, with an irregular
eastern boundary. It extended about to the site of Owens Valley
east of the southern Sierra Nevada, east of Winnemucca in north
central Nevada, and across Oregon into westernmost Idaho (Fig. 2).
The environment is expressed by a characteristic suite of deposits
— volcanics (lavas, tuffs, and breccias) many times repeated and of
great thickness, and associated argillites, graywackes, and cherts,
nearly all of which must have been laid down beneath the sea
(Eardley, 1947, pp. 316-328). The eugeosyncline originated at an
early period, for deposits of eugeosynclinal type contain Silurian
and Devonian fossils in the Klamath Mountains and Ordovician
fossils in north central Nevada and the eastern Sierra Nevada, but
EVOLUTION OF MODERN SURFACE FEATURES
11
its record is most extensively preserved in the later Paleozoic,
Triassic, and Jurassic rocks. This is not the place to discuss the com-
plexities and variations of these primarily marine deposits, as we
are more concerned with the land areas.
Miles
Fig. 2. Map of western United States, showing generalized conditions
during middle part of the geosynclinal phase of the development of the
North American Cordillera (Pennsylvanian and Permian time). 1,
Oceanic area. 2, Eugeosynclinal area; stars indicate approximate posi-
tions of volcanic centers. 3, Miogeosynclinal area. 4, Foreland area, or
continental interior; partly land, but intermittently covered by ephemeral
seas. 5, Deeper sedimentary basins in continental interior. 6, Folds and
fold belts. 7, Direction of transport of sediments.
Within the eugeosyncline, indications of any land areas are elu-
sive. Ephemeral islands are suggested by occasional gaps in the
sequence (such as absence of any Triassic rocks in parts of the Sierra
Nevada) and by local conglomerate layers. Many of the volcanic
units change markedly in thickness within short distances, as though
12 p. B. KING
they were built up irregularly on the sea floor, and perhaps in places
to the surface. It has been thought that in some areas sedimentation
was interrupted by deformation during Paleozoic time, before the
close of the geosynclinal phase (Eardley, 1947, pp. 328-334), so that
fold ridges may have emerged as land areas. Indications of such
deformation are based on obscure evidence that can be otherwise
interpreted, so that any occurrence of fold ridges produced by the
deformation remains to be proved.
At the eastern edge of the eugeosynclinal area the record of
emergence is more definite. Differences between Triassic and Jurassic
deposits east and west of a belt through the center of the Great Basin
have long been known, and are sufficiently marked as to suggest that
the two sets of deposits were separated by a land barrier (Nolan,
1943, p. 158) (Fig. 3). Geologic work in north central Nevada during
the last few decades has indicated something of the antecedents of
this barrier (Roberts et al.). Older Paleozoic rocks that had been
laid down in the eugeosyncline were deformed and thrust eastward
over the miogeosynclinal area, were then eroded, and were over-
lapped from the east by Pennsylvanian deposits (Fig. 2). Angular
unconformities within the higher Pennsylvanian and the Permian
attest a continued instability of the area. In the Great Basin re-
gion, the Triassic and Jurassic barrier must have been inherited
from this belt of Paleozoic deformation. Stratigraphic data indicate,
however, that the barrier continued northward from the Great
Basin toward Canada, where its origin and prior history are less
clearly indicated.
Miogeosynclinal Area of the Cordillera
A miogeosynclinal environment prevailed over the continentward
side of the Cordilleran geosyncline. During Paleozoic time, when the
miogeosyncline received thick accumulations of limestone, its eastern
edge extended across the site of the Rocky Mountains to the Great
Plains near the Canadian border, but farther south in Utah extended
no farther east than the boundary between the Great Basin and
Colorado Plateau.
Through much of the segment in the western United States, there-
fore, a wide area of the Cordilleran region lay east of the geosyncline
— the present Colorado Plateau and the Rocky Mountains of Wyo-
ming, Colorado, and New Mexico. During Paleozoic time most of
EVOLUTION OF MODERN SURFACE FEATURES
13
this area had a history Hive that of the remainder of the stable con-
tinental nucleus, intermittently emergent or receiving the thin de-
posits of ephemeral seas. In later Paleozoic time, however, part of it
began to lose its previous stability. On the site of the Rocky Moun-
130"
120*
100°
.500
1000
Miles
Fig. 3. Map of western United States, showing generalized conditions
late in the geosynclinal phase (Triassic and Early Jurassic time). 1,
Oceanic area. 2, Eugeosynclinal area; stars indicate approximate positions
of volcanic centers. 3, Miogeosynclinal area. 4, Sedimentary wedges that
spread from the geosynclinal area across the foreland: (a) dominantly
marine, (b) dominantly continental. 5, Land areas that probably did not
receive deposits.
tains of Colorado and New Mexico several broad fold ridges were
raised; troughs subsided rapidly between them and received thick
accumulations of waste eroded from the uplifts (Fig. 2). These
"ancestral Rocky Mountains" are the ends of one of the w^estern
branches of the mountain belt that formed during Paleozoic time
14 P. B. KING
along the southeastern side of North America. The zone of weakness
that they created in the crust greatly influenced the configuration
of the Rocky Mountain structures that developed there later (Bur-
bank and Lovering, 1933, pp. 277-301).
By the first half of Mesozoic time, considerable rearrangements
had taken place in the miogeosynclinal area. The land barrier be-
tween the miogeosyncline and eugeosyncline, whose development
had begun in later Paleozoic time, restricted the extent of Triassic
and Jurassic sedimentation on the west; troughs along the eastern
side of the barrier received a considerable thickness of marine sedi-
ments (Fig. 3). To the east, deposits spread beyond the Paleozoic
miogeosyncline, wedging out in the Great Plains area east of the site
of the Rocky Mountains. At least in the south, most of these eastern
deposits were land-laid, and in the Colorado Plateau include such
characteristic units as red stream deposits of the Triassic (Moenkopi
and Chinle formations), great sand dune deposits of the Late Triassic
and Early Jurassic (Wingate and Navajo sandstones), and vari-
colored stream deposits of the Late Jurassic (Morrison formation)
(Baker et al., 1936, pp. 48-55).
During Cretaceous time, sedimentation continued in much the
same region as that covered by the Triassic and Jurassic deposits,
but the Cretaceous deposits are so closely related to the orogenic
phase of Cordilleran history that it is best to discuss them later.
OROGENIC PHASE
General Concepts
Terminology. The word orogeny means mountain building, yet to
a degree its use has been perverted by geologists. During early work
in mountain regions, geologists observed everywhere the strong
disturbance of their rocks and assumed that such disturbances were
the cause of the mountains themselves. Now we know that these
disturbances, while an essential step in the process, did not produce
strong mountainous relief; such relief was only acquired later, in the
post-orogenic phase. Use of the term orogeny for the deformative
phase of mountain growth has nevertheless persisted for want of a
better name; it is convenient to use it here.
The Orogenic Process. The geosynclinal phase of mountain
growth blended, as stated, wath the succeeding orogenic phase, when
EVOLUTION OF MODERN SURFACE FEATURES 15
mobility of tlie crust reached its climax. Blending was greatest in the
eugeosynclinal area, which possessed considerable mobility from the
beginning; the orogenic climax was reached earliest here. During
this climax the eugeosynclinal sediments and volcanics were strongly
compressed and deformed, were more or less metamorphosed, and
were invaded by small to large masses of plutonic rocks, ending with
masses of granitic composition.
Detritus eroded from the newly deformed belt was in part washed
off its oceanward side, where much of its record has been lost, and
was in part spread inland as great sheets of clastic rock that tapered
across the miogeosynclinal area, which was as yet undeformed.
These clastic sedimentary deposits comprise as much as half of many
miogeosynclinal sequences.
As crustal compression progressed, the miogeosyncline itself was
deformed, sometimes in an orogenic period that appears to be dis-
tinct from that in the eugeosynclinal area. Its bedded sedimentary
rocks were thrown into folds and broken by thrust faults along which
rocks above were moved greater or less distances toward the con-
tinental interior. Deformation usually progressed as far as the inland
edge of the geosyncline, where the sediments thin out, and the
interior region was left undeformed. In places, however, deformation
was carried beyond the edge of the geosyncline, as in the southern
Rocky Mountains, within the region we are considering.
Effect on Surface Features. The orogenic phase so consolidated
and strengthened the rocks of the eugeosynclinal area that they
became permanent additions to the continental mass. Also, it
ordinarily expelled the seas from the whole geosynclinal area for a
long period — or permanently. Nevertheless, there is much question
as to how greatly the orogenic phase increased the surface relief.
Restoration of folds and fault blocks that are now eroded gives the
impression that orogeny might have produced ranges higher than
the Himalayas (Fig. 6), but orogeny may have proceeded so slowly
that various leveling processes nearly kept pace with it — erosion
wearing off the upraised areas and sedimentation filling the de-
pressed areas. If so, creation of truly mountainous relief is largely a
post-orogenic event, resulting from processes different from those in
operation during the orogenic phase.
Orogenic Land Bridges. Orogenic belts of this sort are thousands
of miles long. Some terminate laterally by fading out of effects of
16 p. B. KING
deformation, but most, in a sense, are endless. Those along the edges
of the Atlantic Ocean run out to sea and apparently are broken off at
the edges of the continental shelves so that their further extensions
are lost. Those around the margins of the Pacific Ocean, however,
such as the belt of the North American Cordillera, are continuous or
nearly so from one continent to the next, and they appear to be
parts of a single great zone of deformation. In the circum-Pacific
zone, orogeny created potential conditions for land bridges between
the continents, and they came into being from time to time during
the orogenic and post-orogenic phases. Such land bridges were along
the present and observable orogenic trends; as already noted, no
land bridges could have formed across the ocean basins.
The record suggests that land connections along the circum.-
Pacific orogenic belt were firmer and more frequent between North
America and Asia than between North America and South America.
Much of the crust beneath the seas of Middle America, as in the Gulf
of Mexico and Caribbean Sea, is more oceanic than land-laid and
seems to be in process of transformation into land-laid crust by
sedimentation on its surface, and by magmatic transformation
within it (Ewing et al., 1957, pp. 909-911). At least a part of the firm
land connection between the two continents in the Central American
isthmus, especially in Nicaragua and Costa Rica, was built up rather
recently by volcanic eruptions: "To be sure it is in fact an isthmian
link. But why is it such an outrageous isthmian link?" (Woodring,
1954, p. 730). Before development of the isthmus, the lands along
the orogenic belt between North and South America were mainly
disconnected islands.
Deformation of Eugeosynclinal Belt of Cordillera
Cordilleran eugeosynclinal rocks were deformed, metamorphosed,
and invaded by granitic rocks in the middle and last half of the
Mesozoic era, during a time referred to as the Nevadan orogeny (Fig.
4)-
On the west slope of the Sierra Nevada, for which the orogeny is
named, Jurassic rocks are steeply upturned, altered, and invaded by
plutonic rocks, whereas Cretaceous rocks lie on their deeply eroded
edges with little disturbance. From this relation and from more
detailed evidence we need not mention here, some geologists have
concluded that at least the deformational phase of the orogeny in the
EVOLUTION OF MODERN SURFACE FEATURES
17
Sierra Nevada, and perhaps also the plutonic phase, was accom-
pHshed during a relatively brief interval near the end of Jurassic
time, but before its close (Taliaferro, 1942, pp. 102-105). It has been
inferred, as well, that much of the deformation in the eugeosynclinal
I00»
3 VpA /;//
500
1000
Miles
Fig. 4. Map of western United States, showing generalized conditions
during early part of orogenic phase (Late Jurassic and Early to Middle
Cretaceous time). 1, Oceanic areas. 2, Clastic deposits laid down along
edges of orogenic belts; arrows indicate direction of transport of sedi-
ments. 3, Marine deposits of foreland area. 4, Folds produced by Nevadan
orogeny, late in Jurassic and early in Cretaceous time. 5, Folds produced
by orogeny later in Cretaceous time. 6, Miogeosynclinal area. 7, Volcanic
centers.
belt to the north and south, where age relations are less clear, took
place during the same epoch.
Various considerations suggest that events were more complex
and prolonged than thus implied, even in the Sierra Nevada region.
The eugeosynclinal rocks were first folded, steeply upturned, and
18 p. B. KING
regionally metamorphosed, then were invaded by successive masses
of granitic rocks — a sequence which began later than deposition of
the youngest Jurassic rocks of the Sierra, and must have continued
for a long time thereafter. Moreover, radiometric determinations on
the granitic rocks indicate that they themselves were injected over a
period of more than 60 milHon years, or between Middle Jurassic and
Middle Cretaceous times, with the oldest to the west in the Klamath
Mountains and western edge of the Sierra Nevada, and the youngest
near the east edge of the Sierra Nevada (Evernden et al., 1957).
Elsewhere in the eugeosynclinal belt where evidence is available, the
climax of the orogeny varies in age. In the Hawthorne-Tonopah area
of southwestern Nevada thrust faulting was in progress during
deposition of Lower Jurassic sediments (Ferguson and Muller, 1949,
p. 13), whereas in northern Baja California Lower and Middle
Cretaceous rocks are involved in the orogeny, and are unconformably
overlain by Upper Cretaceous rocks (Woodford and Harriss, 1938,
pp. 1328-1330).
Evidence is inconclusive as to the nature of the lands produced by
the Nevadan orogeny. Sediments laid down east of the deformed
belt suggest that the climate there was arid during Triassic and Early
Jurassic times, and became more humid later, but these conditions
were influenced by so many unknown factors that they are difficult
to relate to local topography. As mentioned earlier, a land barrier
existed on the site of the Great Basin during Triassic and Jurassic
times, but during initial phases of the Nevadan orogeny the eugeo-
synclinal belt west of the barrier probably remained low; meta-
morphism and plutonism of the rocks of the belt indicate that they
were deformed at a considerable depth, so that first orogenic move-
ments may have been more downward than upward. Thereafter,
during forcible injection of the younger plutonic bodies, the surface
of the deformed belt may have risen, and its erosion may have con-
tributed to the large volumes of sediment laid down east and west
of it (described under succeeding headings). Such erosion products
do not necessarily imply very great relief in the belt ; they might as
plausibly suggest that leveling by erosion nearly kept pace with
uplift.
Be that as it may, it is worth emphasizing that the topographic
forms produced by deformation of the eugeosynclinal rocks had little
EVOLUTION OF MODERN SURFACE FEATURES 19
similarity to any modern features. The present Sierra Nevada, for
example, was produced much later by tilting and faulting of a block
within the orogenic belt; other parts were variously raised, broken
up, depressed, or buried.
Sedimentation West of Nevadan Belt
Beyond the strongly deformed and altered rocks of the Nevadan
orogenic belt, west of the Sierra Nevada and southwest of the
Klamath Mountains, are less altered Upper Jurassic and Lower
Cretaceous strata — the Knoxville formation and Shasta series — a
sequence of marine shales, sandstones, and minor conglomerates.
These are turned up against the Coast Ranges on the west side of
the Sacramento Valley, where they are as much as 8 miles thick.
It has been thought that they were not laid down until after the
Nevadan orogeny, and that they accumulated in a new trough that
developed west of the Nevadan belt and east of the ancestral Coast
Ranges along the Pacific Ocean, with most of the sediments derived
from the latter (Anderson, 1938, pp. 25-29; Taliaferro, 1942, pp.
103-104). These views require reexamination, as recent paleontologic
work indicates that part of the deformed Jurassic rocks of the Sierra
Nevada on the east (Monte de Oro formation) are of the same age as
the Knoxville, and that a large part of the Franciscan group of the
Coast Ranges, once thought to underlie the Knoxville, is as young as
early Late Cretaceous (McKee et al., 1956, pp. 3; Irwin, 1957). The
dates of orogenic events and distribution of lands and seas during
Late Jurassic and Early Cretaceous time must therefore have been
quite different from those that have been inferred.
It may be that deformation of the rocks during the Nevadan
orogeny diminished westward as well as eastward, so that the sites
of the Sacramento Valley and Coast Ranges were little disturbed
during the orogeny. The Franciscan, Shasta, and Knoxville strata
may have been deposited before, during, and after the climax of the
Nevadan orogeny, and have been laid down along the edge of the
continent and on the continental slope, in part beneath ocean water
of considerable depth. Further critical studies are needed to deter-
mine the source of this great body of sediments, but part of them,
perhaps the greater part, must have been derived from erosion of
rising lands in the orogenic belt to the east and northeast (Fig. 4).
20 P. B. KING
Existence during this time of lands farther west, along the Pacific
border, has been stoutly maintained by various protagonists, but
evidence for such lands seems to have little substance.
Sedimentation East of Nevadan Belt
During Cretaceous time, especially during its latter half, a great
seaway extended along the eastern side of the Cordilleran region,
from the Gulf of Mexico to the Arctic Ocean (Fig. 4). In mid-latitude
in the United States its deposits were spread eastward into the con-
tinental interior as far as Kansas and Iowa and westward into the
Cordilleran region as far as central Utah.
The eastern deposits were shallow-water shales and chalks of no
great thickness, but westward near the front of the Rocky Moun-
tains these pass into a dominantly shaly mass about 2 miles thick.
Beyond, wedges of sandstone appear in the shales and thicken west-
ward, with interbedded layers of coal that formed in swamps and
floodplains along the edge of the seaway. The westernmost preserved
Cretaceous rocks, near the west edge of the present Colorado
Plateau, are nearly 4 miles thick and are dominantly of continental
origin; they include coarse conglomerates that formed as piedmont
deposits adjacent to mountainous lands (Spieker, 1949, pp. 60-68).
The source of these coarse, land-laid beds was clearly to the
west in the area of the present Great Basin (Fig. 4). The land barrier
that existed there during late Paleozoic and early Mesozoic time was
evidently enlarged eastward during Cretaceous time to include the
former miogeosynclinal area. This enlargement was the result of
folding and faulting, rather than of mere upwarp, and produced a
surface of varied relief that was rapidly eroded.
Deformation of Miogeosyncline and Foreland
During latest Cretaceous and Paleocene times, orogeny progressed
into the eastern part of the Cordillera, deforming the rocks of the
Colorado Plateau and Rocky Mountains as far as the Great Plains
(Fig. 5). This deformation, which completed the orogenic phase of
Cordilleran evolution, has been termed the Lar amide oroge?iy. It has
commonly been thought of as distinct, both in place and time, from
the Nevadan orogeny, but such distinctions are between end mem-
bers of a continuing sequence of deformation. Deformation began
earliest toward the west, then expanded across the miogeosynclinal
EVOLUTION OF MODERN SURFACE FEATURES
21
area toward the continental interior; the Cretaceous deformation of
the Great Basin area occupies an intermediate position in place and
time. In any particular part of the eastern Cordillera the observ-ed
w&E*
N5
•w
,500
1000
Miles
Fig. 5. Map of western United States, showing generalized conditions
during late part of orogenic phase (latest Cretaceous and Paleocene time).
1, Oceanic area. 2, Marine sediments along Pacific border. 3, Folds pro-
duced by Laramide orogeny: (a) narrow folds and fault blocks in geo-
synclinal sediments, (b) broad folds in foreland area, involving basement
rocks. 4, Volcanic centers. 5, Transverse faults with major components of
lateral displacement. 6, Sedimentary basins of nonmarine deposition be-
tween folds and along their eastern border. 7, Land areas; shaded areas
indicate approximate extent of plutonic rocks of Nevadan age that had
been unroofed by erosion,
deformation of the rocks can be placed in this sequence only if
stratigraphic evidence is available; as a matter of convenience, all
such structures are ascribed to the Laramide orogeny.
Laramide movements compressed the sedimentary rocks of the
miogeosyncline into long, closely spaced folds and thrust blocks,
22
p. B. KING
characteristic examples of which may be seen in the northern Rocky
Mountains of western Alberta and northwestern Montana, and in
the central Rocky Mountains of western Wyoming and southeastern
Idaho. Farther south they have been obscured by later structures
of the Basin and Range province.
From central Montana southward, Laramide deformation ad-
vanced well beyond the miogeosynclinal belt, disturbing part of what
had previously been the foreland, or border of the stable continental
I I I I L.
.10
20 Miles
Fig. 6. Diagram of a typical mountain uplift in Southern Rocky
Mountains. The example chosen is the Uinta Mountains of northeastern
Utah. The block in the background shows the feature without erosion of
the uplifted strata; that in the foreground the present topography.
(After Powell, 1876.) a, Pre-Cambrian rocks (here, sedimentary strata;
in other uplifts of Rocky Mountains, generally plutonic and meta-
morphic rocks), b, Paleozoic strata, c, Mesozoic strata, d, Tertiary strata.
interior, and raised the central and southern Rocky Mountains of
Wyoming, Colorado, and adjacent states. Here, the sedimentary
cover was mainly thinner than in the miogeosyncline, and deforma-
tion created structures of a different style — broad-backed ranges of
diverse trend and spacing, in which Precambrian basement rocks
were so uplifted along the cores as to be uncovered by erosion, the
ranges being separated by broad basins (Fig. 6).
Many of these structures were newly born during the Laramide
orogeny, but in the southern Rocky Mountains of Colorado and New
Mexico they were guided by structures of the "ancestral Rocky
Mountains" already referred to. Here, some of the Laramide ranges
nearly correspond to uplifts that formed in late Paleozoic time,
EVOLUTION OF MODERN SURFACE FEATURES 23
whereas others were produced by close folding of sediments which
had been deposited in troughs between the earlier uplifts (Burbank
and Lovering, 1933, pp. 283-301).
The foreland ranges of the southern Rocky Mountains are sep-
arated from the miogeosynclinal structures in the Great Basin on
the west by the Colorado Plateau, which remained as a more stable
block during Laramide orogeny. Its rocks were broadly upwarped
and downwarped in much the same manner as those of the Rocky
Mountains, but they attained less structural relief. A typical uplift,
in the Kaibab and Coconino Plateaus of the Grand Canyon district,
is still sheeted over by sedimentary rocks, except where trenched by
the Colorado River, and it is bounded at the sides by steeply sloping
monoclinal flexures.
Record of the Laramide orogeny may be read in deposits of latest
Cretaceous and Paleocene ages which are preserved to great thick-
ness in basins between the ranges of the Rocky Mountains, such as
the Bighorn and Powder River basins of Wyoming — and in the Great
Plains east of the mountains, as in the Denver and Williston basins
of Colorado and North Dakota (Fig. 7). The deposits are somber-
colored land-laid clays and sands with layers of coal, whose upper
parts contain increasing quantities of detritus eroded from the cores
of the ranges.
Much labor has been expended in a search for immense uncon-
formities that were supposed to be concealed in these deposits, and
which would mark the time of upheaval of the intervening ranges,
but it is now clear that the deposits are essentially conformable
sequences. Very likely the original areas in which the deposits were
laid did not greatly dififer from the present structural basins, and the
deposits were thick, local accumulations derived from erosion of
ranges uplifted in the immediate vicinity. The latest Cretaceous and
Paleocene deposits are therefore unlike the broad sheet of marine
sediments of earlier Cretaceous time, which were derived from
erosion of deformed areas far to the west.
Laramide orogeny destroyed the great Cretaceous seaway of the
eastern Cordillera (Fig. 5). Except for a brief marine incursion in
the northern Great Plains during late Paleocene time, represented by
the Cannonball member of the Fort Union formation, seas returned
no more to the region, and all succeeding deposits were land-laid.
The Upper Cretaceous and Paleocene land-laid deposits evidently
24
p. B. KING
,100
400 Miles
Fig. 7. Map of central and southern Rocky Mountains, showing up-
lifts and basins of Paleocene and Eocene time. 1, Folds and fault blocks
in geosynclinal sediments. 2, Uplifts east of geosynclinal area, with out-
crops of pre-Cambrian basement rocks in their higher parts. 3, Basins
that received Paleocene sediments. 4, Basins in which Eocene sediments
were deposited over Paleocene sediments. 5, Areas of lake deposits,
mainly of Eocene age.
EVOLUTION OF MODERN SURFACE FEATURES 25
formed in forested floodplains and swamps, in a warm humid climate,
probably at an altitude no more than a thousand feet above sea level ;
Paleocene rocks contain small mammals that were members of an
arboreal forest community (Van Houten, 1948, p. 2105).
The ranges that intervened between the areas of deposition were
outlined in much their present form during the Laramide orogeny,
but could not have projected to their present bold heights, or they
would have prevented an ingress of moisture-laden winds from the
west and the climate would have been much drier (Mackin, 1937,
p. 819). More likely, their summits rose no more than a few thousand
feet above the basin floors ; their rocks were greatly uplifted by the
orogeny, but were worn down nearly as rapidly as they arose.
POST-OROGENIC PHASE
We pass now to that part of our story which is perhaps of greatest
interest to this audience — the shaping of the Cordilleran mountain
belt after the orogenic phase, in Tertiary and Quaternary times.
General Concepts
Crustal unrest continues in a mountain belt long after the orogenic
phase. The orogenic phase itself created many modifications in the
crust and subcrust, which were stable so long as the region was in the
grip of strong compression. Relatively light sialic crust might be
thickened as a root beneath the mountain belt, and sialic crust might
be added along the oceanward edge where only simatic crust was
present before. Although the orogeny generally thickened and
strengthened the continental crust, it also produced transverse flaws
and zones of weakness, by differential movement between adjoining
segments of the belt.
With relaxation of compression, there was a shift to a new equi-
librium. Overthickened parts of the crust might have risen buoy-
antly, or the mountain root might have been dissipated by subcrustal
transfer of material. Further movements might have followed the
zones of weakness, or such zones provided routes for the ascent of
magmas.
These processes of readjustment are complex, not well understood,
and much debated, but their surface manifestations are more evident
and can be read in the rocks, their structures, and in the changes in
26 P- B. KING
the landscape. Such modifications of the Cordilleran region have
been perhaps as great as in any other mountain belt, and include :
1. Continued differential movements between mountain up-
lifts and intervening basins in the epochs immediately succeeding
the orogeny, or perhaps in the waning stages of the orogeny. Some,
but not all, of the basins in the central and southern Rocky Moun-
tains were thus accentuated during Eocene and Oligocene time.
2. Breakup of extensive areas of the deformed terrain by block
faulting to produce a succession of mountains and intervening
basins. Such was the fate of the former miogeosynclinal area and the
eastern part of the eugeosynclinal area in mid-section in the United
States — in the Great Basin — but similar structures extend far to the
south and southeast through the more inclusive Basin and Range
province.
3. Regional uplift of broad areas without much folding or fault-"
ing, especially late in the post-orogenic period. The greatest of these
uplifted regions encompassed virtually all the central and southern
Rocky Mountains, the Colorado Plateau on the west, and the Great
Plains on the east ; smaller and more complex areas of regional up-
lift occur farther west, as in the Sierra Nevada and Cascade Ranges.
4. Volcanic activity and accompanying shallow intrusions. Some
volcanism took place locally in the Cordilleran region even during
the orogenic phase; in the post-orogenic phase it occurred in varying
degree, at one time or another, in almost every part of the region.
Volcanism was concentrated more in some areas than others, how-
ever, and in some of them was long persistent. By far the most
voluminous and persistent volcanism was in the northwestern
United States, in the Columbia Plateau and Cascade Range.
5. Development of faults along which movements were not up-
ward and downward, but along which one side moved laterally
against the other. The most famous of these is the San Andreas
fault of California, but many more occur near it and others else-
where; some, perhaps, are as yet undetected.
6. Continued orogeny, marked by local subsidence and sedimen-
tation, uplift, and deformation along the ocean ward side of the
mountain belt. In the Coast Ranges of California, strata as young as
the Pliocene and Pleistocene are strongly folded in places, and the
seismic record indicates that the crust is still unstable.
EVOLUTION OF MODERN SURFACE FEATURES 27
Eastern Part of Cordillera (Central and Southern Rocky Mountains,
Colorado Plateau, and Great Plains)
Eocene Environments. We have arbitrarily chosen the end of
Paleocene time as the close of the orogenic, or Laramide, phase in
the eastern part of the Cordillera, but environmental changes from
Paleocene into Eocene were evolutionary rather than revolutionary.
It is true that in some of the intermontane basins initial coarse
Eocene deposits overstep the edges of Paleocene and earlier rocks
with marked unconformity, and that this has sometimes been
thought to have followed immediately on the climax of the Laramide
orogeny. We have seen, though, that Laramide structures had been
in process of growth long before the end of Paleocene time; the
Eocene deposits thus record merely a resumption of sedimentation
after the crust had reverted to relative stability.
Within the mountain belt, subsidence of the basins continued
through Eocene time; basins which had received Upper Cretaceous
and Paleocene deposits also received Eocene deposits (Fig. 7).
Significantly, however, basins east of the mountains became quies-
cent. The Denver, Williston, and other basins in the Great Plains
received Upper Cretaceous and Paleocene deposits, but few or no
Eocene deposits. Here, the surfaces of the earlier basins are over-
spread by thin sheets of Upper Tertiary sands and gravels. During
Eocene time the regime of the Great Plains changed from one of
sedimentation to one of erosion.
Initial Eocene deposits of the intermontane basins (Wasatch
formation and equivalents) are red-banded sands and silts of stream
origin, which pass marginally into coarse piedmont deposits. The
fluviatile deposits contain fossils of large terrestrial mammals which
probably lived in savannas and open country; forest-dwelling types,
such as those of the preceding Paleocene, are less common. Evi-
dently the passage from Paleocene to Eocene time was marked by a
restriction of forests and expansion of grasslands (Van Houten,
1948, p. 2106). Nevertheless, there is no evidence of marked change
in climate or general altitude ; the environment has been compared
with that along the present Gulf Coast of the United States (Brad-
ley, 1948, p. 641).
In some of the basins stream deposition continued through the
Eocene (as in the Powder River, Wind River, and San Juan basins),
28 P. B. KING
but in later Eocene time some of them on the west became the sites
of great lakes in which fine-grained, thin-bedded, water-laid sedi-
ments accumulated, which were in part calcareous or petroliferous
(Bradley, 1948, pp. 640-647). Lacustrine deposition had already
begun during Paleocene time in the western part of the Colorado
Plateau area, where the Flagstaff limestone was laid down widely,
but during the Eocene the center shifted eastward and a great
confluent body of water spread north and south of the Uinta Moun-
tains, in which the Green River formation was deposited ; a smaller
lake also existed in the Bighorn basin, represented by the Tatman
formation (Fig. 7).
Ranges between the basins doubtless continued to rise during
Eocene time and to shed their detritus into the basins, but the over-
lap of the Eocene strata along their edges indicates that uplift was
less active than earlier. The ranges could not have projected more
than a few thousand feet above their surroundings, else they would
have created a rain shadow to modify the prevailing humid climate.
Presence of the same species of mammals in more than one basin
indicates that the ranges were not barriers to migration.
These conclusions are incompatible with reports of Eocene glacial
tills at various places in the Rocky Mountains, especially near Ridge-
way, Colorado (Atwood and Atwood, 1938, p. 961). On this basis,
some geologists have assumed that the ranges of the Rocky Moun-
tains projected to alpine heights at the time. These far-reaching
interpretations have been built on very local, very dubious evidence,
which may well be otherwise interpreted (Van Houten, 1957).
The extensive intermontane and lacustrine deposits of Eocene
time might suggest that the Rocky Mountains and their environs
were then a region of interior drainage — that not only were the seas
driven from the region by Laramide orogeny but also, for some time
thereafter, no rivers flowed from it to the sea. A little reflection sug-
gests that this is implausible. Although the region was not lofty, its
summits must have projected to some height above the lowlands on
the east and formed a drainage divide. The probable rainfall was
greater than could have been trapped entirely by basins without
outlets. The subsiding intermontane basins caught the detritus
which was being washed down from the mountains, but during most
of the time the streams which entered them probably flowed on to
the sea. When subsidence of the basins was excessive, runoff was
EVOLUTION OF MODERN SURFACE FEATURES 29
trapped to form lakes, but the nature of their deposits indicates
that they possessed outlets through most of their existence.
It is obviously impossible to mark out the courses that were pur-
sued by the Eocene streams. Even the courses of exterior drainage
much later in Tertiary time are problematical, and the early history
of the modern rivers of the Cordillera has been diversely interpreted,
as we shall see.
Cenozoic Volcanic Activity. An additional item of the Eocene and
later Tertiary environments in the eastern part of the Cordillera
can be discussed appropriately at this point — the widespread and
persistent volcanism.
Some trace of volcanic activity can be seen in almost all parts of
the region, but with variable manifestations — in places, isolated
volcanic cones, patches of lava, and shallow intrusions; in others,
extensive volcanic piles that stand as massive plateaus or moun-
tains. Time relations also vary. Some volcanic fields are so ancient
that only deeply eroded conduits and dike swarms are preserved;
others are recent enough that the forms of the cones, calderas, and
flows are still recognizable; still others present a record of inter-
mittent volcanic activity through much of Tertiary time, and
even later.
Cause of the localization of the larger Tertiary volcanic fields is
not entirely certain. Many of the Tertiary intrusive bodies are
clearly aligned along zones of weakness in the country rock, related
to the Mesozoic orogenies; such alignments may also exist in the
conduits of the volcanic fields but have been hidden by the eruptives
that overspread the surface. It is perhaps significant that one of the
extensive volcanic fields, in the Absaroka Mountains and Yellow-
stone Park of northwestern Wyoming, lies at the east end of a
transverse zone of volcanic rocks of various ages that extends west-
ward across the Cordillera nearly to the Pacific Coast. Another
series of volcanic fields extends around the Colorado Plateau, from
the San Juan Mountains on the east through the Mogollon Plateau
and San Francisco peaks on the south to the High Plateaus of Utah
on the west, as though the plateau block were separated from its
neighbors by nearly continuous zones of weakness.
Volcanism began in the eastern part of the Cordillera during the
later stages of Laramide orogeny (Fig. 5). Large volumes of andesitic
debris occur in the Upper Cretaceous and Paleocene deposits of
30 p. B. KING
many of the basins. In Colorado, such debris in the Animas forma-
tion of the San Juan basin and the Dawson arkose of the Denver
basin indicates that the nearby San Juan Mountains and Front
Range, during the cHmax of their uplift, were heavily overspread by
eruptives, nearly all trace of which has now been eroded.
In the Absaroka Mountains and Yellowstone Park of northwestern
Wyoming, violent and explosive volcanism began in late Eocene
time, and built up the "early acid breccias" and "early basic brec-
cias" of that area (Rouse, 1937, pp. 1262-1272); no doubt their
edges once extended eastward over the older Eocene deposits of the
Bighorn and Wind River basins. Other flows and breccias were
piled over these, probably during later Tertiary epochs, and the hot
springs and geysers of Yellowstone Park attest that the volcanic
heat has not yet cooled.
Climax of the eruptions around the Colorado Plateau appears to
have been during Miocene time. In the San Juan Mountains of
southwestern Colorado where the sequence has been worked out
most completely (Larsen and Cross, 1956, pp. 258-260), the Paleo-
cene andesitic eruptions were followed by quiescence in Eocene and
Oligocene times, when relatively thin, non-volcanic deposits were
laid down. On these, during the Miocene, a mile or two of lavas,
breccias, and tuffs were piled, but with occasional pauses that per-
mitted the cutting of canyons as deep as those today. Lesser erup-
tions continued through the Pliocene and into the Pleistocene. The
volcanic record of other fields on the periphery of the Colorado
Plateau resembles that of the San Juan Mountains, although per-
haps less complete and on a smaller scale (Hunt, 1956, pp. 39-53).
Volcanism in the eastern part of the Cordillera had a significant,
though secondary role in the shaping of the geography. Eruptions
in the larger fields much increased the relief, although upbuilding
was somewhat compensated by subsidence under the load of erup-
tives and by transfer of magmas from their subsurface reservoirs to
the surface. Volcanism changed the regimen of streams by loading
them with detritus, and in places dammed and diverted their courses.
In some places these effects may be read plainly; in others, where the
eruptives have largely been removed by erosion, the effects are
difficult to assess.
Contrast between Eocene and Present Conditions. Compare the
EVOLUTION OF MODERN SURFACE FEATURES 31
conditions inferred in the eastern Cordillera in Eocene time with
conditions today — in the Eocene, low general altitude, low relief,
subdued landscape, and warm, humid climate; today, high general
altitude, high relief, rugged mountains and deep canyons, and
sharply contrasted climates. How was this change brought about?
Geologists agree on many aspects of the stor>% and especially that
the whole region has been uplifted as a unit many thousands of feet
since Eocene time, but they disagree as to the manner in which it
was accomplished, and by what stages. One view, perhaps the more
customary, is that it came about through a succession of brief up-
heavals, of which the last great one was during the Pleistocene, sep-
arated by more prolonged periods of stillstand (Atwood and Atwood,
1938, p. 978). Another view is that uplift proceeded slowly, with little
interruption since the waning of Laramide orogeny; with the up-
ward movement greatest in the first half of the Tertiary and di-
minishing afterward (Mackin, 1947, pp. 110-111). These divergent
views result from differences of interpretation of the middle and
late Tertiary deposits and land forms that are preserved in the
eastern Cordillera.
Middle and Upper Tertiary Deposits. During middle and late
Tertiary time deposits were laid down in the eastern Cordillera as
widely as during Paleocene and Eocene time, but in a different
pattern. They are preserved now as erosion remnants of original
broad sheets of sediment, rather than as downfolds in original
depositional and structural basins.
Deposits of the Oligocene White River group are extensive in the
northern Great Plains of South Dakota, and are preserved in smaller
remnants in the Central Rocky Mountains of Wyoming; they are
overlain southward, in Nebraska, by the Miocene Arikaree group.
Even more extensive in the Great Plains, however, is the Pliocene
Ogallala formation, which spreads southward from Nebraska to
Texas, and eastward from the mountain front for nearly 400 miles;
its caliche-cemented layers ("mortar beds") form the caprock of the
High Plains (Johnson, 1901, pp. 643-647). At about the same time
another sheet of deposits, the Bidahochi formation was laid down in
the south central Colorado Plateau, and is now preserv^ed as rem-
nants in northeastern Arizona (Repenning and Irwin, 1954). In
New Mexico, between the plateau and the plains, the Santa Fe
32 p. B. KING
formation of late Miocene and Pliocene age occurs in great thickness
in fault troughs that extend southward near the present course of
the Rio Grande.
These later Tertiary deposits were contemporaneous with erup-
tions in the volcanic fields of the eastern Cordillera, and near them
contain water-borne volcanic gravels and air-borne volcanic ash.
The remainder of the deposits were derived from erosion of the
rocks of the ranges. Those in the Great Plains contain fragments
derived from the Rocky Mountains on the west; those of the
Bidahochi formation, fragments from at least as far as the San Juan
Mountains on the northeast.
Except in fault troughs, the preserved deposits of middle and
upper Tertiary times are relatively thin at any locality — a thousand
feet thick or less, rather than much more than a thousand feet as
with the Paleocene and Eocene deposits. Their average texture is
considerably coarser than the latter, not only cobbly or bouldery
near the mountains, but also with lenses and layers of gravel far out
in the plains country. Nevertheless, they appear not to have resulted
from renewed folding of the region, as they overlap the edges of the
ranges without disturbance, and in places nearly bury a rough
topography of earlier rocks with complex structure.
Fossil plants and mammals in the middle and upper Tertiary
deposits record not only a spread of grasslands at the expense of
forests, an accentuation of Eocene tendencies, but also an increasing
regional altitude and aridity. By late Miocene time many of the
earlier browsing herbivore mammals had disappeared; those that
survived, such as the horses, had a dentition adapted to feeding on
harsh grasses. Indications of a semi-arid regime appear first in the
Oligocene floras and faunas and increase to a climax during late
Miocene and Pliocene time when the climate seems to have been
much like that in the present Great Plains.
The deposits themselves are compatible with this inferred environ-
ment. In the late nineteenth century it was supposed that the Great
Plains deposits had been laid down on the floors of a succession of
great lakes, hence that they were originally horizontal and later
were tilted regionally eastward. Critical study by many later geolo-
gists has made clear that they were largely of stream origin, with
local ponds at most and with finer deposits perhaps brought in by
the wind. The coarse deposits that were formed in the channels of
EVOLUTION OF MODERN SURFACE FEATURES 33
withering streams flowing eastward from tlie mountain are of such a
texture that, under semi-arid conditions, they could hardly have
moved down a slope much less than that of the present (Johnson,
1901, p. 628).
Erosion Surfaces in the Ranges. So much for middle and late
Tertiary conditions in the plains and lowlands around the mountain
ranges. What were conditions in the ranges, which were the sources of
the streams and of much of the detritus deposited roundabout?
Wide areas in the ranges are beveled by a subsummit surface,
marked by accordant crests which extend across the deformed bed-
rock structures, above which chains and clusters of peaks project on
the divides, and below which modern valleys and canyons have been
cut to depths of thousands of feet. The surface has been given local
names in different ranges, and has been variously dated as Miocene
and Pliocene. Precise age does not matter greatly, as the surface may
not have been completed simultaneously everyw^here ; it expresses a
general late Tertiary erosional condition, hence deserves the general
title of Rocky Mountain peneplain (Atwood and Atwood, 1938,
pp. 964-965).
Analysis of this surface on the north slope of the Uinta Moun-
tains, where it is unusually well preserv^ed, indicates that it has a
gradient of 400 feet per mile near the high peaks along the mountain
axis, flattening to 55 feet per mile toward the plains, where it is
largely mantled by the coarse gravels of the Bishop conglomerate
(Bradley, 1936, pp. 170-176). This outward flattening of gradient is
believed not to have resulted from late differential uplift of the
range, but to have been inherent in the nature of the surface itself.
The surface must have been cut under conditions of considerable
aridity; its graded profile, much steeper and more concave than
those of humid regions, was just sufficient in an arid climate for the
transport of materials across it.
Regional studies indicate that the Rocky Mountain peneplain in
other ranges is like that in the Uinta Mountains, and that it proba-
bly formed under similar conditions. They show, as well, that the
peneplain in the mountains was originally confluent with deposi-
tional surfaces in the Great Plains and other lowlands where, as we
have seen, the nature of the deposits suggests deposition on a slope
nearly as steep as the present slope of the plains.
Environments of Middle and Later Tertiary times. Between
34 p. B. KING
Eocene and middle Tertiary times the eastern Cordillera was proba-
bly arched upward as a unit by as much as 5,000 feet. During the
same period, the climate became more arid, partly because of a
world-wide secular change (Axel rod, 1957, pp. 40-41), partly because
the crest of the uplift created a rain shadow over the area to the east.
Climax of uplift and aridity was probably also the climax of
aggradation in the areas between and east of the mountains. It ap-
pears well established (Atwood and Atwood, 1938, pp. 965-968;
Mackin, 1937, pp. 821-823) that extensive areas not now covered by
later Tertiary deposits, including the earlier Tertiary intermontane
basins and the lower mountain ends and spurs, were then buried.
Most of the emergent areas were planed to form the Rocky Moun-
tain peneplain, leaving, as projections above the general level, only
the unreduced peaks along the axes of the ranges.
Opinions differ as to the relief of the aggraded and planed-off
surface of later Tertiary time. The view of many geologists has been
that regional relief of the eastern Cordillera was considerably less
than that of today, and that modern regional and local relief is the
product of renewed uplift during the Pleistocene. Other geologists
call attention to the fact that preserved gradients of the Great
Plains deposits and of the Rocky Mountain peneplain are about
those to which stream regimen would have been adjusted in an arid
climate and, by extrapolation, infer that the late Tertiary graded
surface had almost the same regional relief as that of the present
country. Regional relief had thus increased greatly from that of
early Tertiary time, but local relief was about as subdued, and
differed much from the present strong local relief.
Quaternary Denudation and Dissection. Transformation of the
late Tertiary landscape into that of the present was thus an event
of the Quaternary period, mainly of the Pleistocene epoch. Regard-
less of ultimate causes, it resulted from accelerated stream erosion,
which degraded and dissected the whole region.
Such erosion removed large volumes of upper Tertiary deposits
from the mountain areas, and excavated the rocks beneath by vary-
ing amounts according to their resistance. The basins, formed of
weak Cretaceous and lower Tertiary rocks, were etched out, so that
the ranges of pre-Cambrian crystalline rocks and Paleozoic stratified
rocks projected above them. During the period of aggradation
streams had wandered at will down the slopes of the subdued sur-
EVOLUTION OF MODERN SURFACE FEATURES 35
faces, but many of them, as they cut downward, were superimposed
on hard rocks in the buried mountain ridges beneath, and were
there forced to excavate deep canyons (Atwood and Atwood, 1938,
pp. 968-976).
The same sort of canyon cutting took place in the less deformed
rocks of the Colorado Plateau, southwest of the Rocky Mountains,
where uplift and degradation had been in progress since early in
Miocene time (Hunt, 1956, p. 77).
Principal cause of the accelerated stream erosion of the eastern
part of the Cordillera during Quaternary time must have been re-
newed regional uplift, but there is uncertainty as to its amount. All
graded surfaces of subaerial erosion and deposition possess an orig-
inal slope toward the sea ; if the late Tertiary surfaces were produced
in an arid or semi-arid regime, this original slope would have been
much steeper than that produced in a more humid regime. How
much the slopes of the late Tertiary surfaces and the regional relief
of the eastern Cordillera were augmented by uplift is thus difficult
to evaluate, but it was probably much less than has been supposed
by some authors.
Whatever the magnitude of the uplift, major climatic changes oc-
curred also, as the ice ages of Pleistocene time brought about both
refrigeration and increase of rainfall. Under this more humid regime,
streams that had become adjusted to steep gradients during the
arid times of the later Tertiary were able to readjust themselves to
new, lower gradients. Such readjustments were most marked, of
course, during the glacial periods, and were less marked during the
drier interglacial periods; thus, general downcutting has been punc-
tuated by many pauses expressed in the landscape by a succession
of terraces and intervening steps.
Origin of Drainage Courses of Eastern Cordillera. All this is very
well as a generalization but what, specifically, has been the history
of the individual rivers of the eastern Cordillera? The more specific
we become, the more the doubts and confusions multiply.
Streams draining eastward from the Cordillera into the interior
region need trouble us least. Streams of some sort no doubt flowed
from the Cordillera in this direction since the Laramide orogeny,
although their courses must have shifted with time. The greatest
shift in later times was a deflection of streams that formerly flowed
into Hudson Bay, southward, around the edges of the Pleistocene
36 P- B. KING
continental glaciers, to form the Missouri River (Howard, 1958,
pp. 585-587).
Greater problems attend the streams that flow southward and
southwestward from the Rocky Mountains and find their way
through long reaches of mountain, plateau, and desert country,
especially the Rio Grande and the Colorado rivers.
The Rio Grande flows southward from its source in the Rocky
Mountains for 500 miles through a succession of desert basins before
it breaks through the eastern ridges of the Cordillera in the Big
Bend country of Texas and enters the slope toward the Gulf Coast.
Deposits in the basins of northern New Mexico contain channels of
foreign stream-worn gravels that indicate existence there since early
Pliocene time of a river or rivers ancestral to the Rio Grande (Bryan,
1938, pp. 205-208), but such gravels are unreported in basin deposits
of southern New Mexico and Texas. Perhaps the Rio Grande drained
at first into the lake region of northwestern Chihuahua (Lee, 1907,
p. 22) , and later found its way across the ridges to the east by filling
a succession of basins, until it overflowed each in turn at the lowest
point on its rim (King, 1935, p. 260).
Very likely the Colorado has drained southwestward from the
Rocky Mountains for a long span of Tertiary time, during which it
may have persisted in its present position across much of the north-
eastern half of the plateau. Its lower course across the plateau is
more puzzling. It has there cut the Grand Canyon through the south
end of the Kaibab Plateau, which is one of the highest uplifts of the
region. Moreover, below the lower end of the canyon, the desert
basins traversed by the river are filled by the late Tertiary Muddy
Creek formation, which is made up of locally derived detritus,
without deposits of any large, through-going river (Longwell, 1946,
pp. 821-826); the river could not have entered these basins until
after Muddy Creek time.
It has been suggested that the river coursed across such uplifts as
that of the Kaibab Plateau when they were in an early state of
growth, that renewed uplift ponded the drainage on their upstream
sides, until the river overflowed through its original valley and cut
this to its present depth (Hunt, 1956, pp. 65-67). Such a sequence of
events is possible, but field relations suggest otherwise; so far as
known the Kaibab uplift was folded entirely by Laramide orogeny.
It has also been suggested that the Colorado River formerly flowed
EVOLUTION OF MODERN SURFACE FEATURES 37
southward through the area of the Bidahochi formation, and so to
the sea, but was later diverted westward by upHft of the southern
rim of the plateau (Repenning^/a/.). It is believed that filling of the
area upstream from the Kaibab Plateau to a depth of about 600 feet
would be sufficient to allow the river to drain westward, utilizing
the smaller consequent and subsequent stream valleys that had al-
ready been established between the Kaibab Plateau and the Grand
Wash Cliffs.
Nevertheless, the problem of the course of the Colorado River in
its lower segment across the Colorado Plateau remains one of the
riddles of the Cordillera, and will no doubt be debated for years to
come.
Central Part of Cordillera (Great Basin and Sierra Nevada)
Basin and Range Topography and Structure. During the post-
orogenic phase, the Great Basin, or region between the Colorado
Plateau and Sierra Nevada, acquired its distinctive Basin and Range
topography — a succession of discontinuous, subparallel ranges, sep-
arated by desert basins.
The Great Basin itself is a region of interior drainage; streams
that flow into its basins have no outlet to the sea. This is in part a
product of the structure, for some of the basins, of which Death
Valley is an extreme example, have been depressed lower than any
possible outlet. To some extent the interior drainage of the Great
Basin is a product of its arid climate and its remoteness from the
sea; part of its streams could flow out of the region if they had
sufficient volume (Hubbs and Miller, 1948, pp. 94-98), Basin and
Range topography extends far south and southeast from the Great
Basin into Arizona, New Mexico, and Sonora, which are nearer the
sea and are drained by the Colorado, Gila, Rio Grande, and other
through-flowing rivers.
Some geologists have thought that the distinctive quality of Basin
and Range topography is primarily a product of erosion of a com-
plexly deformed bedrock under arid conditions; clearly, the arid
regime has done much to shape the details of the landscape. Most
geologists believe, however, that the topography of much of the
province is related to a distinctive Basin and Range structure, which
was superimposed on the earlier orogenic structures, in part so
recently that the forms of basins and ranges are a direct result of
38
p. B. KING
crustal movement. Certain it is that much of the region is still
unstable, as attested by many fresh fault scarps along the edges of
the mountains and in adjacent alluvial deposits, some of which can
be related directly to recorded earthquakes.
Basin and Range structure is thought to be a mosaic of blocks,
which have been variously raised, lowered, or tilted along steeply
dipping faults (Fig. 8). High-standing blocks produced the mountain
ranges, low-standing blocks the basins; detritus eroded from the
higher blocks was trapped in the lower ones, and smoothed their
surfaces into gently sloping plains. The faulted sides of the most
recently upraised mountain blocks still preserve straight base lines
10 Miles
_i
Approximate scs/e
Fig. 8. Generalized section showing Basin and Range structure as
commonly interpreted, based on Humboldt Range, western Nevada.
(After Louderback, 1904.) 1, Deformed bedrock of Paleozoic and
Mesozoic age. 2, Lava and tuff, mainly of early and middle Tertiary age.
3, Deposits of the intermontane basins, mainly of late Tertiary and
Quaternary age.
and steep escarpments; mountain blocks upraised earlier are more
frayed and are embayed by erosion (Davis, 1925). Detrital filling in
the basins has generally overlapped the edges of the mountains
sufficiently to conceal the faults along their borders, but these faults
are exposed at some favorable places.
Basin and Range structure is a post-orogenic feature that suc-
ceeded the strongly compressed structures of the Cordilleran
orogenic phase, but opinions differ as to the forces that caused it
(Nolan, 1943, pp. 184-186). An early view is somewhat naive — that
it was produced by a breakdown and collapse of the region under
tension, after relaxation of orogenic compression. But under perva-
sive tension the whole region would have subsided from an earlier
high-standing position, the ranges less than the basins, whereas the
EVOLUTION OF MODERN SURFACE FEATURES 39
region has been uplifted several thousand feet since the early
Tertiary, and at least some of the ranges have undergone actual,
rather than merely relative, uplift. Structures resulting from crustal
tension are no doubt present in the region, but they may have
resulted from components of a more pervasive crustal compression.
This compression, however, manifested itself in a different guise
from that which deformed the eugeosynclinal and miogeosynclinal
rocks at an earlier period.
Time Relations of Basin and Range Structure. In the generalized
picture sketched above. Basin and Range topography and structure
were presented as an accomplished fact, although their development
through time was hinted by the varying degrees of erosion observed
in different ranges. But the present topography and structure were
long in the making, and when one attempts to trace their develop-
ment through time, the picture at once becomes more complex
(Longwell, 1950, p. 427).
For example, it was stated that the low-standing blocks, or desert
basins, were largely filled by detritus eroded from the adjoining
ranges, but these deposits formed during a considerable span of
Tertiary time, in which the geography changed as a result of con-
tinuing crustal movements. Earlier basin deposits were derived
from ranges in a state of growth different from the present ranges
and perhaps even in different positions; in places the deposits were
spread over the sites of ranges that developed later. With further
movements, the earlier deposits were faulted, tilted, and eroded, and
those in which resistant lavas were embedded were raised in places
to mountainous heights. Later Tertiary and Quaternary deposits
bear a closer relation to modern geography, although even these are
more or less deformed and eroded.
Sierra Nevada Topography and Structure. The Sierra Nevada,
which lies west of the Great Basin, is a single massive block 400
miles long and 80 miles wide, whose crest attains alpine heights, yet
its form and structure differ only in degree from the mountain
blocks of the Basin and Range province, and its development was
closely related to at least the Great Basin segment of that province.
The Sierra Nevada block may have been shaped by the great masses
of granitic rocks embedded in its deformed eugeosynclinal strata, as
these extend along its eastern side for most of its length.
The Sierra Nevada faces the Great Basin on the east in a series of
40 P. B. KING
lofty scarps that have been outlined mostly by faults, although the
faults are not continuous and are offset en echelon in many places.
Minor faults also occur within the range, but most of the range, west
of its summit, is a tilted block with remarkably even, westward-
tloping crest lines, below which the tributaries of the Sacramento
and San Joaquin rivers have cut impressive canyons.
Early Tertiary (Paleocene and Eocene) Environments. By early
Tertiary time, the topography that developed on the orogenically
deformed miogeosynclinal and eugeosynclinal rocks had become
decadent, but the post-orogenic topography of basins and ranges
had not yet developed.
At many places in the eastern half of the Great Basin the Mesozoic
and older rocks are overlaid by patches of calcareous mudstone, fine-
grained sandstone, and coarser sands and gravels. These appear to be
remnants of originally much more extensive deposits that formed in
floodplains, swamps, and lakes, probably in a warm, humid lowland
(Van Houten, 1956, p. 2819). Although the deposits have been dated
only by meager fossil evidence, they are probably westward exten-
sions of the Paleocene and Eocene deposits of the Colorado Plateau
and the central and southern Rocky Mountains, which formed in a
similar environment.
The western half of the Great Basin seems to have been part of a
low highland which extended westward across the area of deformed
eugeosynclinal rocks to the western edge of the Sierra Nevada. Few
or no early Tertiary sedimentary units exist in the western Great
Basin, although the lower parts of some of its volcanic sequences
may be as old as Eocene. At the western edge of the highland the
marine lone formation of middle to late Eocene age overlaps widely
on the deformed Mesozoic rocks (Allen, 1929). It is composed of
clays of remarkable purity, with interbedded sands, and is traceable
up the slope into the older gold-bearing stream gravels of the Sierra
Nevada foothills. During lone time the site of the Sierra must have
been worn down to low relief, and was drained by sluggish streams
that headed well east of the present mountain crest. The clays were
derived from deeply decayed granitic rocks that were widely ex-
posed on this worn-down surface.
Middle Tertiary {Oligocene and Early Miocene) Environments. In
Oligocene and early Miocene time lavas, agglomerates, and tuffs of
varied composition were spread widely over the western part of the
EVOLUTION OF iMODERX SURFACE FEATURES 41
Great Basin area, and form the older volcanic sequence of that area,
now much disturbed and mineralized. The northwestern corner of
the Great Basin was overlapped by basalt flows related to the
Miocene Columbia River basalt. Most of the volcanics farther south-
east have also been ascribed to the Miocene, but a tuff member in
the Alta formation of the Virginia City district contains middle
Oligocene plants. At some places in the eastern and southern parts
of the Great Basin, ash-rich sand, mud, and gravel were deposited
in basins that recently had been outlined by faulting.
Available floras indicate that the western part of the Great
Basin stood at an altitude of about 2,000 feet above sea level in
middle Tertiary time, with the Sierra Nevada to the west projecting,
at most, only a thousand feet higher. Apparently neither the low
Sierra Nevada ridge nor the downfaulting of incipient basins inter-
fered materially with drainage westward to the Pacific.
During one or more episodes before late Miocene time, and per-
haps mainly in the middle Miocene, the older Tertiary volcanic and
sedimentaiy rocks in many parts of the Great Basin were faulted
and tilted, then widely eroded (Van Houten, 1956, p. 2820). These
movements, premonitions of which we have seen in the middle
Tertiary basin deposits, are the first notable disturbance of the
region since the orogenic phase, and mark the beginning of develop-
ment of Basin and Range structure and topography.
Late Tertiary {Late Miocene and Pliocene) Environments. During
late Miocene and early Pliocene time volcanics and sediments were
spread widely over the Great Basin and Sierra Nevada, covering an
eroded terrain that had been more or less deformed by the preceding
disturbances. As these deposits contain mammals and plants at
many places, and occasional invertebrates and other fossils, they
form not only a useful stratigraphic datum, but also an index of the
environments of the time (Van Houten, 1956, p. 2802; Axelrod,
1957, pp. 23-28).
Much of the central and northern parts of the Sierra Nevada were
covered by several thousand feet of andesitic lava flows, remnants of
which are still preserved on stream divides and mountain tops.
Principal centers of eruption were near the modern crest of the
mountains, along an axis which continued northward into the
Cascade Range, but the flows also spread eastward into the Great
Basin. Andesitic debris was transported widely westward and
42 p. B. KING
eastward, where it became an Important component of contem-
poraneous sedimentary deposits.
Over much of the Great Basin east of the eruptive area a succes-
sion of andesitic vitric tuff, reworked ash, bentonitic mudstone,
sandstone, Hmestone, and diatomite was deposited, which has been
variously termed the Truckee, Esmeralda, or Humboldt formation,
depending on locality. The deposits were laid down in many sep-
arate but probably confluent basins, partly in lakes and swamps.
They not only covered the earlier Tertiary rocks but overlapped
widely onto low inter\^ening highlands of the Mesozoic and Paleozoic
rocks. In southern Nevada faulting was more active at the time, and
the Muddy Creek formation of that area consists of coarse alluvial
fan deposits along the faulted basin margins, and of finer-grained
elastics and evaporites in the basin centers.
Comparison of floras in a traverse eastward across the area is
instructive as to the late Miocene and early Pliocene environments
(Axelrod, 1957, pp. 34-38). Conifer forests like those of the modern
Sierra Nevada were not well developed on its western slope probably
because of low altitude and warm climate. At Carson Pass on the
crest of the range, at a modern altitude of more than 9,000 feet, is a
flora of deciduous trees which could not have lived at altitudes
higher than 2,500 feet. Farther Inland, In the Great Basin, were
conifer forests of a type now found at the margins of woodland and
chaparral country. Annual rainfall at the western base of the Sierra
Nevada must have been about 25 or 30 inches, increasing to 40 or
45 inches on the upper slopes, and thence decreasing to 25 inches
over the lowlands of the Great Basin. The summit level of the central
and northern Sierra Nevada must have stood at an altitude of less
than 3,000 feet, and projected about 1,000 feet above the Great
Basin to the east ; it created no more than an ineff^ective rain shadow
over that area. Evidence of fossil fishes suggests that the Great Basin
at this time stood at altitudes well below 2,000 feet, to allow the
ingress of lowland coastal faunas (C. L. Hubbs, personal com-
munication).
The andesitic eruptions along the Sierra crest, although spread
over a surface of low altitude and low relief, foreshadowed later
uplifts along that axis. By late Pliocene time the floras of the Great
Basin changed from a woodland and forest fades to a savanna and
grassland fades, adapted to less than 15 inches of rainfall. Evidently
EVOLUTION OF MODERN SURFACE FEATURES 43
the Sierra Nevada block was now being uplifted, and was exerting a
climatic influence on the region to the east. Uplift continued into
early Pleistocene time, until the block had been raised 5,000 to
6,000 feet in the north and 7,500 to 9,000 feet farther south (Axel-
rod, 1957, p. 42).
At the same time as the Sierra Nevada was being raised, block
faulting on an extensive scale disrupted the Great Basin, and was
largely responsible for shaping it into its present Basin and Range
topography (Van Houten, 1956, pp. 2821-2822). There was also a
gradual increase in altitude; basin floors which had stood at well
below 2,000 feet above sea level at the beginning of the Pliocene,
now stand at 3,000 to 5,000 feet. In part this was a result of sedi-
mentary filling of the basins, but to a much greater extent to
regional upwarp.
The reader may note a discrepancy between the record as here set
forth for times of uplift in the Rocky Mountain region on the east
and the Great Basin and Sierra Nevada on the west. In the Rocky
Mountains, some geologists believe that the principal uplift was
before the middle of the Tertiary and diminished later, whereas the
Great Basin and Sierra Nevada seem to have been low up to middle
Tertiary time, and were greatly uplifted afterward. The inferred
history of the two areas is based on interpretations of necessarily
elusive evidence by various competent observers, but if the contrasts
are real, they had a significant influence on the geographic and cli-
matic evolution of the middle Cordillera.
Pleistocene Environments. Events in the Great Basin and Sierra
Nevada during the Pleistocene are perhaps sufficiently familiar as
not to require detailed recital — the ice fields along the Sierra crest
and the valley glaciers below them, the smaller glaciers on higher
summits in the Great Basin, and the great lakes, such as Bonneville
and Lahontan, which flooded the lower country, in places to depths
of more than a thousand feet. Climatic fluctuations are recorded not
only by successive glacial moraines in the mountains, but by several
epochs of filling and dessication of the lakes. Existence of the lakes
indicates a much increased rainfall and implies, as well, that many
of the basins temporarily possessed exterior drainage (Hubbs and
Miller, 1948, pp. 21-29).
The Great Basin has returned now to conditions of aridity ap-
proximately comparable to those at the end of Pliocene time but if.
44 p. B. KING
as many believe, the present is merely an interglacial rather than a
post-glacial period, far-reaching climatic fluctuations in the region
may be anticipated in the future.
Northwestern Volcanic Province (Columbia Plateaus and Cascade
Range)
General Setting. The northwestern part of the United States
exhibits one of the most drastic later modifications of the orogenic
structure and topography in the Cordilleran region. Elsewhere in the
Cordillera, volcanism interrupted or modified other post-orogenic
processes; here it dominated the scene. The deformed geosynclinal
rocks are covered, in places deeply, by great floods and piles of lava,
and by associated breccias, tuffs, and sediments. In northern Oregon
and southern Washington no rocks older than these are exposed for
300 miles parallel with the coast, or 400 miles inland ; they also ex-
tend over an even greater area to the south and southeast where
older rocks emerge in places (Fig. 9). The volcanic regime was
prolonged and extended, at one place or another, through most of
Tertiary and Quaternary times.
The Nevadan belt of deformed eugeosynclinal strata frames the
region on the south, east, and north. It is exposed at intervals be-
tween the Klamath Mountains of southern Oregon and the Cascade
Range of northern Washington, but describes a great arc eastward,
which passes through the highlands of northeastern Oregon and
western Idaho (Fig. 9) . The volcanics are confined by the arc on the
north and east, but break across it on the southeast, where they
extend into southeastern Oregon and southern Idaho.
This extraordinary localization of volcanic activity provides food
for speculation for which there is no certain answer, especially as the
substructure upon which the volcanics were built is widely buried —
and entirely so within the area enclosed by the Nevadan arc. A
question is worth asking, however, whether the area within the arc
might not have been an oceanic embayment, floored by simatic
crust, until well through the geosynclinal phase (Figs. 2 and 3), and
was only added to the continent later, by volcanism and sedimenta-
tion. This possibility is suggested by dominance of basalts within the
arc, which were seemingly derived without contamination from the
underlying simatic layer, and by more varied lavas southeast of the
arc, where there was evidently greater mixing of simatic and sialic
crustal materials.
EVOLUTION OF MODERN SURFACE FEATURES
45
\\ it \\
X Sierra
i^°% ^ \
1
^1
^
^
>*■>■■ 'I I. .
2 ^.v.-;.' 3 |..
> - » ■■ '
• •
.100
400 Miles
J
Fig. 9. Map of northwestern volcanic province, in Washington, Ore-
gon, Idaho, and adjacent states. 1, Nevadan basement; metamorphic
rocks Hned, plutonic rocks in heavy shading. 2, Inferred margins of
Nevadan orogenic belt. 3, Plateau basalts of Miocene and later age. 4,
Andesitic volcanics of Cascade Range. 5, Volcanic cones of Cascade
Range, mainly of Quaternary age. 6, Other rocks; mainly sedimentary
rocks of Mesozoic and Tertiary age, but including some older Tertiary
volcanics. 7, Edge of continental area.
The volcanic rocks and their associates assume diverse geographic
forms: along the Pacific, the low Coast Ranges; east of a longi-
tudinal depression, the high Cascade Range; and farther inland, the
46 p. B. KING
Columbia Plateaus, partly split in their middle by the emerged
Nevadan rocks in the highlands of northeastern Oregon.
Early Tertiary Environments. The record of early Tertiary time
may be seen mainly in the Coast Ranges, where marine clastic
sedimentary strata several miles thick are turned up in gentle folds.
Some of them, such as those of the Olympic Mountains of north-
western Washington, may have been laid down beneath ocean water
of considerable depth, and have been derived from turbid flows that
moved westward down the continental slope. Interbedded with the
Tertiary sedimentary rocks are great lenticular masses of basaltic
lava, which were largely erupted beneath the sea, as shown by their
pillow structure (Waters, 1955a, pp. 204-707). Inland, where the
lower Tertiary rocks are occasionally exposed , the marine beds pass
into land-laid deposits, including beds of coal, which formed in
floodplains, swamps, and lakes.
During early Tertiary time the northwestern volcanic province
probably was a broad coastal plain with an offshore continental shelf
and slope, which faced westward on open ocean (Fig. 5). Its environ-
ment must have resembled that of the present Gulf Coastal Plain,
except for the much greater volcanic activity. No ranges existed
near the coast to create a climatic barrier like that today; Eocene
floras from both the east and west sides of the present Cascade Range
are closely related, and grew in subtropical lowland forests (Chaney,
1938, p. 3^Z).
Middle and Late Tertiary Environments. Miocene time witnessed
the great eruptions of Columbia River basalt, which spread over an
area of 100,000 square miles, in places to thicknesses of a mile or
more (Waters, 1955a, pp. 707-708). The basalt flows cover all the
plateau country of southeastern Washington and northeastern
Oregon, within the Nevadan arc (Fig. 9), where in many places they
still remain nearly horizontal, although in others they have been
warped and folded. Along the lower course of the Columbia River
the basalt also spreads westward across the site of the Cascade
Range. Here its farther edges interfinger with marine deposits.
The Columbia River basalt is a plateau basalt — it was not erupted
from volcanoes, but welled out of deep fissures from the simatic layer
beneath. Single flows are 100 to 500 feet thick, and must have been
very fluid as some of them are traceable for more than a hundred
miles. The flows were probably piled thickest near the center of the
EVOLUTION OF MODERN SURFACE FEATURES 47
eruptive area, which subsided gradually beneath them, and they
spread thence in all directions. Along their edges to the north, east,
and south, they overlapped an eroded surface of the Nevadan
orogenic belt, damming valleys and ponding their waters.
At about the same time, a different form of volcanism was be-
ginning along the Cascade Range. Eruptions of explosive violence
built up piles of andesitic lava, mudflows, breccias, and tuffs, which
were probably surmounted by volcanoes. These accumulations
formed a chain approximately along the axis of the present range,
from northern Washington southward through Oregon into Cali-
fornia, where it joined the chain of andesitic eruptions in the Sierra
Nevada. The andesitic volcanics had a much more complex origin
than the basaltic, and probably formed on a line of weakness that
was developing along the Cascade-Sierra Nevada trend (Waters,
1955a, pp. 709-710).
In both the Cascade Range and Sierra Nevada, this line of weak-
ness was first manifested at the surface by eruptions only, but later
the rocks along it began to be raised by crustal forces. Unlike the
segment in the Sierra Nevada, however, that in the Cascades was
neither tilted as a block nor greatly faulted ; the faults that occur are
minor and local. Moreover, volcanic upbuilding went on hand in
hand with crustal uplifts so that basement rocks were not laid bare
by erosion, except at the north end. The cross section of the range
exposed in the gorge of the Columbia River exhibits both volcanic
upbuilding and complex arching (Hodge, 1938, pp. 839-886).
Quaternary Events in Cascade Range. The modern Cascade Range,
from northern Washington to northern California, is crowned by a
score or more of great volcanic cones (Fig. 9), whose construction
apparently began as early as the Pliocene, but whose growth con-
tinued until recent times — if, in fact, it has yet ceased. The cones
were built upon a deeply eroded surface of the older andesitic vol-
canic rocks that form the greater bulk of the range, apparently after
a time of quiescence of some duration in late Tertiary or early
Quaternary time. North of the Columbia River the cones stand
singly, but farther south they have built up a massive range of
volcanic rocks on the eastern side of the earlier range.
History of Columbia River. The Columbia River, whose sources
are in the Rocky Mountains on the east, enters the Pacific in the
midst of the volcanic province. Much of its drainage basin is blessed
48 p. B. KING
with greater rainfall than the country farther south, and its volume
far exceeds that of any other stream on the western slope of the
Cordillera. Similar greater rainfall probably prevailed in this north-
ern segment of the Cordillera through much of the post-orogenic
phase, so one may assume that an ancestor of the Columbia existed
there throughout much of the Tertiary and Quaternary.
With onset of the eruptions of Columbia River basalt, the course
of the river in the coastal plain downstream from the highlands of
the Nevadan orogenic belt was obliterated by the flood of lava. Parts
of the river and its tributaries in the highlands to the north and
northeast were dammed by the lava, and a series of lakes were
formed. Each lake drained around the spur ends of the highlands of
older rocks to the next lower lake on the west, thus establishing an
exit for the waters along the edge of the volcanic field ; with down-
cutting, there was thus established the new course of the Columbia,
part of which it still follows (Fig. 9). Farther downstream in south-
ern Washington, however, the river is deflected eastward into the
lava country, probably as a result of outbuilding of andesitic debris
from the Cascade Range on the west (Waters, 1955b, pp. 681-683).
In southern Washington the river also crosses several anticlinal
folds in the basalt, which plunge southeast from the Cascade Range.
Each anticlinal fold is expressed topographically as a ridge, and in
each ridge the river and several of its tributaries have cut deep
gorges. The Columbia and its tributaries were probably antecedent
to the anticlines (Waters, 1955b, pp. 679-681) — they had much their
present courses before the folding and maintained them by down-
cutting as the anticlines were raised. Still farther downstream the
river cuts a much larger gorge through the complexly upbuilt and
upwarped Cascade Range. Many geologists believe that the river is
antecedent to the growth of the Cascade Range also, but some
would ascribe its course through the mountains to a complex process
of superposition (Hodge, 1938, pp. 888-918).
Pacific Border of Cordillera (Coast Ranges of California)
General Geography and Geology. From the Klamath Mountains
southward through California and into Baja California, the western-
most ranges of the Cordillera are the Coast Ranges along the Pa-
cific Ocean (Fig. 10). Southward to Point Conception they consist of
numerous parallel ridges, each diverging south-southeastward from
EVOLUTION* OF MODERN SURFACE FEATURES
49
^
£'/>
J^
^
400 Miles
Fig. 10. Map of California, showing the two types of basement in the
Coast Ranges and adjacent areas. 1, Nevadan basement of metamorphic
and plutonic rocks. 2, Franciscan basement of strongly deformed but
little metamorphosed clastic sedimentary rocks; probable extent of
Franciscan basement beneath cover of younger sediments indicated by
light stipple. 3, Areas covered by younger sedimentary and volcanic
rocks. 4, Faults, many of which have large components of lateral dis-
placement. 5, Edge of continental area.
50 p. B. KING
the coast at a slight angle. At Point Conception, however, the
prominent Transverse Ranges run nearly eastward, facing the
Channel Islands offshore in the longitude of Santa Barbara, and
rimming the north side of the Los Angeles lowland farther east.
South of the Transverse Ranges and the Los Angeles lowland the
Peninsular Ranges resume a trend parallel with the coast, and form a
more massive set of blocks, somewhat like the Sierra Nevada.
Dominant surface rocks of the Coast Ranges are mainly of
Tertiary age, primarily fine- to coarse-grained clastic sedimentary
strata, but with much diatomite and some volcanics. All of them,
even the youngest, are folded and faulted, in part heavily so, indi-
cating that the latest phase of the construction of the ranges was
late in geologic time.
Basement Rocks. We have suggested earlier that at least the
northern part of the Coast Ranges, west of the Sacramento Valley,
was a marine realm through Jurassic and much of Cretaceous times
— continental shelf, continental slope, and ocean deep — which re-
ceived great masses of sediments washed off the Nevadan orogenic
belt. The Coast Ranges might thus be an element which was built
up and added to the continental plate from Mesozoic time onward.
A puzzling feature, incompatible with this concept, is the oc-
currence in parts of the Coast Ranges of a crystalline basement
consisting of granitic rocks, shown by radiometric determinations to
be of mid-Mesozoic age like those in the Nevadan orogenic belt, and
their host rocks of earlier schists, slates, and marbles. In one area,
the San Gabriel A'lountains north of Los Angeles, radiometric
determinations prove the existence of rocks as early as pre-Cam-
brian, but these probably do not emerge elsewhere.
Disregarding the cover of Tertiary rocks, the fundamental frame-
work of the Coast Ranges is an alternation of these areas of crystal-
line Nevadan basement with a basement of much deformed but
little metamorphosed Mesozoic rocks, especially the Franciscan
group which may have been formed on the western, or oceanic side
of the Nevadan belt.
Basement of Franciscan age underlies all the Coast Ranges north
of San Francisco Bay and extends thence southward along the west
side of the San Joaquin Valley (Fig. 10). Southwest of this northern
Franciscan area is a long strip of Nevadan basement, termed Salinia,
which extends southward from Point Reyes and the Farallon Is-
EVOLUTION OF MODERN SURFACE FEATURES 51
lands near San Francisco, along Salinas Valley (for which it is
named) to the Transverse Ranges. Another area of Franciscan base-
ment, the central Franciscan area, lies west of Salinia (Reed and
Hollister, 1936, pp. 1547-1550). The Transverse Ranges again are
largely floored by Nevadan basement, as are the Peninsular Ranges,
but another, the southern, Franciscan area lies to the south and
west, mostly beneath the sea, and continues far southward along the
Pacific side of Baja California.
The Nevadan basement has been supposed to be the foundation
of the Coast Ranges and to underlie the Franciscan rocks; remark-
ably enough, however, the base of the Franciscan has never been
discovered, and all its contacts with the Nevadan rocks are high-
angle, through-going faults. For example, the contact between the
Nevadan mass of Salinia and the Franciscan rocks on the northeast
is the San Andreas and associated faults. There is thus no evidence
of the sort of crustal material on which the Franciscan rocks were
laid ; it might have been quite different from the Nevadan basement.
San Andreas and Other Through-Going Faults. The high-angle,
through-going faults thus seem to be a critical feature of Coast
Range structure, and many of these faults are remarkable enough of
themselves. Instead of their sides merely moving upward or down-
ward, one side shifted laterally past the other, and the faults have a
large component of sideward movement. For example, along the San
Andreas fault, which has been traced the farthest of any, stream
courses and stream valleys are offset — a stream draining northeast
across the fault turns along the fault line, then resumes its north-
eastward course a half a mile or so to the southeast. This faulting
has thus altered the geography and surface forms, not merely by
raising and lowering blocks of the crust, but by shifting the geo-
graphic positions of large sections of the country relative to country
on opposite sides; the saying is apt that "San Francisco and Los
Angeles are coming closer together," the one city being northeast of
and the other southwest of the fault.
Offset of stream valleys is an obvious late feature, but study of
the rocks on the two sides of such faults discloses older and much
greater anomalies. Gravels in Tertiary rocks on one side of a fault
may contain material whose only possible source is in some area
many miles away on the opposite side, suggesting that the source
area has moved away from the gravels in the time since they were
52
p. B. KING
deposited. Such stratigraphic evidence indicates a sideward shift on
the San Andreas and some of the other faults of 30 miles or more
since the mid-Tertiary (Crowell, 1952, pp. 2030-2035; Noble, 1954,
pp. 44-47). Even greater shifts are suggested when comparisons are
made between basement rocks on the opposite sides, but they are as
yet difficult to prove and require further detailed research (Fig. 11).
There is thus a suggestion that the San Andreas fault has been
moving progressively for a long period — at least since the close of the
500 Miles
Fig. 11. Maps of California during successive periods to illustrate an
hypothesis of extensive lateral displacement on the San Andreas and
related faults. A, In late Mesozoic time. B, In late Miocene time. C,
Present time. (Modified from M. L. Hill, 1954.) 1, Boundary between
Nevadan basement (to east) and Franciscan basement (to west). 2,
Boundary between Miocene continental sediments (to east) and marine
sediments (to west).
Nevadan orogeny — so that rocks of each older age have been shifted
by greater amounts (Hill and Dibblee, 1953, pp. 445-451). This
picture, if valid, is greatly complicated by the fact that the San
Andreas, or master fault, is only one of many in the same region
with similar habit; attempts at reconstruction of the geography at
successive periods thus involve, not a single break, but many breaks
with diverse movements.
Be that as it may, the possibility has thus suggested itself that
the anomalous strips of Nevadan basement are slivers that were
faulted off the orogenic belt on the east, and have been transported
scores or hundreds of miles northwestward, into an environment
foreign to them (Fig. 11). Such movements are strongly indicated in
EVOLUTION OF xMODERN SURFACE FEATURES 53
southern California, where shifts of as much as 30 miles on the San
Andreas fault since the mid-Tertiary have been proved, and where
even greater shifts are suggested in the carher rocks. Farther north,
however, total movements of less than a mile on the San Andreas
fault have been claimed (Taliaferro, 1943, pp. 159-161). Such claims
seem to be based merely on the latest of a series of breaks, and fail
to consider total offset in a broader San Andreas /aw// zone (Wallace,
1949, p. 803). Nevertheless, it is puzzling in this northern area that
there is so little offset of the coast where the San Andreas fault goes
out to sea south of San Francisco, and no detectable offset of the
edge of the continental shelf farther offshore to the northwest. An
offset of the continental shelf of more than 50 miles occurs west of
Cape Mendocino, but along an east-west fracture system, aligned
differently from the San i\ndreas trend (Menard and Dietz, 1952,
p. 273) (Fig. 10).
Although we now appear to have acquired the rudiments of an
explanation for the anomalies of the Coast Ranges, this explanation
is still obscured by negations and contrary evidence. At this stage,
almost any explanation for a set of anomalies in the Coast Ranges
creates other, unexplainable anomalies.
Tertiary Environments. Regardless of the anomalies in the base-
ment rocks and the possible shifts of large segments of the area along
through-going faults, the different types of basement have exerted a
profound influence on the structures of the Tertiary rocks. Areas
underlaid by Nevadan and Franciscan basement have been land or
sea at different times and, when compressive forces were exerted,
the areas underlaid by the weaker Franciscan basement have been
much more deformed than those underlaid by the stronger Nevadan
basement.
Such compression was exerted at many different times during the
Tertiary. Some areas show a record of almost continuous deforma-
tion through long spans of Tertiary time, and the sedimentary
sequences frequently contain so many unconformities that it is
diflicult to generalize any orogenic climaxes (Gilluly, 1949, pp. 567-
569). Nevertheless, two principal climaxes seem to have occurred,
one near the middle of the Miocene, the other early in the Pleistocene
(Reed and Hollister, 1936, pp. 1551-1597). It is interesting to note
that these climaxes of deformation are of about the same age as
those which have been inferred in the Great Basin area. Effects of
54 p. B. KING
the early Pleistocene erogenic climax are especially striking in the
Ventura and Los Angeles basins of southern California, where thick
masses of Pliocene and lower Pleistocene marine and land-laid
strata are steeply upended, and are overlaid by nearly undisturbed
later Pleistocene deposits. This has been termed the Pasadenan
orogeny (Stille, 1936, pp. 867-870).
The influence on the surface features of the varied faulting and
folding during difi^erent times since the beginning of the Tertiary
have been portrayed in many sets of paleogeographic maps prepared
by different geologists. The earlier, or mid -Miocene, deformation
shaped the ridges and troughs of the Coast Ranges into about their
present configuration, but left wide tracts of lower country still sub-
merged ; the later, or early Pleistocene, deformation produced wide-
spread emergence. During times of greatest submergence, the Coast
Range area probably resembled the present offshore region of south-
ern California, with shallow shelves, interspersed with much deeper
troughs, and linear islands that resembled the present Channel
Islands. During times of greatest emergence, the Coast Range area
probably resembled the present topography around San Francisco
Bay, with mountain ridges and intervening troughs or valleys, in
which land-laid sediments were being deposited, and whose lowest
parts, like the present bay, were covered by shallow, ramifying seas.
SUMMARY
Western North America is the region of the Cordilleran system of
mountain ranges, which extend inland from the Pacific Coast 400 to
1,000 miles to the Great Plains of the continental interior. The
landscape of the region has been shaped by surface processes of
erosion, sedimentation, and volcanism, but ultimate cause of the
features is deeper in the crust, in processes that have deformed the
rocks, brought about emplacement of magmas, and raised or lowered
large sections of the surface. These processes, though spasmodic, are
persistent through history. In considering the growth of a mountain
system such as the Cordillera, they may be generalized into a geo-
synclinal phase, an orogenic phase, and a post-orogenic phase.
The geosynclinal phase was a time of sedimentation and rather
mild crustal activity. In the Cordilleran region it persisted through
Paleozoic time and through the first half of Mesozoic time.
The orogenic phase began earliest in the western part of the
EVOLUTION OF MODERN SURFACE FEATURES 55
Cordillera, broadly in mid-I\Iesozoic time — in places in the Jurassic,
elsewhere somewhat later. Rocks formed in this part of the geo-
syncline were deformed, metamorphosed, and invaded by large
bodies of magma. The deformed rocks were raised into a land sur-
face, from which detritus was shed westward into the Pacific Ocean
basin, and eastward as a broad sheet into the interior of the con-
tinent, across the remainder of the geosyncline.
During Cretaceous time, deformation progressed eastward from
the initial disturbed belt, folding and faulting the rocks of the Great
Basin area, more lightly affecting those on the site of the Colorado
Plateau, and more heavily affecting those in the Rocky Mountains
beyond. In the southern part of the Rocky Mountains, zones of
weakness had already been created by mountain-making during
Paleozoic time. By the close of the orogenic phase, in Late Cre-
taceous and Paleocene times, deformation had reached the edge of
the present Great Plains, but it progressed no farther inland.
The folding and faulting of the orogenic phase did not produce the
modern topography. While the surface was raised and lowered by it,
leveling processes of erosion and sedimentation were active and pre-
vented development of strong relief; moreover, regional altitudes
remained low.
Modern surface features evolved by a multitude of crustal proc-
esses during the post-orogenic phase, in Tertiary and Quarternary
times. Intermontane basins subsided (as in Wyoming and Colorado),
large areas were broken up by block faulting (as in the Great Basin),
other large areas were overspread by lava (as in the Columbia
Plateau), and mountains were formed by the building of chains of
volcanoes (as in the Cascade Range). Besides, extensive regions
were uplifted relative to their surroundings, with little internal
deformation. The largest uplifted region centered in the Rocky
Mountains and extended into the Great Plains and Colorado
Plateau; it was raised mainly before later Tertiary time, but with
diminishing uplifts into the Pleistocene. Smaller, more complex
uplifts took place somewhat later in the Sierra Nevada and Cascade
Range; in the Sierra Nevada, uplift was accompanied by marked
faulting along the eastern side.
The post-orogenic (Tertiary and Quaternary) movements raised
the Cordilleran region to its present generally high altitude. Streams,
quickened by the uplift and by increased rainfall during the Pleisto-
56 p. B. KING
cene, etched out the mountains and canyons; mountain barriers
prevented free circulation of moisture-laden winds from the Pacific
and heightened the climatic contrasts. Since mid-Tertiary time,
regional relief, local relief, and climatic contrasts have been greater
in the Cordillera than at any earlier period.
Throughout geologic time, the Cordilleran system has been
bordered on the west by the deep Pacific Ocean basin, floored by
crustal material different from that of the continent. It is unlikely
that any additional lands ever existed offshore that have since
foundered to oceanic depths. More likely, continental area has been
added at the expense of ocean basin by various accretionary proc-
esses. On the other hand, land connections persisted intermittently
along the strike of the Cordilleran system, between North America,
Asia, and South America, as the coastal areas of all three are part of
a circum- Pacific belt of mountain structures whose origin, like the
North American Cordillera, extends far back into the geologic past.
Acknowledgments
This paper was compiled largely from existing publications, but its
context has been shaped to a considerable degree by the climate of thought
and opinion of the writer's many geological friends and colleagues, in
California and elsewhere in the west. Their observations and ideas, too
numerous to recall and mention separately, have given the writer many
insights into the interpretation of the printed record.
In particular, one or more of the versions of the paper have been
read by C. R. Longwell and G. D. Robinson of the U. S. Geological Sur-
vey, J. H. Mackin of the University of Washington, and A. O. Woodford
of Pomona College. Also, C. A. Repenning of the U. S. Geological Survey
has furnished helpful information on the history of the Colorado River
from his unpublished work. Their generous help and their thoughtful
criticisms are gratefully acknowledged, and have been carefully considered
in preparing final revisions.
Nevertheless, decisions as to the context of the paper are those of
the writer, and he assumes all responsibility for the views herein ex-
pressed, whether right or wrong. As one critic remarked, no two geologists
would summarize this complex and diverse subject in the same manner,
either in the subjects selected for coverage or in the interpretations
which are made of them. The perfect story of the evolution of the surface
features of western North America is yet to be written. The present paper
is an interim report which it is hoped will stimulate further thought,
especially in that fascinating no-man's land which lies between the
geological and the biological sciences.
EVOLUTION OF MODERN SURFACE FEATURES 57
REFERENCES
A complete list of references for a general review of this kind would
include nearly all the publications on western geology. Some sort of
selection is thus obviously necessary. Although I have not been entirely
consistent, I have, for the most part, restricted my documentation to
papers published in the last decade or two, and especially to papers
presenting novel or controversial matters. Well-known or long-established
facts of western geology are for the most part not documented. For these,
the reader can profitably consult various general works and compila-
tions, including those listed.
General References
Dunbar, C, O. 1949. Historical Geology. John Wiley and Sons, New York.
Eardley, A. J. 1951. Structural Geology of North America. Harper and
Brothers, New York.
Fenncman, N. M. 1931. Physiography of Western United States. McGraw-
Hill Book Co., New York.
Special References
Allen, V. T. 1929. The lone formation of California: Calif. Univ. Dept.
Geol. Sci. Bull, IS: 347-448.
Anderson, F. M. 1938. Lower Cretaceous deposits in California and
Oregon. Geol. Soc. Am. Special Paper 16.
Atwood, W. W., and W. W. Atwood, Jr. 1938. Working hypothesis for
the physiographic history of the Rocky Mountain region : Bull. Geol.
Soc. Am. 49: 957-980.
Axelrod, D. I. 1957. Late Tertiary floras and the Sierra Nevada uplift.
Bull. Geol. Soc. Am., 68: 19-45.
Baker, A. A., C. H. Dane, and J. B. Reeside, Jr. 1936. Correlation of
the Jurassic formations of parts of Utah, Arizona, New Mexico, and
Colorado. U. S. Geol. Survey Prof. Paper 183.
Bradley, W. H. 1936. Geomorphology of the north flank of the Uinta
Mountains. U. S. Geol. Survey Prof. Paper 185-1, pp. 163-204.
■ — — — . 1948. Limnology and the Eocene lakes of the Rocky Mountain
region. Bull. Geol. Soc. Am., 59: 635-648.
Bryan, Kirk. 1938. Geology and ground-water conditions of the Rio
Grande depression in Colorado and New Mexico. Natl. Res. Comm.,
Regional Plan., Pt. 6, Upper Rio Grande, pp. 197-225.
Burbank, W. S., and T. S. Lovering. 1933. Relation of stratigraphy,
structure, and igneous activity to ore deposition of Colorado and
southern Wyoming, in Ore Deposits of Western States (Lindgren
volume). Am. Inst. Min. Metall. Eng., pp. 272-316.
Chaney, R. W. 1938. Paleoecological interpretations of Cenozoic plants
in western North America. Bot. Rev., 9: pp. 371-396.
58 p. B. KING
Crowell, J. C. 1952. Probable large lateral displacement on San Gabriel
Fault, southern California. Bull. Am. Assoc. Petrol. Geologists, 36:
2026-2035.
Davis, W. M. 1925. The Basin Range problem. Proc. Natl. Acad. Sci., 11:
387-392.
Eardley, A. J. 1947. Paleozoic Cordilleran geosyncline and related
orogeny. ./. Geol, 55: 309-342.
Evernden, J. F., G. C. Curtis, and J. I. Lipson. 1957. Potassium-argon
dating of igneous rocks. Bull. Am. Assoc. Petrol. Geologists, 41:
2120-2127.
Ewing, J. L., C. B. Officer, H. R. Johnson, and R. S. Edwards. 1957.
Geophysical investigations in the eastern Caribbean ; Trinidad shelf,
Tobago trench, Barbados ridge, Atlantic Ocean. Bull. Geol. Soc. Am.,
65: 719-732.
Ewing, Maurice, and Frank Press. 1955. Geophysical contrasts between
continents and ocean basins. Geol. Soc. Am. Special Paper 62,
pp. 1-6.
Ferguson, H. G., and S. W. Muller. 1949. Structural geology of the Haw-
thorne and Tonopah quadrangles, Nevada. U. S. Geol. Survey Prof.
Paper 216.
Gilluly, James. 1949. Distribution of mountain building in geologic time.
Bull. Geol. Soc. Am., 60: 561-590.
Hill, M. L. 1954. Tectonics of faulting in southern California, in Geology
of Southern California, California Div. Mines Bull. 170, Chap. 4,
pp. 5-13.
Hill, M. L., and T. W. Dibblee, Jr. 1953. San Andreas, Garlock, and Big
Pine faults, California. Bull. Geol. Soc. Am., 64: 443-458.
Hodge, E. T. 1938. Geology of the lower Columbia River. Bull. Geol. Soc.
Am., 49: 831-930. (Review by J. H. Mackin, /. Geomorphology, 3:
70-35.)
Howard, A. D. 1958. Drainage evolution in northeastern Montana and
northwestern North Dakota. Bull. Geol. Soc. Am., 69: 575-588.
Hubbs, C. L., and R. R. Miller. 1948. The Great Basin, with emphasis on
glacial and post-glacial times. H. The zoological evidence: correla-
tion between fish distribution and hydrographic history in the desert
basins of western United States. Utah Univ. Bull., 38: 17-166.
Hunt, C. B. 1956. Cenozoic geology of the Colorado Plateau. U. S. Geol.
Survey Prof. Paper 279.
Irwin, P. L. 1957. The Franciscan group in the Coast Ranges and its
equivalents in the Sacramento Valley of California. Bull. Am. Assoc.
Petrol. Geologists., 41: 2284-2297.
Johnson, W. D. 1901. The High Plains and their utilization. U. S. Geol.
Survey 21st Ann. Kept., Pt. 4, pp. 601-741.
Kay, Marshall. 1947. Geosynclinal nomenclature and the craton. Bull.
Am. Assoc. Petrol. Geologists, 31: 1289-1293.
King, P. B. 1935. Outline of structural development of trans-Pecos Texas.
Bull. Am. Assoc. Petrol. Geologists, 19: 221-261.
EVOLUTION OF MODERN SURFACE FEATURES 59
Larsen, E. S., Jr., and Whitman Cross. 1956. Geology and petrology of
the San Juan region, southwestern Colorado. U. S. Geol. Survey
Prof. Paper 258. 303 pp.
Lee, W. T. 1907. Water resources of the Rio Grande Valley in New
Mexico. U. S. Geol. Survey Water-Supply Paper 188.
Longwell, C. R. 1946. How old is the Colorado River? Am. J. Sci., 244:
817-835.
• . 1950. Tectonic theory viewed from the Basin Ranges. Bull. Geol.
Soc.Am., di.- 413-434.
Louderback, G. D. 1904. Basin range structure of the Humboldt region.
Bull. Geol. Soc. Am. 15: 289-346.
Mackin, J. H. 1937. Erosional history of the Bighorn basin, Wyoming.
Bull. Geol. Soc. Am., 48: p. 813-894.
. 1947. Altitude and local relief of the Bighorn area during the
Cenozoic, in Field Conference in Bighorn Basin, Guidebook. Wyoming
Univ., Wyoming Geol. Assoc, and Yellowstone-Bighorn Research
Assoc, pp. 103-120.
McKee, E. D., S. S. Oriel, V. W. Swanson, M. E. MacLachlan, J. C.
MacLachlan, K. B. Ketner, J. W. Goldsmith, R. Y. Bell, and D. J.
Jameson. 1956. Paleotectonic maps of Jurassic system. U. S. Geol.
Survey Misc. Geol. Inv., map 1-175.
Menard, H. W., and R. S. Dietz. 1952. Mendocino submarine escarpment.
/. Geol, 60: 266-278.
Noble, L. F. 1954. The San Andreas fault zone from Soledad Pass to
Cajon Pass, California, in Geology of Southern California, Chap. 4
(Structural features). California Div. Mines Bull. 170, pp. 37-48.
Nolan, T. B. 1943. The Basin and Range province in Utah, Nevada, and
California. U. S. Geol. Survey Prof. Paper 197-D, pp. 141-196.
Powell, J. W. 1876. Report on the geology of the eastern portion of the
Uinta Mountains and a region of country adjacent thereto. U. S.
Geol. Geog. Survey of the Territories. 218 pp.
Reed, R. D., and J. S. Hollister. 1936. Structural evolution of southern
California. Bull. Am. Assoc. Petrol. Geologists, 20: 1533-1704.
Repenning, C. A., and J. H. Irwin. 1954. Bidahochi formation of Arizona
and New Mexico. Bull. Am. Assoc. Petrol. Geologists, 38: 1821-1826.
Repenning, C. A., J. F. Lance, and C. R. Longwell. A history of the Colo-
rado River. Bull. Geol. Soc. Am., in press.
Roberts, R. J., P. E. Hotz, James Gilluly, and H. G. Ferguson. Paleo-
zoic rocks of north-central Nevada. Bull. Am. Assoc. Petrol. Geolo-
gists, in press.
Rouse, J. T. 1937. Genesis and structural relationships of the Absaroka
volcanic rocks, Wyoming. Bull. Geol. Soc. Am., 48: 1257-1296.
Spieker, E. M. 1949. Sedimentary facies and associated diastrophism in
the Upper Cretaceous of central and eastern Utah, in Sedimentary
Facies in Geologic History. Geol. Soc. Am. Mem. 39, pp. 55-82.
Stille, Hans. 1936. Present tectonic state of the earth. Bull. Am. Assoc.
Petrol. Geologists, 20: 849-880.
60 P- B. KING
Taliaferro, N. L. 1942. Geologic history and correlation of the Jurassic
of southwestern Oregon and California: Bull. Geol. Soc. Am., 53:
71-112.
. 1943. Geologic history and structure of the central Coast Ranges
in California, in Geologic Formations and Economic Development of the
Oil and Gas Fields of California. California Div. Mines Bull. 118:
119-163.
Van Houten, F. B. 1948. Origin of red-banded early Cenozoic deposits in
Rocky Mountain region. Bull. Am. Assoc. Petrol. Geologists, 32:
2083-2126.
. 1956. Reconnaissance of Cenozoic sedimentary rocks of Nevada.
Bull. Am. Assoc. Petrol. Geologists, 40: 2801-2825.
1957. Appraisal of Ridgeway and Gunnison "tillites," south-
western Colorado. Bull. Geol. Soc. Am., 68: 383-388
Wallace, R. E. 1949. Structure of a portion of the San Andreas rift in
southern California. Bull. Geol. Soc. Am., 60: 781-806.
Waters, A. C, 1955a. Volcanic rocks and the tectonic cycle. Geol. Soc.
America Special Paper 62, pp. 703-722.
. 1955b. Geomorphology of south-central Washington, illustrated
by the Yakima East quadrangle. Bull. Geol. Soc. America, 66: 663-
684.
Woodford, A. O., and T. F. Harriss. 1938. Geological reconnaissance
across Sierra San Pedro Martir, Baja California. Bull. Geol. Soc. Am.,
49: 1297-1336.
Woodring, W. P. 1954. Caribbean land and sea through the ages. Bull.
Geol. Soc. Am., 65: 719-732.
Climate Since the
Late Cretaceous
H. D. MacGinitie
Humboldt State College, Areata, California
r ast climates and their changes comprise one
of the most fascinating subjects in science, since climates have so
profoundly affected the evolution and distribution of life on the
surface of the earth. Of one conclusion we can be sure: as we turn
back the pages into the past, we see that world climates were
greatly different from those of today. In order to appreciate just
how different, we have to clear the cobwebs of the present entirely
out of our minds. Some time ago when I was discussing with a well-
known western botanist the fossils of Melasequoia and its associates
found in the far north — the McKenzie basin, Greenland, the Arctic
Islands, and Alaska — I was astonished at his remark, "Why, how
could they grow there in all that ice and snow?" His thinking was
tied to present conditions. Another conclusion we can be sure of,
in thinking about past climates, is that the conditions of the Recent
and Pleistocene have been most unusual in the history of the world.
Our present combination of widely emergent and elevated conti-
nents, lofty mountain ranges, and polar glaciation has probably
existed (with recurrences in the past) for less than one-fiftieth of
geologic time.
As an illustration of the misconceptions that can result from
picturing the past too closely in terms of the present, here is a brief
quotation from a discussion of fossil arctic floras in a paper on the
evolution of plant associations (Mason, 1947, p. 206):
An earth, tilted on its axis relative to the plane of its orbit, will inevita-
bly be characterized by a darkened polar area that will alternate season-
ally with a lighted condition. The duration of the darkness will vary to
some extent with position but will range from a few days of total darkness
to almost six months of total darkness. By total darkness I mean the
61
62 H. D. MACGINITIE
absence of insolation capable of being converted into heat energy and of
light of sufficient value for use in photosynthesis. The area so involved
will be a disc approximately 3,000 miles in diameter. Receiving no insola-
tion, such an area would soon dissipate any residual heat in its soil and
rock surfaces. There would result extended and bitter arctic cold through-
out the darkened area that would affect winter temperatures for consider-
able distances into subarctic areas.
If we assume now that the poles have been stationary as most astron-
omers insist that they have, and if we assume that the continents and
ocean basins have been perpetuated in their present places through
geological time as many geologists insist that they have, we must con-
clude that no tropical, warm temperate, or even temperate forest flora
could possibly live and develop in high arctic latitudes. It would be too
cold on the one hand and too dark on the other hand.
Such statements neglect entirely changes in world climates, the
effects of past oceanic temperatures, and the effects of oceanic and
atmospheric circulation.
In order to arrive at a background for understanding later cli-
matic changes, we may turn now briefly to the world climate of the
late Cretaceous and early Tertiary. In the Upper Cretaceous the
continents appear to have been smaller and more occupied by
epicontinental seas than at any time since the Ordovician (Zeuner,
1945, p. 164). The continents were comparatively featureless and
rather uniformly of low elevation. North America was divided into
two subcontinents by a great inland sea extending from the Gulf of
Mexico to the McKenzie Delta, with an east-west breadth of about
12° of longitude. If we could transport ourselves back to the world
of the Upper Cretaceous, it would be like taking a flight to another
planet, so different would conditions seem. Just how different we
may never be able fully to know or appreciate. Tropical to sub-
tropical floras occupied most of the southern two-thirds of the
United States. When we investigate the late Cretaceous floras of the
far north we find an astonishing circumstance in terms of present
conditions. All around the North Pole, north of latitude 55°, we find
fossil floras dominated by temperate deciduous trees. Some of the
more significant localities of such floras are in western Greenland at
about 75° N. Lat., in Spitzbergen at about 78° N., and in the area
of the present Yukon Valley in Alaska at about 65° N. It has been
shown that these northern Cretaceous floras were zoned about
the North Pole just as floras are today farther south. In his work on
the late Cretaceous floras of the Rocky Mountain region, Dorf
CLIMATE SINCE THE LATE CRETACEOUS 63
(1942, pp. 100-103) has shown a definite change from subtropical
to warm-temperate floras between southern Colorado and Montana.
It appears clearly established that the area between the temperate
northern forests and the tropical forests at the southern border of
the United States was occupied by an ecotone characterized by a
gradual transition from the one type to the other. In considering
the "problem" of the northern floras (which is really no problem at
all) we have to remind ourselves again of conditions in the past.
All the evidence points to the fact that the seas were much warmer
than at present. As an example of this kind of evidence the attention
of the reader is called to a paper on Cenozoic marine climates of the
Pacific Coast by Durham (1950), who based his conclusions on an
intensive study of fossil reef-building corals and the associated
invertebrate faunas. His fundamental postulate was that living reef
corals cannot endure a minimum temperature much below 18° C. for
any length of time. Thus, he took the figure of 18° C for the coldest
month (February) as the limiting isotherm beyond which reef-
building corals cannot exist. According to the fossil corals of the
West Coast, the February isotherm of 18° C must have been located
at about 53° N. Lat. in the late Cretaceous. That is approximately
1,500 miles north of its present location on the coast of Lower
California. It is difficult to appreciate the full significance of such
a difference in ocean temperatures from that of the present.
Today a large proportion of the ocean is close to the freezing
temperature. Polar waters are denser than equatorial owing to the
low temperatures ; cold water settles in the polar regions and slowly
creeps along the sea floor to rise to tropical and equatorial regions
where it is warmed. Warm water from within the tropics moves
north at the surface to complete the thermal circulation. The layer
of warm water is comparatively shallow on account of the slow up-
welling of cold water from below. Thus, "the temperature of
abyssal waters in the open ocean basins is conditioned by the tem-
perature of surface waters in the polar regions" (Emiliani, 1954, p.
854). Even in equatorial regions the abyssal waters are close to the
polar waters in temperature. All the evidence that we now possess
indicates that this type of circulation existed throughout the
Tertiary. Emiliani (1958, pp. 57-58), from his tudy of a deep-sea
core, has indicated that the abyssal temperatures in the equatorial
Pacific in the Middle Oligocene were about 10° C, which implies a
64 H. D. MACGINITIE
similar mean temperature for the polar seas. Brooks (1951, p. 1005)
independently arrived at the same figure for polar oceanic tempera-
tures in the Middle Tertiary.
When warm surface water extends far to the north, atmospheric
and oceanic circulation must profoundly modify polar climates.
Any permanent ice caps would be impossible under such conditions,
although winter snows north of the Arctic Circle would be probable.
"Extended and bitter arctic cold" around the poles would not be
possible with the indicated ocean temperatures of the Upper Cre-
taceous and Lower Tertiary. The polar forests of those times were
deciduous, and it is a reasonable assumption that the deciduous
habit, at least in part, arose in response to photoperiodicity, as an
adaptation to the long period of winter darkness in polar regions,
rather than as an adaptation to thermoperiodicity.
If we turn to the Lower Tertiary, there is again abundant evidence
for the existence of a temperate deciduous forest occupying a zone
around the Pole. Several well-known localities are well within the
Arctic Circle. According to the best evidence available, these i\rcto-
Tertiary Geo-floras, as they have been called (Chaney, 1947, pp.
144-146), range in age from Paleocene to Middle Eocene. Some nota-
ble localities (Seward, 1933, pp. 408, 478-479) are in eastern Green-
land (70°-75° N. Lat.), Spitzbergen (78° N.), Elsmereland and
Grinnell Land (to 83° N.), the McKenzie River Delta (64° N.), and
the New Siberian Islands (75° N.). Farther south, to latitude 55°
N. in the central part of the continents, are many more fossil locali-
ties of this northern, summer-green forest. Among the characteristic
trees are the dawn redwood, ginkgo, sycamore, alder, oak, chestnut,
poplar, hazelnut, and many close relatives of trees now growing in
the deciduous forests of the Appalachians and eastern China. It
was, in no sense, a <:6>/(i-temperate flora. The species would find a
congenial habitat at present in the mountains of western North
Carolina at moderate elevations.
In the early Tertiary as well as in the Cretaceous there was a
zonal distribution of forests around the Pole that points clearly to
the fact that the Pole was in the same place as it is today (Chaney,
1940). There was a gradual transition from the tropical floras of the
Gulf states to the warm-temperate floras of Yellowstone Park and
southern Canada and thence to the temperate deciduous floras of
the far north. We can now amend the quotation given at the begin-
CLIMATE SINCE THE LATE CRETACEOUS 65
ning, and say that no tropical, warm-temperate, or even cool-
temperate, forest flora could possibly live and develop in high arctic
latitudes under present conditions. However, the conditions of the
early Tertiary at high latitudes were vastly difi^erent from those of
today. Durham (1950, pp. 1253-1254) concluded that during the
Eocene, the 18° C isotherm was at latitude 53° to 55° N., even farther
north than it was in the late Cretaceous. The fossil floras also indi-
cate that the temperatures of the Lower Tertiary may have been
higher than those in the late Cretaceous, since we have subtropical
floras, such as that at Raton, New Mexico (Knowlton, 1917, pp.
239-240), growing at moderate elevations, and this in spite of a
generally emergent continent and mountain building in the Cordilleran
region. The great inland seaway of the Upper Cretaceous was
drained at the close of that period. Intermittent mountain building
occurred throughout the area of the western Cordillera. The west-
ern mountains of the early Tertiary, with a few possible exceptions,
were of moderate elevation and did not seem to pose an insurmount-
able barrier to plant and animal dispersals, and the general elevation
of the continent was still comparatively low during the Lower
Tertiary. There seems to have been none of those great continental
upwarps that characterize the present Cordilleran region.
By the beginning of the Middle Eocene there were at least three
botanical provinces in western North America (MacGinitie, 1941,
pp. 92-95). In the far- western states a subtropical forest extended
along the coast as far north as latitude 55° N., and, with some modi-
fications, inland at least as far as the present area of northwestern
Wyoming. The Eocene flora of Kupreanofi^ Island in southeastern
Alaska, at Chalk Bluffs on the west slope of the Sierra, and at
Yellowstone Park have many characteristic plants in common.
The low-lying shores of the Mississippi embayment were occupied
by a warmer, practically tropical flora of quite different composi-
tion. Far to the north were the summer-green Arcto-Tertiary
forests.
Two Eocene floras are particularly significant with respect to
climatic trends: (1) the flora of the London Clay at latitude 52° N.
is of Lower Eocene age and is a tropical strand flora — not warm-
temperate, but tropical (Reid and Chandler, 1933, pp. 47-74); (2)
the Green River flora of Middle Eocene age, found at many localities
in northwestern Colorado and southern Wyoming, shows the
66 H. D. MACGINITIE
beginnings of climatic trends that were later accelerated. The flora
represented by the fossil leaves and fruits was a streamside and
lakeside flora of warm-temperate or subtropical aspect. The abun-
dance of small and coriaceous leaves and leaflets shows that the
vegetation on the open divides and higher ground around the lake
basins was somewhat like our modern subtropical scrub (Chancy,
1944). The pollen flora of the Green River gives us a picture of
temperate forests, with oaks and conifers, occupying the surrounding
uplands. Subhumid or even arid local conditions are indicated by
pollen of the desert shrub Ephedra. We also find in the Green River
flora a few representatives of the Arcto-Tertiary flora, the vanguard
of a dispersal, down the moderate elevations of the Rocky Mountain
axis, that was later to result in a complete replacement of the Lower
Tertiary forests. The negative evidence of the Green River flora is
significant. There is no pollen of grasses or other herbs except that
of a few primitive aquatic forms. There is no pollen of the sunflower
family or sagebrush or greasewood and the like. The modern her-
baceous vegetation or desert shrub vegetation evidently did not
exist in that area during the Middle Eocene (Wodehouse, 1933,
pp. 518-522).
A general view of the Eocene forests of the United States shows
us essentially tropical floras along the Gulf Coast, slowly merging
into warm-temperate floras at the north. There appears to have been
a slow shift to the north of these warmer floras, culminating in the
late Eocene (Chaney, 1947, p. 143). The most tropical Tertiary
flora of the West Coast is at Goshen, Oregon. All the Upper Eocene
floras at Comstock, Oregon, at Steel's Crossing, Washington, and
at LaPorte, California, have a definitely tropical aspect.
When the time boundary between the latest Eocene and the
Lower Oligocene is crossed, we find a marked climatic change, and
we can look down the vista of cooling and drying climates that
finally culminated in the glaciation of the Pleistocene. There was an
irregular, but, in the long run, a continuous change over the whole
world toward cooler and also, in general, drier climates. This trend
is clearly shown by the many fossil floras of the Upper Tertiary
that are scattered over the western states, from the high plains to
the Pacific Coast, and by the fossil floras of Europe and Asia. In a
recent study of fossil pollen from localities in southwestern Russia,
Bogelepov (1955, p. 988) has shown the same sequence of forest
CLIMATE SINCE THE LATE CRETACEOUS 67
types and climates from Oligocene to Pleistocene as we can trace
in the western states. This slow but inexorable climatic change
(MacDonald, 1953) profoundly affected the evolution of vegetation
types and their associated faunas. The Middle and Upper Oligocene
mark the influx from the north of Arcto-Tertiary species over the
western states. The trend toward cooler climates brought about the
southward dispersal of a host of temperate-forest trees and the
beginnings of the modern vertebrate faunas. By the Upper Oligocene
we find much of the earlier tropical or subtropical elements of the
floras displaced by northern forms whose ancestors were members
of the Eocene Arcto-Tertiary forests. A striking aspect of the Upper
Oligocene floras of the western states is the large number of species
related to those now living in the forests of eastern Asia. This
Asiatic aspect is one of the characteristic features of the western
Oligocene floras and is due, of course, to the fact that the Arcto-
Tertiary complex, as it dispersed southward, came down into both
eastern Asia and the western part of North America. Dozens of
common species in the western fossil floras have their living counter-
parts in the forests of eastern China (Chaney, 1947, p. 145). Among
the common genera are Acer, Ailanthus, Castanopsis, Celastrus,
Dipteronia, Exbiicklandia , Glyptostrohus, Holmskioldia, Afetaseqiwia,
Koelreuteria, Paliiirus, Pterocarya, Quercus (Asiatic types), and
Zelkova. The widespread Bridge Creek flora of late Oligocene age
occupied a large area from northern California into British Columbia
and eastward to Montana and Colorado. It is characterized by an
abundance of Metasequoia and Asiatic oaks. The Florissant flora of
Lower Oligocene age, in central Colorado, is extraordinarily rich in
warm-temperate species. It comprises many forms derived from the
earlier Green River flora, together with representatives of the flora
moving down from the north.
It is a curious fact that practically none of the western Oligocene
species having living relatives in eastern Asia was able to get into
Mexico or into the Appalachian region. A climatic barrier that
prevented migration either southward or eastward arose in the
Eocene and was well established in the Oligocene. The evidence
seems clear that this barrier was one of reduced rainfall. There is
good evidence, obtained from a study of the Green River and
Florissant floras (MacGinitie, 1953, pp. 52, 58), that an area of
subhumid scrub extended across northern Mexico and northward
68 H. D. MACGINITIE
across the United States in the region of the present high plains and
the prairies. While the relationship of the Oligocene floras is mark-
edly Asiatic, the early Eocene floras of the West Coast contained
many species that are related to plants now living in the upland
floras of Mexico and Central America. This indicates a rather free
interchange of floristic elements north and south at that time.
The later Tertiary was characterized by repeated flurries of
mountain growth, in the Cordilleran region and westward, which
finally culminated in the great uplifts of the late Pliocene and the
Pleistocene. This orogeny resulted in an increasing complexity of
climatic barriers and in the local differentiation of faunas and
floras. According to the coral faunas studied by Durham, the 18°
isotherm, by lower Miocene time, had moved down the West Coast
to approximately the latitude of northern California. The climate of
the western states in the Lower Miocene, though more genial than
at present, shows none of the subtropical aspects of the earlier
Tertiary (except along the coast at the south). The flora in Oregon
and Washington and over the northern Great Basin was essentially
a mixed deciduous-conifer forest of warm-temperate aspect, with
many species of deciduous trees having modern counterparts in the
Appalachian region and in eastern China. There is evidence of
abundant summer rainfall over the area which at present has little
or no summer rainfall. The climatic barrier to the south and in the
plains area that was initiated in the Eocene effectively prevented
the migration of forest species east-west and also north-south until
well into the Miocene. There appears to have been little or no ad-
mixture of forest species between the Appalachians and the Rocky
Mountains in the interval between the Lower Eocene and the Lower
Miocene. The Upper Miocene floras of the Columbia Plateau area
contain many species of oaks, elms, beeches, maples, and the like,
that are closely related to living species in the eastern states, indi-
cating a dispersal path between the two areas, probably through
southern Canada. As the climate cooled in the Upper Tertiary, the
vegetation of the region between the Mississippi and the Rocky
Mountains, which was at first a subtropical scrub, was slowly re-
placed by the modern herbaceous prairie vegetation.
Evolution of the herbs was comparatively rapid after the close of
the Oligocene. Pollen of the sunflower family (Compositae) first
becomes noticeable in the deposits of the Middle Miocene and such
CLIMATE SINCE THE LATE CRETACEOUS 69
pollen has not surely been found earlier than the Lower Miocene.
It is probable that the components of the existing prairies had their
beginnings about the Middle Miocene, although the prairies as
such do not seem to have developed until well into the Pliocene
(Elias, 1942; MacGinitie, 1953, p. 59). The climatic change (Chaney
and Elias, 1936, pp. 25-34) that stimulated the growth of herbaceous
vegetation had a profound, indirect effect on the evolution of the
mammals, since abundant new supplies of nutritious food became
available for herbivores. The fossil localities of the later Miocene
and Pliocene offer striking evidence of the astonishing abundance
of mammalian life on the Great Plains and westward.
By making comparisons between the present deciduous forest
floras of eastern Asia and North America we can gain some idea of
the herbs that came southw^ard with the dispersal of the Arcto-
Tertiary flora. Here we find closely similar or identical species of
herbs on the two continents, and these are almost entirely broad-
leafed, perennial forms with heavy rootstocks. Hui-Lin Li (1952,
pp. 385-405) has presented this evidence in his excellent paper on
the related floras of Asia and America.
The numerous Upper Miocene and Lower Pliocene floras of the
West have been studied by Axelrod (1956, 1957) and their climatic
significance has been well set forth. He has recognized about a half-
dozen climatic provinces — beginnings of the sharply demarked
climatic provinces now found in the area, but by no means as clearly
defined. He has also shown that the average temperatures were not
much higher than those of today, iDut that the summer maximum
temperatures were reduced and the winter minima considerably
raised; in other words, there was a much more equable climate.
The frost-free season in west-central Nevada was probably three or
four months longer than at present. Axelrod has also emphasized the
strong evidence for a shift in the pattern of seasonal distribution
and kind of precipitation, from summer showers and winter rain to
the present regime of dry summers and winter snows.
The late Miocene and early Pliocene floras from Nebraska to
California still indicate comparatively mild conditions, with, on the
whole, moderate rainfall. The presence of such trees as Cedrela
(cedro) and Per sea (avocado) in the latest Miocene suggests the
absence of severe winters, but the majority of the species are
essentially modern in aspect and are not greatly displaced north of
70 H. D. MACGINITIE
their present habitats. The northern oceans were still warmer than
at present. On the West Coast the 18° isotherm had moved to lati-
tude 35° N., 5° to 6° north of the existing location. There is no clear
evidence of permanent polar icecaps at this time. The composition
of the fossil flora that the writer has been collecting near Valentine,
Nebraska, at latitude 43° N., the richest late jVIiocene (or lowest
Pliocene) flora yet found in that area, indicates that the minimum
temperatures were higher than at present and that the severe out-
breaks of polar continental air that characterize the present winter
climate had not yet reached their later intensity. It is surprising to
find abundant Cedrela and Meliosma in a flora of Barstovian (late
Miocene) age in northern Nebraska, surprising, because these genera
are now confined to the tropics, although Meliosma grows at eleva-
tions of 6,000 feet in the mountains of southern Mexico. A majority
of the species, however, would find a congenial habitat in southeast-
ern Oklahoma, some 8° or 9° to the south.
Fr>'e and Leonard (1957) have been able to reconstruct the
sequence of late Tertiary climatic changes on the high plains by
studying the lithologic characters of the beds and the types of fossil
land snails found in them. The picture is one of steadily deteriorating
climates with decreasing rainfall, increased seasonal temperature
fluctuations, and lowered minimum temperatures. Conditions
essentially the same as those of the present were reached by the
Upper Pliocene. All except the hardiest and most drouth-resistant
trees of the once rich western montane floras had become extinct.
The seasonal distribution of rainfall, with the cooling of the border-
ing Pacific Ocean, had changed over the area west of the Rockies
from adequate rainfall at all seasons to the present Mediterranean
type with dry summers. Along the West Coast of the United States,
and especially in California, only those plants capable of withstand-
ing summer drouth were able to survive. Pollen studies show that
the prairies had become well established by the Middle Pliocene.
One of the climatic consequences of low^-lying continents and
warm oceans are truly equable climates, with comparatively small
seasonal temperature changes. In the modern world such climates
are found at moderate elevations in the tropical mountains, such as
the Tierra Templada of southern Mexico and Central America.
The earlier floras show conclusively that the modern severe winters
with their cold waves were nonexistent as late as the Upper Miocene.
CLIMATE SINCE THE LATE CRETACEOUS 71
The cooling continued until, in the late Miocene or Lower Pliocene,
winter snows may have occurred along the northern boundary of
the United States, but the outbreaks of polar air so characteristic
of the present winters appear to be a development of the late
Pliocene. The world climatic changes of the late Tertiary were
intensified and aggravated by the mountain building that reached
its peak at the close of the period. One of the effects of the climatic
changes that finally culminated in the Glacial period was an en-
largement of the area of polar climates and a compression or shrink-
age of the area occupied by temperate and tropical climates (Brooks,
1949, pp. 55-62). In the earlier Tertiary the area of warm-temperate
and tropical climates was enlarged at the expense of the area
occupied by polar climates, but this situation was gradually reversed
in the later Tertiary (Craig and Willett, 1951, pp. 381-382). The
zone of polar-front weather, marked by the succession of moving
high- and low-pressure areas, was greatly intensified, and moved
southward. In contrast, the polar front in pre-Miocene time must
have been nonexistent during the summer and of weak development,
far to the north, in the winter. During the Glacial stages the zone
of maximum cyclonic activity was even farther south than at present.
The southward movement of the polar front and the increased
temperature gradients caused the Glacial periods to be rainy or
pluvial periods in the zone just south of the glaciated area. The
large inland lakes of the Great Basin waxed and waned in response
to Glacial and Interglacial conditions. At the times of Glacial
advances the temperature gradient across the temperate zone,
between the Gulf and the northern states, must have reached a
maximum. Aianley (1955) has indicated that this temperature
gradient could have had at least twice its present value and has
estimated that at the time of maximum cooling the minimum annual
temperature, on the Fahrenheit scale, was lowered about 13° near
the Gulf, 16° at latitude 35° N., 20° in the Ohio Valley, and 27° at
New York.
Glaciers form wherever snowfall exceeds summer melting, and
the maximum development of Pleistocene glaciers was in just
those regions where at present there is maximum winter snowfall
and cool, cloudy summers. A comparatively slight lowering of
summer temperatures from that of the present would suffice to
reinitiate glaciation in those areas.
72 H. D. MACGINITIE
One of the distinguishing features of the Glacial ages seems to
have been the cyclic or periodic character of the climate — the
alternation of Glacial and non-Glacial stages. A new approach to
the problem of "fossil" temperatures has been developed by Urey
and his students (Urey, 1948; Emiliani, 1955, pp. 538-546). The
relative proportion of the oxygen isotope of mass 18 in carbonates,
for example, is inversely proportional to the temperature at which
the carbonate was formed. The ratio of the two isotopes (mass 18
and 16) can be determined accurately by spectrographic means.
Although many difficulties are still to be worked out, this method
of investigating past temperatures holds much promise and some
interesting results have already been achieved by Urey and by
Emiliani. Investigation of sea- bottom cores from the equatorial
and subtropical Atlantic Ocean has shown that there were no
periodic or cyclic temperature fluctuations during the Miocene or
Oligocene and that the "cause responsible for Pleistocene climatic
variations was not effective during Tertiary times" (Emiliani,
1956, pp. 285-287).
The distribution of living plants and animals in the present
temperate regions can be explained only on the basis of the violent
climatic fluctuations of the Pleistocene. The extent of these climatic
fluctuations can hardly be overemphasized. For instance, the climate
on the Michigan Peninsula varied from that of the frigid continental
icecap to climates warmer than at present. Along the front of the
glaciers there were changes from tundra through steppe to broad -
leafed forests, and back again. Studies have indicated that the snow-
line in all the high mountains of the world descended during times
of glaciation. It has been estimated (Leopold, 1951; Antevs, 1954;
Flint, 1957, p. 304) that the snowline on the mountains of New
Mexico, for example, descended approximately 4,000 feet below that
of the present. There is evidence from deep-sea cores that the
surface of the ocean also underwent refrigeration, even in the tropics.
Through the study of fossil pollen from scattered bogs, it has been
indicated that a cool-temperate climate extended from western
Florida to near Austin, Texas (Brown, 1938; Davis, 1946, pp.
193-196; Potzger and Tharp, 1947, 1954). The lower levels of these
bogs contain pollen of spruce and fir species now characteristic of
forests around the Great Lakes. The distribution of the bogs indi-
cates that these cool-temperate forests could hardly have been small
CLIMATE SINCE THE LATE CRETACEOUS 73
isolated islands of such forest types. A few small fossil floras show
that the climate of southern California was cooler and moister than
at present. Such examples could be increased almost indefinitely
(see, for example, Murray, 1957). On the other hand, studies of fossil
pollen give evidence of the existence of oak-hickory forests during
Interglacial periods in areas around the Great Lakes that were
occupied by ice during the Glacial stages.
The succession of Glacial and Interglacial stages was no doubt
the impetus for plant and animal dispersals north-south and up and
down in the mountainous areas. The distributional, ecological, and
speciational changes may be inferred, as follows. As the climate
ameliorated in an Interglacial interval, southern forms expanded
their habitat areas to the north and upward, while withdrawing
at the south. This northward extension continued until the climatic
trend was reversed. Isolated, relict areas of occupancy were left
scattered in favorable, or at least tolerated, locations south (and
possibly west) of the main occupied area. These relict areas, for
species dispersing northward, were on the higher elevations and on
cool north slopes, and may have ofTered especially favorable condi-
tions for the beginning of further speciation. Uninhabited areas,
newly exposed by the retreating ice, may have presented somewhat
different environments and changing competition to the vanguard
of the northward dispersal. With a turn toward advance of the ice
sheets, areas of occupancy tended to be driven southward, posing
new competitors and, perhaps, putting a premium on adaptability
to unaccustomed foods. There were many changes in local physio-
graphic barriers, ice sheets, rivers, and lakes.
Pollen studies indicate that vegetational changes in middle lati-
tudes were marked. There is evidence that the prairies moved
northward and, in response to warmer and drier conditions, also
eastward during Interglacials. During pluvial Glacial stages prairies
invaded the eastern areas of our south-western deserts. During such
times of cyclic climatic changes the stimuli to admixture, hybridi-
zation, and natural selection must have been Intensified. The effects
on life were naturally greatest along the southern extension of the
glacial fronts, but these effects are found far to the south (in the
mountains of Mexico, for instance). Apparently the most favored
areas climatically were along the Pacific Coast and the southern
Atlantic seaboard. It is probable that there were dispersals back and
74 H. D. MACGINITIE
forth along the Gulf Coast from the Appalachians to the mountains
of eastern Mexico (Sharp, 1950, pp. 316-318).
The world climate has undergone striking fluctuations since the
retreat of the last continental glacier, without physiographic changes
of any consequence. A gradual warming culminated in the "climatic
optimum" (about 6,000 years ago), followed by a return to cooler
conditions. Now a warming trend seems to have been renewed.
Prehistoric sites of human habitation in the western states show
clear evidence of great climatic instability since the retreat of the
glaciers (Malin, 1957). Occupance layers are separated by thick
layers of wind-blown dust that indicate intervals when the sites
were uninhabited and when the vegetational cover was at a mini-
mum. There are historical accounts of severe dust storms in the
Plains states long before modern settlement and the "plowing of
the plains." One of the latest effects of climatic changes is the
spread of the tropical deserts from western India across the
Mediterranean and northern Africa, and in our own Southwest
(Wadia, 1955).
Attention is called to two stimulating papers dealing with the
present apparently erratic distribution of certain vertebrate ani-
mals. In dealing with the biogeographical problems concerning some
American genera of salamanders, Lowe (1950) has plausibly ex-
plained the puzzling distribution of these animals by a considera-
tion of late Tertiary and Pleistocene changes. Smith (1957) has
treated some unusual problems concerning the distribution of mam-
mals in the north-central states. Almost any type of erratic distri-
bution and almost any inconsistency of distribution appear possible
when the effects of climatic changes in the later Tertiary and Pleis-
tocene are considered.
The world climate has been comparatively stable throughout the
ages, but subject, at times, to the most amazing variations. In
emphasizing certain aspects of past climates the writer has hoped to
furnish some hints concerning the remarkable effects of climatic
changes on the evolution and distribution of living plants and
animals.
Space does not permit a critical presentation of all the different
theories and ideas as to the causes of world climatic changes (Flint,
1957; Willett, 1953). However, in considering these causes it is al-
ways necessary to go back to the two fundamental controls of world
CLIMATE SINCE THE LATE CRETACEOUS 75
climate: (1) composition of the atmosphere and (2) amount and
kind of solar radiation. Without doubt there have been changes in
both of the fundamental controls during geologic time. In addition,
it is important to note that changes in solar radiation can also affect
the composition of the atmosphere by changing the amount of both
water vapor and carbon dioxide. Thus the two controls are not inde-
pendent. As far as we know now the two constituents of the atmos-
phere most concerned with world climate are carbon dioxide and
water, although the concentration of oxygen and ozone aloft may
also play a part. Carbon dioxide and water both act to absorb earth
radiation while they are comparatively transparent to short-wave
solar radiation. Thus the surface of the earth is blanketed by these
gases and, as a consequence, is much warmer than it would be
without them, and daily fluctuations are much reduced. Recent
studies of the absorption bands of carbon dioxide indicate that it
can have a rather large effect independently of the presence of water
vapor. Plass (1956) brought up to date the climatic effects of changes
in the concentration of carbon dioxide. However, he did not explain
convincingly the role of this gas in initiating world wide climatic
changes, such as the beginning or ending of the Glacial periods.
It is only necessary to recall again the climatic changes between the
spring of 1956 and of 1957 to realize that circulation patterns can
vary remarkably from one year to another without changes in the
composition of the atmosphere. We still have much to learn con-
cerning the true causes of these year-to-year fluctuations, let alone
those of longer periods. The problem of the function of carbon
dioxide as an atmospheric climatic control is most complex, and
several important questions remain unanswered. Removal of carbon
dioxide from the atmosphere by natural causes might lower world
temperatures. Removal is accomplished by lime-secreting organisms,
by the weathering of the rocks, and by the deposition of oil, coal,
and the like. When we consider the huge limestone deposits of the
Paleozoic and the Cretaceous, together with the accompanying coal
deposits, we wonder if the concentration of carbon dioxide in the
atmosphere has not been tremendously reduced since pre-Cambrian
days. If the role of carbon dioxide in the atmosphere is of climatic
importance, there must be some natural means of replenishing the
atmospheric supply. The glaciation of the late Paleozoic might be
a natural consequence of the removal of the gas in the formation of
76 H. D. MACGINITIE
the Paleozoic limestone beds, but what brought the return of the
mild climates in the Mesozoic? As far as we know now, the only
source of carbon dioxide in any quantity is volcanism. Yet intense
and long-continued volcanism seems to precede rather than follow
Glacial ages.
Carbon dioxide is more soluble in cold water than in warm. The
present cold oceans are a storehouse for incredible amounts of CO2.
If the climate should become warmer, large amounts of the gas would
be released to the atmosphere. But here we see that an increase of
carbon dioxide is an effect of, rather than the cause of, warmer
climate. Warmer climates also mean an increase in the total amount
of water vapor in the atmosphere. There is little question that
changes in the concentrations of these gases tend to emphasize
climatic fluctuations. The role of continentality in initiating or
terminating Glacial ages has been greatly overemphasized. No
known distribution of land and water and no known variations in
topography are adequate to account for the changes in climate
since the Upper Cretaceous. Anyone who is familiar with the cli-
matic change in the central United States between the spring of
1956 and the spring of 1957 must be aware that some other efifect
than size, shape, and topographic relief of the continents must be
the cause of major changes in circulation patterns. Terrestrial factors
are capable of increasing climatic contrasts and channeling currents
of air and water, but they cannot, on the basis of our present knowl-
edge, affect the climate of the earth as a whole (Willett, 1953, pp.
58-59). The solution of the problem of changing climates is not to
be found in the theories of wandering poles and drifting continents.
Any forms of these theories yet developed directly contradict the
known facts concerning the distribution of fossil floras. In addition
to the negative biologic evidence there is also direct physical evidence
against the idea of wandering poles. From his study of the orientation
of magnetic grains in sediments, Hospers (1955) has "concluded
that the large amount of polar wandering suggested by Kreichgauer,
Koppen and Wegner, and Milankovitch cannot be reconciled with
the new data. If ... at all ... it ha& not exceeded 5°-10° since
Eocene times."
The evidence of a recent warming of world climate is clear. If the
present trend toward warming and drying continues, our south-
western deserts will eventually expand into Oklahoma, Texas, and
CLIMATE SINCE THE LATE CRETACEOUS 77
Kansas, and the prairies will move eastward and northeastward.
Is this warming and drying trend due to the enormous amounts of
carbon dioxide being returned to the atmosphere through the
burning of fossil fuels, as Plass believes, or is it due to some secular
change in solar radiation? In this connection, accumulating evidence
indicates that short-wave and corpuscular radiations from the sun
appear to fluctuate rather markedly, and that the amounts of such
radiation absorbed by the outer atmosphere may produce rather
large effects in modifying atmospheric circulation patterns (Craig
and Willett, 1951 ; Willett, 1953, pp. 62-69).
In his study of past climates the writer has become convinced
that the fundamental cause of world climatic changes has its origin
in small fluctuations in the amount and kind of solar radiation
(see also Willett, 1953, pp. 57, 61; Flint, 1957, pp. 481-509). Opik
(1958) has developed what is perhaps the first plausible mechanism
for long-term changes in solar radiation. These solar changes are
considerably modified by the resulting changes in ocean tempera-
tures, concentrations of H2O and CO2, and, on a more local scale,
by topographic changes. The problem is a complex one, but the
writer, on the basis of present evidence, always returns to the
conclusion that the primary cause lies outside the earth itself.
Brooks' solar-topographic hypothesis (Brooks, 1951, pp. 1016-1017)
offers an adequate and satisfying explanation of the observed
facts.
REFERENCES
Antevs, E. 1954. Climate of New Mexico during the last Glacio-pluvial
/. Geol, 62: 182-191.
Axelrod, D. I. 1956. Mio-Pliocene floras from west central Nevada.
Univ. Calif. Pubis. Geol. Sciences, 33: 1-322.
— . 1957. Late Tertiary floras and the Sierra Nevada uplift.
Bull. Geol. Sac. Am., 68: 19-46.
Bogolepov, K. V. 1955. Stages in the development of the Tertiary vegeta-
tion in the Angara region of the Enisei ridge. Doklady Akad. Naiik
SSSR, 100: 985-988.
Brooks, C. E. P. 1949. Climate through the Ages. McGraw-Hill, New York.
. 1951. Geological and historical aspects of climatic change.
Compendium Meteorol., pp. 1004-1023.
Brown, C. A. 1938. The flora of Pleistocene deposits in the western
Florida parishes; West Feliciana Parish, East Baton Rouge Parish,
Louisiana. Louisiana Geol. Survey, Geol. Bull., 12: 59-96.
78 H. D. MACGINITIE
Chaney, R. W. 1940. Tertiary forests and continental history. Geol. Soc.
Am. Bull., 51: 469-488.
. 1944. A fossil cactus from the Eocene of Utah. Am. J. Botany, 31:
507-528.
1947. Tertiary centers and migration routes. Ecol. Monographs,
17: 139-148.
Chaney, R. W., and M. K. Elias. 1936. Late Tertiary floras from the high
plains. Carnegie Inst. Wash. Publ. No. 476: 1-72.
Craig, R. A., and H. C. Willett. 1951. Solar energy variations as a possible
cause of anomalous weather variations. Compendium Meteor ol.,
pp. 378-390.
Davis, J. H., Jr. 1946. The peat deposits of Florida, their occurrence,
development and uses. Florida Geol. Survey, Geol. Bull. 30.
Dorf, E. 1942. Upper Cretaceous floras of the Rocky Mountain region.
Carnegie Inst. Wash. Publ. No. 508: 1-168.
Durham, J. W. 1950. Cenozoic marine climates of the Pacific coast.
Bull. Geol. Soc. Am., 61: 1243-1264.
Elias, M. K. 1942. Tertiary prairie grasses and other herbs from the
High Plains. Geol. Soc. Am. Special Paper 41.
Emiliani, Cesare. 1954. Temperatures of Pacific bottom waters and polar
superficial waters during the Tertiary, Science, 119: 853-855.
. 1955. Pleistocene temperatures. J. Geol., 63: 538-573.
. 1956. Oligocene and Miocene temperatures of the equatorial and
subtropical Atlantic Ocean. /. Geol, 64: 281-288.
1958. Ancient temperatures. Sci. American, 198: 54-63.
Flint, R. F. 1957. Glacial and Pleistocene Geology. John Wiley & Sons,
New York.
Frye, J. C, and A. B. Leonard. 1957. Ecological interpretations of Plio-
cene and Pleistocene stratigraphy in the Great Plains region.
Am. J. Sci., 255: 1-11.
Hospers, J. 1955. Rock magnetism and polar wandering. /. Geol., 63:
59-74.
Knowlton, F. H. 1917. Fossil floras of the Vermejo and Raton formations
of Colorado and New Mexico. U. S. Geol. Survey Prof. Paper 101:
223-455.
Leopold, L. B. 1951. Pleistocene climate in New Mexico. Am. J. Sci.,
249: 152-168.
Li, Hui-Lin. 1952. Floristic relationships between eastern Asia and
eastern North America. Trans. Am. Phil. Soc, N. S., 42, Pt. 2: 371-
405.
Lowe, C. H., Jr. 1950. The systematic status of the salamander Plethodon
hardii, with a discussion of biogeographical problems in Aneides.
Copeia (2) : 92-99.
MacDonald, J. R. 1953. Climate of western South Dakota during the
Oligocene epoch. Program Geol. Soc. Am., Cordilleran Sect., p. 17.
CLIMATE SINCE THE LATE CRETACEOUS 79
MacGinitie, H. D. 1941. A Middle Eocene flora from the central Sierra
Nevada. Carnegie Inst. Wash. Publ. No. 534: 70-78.
. 1953. Fossil plants of the Florissant beds, Colorado. Carnegie
Inst. Wash. Publ. No. 599.
Malin, J. C. 1957. Review of "The North American grassland in historical
perspective," by J. E. Weaver and F. W. Albertson, Ecology, 38:
362-363.
Manley, G. 1955. A climatological survey of the retreat of the Laurentide
ice sheet. Am. J. Sci., 253: 256-273.
Mason, H. L. 1947. Evolution of certain floristic associations of western
North America. Ecol. Monographs, 17: 202-210.
Murray, K. F. 1957. Pleistocene climate and the fauna of Burnet's Cave,
New Mexico. Ecology, 38: 129-132.
Opik, Ernst J. 1958. Climate and the changing sun. Sci. American, 198:
85-92.
Plass, G. N. 1956. Carbon dioxide and the climate. Am. Scientist, 44:
302-316.
Potzger, J. E., and B. C. Tharp. 1947. Pollen profile from a Texas bog.
Ecology, 28: 274-280.
— . 1954. Pollen study of two bogs in Texas. Ecology, 35: 462-466.
Reid, E. M., and M. E. J. Chandler. 1933. The flora of the London Clay.
British Museum, London.
Seward, A. C. 1933. Plant life through the ages. Cambridge University
Press, Cambridge, England.
Sharp, A. J. 1950. Characteristics of the vegetation in certain temperate
regions of eastern Mexico. Ecology, 31: Z\2>-3?)i.
. 1953. Notes on the flora of Mexico. /. Ecology, 41: 377-378.
Smith, P. W. 1957. An analysis of post-Wisconsin biogeography of the
Prairie Peninsula region based on distributional phenomena among
terrestrial vertebrate populations. Ecology, 38: 205-218.
Urey, H. C. 1948. Oxygen isotopes in nature and the laboratory. Science,
10: 489-496.
Wadia, D. N. 1955. Deserts of Asia — their origin and development in
late Pleistocene time. Second Seivard Mem. Led. Birbal Sahni
Institute of Paleobotany, Lucknow.
Willett, H. C. 1953. Atmospheric and oceanic circulation as factors in
glacial-interglacial changes of climate. In H. Shapley, Climatic
Change, pp. 51-71. Harvard University Press, Cambridge, Mass.
Wodehouse, R. P. 1933. Tertiary pollen. 11. The oil shales of the Green
River formation. Bull. Torrey Botan. Club, 60: 479-524.
Zeuner, Frederick E. 1945. The Pleistocene Period. Ray Society, London.
— — — . 1952. Dating the Past, 3rd edition. Methuen, London.
The Role of Physiology
in the Distribution of
Terrestrial Vertebrates
George A. Bartholomew
Department of Zoology, University of California,
Los Angeles
1 he inclusion of this paper in a symposium on
the origins and affinities of the land and freshwater fauna of western
North America may be taken as an expression of the tacit assumption
of most biologists that physiology plays a determining role in the
complex problems of animal distribution. I have accepted this
assumption, but in attempting to formulate conclusions available
from present knowledge, I find that the relation of physiology to
distribution in terrestrial vertebrates is neither direct, simple, nor
obvious. All that a brief essay such as this can do is offer a point of
view with regard to certain groups. To attempt a taxonomically
extended treatment of a topic so broad would be presumptuous, and
I shall concentrate on the animals that I know best — the amniotes.
The literature cited is not exhaustive, but most of the papers are
quite recent, and all include extensive bibliographies that offer
convenient access to the literature relevant to the role of physiology
in the distribution of terrestrial vertebrates.
Biology is a continuum, but we biologists, because of our limita-
tions, divide ourselves into categories, and then we pretend that
these categories exist in the living systems that we study. From the
functional point of view, of course, an animal is indivisible, and
physiology is not in any sense an isolatable component of an organ-
ism. If physiology is defined as the study of vital functions, it be-
comes inseparable from morphology and behavior. When one defines
physiology as broadly as this and then undertakes to discuss its role
in distribution, one attempts the impossible — nothing less than an
81
82 G. A. BARTHOLOMEW
interpretation of all the ways in which the dynamic capacities of an
organism influence its distribution. In the present paper therefore,
we shall restrict our discussion to the kinds of data that comparative
physiologists and physiological ecologists gather. In this way we can
confine our topic to reasonable limits and also insure that we have
at least some data on which to base our conjectures.
Once an organism has been identified, two of the most obvious
questions to ask are first, "How many are there?" and second,
"Where do they live?" Simple as these questions are, they are
usually extremely difificult to answer. But let us assume that, by
years of unremitting effort, we have succeeded in obtaining approxi-
mate answers to these obvious questions. Since abundance and dis-
tribution may be considered as different aspects of the same problem
(Andrewartha and Birch, 1954, p. 5), two additional and inextricably
interlocked questions inevitably present themselves: first, "Why are
there as many as there are?" and second, "Why do they live where
they do?" We may start our inquiry concerning the role of physi-
ology in distribution by asking the straightforward question,
"What information do physiologists supply that relates more or less
directly to the above questions, particularly to the last one, which is
a major concern of most students of distribution?" Unfortunately it
is useless to pretend that answers to these questions can supply us
with much that is specifically and immediately relevant; first,
because of the complexity of both physiology and distribution, and
second, because physiologists have only infrequently considered
these questions.
It is obvious that an organism's distribution is a complex integra-
tion of all facets of its present biology, together with a past history
in which chance has played an indeterminable but not necessarily an
unimportant role. Moreover, the occurrence of an organism is
dependent not only on a complex summation of its present and past
activities plus chance; it is often profoundly influenced by the occur-
rence or non-occurrence of other organisms, and these organisms
may be of quite a different nature and have difi'erent physiological
tolerances, requirements, and reactions from the one whose distri-
bution is being studied.
Viewed in this context it is obvious that most present knowledge
of the physiology of terrestrial vertebrates is likely to have either no
apparent distributional importance or to have a contribution so
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 83
broad that It is of little assistance In the analysis of any specific
distribution. The aspects of physiology that are directly pertinent
to distribution — and these are the only ones with which it Is ordi-
narily possible to deal — are not those concerned with internal inte-
gration, but are those that cither involve the animal's exchanges
with the environment or control and regulate these exchanges, and
those that affect reproductive performance. The exchanges referred
to involve food, water, heat, radiation, and metabolic wastes, and
are usually studied in terms of rates and limits. The factors con-
trolling reproductive performance under natural conditions are at
present only in the first stages of analysis (Lack, 1954) and offer a
challenging series of problems related to distribution.
Since an organism is Inseparable from its environment, any person
who attempts to understand an organism's distribution must keep
constantly in mind that the item being studied is neither a stuffed
skin, a pickled specimen, nor a dot on a map. It is not even the live
organism held In the hand, caged in the laboratory, or seen in the
field. It is a complex Interaction between a self-sustaining physico-
chemical system and the environment. An obvious corollary Is that
to know the organism it is necessary to know its environment. If
this view is valid, and if the distributlonally relevant data of physiol-
ogy relate to the dynamics of the complex Interaction between
organism and environment, then to evaluate the contribution of
physiological data to knowledge of distribution, one must first
examine the environment critically, analytically, and in detail.
Obviously a searching examination of the environment cannot be
made In a general discussion addressed to only the broad aspects of
the problem, but for purposes of comparison we may consider the
sea. From the point of view of this discussion, the most conspicuous
feature of the open sea is that it offers few places for an animal to go
to avoid unfavorable conditions that may develop locally. If one
excludes shore and estuarlne areas, the number of aquatic micro-
habitats that offer significant possibilities of escape from unfavorable
conditions is negligible. We can therefore expect that marine organ-
isms will often be limited in distribution by physical conditions,
particularly temperature. In contrast, the terrestrial environment
and to a lesser degree the freshwater habitat offer many mlcrohabl-
tats that make available an enormous range of temperature, mois-
ture, and radiation.
84 G. A, BARTHOLOMEW
On land an almost infinite series of physical situations is available.
Plants, generally speaking, meet the impact of the terrestrial environ-
ment head on, although of course they in turn modify the physical
environment by adventitious group activity. The individual plant
cannot select its habitat ; its location is largely determined by the
vagaries of the dispersal of seeds or spores and is thus profoundly
affected by chance. Because of their mobility and their capacity for
acceptance or rejection terrestrial animals, in contrast, can and do
actively seek out and utilize the facets of the environment that
allow their physiological capacities to function adequately. This
means that an animal by its behavior can fit the environment to its
physiology by selecting situations in which its physiological capaci-
ties can cope with physical conditions. If one accepts this idea, it
follows that there is no such thing as The Environment, for there
exist as many different terrestrial environments as there are species
of animals.
We can now take a somewhat closer look at the relation of physi-
ology to distribution. First of all, we must consider what questions
the student of ecological animal physiology is trying to answer. (A
more realistic approach might be to ask to what questions can con-
veniently obtained physiological data be applied.) It usually de-
velops that after much laborious and frustrating effort the investi-
gator of environmental physiology succeeds in proving that the
animal in question can actually exist where it lives. It is always
somewhat discouraging for an investigator to realize that his efforts
can be made to appear so trite, but this statement does not belittle
the ecological physiologist. If his data assist the understanding of
the ways in which an animal manages to live where it does, he makes
an important contribution to the study of distribution, for the pres-
ent is necessarily a key to the past.
The contributions of physiological knowledge to an understanding
of distribution are necessarily inferential. Distribution is a historical
phenomenon, and the data ordinarily obtained by students of physi-
ology are essentially instantaneous. However, every organism has a
line of ancestors which extends back to the beginning of life on
earth and which, during this immensity of time, has invariably
been able to avoid, to adapt to, or to compensate for environmental
changes. By examining in retrospect this prolonged exercise in the
art of survival and at the same time bearing in mind the physio-
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 85
logical capacities of living forms, it is possible to adduce some obvi-
ous, familiar, and general statements about the broad relations of
physiology to the distribution of terrestrial vertebrates. Such an
effort is greatly facilitated by application of Liebig's law of the
minimum (Hesse, Allee, and Schmidt, 1951, p. 26), one of the most
useful of generalizations to which an ecological physiologist can turn.
In the context of the present essay this generalization may be stated
thus : the distribution of a species will be controlled by that environ-
mental factor for which it has the narrowest range of adaptability or
control. The limiting factors will of course be different at different
stages in the life cycle and will vary from group to group and from
time to time.
The evolution of terrestrial vertebrates has been characterized
first, by increasingly effective homeostatic mechanisms and second,
by increasingly variable and flexible behavior. Together these two
trends mean that the evolutionary history of vertebrates has resulted
in increasing physiological competence and, at the same time,
increasing capacity to select from the environment the special physi-
cal situations that are appropriate to an animal's physiological
capacity. This increase in ecological versatility allows some forms
to occupy a remarkably diverse array of habitats and makes the
determination of distributionally limiting factors an intriguingly
subtle problem. If we examine the major groups of terrestrial verte-
brates with regard to the aspects of their physiology that are likely
to be limiting, we can make several obvious general observations.
Amphibians. Amphibia show poor osmoregulation (see Sawyer,
1956, for a recent review), poor control of water loss (Cohen, 1952;
Thorson, 1956), and complete lack of physiological thermoregulation
other than the passive cooling incidental to dehydration.
Reptiles. Of the major homeostatic capacities reptiles lack only
effective physiological thermoregulation, and they compensate for
this with surprisingly effective behavioral thermoregulation (Cowles
and Bogert, 1944; Bogert, 1949; Norris, 1953). A dramatic example
of behavioral thermoregulation is shown by the Andean lizard
Liolaemus multiformis, which under some circumstances can achieve
body temperatures as much as 30°C above air temperature (Pear-
son, 1954a).
Birds. Birds have reached a level of homeostatic control com-
parable to that of mammals. Considering their small size, they have
86 G. A. BARTHOLOMEW
remarkable powers of thermoregulation. Their capacity to tolerate
severe hyperthermia allows them to operate effectively at remark-
ably high environmental temperatures (Bartholomew and Dawson,
1958), and their high rate of heat production, effective insulation,
and peripheral vasomotor control allow them to operate at extremely
low environmental temperatures (Scholander et al., 1950a; Wallgren,
1954; Irving et al., 1955). With regard to water, however, birds have
less independence of the environment than do many mammals.
In the birds that have been measured, evaporative water loss
exceeds metabolic water production even under resting conditions.
(Bartholomew and Dawson, 1953). This unfavorable relationship
necessitates a high intake of water either through drinking or the
eating of succulent foods, which places birds, particularly small
ones, at a disadvantage with regard to the occupancy of arid re-
gions (Bartholomew and Cade, 1956).
Documented records of both daily and seasonal torpidity are now
available for adult birds in four different orders (see Bartholomew,
et al., 1957, for a summary). Although the advantages of torpidity
with regard to energy conservation are obvious for birds of extremely
high metabolism, such as humming birds (Pearson, 1954b), or for
birds dependent on periodically unavailable food (swifts, poor-wills,
and nighthawks) , the limited number of species and the fragmentary
nature of the available data do not warrant rigorous distributional
inferences.
Mammals. One of the most impressive attributes of mammals is
the excellence of the physiological homeostasis that they have at-
tained ; one form or another is able to meet head on the most severe
naturally occurring environmental conditions of heat, cold, or
aridity. Hence, any taxonomically extensive generalizations concern-
ing physiologically determined distributional limits are apt to be
particularly unsatisfactory in this group. Large arctic mammals by
the excellence of their insulation and vasomotor control can main-
tain a difference of as much as 70° C between air and deep body
temperatures without increasing metabolism above basal level or
decreasing the deep body temperature (Scholander et al., 1950b;
Scholander, 1955).
Most medium to small-sized mammals living in areas of very high
environmental temperatures avoid heat stress by being fossorial,
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 87
nocturnal, or both. Such patterns of behavior are often impossible
for large mammals, but if they can sweat and if drinking water is
available, they are able to cope with any high air temperatures that
occur naturally. In at least one large mammal, the dromedary camel
{Camelus dro^nedarius) , tolerance of hyperthermia contributes
significantly to effectiveness of adaptation to high ambient tempera-
tures by allowing heat storage rather than by requiring heat dissi-
pation through evaporation of water (Schmidt-Nielsen et al., 1957).
The availability of surface water is of no importance in the distri-
bution of many desert rodents. Several species in the family Hetero-
myidae lose so little water through evaporation, excretion, and
defecation, that as long as they are not forced to resort to evaporative
cooling, they are able to produce all the water they need through
their own metabolism even while subsisting on a dry diet (see
Schmidt-Nielsen and Schmidt-Nielsen, 1952, for an extensive
review). It has yet to be demonstrated, however, that large herbiv-
orous mammals can produce enough metabolic water while on a dry
diet to compensate for water losses. Unlike a rodent, the larger
mammals cannot escape the heat of the day by burrowing and must
therefore depend in part on evaporative cooling to prevent harmful
hyperthermia. Nevertheless, the capacity of some large herbivores
to go without water is impressive. A dromedary camel exposed to the
full heat load of radiation from sun and ground during the summer
at a Saharan oasis survived a 17-day period on a dry diet without
water (Schmidt-Nielsen et al., 1956). Its performance is attributed to
its capacity to tolerate a loss in body water equivalent to 30 per cent
of its body weight. (Most mammals cannot tolerate more than 12
per cent dehydration.)
One may summarize by saying that by a combination of behavior
and physiology mammals can successfully occupy all but the most
extreme environments on earth without anything more than quanti-
tative shifts in the basic physiological pattern common to all. With
regard to dietary limits their performance is almost as impressive.
For example, ruminant artiodactyls can subsist largely on cellulose
because of the synthetic capacity of the bacterial flora of the rumen
(see Blaxter, 1954, for a discussion). (The existence of a fauna of
ruminant ungulates of course is an essential feature for the survival
of populations of many of the larger mammalian carnivores.) How-
88 G. A. BARTHOLOMEW
ever, a deficiency in critical trace elements in the soil apparently
represents an unbeatable physiological problem even to ruminants
(see Underwood, 1956, for a comprehensive review).
In several groups of mammals there is an additional capacity in
the repertory of environmentally relevant physiology, namely hiber-
nation, which allows smaller mammals to avoid for weeks or even
months climatic conditions too severe for them to cope with other-
wise (see Lyman and Chatfield, 1955, and Kayser, 1955, for recent
reviews). Prolonged periods of dormancy may occur at any season,
and the limited data presently available indicate that there is no
clear-cut difference between hibernation and estivation except the
environmental temperatures at which they occur (Bartholomew and
Cade, 1957). Daily periods of torpor are known among mammals
only in bats (Hock, 1951). Since hibernating mammals can arouse
spontaneously from their torpor, this capacity significantly extends
the range of environmental conditions which they can occupy, by
allowing them to confine their activity to the periods of the day or
the year when environmental conditions are favorable.
In addition to the capacities summarized above, many animals
including members of all classes of vertebrates have the capacity to
acclimate to environmental changes. This process of acclimation
allows the organism to accommodate its own range of control to a
w^ide range of physical conditions (see Bullock, 1955, for a review of
temperature compensation in poikilotherms).
Now that some of the relevant physiological capacities of verte-
brates have been surveyed very briefly, we may consider some ideas
concerning the relation of physiological tolerance to distribution. An
environmental factor that exceeds the limits of an animal's physio-
logical tolerance will control its distribution, but only at irregular
intervals in time and only on that perimeter of its range where the
factor is becoming extreme. On most of the boundaries of the
animal's range, the distributional limits are set by factors other than
simple physiological tolerance to the given environmental factor.
Familiar examples demonstrating that physiological incapacity to
meet environmental extremes is a factor in distributional control
only at isolated points in time and space are ofTered by the distribu-
tion of many species of vertebrates the ranges of which impinge on
the deserts of southwestern United States and northern Mexico. The
heat and aridity of the desert may actually limit the occurrence of
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 89
these species, but the desert comprises only part of the perimeter of
their ranges. On other parts of the perimeters, different factors must
be Hmiting.
Locally the distribution of many amphibians and reptiles is often
determined by aridity and temperature, but even these animals,
which are relatively dependent on climate, are able by their diurnal
and seasonal patterns of activity to select from apparently unfavor-
able physical circumstances the environmental conditions that do
not exceed their particular physiological tolerances. A result is that
while it is possible to reason from physiological data to the conditions
necessary for survival, it is not possible to reason from distributional
data to physiological capacities in the absence of detailed ecological
knowledge. Two examples may be cited. Thorson (1955) found that
the spade-footed toad, Scaphiopus hammondii, which occupies arid
regions, actually takes up water more slowly than do frogs from
more moist environments. In western Australia, frogs of the genus
Neohatrachiis frequent clay soils in which they cannot dig deep
burrows, whereas all species of the genus Heleioporus occupy friable
soil in which they can dig deep burrows. In the various species of
Neobatrachus, rate of water uptake increases with increasing aridity
of habitat, whereas in Heleioporus no such correlation can be demon-
strated. Presumably because of the microhabitat occupied during
estivation, rapidity of water uptake by Neobatrachus is of selective
importance, whereas for Heleioporus it is not selectively important
because the latter can dig deep enough to remain in damp soil where
rapid recovery from seasonal dessication is not critical (Bentley,
Lee, and Main, 1958).
The behavioral and physiological virtuosity of birds and mammals
makes the assignment of distributional control to environmental
extremes particularly difficult even after detailed studies of ecology
and local distribution, although some documented instances are
available in the literature. Opossums {Didelphis marsupialis) on the
northern limits of the species' distribution frequently suffer frostbite
of ears and tail and it may be that low temperatures per se are limit-
ing the northward spread of this species (see Hamilton, 1958, for a
discussion). At the opposite extreme, Alaska fur seals {Callorhinus
ursinus) become overheated at air temperatures only a few degrees
above 0° C, and death from heat prostration is frequent during the
commercial seal drives in the Pribilof Islands (Bartholomew and
90 G. A. BARTHOLOMEW
Wilke, 1956). The inability of these fur seals to prevent hyper-
thermia even at low air temperatures and low levels of solar radia-
tion may restrict the location of their breeding grounds to the Bering
Sea area. In contrast to such situations, wherein environmental
temperatures may be limiting, several species with very different
capacities for thermoregulation may successfully occupy the same
demanding environment. Brown Pelicans {Pelecanus occidentalis) ,
Great Blue Herons (Ardea herodias), and Western Gulls {Lams oc-
cidentalis), although having comparable thermoregulatory abilities
as adults, differ markedly in this respect while young. The first
two species are altricial; the third is precocial. Nevertheless all
three species nest successfully in unsheltered rookeries on the
desert islands of the Gulf of California, where they are subjected to
high air temperature, intense solar radiation, and extreme aridity.
They are able to breed despite these unfavorable physical conditions
and despite the profound differences in the capacity for temperature
regulation of the young, because the parents in the two precocial
species are extremely attentive and shade the nestlings during the
hours of intense heat, thus behaviorally compensating for the phys-
iological limitations of the young (Bartholomew and Dawson, 1954).
There can be no doubt that in areas such as the deserts, polar
regions, and high mountains where the environment is so demanding
that life is extremely difficult or impossible, physiological capacities
and tolerances limit the distribution of all groups of vertebrates.
But if one considers the continental areas as a whole and amphibia
and amniotes only, it becomes surprisingly difficult to find distribu-
tional limits that are set by physiological tolerance to physical
factors in the environment, except for those species that occupy one
of the unusually demanding environments such as mentioned above.
Ordinarily one species replaces another geographically. Such replace-
ment may of course on occasion be caused by physiological differ-
ences between the forms in question. The problems of sympatry and
competition are so complex, however, that in the absence of detailed
ecological and physiological knowledge, it seems unwise to assume
that in an area of contact or overlap each of a pair of geographically
complementary species is distributionally limited by its physiological
capacities. (See Dumas, 1956, for a carefully analyzed study of the
ecological and physiological responses to temperature and humidity
in two sympatric salamanders.) Although the topic has been one of
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 91
great interest and enormous theoretical importance since the time of
Darwin, a satisfactory evaluation of the role of competition in the
determination of distribution in general is obviously impossible at
the present time. As Hutchinson (1957, p. 419), has pointed out:
The only conclusion that one can draw at the present from the observa-
tions is that although animal communities appear qualitatively to be
constructed as if competition were regulating their structure, even in the
best studied cases there are nearly always difficulties and unexplored
possibilities. These difficulties suggest that if competition is determinative
it either acts intermittently ... or it is a more subtle process than has
been supposed.
My obvious reluctance to accept the direct role of physiology in
the determination of distribution of species probably needs defense
from the students of geographic variation in western North America,
where so many subspecies and species have been shown to have
limits that can be readily correlated with vegetation types and hence
indirectly with conditions of the physical environment. Since such
correlations are striking, it is often assumed that the distributional
limits are physiologically determined and that closely related species
or even subspecies are characterized by physiological differences.
There is little a priori reason to presume that animals are any less
variable in physiology than in morphology. Aside from coloration,
however, the minute morphological differences separating subspecies
or closely related species are not necessarily adaptive; similarly,
small physiological differences between closely related forms need
not be adaptive. If physiological differences are not adaptive, they
have little significance in determining the distribution of the forms
that possess them. Moreover, when one deals with the smallest
taxonomic categories — subspecies and obscurely delimited species —
and finds adaptive physiological differences, it is impossible to state
categorically whether or not these differences allow or follow
changes in distribution.
In view of the difficulty of demonstrating physiologically deter-
mined distributional limits and physiologically determined competi-
tive success in terrestrial vertebrates, it is reasonable to turn to
habitat selection and ecological tolerance for help in understanding
distribution. The correlation of habitat with both local and general
distribution is familiar to all field zoologists. It is a well-documented
fact that discontinuities of populations of terrestrial vertebrates
92 G. A. BARTHOLOMEW
coincide with changes in plant formations and soil types. These
discontinuities in distribution are related to active selection of
habitat by the animals involved. The ability to recognize and react
to factors in the environment, in such a manner that a given species
characteristically occupies a certain type of situation, is of course
referred to as habitat selection. As Miller (1956, p. 269) has pointed
out, "It does not imply selection of a habitat coincident with the
limits of environmental tolerance of the species but usually reaction
to some feature of the habitat far within those limits . . ." In areas
of great altitudinal relief such as western North America, many
clear-cut examples of the roles of habitat selection are available
(Miller, 1942). A spectacular instance is ofTered in the mountains of
northern Nicaragua where tropical rain forests interdigitate with
montane pine forests and each vegetational complex supports its
own characteristic avifauna, so that boreal species such as the Red
Crossbill (Loxia curvirostra) and tropical species such as the Jacamar
(Galbula ruficauda) may live only meters apart (T. R. Howell,
personal communication). Equally spectacular examples can be
cited for other groups. An unusually clear-cut example of the role of
the substratum in determining distribution is afforded by the fringe-
toed lizards of the iguanid genus Uma of the deserts of southwestern
America. Members of this genus occur only on aeolian sand, and the
changes in distribution of present day forms are determined by the
movements of the sand dunes that they occupy. Despite the total
dependence of this genus on a specific and limited physical habitat,
it occupies a broad altitudinal zone extending from 244 feet below
sea level to 3,700 feet above sea level (Norris, 1958).
SUMMARY AND CONCLUSIONS
It is the thesis of this paper that although the distribution of
many marine and aquatic organisms and many terrestrial inverte-
brates may be explicable in terms of physiological tolerances, no
such general statement can at present be made for terrestrial
vertebrates. The relationship between physiology and distribution
becomes progressively more obscure as one ascends the phylogenetic
series of vertebrates. The homeostatic mechanisms of terrestrial
vertebrates and the exceedingly complex relations which their
behavior allows them to maintain with the physical environment
make any assignment of causality between physiology and distribu-
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 93
tion extremely difficult. In the light of present knowledge it appears
more reasonable to look for the determinants of distribution of the
higher vertebrates in behavioral and ecological factors rather than
in terms of physiological tolerances. Available knowledge of physi-
ology helps to explain how a vertebrate can live where it does, but
rarely reveals why it does not occur beyond the observed limits of
its distribution. Physiological tolerances are permissive in that they
set the environmental parameters within which a species can occur.
By habitat choice, seasonal and daily patterns of activity, selection
of appropriate microhabitats, and acclimation, however, a species
with sufficient ecological tolerance can assemble the environmental
conditions necessary for survival and reproduction out of remarkably
unlikely arrays of environmental factors. Consequently, assignments
of distributional limits on the basis of assumptions about the physi-
ology of an animal are unrealistic. An animal's distribution represents
an integration of all the factors — behavioral, ecological, competitive,
reproductive, or other — that limit its existence as a population. It
is, therefore, unrewarding to attempt to explain distribution solely
in terms of the data presently available from physiological studies,
which because of the orientation of most physiologists, have been
neither sufficiently varied taxonomically, sufficiently intensive from
the standpoint of species and populations, nor often enough oriented
toward ecology to yield data adequate for the analysis of problems
as subtle as those involved in distribution.
REFERENCES
Andrewartha, H B., and L. C. Birch. 1954. The Distribution and Abun-
dance of Animals. University of Chicago Press, Chicago, 111.
Bartholomew, G. A., and T. J. Cade. 1956. Water consumption of house
finches. Condor, 58: 406-412.
. 1957. Temperature regulation, hibernation, and aestivation in the
little pocket mouse, Perognathiis longimembris. J. Mammal., 38: 60-72.
Bartholomew, G. A., and W. R. Dawson. 1953. Respiratory water loss in
some birds of southwestern United States. Physiol. Zo'dl., 26: 162-166.
. 1954. Temperature regulation in young pelicans, herons, and
gulls. Ecology, 35: 466-472.
-. 1958. Body temperatures in California and Gambel's quail.
Auk, 75: 150-156.
Bartholomew, G. A., T. R. Howell, and T. J. Cade. 1957. Torpidity in
the white-throated swift, anna hummingbird, and poor-will. Condor,
59: 145-155.
94 G. A. BARTHOLOMEW
Bartholomew, G. A., and F. Wilke. 1956. Body temperature in the
northern fur seal, Callorhiniis iirsinus. J. Mammal., 37: 327-337.
Bentley, P. J., A. K. Lee, and A. R. Main. 1958. Comparison of dehydra-
tion and hydration of two genera of frogs {Heleioporus and Neo-
batrachus) that live in areas of varying aridity. /. Exptl. Biol., 35:
677-684.
Blaxter, K. L. 1954. Ruminant nutrition. In Progress in the Physiology of
Farm Animals, Vol. 1, J. Hammond, Editor. Butterworths Scientific
Publications, London.
Bogert, C. M. 1949. Thermoregulation in reptiles, a factor in evolution.
Evolution, 3: 195-211.
Bullock, T. H. 1955. Compensation for temperature in the metabolism
and activity of poikilotherms. Biol. Revs., 30: 311-342.
Cohen, N. W. 1952. Comparative rates of dehydration and hydration in
some California salamanders. Ecology, 33: 462-479.
Cowles, R. B., and C. M. Bogert. 1944. A preliminary study of thermal
requirements of desert reptiles. Bull. Am. Museum Nat. Hist., 83:
261-296.
Dumas, P. C. 1956. The ecological relations of sympatry in Plethodon
dunni and Plethodon vehiculum. Ecology, 37: 484-495.
Hamilton, W. J. 1958. Life history and economic relations of the opossum
(Didelphis marsupialis virginiana) in New York State. Cornell
Univ. Agr. Expt. Sta., Memoir 354, pp. 3-48.
Hesse, R., W. C. Allee, and K. P. Schmidt. 1951. Ecological Animal
Geography. John Wiley & Sons, New York.
Hock, R. J. 1951. The metabolic rates and body temperatures of bats.
Biol. Bull, 101: 289-299.
Hutchinson, G. E. 1957. Concluding remarks. Cold Spring Harbor
Symposia Quant. Biol. 22: 415-427.
Irving, L., H. Krog, and M. Monson. 1955. The metabolism of some
Alaskan animals in winter and summer. Physiol. Zo'dl., 28: 173-185.
Kayser, C. 1955. Hibernation et hibernation artificielle. Revue de
Pathologic Generale et Comparee, No. 668, pp. 704-728.
Lack, D. 1954. The Natural Regulation of Animal Numbers. Oxford
University Press, London.
Lyman, C. P., and P. O. Chatfield. 1955. Physiology of hibernation in
mammals. Physiol. Revs., 35: 403-425.
Miller, A. H. 1942. Habitat selection among higher vertebrates and its
relation to intraspecific variation. Am. Naturalist, 76: 25-35.
. 1956. Ecologic factors that accelerate formation of races and
species of terrestrial vertebrates. Evolution, 10: 262-211 .
Norris, K. S. 1953. The ecology of the desert iguana Dipsosaurus
dorsalis. Ecology, 34: 265-287.
■ . 1958. The evolution and systematics of the iguanid genus Uma
and its relation to the evolution of other North American desert
reptiles. Bull. Am. Museum Nat. Hist., 114: 247-326.
DISTRIBUTION OF TERRESTRIAL VERTEBRATES 95
Pearson, O. P. 1954a. Habits of the lizard Liolaemus multiformis multi-
formis at high altitudes in southern Peru. Copeia (2): 111-116.
. 1954b. The daily energy requirements of a Wild Anna Humming-
bird. Condor, 56: 317-322.
Sawyer, W. H. 1956. The hormonal control of water and salt-electrolyte
metabolism with special reference to the Amphibia. Memoirs of the
Society for Endocrinology, No. 5., Part H, pp. 44-59.
Schmidt-Nielsen, K., and B. Schmidt-Nielsen. 1952. Water metabolism
of desert mammals. Physiol. Revs. 32: 135-166.
Schmidt-Nielsen, K., B. Schmidt-Nielsen, T. R. Houpt, and S. A. Jarnum.
1956. Water balance of the camel. Am. J. Physiol., 185: 185-194.
Schmidt-Nielsen, K., B. Schmidt-Nielsen, S. A. Jarnum, and T. R. Houpt.
1957. Body temperature of the camel and its relation to water
economy. Am. J. Physiol., 188: 103-112.
Scholander, P. F. 1955. Evolution of climatic adaptation in homeotherms.
Evolution, 9: 15-26.
Scholander, P. F., R. Hock, V. Walters, and L. Irving. 1950a. Adaptation
to cold in arctic and tropical mammals and birds in relation to body
temperature, insulation, and basal metabolic rate. Biol. Bull., 99:
259-271.
Scholander, P. F., R. Hock, V. Walters, F. Johnson, and L. Irving.
1950b. Heat regulation in some arctic and tropical mammals and
birds. Biol. Bull, 99: 237-258.
Thorson, T. B. 1955. The relationship of water economy to terrestrialism
in amphibians. Ecology, 36: 100-116.
. 1956. Adjustment of water loss in response to dessication in
amphibians. Copeia (4): 230-237.
Underwood, E. J. 1956. Trace Elements in Human and Animal Nutrition.
Academic Press, New York.
Wallgren, H. 1954. Energy metabolism of two species of the genus
Emberiza as correlated with distribution and migration. Acta Zool.
Fennica, 84: 1-110.
Evidence from Fossil Land Mammals on the
Origin and Affinities of the
Western Nearctic Fauna
Donald E. Savage
Museum of Paleontology, University of Calif or?iia,
Berkeley
1 he living nonmarine mammal fauna of Ne-
arctica is divided into 9 orders. These orders are subdivided into
about 28 families, about 100 genera, and a minimum of about 175
species. Approximately 75% of its orders, 60% of its families, 30%
of its genera, and 1-6% of its species are also found in the parts of
eastern Asia not occupied by tropical rain-forest. 100% of its orders,
about 65% of its families, 15% of its genera, and 3% of its species
occur in the parts of South America not occupied by tropical rain
forest. But these imposing numbers and their graphic demonstration
in Fig. 1 do not afford a satisfactory basis for concluding whether the
mammals of North America have closer affinity with those of eastern
Asia or with those of South America. The number of taxonomic
units in the living ensemble and the taxonomic percentage com-
parisons are figures that serve only as a crude index of the total
characteristics and affinities. Living mammals are but a small part
of the total land mammal fauna of this continent, for many more
lived here in the past, and the exterminated forms must also be
studied if our knowledge of origins and affinities is to be complete.
Beginning in force with Sclater, Darwin, Wallace, and Lydekker,
with tremendous propulsion from Osborn (1910) and Matthew
(1915), and with recent thorough refinement by Simpson (1947,
1953), we see the development of our present knowledge of mam-
malian biogeography, involving millions of years of history. Bio-
geography "must reckon with time as well as with space" (Hesse,
Allee, and Schmidt, 1937, 1951, p. 121). The attributes of a living
97
98
D. E. SAVAGE
fauna are to a large degree, then, reflections of the paleodynamics
of the fauna.
Our symposium theme. Origin and Affinity, involves certain rea-
soning and inferences, probably elementary to most zoogeographers,
TAXONOMIC COMPARISON OF LIVING LAND-MAMMAL FAUNAS
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ENDEMIC AUTOCHTHONS
Fig.
^1. A graphic demonstration of the approximate percentage of
living nonmarine mammalian taxonomic units of North America that are
also found in East Asia and in South America respectively.
certainly basic to paleozoogeographers, that can appropriately be
acknowledged and reviewed; for they form a philosophic back-
ground to our interpretations. It is fitting that a paleontologist
make the initial review of this background for he is particularly
concerned with the secularly developed phases in the evolution
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 99
and dispersal of organisms and with tiie ideas tiiat pertain thereto.
Certain criteria for determination of origin, as Hsted below, apply
particularly to the expanded field of paleozoogeography — a field
extending through millions of years.
Criteria for Determination of Origin
1. The earliest record of the group in the proposed area of origin. In
the absence of strong contradictory data, the district in which there is the
oldest, that is, earliest, occurrence of a group may be taken as the area of
origin. This procedure is elementary but essential, just as Steno's ride of
superposition is an essential in the science of stratigraphy (Steno's rule
states that in an undisturbed succession of sedimentary rocks, the oldest
formation is at the bottom, the youngest on top.) For example, on this
criterion, we may claim that Africa, perhaps the restricted area in North
Africa that was the southern coastal plain of the old Tethyan Seaway, was
the area of origination of the Proboscidea and that the armadillos origi-
nated in South America. These statements are based primarily on the
earliest records. In the case of the proboscideans such claims should be
employed only as exploratory models of interpretation because of the
paucity of the fossil record of early forms. Proboscideans may have
originated in central Asia, as some workers suggest, rather than in North
Africa; but if the record of late Eocene warm-temperate, savanna,
gallery-forest habitats in Asia becomes better known, yet does not pro-
duce remains of proboscideans or pre-proboscideans, the probability
becomes greater that Africa was indeed the homeland. Already the rela-
tively complete Eocene records in Europe and in the United States make
it probable that these territories were not centers of proboscidean origin.
In the case of the armadillos, contemporary and comparable environ-
ments are relatively well represented in North America, and we believe
that armadillos would have been found If they had lived here as early as
in South America.
2. An earlier record of progenitors in the proposed area of origination.
From the standpoint of paleontology, this, along with the first criterion, is
the ultimate basis for definition of center of origin and dispersal. These
criteria demonstrate that final statements as to the origin of any taxo-
nomlc unit of animals whose classification is supported by morphology of
geologically preservable parts must be based on the complete stratigraphic
record of the unit.
3. A group probably originated in the area wherein It has greatest
taxonomic differentiation (see, also, Emerson's conclusion 13 (1952, p. 224).
Taxonomic differentiation is here taken as the best available Index of
general evolutionary differentiation.
This criterion Is based on the reasoning that with given equality of
opportunity to diversify, the group has had more time to adapt to the
various niches, hence has greater antiquity in the area of greatest diversi-
100 D. E. SAVAGE
fication. Mayr (1946) uses this criterion extensively; his example (p. 13)
of the lark family is illustrative: "The larks are a family of more than 70
species and are represented in all parts of the Old World. Only certain
subspecies of a single species occur in the New World. There can he no
shadow of doubt concerning the family's Old World origin" [italics are
mine]. Perhaps not in Mayr's example but in many similar statements,
such an approach may be very tenuous and often misleading unless bio-
stratigraphic, sedimentologic, mineralogic, and geochemical studies indi-
cate that the proposed center of origin was comparable in ecologic diver-
sity with the inferred non-origination areas.
The interpreted center of dispersal, as evidenced by the distribution
and case history of living forms, may be altogether different from the
center of origin, particularly in the bradytelic phyla. The environment of
origin for many groups of organisms has shifted across great distances
since their inception. See, for example, Chaney (1936, 1940), Axelrod (1952
and earlier papers), and Stebbins (1950, Chap. XIV).
A complication may arise also in the consideration of animal groups
that become less diversified in the later episodes of their phyletic history
for reasons that may not be apparent in the sedimentary record. The liv-
ing Didelphoidea (opossums) are most diversified and include possibly
the most advanced members in the Neotropical region, but all living
didelphoids show less morphological variation than the late Cretaceous
Nearctic forms that are presently considered members of the group^ Thus
we conclude that the Neotropics are an asylum of diversified didelphoids
and that these Neotropical forms had their ecologic counterparts in late
Cretaceous Nearctica. Moreover, we must look for the origin of the
didelphoids in sediments that are lower in the stratigraphic column than
the presently known fossil sites.
Finally, the third criterion is the more revealing for the smaller taxa.
Later diversification within an order, for example, may have little geo-
graphic relationship to the origin of the first and most primitive species
of the order.
4. Phyletic age of the group is important. Phyletically ancient forms,
groups that have changed relatively little (in hard parts, of course)
through a long interval of time, are frequently known from restricted
or from scattered, relict type occurrences. Pertinent examples may be
found in many living amphibians, reptiles, and invertebrates, and even
in some mammals. Living lemurids in Madagascar have close relatives
in the early Cenozoic deposits of North America and Europe. The South
American, Asiatic and African distribution of living hystricomorph ro-
dents may represent an unrecorded Paleocene transworld dispersal of a
primitive stock, as suggested by Landry (1957). There are many records
1 Only jaws and dentitions are known for the late Cretaceous forms, but greater size
range and greater diversity of tooth structure are clearly indicated. Paleomammalogists
infer, therefore, more diversified gross morphologies, diets, and habits in these early
types.
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 101
in the Cretaceous and early Cenozoic in the northern hemisphere of the
pleurodire turtles, which now live in the southern hemisphere. Gavials
now live in Asia, but are known from the Oligocene of South America
according to Langston (1953). Cryptobranchid amphibians live in eastern
North America and in eastern Asia, but they are represented by the
renowned Andrias scheuchzeri ("Homo dilmni testis") in the Miocene of
Switzerland (Schmidt, 1946, p. 149; Romer, 1945, p. 592). These little-
changing types are in various degrees characterized by fragmented or by
recessed representation of a once greater geographic range that was
established during an expanding phase of their dispersal history.
5. Vagility of the group must be considered. This factor adds im-
measurable complexity and uncertainty to the interpretation of the fossil
record. Migratory birds may, theoretically, become a part of the fossil
record at any resting point on their flyway. Rapidly dispersing land mam-
mals might be first trapped in the sediments at great distance from their
district of origin. These uncertainties tend to be overcome by an in-
creasing probability that correlates with an increasing paleontologic
sample. Several concordant examples lend an inference greater credence.
Darlington (1948) and Stebbins (1950, Chap. XIV) have dis-
cussed other approaches to interpretation of the origin and dis-
persal of organisms: numbers of animals and of taxonomic units;
size and continuity of geographic range; distribution of related, com-
peting, or associated groups. Size and continuity of geographic
range appear to comprise an especially useful neontologic criterion
for interpreting origin of the smaller taxa. A large and continuous
range tokens the origin area.
Thus to confirm an interpretation of origin for a group of animals,
we must first explore the diverse paleobiotopes for earliest oc-
currence. This documentation is fundamental to the historical
zoogeography of the phyla and is then enriched by the succeeding
criteria. If, then, an area contains the earliest record, shows a bio-
stratigraphic sequence from progenitors to the group concerned,
contains most differentiated subgroups, and exemplifies a large and
continuous group geographic range, it is probably the center of
origin and dispersal.
Matthew (1915) claimed that the more advanced and progressive
members of a group should be nearer the center of origin because
evolution was more progressive at this point. He also concluded that
the less advanced members tend to disperse radially and will be
peripheral. Because of the known climatic changes through time in
Holarctica, and because of the concentration of primitive animal
102 D. E. SAVAGE
forms in the equatorial and southern hemisphere land areas, Mat-
thew decided that the Holarctic region has been the principal cen-
ter of evolution and dispersal of land vertebrates — that the southern
and tropical areas are refuges for primitive species. This thesis,
along with Matthew's erudition, had an overwhelming effect on
North America zoogeographers, as Myers (1938) pointed out. In
so far as non-mammalian vertebrates and land invertebrates are
concerned, Matthew's thesis has been strongly opposed by many
neontologic disciplines. Myers (1938, p. 351) believed that there
is no evidence for the North American origin of any of the South
American freshwater fishes. Schaeffer (1952, p. 231), however, as-
serted that centers of origin for the true freshwater fishes are un-
known but that some elements were present in South America by
the late Cretaceous. He concluded that Mesozoic freshwater fishes
suggest a dispersal relationship between South and North America
on the one hand, and between Africa and Eurasia on the other.
Darlington (1948, p. 110) concluded that the main center of evolu-
tion of dominant groups of freshwater fishes, amphibians, and
reptiles has been the tropical part of the Old World. Mayr (1946)
reemphasized that the classic zoogeographic terms such as Holarctic
and Nearctic cannot be applied usefully to the historical zoogeog-
graphy of birds. He believes that such terms add nothing, in the
geographic sense, to the meaning of standard geographic names for
the areas involved. And he proposes Pantropical, Panboreal, Old
World, North American, Pan-American and South American cen-
ters for avian origin and dispersal. Conclusions opposing Matthew's
generalizations are equally numerous in the literature of nonmarine
invertebrates, but Emerson (1952) believed that termite history
is in essential accord. Much of the opposing viewpoint stemmed
from Matthew's rationalization that the more progressive species
develop in an area of secularly changing climate — that the warm,
humid swamp and forest environments promote a "relatively slug-
ish life." Some of the contradictory statements have been weakened
by too great a dependence on the natural and organic phenomena
of the presently arranged and restricted climatic belts. Much of
Darlington's contention that the Old World Tropics were the main
center of evolution for cold-blooded vertebrates, for example, is
based on the knowledge "that the tropical part of the Old World
is the largest favorable area for existence of cold-blooded life. ..."
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 103
[italics are mine], and on the misconception that north temperate to
tropical climatic zones have not shifted much during the Cenozoic.
It has been effectively demonstrated that there was a tremendously
greater latitudinal expanse of tropical, subtropical, and warm-
temperate climates during the late Mesozoic and early Cenozoic
interval when many of the now surviving orders and families and
some of the genera of animals were actually beginning; even though
the orientation of climatic belts was similar to the present.
Holarctica, although defined originally by the fauna living in the
present temperate and frigid climates, means much more than the
extant north temperate frigid region. When visualized through the
span of its geochronologic age, most of Holarctica was tropical and
subtropical throughout the first two-thirds of mammalian history.
Perhaps the inception date for Holarctica should be specified as the
time when oceanic and continental segments of the earth's crust
were first arranged roughly as at present, whenever that might
have been. I can see no utility for the term prior to the time of
abundant land life, however, and probably not before the "Age" of
endotherms. To the paleomammalogist, Holarctic is a shorthand
term to signify: (1) the fauna of the northern world continent;
(2) the northern world continent, characterized by its fauna through
the geochronologic age of the fauna; or just (3) the world continent
of North Africa, Eurasia, and North America through a geochrono-
logic interval. The term is therefore, a generalization, involving
geography, organisms, and time duration, with varying emphasis on
these respective constituents. Holarctica, like fauna, flora, strati-
graphic zone, species, and many other terms in our technical dic-
tionaries is entrenched by usage and is not vitiated because it has
been used with differing connotations or because certain organisms
do not have a dispersal history that can be described most effectively
by using Holarctic and sister terms.
Many groups of mammals may have originated in tropical, sub-
tropical, or warm-temperate biotopes, whether in northern latitudes
or in the present "tropics." Entire orders of mammals may be auto-
chthonous and endemic to the warmer and more humid areas, prob-
ably for varied reasons. As examples we may take the Primates,
the Dermoptera, and the Chiroptera (with most exceptions). I sug-
gest to the other contributors in this symposium that, if a "tropical"
origin is proposed for a group of animals, they carefully specify
104 D. E. SAVAGE
whether "tropical" means past or present, for the geographic con-
notation is much different.
CHARACTER OF THE FOSSIL LAND MAMMAL RECORD
Mayr, Linsley, and Usinger (1953, pp. 14-15) have reemphasized
that the study of many living groups of animals has hardly begun.
If the knowledge of living groups is in its infancy, the knowledge of
fossil groups is embryonic; for we yet lack complete study series
in the fossil sample. Darwin (1859, end of Chap. X), remarking on
the poorness of the paleontological record, said: "... I look at the
geological record as a history of the world imperfectly kept, and
written in a changing dialect; of this history we possess the last
volume alone, relating only to two or three countries. Of this vol-
ume, only here and there a short chapter has been preserved; and
of each page, only here and there a few lines. Each word of the
slowly-changing language, more or less different in the successive
chapters, may represent the forms of life, which are entombed in our
consecutive formations, and which falsely appear to have been
abruptly introduced." Matthew (1915, 1939 edition, pp. 13-14)
noted: "We know more about fossil mammals in proportion to
their modern numbers than about any other of the larger groups of
land animals, yet the number of species of which we have any ade-
quate knowledge is but a minute fraction of the number which must
have lived since the class first came into existence." Even in a
thoroughly studied district such as Crazy Mountain Field of Mon-
tana, Simpson (1937, p. 69) found that 25% of the species in the
sample were known from only one specimen each. And new animals
are yet being discovered in the frequently prospected Chadron
formation of Nebraska (Cook, 1954). At the present time, and un-
doubtedly for a long time to come, we can claim little more than
did Darwin or Matthew. The total taxonomic diversity may be
usefully represented for some stratigraphic intervals, but only a
few fossil assemblages adequately portray the populations that they
represent.
Locations of the pre-Pleistocene land mammal localities of
Nearctica are shown on Fig. 2. The record of earliest mammals is
from two upper Jurassic localities, one in Wyoming and one in
Colorado. (Late Triassic representatives of the class are found in
Europe.) Fortunately the Wyoming site produced a splendid as-
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA
105
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sortment of jaws and teeth and is one of the best of the Mesozoic
mammalian assemblages (Simpson, 1929). The early Cretaceous
record, at the threshold of dichotomy between eutherian (placental)
and metatherian (marsupial) mammals, is limited to a few tantaliz-
ing scraps of bone, isolated teeth and jaw fragments from a site
in north Texas (Patterson, 1956). The later Cretaceous land mammal
localities — principally in Wyoming, Montana, and Alberta — indi-
cate at present a curiously undiversified aggregate of multituber-
culates, didelphoids, and generalized eutherians.
The Cenozoic mammals of North America inherited an array of
nonmarine environments that extended across the entire continent ;
for our emergent land mass has suffered only marginal inundation
through the last 70 million years. In the freshwater deposits of the
middle and southern latitudes, mammalian aggregates have been
uncovered that are delightfully complete and varied when compared
with earlier records, but they are woefully small as compared with
the obtainable living sample of the same area. With the exception
of the interesting Miocene and Pliocene faunas in Florida, the
fossil mammal sample of western North America must represent all
the Nearctic region. Very few pre-Pleistocene fossil mammal speci-
mens have yet been found east of the Mississippi River.
Paleocene forms, tokened by skulls, dentitions, and some com-
plete skeletons, have been collected in the present Rocky Mountain
province. A few materials have been discovered in California
(McKenna, 1955), and one jaw came from a deep well in Louisiana
(Simpson, 1932). The better and more varied Paleocene assemblages
are in New Mexico, Utah, Wyoming, and Montana.
Eocene mammalian local faunas extend from the West Coast into
the Rocky Mountain area and from British Columbia (Russell,
1954) to southwest Texas (Wilson et al., 1952), and possibly to
central Mexico (Fries, Hibbard, and Dunkle, 1955). A few frag-
ments are known from New Jersey (Wood et al., 1941, p. 31 ; Gazin,
1953, pp. 8, 34). The better and more diversified Eocene assemblages
are in the Rocky Mountain states and in California.
Oligocene mammals are known from sites in the central part of
western North America: from the northern Great Plains to Cali-
fornia, from southwestern Saskatchewan (Russell, 1940) to south-
western Texas (Stovall, 1948). Best Oligocene assemblages are from
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 107
Texas, from the world-famous White River group of the northern
Great Plains, from Montana, and from Saskatchewan.
Late Cenozoic assemblages are widely scattered through the
middle latitudes of western North America. Every western state
claims several local faunas representing the last 30 million years of
land mammal history on this continent. Pliocene Ncarctic mam-
malian assemblages have been discovered as far south as Honduras
(Olson and McGrew, 1941). Pleistocene localities would make a
dense, stippled pattern for many areas on the map of Fig. 2 and
have consequently been omitted. Some of the more important
Pleistocene localities in the West include stream and lake deposits
of the Great Plains and Texas, cave and shelter accumulations in
the Southwest and Mexico, "mucks" and gravels in Alaska, and
breas in California. This suite of samples forms the biostratigraphic
basis for conclusions as to the origin and affinities of land mammals
in western Nearctica.
SIGNIFICANCE OF FOSSIL LAND MAMMAL SAMPLES
Since at least the day of Madison Grant's (1904) essay on the
origin and relationships of the large mammals of North America,
such statements as the following have appeared in the literature:
. . . the poverty of animal life which lived in Y area . . . , or . . . in
the X beds of corresponding age, a similar but more limited fauna is
found. These statements, usually based on little more than pre-
liminary surface collecting in newly discovered fossiliferous areas,
should have been carefully qualified as pioneer generalizations, but
were not. The authors made no evaluation of the factors of ac-
cumulation, preservation, discovery, and collection; and the printed
conclusions, in light of present knowledge, are no more than facile
verbiage. It is no secret that paleontologists yet lack raw data as
to the density and relative numbers of individuals, population size,
species associations and the like in the once living biocenoses.
Surprisingly, the more common a given fossil is in an area, the more
likely that there is a poor census for the animal represented. Through
the years, the common forms have been kicked aside in the quest
for the "remarkably new" exhibition specimens or the perfect
study skeleton. Some collectors have been disproportionately in-
trigued with the remains of giants (alas, the lust for the mighty
108
D. E. SAVAGE
dinosaur!); others spurn the labor-consuming giants for micro-
sized remains; others collect only complete skulls or skeletons and
discard individuals represented by only fragmentary specimens.
OCHOtON^
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Fig. 3. Faunal analysis diagram of the quarry sample from McKay
Reservoir, Oregon. The divisions of the circle graph represent relative
abundance of the mammals indicated. The radial bar graph represents
the number of specimens per individual. The heavy concentric line in-
cludes genera assigned to the proximal community. Reproduced from
Shotwell (1955, p. 333).
Shotwell (1955) demonstrated, as in Fig. 3, that useful census
and ecological interpretations may be derived from a meticulously
collected fossil sample. Such a sample will be composed of all the
obtainable bones and bits of bones from a given site. Shotwell pro-
FOSSIL LAND MAMMALS AXD WESTERN NEARCTIC FAUNA 109
vided an objective basis for the evaluation of the numbers of in-
dividuals of each species in the sample and from this census inferred
the species whose ranges were more proximal or more distal to the
accumulation site. No doubt other interpretations of the data will
differ from Shotwell's, for, as Shotwell notes, many variables and
assumptions are involved, but a new method of inquiry has been
pioneered. And this approach to the significance of relative num-
bers of fossil remains at a given locality will make the formerly
indifferent collector think twice before destroying or leaving behind
the identifiable fragments.
The taxonomic composition of quarry samples may differ sig-
nificantly from samples made up of specimens picked up only on
the surface of a fossil-bearing stratum. Simpson (1937) noted the
differences between two such samples in the Paleocene of Montana
and concluded that the apparent differences probably represented
two facies of the fauna. In a footnote (p. 52) he remarked: "Correla-
tions of faunal types and collecting methods are real but indirect.
Flood-plain deposition and facies would not normally result in
concentration of fossils sufficient to permit profitable quarrying."
Van Houten (1945) concluded that in the continental sediments of
late Paleocene and early Eocene ages in the Rocky Mountain region
there is a definite relationship between mamalian faunal facies
and the lithofacies. He found (p. 444) that the arboreal forest
faunal facies [micro-mammals] are concentrated in local pockets of
the drab grayish sediments, whereas the large ungulates and
creodont carnivores, representing savanna floodplain habitats, are
sparsely scattered throughout the red-banded varicolored sediments.
Here the micro-mammal facies were obtained from quarries and the
mega-mammal facies from surface collecting. A comparison of a
quarry sample with the surface discoveries from one formation
shows taxonomic and census differences comparable to those in the
lithofacies studied by Simpson and by Van Houten. Simpson (1935,
p. 4) showed the abundance of different species in the Tiffany fauna,
late Paleocene, from the San Jose formation of southwestern Colo-
rado. In his chart, here slightly modified (Fig. 4) following later
work by Simpson, the numbers of micro-mammals from the Mason
Pocket faunule, contained in less than a cubic yard of matrix, are
compared with the known surface discoveries on the upper Paleocene
part of the San Jose formation. In this comparison only one species.
110 D. E. SAVAGE
Plesiadapis gidleyi, among the eiglit known from the San Jose sur-
face and among the eleven from the pocket, is common to the two
assemblages. The larger animals such as Phenacodus and Periptychus
are known only from surface finds; so that one's concept of faunal
composition would be completely different if only the surface ma-
MASON POCKET ELSEWHERE
MULTITUBERCULATA
PTILODONTIDAE
Ectypodus musculus 12+
MARSUPIALIA
DIDELPHIDAE
Peradecfes elegans 20
INSECTIVORA
LEPTICTIDAE
Leptacodon tener 2
Xenacodon mutilatus I
PICRODONTIDAE
Zanycteris paleocena I
PRIMATES
PLESIADAPIDAE
Plesiadapis gidleyi 20+ I
?APATEMYIDAE
Labidolemur soricoides 2
CARPOLESTIDAE
Carpodapfes aulacodon I
ANAPTOMORPHIDAE
Navajovius kohlhaasae 3
PHENACOLEMURIDAE
Phenacolemur frugivorus 7
CARNIVORA
ARCTOCYONIDAE
Chriacus sp. • • I
Thryptacodon oust rails I
MESONYCHIDAE
?Dissacus sp. . . I
CONDYLARTHRA
PHENACODONTIDAE
Phenacodus grangeri • • 9
Phenacodus matthewi • • \
Phenacodus gidleyi • • I
Phenacodus sp. • • I
PERIPTYCHIDAE
Periptychus superstes • • 5
TOTALS 70+ 20
Fig. 4. Census of individuals of various land mammal species from
the Mason Pocket and from elsewhere in the San Jose formation, late
Paleocene, Colorado. Modified from Simpson (1935, p. 4).
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 111
terlal had been collected. Taxonomic and relative abundance differ-
ences may be the result of incomplete quarrying at the site of sur-
face discoveries (one jaw on the surface may indicate fifty at six
feet down !) , or lithofacies differences may indicate a complete bio-
facies change, as suggested by Simpson and by Van Houten. The
final confirmation of one or more of the various possibilities rests on
the completion of exhaustive quarrying with improved collecting
techniques in the areas where the variegated, red-banded formations
are exposed and where the sample is essentially surface pickup at
present.
During the last fifteen years several institutions in the midwestern
and western United States have been employing a screen -washing
technique for the recovery of small fossils. This technique calls for
the handling of tons of fosslliferous sediment. The sediment Is
washed through screen boxes. Available bodies of water are used,
whatever they may be: streams, lakes, stock tanks, or the ocean.
Fosslliferous matrix, frequently appearing quite barren on its surface
exposure, is quarried and shoveled into burlap bags for transport to
the washing site. Experience has shown that the transport distance
may be 20 miles or more before the method can be considered un-
profitable in terms of collecting expense. At the water, the matrix is
screen -washed, dried, and picked; and the number of specimens
recovered is often astounding when compared to standard quarrying
methods. During three summer seasons in the lower Eocene of north-
western Colorado and adjacent Wyoming, M. C. A^IcKenna and
colleagues of the University of California obtained about 20,000
individual specimens of teeth, jaws, and bones of ultra-small fossil
vertebrates. And these were taken from terrain that had been passed
over and considered unworthy for collecting by earlier workers.
Through a work period of five months, we have washed slightly more
than 30 tons of sandstone and have recovered 2,500 museum speci-
mens of fossil mammals from the late Cretaceous of Wyoming. This
is about one mammalian study specimen for each 24 pounds of
matrix. And these mammals are especially significant to the under-
standing of basic diversification (now largely conjectural) within
the Class Mammalia. Even greater numbers of specimens represent-
ing a combined assemblage of lizards, frogs, snakes, fishes, dinosaurs,
turtles, crocodiles, and birds were obtained from the depositional
association with the Cretaceous mammals. In both the Eocene and
112 D. E. SAVAGE
the Cretaceous, the first and principal sign of the richly fossiliferous
matrix was an accumulation on an ant hill of tiny teeth, gar scales,
reptile teeth, and the like.
These are admittedly the words of an enthusiast. Screen washing
is not the solution for all collecting problems, and it is efhcient only
as a mass production technique. Some matrices and some fossils are
not susceptible to this type of treatment. But the method is useful
in many areas, and it may be especially useful for census and ecology
studies in the varicolored flood-plain formations that have been pro-
claimed barren by previous workers.
The possible contrast in abundance of adaptive types between
samples from the drab gray quarry pockets and the varicolored
flood-plain deposits is also interesting. In the continental late Paleo-
ceneof the Rocky Mountains, Simpson (1935, 1937) and Van Houten
(1945) found that the small herbivores abound in the quarry samples
and that the large herbivores, carnivores, and carnivore-omnivores
are relatively abundant in the scattered surface finds. Combined
floral, faunal, and sedimentological data show that these late Paleo-
cene environments were in intermontane lowlands and were subject
to humid warm-temperate or subtropical climate (Knowlton, 1917,
1924; Berry, 1935; Bell, 1949). By contrast, work in the late Mio-
cene deposits in the Cuyama Badlands of southwestern California
shows quite difi"erent proportions of adaptive types. Figure 5 gives
the stratigraphic correlation between red-bed and gray-bed occur-
rences of land mammals within the Caliente formation in this area.
Present mapping and studies of the physical stratigraphy of the
district indicate that the red-bed and gray-bed mammal locations,
here assigned to the Barstovian (late Miocene) Mammalian Age,
are geochronologically contemporaneous. Figure 6, a preliminary
census of the Caliente formation mammals, is based on both surface
collecting and incomplete quarrying in both lithofacies. In this com-
parison it may be noted that the small insectivores and herbivores
(including rodents and rabbits) are relatively abundant in the red
beds, whereas large herbivores, such as camels, horses, and oreo-
donts, are the dominant element in the gray-bed faunule. The
Cuyama example, therefore, suggests a quite different relationship
between lithofacies and mammalian adaptive types. Combined
paleontological and geological evidence shows that the Cuyama
paleobiotope was in coastal intermontane valleys and was subject
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 113
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D. E. SAVAGE
BARSTOVIAN MAMMALS
IN THECALIENTE FORMATION
RED BEDS
GRAY BEDS
■ ! .!<.., .M« > ? .. ^ . a .. ^ , T . ,w, ., , .)
Fig. 6. Census of land mammal adaptive types in the late Miocene
Caliente formation of southwestern California, showing approximate
abundance of each type on a percentage bar graph for the red-bed facies
and the gray-bed facies respectively.
to probable temperate-mesic to xeric climatic conditions, depending
upon local topography (Axelrod, 1940, 1950; Dibblee, 1952 ; Durham,
1950; Schwade, 1954). But this comparison between the paleobio-
cenoses across western North America provides only tentative con-
clusions because:
1 . The compared faunas are dissimilar taxonomlcally.
2. There was a profound climatic and vegetative difference be-
tween the two areas.
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 115
3. Approximately 45 million years, a sufficient interval for great
evolution of morphologies and change of ecological-physiological
tolerances, elapsed between early Eocene and late Miocene.
4. There are possible subtle differences between the similar litho-
facies of the two areas. Similar lithofacies were not necessarily
formed under the same environmental conditions. The color differ-
ences in the Caliente formation may mean little more than differing
sediment-source, and both the red and the gray facies may have
been deposited in the same physical environment.
Detailed sedimentological studies have not yet been accomplished,
and much work lies ahead. Nevertheless, the example from Cuyama
suggests that conclusions as to relative abundance of taxonomic units
and adaptive types in certain lithologies are premature and may be
completely misleading, especially when based on samples collected
by techniques of disparate refinement.
HISTORY AND AFFINITIES OF THE ORDERS OF NEARCTIC
LAND MAMMALS
Earliest records of the class Mammalia are from the late Triassic
of England, but generalized reptilian progenitor stocks are known
from South Africa as well as in various Holarctic districts. There-
fore, on the basis of the stratigraphic record, the possibility of either
Holarctic or Paleotropic origin for the class Mammalia must be
conceded.
Pre-Paleocene land mammal faunas are so poorly known on most
continents that little can be determined as to intercontinental dis-
persal and affinities. From late Paleocene to the present, however,
the fauna of North America is clearly dominated by groups common
to many parts of Holarctica, especially such forms as shrews and
moles, rabbits and pikas, sciuromorph and myomorph rodents,
creodont and fissiped carnivores, condylarths, uintatheres pro-
boscideans, perissodactyls, and artiodactyls. All zoogeographers
know that the Nearctic Cenozolc mammalian fauna differs markedly
from the prototherian-metatherian fauna of Australasia and is only
slightly less distinct from the pre- Pleistocene metathere-edentate-
archaic ungulate assemblage of South America.
Nearctica is dominant in the recorded range and dispersal of the
33 recognized orders of land mammals (Fig. 7), but only 9 orders
(with 27 families) are represented here by living forms: Marsupialia
116 D. E. SAVAGE
(1 family) ; Insectivora (2 families) ; Primates (1 family) ; Chiroptera
(3 families); Edentata (1 family); Carnivora (5 families); Lago-
morpha (2 families) ; Rodentia (8 families) ; Artiodactyla (4 families).
However, 14 additional orders were here during various intervals of
the Mesozoic and Cenozoic, but are now either extinct or survive on
other continents: Multituberculata (extinct); Triconodonta (ex-
tinct) ; Docodonta (extinct) ; Pantotheria (extinct) ; Symmetrodonta
(extinct); Dermoptera (now in the Paleotropics) ; Tillodontia (ex-
tinct); Taeniodonta (extinct); Condylarthra (extinct); Notoungu-
lata (extinct); Pantodonta (extinct); Dinocerata (extinct);
Proboscidea (now in the Paleotropics) ; Perissodactyla (now in the
Paleotropics, Palearctica, and Neogaea). Of the 23 orders of land
mammals recorded in Nearctica, 9 have earliest record here, and 6
have earliest record here and elsewhere. First let us consider the
possibility that Nearctica was the origin and dispersal center for
these 15 orders, following the criteria proposed in the first part of
this paper; then we may consider the possible Nearctic origin for
other orders. Center of origin or origin area, as here used, of course
means place where earliest and most primitive members appeared.
Orders with Earliest Record in North America
1. Multituberculata (extinct)
a. Earliest record in upper Jurassic of England and United States
b. A group of uncertain phylogenetic affinities
c. Possibly originated somewhere in Holarctica
2. Marsupialia
a. Earliest record in upper Cretaceous
b. Comparisons on the basis of jaws and characters of dentition
lead to conclusion that this group was derived ultimately from
the Jurassic mammalian radicle, the Pantotheria; but forms with
annectant morphologies are unknown
c. Possibly originated in North America, but comparable Cre-
taceous biocenoses are poorly known in Asia and are not yet
known on the other continents
3. Dermoptera ("flying lemurs")
a. Earliest record in upper Paleocene
b. Probably distinct since middle or early Paleocene derivation
from generalized unguiculate eutherian; intra-ordinal relation-
ships are uncertain
c. Possibly originated in North America, but poorly known in the
North American fossil record and unknown as fossils elsewhere
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA
117
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4. Chiroptera (bats)
a. Earliest record in Eocene of North America and Europe
b. Probable latest Mesozoic or Paleocene derivation from a
eutherian stock (Insectivora?)
c. Bat-like forms are reported from the late Paleocene of North
America, but the group is too poorly known to conjecture as to
center of origin
5. Primates
a. Earliest record in middle Paleocene
b. An early Paleocene or latest Cretaceous differentiation in the
radicle Eutheria
c. Possibly originated in North America, but mammal-bearing
deposits as old as the early North American records are not
known on the other continents
6. Tillodontia (extinct)
a. Earliest record in upper Paleocene
b. An early to middle Paleocene differentiation from unguiculate
(?) stock
c. Possibly originated in North America, but evidence inconclusive
7. Taeniodonta (extinct)
a. Earliest record in lower Paleocene
b. A probable late Cretaceous differentiation within the Eutheria
c. Entire record of this group is in Nearctica
8. Edentata
a. Earliest record in upper Paleocene
b. An early to middle Paleocene differentiation from unguiculate
stock
c. Probable Nearctic origination because the earliest forms known
lack dermal armor and have a less specialized skeleton; but early
and middle Paleocene records of mammals are lacking in
Neogaea, the center of mid-Cenozoic evolutionary radiation of
the Edentata
9. Rodentia
a. Earliest record in upper Paleocene
b. Presumed origin from early or middle Paleocene unguiculate
stock, but annectents are completely unknown
c. Possibly originated in Nearctica, probably in Holarctica, but
evidence is inconclusive
10. Carnivora
a. Earliest record in lower Paleocene
b. Probably derived from a late Cretaceous eutherian group that
has been referred to the Insectivora or is not yet recorded;
possibly became a discrete group before the end of the Mesozoic
c. Probably of Holarctic origin, possibly in Palearctica
11. Condylarthra (extinct)
a. Earliest record in lower Paleocene
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 119
b. A horizontally classified group in which subdivisions are pre-
sumably derived from a ferungulate stock; some of the families
are a probable late Cretaceous differentiation
c. Most of the families (Hyopsodontidae, Phenacodontidae, and
Periptychidae) may have originated in North America, although
some paleomammalogists would propose origin elsewhere because
of the "sudden" appearance of differentiated groups in the
lower Paleocene here. Didolodontidae, as presently recognized,
appear to have a South American history, but are only slightly
divergent from phenacodonts (McKenna, 1956). Meniscotheri-
idae might have originated in Palearctica
12. Pantodonta (extinct)
a. Earliest record in middle Paleocene
b. An early unique differentiation within the Eutheria, possibly a
derivative of the ferungulate radicle but annectants with earlier
eutherians unknown
c. Probably of Holarctic origin
13. Dinocerata (uintatheres, extinct)
a. Earliest record in upper Paleocene of North America and Asia
b. Unique giants of uncertain phyletic origin within the Eutheria,
possibly derived from a ferungulate stock
c. Probably of Holarctic origin
14. Perissodactyla (horses, tapirs, rhinos)
a. Earliest record in lower Eocene of North America and Europe
b. Probably derived from advanced phenacodontid condylarths of
the type seen in the middle and late Paleocene of North America
c. Possibly originated in North America but the pre-perissodactyl
record is poorly known in Eurasia
15. Artiodactyla (pigs, deer, bovids)
a. Earliest record in lower Eocene of North America and Europe.
b. Probably derived from a generalized eutherian group of Paleocene
c. Probably of Holarctic origin, possibly of Paleotropic origin
Eight orders of mammals known in North America have earlier
records elsewhere: Triconodonta, Docodonta, Symmetrodonta,
Pantotheria, Insectivora, Lagomorpha, Proboscidea, and Notoungu-
lata. On the basis of prospecting and collecting data for North
America these orders may be divided into two groups: those that
may have a yet unknown earlier record in North America and those
that more probably do not have an earlier record in North America.
The lagomorph, proboscidean, and notoungulate beds of this con-
tinent are underlain by relatively well-explored mammal-bearing
strata; hence, these orders fall into the second group. The other
orders, all with earliest record in the Mesozoic, may be included in
120 D. E. SAVAGE
the first group, and it is pointless to guess as to an origin area, even
an area of continental size.
The remaining orders, not presently recognized in the Nearctic
record, can be discussed briefly.
1. Monotremata, as Patterson (1956, p. 100) has suggested, may
be related to forms that are being uncovered in the late Triassic of
England. This Mesozoic group (Docodonta Kretzoi, fide Patterson)
has representatives in the late Jurassic of North America.
2. Pholidota, Embrithopoda, Hyracoidea, and Tubulidentata
have no presently recognizable North American affinities. The rela-
tionships between hyracoids and the Holarctic, early Cenozoic
meniscothere condylarths are yet to be studied thoroughly. The
affinity of Tubulodon Jepsen from the early Eocene of North America
with the Tubulidentata is disputed (Jepsen, 1932; Colbert, 1941).
More fossil material referable to Tubidodon is badly needed.
In summary, the evidence appears strongest for Nearctic origin of
the marsupials, edentates, tillodonts, taeniodonts, perissodactyls,
dermopterans, primates, and rodents. For none of these groups,
however, is the evidence compulsory. Figure 7 also demonstrates
that late Paleocene through Eocene was the time when most of the
modern orders of mammals arose.
HISTORY AND AFFINITIES OF THE MINOR
TAXONOMIC GROUPS
Simpson (1947) so meticulously covered the evidence for origin
and dispersal direction of families and certain lesser taxa of North
American mammals that it would be superfluous to do more than
summarize his conclusions. Figure 8, showing possible origins, is
presented with the belief that most of the participants in this sym-
posium will be interested primarily in the families that are now
living. It is to be remembered that an individual subfamily, genus,
or species does not necessarily correspond with the origin and dis-
persion of its family ; for example :
1. Castor (beaver; Castoridae) evidently dispersed from Pale-
arctica to Nearctica; Miocene and middle Pliocene members of the
family dispersed in the opposite direction.
2. Didelphis (opossum; Didelphidae) and Tayassu (peccary;
Tayassuidae) appear to be Neotropical autochthons and Nearctica
is recently marginal to their expanded or expanding range.
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA
121
ORIGIN AND DISPERSAL OF LIVING
NEARCTIC MAMMALIAN FAMILIES'
REGION S
I 1
PALEARCTIC NEARCTIC
Didelphidae E -• L
Soricidae L -• ? L
Talpidae L ^L
Scalopodinae L -• ? L
Phyllostomatidae^ L -* ?—
Vespertilionidae^ \J "^ ^ L
Molossidae^ L' ? L
Hominidae L' ^ L
Dasypodidae^ L -*
Ochotonidae L ? *- L
Leporidae L *- L
Aplodontidae E -■ L
Sciuridae L -• ? L
Geomyidae^ L
Heteromyidae^ L
Castor idae L •" L
Cricetidae L "?" L
Microtinae L -• ? L
Muridoe^ L ■ L
Zapodidae L ^ L
Zapodinae L -< ? L
Erethizonfidae^ L -•
Canidae L ^?— L
Ursidae L ^ L
Procyonidae L ^?-" L
Mustelidae L ? ^ L
Felidae L ?- ^L
Toyassuidae E ^?-* L
Cervidae L ? ^L
Bovidae L *- L
Antilocapridae L
E-extinct
L-living
'-Based on Simpson(l947).
2-Not discussed by Simpson(l947).
'-Might have originated in the Paleotropic Region.
Fig. 8.
NEOTROPIC
— L
— L
-^L
-►L
— L
-*-L
■*■ L
— L
-^L
— L
— L
— L
A consideration of the time of origin of the 28 Hving Nearctic
famihes (Fig. 9), supports the generaHzation that the Oligocene or
possibly late Eocene-Oligocene, was the interval of inception of
modern families of mammals.'^
The living genera of Nearctica are either autochthonous or have
immigrated from Palearctica or from the Neotropics. Interpretation
2 Old World and South American families have a comparable geochronologic history.
122
D. E. SAVAGE
of the origin of these genera is shown in Table I. We may say that
the interval from Miocene into Pleistocene was the time when most
modern genera of land mammals arose.
Most species in the living Nearctic land mammal fauna are evi-
dently autochthonous. Probable exceptions are the transboreal
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MIOCENE
OLIGOCENE
EOCENE
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PALEOCENE
CRETACEOUS
TIME OF ORIGIN OF LIVING
NEARCTIC MAMMALIAN FAMILIES
Fig. 9.
forms, such as the moose, muskox, caribou, and polar bear; certain
"pan -American" forms, such as Eptesicus juscus (big brown bat),
Lasiurus borealis (red bat), Tadarida macrotis (big freetail bat), and
Eumops perotis (Western mastiff bat); and probable Neotropical
autochthons — Dasypus novemcinctus (armadillo) and Tayassu angu-
latus (peccary). A species list of land mammals from the Pleistocene
[including the Holocene of some workers] is given by Hibbard
(1956; in Flint, 1957, pp. 458-467). No taxonomist will recognize
exactly the same number of species as appear on the compilation by
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 123
Hiljbard; but it is beyond the intent of this paper to consider the
taxonomic problems of Pleistocene mammals or the effects of "split-
ting" or of "lumping" on the species Hsts of fossils. Hibbard's list
indicates the general stocks that were available for evolutionary
modification and zoogeographic change through the last few thou-
sand years. Many of the late Pleistocene animals are very similar in
hard part structures to the living species and have been so identified.
Very few of the middle or early Pleistocene forms have been referred
to living species.
Intercontinental faunal comparisons show probable trans-Hol-
arctic mammalian dispersal waves during most of the subepochs
from late Jurassic through late Pleistocene. Strongest evidence for
such dispersal is found in the late Jurassic, late Paleocene, early
Eocene, early Oligocene, middle to late Miocene, and middle Plio-
cene through late Pleistocene. Sharp peaks in the intercontinental
faunal resemblance curve indicate, as shown by Simpson (1947),
that these dispersals were discontinuous pulsations.
SUMMARY
1. A given area may be considered the most probable center of
origin of a group of animals if: (a) it contains the earliest record of
the group; (b) it contains the record of suitable progenitors; (c) it
contains greatest taxonomic differentiation within the group; (d) it
contains a large and continuous geographic range of the group.
2. The extant climatic belts and districts are poor geographic
indices for late Mesozoic-early Cenozoic arrangements. Therefore,
to propose the Holarctic or Paleotropic or other regions as centers of
origin and dispersal for a given group of animals we must first
evaluate the climate and ecology of these regions at the time of
origin.
3. The fossil sample may now give a good picture of the taxonomic
diversity of once living mammals for some districts, but the study
of paleobiocenoses, based upon significant numbers of individuals,
is in its infancy.
4. The biostratigraphic record is not yet adequate to reveal pre-
cisely the districts of origin and directions of dispersal for many
groups of land mammals.
5. Useful census and ecological interpretations may be derived
from a meticulously collected fossil sample made up of all identi-
124
D. E. SAVAGE
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Spilogale Geomys
Conepatus Cratogeomys
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Taxidea Thomomys
Urocyon 0?iychomys
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Probable Old World
or Nearctic Origin
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tS
Palearctic
Origin
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Thalarctos?
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Lagurus
Mus?
Probable time
of Origin
c
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FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA
125
Didelphis?
Dasypus
^ ts ^ -S
o e S ^
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Aplodontia
Zapus
Napeozapus
Odocoileiis
Bassariscus Peromyscus
Vulpes
Marmota
Citellus
Perognathus
r»-.
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Mustela
Sciurus
•■s t? s; 1 s ^ s ^ §
Lutra?
Felis?
Ochotona
Tadarida?
Rattus
H
G
u
o
c
0)
U
1
Oligocene
to
Pliocene
o
u
in
O
o
126 D. E. SAVAGE
fiable bones and bone fragments. This statement is trite unless
considered in the Hght of the actual case history of fossil vertebrate
collecting.
6. It is possible that there may be a fixed relationship between
mammalian faunal facies and the containing lithofacies, but pre-
vious generalizations as to this possibility were premature and will
have to be confirmed by exhaustive quarrying and by improved
collecting methods.
7. Screen washing is being applied to formations that earlier
workers believed to be unprofitable for recovery of fossils. The
abundance of small vertebrates in these formations indicates that
we may obtain large samples from seemingly barren, red, red-
banded, or varicolored flood-plain deposits.
8. Evidence is strongest for the Nearctic origin of Marsupialia,
Edentata, Tillodontia, Taeniodonta, Perissodactyla, Dermoptera,
Primates, and Rodentia, but the evidence is not conclusive. These
orders evidently differentiated within the Infraclass Eutheria in the
interval extending through late Cretaceous and Paleocene, roughly
85 to 65 million years ago.
9. About 35% of the living land mammal families of Nearctica
are autochthonous, about 7% endemic; most of the families origi-
nated in the interval late Eocene-Oligocene, approximately 50 to 35
million years ago,
10. About 70% of the modern Nearctic land mammal genera are
probably autochthonous; and as many as 15% were living as early
as late Miocene, 30% by middle Pliocene. All together, the genera
originated from about 15 million to possibly several thousand years
ago.
11. About 97% of the modern Nearctic land mammal species are
probable autochthons that originated in the interval, later Pleisto-
cene into Recent, possibly two or three hundred thousand years
ago to present.
REFERENCES
Axelrod, D. I. 1940. The Mint Canyon flora of southern California: a
preliminary statement. Am. J. Sci., 238: 577-585.
. 1950. Evolution of desert vegetation in western North America.
Carnegie Inst. Wash. Publ., 590: 215-306.
. 1952. Variables affecting the probabilities of dispersal in geologic
time. Bull. Am. Museum Nat. Hist., 99: 177-188.
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 127
Bell, W. A. 1949. Uppermost Cretaceous and Paleocene floras of western
Alberta. Bull. Geol. Surv. Canada, 13.
Berry, E. W. 1935. A preliminary contribution to the floras of the White-
mud and Ravenscrag formations. Mem. Geol. Surv. Canada, 182.
Chaney, R. W. 1936. Plant distribution as a guide to age determination.
/. Wash. Acad. Sci., 26: 313-324.
. 1940. Tertiary forests and continental history. Bull. Geol. Soc.
Am., 51: 469-488.
Colbert, E. H. 1941. A study of Orycteropus gaudryi from the Island of
Samos. Bull. Am. Museum Nat. Hist., 78: 305-351.
Cook, H. J. 1954. A remarkable new mammal from the Lower Chadron
of Nebraska. Am. Midland Naturalist, 52: 388-391.
Darlington, P. J., Jr. 1948. The geographical distribution of cold-blooded
vertebrates. Quart. Rev. Biol., 23: 1-26, 105-123.
Darwin, C. 1859. On the Origin of Species. John Murray, London.
Dibblee, T. W., Jr. 1952. Cuyama Valley and vicinity. Guidebook, Calif.
Oilfields. American Association Petroleum Geologists, Tulsa, Okla.,
pp. 82-84.
Durham, J. W. 1950. Cenozoic marine climates of the Pacific Coast. Bull.
Geol. Soc. Am., 61: 1243-1264.
Emerson, A. E. 1952. The biogeography of termites. Bull. Am. Museum
Nat. Hist., 99: 217-225.
Flint, R. F. 1957. Glacial and Pleistocene Geology. Wiley, New York.
Fries, C, C. W. Hibbard, and D. H. Dunkle. 1955. Early Cenozoic ver-
tebrates in the red conglomerate at Guanajuato, Mexico. Smith-
sonian Inst. Afisc. Collections, 123: 1-25.
Gazin, C. L. 1953. The Tillodontia: an early Tertiary order of mammals.
Smithsonian Misc. Collections, 121: 1-110.
Grant, M. 1904. The origin and relationship of the large mammals of
North America. Rept. New York Zool. Soc, 8: 182-207.
Hesse, R., W. C. AUee, and K. P. Schmidt. 1937. Ecological Animal
Geography. Wiley, New York; 2nd edition, 1951,
Jepsen, G. L. 1932. Tubulodon taylori, a Wind River Eocene tubulidentate
from Wyoming. Proc. Am. Philos. Soc, 71: 255-274.
Knowlton, F. H. 1917. Fossil floras of the Vermejo and Raton formations
of Colorado and New Mexico. U. S. Geol. Surv. Prof. Paper, 101:
223-435.
. 1924. Flora of the Animas formation. U. S. Geol. Survey Prof.
Paper, 134: 71-98.
Landry, S. O., Jr. 1957. The interrelationships of the New and Old World
hystricomorph rodents. Univ. Calif. Publ. Zool., 56: 1-118.
Langston, W., Jr. 1953. Longirostrine crocodilians from the Tertiary of
South America. Bull. Geol. Soc. Am., 64: 1520 [Abstr.].
Matthew, W. D. 1915. Climate and Evolution. Special Publ. New York
Academy Science, 1939 edition.
128 D. E. SAVAGE
Mayr, E. 1946. History of North American bird fauna. Wilson Bull., 58:
3-41.
Mayr, E., E. G. Linsley, and R. L. Usinger. 1953. Methods and Principles
of Systematic Zoology. McGraw-Hill, New York.
McKenna, M. C. 1955. Paleocene mammal, Goler formation, Mojave
Desert, California. Bull. Am. Assoc. Petrol. Geologists, 39: 512-515.
. 1956. Survival of primitive notoungulates and condylarths into
the Miocene of Colombia. Am. J. Sci., 254: 736-743.
Myers, G. S. 1938. Fresh-water fishes and West Indian zoogeography.
Smithsonian Inst. Ann. Kept., 1937: 339-364.
Olson, E. C, and P. O. McGrew. 1941. Mammalian fauna from the
Pliocene of Honduras. Bull. Geol. Sac. Am., 52: 1219-1244.
Osborn, H. F. 1910. The Age of Mammals in Europe, Asia and North
America. Macmillan, New York.
Patterson, B. 1956. Early Cretaceous mammals and the evolution of
mammalian molar teeth. Fieldiana: Geology, 13: 1-101.
Romer, A. S. 1945. Vertebrate Paleontology, 2nd edition, University
Chicago Press, Chicago, 111.
Russell, L. S. 1940. Titanotheres from the lower Oligocene Cypress Hills
formation of Saskatchewan. Trans. Roy. Soc. Canada, 34: 89-100.
. 1954. Mammalian fauna of the Kishenehn formation, south-
eastern British Columbia. Ann. Kept. Natl. Museum Canada, 132:
92-111.
Schaeffer, B. 1952. The evidence of the fresh-water fishes. Bull. Am.
Museum Nat. Hist., 99: 227-254.
Schmidt, K. P. 1946. On the zoogeography of the Holarctic Region.
Copeia, 1946, no. 3: 144-152.
Schwade, I. T. 1954. Geology of Cuyama Valley and adjacent ranges, San
Luis Obispo, Santa Barbara, Kern, and Ventura Counties. Calif.
Div. Mines Bull., 170: Map Sheet 1.
Shotwell, J. A. 1955. An approach to the paleoecology of mammals.
Ecology, 36: 327-337.
Simpson, G. G. 1929. American Mesozoic Mammalia. Mem. Peabody
Mus., 3.
. 1932. A new Paleocene mammal from a deep well in Louisiana.
Proc. U. S. Natl. Musuem, 82: 1-4.
— . 1935. The Tiffany fauna, upper Paleocene. I. Multituberculata,
Insectivora, and PChiroptera. Am. Museum Novitates, 795: 1-19.
. 1937. The Fort Union of the Crazy Mountain Field, Montana and
its mammalian faunas. Bull. U. S. Natl. Museum, 169: 1-279.
■ — . 1947. Holarctic mammalian faunas and continental relationships
during the Cenozoic. Bull. Geol. Soc. Am., 58: 613-688.
1953. Evolution and Geography. Condon Lectures, Oregon State
System Higher Education.
Stebbins, G. L., Jr. 1950. Variation and Evolution in Plants. Columbia
University Press, New York.
FOSSIL LAND MAMMALS AND WESTERN NEARCTIC FAUNA 129
Stovall, J. W. 1948. Chadron vertebrate fossils from below the Rim Rock
of Presidio County, Texas. Am. J. Sci., 246: 78-95.
Van Houten, F. B. 1945. Review of latest Paleocene and early Eocene
mammalian faunas. /. Paleontol., 19: 421-461.
Wilson, J. A., R. A. Maxwell, J. T. Lonsdale, and J. H. Quinn. 1952. New
Paleocene and lower Eocene vertebrate localities, Big Bend National
Park, Texas. Rept. Invest. Bur. Econ. Geol. Texas, 14: 9.
Wood, H. E., R. W. Chaney, J. Clark, E. H. Colbert, G. L. Jepsen,
J. B. Reeside, Jr., and C. Stock. 1941. Nomenclature and correlation
of the North American continental Tertiary. Bull. Geol. Soc. Am.,
52: 1-48.
The History and Affinities
of the Recent Land Mammals
of Western North America
William H. Burt
Museum of Zoology, University of Michigan^
Ann Arbor
When we speak of the origin of a fauna or
of some component of a fauna we imply that a more or less definite
place and time is involved. If our present concept of evolutionary
process is correct, faunas or parts thereof do not arise de novo.
Instead, they constitute a continuum. How, then, without being
strictly arbitrary, can we reasonably designate a place and time as
a starting point in this continuum — a place and time for the origin —
when the fauna or taxon is merely changing from one complex to
another. Can we really talk about the origin of a fauna or a taxon
without going all the way back to the origin of life itself, which may
also have been a continuum? Would it not be more nearly accurate
to speak of a phase in the history of a fauna or a taxon? In mammals,
for example, we might speak of the reptilian-mammalian phase,
which must have persisted for some millions of years, then the
mammalian phase, which has continued to the present. Geolog-
ically speaking, we might designate a pre-Tertiary phase and a
Tertiary phase in mammalian history. In this way we would indi-
cate a gradual change, not an abrupt one. Part of our thinking,
perhaps, has been influenced by the great discontinuities in the
geologic record. These break the continuum in the fossil record and
give to the uninitiated the impression of great steps in evolution.
They make for easy categorizing, but the animals and plants were
living and evolving during these great intervals of time when,
in the history of land mammals, no terrestrial deposits were being
formed, and no record was left. We are apt to pass over these
unknown intervals of time and say, for example, that the mammals
131
132 W. II. BURT
appeared in abundance at the beginning of tlie Tertiary. What we
actually mean is that their fossil remains show up in abundance
first at the beginning of the Tertiary period. But, they must have
been abundant and diversified long before the first grain of sand was
deposited in what we now call Tertiary beds. The paleontologist
knows all this, but I fear that he sometimes inadvertently conveys
the wrong impression by the language he uses and the charts he
draws, stacking one representation of a geologic age, referring to
the deposits containing fossils, on top of another and not indicating
lapses of time between them.
Although the title of the present symposium contains the word
"origin" I have not used it in this paper for the reasons just given.
I believe it is more in keeping with the subject of the symposium to
call it "The history and affinities of the Recent land mammals of
western North America." There is precedence for this in W. B.
Scott's monumental work A History of Land Mammals in the
Western Hemisphere, published in 1913. But, whether we speak of
origins or histories, it is necessary first to establish space and time
limits, otherwise the discussion is somewhat meaningless. The area
about which I shall be concerned in North America is that segment
of the continent lying principally west of meridian 100° West and
north of parallel 30° North. In Asia, it is that area principally east
of meridian 100° East and north of parallel 30° North. In South
America, I consider the entire continent. These areas admittedly
are unequal, but each contains diversified ecological conditions,
and each is sufficiently large to give a good sample of the total
mammalian fauna. The time interval is from the beginning of the
Tertiary through the Recent. Bats and marine mammals are not
included in the following analysis. I shall be little concerned with
the fossil record since that was discussed in the preceding paper.
I should like, however, to point up a few criteria used by students
of Recent faunas in attempts to determine the so-called place of
origin of a group of animals. I would prefer to call this the area of
differentiation — where the group passed from one evolutionary
phase to another.
1. The Present Geographic Distribution of the Group Indicates
Its Origin, (a) Some have thought that the central .part of the
area now occupied may represent the area of "origin" (differenti-
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 133
ation) of the group. This may or may not be so. Here, it is important
to know what time interval is being considered and, also, the
taxonomic level of the group — species, genus, family, etc. We
know that faunas have shifted geographically in the past, and,
unless we have the fossil evidence we cannot prove that the faunal
element involved did not move in from some other locality. A good
example in the mammals, in the area under consideration, where
we do have a fossil record from the same general area now occupied
by the group, is the assemblage of pocket gophers, pocket mice,
and kangaroo rats, involving two closely related families as now
recognized by specialists, the Geomyidae and Heteromyidae.
These mammals are, and have been, primarily western North
American in their distribution, as indicated by the fossil record
and knowledge of Recent kinds (Fig. 4). This is true also of the
pronghorn. Family Antilocapridae. If we base our interpretation
solely on Recent kinds and their present geographic distribution
and use the criterion just set forth, we would be correct in saying
that the area of differentiation was in western North America.
But, if we were to use the same criterion for the camels, Family
Camelidae, we would be far wrong. None of the latter are now
found in North America where they had their great development
in Tertiary times and continued into the Quaternary.
(b) The periphery of the present range has been considered by
some as being the most likely place for differentiation of a group.
This might hold for some of the lesser categories, such as species,
but for the higher categories, camels, for example, we find the same
objections as we did in the preceding discussion. As a matter of
fact, any segment of a population of a species might have the
potential of evolving in a different direction from the parent stock
if a barrier is established to isolate it. This barrier need but stop or
sufficiently dilute the genetic interchange between populations.
Even in a continuous population over a relatively large area, the
segments at the extremes may be sufficiently isolated by distance
that they will evolve in different directions {Peromyscus maniculatus
is an example).
2. The Area of Present Greatest Abundance Is Likely the Place
Where Group Evolved. This theory assumes that the area where
optimum conditions prevail today was always so. It ignores the
134 W. H. BURT
possibility of climatic change and the accompanying changes in
flora. These changes, if they occurred, would have influenced not
only distribution patterns but also population densities.
3. The Area of Greatest Diver sificatioyi {at present) of the Group
Is Likely the Place Where It Evolved into Its Present Phase. Some
authors have thought that the area now supporting the greatest
number of species (of a genus) must be the area where the group
reached its present evolutionary phase; that far from the place
where they evolved, individuals of a species are less plastic and
less able to adapt to diversified conditions. However, this does not
necessarily follow. It is usual to find diversity in a group (a genus,
for example) in an area that supports many kinds of habitats,
where ecological conditions are diverse. If these diverse ecological
conditions have persisted over a long period of time in the same
area, it is conceivable that many of the lower categories and, given
enough time, the higher categories might have developed there.
But, especially for the larger categories, this is problematical.
They might or might not have evolved in the area.
4. The Area Where Individuals Show the Highest Development,
Are Least Primitive, Is Probably the Place of Differentiation of the
Group. This is in keeping with Matthew's hypothesis. It is more
likely to hold for the higher categories (families and orders) than
for the lower ones. Without the fossil record, the same objections
apply to this as to other hypotheses.
5. Ecological Tolerance. Some authors have held that if a
species can adapt to several kinds of habitat, if it is not confined to
narrow ecological conditions, it still maintains a certain plasticity
and some of its initial potential for adaptation. Therefore, this
area, where the species is adaptable, is likely to be at or near the
place where it evolved from its ancestral stock. This, of course,
need not be true.
These are some of the ideas that have been expressed by students
of Recent biota. (For others, and a critique of them, see Cain,
1944; Darlington, 1957, pp. 29-35). They are all indirect lines of
evidence, but they may be used to advantage where other evidence
is not available. If any one of the above criteria is used, it should
be applied with extreme caution, because it may or may not lead
to a true interpretation of the facts. Darlington (1957, p. 580)
goes so far as to state: "I doubt whether any existing animals tell
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 135
anything about more ancient times." But he does use present
situations to explain past events. It is my opinion that the only
indisputable evidence comes from the fossil record, but we can get
leads from present distributions and relationships. However, I
shall not dwell further on this subject here, but shall go directly
to my principal topic, that of the present affinities of our Recent
mammalian fauna.
When one attempts to evaluate, or designate, affinities of two
or more faunas, he must first indicate the criteria to be followed.
It might seem simplest to count the species or genera, or whatever
category is to be employed, apply a formula, and come up with a
measure indicating degree of taxonomic resemblance between two
or more faunas. This will give a quantitative measure and make it
possible for us to communicate our results to our fellow workers
without elaborate descriptive material. But, the source data are
subject to errors, as I shall point out later, and the errors, if they
exist, will influence the result. As in dealing with so many biological
problems, a certain amount of subjectivity must enter the picture,
and to reduce everything to numerical terms may be misleading —
or downright wrong. Many non-taxonomists, and some taxonomists,
I am sorry to report, think of species and subspecies of mammals
as discrete entities. When they look at a check list, or faunal list,
they assume that each name represents a distinct unit, and that all
names in the same category represent units of equal value. Nothing
could be farther from the truth. All the categories of mammals are
to some extent subjective. In addition, they have changed with
time. What was once a species may now be a genus or a family,
either through evolution of the animals, if enough time is involved,
or through changes in man's concepts. Let me give a couple of
examples that I cited in a previous paper (1954). These have noth-
ing to do with the evolution of mammals, but they do show the
evolution of man's ideas. In 1909, when Osgood revised the genus
Peromyscus, some twenty-eight named species in the literature
ended up as one (maniculatus) , when he had finished his study.
More recently, in 1951, Hall reduced what were listed as twenty-five
species of weasels in the literature to three. I think it is apparent
that if one were using numbers of species per se, in comparing
faunas, the results would be quite different if data were taken from
the 1908 literature or that of 1956. Yet, many biologists continue
136 W. H. BURT
to count names in a list and talce them at their face value. They then
formulate hypotheses on what they innocently, but erroneously,
think are substantial data.
These and other problems have confronted me in the preparation
of this paper, and I have found no good solution to them. I have
tried various formulas for taxonomic resemblance, and will discuss
some of these presently. However, no formula will give a correct
answer unless the basic data are accurate. If we must use a formula,
and this method has great popularity in biology today, I prefer
one that takes into account the entire faunas, not just the smaller
of two. The latter may be best for fossil faunas, as Simpson (1947)
seems to think, but for our purposes I believe there are better ones.
After counting the species and genera listed in the literature,
primarily in Miller and Kellogg (1955) for North America, Ellerman
and Morrison-Scott (1951) for Asia, and Cabrera and Yepes (1940)
for South America, I decided to use the genus as my category for
the application of the various formulas. I have also prepared a
chart in an attempt to show graphically the relationships of these
three faunas. Other authorities were also consulted, and when there
was disagreement on a generic name, I arbitrarily included or ex-
cluded the name as I thought best. The numbers used, therefore,
should be considered approximate. I then employed "taxonomic
intuition." With this system, I came up with similar, but somewhat
different results. Neither system is accurate, but they show the same
general trends which fit the concepts of every competent mammalo-
gist today. My objective here is to test different methods of indi-
cating taxonomic resemblance — to discover, if possible, how nearly
accurate they are and where they might be misleading. I shall
attempt to analyze some of these, but first I should like to indicate
some of the perplexing problems that confront one in this kind of
effort.
To begin with, our knowledge of the three faunas under con-
sideration is not equal, so our basic data are not equivalent, and
this in itself makes comparisons difficult. Our knowledge is best for
North America, but even here we have many names in the literature
that no doubt will be omitted from the books in another twenty-five
years or so. As a matter of fact, our total knowledge of any one kind
of mammal is inadequate to evaluate it properly in the whole
scheme of things.
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 137
Secondly, we have conservatives and liberals, or lumpers and
splitters, among students of Recent mammals. Ellerman and
Morrison-Scott (1951) tend to be conservative for genera and species
while Cabrera and Yepes (1940) are quite liberal with the number
of genera that they recognize. Miller and Kellogg (1955) include
the findings in the latest revision of each group, with no critical
analysis of their own, so their list is a mixture of conservatism and
liberalism. In some groups, such as the Grizzly Bears, the last
authors, following Merriam's 1918 revision, list no fewer than 69
species for North America. They also give the black bear different
generic rank (Euarctos) from the grizzly {Ursiis). In 1953, two years
before the list by Miller and Kellogg appeared, Erdbrink included
all the Recent bears in the one genus Ursus, and all the North
American species of the grizzly, along with those from Asia and
Europe, in the one species arctos. These two works represent extremes
in the evaluation of names. It must be frustrating to the non-
taxonomist to see two such treatments within two years by two
different authorities. It is also frustrating to the taxonomist who is
attempting to apply a formula for taxonomic resemblance between
North America and Asia.
Thirdly, and somewhat related to the two previous difficulties,
is the fact that some kinds are considered in the literature to be
conspecific or congeneric while others, probably just as closely
related, are not. Some examples of species that are now considered
by some, at least, to be conspecific for North America and Asia are:
a shrew {Sorex pacificus), the gray wolf {Cams lupus), Arctic fox
(Alopex lagopus), wolverine {Gulo gulo), two weasels (Mustela
erminea and M. ?iwalis), moose {Alces alces), a ground squirrel
(Citellus undulatus), and two voles {Microtiis oeconomus and
Clethrionomys rutilus). Such kinds as the red fox (Vulpes), marten
(Martes), river otter (Lutra), lynx {Lynx), lemmings {Dicrostonyx
and Lemmus), chipmunk {Eutamias), and several voles and shrews
are considered to be distinct species, at least in the literature.
In a case like this, the counting of names without some evaluation
may give a false impression.
A fourth problem, but not a difficult one, is what category to
use. If we simply count the species listed for western North America
and for northeastern Asia, we come up with about 229 and 160,
respectively. On the basis of species names, North America would
138
W. H. BURT
appear to have a larger fauna, 229 to 160, but if we consider genera,
it would have the smaller fauna, 68 to 93. South America, with
114 generic names, tops them all. But this is not as bad as it might
seem at first glance. Obviously, if we are comparing faunas which
are relatively close geographically, and there are no great barriers,
most of the genera will be common, so we should use a smaller
Fig. 1. Chart showing relationships of non-flying land mammals on
three continents. Number of genera is approximate. Shaded areas repre-
sent parts of total faunas. Formulas at bottom are for taxonomic
resemblance.
category such as the species. If we are comparing remote faunas
where few, if any, of the species are common, we must use a higher
category, the genus or family.
These are some of the items that one must consider when com-
paring faunas for resemblance. Now let us look at Fig. 1 and the
measures we get by using different formulas. Numbers of genera
listed in the literature are given in the left column and are plotted
to scale in the others. My intuition tells me that South America
has too many genera in the indigenous block, relative to North
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 139
America and Asia. However, I am of the opinion that the number
of common genera is near reaHty. The great variables, then, will
be found in iV — C for each fauna, in any of the formulas used here.
But, regardless of the formula used, the trend is the same for these
three faunas, and all seem to be indicative of the relationships. In
Simpson's formula, (C/Ni) X 100, if we compare western North
America with Asia and South America, N2 could vary from 69 to
infinity and the measure would be the same, 40 for western North
America and Asia; 1 1 for western North America and South America.
What his formula actually gives is the percentage of common
kinds in the smaller of the two faunas, regardless of the size of the
larger one. This formula is usable as far as it goes, but it is my
opinion that it should be applied in both directions to give the true
picture. This gives two measures and makes it more cumbersome to
use than a formula that takes into account the total of the faunas
to be compared and gives but one measure. Such a formula is the
middle one in Fig. 1, [C/(iVi + N^ - Q] X 100. In this formula,
C appears in both numerator and denominator, and the measure
obtained is the percentage of common kinds in the total of two
faunas. This formula works best if the two faunas being compared
are equal, or nearly so, in size. If they are very unequal in size,
and the smaller fauna is mostly common to the larger one, the result
obtained may be misleading.
The top formula, [2C/(iVi + N2)] X 100, where C appears only
in the numerator, gives a measure, different from the others, but
shows the same trend in the faunas here compared.
In the figure, you will note that twenty-seven genera are common
to North America and Asia (C = 27). Several genera have close
relatives on the two continents, but, because of a different name in
the lists, they will appear in that part of the fauna which is consid-
ered indigenous. Some of these for western North America are:
Scapanus (mole), Taxidea (badger), Tamiasciurus (red squirrel),
Glaucomys (flying squirrel), Phenacomys (vole), Sylvilagus (cotton-
tail), and Odocoileus (deer). These genera are given the same value,
on the indigenous side for North America, as Dipodomys (kangaroo
rat), Perognathus (pocket mouse), Thomomys (pocket gopher),
and Antilocapra (pronghorn). But, they are related, and fairly
closely, to their Asiatic counterparts, whereas kangaroo rats,
pocket mice, pocket gophers, and pronghorns are not. If we use
140 VV. H. BURT
a formula based strictly on names in the literature, these relation-
ships are obscured and given negative instead of positive weight.
In my subjective system, which presupposes a knowledge of the
group, these seven kinds would be added to C, to give it a value of
34, instead of 27. Other adjustments would be made in various
groups, either combining or separating them. With this system, I
ended up with over half of the mammal fauna of western North
America showing affinities with that of Asia, about 57 per cent.
I believe this is nearer reality than anything the formulas would
indicate. However, the results are not in a form that is easily
communicable to other workers. By using this arbitrary system
further, about 30 per cent, instead of 45 per cent, of the western
North American mammals are considered as indigenous. In com-
paring North and South America, I arrived at 13 per cent, instead
of 19 per cent, of the western North American mammals showing
affinities with those from South America. This is fairly close.
MOVEMENTS OF MAMMALS BETWEEN EURASIA AND
NORTH AMERICA
Faunal relationships of the nature just discussed, where two land
masses are now separated by water, indicate a movement of animals
from one land mass to the other in past times. That there was a
nearly continuous land connection from the beginning of the Ter-
tiary to Pleistocene time between what are now the North American
and Asiatic continents is well established. There is still doubt
concerning the directions of movements of many kinds of mammals.
This would be important to know, but it is not essential to the
present discussion (see Simpson, 1947, for a summary on these
connections and movements). But, a land connection is in itself
not sufficient for the transfer of non-flying terrestrial mammals,
unless it be a very short one which an animal might cross in a
single journey. The distance from Cape Prince of Wales to East
Cape, across what is now the Bering Strait, some 75 miles, might
conceivably have been crossed by some of the larger mammals
such as caribou, moose, elk, and bear, even though no vegetation
were present. For the smaller mammals, some of which are restricted
within fairly narrow limits to specific ecological conditions, I
think it most unlikely that they would, or could, make the crossing
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 141
without food and shelter. This principle was pointed out several
years ago by Scott (1913, p. 143) in the following statement.
In the case of lands newly raised above the sea and connecting formerly
separated areas, it is necessary that they should first be taken possession
of by vegetation, before they can become passable by animals, for the
migration of mammals from continent to continent is an entirely distinct
phenomenon from the annual migration of birds.
Not only the land bridge, but the abutments to it must possess
ecological conditions suitable for those kinds that are likely to make
the crossing (Simpson, 1947). Simpson {ibid., p. 685), no doubt
influenced by earlier workers such as Merriam (1894) and Scott
(1913), stressed the climate as being "Not the only, but probably
the most important, selective factor..." in the faunal interchanges
between Eurasia and North i\merica. Further, he stated that
"the migrants generally are those groups tolerant of relatively
cold climates," and thereby gave importance to the temperature
at the time of crossing. But, he did not rule out other ecological
factors. I am of the opinion that climatic conditions, as regards
movements of mammals over long periods of time, are important
in an indirect way, as they affect vegetation and soils, rather than
in a direct one. It is fairly well established that through Tertiary
times the climate was more moderate than at present (Emiliani,
1958). Even in the Pleistocene, the interglacial stages had fairly
moderate climates (Deevey, 1949). Temperature tolerance in
mammals is primarily physiological, and most of them can with-
stand great changes if supplied with food. It is true that those
mammals that live in cold-temperate climates, especially the large
mammals that live above the snow, are tolerant of greater fluctu-
ations in air temperature than are many of the tropical kinds.
Yet, there are several kinds that range through the tropics to the
colder regions today (mountain lion, Felis; river otter, Lutra;
weasel, Mustela; and others). Recent studies, on the bioclimate of
small mammals that live beneath the snow in winter in an Alaskan
taiga, show that the temperature at ground surface, where many of
the small mammals live, ranged through no more than 27°F from
summer to winter, whereas the air above the snow ranged through
152° F. The temperature where many of these small mammals
live rarely goes below + 20° F even in the most severe winter
142 W. H. BURT
(Pruitt, 1957). It is misleading to consider air temperatures in
relation to these forms. The microclimate in which they live is
the important factor.
The northern porcupine must have evolved a different physiology
from that of its tropical ancestors to endure the low temperatures
in parts of its present range, and this since Pliocene times when the
Panama land connection was made between North and South
America. Although the porcupine can den in a sheltered place, it
must expose itself to the elements when it is feeding. I suspect that
physiological evolution may proceed more rapidly than morpholog-
ical change, although I have no direct proof of this. However, I
think it not too far-fetched to postulate that physiological adjust-
ment to climate might have kept pace with changing temperatures
and that temperature per se was no direct selective mechanism
in the interchange of mammal kinds between Eurasia and North
America. In some kinds of burrowing mammals, type and depth of
soil might be the important selective agent (Hardy, 1945). An
analysis of the Recent mammalian fauna of western North America,
with these considerations in mind, should throw some light on the
general problem of what were or were not selective agents. Also,
we should get some idea of the relative times of the last crossings
made by each group. Not all mammals have evolved at the same
rate, but close relationships should indicate recent crossings and
distant relationships earlier crossings. We must first make one
assumption, and it seems a reasonable one, i.e., that the habits of
mammals have not changed markedly since the times when their
ancestors had the opportunity to cross the land bridge. If this
assumption is not valid, then we have no way of interpreting many
of the phenomena of the past. Also, to have had an interchange of
the kinds that are related and now living on the two continents we
demand a corridor with the following specifications: There must
have been soil and vegetation with a fairly continuous forest and
areas of open savanna country. The two types of vegetative cover
might or might not have been coexistent. These demands are in
conformity with modern interpretations of past climate and vege-
tation in the area of the approaches as well as of the land bridge
itself (see Darlington, 1957, for a summary of studies in this area).
In the following discussion of the various groups of mammals I
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA
143
have used the excellent summary of fossil evidence by Simpson
(1947).
LAND MAMMALS FOR WHICH LAND BRIDGE SERVED AS A
CORRIDOR
Moles (Family Talpidae). These animals must have required a
soil cover of the proper kind. This means also a vegetative cover
and soil organisms for food. Our western moles today range no
farther north than southern British Columbia. However, the eastern
representatives go well into Labrador. The present distribution,
Fig. 2. General distribution of the moles, Family Talpidae, of North
America. Late crossings of the Bering land bridge are not indicated.
144
VV. H. BURT
relationships, and the fossil record would indicate an early Tertiary
crossing. Late crossings are not indicated. This group has been on
the North American continent long enough to evolve into two genera
on the West Coast and three genera in eastern North America.
Fig. 3. General distribution of shrews of the genus Sorex in North
America. Late crossings of the Bering land bridge are indicated. The
genus occurs also in Eurasia (Table I).
A large area now separates the western and eastern kinds (Fig. 2).
In like manner the Eurasian moles have evolved into several genera,
all distinct from those of North America. Temperature probably
would not have been a factor in dispersal of moles, but soil type
would. Moles are able to survive in rather heavy soils as well as
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 145
lighter, friable types, but arid conditions, with accompanying light
soils and a paucity of soil organisms are not suitable for them.
Shrews (Family Soricidae). Present day shrews live in various
types of habitats and in various climatic zones (Fig. 3). With a
vegetative cover of any kind they would find easy passage. Both
early Tertiary and late passages are indicated by the fossil record
and present relationships.
Man (Family Hominidae). There is no problem here, even
without a land bridge man could have made the crossing.
Bears (Family Ursidae). There is no problem in getting bears
from one continent to the other. Polar bears, which are not strictly
terrestrial, are circumpolar in distribution today, and the other
bears on the two continents are closely related (the grizzlies are
considered to be of the same species by Erdbrink, 1953). Exchanges
probably continued through the period of the last connection.
Weasel-like mammals (Family Mustelidae). Fossil records in-
dicate an early Tertiary passage and Recent relationships and
distributions indicate late passages, particularly of the fisher,
marten, otter, wolverine, mink, and weasels. The fisher and marten
would indicate a forested bridge, the others might pass over open
or forested country. Temperature would not be a factor with these
animals. However, for some of the skunks (Mephitinae), particularly
those of the genus Conepatus, climatic zoning could have served as a
selective agent in late Tertiary and Pleistocene times. Mephitis
and Spilogale now live under temperature conditions that are
probably more severe than they were during much of the time that
the two continents were connected.
Dogs (Family Canidae). Because of the diversity of habitats
occupied by this group, we need not look for special conditions to
effect an interchange. Fossil records and present distributions and
relationships indicate exchanges from early Tertiary to the last
land connection.
Cats (Family Felidae). Members of this family are nearly
worldwide in distribution and occupy various habitats. Indications
are that they passed from one continent to another many times
from early Tertiary to Recent. Although some kinds are now
confined to the tropics and some to cold areas, others, including
Felis concolor, range through the different climatic zones.
146 W. H. BURT
Squirrels (Family Sciuridae). This is a diversified group with
many closely related kinds on the two land masses today. Partic-
ularly close, in the two areas, are the marmots (Marmota), ground
squirrels (Cilellus), chipmunks {Eutamias), tree squirrels (Sciurus),
and flying squirrels {Glaucomys in North America and Pteromys in
Eurasia). For the passage of the marmots and ground squirrels,
open savanna is required, but for the tree squirrels and flying
squirrels, there must have been a fairly continuous forest. Climate
and soil would have been influencing factors only as they affected
the vegetation. There must have been several crossings up to and
including the last land connections.
One group in this family of rodents, the prairie dogs (Cynomys),
apparently had their entire evolutionary history in North America.
They are inhabitants of short-grass areas and require deep soil
for their burrows. These conditions apparently did not prevail to
the northward and they never reached the land bridge.
Beaver (Family Castoridae). A forest, or cover of shrubs, and
fresh water would seem to be required here. Fossil evidence would
indicate an early Tertiary crossing. Present day relationships and
distributions indicate a late crossing also. It is possible that there were
several interchanges. Temperature would not have been a factor.
New World mice and voles (Family Cricetidae). This group is so
diversified that any type of vegetative cover would have sufficed.
The subfamily Cricetinae, long-tailed representatives, probably had a
fairly early ancestral crossing. Evidence of this is found in their
present distant relationships and in the fossil record. A Pleistocene
crossing is not indicated. However, the subfamily Microtinae now
has close relatives on the two continents (in some genera the same
species) so crossings must have persisted to the end of the last
land bridge. Climatic conditions would not afTect this group directly.
The vegetative cover postulated would suffice, be it forest or
savanna. Why the North American cricetids or the Old World
murids did not make the crossing is difiicult to explain. Some would
argue that because they are ecological homologues, competition
would keep the two groups separated. I am not convinced that
this is the answer. It is possible that each group had its evolutionary
history far to the south, fairly late, and that time was not sufficient
for them to reach the bridge before separation of the continents.
However, there is no good evidence of this.
Mountain beaver (Family Aplodontidae). The little information
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 147
we have on this group indicates a late Tertiary crossing from
North America to Asia. A rather heavy vegetative cover is required.
Jumping mice (Family Zapodidae). Conditions suitable for
the Microtinae would be suitable for this group. Late crossings
are indicated.
Pikas (Family Ochotonidae). The fossil record would indicate a
middle Tertiary crossing for this group, and present relationships
indicate late crossings also. The pika now lives in talus slopes near
timberline. For the first ancestral crossings, when climates were
more moderate, a change in the habits of these little lagomorphs is
called for. In the Pleistocene, environmental conditions suitable
to present day pikas would have been more likely.
Rabbits and hares (Family Leporidae). Either forest or savanna
would have been suitable for the crossing of these mammals. Climate
would not, in itself, have been a factor. Fossil evidence and present
relationships indicate early and late crossings.
Peccary (Family Tayassuidae). Indications are of an early
Tertiary crossing. The peccary was then restricted to the North
American (and later South American) continent from about middle
Tertiary on. Open or wooded areas would have been suitable for
the crossing.
Deer (Family Cervidae). From about middle Tertiary on,
members of this family probably crossed over the land bridge
several times. The elk, moose, and caribou now have close relatives
on the two land masses, an indication of late crossing. Most any
vegetative cover would have been suitable for the crossing over.
Bovines (Family Bovidae). The bison and big horn sheep both
have close relatives on the two continents, an indication of late
interchange. There is less certainty about the mountain goat
(Oreamnos). From present relationships with Old World antelopes,
the indication is that no late passages occurred.
It will be noted that the groups in this section required only
soil (moles) and a vegetative cover of savanna and forest (others)
for a suitable corridor. Temperatures were at no time (except pos-
sibly during the glacial stages in the Pleistocene) prohibitively low.
LAND MAMMALS FOR WHICH LAND BRIDGE APPARENTLY
DID NOT SERVE AS A CORRIDOR
Raccoons (Family Procyonidae). There is no indication of
intercontinental exchange since the evolutionary phase in which
148
W. H. BURT
Table I. Genera of Strictly Terrestrial, Non-Flying Mammals of
Temperate North America," 30 of Which Also Occur in Eurasia
Genus
Didelphis
Condylura
Scalopus
Parascalops
Scapanus
Neurotrichus
Sorex
Microsorex
Notiosorex
Cryptotis
Blarina
Ursus
Procyon
Nasua
Bassariscus
Martes
Mustela
Gulo
Lutra
Spilogale
Mephitis
Conepatus
Taxidea
Vulpes
Urocyon
Alopex
Canis
Felis
Lynx
Marmota
Citelliis
Cynomys
Tamias
Eutamias
Tamiasciurus
Sciurus
Glaucomys
Eurasia
X
X
X
X
X
X
X
X
X
X
X
Western
Eastern
North
North
America
America
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
" Designation to eastern or western North America is arbitrary in many instances.
One species of the genus Eutamias {minimus), for instance, occurs as far east as
Ontario, yet it is designated western because that is where all the other species are
found.
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA
149
Table I. — (Continued)
Western
Eastern
North
North
Genus
Eurasia
America
America
Thomomys
Geomys
Cratogeomys
Liomys
Perognathus
Dipodomys
Microdipodops
Castor
Onychomys
Reithrodontomys
Baiomys
Peromyscus
Oryzomys
Sigmodon
Neotoma
Synaptomys
Lemmiis
Dicrostonyx
Phenacomys
Clethrionomys
Microtus
Lagurus
Pitymys
Neofiber
Ondatra
Aplodontia
Zapus
Napaeozapus
Erethizon
Ochotona
Lepus
Sylvilagus
Pecari
Cervus
Odocoileus
Alces
Rangifer
Antilocapra
Bison
Ovibos
Ovis
Oreamnos
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
150 W. H. BURT
ancestral forms can first be recognized as raccoons (subfamily
Procyoninae). Raccoons proper probably had their early evolution
in tropical America. Climatic zoning might have been a selective
factor with these animals. However, they do range into southern
Canada today and it is difficult to see why they did not reach
Asia in late Tertiary or Pleistocene times. From fossil evidence we
may assume that the early ancestors passed over in Early Tertiary
times. The coati {Nasua) is a southern form that likely never did
get very far north. Climatic factors could have been important in
limiting the dispersal of this mammal.
Ringtails (Family Bassariscidae). The ringtail occupies the
same kind of situation as the coati (Nasua) discussed above.
Prairie dog (Family Sciuridae). The prairie dog was mentioned
earlier, but should be included in this section. It is an inhabitant
of short-grass areas, and ecological factors probably prevented it
from making the crossing. Although it now inhabits areas where
winter temperatures are low, it avoids the extreme cold by going
into hibernation.
Pocket gophers (Family Geomyidae). The present and what we
know of the past distribution of pocket gophers is primarily western
North American. A segment inhabits southeastern United States.
Their latitudinal range is from southern Canada to tropical America.
They are excellent diggers and can occupy the regions of heavy
soils as well as sandy loams. They apparently require soil moisture
sufficient to grow a good cover of vegetation. Normally, non-
forested areas are preferred. I suspect that a continuous, dense
forest would be a barrier to their dispersal — shallow, rocky soils
might serve the same purpose. Temperature probably would not
have prevented them from reaching the land bridge — there must
have been a barrier of forests or soil types, or both.
Kangaroo rats and pocket mice (Family Heteromyidae). Here
again, the fossil record indicates a strictly North American evolu-
tionary sequence. Soil type is probably the most important limiting
factor in the distribution of these rodents. Although partially
fossorial, they are weak diggers and, therefore, they require friable
soil. This kind of soil is to be found primarily in the arid and semi-
arid western part of North America (Fig. 4). Some of these animals,
particularly along the eastern border of their ranges, penetrate
areas of fairly heavy clay soils, but they prefer the lighter types.
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA
151
They tolerate temperatures from those found In Death Valley in
summer (about 120° F) to those of the northern Great Plains in
winter (about — 40° F). I cannot see that temperature played a
Fig. 4. General distribution of the genera Dipodomys (broken line
boundary) and Perognathus (soHd line boundary). All evidence indicates
that these mammals had their evolutionary history approximately within
their present range. There is no indication that they ever approached
the Bering land bridge.
major role in keeping these mammals on the North American
continent. I suspect it was soil type with the accompanying vege-
tation that prevented these rodents from approaching the land
connection.
Porcupine (Family Erethizontidae) . The porcupine did not
152 W. H. BURT
find its way to North America until after the Panama land connec-
tion with South America was established. It has now penetrated to
the far northern forests and no doubt would have made the crossing
had it not arrived too late. Time, I suspect, was the important
factor for the porcupine.
Pronghorn (Family Antilocapridae). As far as known, this is
strictly a North American product. Any intercontinental exchange
must have been by pre-pronghorn ancestors. Why did not this
animal reach Asia when other artiodactyls did? I suspect that the
answer is to be found in the ecology of the pronghorn. It is an
inhabitant of short-grass, semi-arid country. It is tolerant of low
as well as high temperatures. If the ancestors of pronghorns had
similar habitat preferences, we may assume that these short-grass
semi-arid conditions did not form a pathway on the approaches or
on the bridge itself. In this case, ecological conditions would serve
as a selective agent to prevent movement of the pronghorn.
Except for the coati and ringtail, these groups that apparently
did not cross the land bridge now inhabit areas of lower winter
temperatures than those that prevailed when the continents were
connected. General ecological conditions, soil and vegetation, I
suspect, were more important in restricting their northward move-
ments than was temperature. For the porcupine it was probably
the time element. The coati and ringtail conceivably could have been
restricted by low temperatures.
SUMMARY AND CONCLUSIONS
It is suggested that the term "origin" as applied generally to
faunas or taxa be replaced by the term "evolutionary phase."
Origin implies a fairly definite time and place for the beginning of a
fauna or taxon. But the evolutionary process is a continuum, and
a phase may represent a transition in time and space.
The difficulties in evaluating mammalian faunas in order to
designate affinities are pointed out. After a somewhat subjective
analysis, it is concluded that over one-half (57 per cent) of the
mammalian fauna of western North America shows affinities with
the fauna of Asia, about 13 per cent with that of South America,
and the remainder (30 per cent) may be considered as indigenous.
Present relationships indicate an exchange of faunas in the past.
Further, they indicate suitable habitats on land connections for
RECENT LAND MAMMALS OF WESTERN NORTH AMERICA 153
those kinds that made the crossing from one continent to the other.
The various groups of mammals of western North America are
analyzed for habitat selection, and general ecological conditions
are postulated for those that apparently made the crossing on the
Bering land bridge. Ecological conditions, soil and vegetation,
are considered to have been more important than climate, especially
temperature, in preventing certain kinds from making the crossing.
From the analysis of the mammalian fauna it is evident that
generalizations are dangerous. Each kind must be judged by itself.
What is applicable to one may not be to another. Still more hazard-
ous would be the application of rules derived from the study of
mammals to other classes of vertebrates or to invertebrates without
first understanding those groups.
REFERENCES
Burt, William H. 1954. The subspecies category in mammals. Syst. ZooL,
3 (3) : 99-104, 3 figs.
Cabrera, Angel, and Jose Yepes. 1940. Historia Natural Ediar.-Mamtferos
Slid- Americanos. Buenos Aires.
Cain, Stanley A. 1944. Foundations of Plant Geography. Harper and
Brothers, New York.
Darlington, Philip J. 1957. Zoogeography. John Wiley and Sons, New
York.
Deevey, Edward S., Jr. 1949. Biogeography of the Pleistocene. Bull.
Geol. Soc. Am., 60: 1315-1416.
Ellerman, J. R., and T. C. S. Morrison-Scott. 1951. Checklist of Palaearctic
and Indian mammals, 1758 to 1946. British Museum (Natural
History). London.
Emiliani, Cesare. 1958. Ancient temperatures. Sci. American, 198: 54-63.
Erdbrink, D. P. 1953. A Review of Fossil and Recent Bears of the Old
World, Pt. 2, pp. 321-597. Deventer-Drukkerij Jan de Lange.
Hall, E. Raymond. 1951. American Weasels. Univ. Kansas Pubis., Mus.
Nat. Hist., Vol. 4, pp. 1-466.
Hardy, Ross. 1945. The influence of types of soil upon the local distribu-
tion of some mammals in southwestern Utah. Ecol. Monographs
15: 71-108.
Merriam, C. Hart. 1894. Laws of temperature control of the geographic
distribution of terrestrial animals and plants. Natl. Geogr. Mag., 6:
229-238.
. 1918. Review of the grizzly and big brown bears of North
America. North Am. Fauna No. 41.
Miller, Gerrit S., Jr., and Remington Kellogg. 1955. List of North
American Recent mammals. U. S. Natl. Museum Bull. No. 205.
154 W. H. BURT
Osgood, W. H. 1909. Revision of the mice of the American genus Pero-
myscus. North Am. Fauna No. 28.
Pruitt, WilHam O., Jr. 1957. Observations on the biocHmate of some
taiga mammals. Arctic, 10: 131-138.
Scott, William B. 1913. A History of Land Mammals in the Western
Hemisphere. The Macmillan Company, New York.
Simpson, George Gaylord. 1947. Holarctic mammalian faunas and
continental relationships during the Cenozoic. Bull. Geol. Soc, 58:
613-688.
Origin and Affinities of the
Birds of Western North America
Alden H. Miller
Museum of Vertebrate Zoology,
University of California, Berkeley
In a well-illustrated talk, Dr. Miller presented
a critical and characteristically lucid analysis of the origin and
affinities of the birds of western North America, with special ref-
erence to those of Asiatic and South American origin. He compared
the eastern and western bird faunas of North America. One of the
points he stressed is the high incidence of endemism in the Califor-
nia fauna, conditioned in large part by the isolation of this fauna, by
the arid lands of the Great Basin and the Colorado Desert. Pressure
of other duties forestalled the preparation of his paper for publica-
tion. — Editor.
155
.7
Origin and Affinities of the Present Western North
American Reptile and Amphibian Fauna
Robert C. Stebbins
Museum of Vertebrate Zoology,
University of California, Berkeley
ABSTRACT
1 he present distribution of amphibians and
reptiles in western North America suggests a comparatively recent
(geologically speaking) trend toward widespread increasing aridity.
This trend has been especially potent in affecting the course of
evolution and distribution in the more sedentary, moisture-depend-
ent species. Examples are presented from among the major groups
of amphibians and reptiles.
The origin and affinities of the present salamander fauna of the
West are discussed.
157
Evolution of a Coast Range Corridor in California
and Its Effect on the Origin and Dispersal
of Living Amphibians and Reptiles
Frank E. Peabody^ and Jay M. Savage
Department of Zoology. University of California, Los
Angeles and Department of Biology, University of
Southern California, Los Angeles
1 hirty years ago, A. B. Howell wrote (1927,
p. 18) that "the fauna of the Pacific Coast of the United States
is of unusual interest, and presents many fascinating problems."
After three decades of intensive study, Howell's statement is no less
true, and many fascinating problems remain for the solving. How-
ever, in three decades there has accumulated a great mass of infor-
mation on the terrestrial fauna and flora of far western North Amer-
ica. Numerous investigators approaching the region from the varied
point of view of the zoologist, botanist, paleontologist, and geologist
have worked to a large degree independently. Perhaps the time is
right for significant syntheses culled from the data of biological
and physical disciplines.
Obviously, any synthesis must draw on the data of geology and
paleontology as well as on that from the modern biota. A most
important contribution of geology is that our western region is in
the throes of violent physical revolution in marked contrast with
long antecedent epochs of quiescence. Our modern biota exists in
what we and many others regard as an interglacial stage of the
Pleistocene epoch. A most important contribution of paleontology
is the clear evidence of marked southerly shifts of isotherms on a
continental scale culminating in the Pleistocene and integrated with
profound topographic changes affecting vast inland areas. While it
may be charged that the biologist has not sufficiently heeded these
1 Deceased June 27, 1058.
159
160 F. E. PEABODY AND J. M. SAVAGE
major contributions outside his immediate field, it is probably true
that the paleontologist and even the geologist may profit from a
closer look at biological data. It is the general purpose of the present
paper to demonstrate the advantages of a many-sided approach to
the problems of origin and dispersal of the biota of far western North
America. Attention is focused on the late Cenozoic era because the
historical events of that time are most completely documented and
because these events produced the major patterns of origin and
distribution of modern species.
Distribution diagrams are based on the treatise by Stebbins
(1954), with some emendations by the junior author. The distribu-
tion patterns are selected to illustrate best the relationship to the
coastal corridor. It is believed that the pattern of present distribu-
tion of species provides a general indication of the point of origin
with respect to the geologically recent corridor. Obviously, fluctua-
tions must have taken place in the past as at present, as witness the
northward advance of southern species and northward retreat of
boreal species which are presently being documented across North
America.
THE FOSSIL RECORD
Fossil remains of amphibians and reptiles are rare in North
America west of the Mississippi and extremely rare in the far west.
Some indication of the fact is afforded by the paucity of citations
from bibliographic sources. For the 41 -year period from 1913 to
1954, the journal Copeia, of the American Society of Ichthyologists
and Herpetologists, contains only four papers describing Pleistocene
reptiles, and only three papers on Pliocene reptiles (Reed, 1956).
The more complete coverage in the Camp bibliographies of verte-
brate paleontology over the 20-year period 1928-1948 includes ap-
proximately eleven papers on amphibians, none concerning far
western North America, and approximately sixteen papers on rep-
tiles, none concerning the far west (Camp et al., 1940-1953). More
current literature includes a few but important contributions, for
example, the description of the salamander, Paleotaricha, from the
Oligocene of Oregon (Van Frank, 1955), and contributions by
Bayard H. Brattstrom (particularly 1954, 1955) and Richard G.
Zweifel (1955, 1956) on the herpetofauna of the Tertiary and Pleisto-
cene. In general the described fossils older than the late Pleistocene
COAST RANGE CORRIDOR IN CALIFORNIA 161
are rare, isolated fragments. Cave and asphaltic deposits of the late
Pleistocene produce more remains, but nearly all are disarticulated
and easy to overlook in the quest for larger and more durable re-
mains of mammals and birds.
Current interests of paleontologists in the washing and sifting of
sediments for microfossils are greatly increasing the recovery of
herpetological remains. For example, students of the University of
California, Berkeley, have made large collections of small lizard
remains from Eocene and Cretaceous strata of Colorado and Wyo-
ming (Malcolm McKenna and Robert Estes, personal communica-
tion). However, a fossil amphibian, particularly a fossil urodele, will
continue to be a rare find for the paleontologist because of the an-
cient trend toward deossification in their skeleton and because bone
is a prime prerequisite for preservation. Fortunately, the fossil
record of amphibians is enhanced significantly by the discovery of
numerous, clear, and distinctive trackways of urodeles in Mio-
Pliocene sediments of the Sierra Nevada Mountains in California
(Peabody, 1940, 1954).
A general conclusion from a survey of the paleontology of the far
western herpetofauna is that considerable progress is to be expected
in the future as a result of new techniques and of heightened interest
in paleoherpetology. However, we cannot ever expect to approach
the relative completeness of the mammalian record, and discoveries
in the far west will continue to be infrequent. Also a necessary ad-
junct to paleontological studies will continue to be more detailed
osteological studies of living species.
The fossil record of the herpetofauna, admittedly deficient, is
complete enough to establish firmly some general considerations of
historical importance. Fossils from the Cenozoic of Europe and
North America clearly indicate great antiquity for most living
genera of salamanders. By the dawn of the Cenozoic the three
families of terrestrial salamanders, Salamandridae, Ambystomidae,
Plethodontidae, were evolved, and by the Miocene epoch living
genera of all urodeles were probably in existence. The most dramatic
and unusual evidence of modern families and genera comes from the
Mio-Pliocene trackways of the Sierra Nevada (Peabody, 1940) where
the genera Taricha, Batrachoseps, and a Dicamptodon-l'ike form
coexisted in association with a fossil flora described by Condit
(1944). These trackways and the Oligocene skeleton of Paleotaricha
162 F. E. PEABODY AND J. M. SAVAGE
from Oregon (Van Frank, 1955) clearly indicate an additional,
important conclusion. Before the end of the Miocene epoch the far
west possessed a salamander fauna distinct from those of eastern
North America and Asia. The fossil record suggests that the antiq-
uity of anuran development at the familial and generic levels was
similar to that of the urodeles. However, the anuran fauna of western
North America has not become as clearly differentiated from the
eastern fauna.
On a worldwide basis the antiquity of families and genera of
modern reptiles does not correspond to that of the amphibians, that
is, the rate of evolution has been faster. A general impression is that
whereas most modern families, for example, the Iguanidae and
Varanidae, were evolved before the beginning of the Cenozoic, the
majority of modern genera in all families originated in middle to
late Cenozoic. In any event, the fossil record has little to offer on
the origin of modern genera and families of reptiles in far western
North America.
The fossil record makes little contribution to the origin of modern
species of the herpetofauna generally. Our knowledge of specific
characteristics of modern skeletons, of representative herpetofaunas,
and of stratigraphic controls within the Quaternary epoch is much
too deficient. Historical insight of the paleontologist would suggest,
however, that in our far western area, physical events culminating
in the Pleistocene epoch provided abnormally strong stimuli to the
rate of evolution at the level of species and subspecies.
THE CALIFORNIA COAST RANGE CORRIDOR
Obviously the above account of purely paleontological contribu-
tions to the stated theme of the symposium are disappointing and
inadequate. With this fact all too apparent, the writers groped for a
more significant contribution in the form of a multi-directional
approach — essentially a new look at old data from geology, paleon- .
tology, and herpetology. The senior author has long been fascinated
by the classic rassenkreis of subspecies of Ensatina as ably described
by Stebbins (1949). Reflection on possible historic controls of the
sympatric association of Ejtsatina subspecies in southern California
suggested that somehow the physical history of California may re-
veal the vital causative factor — a possibility not entertained by
COAST RANGE CORRIDOR IN CALIFORNIA 163
Stebbins. Interest was stimulated by the discovery that southern
Cahfornia is an area of relatively high incidence of sympatry be-
tween closely related forms in the modern herpetofauna. While
searching for the explanation for this phenomenon of distribution,
the writers evolved the concept of a Pacific Coast Range corridor
culminating in the Pleistocene epoch, accompanied by collateral
physical changes and affecting directly the origin and distribution of
the modern herpetofauna. The concept is hopefully presented as a
useful adjunct to understanding of the problems of origin and dis-
persal of faunas of far western North America.
Evolution of a Coast Range corridor essentially involves the
Central Coast Ranges, consisting of western and eastern segments
and extending from San Francisco south to Santa Maria, and the
Southern Coast Ranges extending from the Santa Barbara region
through the Transverse Ranges. The corridor has important con-
nections on the south with the Sierra block and with the Peninsular
Ranges, both of which are genetically related to the Basin and Range
PRESENT EXTENT OF
FRANCISCAN SERIES
m GRANITIC BASEMENT
AND OLDER ROCKS
n POST-JURASSIC
SEDIMENTS
/v
Fig. 1. Lithologic provinces of California. The present Great Valley
and Central and Southern Coast Ranges are the site of extensive marine
deposition (to 50,000 ft. thick) from Cretaceous into early Pleistocene
time. (After Camp.)
164
F. E. PEABODY AND J. M. SAVAGE
Province of Nevada. The corridor is bordered on the west by the
ocean and on the east by a great structural depression, only re-
cently reclaimed from the sea by continental uplift.
The data of geology (Taliaferro, 1943; Eardley, 1951) supply
antecedent chapters in the formation of the corridor. Geomor-
phologic provinces of California (Fig. 1) show that the site of the
present corridor was dominated by a large geosyncline receiving
mainly marine deposits in the approximate position of the Great
Valley of California during most of the Cenozoic. Adjacent struc-
tural basins of marine deposition to the south contributed to the
limiting of the stable edge of the continent to a line running length-
wise through the middle of modern California. The area of the
corridor was an archipelago at best during most of the Cenozoic.
During the Miocene epoch the area of the future corridor was
essentially "wiped clean" of terrestrial organisms by maximum
flooding of marine waters (Fig. 2). Flooding was followed by ac-
celeration of orogeny in the Coast Range belt. The orogeny surged
to one peak in late Pliocene, affecting mainly the western part of
the Central Coast Ranges, and to a second peak in the Mid-Pleisto-
UPPER MIOCENE
PALEOGEOGRAPHY
r
Fig. 2. Late Miocene paleogeography of California, showing extensive
marine flooding in position of present Central and Southern Coast
Ranges. (After Camp.)
COAST RANGE CORRIDOR IN CALIFORNIA
165
cene, affecting the eastern part of the Central Coast Ranges and the
Southern Coast Ranges generally. The last surge is still in its
climactic phase as the present is a time of active orogeny. The mid-
Pleistocene orogeny is associated with the final disappearance of
Tertiary troughs of deposition and the foundering of considerable
segments of the Coast Ranges into the Pacific Ocean. Also, and of
particular importance to the corridor concept, a marked uplift of
PLIOCENE AND
LOWER PLEISTOCENE
PALEOGEOGRAPHY
Fig. 3. Pliocene and early Pleistocene paleogeography, showing archi-
pelagic nature of Coast Range region, and presence of strait connecting
Pacific with San Joaquin embayment. (After Eardley.)
epeirogenic proportions affected the continent generally and the
area of the corridor in particular following the peak of mid- Pleisto-
cene orogeny. (At present, dissected erosion surfaces exist at levels
of several thousand feet elevation in the San Gabriel Mountains.)
Volcanism appears to have occurred sparingly in the area of the
corridor and has contributed little to its crust,
Paleogeography of the Pliocene and early Pleistocene (Fig. 3)
suggests that the Central and Southern Coast Ranges constituted a
reasonably continuous land mass probably extending far northward
but separated at the southern end from the continent proper by a
wide strait. Distribution of terrestrial plant and mammalian locali-
ties (Fig. 4) of Pliocene and early Pleistocene age suggests that the
166
F. E. PEABODY AND J. M. SAVAGE
strait at the southern end of the future corridor opened directly
westward from the southern San Joaquin embayment. In view of
the many complexities of Coast Range geology it is difificult to
follow in detail the rapid geomorphic changes attending Coast Range
orogeny. However, the distribution of the modern herpetofauna in
California suggests strongly that there was an important marine
barrier in the position of the present Southern Coast Ranges, in fact
• PLANTS
o VERTEBRATES
Fig. 4. Distribution of terrestrial Pliocene and early Pleistocene
localities for plants and mammals suggestive of southern strait connect-
ing Pacific with San Joaquin embayment.
precisely coincident with the strait shown in Fig. 3. Also a con-
tinuity northwestward from the strait is indicated. The continuity
need not have been geographic but was almost certainly zoogeo-
graphic, allowing free access to northern species of the herpetofauna
but not to southern species. Paleobotanical data (Axelrod, 1957)
indicate that the marine strait was not a barrier to northward ex-
tensions of tropical and subtropical floras (Fig. 5). In terms of the
herpetofauna, it seems reasonable to conceive of a long peninsula
or a series of closely adjacent islands forming a zoogeographic unit
extending southward from the San Francisco region and including
the Santa Lucia basement rocks as a relatively stable component.
COAST RANGE CORRIDOR IN CALIFORNIA
167
MIO-PLIOCENE
GEOFLORAS
□ ARCTO-TERTIARY
^ MADRO-TERTIARY
S NEOTROPICAL-
TERTIARY
Fig. 5. Distribution of geofiora during Mio-PIiocene time. (After
Axelrod (reconstructed).)
ARCTO-TERTIARY
Fig. 6. Alternative interpretations of zoogeographic peninsula existing
in California during Pliocene and early Pleistocene time.
168 F, E. PEABODY AND J. M, SAVAGE
Alternate maps may be presented (Fig. 6) depending on the pre-
sumed position of the marine strait, but in both cases demonstrat-
ing the barrier at the southern tip of the peninsula. The peninsula
persisted until the second peak of Coast Range orogeny in mid-
Pleistocene time and the following uplift brought the Clast Range
corridor into being.
Physical changes associated with Coast Range orogeny were not
in themselves sufficient to convert the Coast Ranges into a zoogeo-
graphic corridor. Entirely coincidental and independent climatic
changes were in progress. The work of Chaney (1940) in paleobotany
and of Durham in invertebrate paleontology (1950) has mutually
documented a continent-wide shift of isotherms southward through-
out the Cenozoic, reaching a maximum (with fluctuations) in the
Pleistocene epoch. According to Durham, the 18°C marine isotherm
was at latitude 35°N, coincident with the Southern Coast Ranges, in
the late Pliocene, and shifted 7° southward (over 400 miles) at the
peak of Pleistocene glaciation. Here is the climatic stimulus needed
to force faunal elements southward into the peninsula, perhaps
causing "jamming" or peninsular effects. Future study of fossil
mammals in the presumed peninsular area may show such effects
to be present. Certainly the marine faunas of the area are extremely
provincial in character. However, this is commonly attributed to
the many local, shifting basins of deposition attending the Coast
Range orogeny.
Coincidental with the Coast Range orogeny, the vast Sierra
Nevada block began to tilt westward, so as to form a high crest
running southward from a point near the present Lake Tahoe and
curving westward to a junction with the Southern Coast Ranges.
Axelrod's masterly use of paleobotanical data (1957) graphically
portrays the rise of the Sierra Crest from an average of 3,000 feet in
the Miocene to 8,500 feet in the Pleistocene, and the accompanying,
drastic, climatic effect on vast inland areas of the continent. Un-
doubtedly the formation of the Coast Ranges also contributed to the
drying of the interior. The combination of geological and climatic
changes in the far west resulted in a southward movement of the
Arcto-Tertiary geoflora, especially along the coast, and a northward
and northwestward movement of the Madro-Tertiary geoflora from
a Mexican center of origin. A Neotropical-Tertiary geoflora re-
treated southward along the coast.
COAST RANGE CORRIDOR IN CALIFORNIA 169
In summary: Geological data conclusively demonstrate that the
Central and Southern Coast Ranges were formed largely from sub-
marine portions of the continental shelf. The Coast Ranges then
constituted a land bridge between northern and southern California,
because a San Joaquin embayment to the east persisted as a marine
barrier well into the Pleistocene. Later withdrawal of the sea from
the embayment reduced the barrier potential between the Coast
Ranges and the Sierra Nevada, but the low, wide, dry valley re-
mains an effective barrier to many terrestrial organisms.
There is no doubt that the Central and Southern Coast Ranges
eventually formed a connecting bridge around the seaward side of a
great structural depression, but the connection remained incomplete
near the southern end until Mid- Pleistocene time. The area of the
bridge is cut lengthwise by one of the world's major faults, the San
Andreas. However, the movement along the fault is largely hori-
zontal, and although there may have been horizontal displacement
of several hundred miles in the Plio-Pleistocene, it is thought that
the zoogeographic effect of the fault movement was negligible. Only
after the second peak of Coast Range orogeny, accompanied by
continental uplift, did the land connection become a continuous
bridge or corridor available to the herpetofauna.
The original point of view here presented is that the land connec-
tion existed prior to the mid-Pleistocene as a large peninsula broadly
connected northward to the continent, as a continuous zoogeographic
(if not geographic) unit, and with an effective marine barrier in the
form of a wide strait at the southern tip. The barrier remained until
mid-Pleistocene time. At this time the Central and Southern Coast
Ranges became an effective corridor for the dispersal of many ter-
restrial organisms.
During late Miocene and early Pliocene the peninsula was largely
occupied by Neotropical and Madro-Tertiary geofloras. The Arcto-
Tertiary geoflora was excluded and along with it the associated
herpetofauna, on the basis of purely climatic control. At the same
time, herpetofauna of Mexican origin and associated with the
Madro-Tertiary geoflora may have been unable to reach the evolv-
ing peninsula because of the marine barrier at the southern tip. The
barrier, however, was not effective in limiting the northward exten-
tion of the Neotropical and Madro-Tertiary geofloras. The above
hypothesis is strengthened by the fact that no endemic species of
170 F. E. PEABODY AND J. M. SAVAGE
the present herpetofauna exist In the stable Santa Lucia positive
area of the peninsula. Geological and climatic events of the late
Cenozoic preclude such endemism. Finally, the profound and com-
plex influences brought to bear on the biota of the California region
are shown to be the result of an entirely fortuitous combination of
interacting geological and climatic changes having peak effect dur-
ing Pliocene and Pleistocene time: evolution of the Coast Ranges;
southward shift of marine and continental isotherms on a worldwide
basis; rise of the Sierra Nevada crestline with concomitant drying
of the interior; continental uplift.
CORRIDOR EFFECTS
Arcto-Tertiary Species
Major migrations of western geofloras described by Axelrod (1957)
are important to an understanding of distribution changes in the
contemporaneous herpetofaunas. The writers believe that the late
Cenozoic herpetofauna of the west may be correlated broadly with
the Arcto-Tertiary and Madro-Tertiary geofloras. Salamanders are
fundamentally boreal and Arcto-Tertiary, the lizards and snakes
are fundamentally Sonoran and Madro-Tertiary in historical rela-
tionship. The frogs and toads are transitional in that some forms
appear to be Arcto-Tertiary elements while others are of Madro-
Tertiary relationships. Biijo boreas and Rana aurora are examples of
the former; Bufo microscaphus, Rana boylii, and Rana miiscosa of
the latter. As a result of the combination of geological and climatic
events described above, the Arcto-Tertiary salamanders and frogs
tended to move southward and split around east and west sides of
the Great Valley depression. However, the western route down the
corridor was not complete until the mid-Pleistocene. Thus until the
last half of the Pleistocene a "dam" was in force which would allow
accumulation of genetic differences between east (Sierran) and west
(Coast Range) arms of Arcto-Tertiary dispersals. Unless the "dam"
was in force until relatively late in the Pleistocene, the flow of
genetic material down the corridor should have merged compatibly
with the flow down the mainland to eastward. Apparently this was
not the case. Once the corridor was in operation it was possible for
an Arcto-Tertiary species to disperse southward, subject to fluctua-
tions, in a pattern like that of Rana aurora (Fig. 7). Development of
clines along the route would be expected, and do occur. Few of the
COAST RANGE CORRIDOR IN CALIFORNIA
171
Arcto-Tertiary species range around the southern end of the Great
Valley at present, but many range around the northern end.
Trans-valley "leaks" have occurred across the valley barrier
but only from west to east at the position of the San Joaquin delta.
Apparently the "leaks" became possible during relatively recent
RED-LEGGED
FROG
RANA
^ 1 AURORA
Fig. 7. Distribution of red-legged frog, Rana aurora. Pattern is
typical of Arcto-Tertiary forms that have moved southward through
Sierra Nevada and coastal corridor. Arrows in Figs. 7-18 indicate proba-
ble movements from points of origin. (Figures 7-18 based on Stebbins,
with some modifications.)
fluctuation of humidity in the delta region. The subspecies xanthop-
tica of Ensatina eschscholtzii has established a population in the
Sierras and is currently showing some interbreeding with the es-
tablished Sierran sxihs^ecies platensis (Fig. 15). Similarly, the coastal
Aneides lugubris has established a population in about the same area
as the subspecies of Ensatina (Fig. 8). In a valuable study of this
phenomenon, Rosenthal (1957) points out that no Ijiological or
physical factor, other than time itself, limits the Sierran range of the
172
F. E. PEABODY AND J. M. SAVAGE
trans-valley leak, hence the Sierran population must be a recent
introduction across the valley. The only other trans-valley leak
noted seems to have occurred in the distribution of the limbless
lizard, Anniella pulchra, which is a Madro-Tertiary species. Again,
the leak has been from west to east, near the position of the delta.
It is not known if moisture has been the critical factor here as it
surely has been for the salamanders, or whether the leak is indeed
ARBOREAL SALAMANDER
ANEIDES LUGUBRIS
TRANS- /
\ VALLEY /
\"LEAK" /
\ '
Fig. 8. Distribution of arboreal salamander, Amides luguhris. Note
trans-valley leak, which probably occurred in pluvial times and estab-
lished species in Sierra foothills.
genuine (the supposed leak may represent an inadequately known
distribution of the lizard northward along the entire eastern side of
the Great Valley). The few occurrences of trans-valley leaks em-
phasize the overall efificiency of the Great Valley as a barrier to
transverse dispersal between the corridor and the Sierras except at
the north and south ends. Finally, no Arcto-Tertiary species appears
to have moved down the corridor and back up the Sierras, or vice
versa. Dispersals southward along the corridor and along the Sierras
have remained largely separated in southern California in coastal
lowland and interior highland, or have achieved only limited
sympatry there.
COAST RANGE CORRIDOR IN CALIFORNIA
173
Madro-Tertiary Species
Species of lizards and an anuran illustrate best the relationship of
the corridor to Madro-Tertiary elements moving in from Mexican
centers of origin. Southern mesic elements of the Madro-Tertiary
complex invaded the corridor from the south end, but in a variable
manner. The western spadefoot, Scaphiopus hanimondii, appears to
have "flooded" the corridor (Fig. 9) and the adjacent valley to its
northern end, meanwhile developing a wide disjunction in the lower
Colorado Valley. A related, northern species in the Great Basin
appears to be in the process of invading the San Joaquin Valley via
Walker Pass. Patterns somewhat similar to that of S. hammondii
occur in Bujo microscaphns and Ilyla arenicolor, without the pres-
ence of a related Great Basin species. This suggests that species ap-
WESTERN SPADEFOOT
SCAPHIOPUS
. j\ HAMMONDI
|L GREAT BASIN
•4^ SPADEFOOT
\^ S. INTERMONTANUS
7
/
Fig. 9. Distribution of western spadefoot, Scaphiopus hammondii, and
Great Basin spadefoot, Scaphiopus intermontanus. Former now has
disjunct distribution in Californias and areas to east. Apparently 5.
intermontanus has recently invaded western Sierran foothills through
mountain passes.
174
F. E. PEABODY AND J. M. SAVAGE
proaching the southern end of the corridor from the interior en-
counter a barrier at the southern Sierra crest and at the Transverse
Ranges. Warming and drying trends may enable desert species to
spread northward into the San Joaquin Valley via Walker,
Tehachapi, and Tejon passes. Distribution of the desert night lizard,
Xantusia vigilis (Fig. 10), indicates a relatively recent invasion via
Tehachapi and up the Sierra foothills, and an invasion via Tejon
DESERT "**
/ NIGHT
jL LIZARD /
*\ XANTUSIA /
VIGILIS I
Fig. 10. Distribution of desert night lizard, Xantusia vigilis. Invasion
of foothills on both east and west sides of Great Valley is apparently
progressing actively at present.
and up the dry inner Coast Ranges. A somewhat older invasion
through the passes into the San Joaquin Valley is suggested by the
distribution pattern of the leopard lizard, Crotaphytus wislizenii
(Fig. 11). The San Joaquin subspecies, silus, represents a stock
difTerentiated from the parent subspecies of the Great Basin, and
certainly reached the San Joaquin Valley from the south, across
mountain passes, during a climatic fluctuation.
Northern elements of the Madro-Tertiary complex have tended
to invade the corridor from the north, following the path of Arcto-
Tertiary species. The sagebrush lizard, Sceloporus graciosus (Fig.
12), has differentiated a Californian subspecies, graciosus, which has,
COAST RANGE CORRIDOR IN CALIFORNIA
175
SO to speak, made an "end run" around the north end of the Great
Valley and down the corridor. However, disjunct populations of
this and the southern subspecies, vandenhurghianus , suggest a post-
Pleistocene fragmentation and retreat northward. Somewhat similar
distribution patterns are found in the ringneck snake, Diadophis
amabilis, and the mountain kingsnake, Lampropeltis zonata.
Fig. 11
Fig. 11. Distribution of leop-
ard lizard, Crotaphytus wislizenii.
Race silus, is isolated in arid
southern portion of Great Valley.
'4
SAGEBRUSH
^^ LIZARD
SCELOPORUS
GRACIOSUS
/ V
1
u
^^^^"^•:;il....VANDEN- ,
A«V BURGHIANUSJ
I
^-1
Fig. 12
Fig. 12. Distribution of Scelo-
porns graciosus, sagebrush lizard.
Effect of coastal corridor on this
mesic species and fragmentation
of its range are noteworthy.
The northern alligator lizard, Gerrhonotus cocruleus (Fig .13), and
the foothill alligator lizard, G. muUicarinatus (Fig. 14), probably
differentiated from an ancestral Mexican species. The derived
species present a curious contrast in distribution. The northern
alligator lizard appears to have made an "end run" around the Great
Valley and invaded the corridor part way. The coastal arm is sub-
176
F. E. PEABODY AND J. M. SAVAGE
specifically distinct. Generally the distribution pattern is like that of
Sceloporus graciosiis (Fig. 12). The foothill alligator lizard, preferring
warmer, drier habitat than the northern alligator lizard, ranges
completely around the Great Valley and broadly up and down the
California Coast. However, there is subspecilic differentiation, which
COERULEUS
35
'ANCESTRAL SPECIES
SONORAN ALLIGATOR
LIZARD
Fig. 13. Patterns of distribution for northern alligator lizard, Gerrho-
notus coeruleus, and related Sonoran alligator lizard, Gerrhonotus kingi.
Filter effect of coastal corridor is clearly apparent.
has highly interesting boundaries. Gerrhonotus muUicar hiatus webbii
ranges the southern California Coast and up the Sierra Nevada, but
is differentiated from the northern California subspecies precisely in
the position of the marine barrier postulated earlier. This coinci-
dence would be unimportant were it not for the fact that insular
representatives of the two subspecies (Fig. 14) are also separated —
multicarinatus occurring on four islands north of the mainland
boundary, webbii on three islands south of the boundary. There is
COAST RANGE CORRIDOR IN CALIFORNIA
177
the possibility that the subspecies in the corridor came in from the
North in the Pleistocene at a time when the marine barrier existed
at the south end of the present corridor. In any case the coincident
insular and mainland distribution suggests a certain antiquity of
subspecific differentiation. It would be interesting to know the rela-
•-■4 FOOTHILL
ALLIGATOR
LIZARD
rcriMcirA. ,nAiGERRHONOTUS
rSCINCICAUDAS mULTICARINATUS
35'
'ANCESTRAL SPECIES
SONORAN ALLIGATOR
LIZARD
Fig. 14. Distribution of foothill alligator lizard, Gerrhonotus multi-
carinatus, and its relationship to range of Gerrhonotus kingi, Sonoran
alligator lizard. Eastern species is more closely allied to G. muUicarinatiis
than to G. coeruleus, and the last two forms occur sympatrically in many
regions.
tive degree of differentiation between webbii and midticarinatus on
the south and north ends of the San Joaquin Valley.
In summary: Relations of A^Iadro-Tertiary species to the corridor
and adjacent land features appear more varied than for Arcto-
Tertiary species. Northern elements of the Madro-Tertiary moved
around the north end of the Great Valley and down the corridor;
southern elements moved up the corridor, or if xeric in habitat
preference, met an effective barrier at the Transverse Ranges and
178
F. E. PEABODY AND J. M. SAVAGE
the southern Sierra Nevada. Warm, dry trends of cHmate allowed
xeric elements to move north through mountain passes and into the
San Joaquin Valley and bordering foothills.
Sympatry in Southern California
Four cases of sympatry between closely allied forms occur in
southern California. Two of the four cases involve amphibians of
Arcto-Tertiary afTfinities; one of amphibians and one of reptiles are
of northern Madro-Tertiary affinities. The sympatry is not of the
same degree in each case, but it is sufficiently clear-cut to draw
attention to its localized occurrence in southern California. The high
incidence of sympatry here strongly suggests a controlling, historical
factor. It is believed that this factor is primarily the evolution of a
Coast Range corridor as outlined earlier.
1. A classic rassenkreis of subspecies is represented by the dis-
tribution pattern of Ensatina eschscholtzii in California (Stebbins,
^^^,ESCHSCHOLTZ'S
SALAMANDER
ENSATINA
-^^ESCHSCHOLTZII
XANTHOP
TICA'
35
ESCHSCHOLTZII
SYMPATRIC
.V/;=INTERGRADE
Fig. 15. Distribution of painted salamander, Ensatina eschscholtzii.
Subspecies E. e. eschscholtzii and E. e. klanberi occur together in upper
San Gorgonio River system, San Bernardino Mountains.
COAST RANGE CORRIDOR IN CALIFORNIA
179
1954, 1957). The pattern results from a southward movement of a
boreal species that split around the Great Valley barrier (Fig. 15).
The coastal arm is characterized by a solid color pattern, the Sierran
arm by a spotted color pattern. Aside from a trans-valley leak noted
earlier, the two arms maintain their identity at separate elevations
in southern California, but are found in true (if limited) sympatric
association at moderate elevations in the Peninsular Ranges. The
Sierran arm has undergone more differentiation and more fragmen-
tation, thus suggesting that it is older than the coastal arm.
2. Two closely related species of the slender salamander, Batra-
choseps attenuatus and B. paci'ficiis, are associated in extensive
sympatry (Fig. 16) in southern California, along the coast (Stebbins
and Lowe, 1949; Savage and Brame, 1957). The species may live
together under the same rock or piece of wood. B. pacificus appears
to be an older species in southern California, if judged from the
degree of subspecific variation and particularly because of its oc-
"■^ SLENDER
/SALAMANDER
/ BATRACHOSEPS
--^ A, PLIOCENE ") .
^-T-^ / ^FOSSIL }-t
--^RACKWAYJ
SYMPATRIC
PACIFICUS'
LEUCOPUS
B. PACIFICUS /
I
-1
^^^\CAr ^
Fig. 16. Distribution of slender salamanders, genus Batrachoseps.
Slender salamander, B. attenuatus, is found in sympatry with worm
salamander, B. pacificus, in numerous localities in Los Angeles and
Orange counties of California, and on Santa Cruz Island.
180
F. E. PEABODY AND J. M. SAVAGE
currence on six offshore islands, while the other species has managed
only one insular invasion. Fossil trackways of Mio-Pliocene age,
near Sonora in the Sierra Nevadas (Peabody, 1940) suggest that
B. pacijicus was derived from the north in pre- Pleistocene time.
B. attenuatus represents the appearance of a younger species in
southern California, more advanced in a trend toward attenuation,
and one that shows the forked distribution pattern of a boreal species
with respect to the Great Valley barrier.
DISJUNCT
i
MUSCOSA
Fig. 17. Distribution of yellow-legged frogs, Rana boylii and R.
muscosa. The latter is found at high elevations in Sierra Nevada and in
montane situations in southern California. Sympatry with R. boylii
occurs at one locality in San Gabriel Mountains.
3. The distribution pattern of the two species of the yellow-
legged frogs, Rana boylii and Rayia muscosa (Fig. 17), displays a
situation resembling that of Ensatina (Zweifel, 1955). The younger
of the two species, boylii, ranges around the Great Valley barrier in
the familiar forked pattern. The range is more or less continuous
except for a small, disjunct population at the southern end, in the
San Gabriel Mountains. Here there is a limited sympatry with the
older species, muscosa. The older species ranges at high elevations in
the Sierra Nevada and has undergone post-Pleistocene fragmenta-
COAST RANGE CORRIDOR IN CALIFORNIA
181
tion into populations on several mountain ranges of southern Cali-
fornia — San Gabriel, San Bernardino, San Jacinto, and Palomar.
4. Two closely related species of skinks (Fig. 18) show a limited
sympatry in the Southern Peninsular Ranges of southern California.
The sympatric relationship is not so well established as for Ensatina
GILBERTS SKINK
SYMPATRIC— 3Si!llX z' ^ ^
EUMECES I
GILBERT! /
Fig. 18. Distribution of western skink, Eumeces skiltonianus, and
giant western skink, Eumeces gilberti.
and Batrachoseps, but appears to be valid. Also, it is more difficult to
explain reasonably the location of the sympatry. However, the
sympatry of the skinks is of particular interest for the reason that
it is unique for closely related species of reptiles in the far west,
and involves a northern Madro-Tertiary component that has made
an end run around the northern end of the Coast Range corridor.
The northern species, Eumeces skiltonianus, appears to have moved
down the corridor along with boreal species. A few insular popula-
182 F. E. PEABODY A\D J. M. SAVAGE
tions, a derived endemic species {E. lagiinensis) at the tip of Baja
California, and a disjunct population in southern Nevada suggest
that the species was an early migrant down the corridor. Eumeces
gilberti maintains strict separation of range along its western limits
except for the sympatry in southern California. There may be a
limited sympatry also at the northern end of the range. The species
has several disjunct populations in the Great Basin and one in
Arizona, all suggesting considerable post- Pleistocene fragmentation.
The relatively high incidence of sympatry between closely related
forms in southern California suggests a set of well-timed physical
conditions which must first maintain genetic isolation and then
allow the isolation to break down. If the Coast Range corridor, Great
Valley, and Sierra block had possessed their present form and rela-
tionship from Late Pliocene to Recent, it is doubtful that genetic
isolation would have been maintained by west and east arms of
species dispersing southward around the Great Valley barrier,
whether or not gross climatic changes acted as stimulants. Some-
thing must have blocked one of the dispersal routes. The evolution
of a Coast Range corridor, as outlined earlier, exactly fulfills the
conditions of time, place, and climate necessary to produce the ob-
served sympatric conditions. Under the conditions that prevailed,
sympatry anywhere else in the far west was unlikely. Also, it was
unlikely under prevailing conditions that sympatry would develop
in Madro-Tertiary species unless a northern element were to make
an end run from the northern Great Basin to the west and down the
corridor in company with purely boreal species. That this could
happen is indicated by the somewhat special sympatry of the skinks
(of example 4, above). Under the prevailing conditions Madro-
Tertiary species of more xeric preference could not disperse up the
corridor, and in fact, were barred from it until relatively recent
times when dispersal over mountain passes has been possible. Fi-
nally, it should be emphasized that the areas of sympatric associa-
tion are precisely where they should be in relation to the presumed
barrier to dispersal down the corridor in Pre-Middle Pleistocene
time and to the junction of corridor and Sierran dispersals. (See
Fig. 19 for summation.)
The time when sympatry in southern California became possible
must not be earlier than mid-Pleistocene time, if our concept of the
evolution of the Coast Range Corridor is correct. Thus one is more
COAST RANGE CORRIDOR IN CALIFORNIA
183
al)lc to judge the relative age of west and east arms of dispersals
reaching southern California via the corridor and the Sierran or
Inland route. At least In the four examples of sympatry cited, It is
fairly certain that the dispersals down the corridor are the "new--
comers" to southern California. The evidence of corridor evolution,
together with relative development of insular populations and
^=^-. y-
35'
BRIDGE
SYMPATRIC
POTENTIAL
Fig. 19. Map showing probable migration paths taken by modern
amphibians and reptiles with respect to the Coast Range corridor and
associated geographic features.
development of post-Pleistocene fragmentation of patterns of
distribution are keys to relative age determination.
Coastal Islands and "Waif" Faunas
Distribution of the far western herpetofauna on offshore islands of
southern California (Stebbins, 1954) suggests that it may be profit-
able to reexamine the established theory that the offshore Islands
have been connected with the mainland at one time or another
during the late Pleistocene. Among the amphibians, only Bairacho-
seps, Aneides luguhris, and Hyla regilla have reached offshore Islands.
184 F. E. PEABODY AND J. M. SAVAGE
These amphibia are well suited for "waif" dispersal and the main-
land opposite the islands has numerous stream channels that fre-
quently sweep enormous amounts of sediment and floating debris
into the ocean. In the case of Batrachoseps, the older species {paci-
ficus) on the mainland has populated the largest number (5) of the
offshore islands. The younger species {attenuakis) has reached but
one island (Fig. 16).
The reptilian insular fauna appears erratic in distribution, and
significantly there are no chelonians. Certainly the distribution of
insular herpetofauna does not support the theory of "tied" islands,
and the relationship of mainland herpetofauna to the Coast Range
corridor suggests a generally high degree of sensitivity to land
routes.
CONCLUSIONS
The fossil record at present contributes little to a detailed study
of origins and dispersals of the modern herpetofauna of western
North America. However, a synthesis of the data from geology,
paleontology, and herpetology indicates that the far west, particu-
larly California, was the locus of physical events during the late
Cenozoic era that shaped the destiny of the modern herpetofauna.
The synthesis reveals an especially intriguing example of the physi-
cal factors inherent in biological evolution — the coincidence of time,
place, and climate contributing to the randomness and opportunism
of evolution. The synthesis suggests that such fortuitous interac-
tions of time, place, and climate might be considered a major factor
in biologic evolution, along with genetic variability, selective pres-
sure, and geographic isolation. Perhaps this might be considered a
fourth major factor in biologic evolution along with genetic varia-
bility, selective pressure, and geographic isolation. Perhaps this
factor could be included in the term "geodynamics."
A major result of the synthesis is the concept of a Pacific Coast
Range corridor which took shape in Pliocene and early Pleistocene
time as a zoogeographic peninsula connected to the mainland on the
north, and separated by a marine barrier strait from mainland to
the south. After mid-Pleistocene time the peninsula became a con-
tinuous corridor allowing dispersal in both directions, but causing
a high incidence of sympatry in the herpetofauna of southern Cali-
fornia. The study of origins and dispersals relative to the evolution
COAST RANGE CORRIDOR IN CALIFORNIA 185
of the Coast Range corridor would appear to represent a fruitful
field of investigation, not only in herpetology but also other branches
of natural history. Evolution of the Coast Range corridor provides a
unique opportunity to study the influence of a small but efi'ective
land bridge on its associated biota. Unlike large, classic land bridges,
such as the Panamanian Isthmus, the Coast Range corridor is a
phenomenon of small scale lending itself to intensive investigation
from many directions by biologists and geologists alike. We may
confidently reaffirm and echo A. B. Howell's assertion of thirty
years ago that the fauna of the Pacific Coast is of unusual interest
and presents many fascinating problems. Californians have a land
bridge laboratory in their own back yard !
Acknowledgment
Grateful acknowledgment is given to Miss Madeline Peabody for her
most valuable aid in drafting the illustrations and assisting with the
manuscript.
REFERENCES
Axelrod, D. 1957. Late Tertiary floras and the Sierra Nevadan uplift.
Bull. Geol. Soc. Am., 68: 19-46.
Brattstrom, Bayard H. 1954. Records of Pleistocene reptiles from Cali-
fornia. Copeia, 3: 174-179.
. 1955. New snakes and lizards from the Eocene of California.
/. PaleontoL, 29: 145-149.
Camp, C. L. 1952. Earth Song. University California Press, Berkeley,
Calif.
Camp, C. L., et al. 1940-1953. Bibliography of fossil vertebrates. Geol.
Soc. Am.: Spec. Papers 27, 42; Memoirs 37, 57.
Chaney, Ralph W. 1940. Tertiary forests and continental history. Bull.
Geol. Soc. Am., 51: 469-488.
Condit, Carlton. 1944. Pliocene floras of California and Oregon, Chap. 3,
The Table Mountain flora. Carnegie Inst. Wash. Puhl., 553, pp.
57-90.
Durham, Wyatt. 1950. Cenozoic marine climates of the Pacific Coast.
Bull. Geol. Soc. Am., 61, 1243-1264.
Eardley, A. J. 1951. Structural Geology of North America. Harper, New
York.
Howell, A. B. 1927. On the faunal position of the Pacific Coast of the
United States. Ecology, 8: 18-26.
Peabody, F. E. 1940. Trackways of Pliocene and recent salamandroids of
the Pacific Coast of North America. M. A. thesis in Library of the
University of California, Berkeley.
186 F. E. PEABODY AND J. M. SAVAGE
■ — ■ — — . 1954. Trackways of an ambystomid salamander from the Paleo-
cene of Montana. /. Paleofitol., 28: 79-83.
Reed, C. F. 1956. Index to Copeia 1913-1954. Science Press, Lancaster, Pa.
Rosenthal, Gerson M. 1957. The role of moisture and temperature in the
local distribution of the plethodontid salamander. Amides luguhris.
Univ. Calif. Piibl. ZooL, 54: 371-420.
Savage, J. M., and A. H. Brame. 1957. The Southern California slender
salamanders: A solution of the Batrachoseps problem. (1957 meeting,
Soc. Evolution, Stanford Univ.) (manuscript).
Stebbins, R. C. 1949. Speciation in salamanders of the plethodontid genus
Ensatina. Univ. Calif. Picbl. ZooL, 48: 377-526.
— — ■ — ■. 1954. Amphibians and Reptiles of Western North America. Mc-
Graw-Hill, New York.
-. 1957. Intraspecific sympatry in the lungless salamander Ensatina
eschscholtzi. Evolution, 11: 265-270.
Stebbins, R. C., and C. H. Lowe, Jr. 1949. The systematic status of
Plethopsis with a discussion of speciation in the genus Batrachoseps.
Copeia, 1949: 116-129.
Taliaferro, N. L. 1943. Geologic history and structure of the Central
Coast Ranges of California. Calif. State Div. Mines, Dept. Nat. Re-
sources, No. 118, pp. 119-162.
Van Frank, Richard. 1955. Palaeotaricha oligocenica, new genus and
species, an Oligocene salamander from Oregon. Breviora, Museum
Comp. ZooL, Cambridge, No. 45, pp. 1-12.
Zweifel, Richard G. 1955. Ecology, distribution, and systematics of frogs
of the Rana boylei group. Univ. Calif. Publ. ZooL, 54: 207-292.
. 1956. Two Pelobatid frogs from the Tertiary of North America
and their relationships to fossil and recent forms. Am. Museum
Novitates, 1762: 1-45.
9
Origin and Affinities of the Freshwater
Fish Fauna of Western North America
Robert Rush Miller
Museum of Zoology, University of Michigan,
Ann Arbor
1 he area covered by this paper is primarily
North America west of the Continental Divide, northward to
the Stikine River, British Columbia, and southward to the Rio
Yaqui, northwestern Mexico. The Yaqui is included because it
contains certain faunal elements derived from the Colorado River,
and British Columbia is treated since its coastal streams include a
number of Columbia River types (Lindsey, 1957). Excluded from
consideration, except in passing, are the Arctic and Bering Sea
drainages, and only mentioned is the interdigitation of Nearctic
and Neotropical fishes in Middle America.
Thirty families comprising nearly 200 species have been recorded
from fresh water within this area (Table I). These groups form a
diverse assemblage. Twelve of the families include species in the
Western fauna that are predominantly marine, although some
inhabit brackish water or invade fresh water to a limited extent,
especially toward the tropics, e.g., herrings, flatfishes, silversides,
mullets, sticklebacks, and gobies. Representatives of four families
regularly pass only part of their life cycle in the sea or in fresh water
(lampreys, sturgeons, some smelts, and most trouts). Species repre-
senting four families were derived from marine ancestors but they
are now virtually restricted to fresh water (a gizzard shad, Dorosoma ;
a codfish, Lota; a viviparous perch, Ilysterocarpus ; and the fresh-
water sculpins, Cottus). Two families, the whitefishes (Coregonidae)
and graylings (Thymallidae) , are intimately related to the salmons
and trouts (Salmonidae), which occur in either the sea or fresh water.
In interpreting origins and dispersal patterns it is essential to
distinguish the true freshwater fishes from these groups. Although I
187
188
R. R. MILLER
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190
R. R. MILLER
consider affinities of the freshwater fauna as a whole, emphasis is
placed on groups designated as primary (I) — made up of those fishes
that throughout their known history have, with rare exceptions,
been restricted to fresh water (Fig. 1). These comprise the great
continental faunas dominant on all land masses save Australia
(Darlington, 1957, Fig. 11); they fall principally into a single order
NUMBERS OF
FAMILIES, GENERA
AND SPECIES
OF NORTH AMERICAN
PRIMARY
FRESHWATER FISHES
w
Fig. 1. Primary freshwater fishes of North America. For simplifica-
tion, the Lahontan Basin (labeled 2-7-8) is mapped too extensively,
including areas treated separately under Isolated Basin Drainages. See
text for discussion. See also Tables I-II.
FRESHWATER FISH FAUNA 191
(Ostariophysi = Cypriniformcs) containing about 5,000 species.
Also of value are the secondary (II) freshwater fishes representing
groups largely restricted to fresh water but salt-tolerant and capable
of occasionally crossing narrow sea barriers. The remaining fishes
known from fresh water may be divided as follows (Myers, 1938,
1951) : Diadromous (III), those that regularly migrate between fresh
and salt water during a definite period of the life cycle. Vicarious
(IV), essentially or presumably non-diadromous freshwater repre-
sentatives of partly or primarily marine groups. Complementary
(V), species that are often or usually diadromous and belong to
marine groups that become dominant in fresh waters only in the
scarcity or absence of primary and secondary fishes. Sporadic (VI),
fishes living and breeding more or less indifferently in salt or fresh
water or entering fresh water only sporadically. The 30 families
recorded from fresh water within the area comprise 6 primary
groups with nearly 100 species and 3 secondary families with only 15
species. Thus the primary (I) and secondary (II) fishes constitute
somewhat more than half the total number of species that occur in
western fresh waters.
The absence of a large and diverse drainage system, such as the
Mississippi, and the general scarcity and instability of the aquatic
environment help to explain why the freshwater fish fauna of the
West lacks many of the families and genera, especially lowland types,
that live east of the Rockies (Fig. 1). The depauperate western fauna
comprises only half as many families and one-fourth as many species
of primary and secondary fishes as the eastern fauna. It is made up
of relicts, an abundance of monotypic genera, and a complex of
endemic faunas with few widespread species in common. Many of
the species are of restricted distribution (Fig. 2).
Our knowledge of the systematics of this fish fauna is behind
that of the other vertebrates. This is especially true of the published
record. Although the few taxonomists who have worked with western
fishes in the past quarter century have restricted most of their
publication to the description of new taxa, I estimate that about 10
per cent of the species have yet to be described. Rather considerable
recent field work, begun in 1934, has built up a wealth of preserved
material and observations that await critical evaluation. No up-to-
date generic revisions have appeared, and the inadequate fossil
record provides few hints for speculation on the interrelationships of
192
R. R. MILLER
Fig. 2. Approximate location of species of closely restricted distribu-
tion in western North America. Note the concentration of localized forms
in the Great Basin and in disrupted waters (in southern Nevada) of the
Colorado River drainage. Only 14 of the 43 species occur outside of those
areas.
the modern forms, particularly at the generic level. It is not sur-
prising, therefore, that the affinities of many of the genera are
unknown.
FOSSIL RECORD
The paleontological record of Tertiary and Quaternary fishes in
western North America is meager. What little material is available
has not received critical comparative study. For the most part, the
available skeletal remains, particularly of the Pliocene and Pleisto-
cene fossils, are hardly adequate for identification below the generic
level or, occasionally, not even below the family. The only reason-
ably well-known formation is that of the Green River Eocene, which
involves a fauna too early in fish evolution to give much help in
interpreting the modern forms. Tertiary fishes have been treated
chiefly by Cope, and since his death in 1897, only scattered papers
have appeared with little attempt at evaluation or reappraisal.
Vigorous, organized search for and comprehensive study of late
Cenozoic fish fossils by students thoroughly familiar with the Recent
fauna is one of the urgent needs for advancing knowledge of the
origin, dispersal, and evolution of the present fauna.
Fossils representing nine families have been recorded from fresh-
water deposits of Miocene to Pleistocene age in western North
FRESHWATER FISH FAUNA 193
America (Cyprinidae, Catostomidae, Ictaluridae, Aphredoderidae,
Centrarchidae, Salmonidae, Cyprinodontidae, Cottidae, and Gas-
terosteidae) . The first five are primary division freshwater fishes;
the remainder are of diverse origin (boreal, secondary tropical,
marine types or derivatives). Certain Miocene fossils from the Great
Basin, e.g., from the Humboldt Formation, Nevada, indicate that
at this time there were kinds of fishes (a sucker, Amyzoji, and a pirate
perch, Trichophanes) quite unlike those that now inhabit the West;
Miocene and Pliocene sunfishes (Centrarchidae) of extinct genera
from Oregon, Nevada, and Utah demonstrate that this family, now
largely restricted to eastern North America, was then more wide-
spread. A minnow from British Columbia, Leiiciscus rosei (Hussakof,
1916), thought to be of Miocene age, probably represents the living
genus Richardsonius , and a Miocene minnow from Nevada is of
essentially modern facies (Hubbs and Miller, 1948, p. 26), From
these sketchy data it may be inferred that during the long Miocene
epoch and extending into the Pliocene, one family (Aphredoderidae)
and a number of genera {Amyzon, sunfishes, Trichophanes) became
extinct in the West, though relatives have persisted in eastern North
America, and that, although the Miocene fauna as a whole is quite
different from the existing fishes, at least one modern freshwater
type {Richardsonius) probably became established during this
epoch.
Two early Pliocene fossils from beds within the Lahontan system
of Nevada, a killifish {Fiindulus nevadensis) and a stickleback
(Gasterosteus doryssus), belong to genera of coastal and lowland dis-
tribution living today in western North America only along the
Pacific slope. Their entrance into Nevada, perhaps in late Miocene
or early Pliocene times, may have been from the southwest by way of
what is now the Death Valley region, since fossil killifishes of the
same genus occur there (Miller, 1945b) and sticklebacks are found
as far south today as northern Baja California.
Middle Pliocene fossils from the Bidahochi formation in the
Colorado system of northern Arizona represent species of Gila and
Ptychocheilus similar to the living forms that are adapted to a swift-
water habitat. This suggests that the Colorado was then a swift
river, and such an ecological picture is supported by recent studies
of geologists on the evolution of the Colorado (Repenning et al.,
manuscript), A Pliocene minnow from the Esmeralda formation of
194 R. R. MILLER
Nevada, Leuciscus turneri (Lucas, 1900), is likely identical with a
modern genus (Gila); the age of this formation, first thought to be
Miocene, was discussed by Stirton (1936, 1939).
A late Pliocene to early Pleistocene fauna from southern Idaho
and eastern Oregon contains representatives of 6 families, including
a catfish of the genus Ictaliiriis and a sunfish likely of the genus
Lepomis ; the latter genus is now restricted to eastern North America
and Ictaluriis is not native on the Pacific slope north of the Yaqui
basin (Figs. 5 and 9). Both genera represent invaders from the East
whose extinction in the Snake River basin in early Pleistocene times
is probably correlated with lowering of water temperatures below
the minimum spawning requirements of these fishes. Most of the
fossils representing this fauna were discussed by Cope (1883, pp.
153-165).
This brief summary of the sketchy fossil record indicates the ur-
gent need for research on the paleoichthyology of the later Cenozoic,
particularly for comparisons of the fossils with their living relatives.
Much of the material is not identifiable because of our inadequate
knowledge of the osteology of modern fishes.
PRIMARY AND SECONDARY GROUPS
The primary freshwater fish fauna of North America (Fig. 1)
comprises 21 families with approximately 600 species. Although these
are mapped by areas that generally follow major watersheds, it is
not intended that these areas portray zoogeographic regions. The
numbers, representing families, genera, and species, become less
accurate south of the United States border. The richness of the
Mississippi Valley fauna is noteworthy, as is the absence of primary
fishes in the West Indies. In general, there is a trend toward more
species to the south, perhaps correlated with more equable water
temperatures and a greater diversity of habitats. The apparent
richness of the Arctic fauna is largely the result of invasion of the
Red River by Mississippi fishes during late Pleistocene times.
Similarly, as a result of Glacial and Postglacial connections, the
fauna of the Great Lakes basin is strikingly similar to, though
smaller than, that of the Mississippi Valley.
The Plateau Region of northern Mexico has provided a broad
highway over which many Nearctic types have traveled southward.
Although the bulk of these fishes are stopped by the east-west chain
FRESHWATER FISH FAUNA 195
of volcanoes lyin^i? at about 19° N. Lat., a sucker {Idiohiis meri-
dionalis) and a catfish {Ictaluriis meridionalis) have managed to
reach the basin of the Rio Usumaclnta, Guatemala. The Mexican
coastal regions, particularly the Atlantic coastal plain, have simi-
larly allowed the northward penetration of Neotropical groups. A
single representative each of the characins {Astyanax jasciatus) and
cichlids {Cichlasoma cyanoguttatiim) has invaded the United States
in extreme southwestern Texas, and the characin has moved into
New Mexico (these two are the only primary families shared by the
United States and South America).
The southern end of the Middle American peninsula has been
invaded by a number of South American groups, most of which
drop out beyond western Panama, although the eel-like Gymnotidae
are represented as far north as Guatemala. The fish fauna inhabit-
ing the peninsular-like region between the Isthmus of Tehuantepec
and Panama is dominated by secondary freshwater fishes, notably
the Poeciliidae and the Cichlidae. The viviparous poeciliids pre-
sumably arose within this area, diversified greatly, and spread
northward and southward ; the cichlids and pimelodids, on the other
hand, probably originated in South America and speciated in the
unsaturated environment of Middle America. These two groups,
with additions from the Characidae and Atherinidae, constitute the
more tropical portion of Middle American fauna. Intervening be-
tween this portion of the Middle American fauna and the Nearctic
fauna of northern Mexico are several transitional faunas and the
highly distinctive Lerma fauna, which includes a limited representa-
tion of both middle American and North American genera, and is
dominated by the endemic cyprinodont family Goodeidae and the
endemic and diverse atherinid genus Chirostoma. The Lerma fauna
may be regarded as a distinct element in the Middle American
complex.
The relatively impoverished primary fauna of western United
States is indicated for the 8 drainage areas shown on the map (Fig.
1). Within the entire area there are only 6 primary families (Table
I): the mudminnows (Umbridae), minnows (Cyprinidae), suckers
(Catostomidae) , catfishes (Ictaluridae), trout-perches (Percopsidae),
and sunfishes (Centrarchidae). The first three are regarded as of
Eurasian origin, and the last three as North American.
The mudminnows (Fig. 3) are represented by two genera, Nov-
196
R. R. MILLER
T^^'J^^.
Fig. 3. New World distribution of the mudminnows (Umbra and
Novumbra) and the blackfish (Dallia). The only other mudminnow, Umbra
krameri, lives in eastern Europe. Dr. Norman J. Wilimovsky provided
the northeastern limit of the range of Dallia.
umbra (Fig. 4), a monotypic relict from the Olympic Peninsula of
Washington (Schultz, 1936), and Umbra, with two species in eastern
United States and one in Europe. The suborder (Haplomi =
Esocoidei) to which these fishes belong contains also the pikes,
which are circumboreal but most speciose in North America, and the
Fig. 4. The western mudminnow, Novumbra hiibbsi, a relict species of
the Chehalis and Deschutes rivers, Washington. (From original drawing
by Dorothea B. Schultz; see Schultz, 1936, Fig. 38.)
FRESHWATER FISH FAUNA
197
Fig. 5. Distribution of the North American freshwater catfishes,
family Ictaluridae. Fossil occurrences of Ictalurus are shown for western
North America only. (Modified from Rostlund, 1952, maps 18-20;
Mexican portion original.)
blackfish (Dallia), which lives in Alaska and Siberia. Although the
present distribution suggests a North American origin, all known
fossils, including the primitive genus Palaeoesox (Berg, 1936), are
from the Eocene to Miocene of Europe.
The North American catfishes, comprising about 6 genera and 35
species, barely enter the western fauna with a single species in the
Yaqui River. That these fishes formerly occurred much farther
north in the West has already been pointed out. All known fossils
are North American, as is the present distribution (Fig. 5).
Trout-perches constitute a singular group represented by two
monotypic genera, Columbia (Fig. 6) restricted to the basin of that
name in the West, and Percopsis, of much wider distribution in the
East. With the closely related monotypic pirate perches (Aphredo-
198
R. R. MILLER
Fig. 6. The Columbia River trout-perch, Columbia transmontana.
(From original drawing by A. H. Baldwin; see Jordan and Evermann,
1900, Fig. 330).
Fig. 7. Distribution of the North American trout-perches and pirate
perches. The fossil pirate perch, Trichophanes, is known only from north-
eastern Nevada. (Percopsidae greatly modified from Rostlund, 1952,
map 32, using Walters (1955), Lindsey (1956), and original data. Range
of Aphredoderidae from unpublished map by Reeve M. Bailey.)
FRESHWATER FISH FAUNA 199
deridae), they form a North American group known from Eocene
to Recent (Fig. 7).
The centrarchids, or sunfishes, comprise a compact family of
about 11 genera and 30 species, which, except for the rehct genus
Archoplites of California (Fig. 8), are confined to eastern North
America (Fig. 9). The present center of distribution is in the middle
and lower Mississippi Valley. Relatively numerous fossils are
recorded from Oligocene to Pleistocene deposits of North America ;
whether or not the Green River Eocene genus Priscacara is a sunfish
has not been conclusively shown, although Regan (1915, p. 106) un-
questionably referred it to the Centrarchidae. This freshwater
group dates from the early Cenozoic and is closely related to the sea
basses (Serranidae). Since as a whole sunfishes are characteristic of
lowland waters, the sole survivor in the West presumably attained
its present distribution prior to the formation of the Rocky Moun-
tains and Sierra Nevada Ranges.
The two remaining families, the minnows and suckers, account
for 95 of the 99 species of primary freshwater fishes in western
North America. The suckers, a compact group of 14 living genera^
and about 80 species, are known fossil and Recent from eastern
Asia and Alaska, as well as from eastern and western North Amer-
ica. In the New Worid (Fig. 10) they range southward on the
Atlantic slope to northern Guatemala {Ictiobus, Rio Usumacinta)
and on the Pacific versant to western Mexico {Moxostoma, Rio
Armeria, Jalisco). In the Old Worid there are but two representa-
tives, an ancient, monotypic genus in China {Myxocyprinus) and
Catostomus catostomus, in eastern Siberia, representing a recent
invasion of a species widespread in northern North America (Dar-
lington, 1957, p. 31, Fig. 9). In the most recent treatment (Nelson,
1948, 1949), division of the family into three subfamilies (Fig. 11)
has been made largely on the basis of the morphology of the four
highly modified anterior vertebrae (the Weberian apparatus) that
connects the gas bladder with the middle ear. The Cycleptinae, with
a primitive genus in each continent, might justifiably be segregated
as two subfamilies with Cycelptiis as the North American and
Myxocyprinus as the Asian representative. The Ictiobinae includes
but 2 genera and 9 species in eastern North America and appears to
1 The following are regarded as synonyms: Deltistes = Catostomus; Megapharynx and
Placopharynx = Moxostoma; Megastomatobtis = Ictiobus.
200
R. R. MILLER
Fig. 8. Sacramento perch, Archoplites interruptus, the only native
sunfish west of the Rocky Mountains. (From Jordan and Evermann,
1902, p. 341).
Fig. 9. Distribution of the Nearctic family Centrarchidae. Fossil
records are indicated only for areas outside of the present natural range
of the sunfishes.
FRESHWATER FISH FAUNA
201
be a conservative group characteristic of lowland waters. The re-
maining 10 genera belong to the Catostominae ; 2 of its 3 tribes, the
Moxostomatini and Catostomini, contain over 80 per cent of the
known species of suckers. Five of the 14 genera are monotypic:
3 in eastern United States {Cydeptus, Lagochila, and Minytrema),
1 in western United States {Xyrauchen, Fig. 12), and 1 in China
Fig. 10. Distribution of the sucker family, Catostomidae, in North
America and adjacent Siberia; one genus is endemic to China. Northern
limit between western side of Hudson Bay and Coppermine River from
Wynne-Edwards (1952, p. 18).
(Myxocyprinus) . One genus in the East, Moxostoma, and 2 with
most of their species restricted to the West {Catostomus and Pan-
tosteus), account for 65 per cent of the modern species.
The earliest possible fossil sucker remains (Hussakof, 1932, pp.
16-17) are from Eocene deposits of Central Asia and are probably
closest to the Chinese genus Myxocyprinus (Nelson, 1949, p. 566).
The earliest reliably dated remains of the family in North America
202
u. R. mii.i.i:k
MYXOCYPRINUS
ERIMY20N MOXOSTOMA CATOSTOMUS
THOBURNIA \ PANTOSTEUS
IcHASMISTES
'XYRAUCHEN
' — AMYZON [MIOCENE, N AMJ
hHYPOTHETICAL PHYLOGENY
OF THE FAMILY
CATOSTOMIDAE
CVPRINIO ? PROTOTYPE
Fig. 11. Hypothetical phylogeny of the Catostomidae. The approxi-
mate number of species in each subfamily and tribe is shown in the
circles.
are from Miocene deposits in British Columbia, Nevada, and
Colorado, and arc placed in an extinct genus Amyzo7i. Superficially,
at least, this sucker bears a close resemblance to the living genus
Ictiobus, but a careful comparison with Myxocyprinus may show
Amyzon to be closer to that Old \\\jrld representative. Although the
fossil evidence is inconclusive, it seems probable that the Cato-
stomidae arose in southeastern Asia and soon crossed a Bering land
bridge to America, leaving a relict in China, and that in late Pleisto-
Fig. 12. Humpback sucker, Xyraiichen tcxanus, an endemic genus of
the Colorado River s>'stem. (From original drawing by S. F. Denton
(nuchal hump retouched); see Jordan and Evermann, 1900, Fig. 88.)
FRESHWATER FISH FAUNA 203
cene time the North American species Catostomiis catostomus re-
crossed to eastern Siberia. The recency of that crossing is indicated
by the common occurrence, in Siberia and western Arctic America,
of the same subspecies (Walters, 1955, pp. 295-296).
It is rather generally held that the suckers are ancestral to (or at
least more primitive than) the minnows, family Cyprinidae, but a
comparative study of the upper jaw mechanism in the bony fishes
led Eaton (1935, p. 168) to conclude that suckers undoubtedly
descended from minnows. And, after studying skeletal features of
two groups of Asiatic minnows and comparing them to those of
certain catostomids, Ramaswami (1955a, pp. 152-153; 1955b, p.
236; 1957) found certain catostomid skeletal features in members of
the gudgeons, a subfamily of minnows inhabiting China, and con-
cluded: "... it is not likely that the Catostomidae could have given
rise to the Cyprinidae." The weight of present evidence thus indi-
cates (Fig. 11) a cyprinid prototype as probably ancestral to this
family.
The carps and minnows comprise the largest of all freshwater fish
families, the Cyprinidae, with an estimated 250 genera and up-
wards of 2,000 species, inhabiting all the continents except South
America and Australia. The group attains its greatest number of
species and diversity of form in southeastern Asia, where the most
generalized types also are found. Relatively, the family is not very
richly represented nor is it particularly diverse in the New World,
where there are only about 40 genera and 250 species, and the
paleontological evidence indicates that minnows arrived here in
comparatively recent times, not prior to the Miocene epoch. Whereas
a number of distinct subfamilies are recognized in the Old World,
for example in China (Chu, 1935), it is probable that all of the New
World cyprinids belong to a single subfamily, the Leuciscinae
{Notemigonus is possibly a member of the Abramidinae, but its
relationships to that Old World group are in need of critical study).
Not only lack of basic morphological diversity but also the readiness
with which most American minnows hybridize (Hubbs, 1955) sup-
ports the evidence that the group has not been here long enough to
develop strongly divergent lines.
About 27 genera and 58 species of cyprinids live in western North
America. Of the genera 15 (or 56 per cent) are monotypic. Twenty
204
R. R. MILLER
are strictly western In distribution ; another, Gila,"^ has only 4 of its
approximately 13 species living east of the Continental Divide
(Miller and Uyeno, manuscript); 5 {Hybopsis, Hybognathus, No-
tropis, Campostoma, and Pimephales) are clearly recent invaders
from the East; and one {Rhinichthys) is well represented in both
areas, although two-thirds of its species live in the West. The 21
Fig. 13. New World distribution of the minnow family, Cyprinidae.
The extreme northwestern portion of the range is taken from Wynne-
Edwards (1952, pp. 18-19).
genera that are strictly or virtually western may well be autoch-
thonous, but it is clear that the family originated in southeastern
Asia around the close of the Cretaceous. It has been suggested that
there are close relationships between certain western genera and
ones that occur in China and Japan — for example, between Mylo-
* Because of inadequate information about the affinities of this genus, I recognize
Gila, Richardsonius (Fig. 14), and Clinostomus as distinct genera, pending further study
(see Bailey, 1956, p. 331).
FRESHWATER FISH FAUNA
205
pharodon (California), Mylocyprinus and Mylocheilus (fossil, Idaho;
Recent, Columbia River), and Mylopharyngodon (China). The indi-
cated similarities in this series pertain to the common possession of
crushing type (molariform) pharyngeal teeth, an obvious feeding
adaptation subject to independent and repeated evolution through-
out the family. More likely candidates are the western genus Gila
and Tribolodo7i of the Japanese fauna. None of the affinities postu-
lated above has been thoroughly investigated. At the present time,
only one American genus, Gila, is regarded by some as congeneric
with an Old World genus, Phoxinus (see Berg, 1949, p. 571), but I
Fig. 14. Redside shiner, Richardsonius balteatus, of the Columbia
River basin. Fish of this type represent the earliest known fossils of the
Cyprinidae in North America. (From Jordan and Evermann, 1900,
Fig. 105).
do not accept this allocation for reasons already given. The New
World distribution of the Cyprinidae (Fig. 13) indicates that this
family is less tolerant of low maximum temperatures than are
the Catostomidae.
The three secondary families have barely been able to invade the
western fauna from the south and southeast. One species of mojarra
(Cichlasoma beani), of the tropical family Cichlidae, has managed to
reach the Yaqui River; the genus to which it belongs is most speciose
in Middle America, but was derived from a South American ancestor
(Regan, 1906-08, p. xiii). The viviparous topminnows of the family
Poeciliidae, exclusively American and essentially tropical, have
moved a little farther north to the lower Colorado River system,
where they are represented by a single species of Poeciliopsis in
southern Arizona (two species occur in the Yaqui). The egg-laying
killifishes of the family Cyprinodontidae, largely tropical but push-
206
R. R. MILLER
ing well into the temperate region of North America (Fig. 15), have
penetrated Nevada and southeastern and coastal California, where
they are represented by 4 genera and 1 1 species. This group is
Fig. 15. New World distribution of the killifishes, family Cyprino-
dontidae, a secondary freshwater group.
Fig. 16. Railroad Valley springfish, Crenichthys nevadae, a relict
confined to warm springs of the enclosed valley (Fig. 15, south central
Nevada). Another species lives in a former tributary of the Colorado
River and a related genus, Empetrichthys, inhabits the Death Valley
system. (From original drawing by Grace Eager; see Hubbs, 1932.)
FRESHWATER FISH FAUNA 207
dominant in the saline, alkaline, and frequently warm waters of the
Death Valley system (Miller, 1948). Two of the four genera are well
isolated relicts, Crenichthys, Fig. 16 (Hubbs, 1932), and Empe-
trichthys, each with two species, and the two remaining genera
(Fundulus and Cyprinodon) have their closest relatives in southern
United States and northern Mexico. The importance of this sec-
ondary family in indicating past connections of such disrupted
drainages as the Death Valley system has been substantiated by
geological evidence.
CENTERS OF ENDEMISM
In correlation with the physiographic disruption of the West
during late Tertiary and Quaternary times, the fish fauna has
differentiated within a group of isolated basins each with a more or
less high incidence of endemism and generally having few strictly
freshwater species in common (Hubbs and Miller, 1948). Seven
main centers of endemism may be recognized constituting the fol-
lowing drainage systems: (1) Colorado, (2) Sacramento, (3)
Klamath, (4) Columbia, (5) Bonneville, (6) Lahontan, and (7)
Death Valley (Tables I-II; Fig. 1). Not all the fishes inhabiting the
West are included in these 7 systems since there are certain inde-
pendent basins (for example, between the Lahontan and Columbia,
Lahontan and Bonneville, and Lahontan and Colorado systems)
that harbor a few primary species (about 13 in all) unknown else-
where. The faunas of these extralimital systems are discussed later.
Most species that occur in more than one of the seven isolated
drainages belong either to the semi-marine groups (e.g., lampreys,
sturgeons, smelts, most salmonids, and sticklebacks) or are moun-
tain-creek types (such as mountain whitefish, cutthroat trout, and
certain suckers and minnows, particularly the ubiquitous speckled
dace, Rhinichthys osculus). The montane types probably attained
their widespread distribution by means of stream captures, head-
water distributary connections (like Two-Ocean Pass, Wyoming;
Evermann, 1892, pp. 24-28, PI. II), or through stream shifting across
low divides. The distribution of the genera of primary fishes that
are common to a number of the basins (such as the suckers, Cato-
stomus and Pmitosteus, and the minnows, Gila, Ptychocheilus,
Rhinichthys, and Siphateles) probably took place largely in Pliocene
or early Pleistocene times.
208
R. R. MILLER
Colorado River Complex
The primary fish fauna of this basin, including that of the late
Pleistocene tributary White River of eastern Nevada (Hubbs and
Miller, 1948, pp. 95-98), is the richest and has the highest per-
centage of species endemism (87 per cent) of the seven major drain-
ages. Two factors contribute to this: (1) the basin developed as
isolated segments for a long period prior to its formation as the
continuous river we see today ; and (2) it has fewer competing groups
of marine derivation than the three other coastal drainages (Sacra-
mento, Klamath, and Columbia) and about half of these {Elops,
Mugil, Eleotris, Gillichthys) are restricted to the terminal portion of
the river and the others (Prosopmm, Salmo, Cottus) mostly to the
higher headwaters.
The affinities of the fishes vary in different parts of the Colorado.
Cutthroat trout {Salmo clarki), mountain whitefish (Prosopmm
williamsoni, Fig. 17) and sculpins {Cottus bairdi and C. annae), all
confined to the upper portion, have their closest relatives in the
Fig. 17. Breeding male and juvenile of the mountain whitefish,
Prosopium williamsoni, a species of cold, clear mountain streams that has
probably dispersed by stream capture. (From Jordan and Evermann,
1900, Figs. 200, 200a.)
FRESHWATER FISH FAUNA
209
Bonneville and upper Snake (Columbia) drainages. The middle
section, in the vicinity of and including the Little Colorado River and
the ancient White River, holds in common the species of the endemic
cyprinid genus Lepidonieda (Miller and Hubbs, in press). The Gila
River division has 8 endemic species, most of which are likely au-
tochthonous but at least 2 {Cyprinodon and Poeciliopsis) of which
were derived from the east and south, respectively. Except for
headw^ater types, which are identical with or representative of
headwater species of adjacent basins, 71 per cent of its total of 35
species are confined to the Colorado. This bespeaks a long isolation
from surrounding faunas. Only limited faunal exchange has taken
place with the Rio Yaqui (1 sucker and 2 minnows have moved
south from the Colorado and Poeciliopsis has moved northward
from the Yaqui).
Sacramento Complex
The Sacramento-San Joaquin, streams entering Monterey Bay
and San Francisco Bay, and the Russian River and other coastal
streams north to the Mad River are included in this complex. Nine
of the 13 families occurring here contain semi-marine species, and
one {Hysterocarpus traski of the Embiotocidae, Fig. 18) is the only
freshwater representative of an otherwise wide-ranging marine
family. The only native centrarchid west of the Rocky Mountains
survives in the lowland waters but has been greatly reduced from its
'''--^^.
Fig. 18. Tule perch, Hysterocarpus traski, the only freshwater mem-
ber of its marine family (Embiotocidae). (From original drawing by W. S.
Atkinson; see Jordan and Evermann, 1900, Fig. 577.)
210 K. R. MII.I.KR
one-time abundance, presumably through competition with intro-
duced fishes. Sculpins are common (5 species of Cottus and 1 of
Leptocottus) , but suckers are not numerous; minnows have developed
5 endemic genera (in part, perhaps relicts). The fish fauna shows
affinities with each of the surrounding basins, the Columbia (Ptycho-
cheilus, Siphateles) , the Great Basin {Gila, Siphateles), the Klamath
{Cottus), and the Colorado {Ptychocheilus). High endemism (75
per cent) at the species level indicates rather long and effective
isolation for much of the basin. The likely mode of penetration of
Great Basin types was indicated by Robins and Miller (1957, pp.
229-230).
Klamath River
Studies of the geology and ichthyology of this drainage indicate
that the part above Klamath Falls has only recently established an
outflow to the Pacific by the headward erosion of Klamath River;
certain elements of the fauna largely or entirely restricted to the
lakes and streams above the Falls strongly suggest former connec-
tions with the Great Basin (Hubbs and Miller, 1948, pp. 67-68;
Robins and Miller, loc. cit.). Nine genera and 13 species occur above
the Falls, and of these, 8 species {Entosphenus tridentatiis, Salmo
clarki, S. gairdneri, Catostomus snyderi, Gila bicolor, Rhinichthys
osculus, and Siphateles bicolor) have also been reported from below
(Snyder, 1908). Catostomus snyderi and Gila bicolor are known from
single records only but Siphateles bicolor was taken at 3 localities by
Snyder (1908, p. 159, as Rutilus bicolor). On distributional grounds
it is clear that these three species were originally present only in the
upper part of the Klamath basin and gained access to the remainder
of the river by being carried downstream over the Falls. It is likely
Fig. 19. Klamath Lake sculpin, Cottus princeps, a vicarious fresh-
water fish restricted to Upper Klamath Lake, Oregon. (From original
drawing by Anna L. Brown; see Gilbert, 1898, p. 12.)
FRESHWATER FISH FAUNA 211
that Rhmichthys osculus (Agosia nuhila and A. klamathensis of
Snyder) moved in the same direction, since the species does not
otherwise occur south of the Coquille River, Oregon, or north of
the Sacramento River system. Ten genera and 19 species have been
stopped by the Falls; only one of these, Catostomus rimiculus, is a
primary fish (known elsewhere only from Rogue River, Oregon).
Two species of Cottus (C. prmceps, Fig. 19, and C. tenuis) are con-
fined to the Upper Klamath basin. The percentage of endemism at
the species level is lowest in this system.
Columbia Complex
This system, as here expanded to include not only the Columbia
River but also the Umpqua, Malheur, Fraser, Skeena, and Stikine
rivers, is the largest of the centers of endemism (Fig. 1). The Snake
River above American Falls is not included in the complex, as this
part is faunally allied to the Bonneville Basin and received the outlet
of Lake Bonneville. In correlation with its size, the Columbia has
the richest fauna — 15 families, 29 genera, and 57 species. However,
its primary fishes, though including four families, are not as numer-
ous as in the smaller Colorado complex (Table I). The accessibility
of the Columbia to the wealth of marine and semi-marine types ac-
counts for its large total fauna but also is correlated with a relatively
weak primary fauna with specific endemism at about the same level
as that of the Klamath River. A noteworthy element of the fauna is
the richness of the genus Cottus, the Columbia River system alone
containing about 12 species (6 endemic). Salmonoids also are nu-
merous, constituting 6 genera and 13 species, including Thymalliis
arcticus from the Stikine River only and Coregonas clupeaformis
from the Skeena and Fraser rivers (Lindsey, 1956, p. 763).
The primary fauna shows relationships with that of eastern United
States: 4 species occur on both slopes of the Continental Divide
{Catostomus catostomus, Hyhopsis plumbea, Hybognathus hankinsoni,
and Rhmichthys cataractae). Two, Siphateles bicolor and Pantosteus
platyrhynchus, are invaders from the Great Basin. Novumbra huhbsi
and Columbia transmontana are ancient (Miocene?) relicts.
Bonneville System
This is the largest of the Great Basin drainages with about 21
species, 67 per cent of which are endemic (Table II). Included is the
212 R. R. MILLER
Snake River above American Falls, into which Lake Bonneville
overflowed in late Pleistocene times. Excluded from consideration
in the Bonneville fauna, however, are two suckers {Catostomus
catostomus and C. columbiamis) known from the upper Snake (and
elsewhere in the Columbia complex) but absent from the Bonneville
system. These two species are believed to represent part of the origi-
nal Snake River fauna that survived a volcanic deluge which pre-
sumably destroyed the other species during or after the formation of
American Falls but prior to the overflow of Lake Bonneville (Hubbs
and Miller, 1948, p. 30).
Table II. Fishes of the Great Basin
Bonneville.
Lahontan
Other
Death
Family
System
System
Drainages'^
Valley
Primary (I)
Cyprinidae
5 7
4 5
2 5
2 3
Catostomidae
3 5
3 3
2 3
1 1
Secondary (II)
Cyprinodontidae
1 1
2 6
Others
Coregonidae (III)
1 4
1 1
Salmonidae (III)
1 1
1 3
1 1
Cottidae (IV)
1 4
1 1
— —
Totals
5-11-21
5-10-13
4-6-10
3-5-10
% Endemism
Primary (I)
25 67
14 78
78
75
All families
18 62
10 69
70
20 90
" These include basins between Pluvial Lake Lahontan and the Columbia, Bonne-
ville, and Colorado systems (see Hubbs and Miller, 1948, pp. 43-67).
The affinities of the upper Snake and the Bonneville Basin proper
indicate that 5 species {Prosopiiim williamsoni, Salmo clarki, Cato-
stomus ardens, Rhinichthys cataractae, and Cottus bairdi) entered
Lake Bonneville from the Snake River; 4 species {Pantosteus platy-
rhynchus, P. virescens, Gila atraria, and Snyderichthys copei) moved
northward into the Snake; and 3 species {Rhinichthys osculus,
Richardsonius halteatus, and Cottus heldingi) may have moved either
or both ways. Two primary genera {Richardsonius and Chasmistes)
are shared with the Lahontan system and 4 montane species {Pro-
sopium williamsoni, Salmo clarki, Rhinichthys osculus, and Cottus
heldingi) are common to these two drainages. The Lahontan rela-
tionships indicate a former connection, perhaps of Pliocene or early
FRESHWATER FISH FAUNA 213
Pleistocene age, between the Bonneville and Lahontan basins. Three
of the 4 species (mountain whitefish, cutthroat trout, and Cottus
bairdi) shared with the Colorado River are headwater types and
indicate headwater transfers from the Bonneville into the Colorado
(the fourth species, R. osculus, is too poorly analyzed and too wide-
spread to be of much zoogeographic value).
Lahontan System
This isolated basin is second in size of the interior drainages and
second also in the number and variety of its fishes, with 78 per cent
of the primary species endemic (Table II). It has very little of
significance in common w^ith the Colorado River (for example, that
basin lacks Chasmistes, Siphateles, and Richardsonius , and Gila is
absent from the Lahontan basin), but shows afiinities with the
Klamath, Columbia, Bonneville, and Death Valley systems. Unlike
Lake Bonneville, Lake Lahontan had no outlet in late Pleistocene
time and the connections with the surrounding basins were either
of comparatively recent headwater exchanges across existing divides
(whitefish, trout, and Cottus) or more ancient low-elevation trans-
fers, e.g., of Chasmistes (Hubbs and Miller, 1948, p. 40). Black-
welder (1948, p. 12) felt that a mid-Pleistocene outlet of the Lahon-
tan basin to the sea via Pit River into the Sacramento or into the
Klamath, or northward into the Columbia, is a plausible speculation.
Death Valley System
This much disrupted drainage is noteworthy for the lack of
salmonoids and Cottus, the strength of secondary types (6 out of 10
species), and the weakness of the primary fauna (Table II). The
highly saline, often warm, and alkaline waters of a large part of the
system are particularly suited to the family Cyprinodontidae, of
which all the species and 1 of the 2 genera are endemic (Miller, 1948).
That this family has been in the system for a long time is attested
not only by the high degree of endemism but also by the fossil
record (Miller, 1945b) of Cyprinodon and Fundulus from Tertiary
deposits in Death Valley. The endemic genus Empetrichthys was
probably derived from Fundulus.
The faunal relationships point to a former connection to the south-
east, probably in Pliocene time, with what we now know as the
Colorado River, and from the north, with the precursor of Lake
214 K. R. MILLER
Lahontan. Evidently the invasions were not simultaneous since the
movement southward of Siphateles was timed so that this genus did
not become established in the Colorado complex. The hypothesis
that Siphateles (as well as Catostomus and Rhinichthys) entered the
Owens River portion of the Death Valley system from the Lahontan
basin via the Mono Lake basin (Hubbs and A/Iiller, 1948, p. 79) fails
to explain why Prosopium, Salmo, and Cottus, common associates of
Catostomus and Rhinichthys (if not of Siphateles), are absent from
the Death Valley system. The common occurrence of Siphateles
points to an earlier, low-elevation connection such as may have per-
mitted the entrance into the Lahontan basin of Fundulus and
Gasterosteus.
OTHER DRAINAGES
The fauna of the Rio Yaqui, of coastal streams from Baja Cali-
fornia to central California, and of certain isolated waters not in-
cluded in the seven centers of endemism are briefly discussed here.
Yaqui River
The fauna of the Yaqui River of northwestern Mexico is distin-
guished from that of the drainages already discussed by the presence
of a native freshwater catfish {Ictaluriis pricei), a cichlid (Cichla-
soma beani), and a host of tropical fishes of marine derivation
{Dorosoma, Lile, Galeichthys, Centropomus, Dormitator, Trinectes,
etc.). It has the largest number of families, 16, and is second to the
Columbia and Sacramento in number of genera. Only 12 of its 31
species are primary freshwater fishes (Table I). Not included in
the tabulation are Gila ditaenia (Miller, 1945a), of the Rio de la
Concepcion, and Catostomus wigginsi (Herre and Brock, in Herre,
1936), of the Rio Sonora, both independent tributaries of the Gulf
of California lying between the Yaqui and Colorado drainages. The
relationships of the minnow are with Gila purpurea of the Yaqui
and G. orcutti of southern California; those of the sucker have not
been determined.
Seven of the 12 primary species are Rio Grande types, which, it is
plausibly postulated, have entered the Yaqui by stream capture
across the Sierra Madre Occidental (Meek, 1904, p. xxvii). These are
Pantosteus plebeius, Campostoma ornatum, Gila'' nigrescens,'' Notropis
mearnsi, N. ornatus, Pimephales promelas, and Ictalurus pricei. Pre-
FRESHWATER FISH FAUNA 215
cisely when antl where they or their immediate ancestors arrived lias
not been stated. Study of the physiographic map of Mexico pre-
pared by Hoy (1943) and of World Aeronautical Charts 470 (San-
tiago Mountains, 1950, rev. ed.) and 520 (Lake Santiaguillo, 1951,
rev. ed.), shows that capture of a tributary of the Rio Conchos by
the Rio Papigochic (of the Yaqui system) could readily have taken
place about 28 airline miles south of Minaca, Chihuahua. Also,
instead of taking the abrupt horseshoe turn that the Papigochic
now follows northwest of Minaca, this segment of the stream may
formerly have flowed northward to form the headwaters of Rio
Casas Grandes, a stream of interior drainage in Chihuahua. In either
event, Rio Grande types would have been transferred to the Yaqui
fauna.
Three species, Catostomus bernardini, Agosia sp. (near chryso-
gaster), and Gila minacae (= G. robusta; Miller and Uyeno, manu-
script), are the same as or most closely allied to Colorado River
species, and thus indicate entry into the Yaqui from the north. The
2 remaining primary fishes are a sucker (Catostomus) and a minnow
(Gila purpurea). The former, of uncertain relationships, occurs in
the headwaters of both the Yaqui and the Casas Grandes, whereas
the latter, related to G. orcutti and G. ditaenia, inhabits the Yaqui
and Rio Sonora. No genera are endemic and but one species, No-
tropis mearnsi, scarcely distinct from N. formosus of the Rio Casas
Grandes, is regarded as indigenous.
Minor Coastal Drainages
Streams and interior springs from central Baja California north-
ward to San Luis Obispo Creek, California, harbor limited fish faunas
(arbitrarily combined in Table I). Although 12 families are repre-
sented, these comprise only 18 species, of which but 3 are primary
freshwater fishes. One of these, Rhinichthys osculus, is of little
zoogeographic help. Gila orcutti, with its closest relatives in northern
Sonora (G. ditaenia) and in the Yaqui (G. purpurea), evidently came
into southern California from the direction of the Colorado River.
The third freshwater fish, Pantosteus santaanae, is most closely re-
lated to species now inhabiting the Great Basin, whence it pre-
sumably came, perhaps in Pliocene time.
The two secondary fishes, Fmidulus parvipinnis and F. lima, are
the only Pacific representatives of a genus that has its center of
216 R. R. MILLER
abundance in southeastern United States (Miller, 1955), but which
was once more numerous west of the Continental Divide, whence 5
fossil species have been described (Miller, 1945b).
Isolated Basin Drainages
Certain isolated basins lying between the Lahontan, Bonneville,
and Colorado systems harbor a small but interesting remnant fish
fauna (Hubbs and Miller, 1948, pp. 51-67, 73-75).
A group of valleys in northeastern Nevada share a peculiar
Rhi?tichthys-\ike dace, the only native fish in 4 of the 5 basins (Hubbs
and Miller, 1948, Map 1, Nos. 24-28, 30). The southernmost basin
(No. 30), Spring Valley, also harbors a species of Pantosteus, which
is related to species in all surrounding major w^atersheds; the common
ancestor of this sucker probably originated in the Great Basin.
Lying north of the Lahontan basin are the Madeline Plains, site
of Pluvial Lake Madeline (Hubbs and Miller, 1948, Map 1, No. 33).
This region contains but a single fish, Rhinichthys osculus. The
remnant populations show remarkable uniformity and are ap-
parently indistinguishable from the Pit River form, suggesting that
Madeline Plains received its stock from that source (Hubbs and
Miller, 1948, p. 59). A very distinctive chub of the genus Siphateles
occurs in Alvord Valley, mostly in Oregon, and another species of
the same genus is known from Catlow and Guano valleys. Surprise
Valley, in northwestern Nevada, has an endemic sucker as well as
the noncommittal Rhinichthys, and the nearby Warner Valley,
mostly in Oregon, harbors Catostomus warnerensis (endemic),
Rhinichthys osculus, Siphateles hicolor, and was probably inhabited
by Salmo clarki (a Sacramento genus, Hesperoleucus, has likely been
introduced) . Too little is known about the affinities of these species
to enable one to draw reliable conclusions as to their origin.
A number of isolated basins in south central Oregon, lying in the
desert region between the headwaters of Deschutes River and
Malheur Lake, were once united into Pluvial Fort Rock Lake
(Hubbs and Miller, 1948, p. 73). The Recent fauna includes Salmo
clarki, Rhinichthys osculus, and Siphateles hicolor, each of which has
relatives in adjacent watersheds. The fossil occurrence of Pacific
salmon (Oncorhynchus) establishes that the waters of this lake were
once directly connected to the ocean and the physiographic data
indicate that the connection was via Deschutes River. Study of the
FRESHWATER FISH FAUNA 217
fossil minnows and suckers, along with careful comparison of the
living fishes, should help to determine whether the fauna entered
this region by more than one route.
One other well-isolated basin shows a curious faunal mixture.
Railroad Valley, in eastern Nevada, was the site of a large Pluvial
lake (Hubbs and Miller, 1948, p. 90, Map 1, No. 60). The sur\dving
waters contain chubs referable to Siphateles bicolor and an endemic
cyprinodontid, Crenichthys nevadae (Fig. 16). The only other species
of Crenichthys, C. baileyi, is known from the remnants of the adja-
cent Pluvial White River, once a permanent tributary of the Colo-
rado River. Structural troughs lead from Railroad Valley in a
southeasterly direction toward the Colorado River suggesting, along
with the mutual occurrence of Crenichthys, that Railroad Valley
once drained in that direction, perhaps in early Pleistocene time.
Siphateles is particularly characteristic of the Lahontan basin and
presumably entered Railroad Valley from the north after the con-
nection between that valley and the Colorado system was severed.
SPECIES CROSSOVERS BETWEEN EASTERN AND WESTERN
NORTH AMERICA
A study of the extralimital ranges of western and eastern fishes
shows that 29 species have taken part in recent crossings of the Con-
tinental Divide. Possibly some of these transgressions are the result
of human intervention (Lindsey, 1956, pp. 780, 782). These fishes
comprise 23 genera in 9 families, 3 of which are primary. About
twice as many species have moved from east to west as from west to
east; where the crossing was effected by stream capture, this sug-
gests that the western rivers have been the more active in the
piracy. A total of 19 eastern species has entered the Columbia
complex of streams and the Yaqui drainage, whereas only 10 western
species have invaded eastern waters at points from British Columbia
to Wyoming.
Stream capture by the Yaqui River of a drainage that once was
connected with the Rio Grande has given the Yaqui 8 eastern species
(7 primary, 1 secondary) ; except for a Gila and Ictalurus pricei, none
of these is recorded elsewhere on the Pacific slope. The eastern ele-
ment makes up 26 per cent of the total fauna and 58 per cent of the
primary fishes inhabiting the Yaqui. A well-established route of
two-way faunal exchange has taken place between the Snake River
218 R. R. MILLER
(of the Columbia complex) and the upper Missouri River. Moun-
tain whitefish {Prosopium williamsoni), cutthroat trout (Salmo
clarki), and the mountain sucker (Pantosleus) have moved east-
ward; and the longnose sucker {Catostomus catostomus), longnose
dace {Rhinichthys cataractae), and mottled sculpin {Cottus hairdi)
have moved westward. Farther north, the Continental Divide has
been crossed at several points, notably between the upper Fraser or
Skeena basins and the MacKenzie Valley in British Columbia
(Lindsey, 1956), where at least 8 and likely 10 species have crossed
from east to west and 7 species have moved from west to east.
Multiple crossings of the Continental Divide are evident from the
distribution patterns of such western species as Prosopium william-
soni, Salmo clarki, and Salvelinus malma, and of the eastern
Catostomus catostomus and possibly Rhinichthys cataractae. Most
species have not spread far after entering eastern or western waters
but the cutthroat trout, mountain whitefish, and mottled sculpin
(Cottus hairdi), all of which ascend tributaries, have extended their
ranges into isolated basins probably via stream captures, at least in
part. Two northern species are not included in the above discussion
since they are unknown from Pacific streams in the area covered by
this report. Round whitefish, Prosopium cylindraceum, and northern
pike, Esox lucius, have invaded the Alsek River, a Pacific tributary
in extreme northwestern British Columbia, which also contains
Arctic grayling (Lindsey, 1956, p. 789) ; Esox and Thymallus also
inhabit the Taku River, next to the south. Headwater transfer from
the MacKenzie drainage furnishes a plausible explanation of their
limited occurrence on the Pacific slope. Most of these crossings of the
Continental Divide probably took place in Postglacial times, at
least in the northern Rockies, and no crossing is thought to be earlier
than the latter part of the Pleistocene. The identity of most or all of
the now separated species on each side of the Divide supports the
view that the transfers were recent.
CONCLUSION
Of the 21 families of primary freshwater fishes inhabiting North
America (Fig. 1), about 30 per cent of the species are judged to be of
North American origin, 55 per cent of Eurasian ancestry, and 15
per cent of South American affinities. Two relict families, the
Polyodontidae and the Amiidae, with a single species each in eastern
FRESHWATER FISH FAUNA 219
United States, are clearly of northern origin, hut whether Eurasian
or American is problematical. Hence they are not included in the
above estimates. Darters (Etheostomatinae) are considered North
American, but the three other large percids are tentatively assigned
a Eurasian origin.
In western North America there are an equal number of families
of North American and Eurasian origin but the three Eurasian
groups (Umbridae, Cyprinidae, and Catostomidae) account for 97
per cent of the primary fauna. The rather sharp differences between
the western and eastern American fish faunas are of relatively re-
cent origin, probably post-Miocene except for the three old lowland
relicts, Novumbra, Columbia, and Archoplites. Excluding the very
recent. Postglacial eastern invaders, there is an overlap of only about
5 per cent in the total number of species between the two regions.
Acknowledgments
During the approximately 20-year period that I have been studying
western fishes, Dr. Cad L. Hubbs has provided guidance and repeated
stimulation both by encouragement of my work and through our joint
studies. He has also criticized this manuscript. Although I accept full
responsibility for the conclusions here expressed, my indebtedness to him
is considerable. My colleague. Dr. Reeve M. Bailey, has also made valued
suggestions for improving the manuscript and has generously allowed me
to use the map (Fig. 1) which he compiled and which appears here with
only minor modifications. Dr. Leonard P. Schultz kindly arranged for the
use of photographic copies of certain original drawings (Figs. 4, 7, 13,
18-19). Research grants from the Horace H. Rackham School of Graduate
Studies, University of Michigan, made possible much of the field work
that provided the raw data for this report. The maps and charts were
drafted by Mrs. Betty Anthony.
REFERENCES
Bailey, Reeve M. 1956. A revised list of the fishes of Iowa, with keys for
identification, in James R. Harlan and Everett B. Speaker, Iowa
Fish and Fishing. Iowa State Conserv. Comm., 3rd edition, pp. 327-
377.
Berg, Leo S. 1936. The suborder Esocoidei (Pisces). Bull. inst. recherches
biol. Perm, 10: 385-391 (in Russian and English).
— -. 1949. The freshwater fishes of the USSR and neighboring regions.
Acad. Nauk Moscow, 2: 469-924, Figs. 288-674 (in Russian).
Blackwelder, Eliot. 1948. The geological background, in The Great Basin,
with emphasis on Glacial and Postglacial times. Bull. Univ. Utah, 38
(20): 3-16.
220 R. R. MILLER
Chu, Yuanting T. 1935. Comparative studies on the scales and on the
pharyngeals and their teeth in Chinese cyprinids, with particular
reference to taxonomy and evolution. Biol. Bull. St. John's Univ.,
No. 2.
Cope, E. D. 1883. On the fishes of the Recent and Pliocene lakes of the
western part of the Great Basin, and of the Idaho Pliocene lake.
Proc. Acad. Nat. Sci. Phila., 1883: 134-166.
Darlington, Philip J., Jr. 1957. Zoogeography: The Geographical Distribu-
tion of Animals. John Wiley and Sons, New York.
Eastman, Charles R. 1917. Fossil fishes in the collection of the United
States National Museum. Proc. U. S. Natl. Museum, 52: 235-304.
Eaton, Theodore H., Jr. 1935. Evolution of the upper jaw mechanism in
teleost fishes. J. Morphol., 58 (1): 157-172.
Evermann, Barton Warren. 1892. A reconnaissance of the streams and
lakes of western Montana and northwestern Wyoming. Bull. U. S.
Fish Comm., 11 (1891): 3-60.
Gilbert, Charles H. 1898. The fishes of the Klamath River basin. Bull.
U. S. Fish Comm., 17 {1897): 1-13.
Herre, Albert W. C. T. 1936. Notes on fishes in the zoological museum
of Stanford University. IV. A new catostomid from Mexico and a
new callionymid from Celebes and the Philippines. Proc. Biol. Soc.
Wash., 49: 11-14.
Hoy, Harry E. 1943. A new map of the surface configuration of Mexico.
Papers Mich. Acad. Sci., 28 (1942): 441-443.
Hubbs, Carl L. 1932. Studies of the fishes of the order Cyprinodontes.
XII. A new genus related to Empetrichthys. Occ. Papers Museum Zool.
Univ. Mich., No. 252, pp. 1-5.
. 1955. Hybridization between fish species in nature. Syst. Zool.,
4(1): 1-20.
Hubbs, Carl L., and Robert R. Miller. 1948. Correlation between fish
distribution and hydrographic history in the desert basins of Western
United States, in The Great Basin, with Emphasis on Glacial and
Postglacial Times. Bull. Univ. Utah, 38 (20): 17-166.
Hussakof, L. 1916. A new cyprinid fish, Leuciscus rosei, from the Miocene
of British Columbia. Am. J. Sci., 42: 18-20.
. 1932. The fossil fishes collected by the central Asiatic expeditions.
Am. Museum Novitates No. 553, pp. 1-19.
Jordan, David Starr, and Barton Warren Evermann. 1900. The fishes of
North and Middle America. IV. U. S. Natl. Museum, Bull. 47.
. 1902. American Food and Game Fishes. Doubleday, Page and Co.,
New York.
Lindsey, C. C. 1956. Distribution and taxonomy of fishes in the Mac-
Kenzie drainage of British Columbia. J. Fisheries Research Board
Can. 13 (6): 759-789.
. 1957. Possible efi'ects of water diversions on fish distribution in
British Columbia. J. Fisheries Research Board Can., 14 (4): 651-668.
FRESHWATER FISH FAUNA 221
Lucas, Frederic A. 1900. A new fossil cyprinoid, Leuciscus turneri, from
the Miocene of Nevada. Proc. U. S. Natl. Museum, 23: Z3)2)~2>?)A.
Meek, Seth Eugene. 1904. The fresh-water fishes of Mexico north of the
Isthmus of Tehuan tepee. Field Col. Museum Puhl. 93 (Zool. Ser.,
Vol. 5).
Miller, Robert Rush. 1945a. A new cyprinid fish from southern Arizona,
and Sonora, Mexico, with the description of a new subgenus of Gila
and a review of related species. Copeia No. 2, pp. 104-110.
. 1945b. Four new species of fossil cyprinodont fishes from eastern
California. J. Wash. Acad. Sci., 35: (10), 315-321.
. 1948. The cyprinodont fishes of the Death Valley system of
eastern California and southwestern Nevada. Misc. Puhl. Museum
Univ. Mich. No. 68, pp. 1-155.
1955. An annotated list of the American cyprinodontid fishes of
the genus Fundulus with the description of Fundulus persimilis
from Yucatan. Occ. Papers Museum Zool. Univ. Mich. No. 568, pp.
1-25.
Miller, Robert Rush, and Carl L. Hubbs. In press. The spiny-rayed
cyprinia fishes (Plagopterini) of the Colorado River system. Occ.
Papers Museum Zool. Univ. Mich.
Miller, Robert Rush, and Teruya Uyeno. Classification of the cyprinid
fishes of the genus Gila in Mexico and New Mexico (manuscript).
Myers, George S. 1938. Fresh-water fishes and West Indian zoogeography.
Ann. Kept. Smithsonian Inst., 1937, pp. 339-364.
. 1951. Fresh-water fishes and East Indian zoogeography. Stanford
Ichth. Bull., 4 (l):n-2l.
Nelson, Edward M. 1948. The comparative morphology of the Weberian
apparatus of the Catostomidae and its significance in systematics.
/. Morphol., 83 (2): 225-251.
. 1949. The opercular series of the Catostomidae. /. Morphol., 85
(3): 559-567.
Ramaswami, L. S. 1955a. Skeleton of cyprinoid fishes in relation to
phylogenetic studies. VI. The skull and Weberian apparatus in the
subfamily Gobioninae (Cyprinidae). Acta Zool., 36: 127-158.
— . 1955b. Skeleton of cyprinoid fishes in relation to phylogenetic
studies. VII. The skull and Weberian apparatus of Cyprininae
(Cyprinidae). Acta Zool., 36: 199-242.
1957. Skeleton of cyprinoid fishes in relation to phylogenetic
studies. VIII. The skull and Weberian ossicles of Catostomidae.
Proc. Zool. Soc. {Calcutta), Mookerjee Mem. Vol., pp. 293-303.
Regan, Charles Tate. 1906-08. Pisces, in Biologia Centrali- Americana,
Vol. 8.
. 1915. Reptilia, Batrachia, and Pisces, in Biologia Centrah-
Americana, Introd. Vol., pp. 105-117.
Repenning, Charles A., John F. Lance, and Chester R. Longwell. A his-
tory of the Colorado River (manuscript).
222 R. R. MILLER
Robins, C. Richard, and Robert Rush Miller. 1957. Classification, varia-
tion, and distribution of the sculpins, genus Cottus, inhabiting
Pacific slope waters in California and southern Oregon, with a key
to the species. Calij. Fish and Game, 43 (3): 213-233.
Rostlund, Erhard. 1952. Freshwater fish and fishing in native North
America. Univ. Calif. Publ. Geog., 9.
Schultz, Leonard P. 1936. Keys to the fishes of Washington, Oregon and
closely adjoining regions. Univ. Wash. Publ. Biol., 2: 103-228.
Snyder, John Otterbein. 1908. The fishes of the coastal streams of Oregon
and northern California. Bull. U. S. Bur. Fisheries, 27 (1907) :
153-189.
Stirton, R. A. 1936. Succession of North American continental Pliocene
mammalian faunas. Am. J. Sci., 32: 161-206.
. 1939. The Nevada Miocene and Pliocene mammalian faunas as
faunal units. Proc. Sixth Pacific Sci. Congr., 1939, pp. 627-640.
Walters, Vladimir. 1955. Fishes of western Arctic America and eastern
Arctic Siberia. Taxonomy and zoogeography. Bull. Am.. Museum
Nat. Hist., 106: 255-368.
Wynne-Edwards, V. C. 1952. Freshwater vertebrates of the Arctic and
subarctic. Fisheries Research Board Can., Bull. 94, pp. 1-28.
1
Some Problems of Freshwater
Invertebrate Distribution in the
Western States^
Robert W. Pennak
University of Colorado, Boulder
Any brief discussion of the distribution of
free-living freshwater invertebrates of the West (even excluding
insects) is a rather large and difBcult matter, chiefly because of the
great taxonomic and ecological diversity of the many taxa involved
and because of scanty definitive data. For this reason, I shall deal
primarily with a few of the basic problems, and I shall limit myself
largely to generalizations. My remarks are restricted to the Recent
distribution of freshwater invertebrates, other than insects, of the
eleven western states. There are six major points which I should
like to make.
1. The freshwater invertebrate fauna of the West is not well
known. Aquatic biologists are relatively far more numerous in the
eastern half of the United States, where for many years collecting,
identification, and zoogeographical studies have been actively
pursued. To an even more striking degree, our familiarity with the
western freshwater fauna is still farther behind the situation in
Europe, where such studies have produced a remarkably thorough
knowledge of freshwater invertebrates.
Our first point, therefore, is a plea for more field, laboratory,
and zoogeographical work in our West, especially published work.
We hope that, as time goes on, more and more students can be
encouraged to enter these fields of research. Incidentally, we suspect
that a good deal of unpublished information is already hidden away
in field notes, master's theses, and unpublished doctoral disser-
tations.
1 Contribution No. 32, Limnology Laboratory, University of Colorado.
223
224 R. W. PENNAK
2. From a purely environmental standpoint, the freshwater
fauna of the West does not have the advantages of stable flo wages
and many associated large lakes. Western topography is violent and
broken, the climates are highly demanding because of wide annual
variations, and barriers are abundant and rigorous. Many of our
rivers are laden with silt during much of the year, the gradients
are steep, and the water levels sometimes vary from trickles (or dry
beds) in late autumn and winter to rushing torrents during the
spring runoff. Droughts in the West are often extreme and exten-
sive; undoubtedly they are effective in inhibiting or exterminating
local populations. Except in mountainous regions, the West has
relatively few natural lakes, and many of these are small, ephemeral,
and pondlike.
3. We assume that many species of freshwater invertebrates in
the eastern half of the United States could become well established in
western areas, but for several important reasons these eastern
species in certain taxa are apparently prevented from naturally
spreading westward. The following barriers, for example, are un-
doubtedly effective: prevailing westerly winds, the topography and
headwater drainages of the Continental Divide area, steep stream
gradients, intermittent rivers, streams, and ponds, and extensive
deserts and semi-arid regions.
4. Nevertheless, when examined closely, the western states
appear to present a set of conditions that should encourage isolation
and speciation, especially in certain taxa containing macroscopic
forms, and the West should theoretically have a unique population
of freshwater invertebrates. Some of these conditions may be
enumerated briefly, as follows: (a) the abundance of barriers to
gene flow (mountains, deserts, closed drainage systems, variety of
climates, etc.); (b) the abundance of natural and artificial lakes
and springs with peculiar chemistry (alkali lakes, saline lakes,
saline springs, etc.); (c) thermal springs; (d) the generally wide
variety of lakes and streams. Indeed, there is already evidence to
show that the western aquatic invertebrate fauna is much richer
and more varied than is indicated in the literature. Our personal
experience with alkali lakes, thermal springs, and high-altitude
lakes and ponds convince us of this.
Some of the most striking examples of western endemism are to
be found in the arid and semi-arid Great Basin and adjacent regions,
FRESHWATER INVERTEBRATE DISTRIBUTION 225
notably among the stream snails (Pleuroceridae) . Freshwater
shrimps in the Family Atyidae, restricted to a few California coastal
streams, present a further example.
Perhaps it should be pointed out that the West appears to be
lacking in extensive limestone caves and associated underground
stream systems of the sort found in Kentucky, Tennessee, Indiana,
Illinois, Missouri, and Florida. Such habitats are often marked by
unusual endemic aquatic invertebrates. Interesting counterparts,
however, are the occasional western lava-tube caves where a few
unusual forms have been found, e.g., Kenkia (turbellarian) and some
species of Stygobromiis (amphipods). On the other hand, it should
be noted that the West, so far as we know, is lacking in truly archaic
species, such as amphipods, isopods, Bathynella, Troglochaetus,
and Marifiigia, that are so typical of southeastern Europe.
5. Unlike the situation for certain vertebrates and for inverte-
brate terrestrial groups, it is quite clear that the western freshwater
invertebrate fauna involves a zoogeographic situation that is con-
fusing, poorly known, and greatly diverse. Omitting insects and a
few of the minor taxa, however, an assessment or appraisal of this
fauna would seem to indicate five zoogeographic categories, as
follows.
Six taxa are characterized in the West by numerous cosmopolitan
species, most of which produce resting eggs, cysts, and other resis-
tant and dispersal devices that are remarkably effective in sur-
mounting barriers. Protozoa and Rotatoria are typical of this
category and are fairly well known in the West. Four other groups
(Oligochaeta, Tardigrada, Gastrotricha, and Nematoda) are poorly
known, but judging from studies in other parts of the world, we
assume that many common species are widely distributed through-
out the West.
A second category includes five taxa that are not necessarily
cosmopolitan but whose speciation and abundance in the West
are largely unknown. There are a few records of triclad Turbellaria
from the West, but little is known about the rhabdocoels, and we
are greatly in need of studies on pond, alpine, and springbrook
species in this order. Little is known about the Hirudinea of the
West; a good many eastern species, however, have highly restricted
distributions, and a comparable situation may exist in the West.
Of the thirty species of freshwater Porifera in the United States,
226 R. W. PENNAK
only about seven have been reported from the western states;
presumably many of the turbid low-altitude lakes and streams
discourage the establishment of sponges, but very little work has
been done in mountain ponds and lakes that are sometimes fruitful
places for sponge collecting. Only about four species of hydras have
been reported from the West; more intensive collecting should
undoubtly reveal a fauna perhaps even richer than that of the
eastern states. The same situation applies to the Bryozoa; they are
easily transported from one place to another by virtue of their
hibernacula and statoblasts, yet the western species are poorly
known.
A third category includes four taxa that are known to be well
represented in the West; they are also groups in which the lists of
western species will undoubtedly eventually be longer than those
for the eastern portion of the United States. The Cladocera, for
example, are represented by many cosmopolitan species, perhaps
largely owing to the viability and ease of transport of the ephippial
eggs; in addition, a good many species are restricted to certain
habitats in the western states, especially species of Moina, Camp-
tocercus, and Pleuroxus in alkali ponds and lakes. Cosmopolitan
species of cyclopoid and harpacticoid copepods are likewise abundant
in the West; the diaptomids, however, are more interesting because
of their proliferating speciation in western lakes and ponds (the list
of known species is growing markedly); furthermore, even a few
Asiatic and Alaskan species are now being reported from certain
cold-water habitats of the West. Although Ostracoda have been
subjected to relatively little collecting in the West, each new study
turns up numerous cosmopolitan and endemic species; further
systematic collecting should reveal a remarkably large fauna. The
same is true for the Hydracarina, especially in view of the experience
of European specialists; the little collecting already done in the
western states is ample evidence that it is an area rich not only in
cosmopolitan but also in endemic species, as one might assume in
view of the wide variety of isolated aquatic habitats.
A fourth category includes five large taxa that are poorly rep-
resented in the West. It is, for example, remarkable that this region
contains relatively few gastropods, especially as compared with the
very rich fauna of the Mississippi drainage area. To be sure we have
an interesting assemblage of isolated genera and species in such
FRESHWATER INVERTEBRATE DISTRIBUTION 227
areas as the Great Basin, including Panipholyx, Carinijex, and
Fluminicola, but these do not constitute a large fauna. The Pele-
cypoda (exclusive of the Sphacriidae) are very poorly represented
west of the Continental Divide; for example, only about six species
of unionids are native to California. One of these, Margaritifera
margaritifera, is widely distributed in the western states but also
occurs in the North Atlantic states. But presumably the great
unionid population of the Mississippi Valley has never been success-
ful in overcoming the difficulties of the Divide, sandy and silty
rivers, and the intermittent nature of many western streams.
Undoubtedly a further problem in the West is the lack of proper
fish hosts for the glochidia stages of unionids. Isopoda and Amphi-
poda are apparently poorly represented in the West, although most
of the few species found there are endemic; the relative abundance
of species in the eastern states is probably a reflection of speciation
in springs and subterranean waters. Freshwater crayfishes were
originally represented by only five species of Astacinae west of the
Continental Divide, and this same subfamily is represented else-
where only in northern Europe and eastern Asia, by about ten
species. The Cambarinae, however, which are so abundant east of
the Continental Divide, have, in Recent times, apparently never
been successful in spreading westward from their centers of dispersal
and speciation in Mexico and the south-central and south-eastern
parts of the United States. It is, of course, entirely possible that
the Cambarinae inhabited the western states area in pre- Pleistocene
times.
A fifth and last category includes three small groups that are
especially characteristic of the West and that are also abundant in
comparable geographic and climatic areas elsewhere in the world.
These are the Anostraca (fairy shrimps), Conchostraca (clam
shrimps), and Notostraca (tadpole shrimps). All are far better
represented in the West than in the eastern half of the country.
Two peculiarities of these groups are perhaps primarily responsible
for their occurrence here. First, they produce an abundance of
highly resistant, thick-shelled eggs that are able to withstand
extremely unfavorable conditions for long periods. Second, many
species are adapted to living in unusually saline, alkaline, and
silty bodies of water. Permanent and vernal ponds and pools
throughout the West thus afford ideal conditions for these phyllo-
228
R. W. PENNAK
pods, and although they are usually considered more typical of the
Great Plains, they are just as characteristic of suitable mountain and
desert habitats west of the Divide.
Table I. Systematic and Zoogeographic Status of Certain Groups of
Freshwater Invertebrates in the Western Portion of the United States
Groups
containing
preponder-
With
ance of
high
species wide-
percentage
Western
spread in the
of endemic
status
United
species
largely
States
in West
unknown
Protozoa
West relatively
X
Rotatoria
rich in species
X
Oligochaeta
?
Gastrotricha
?
Tardigrada
X
Nematoda
?
Eubranchiopoda
X
Hydracarina
X
Ostracoda
X
Copepoda
?
?
Cladocera
?
■i
Turbellaria
X
Hirudinea
X
Gastropoda
X
Bryozoa
X
Porifera
X
Coelenterata
X
Amphipoda
X
Isopoda
>
'■
X
Decapoda
West relatively
X
Pelecypoda
poor in species
X
Certain of the generalizations thus far discussed are summarized
in an alternate fashion in Table I. The twenty-one taxa in the
first column are listed in order of their decreasing relative species
abundance in the West (particularly as compared with the situation
in the eastern half of the United States). The first five taxa comprise
a group characterized by a preponderance of cosmopolitan species,
FRESHWATER INVERTEBRATE DISTRIBUTION 229
even though definitive data are lacking for the Oligochaeta, Gas-
trotricha, and Nematoda, and their inclusion here is based on
information gathered primarily from European sources. The next
five taxa of crustaceans form a natural group featured by a high
percentage of endemic species in the West (with the possible ex-
ceptions of the Copepoda and Cladocera). The following six taxa
are a heterogeneous group which, with the exception of the Gastro-
poda, are poorly known in the West, chiefly because of the lack of
intensive and systematic collecting. The last four taxa listed in
the first column are all relatively poor in species in the West, but
nevertheless most of the species found there are endemic.
6. The last point I should like to make is concerned with the
increasingly important role being played by man in the distribution
of freshwater invertebrates in the West. Residents of California,
for example, are well aware of the nuisance and economic importance
of cambarine crayfishes that were intentionally introduced here
many years ago. In Colorado we are seeing the same process,
although the end results will probably not be so serious; cambarine
crayfishes have been introduced into certain Colorado mountain
lakes, and in some such habitats they have become abundant and a
welcome addition to the trout diet. In addition, however, they have
been introduced into the Western Slope drainages, and in a few
irrigation ditches they are occasionally a nuisance because of their
burrowing habits.
Aquarium enthusiasts are often responsible for setting up new
centers of distribution for both bivalve and univalve mollusks.
Many species native to the eastern states are well adapted to home
aquarium use, and, of course, these are commonly shipped west as a
part of the thriving aquarium business. Frequently, however,
when the hobbyist is tired of his aquarium, he empties it into the
nearest pond or lake, and we may thus have a new mollusk popul-
ation established under natural conditions.
Fishermen are consciously accomplishing the same ends. We
have seen fishing parties from Nebraska, for example, bringing
milk cans full of vegetation and the associated invertebrates to
Colorado. These they commonly empty into mountain lakes on
both sides of the Continental Divide. Furthermore, state fish and
game departmants frequently do exactly the same thing when
they transport large quantities of invertebrates and vegetation from
230 R. W. PENNAK
one "rich" lake to another "poor" lake. Over a period of time these
activities will undoubtedly assume considerable importance in
spreading various invertebrates over wider areas of the West.
A further and unintentional means by which aquatic inverte-
brates are greatly increasing their ranges and abundance is through
the extensive system of thousands of farm ponds and stock tanks
which have been constructed in the West, especially during the
past twenty-five years. In areas formerly characterized by great
stretches of unbroken arid or semi-arid land, we now have an
extremely effective system of "stepping stones" by which inverte-
brates may disperse much more effectively than was the case many
years ago. This is no exaggeration. Anyone who will take the trouble
to examine the invertebrate population of a stock tank or ranch
pond in the middle of a large semi-arid tract is bound to be impressed
with the abundance of species occurring there. (Incidentally, this
facet of aquatic biology seems to have been completely neglected.)
During the past seventy years the West has become densely
criss-crossed with an extensive system of irrigation ditches, many of
them carrying water at all times of the year. Such ditches connect
with a host of artificial irrigation reservoirs. In our estimation,
these waterways also provide an enormous transportation and
dispersal system by which our aquatic invertebrates are becoming
much more generally distributed.
Affinities and Origins of the Northern and Montane
Insects of Western North America
Herbert H. Ross
Illinois Natural History Survey, Urbana
1 he subjects of this paper are the insects
belonging to the cool-adapted biota and occupying an ecological
band comprising essentially the cool-temperate and arctic regions.
The arctic region comprises both the tundra of the Arctic and the
alpine tundra found above timberline in subarctic areas. The cool
temperate region comprises the taiga and its equivalents — the
northern coniferous spruce and pine forests and various higher-
elevation forests toward the south. In North America today this
double band — cool temperate and arctic — extends in a wide swath
across roughly the northern third of the continent and extends
southward as islands at higher and higher elevations, through the
mountain chains of eastern and western America. In the West these
cool-temperate islands are larger and occur much farther south than
in the eastern part of the continent.
A large number of insect species are abundant in both taiga and
tundra, and are almost entirely restricted to these two major
ecological formations. These insects represent many orders and
families, including such well-known types as caddisflies, sawflies,
and mosquitoes. Although today these many species of various
families form what appears to be a closely knit ecological aggre-
gation, they must have arrived in this general area of the continent
by diverse paths and at different geologic times.
Concerning this cool-adapted biota of western North America,
we can deduce that some elements arrived from Asia, that other
elements spread westward from the eastern parts of North America,
and that still others spread northward from the more tropical
areas to the south. Present information gives evidence of dis-
persals of living genera dating from Cretaceous time to practi-
231
232 H. H. ROSS
cally the present. Undoubtedly dispersals between the same areas
occurred many times, each time involving different ecological
conditions in the bridging area and resulting in the spread of differ-
ent lines of insects having corresponding ecological adaptations.
We know far too little concerning this historic process, however,
to be able to detail the spread of all the insect species in these
northern communities, or even that of the plants and other animals.
Because fossils of northern insects are rarities, we must rely
chiefly on the biogeographic analysis of living species in delving
into the past history. Two sets of facts constitute the backbone of
such an analysis, first, the morphological characters of the species
Fig. 1. A Baltic Amber caddisfly: right, Lype sericea and left, one of
its living counterparts, the European Lype phaeopa. (From Ulmer, 1912,
and Mosely, 1939.)
on which phylogeny is based, and then the known geographic
distribution of the species from which the dispersal pattern may be
deduced. When present, fossil evidence is a welcome and valuable
adjunct to these data.
One fact of inestimable importance in attempts at phylogenetic
reconstruction is deduced from the fossil record, namely that in
some insect lines evolutionary change may be very slow. The
caddisfly genus Lype is represented in both the Baltic Amber
(probably deposited no later than upper Eocene) and present day
biotas. One of the Baltic Amber species is almost identical in
diagnostic characters of the male genitalia with a species existing
today (Fig. 1), and only slight differences can be detected between
these populations some 50 million years apart in time. In this slow
rate of evolutionary change found in some of their phyletic lines,
the insects resemble the freshwater Pelecypoda and certain other
INSECTS OF WESTERN NORTH AMERICA
233
invertebrates and contrast sharply with the rapid evolutionary
rates described as characteristic for many groups of Mammalia.
PREHISTORIC FAUNAL ELEMENTS
Fossil records show that many insect genera occurred previously
in western North America but are now absent from the area.
Examples from the cool-adapted biota include the fern-boring
Fig. 2. The phylogenetic tree of the caddisfly genus Wormaldia
subgenus Doloclanes superimposed on the known distribution of the
species. This subgenus may be most closely related to more primitive
Baltic Amber species.
sawfly Blasticotoma, known only from fossil remains in the Flor-
issant shales of Colorado and from living representatives in Europe
(Benson, 1942) ; and the snakefly genus Raphidia, known also from
the Florissant shales but not now occurring in North America
(Carpenter, 1953). Since representatives of the caddisfly genus
Phylocentropus are now known only from Baltic Amber fossils and
from living species restricted to eastern North America, intervening
areas must have been populated by this genus at some past time.
Because considerable evidence indicates that the intercontinental
connection was between northwestern North America and north-
234
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INSECTS OF WESTERN NORTH AMERICA 235
eastern Asia, it is plausible to assume that this genus and others of
similar range characteristics were former denizens of the American
Northwest.
A few cases drawn entirely from the distribution of living forms
give practically conclusive proof of the same phenomenon. An
example is the subgenus Doloclanes of the caddisfly genus Wormaldia
(Ross, 1956). The main group of species involved in this subgenus
evolved in and is now restricted to the eastern part of Asia (Fig.
2), but one species (most closely allied to one in Japan) occurs in the
Great Smoky Mountains of eastern North America. The only
logical explanation for this set of circumstances is that a northeastern
Asiatic species spread across North America and ultimately became
established in the Smoky Mountains. During this dispersal, we
must assume that a species of Doloclanes lived in northwestern
North America, although we have no definite records for this
subgenus there.
Some insect fossils from western localities represent highly
specialized genera not known from living species and undoubtedly
have become extinct. The existence of such extinct "side branches"
of phylogenetic trees cannot be deduced from the study of living
forms, hence how many of them existed in the past we do not know.
PRESENT INHABITANTS OF THE WEST
The oldest dispersals of northern insects involved in the origin
of the present western North American fauna for which we have
evidence seem to have been in middle Cretaceous. It may be in-
ferred that the caddisfly genus Sortosa dispersed at that time to
almost every continental land mass and that after this great spread,
many populations of Sortosa became isolated in and persisted in
various parts of the world. In western North America five species,
comprising the subgenera Sisko and Fumonta, represent this old
movement (Fig. 3). It is highly likely that several archaic western
genera of limnephilid caddisflies, including Dicosmoecus, Ecclisomyia,
Farula, and Pedomoecus, also are surviving lines dating back to this
same mid-Cretaceous dispersal (Schmid, 1955). All five of these
caddisfly genera frequent streams in the extreme north or at higher
elevations in mountains.
Judged from their known present distributions, most of these north-
western genera or subgenera have either remained isolated in moun-
236
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INSECTS OF WESTERN NORTH AMERICA 237
tain regions of western North America since the time of this supposed
mid -Cretaceous dispersal, or if they did spread to other areas have
become estabUshed in no other region. This situation suggests
that for survival these insects must have streams which are not
only cold but rapid, and that in the past greater continuity of
mountainous terrain was a major factor in permitting their dispersal.
Evidence is highly suggestive that during the height of the
Laramide orogeny, that is, the very end of Cretaceous and the
earliest part of Cenozoic, many members of the cool-adapted biota
spread between western North America and Asia. The mountain-
inhabiting caddisfiies offer evidence for this dispersal also. The
genus Wormaldia, which could very well have evolved from a
Cretaceous subgenus of Sortosa isolated in western North America,
probably spread in Paleocene into Asia and across to Europe.
Whichever way the dispersal occurred, it antedated the Baltic
Amber (in which Wormaldia occurs) and is documented by clusters
of Wormaldia species in many continental areas (Fig. 4). One
cluster of nine species occurs in western North America. It may be
postulated that members of two other caddisfly families dispersed
in similar fashion at this same time. The genus Rhyacophila,
belonging to the family Rhyacophilidae, is one of the largest and
commonest mountain caddisfly genera of the West. Of its 44 species
groups, 19 occur in the West but 7 are known also from other
areas. It is almost certain that the ancestors of the other 12 groups
either reached the West no later than Paleocene or evolved in the
mountains of western North America from older parental forms.
The same may be true also of certain of those seven groups that
now occur in two or more major areas.
In the family Glossosomatidae (the caddisfiies whose larvae
construct saddle-like cases) both the archaic genus Anagapetus and
the subgenus Ripaeglossa of Glossosoma appear to have had similar
early histories. It is impossible to be sure whether the ancestral
forms of these groups arose in Asia or North America, but wherever
they did originate, they dispersed between the two continents at
some early date. In western North America a remnant of each line
appears to have evolved in, and to have been restricted ever since
to, the higher elevations of this area (Fig. 5).
The next dispersals of cool-adapted insects for which we have
238
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of small caddisflies restricted to western North America. (From Ross,
1956.)
INSECTS OF WESTERN NORTH AMERICA 239
plausible evidence occurred in mid-Cenozoic and involved chiefly
species which may be considered ecologically as forming the warmer
fringe of the cool-temperate biota. The best evidence involves tree-
feeding leafhoppers of the genus Erythroneiira and caddisflies of the
genera Pycnopsyche, Agapetus, and the more warm-adapted
species of Rhyacophila, which presumably became widespread
across North America and Eurasia along with the temperate
deciduous forests of that era. Most of these insect examples had a
greater eventual effect on the fauna of eastern North America than
on that of the West, and established nuclei for groups that became
important elements of the eastern temperate deciduous forest.
Certain of these mid-Cenozoic dispersals did apparently result
in colonizations that evolved into species flocks in the West compara-
ble with those that evolved in the East. The best examples with
which I am acquainted are the sawfly genus Neodiprion and the
caddisfly genus Agapetus. We do not know where the ancestral
form of Neodiprion (Fig. 6) arose, but it seems obvious that an
eastern and a western population became established, that each
evolved into a distinctive species flock, that each now constitutes
an important element in the conifer-inhabiting insect fauna, and
that the eastern and western branches of the genus have remained
separate geographically until almost the present time (Ross, 1955).
A comparable situation may be postulated for the American
species of the caddisfly genus Agapetus. The larvae of these species
construct saddle-like cases and inhabit clear, cool, spring-fed streams
in hilly and mountainous country throughout the Allegheny system
in the East and much of the western montane region south of
Canada. Available evidence, based on characters of venation and
abdomen, indicates that the North American species arose from an
Asiatic ancestor which spread into North America at the time of the
Holarctic temperate deciduous forest. The present day North
American species of Agapetus appear to constitute two primary
phyletic branches, one in the East and one in the West. Each branch
has evolved into a moderate cluster of species, many of which
exhibit striking changes compared with more primitive forms.
This combination of phylogeny and distribution suggests that when
the American transcontinental temperate deciduous forest broke up
in mid-Cenozoic into widely separated segments, one segregate of
Agapetus persisted in the East and one in the West. There is no
240
H. H. ROSS
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INSECTS OF WESTERN NORTH AMERICA
241
evidence that the two resulting phylogenetic lines ever again
mingled geographically.
In addition to these mid-Cenozoic events which can be linked
ecologically with temperate forest dispersals, we have evidence of
other intercontinental dispersals of cool-adapted insects that are
difficult to date. An example (Ross, 1956) is the deduced dispersal
of the caddisflies belonging to the Rhyacophila sibirica group (Fig.
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Fig. 7. Phylogenetic dispersal chart of the Rhyacophila sibirica group,
comprising caddisflies restricted to rapid, cold streams. (From Ross, 1956.)
7). Its main evolutionary lines seem to have oscillated between
northwestern America and northeastern Asia, with many surviving
species in both areas. The distribution of these chiefly northern
montane species indicates the possibility of some interchanges in the
northern elements of our western cool-adapted biota at moderately
frequent intervals during the Cenozoic. For other groups of montane
caddisflies of indicated Asiatic origin, a single line seems to have
spread to and to have become established in western North America.
Examples are Himalopsyche phryganea (Fig. 8), Glossosoma penitum,
and the entire Rhyacophila acropedes complex. Beacuse each line
242
H. H. KOSS
offers evidence of only one Intercontinental dispersal, it is impossible
to approximate the date of arrival of these lines in North America.
We should not forget that during this Cenozoic period many
lines were almost certainly already present and evolving in the
cooler habitats of western North America. In the montane caddisflies
some of these lines apparently remained in the area (e.g., the
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Fig. 8. Phylogenetic diagram of the caddisfly genus Himalopsyche.
Note that all the species occur In Asia except the one shown at the extreme
left, phryganea, which represents the only known dispersal of the genus
into North America. (From Ross, 1956.)
Rhyacophila verrula and vagrita groups), whereas others (Fig. 9)
seemingly gave rise to species that spread into eastern North
America, e.g., the Rhyacophila invaria and Carolina groups, or into
Eurasia, e.g., the Rhyacophila glareosa and pepingensis branches.
The climatic and geologic changes in late Pliocene and the
Pleistocene are associated with what appears to have been a whole-
sale redispersal of many cool-adapted insects throughout the Hol-
arctic region. This phenomenon is especially well illustrated in the
INSECTS OF WESTERN NORTH AMERICA
243
sawflies. The predominantly northern genera Dolerus, Nematus,
Amauronematiis, Rhadinoceraea, and many others have entire
complexes within which all western North American species either
are Holarctic or have a sister species in Eurasia. It is obvious in
these cases that probably during the immediate past either an
existing species or its immediate ancestor became widespread
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Fig. 9. Phylogenetic dispersal chart of several species groups from one
of the distinctive branches of Rhyacophila, comprising caddisflies which
inhabit cold, rapid rivers and streams. (From Ross, 1956.)
across the Holarctic region. The same situation is shown graphically
by evidence from the herb-feeding leafhopper genus Macrosteles
(Moore and Ross, 1957). The present distribution of known species
of this genus can plausibly be explained only by the intercontinental
dispersal of at least sixteen phylctic lines (indicated by black dots
on Fig. 10). These sixteen movements were of course not all con-
temporaneous, but judged by the uniform morphological similarity
of many pairs of sister species, at least the upper thirteen dispersals
244
H. H. ROSS
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INSECTS OF WESTERN NORTH AMERICA 245
indicated in Fig. 10 were relatively recent and without much doubt
within the late Pliocene-Pleistocene period. Similar circumstances
prevail in many genera of northern grass-feeding leafhoppers and
also, I am sure, in a large number of other insects abundant in the
North and Northwest. In Culicoides, an extremely widespread
genus of biting flies, Khalaf (1954) found evidence of even wider and
relatively recent dispersals, some indicating a total spread including
central and northwestern North America, Asia, Europe, and Africa.
Two Alaskan species, Culicoides obsoletiis (Meigen) and C. tri-
striatidus Hoff, belong to such widely ranging complexes.
In addition to these intercontinental movements, dispersals
from the eastern to the western areas of the continent are illustrated
by insects. Although there is abundant evidence that members
from many western species flocks spread to and colonized the East
at various times in the Cenozoic, present information indicates
that dispersals to the West from eastern species flocks were much
rarer and occurred chiefly in the Pleistocene. Of the seven older
eastern species flocks in the caddisfly genus Rhyacophila, none has
apparently spread to the West. Some other caddisflies do indicate
such a dispersal. In the genus Triaenodes nineteen species form a
fairly old, distinctive, polyphyletic complex which appears to
have evolved in the eastern deciduous forest area as a series of
species flocks (Fig. 11). Seventeen of these nineteen species are still
restricted to the East and Northeast (Fig. 12), but two, baris and
tarda, extend westward into the Rocky Mountain region.
Because no morphological differences have been detected between
eastern and western populations of the two species just mentioned,
the most logical interpretation is that they evolved originally in the
East and spread to the West along ecological corridors brought into
existence by Pleistocene events. An alternative logical possibility
is that the progenitors of tarda and baris spread from the East to
the West, that the western populations of each became isolated
and evolved into distinctive species, and that these two species in
turn spread eastward during Pleistocene. The restricted western
distribution and extensive eastern range of T. tarda, however,
strongly suggests that it was of eastern origin.
Several species of the related genus Athripsodes, notably cancell-
atus and tarsipunctatus, exhibit parallel phenomena and may also
represent recent dispersals from the East to the West. It is quite
246
H. ir. ROSS
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^-short opodeme
^-long closper
Fig. 11. Phylogenetic diagram of the North America components of
the case-making caddisflies belonging to the genus Triaenodes.
possible that comparable information on other insect groups will
add greatly to these examples.
The sum of the Holarctic and trans-American dispersal patterns
points to a truly extensive faunal interchange associated with the
colder climates of the Pleistocene.
The American species of the caddisfly genus Helicopsyche il-
lustrate another type of range extension into the cool-temperate
world. The larvae of Helicopsyche live in small clear streams and
make strong cases shaped like snail shells. All fourteen described
species occur in the tropical and /or subtropical regions and three of
them extend northward into the temperate region (Fig. 13). For
two species, these extensions are slight or small: H. mexicana has
outpost populations in central Arizona, northern New Mexico, and
Arkansas, and H. vergelana has an outpost in western Louisiana.
The species borealis, however, extends northward into the cool-
temperate zone, reaching Washington in the West and Quebec in the
East. Thus H. borealis has in some manner acquired an ecological
tolerance much wider than that of other members of the genus, and
INSECTS OF WESTERN NORTH AMERICA
247
Fig. 12. Known distribution of certain North American species of
the caddisfly genus Triaenodes. The category "other species" includes
all those except tarda and haris listed between tridonta and furcella in
Fig. 11.
248
H. H. ROSS
Fig. 13. Distribution of Helicopsyche horealis and the six other species
belonging to the same phylogenetic branch. The species limnella, known
only from Arkansas, is so close to mexicana morphologically that it is here
considered as merely an outpost colony of mexicana.
INSECTS OF WESTERN NORTH AMERICA
249
thereby has effected an intrusion of a predominantly subtropical
group into the cool temperate belt. There is in these data no sugges-
tion as to when this extension of range developed, but the lack of
formation of distinctive northern species in the group suggests
that it occurred relatively recently.
Adding together the known data concerning cool-adapted insects,
one gets the definite impression that at three points in geologic
o
o
a.
E
25
20
15
10
CRETACEOUS
CENOZOIC
PLEISTOCENE
Fig. 14. Suggested temperature trends during the latter part of
Cretaceous and Cenozoic time, combining data for the Cretaceous from
Lowenstam and Epstein (1954), the Cenozoic from Durham (1950), and
the Pleistocene from Emiliani (1955). These authors stress that the values
represent trends and should not be construed as indicating absolute
climatic measurements.
time — middle Cretaceous, Paleocene, and Pleistocene — conditions
were such that extensive dispersal of cool-temperate forms took
place. Various estimates of temperature trends during Mesozoic
and Cenozoic agree closely (Fig. 14), but they indicate that periods
of widespread cool conditions were of relatively short duration.
During the long intervening periods when warmer climates prevailed
over the lowlands, we must presume that the cool-temperate biota
existed in higher elevations in the montane regions. Two sets of
data from the western region of North America fit well into such a
hypothesis.
1. The relatively flat portions of the present day northern tundra
250 H. H. ROSS
and coniferous forests are sufficiently extensive to have an air of
permanence. If, however, they were stable features of the landscape,
geologically speaking, one would expect some distinctive taxonomic
units to have evolved, and remained, therein. Among the insect
groups of my acquaintance, the species of the flat north country are
either the same as those in the western or eastern mountains, or
were obviously derived relatively recently from montane species.
It appeared at one stage in our studies that case-making cacldisflies
belonging to the Limnephilus suhlunatus complex might be a species
flock which had evolved in the flat northland. Most of the earlier
records for many species in this group were from northern Sas-
katchewan, the Mackenzie River Delta, and Great Slave Lake.
More recent collections from Yukon and Alaska emphasize the
possibility that the Limnephilus sublimatus complex may be associ-
ated historically with the northern ranges of the Rocky Mountains
rather than with the flatter country.
2. The two main areas of caddisfly distribution in the mountains
south of Canada, the Cascade-Sierra Nevada area to the west and
the main Rocky Mountain area to the east, are separated by an
irregular strip of arid, less mountainous country, including the
Great Basin. This pattern is illustrated by the distribution of those
caddisflies of the genus Glossosoma that comprise the subgenus
Ripaeglossa, which abounds in large, fast, clear streams in both
areas. The sixteen species of Ripaeglossa form two major phyletic
branches. The branch comprising the alascense and traviatum
species groups apparently evolved primarily in the western ranges
and the one comprising the parvulum species group evolved in the
eastern ranges. At the present time the northern six of the sixteen
species of Ripaeglossa extend around the northern end of the arid
zone separating the two mountain areas, but no phyletic line appears
to have divided into sister species in the area to which it spread
(Fig. 15). From these data it is possible to reconstruct a plausible
series of events. When the progenitor of all existing forms of Ripae-
glossa lived, clear mountain rivers of the West formed a sufficiently
well-connected system to allow this caddisfly to spread throughout
the West. Increased aridity of the Interior Basin area broke this
river network and split the ancestral Ripaeglossa species into well-
separated eastern and western populations. This same condition
presumably prevailed during the entire subsequent evolution of
INSECTS OF WESTERN NORTH AMERICA
251
these two populations. Only in comparatively recent times have
shifts in climates or topography produced conditions under which
northeastern species of Ripaeglossa spread westward and north-
western species eastward. This and other similar examples of
caddisfly distribution indicate that in these mountain areas Pleisto-
Eostern Ranges
White, Wosotch, Rockies, etc.
^LARAMIE BREAK
SO-CEN
ARIZ NM COLO WYO UT WYO MOM IDAl
Western Ranges
Coscodes, Sierra Nevado, etc.
CALIF
^CALIFICA
WENATCHEE
PTERNA
ALASKA
Fig. 15. Phylogenetic dispersal chart of Glossosoma subgenus Ripae-
glossa, a group of caddisflies inhabiting cold, rapid rivers and confined
to the mountainous area of western North America. (From Ross, 1956.)
cene events effected a mixing of phyletic lines previously separated
from each other for long periods.
In exploring the origin of the cool-adapted western insect fauna
we have surveyed data from only a small fraction of the insects
that occur in the cooler parts of the West. It is noticeable, however,
how most of the data fits readily into the concept of an almost
cyclic alternation of brief dispersals and long separations. The many
small but different types of evidence pointing in the same direction
give us reason to visualize an extensive dispersal and intermingling
252 H. H. ROSS
of cool-adapted phyletic lines during mid-Cretaceous, a similar
series of events occurring again during Paleocene, and a third
extensive set taking place in the Pleistocene. At each time the
details of the dispersals were different. Finding out more about
these details is proving a challenge to our investigations. Each
dispersal, however, crossed or crisscrossed the West and had a
tremendous effect on its cool-adapted fauna. In their total action
these three cool-dispersal periods, with long intervening periods of
chiefly local movement, were the most important events determining
the composition of the present northwestern fauna.
REFERENCES
Benson, Robert B. 1942. Blasticotomidae in the Miocene of Florissant,
Colorado (Hymenoptera: Symphyta). Psyche 49: 47-48.
Carpenter, F. M. 1953. The geological history and evolution of insects.
Am. Scientist 41: 256-270.
Durham, J. Wyatt. 1950. Cenozoic marine climates of the Pacific Coast.
Bull. Geol. Soc. Am. 61: 1243-1264.
Emiliani, Cesare. 1955. Pleistocene temperatures. /. Geol. 63: 538-578.
Khalaf, Kamel. 1954. The speciation of the genus Ciilicoides (Diptera,
Heleidae). Ann. Entomol. Soc. Am. 47: 34-51.
Lowenstam, H. A., and S. Epstein. 1954. Paleotemperatures of the Post-
Aptian Cretaceous as determined by the oxygen isotope method.
J. Geol. 62: 207-248.
Moore, T. E., and H. H. Ross. 1957. The Illinois species of Macrosteles,
with an evolutionary outline of the genus (Hemiptera, Cicadellidae).
Ann. Entomol. Soc. Am. 50: 109-118.
Mosely, Martin E. 1939. The British Caddis Flies (Trichoptera). George
Routledge & Sons, Ltd., London.
Ross, H. H. 1955. The taxonomy and evolution of the sawfly genus
Neodiprion. Forest Sci. 1: 196-209.
. 1956. Evolution and Classification of the Mountain Caddisflies.
University of Illinois Press, Urbana, 111.
Schmid, F. 1955. Contribution a I'etude des Limnophilidae (Trichoptera).
Mitt, schweiz. entomol. Ges. 28: 1-245.
Ulmer, Georg. 1912. Die Trichopteren des baltischen Bernsteins. Beitrage
zur Naturkunde Preussens, Konigsberg 10.
i:
The Origin and Affinities of
the Dermaptera and Orthoptera of
Western North America
James A. G. Rehn
Academy of Natural Sciences of Philadelphia,
Pennsylvania
r or the greater part of a half century the
assembly of data and evidence bearing on the fields of this symposi-
um, as relating to the Dermaptera and Orthoptera of North America
as a whole, has been a major objective of a group of colleagues now
or formerly associated with my institution. The evidence here
summarized has been drawn largely — and particularly for the
United States — from field investigations personally carried on over
a period of fifty-five years.
Much of the past literature, and considerable past collecting, is
not at all helpful. However, very definite and clear-cut conclusions
are now emerging, as extensive collections, representing many
seasons of fully documented field work, are being critically studied
as part of a long-range project assisted by a National Science
Foundation grant. The general results, systematic, zoogeographic,
and binomic, are now being made known in a series of papers
preliminary to a more condensed monograph. In view of these
circumstances citations to the literature have been omitted in this
paper.
In the present analysis of the subject I am assuming a full under-
standing of the terminologies that have long been in general use
for life areas, particularly by the vertebrate school, which in North
America produced some of the zoological pioneers in biogeography ;
also that the descriptive terms, based on physiographic areas, such
as Cordilleran (for the Rockies alone), Sierran, and Campestran,
are equally familiar and precise.
253
254 J. A. G. REHN
ORDER DERMAPTERA
Fossil evidence indicates that the two oldest known members of
the Dermaptera were present in the Jurassic of Kazakstan, from
which they were reported in 1925 by Martynov. One of these,
Protodiplatys, was separated by him as a distinct fossil suborder,
the Archidermaptera, which has blattoid suggestions. The other,
Semenoviola has since been regarded as a member of the restricted
suborder Dermaptera. From the early Caenozoic we know true
forficulids from the middle Eocene of Italy, the Lower Oligocene of
Belgium, the Upper Miocene of Germany, and the Florissant
Miocene of Colorado, as well as from the Baltic Amber. However,
from the Permian of Kansas Tillyard described a representative of
what he regarded as a new order, the Protoelytroptera, which he
regarded as a link between the Paleozoic blattids and the Recent
Dermaptera. It is therefore within the realm of possibility that
North America may at one time have been as much a center of
development of the Dermaptera as the Old World.
Of the ten genera Dermaptera in North America six (Labidura,
Anisolabis, Euborellia, Labia, Chelisoches, and Forficida) are clearly
introduced adventives, and several of these are almost entirely
riparian types, possibly dating back to "ballast" days, while the
genus Prolabia is represented in our fauna by two lines, one clearly
an Old World adventive (now known from southern Texas), the
other an intrusive Neotropical line of the genus found only in our
southeastern states west to Texas.
The three remaining genera are clearly of Neotropical origin as
far as their presence in our limits is concerned. Two occur outside
our territory in Central and South America. One, Spongovostox, is
a pantropical assemblage with probably half the species Ethiopian
or Malagasian in distribution. The second of these genera, Vostox,
is clearly of Neotropical origin. Its single North American species
ranges broadly northward through the eastern United States to
Pennsylvania, yet does not extend any considerable distance west-
ward in Texas.
The third and last genus Doru is also of Neotropical origin, and is
of very broad distribution in tropical America. In our territory
it is widely spread in the eastern and southwestern United States.
In Texas and in the extreme southwest only the widely distributed,
basically Neotropical, D. lineare, occurs, whereas in the eastern
DERMA PTERA AND ORTHOPTERA 255
United States there are two distinctive endemic members of the
genus. It is possible that Doru reached North America in two
separate invasions, the eadier of which established the line that
developed the endemic southeastern species D. aculeatiim and davisi,
and the later of which brought in the widely spread D. lineare,
which is now known from within our territory only from areas of
Texas, southern New Mexico and Arizona, and California. A
single species undoubtedly referable to Doru was described from New
South Wales in 1891. With an intimate knowledge of the hiding
places that Doru selects, I suggest that a restudy of the unique
type will probably show it is inseparable from the widely spread
Neotropical D. linear e, and also that it was introduced from Rio de
Janeiro, when in 1789 various specimens of Opimtia, the nest-egg
of the Australian "prickly pear" scourge, were brought in to supply
food for the similarly introduced cochineal insect.
One of the really puzzling anomalies in the relationship and dis-
tribution of the Dermaptera found in America north of Panama is
the occurrence in areas of south-central Mexico of one species (vara)
of the genus AnechiLrella, the sole representative known from the
New World of the otherw^ise widely distributed subfamily Anechuri-
nae, members of which elsewhere occur from western Europe and the
Madeira Islands to India, China, Japan, Formosa, and Borneo, but
not from continental Africa.
No genera of the Dermaptera are peculiar to North America. The
areal distribution of the genera of Dermaptera shows clearly that the
largest number of generally recognized generic entities occurs ex-
clusively in the Oriental Region, this closely followed in numbers by
the similarly restricted Neotropical, with the I ndo- Malayan and
Ethiopian (with its Malagasy subregion) following. The exclusively
Palearctic genera (12) are equaled in number by those which are
pantropical, with the Australian, Melanesian, and Pacific, broadly
paleotropical, and cosmopolitan following in regularly reducing
representations.
No member of the North American dermapterous fauna, except
those of cosmopolitan distribution, and these usually limited to such
special environments as sea beaches or river banks, appears to have
been derived from the Palearctic Re-ion. All other elements have
clearly come from the Neotropical Region. Several genera of this
source have apparently been established sufficiently long in the east-
256 J. A. G. REHN
ern and southeastern United States to develop distinct specific
entities. All non-adventive forms found west of central Texas and
Kansas clearly have entered our limits within geologically recent
times.
ORDER ORTHOPTERA: SUBORDER CAELIFERA
Superfamily Acridoidea
Family Tetrigidae. The Tetrigidae, or "grouse locusts," are
cosmopolitan, except for the true arctic and antarctic regions and
New Zealand ; they are even represented on some of the Pacific island
groups by distinctive genera. Although terrestrial in habits, they
almost invariably show close association with moist areas, and many
species are fully capable of sustaining themselves on the surface of
water, or of swimming beneath the surface. Their known paleonto-
logical picture is represented by a fossil genus in the Baltic Amber,
material referred to a Nearctic and Neotropical genus from the
Upper Miocene of Bavaria, and an unplaced species of the family
from African copal gum.
Very narrowly within our limits, in coastal south Texas, there
enters the genus Neotettix, an endemic eastern and southeastern
North American assemblage, possibly developed relatively early,
either from a primitive Tetrix-\\\<.Q ancestor, or more probably from
the Neotropical genus Liotettix, to which it has some affinity. A
similar history is probably that of the Mexican and Central American
Ochetotettix, which is related to Neotettix and also to Liotettix, but
Ochetotettix does not enter our territory. Indications point to Neo-
tettix being one of the number of orthopterous genera apparently
derived from a relatively early, certainly pre-Pleistocene, invasion
from the Neotropics; most of these genera are now isolated in the
eastern or southeastern United States.
The genus Tetrix, which is represented in western North America
by five distinct lines, is clearly of Palearctic origin, but it is warranted
to believe that our North American lines of the genus represent a
number of distinct incursions from the Palearctic, certainly one or
two much earlier than the last. From the earlier one or ones three of
our stocks have probably developed: T. arenosa, presumably the
earliest, is now confined to the eastern, central, and southeastern
United States and extreme southeastern Canada; T. ornata is much
more broadly distributed; T. sierrana, clearly related to Old World
DERMAPTERA AND ORTHOPTERA 257
species, was recently described from Madera County, California,
in the Sierras at an elevation of 4,300-5,000 feet. The components
of the Tetrix ornata line, which is confined to North America, are of
particular interest, as they clearly show reactions to the varying
aspects of Postglacial climate, as well as the probable results of
Glacial control. Two subspecies, dominant in eastern and middle
North America, namely Tetrix ornata ornata and T. o. hancocki, are
clearly differentiated in certain areas, and are less sharply, probably
environmentally, segregated in others. The more predominantly
eastern of the two, T. o. ornata, is far less frequent in large series
that represent many localities in the western United States and
Canada, whereas the other, T. o. hancocki, which seems to be more
partial to steppe country or coniferous forest lands and also is more
frequent at higher elevations, is the prevailing form in the broad
sweep of the Great Plains and the Cordilleran region. The Post-
glacial ebb and flow of prairie land and coniferous and deciduous
forests appears to account for the mosaic pattern of distribution
presented by these two elements of this species over a large part of
its range. However, an isolated subspecies, T. o. ifisolens, is known
only from the western slopes of the Sierras in California, and is
broadly isolated from the other localities where the species occurs.
Another subspecies, T. o. occidua, is limited to the Snake River and
Columbia River region of Idaho and Washington, reaching north-
ward to Lake Okanagan in southern British Columbia, in the
general vicinity of which it intergrades with T. o. hancocki of the
higher levels about the Okanagan area. It is probable that the
Columbia-Snake River subspecies represents survival in an area of
relative aridity of a species once more uniformly distributed, and
which normally requires a greater degree of humidity.
The last incursion of the genus Tetrix may have been Inter-
glacial or even Postglacial, as New World and Old World individuals
of the one species involved, T. subidata, are inseparable. In the
New World it is broadly distributed north to the northern border
of the Subarctic, reaching southward in western America to the
southern Sierras of California, to relatively high mountain areas in
southern Arizona and New Mexico, and even to the Sierra Madre
region of northern Chihuahua, Mexico. In eastern North America it
does not range south of eastern Pennsylvania and southern New
Jersey. Another line of the genus developed in North America a
258 J. A. G. REHN
species, T. brunnen, which is found in Hudsonian and Boreal
conditions extending from Alaska to New Brunswick and Quebec,
north to the northern hmits of the Subarctic and south in western
North America in mountain areas as far as the Cascades of central
Oregon and the Rockies of south-central Utah and central Colorado;
in the eastern United States it is known to occur only in the upper
Great Lakes region and the Adirondacks; a closely related, or
possibly inseparable, analog is now known from extreme eastern
Siberia. It would appear that the brunneri line of Tetrix may owe
the base pattern of its distribution to the same activating causes
as the members of the acridoid genus Zubovskya and the blattid
Cryptocercus, discussed beyond.
Paratettix is the most widely distributed genus of the Tetrigidae,
occurring in both hemispheres but not reaching as far northward as
Tetrix. All representatives of the genus in North America are now
regarded as developments of lines that have reached us from the
Neotropical Region. Whether the four chief lines of the genus in
western North America moved from a developmental point in
southern Mexico and Central America northward into the truly
Sonoran areas of more northern Mexico and the western United
States, or whether they evolved in the latter, at present rela-
tively more arid district, and then spread southward, can hardly
be determined from present knowledge. The more pluvial conditions
which prevailed over much of that country during the late Pleisto-
cene and/or early Recent clearly were more favorable for tetrigids
than the severe restrictions of suitable environment there today.
One North American member of Paratettix, P. cucullatus, has a
very broad distribution, reaching from southwestern Ontario and
the northeastern United States to north-central peninsular Florida
and westward broadly to the lower Rio Grande in Texas and the
eastern border of the Great Plains to the northward. However, it
apparently spread, Postglacially in a period of greater precipitation,
from the Platte drainage across the non-mountainous Wyoming
Basin into the drainages of the Green and Colorado rivers and certain
of their tributaries, and also to the Bear and Snake rivers, and
eventually to the Columbia in northern Oregon and southern
Washington. In these immediate areas P. cucullatus and the quite
distinct P. aztecus are the sole members of the genus. The species
aztecus has clearly reached the northwestern United States from its
DERMAPTERA AXD ORTHOPTERA 259
broad sweep in the southwestern United States and Mexico by an
extension of its range covering much of the state of CaHfornia.
The tetrigid subfamily Batrachideinae is one that has, funda-
mentally, a "Gondwanaland" type of distribution and perhaps of
origin. The genera are limited to the Americas, particularly the
Neotropical section, and to the Ethiopian, Oriental, Alelanesian,
and Australian regions. Their greatest development is in South and
Central America, where eleven of its sixteen genera occur. One
genus is Melanesian and Australian, one is Oriental, and two are
Ethiopian, while a single one, Paxilla, is a Nearctic endemic, found
only in the southeastern United States. The genus Tettigidea is
clearly of Neotropical origin, as it has many species limited to South
and Central America, but it became established in our continent,
and particularly in eastern North America, relatively early in the
invasion of our continent by Neotropical types. There are four well-
marked lines of the genus in the eastern United States, with clearly
marked, related species in Mexico and Central America, the range of
none of which, however, is contiguous to those of its relatives in the
southeastern and central United States. One of these lines, T.
lateralis, is much more broadly distributed than the others over the
eastern and central portion of North America, occurring westward to
parts of the Cordilleran region and to certain areas on the Mexican
boundary.
Family Eumastacidae. This is, for the Orthoptera, an old assem-
blage, on the basis of present knowledge probably older than the
true grasshoppers or Acrididae. The oldest fossil definitely referred
to the Eumastacidae is Promaslax of Handlirsch, from the Oligocene
of British Columbia. From the Miocene of Florissant, Colorado,
three species of the genus Taphacris have been described, and these
have been considered eumastacoid by Cockerell, Tillyard, and
Zeuner. A species described from the Oligocene of Baden, Germany,
by Theobald, has also been referred to this family by Zeuner, who is
probably the most capable student of fossil Saltatoria in recent years.
Therefore, the Eumastacidae seem to have appeared in both hemi-
spheres, relatively early in the Caenozoic, at a time of probably
greater warmth than today.
The greatest development of the Eumastacidae at present is in
the tropics of both hemispheres, with the maximum generic differ-
entiation in the Indo-Malayan and Oriental Regions, followed by the
260 J. A. G. REHN
Ethiopian and Malagasian and the Neotropical. One of the most
aberrant subfamiHes, hmited to AustraHa and Tasmania, in a num-
ber of respects approaches the exceedingly distinctive and endemic
Neotropical family Proscopiidae. No member of the Eumastacidae
extends into the Palearctic Region except in elevated areas of Central
Asia and in Japan, and the family is absent from the Pacific Islands
east of New Guinea and from New Zealand, as well as from Chile
and southern Argentina. Three genera are known from two of the
greater Antilles (Cuba and Hispaniola), but the family has not been
taken in any of the others.
The southwestern United States is the only part of North America
in which members of the family now occur. They represent five gen-
era of two very different subfamilies, both of which, as far as present
knowledge indicates, are endemic within the area. One of these
subfamilies, the Tanaocerinae, comprising the genera Tanaoceriis
and Mohavacris, is localized in certain semi-arid and arid mountains
and adjacent desert areas of southern California and southern
Nevada, except for one species of Tanaocerus that is also found in
northern Baja California. This subfamily in many respects is one
of the most distinctive assemblages in the superfamily Acridoidea,
the antennae being the longest in any members of that extensive
and varied aggregation known as the "short-horned" grasshoppers.
The Tanaocerinae, which has been regarded by some as of family
rank, and even considered by one student to represent two families,
is clearly a Nearctic autochthon, which because of its combination
of unusual characters certainly may be inferred to have developed
a considerable time in the past. It is in a number of respects probably
the most strikingly isolated section of the whole family, and it
apparently developed from one of its ancestral lines. The other
Nearctic subfamily, the Morseinae, comprising the three genera
Morsea, Eumorsea, and Psychomastax, is a cohesive assemblage
known only from Arizona, extreme southwestern Utah, southern
Nevada, and areas of southern and coastal California north to Mt.
Tamalpais. Morsea, the most widely distributed of the three, occurs
in its preferred habitat over the greater part of the full range of the
subfamily, although it is not known from southern Arizona. Psycho-
mastax is peculiar to mountain areas of southern California and
southern Nevada, reaching northward along the eastern slope of the
Sierra Nevadas, occurring also in the White Mountain section of the
DERMAPTERA AND ORTHOPTERA 261
Inyo Range, and in the Charleston Mountains of southern Nevada
as high as 11,500 feet. Both genera are chiefly thamnicolous; Morsea
occurs largely on chamise (Adenostoma) and manzanita {Ardosta-
phylos). The genus Enmorsea is known only from a few areas in the
mountains of what Mearns sixty or so years ago called the "Central
Elevated Tract," in extreme southern Arizona, where it has been
found on the foliage of conifers. A^Iost certainly Eumorsea also occurs
to the southward in the Sierra Madre of Mexico, and the same is
doubtless true of Morsea and Psychomastax in at least some of the
mountains of Baja California, although neither has been so reported
to date. The nearest relatives of the members of the subfamily
Morseinae are probably those of the central and eastern Asian sub-
family Gomphomastacinae, of which the five or so known genera,
range altitudinally upwards to high areas in the Karakoram section
of the Himalayan uplift (to at least 14,500 feet), and in northern
Afghanistan (where exact elevations are largely unrecorded).
Whether the Morseinae and the Gomphomastacinae have had a
reasonably recent common ancestry remains to be determined but
this possibility is now under investigation. However, the Morseinae
clearly comprise a cohesive natural assemblage, occurring in a
relatively limited Nearctic region, which also shows numerous
similar parallels in the distribution of other elements of the
Orthoptera.
A third subfamily of the Eumastacidae, the Teicophryinae, con-
sisting of two Mexican genera, is known from the Cape Region of
Baja California, but has not been taken north of that limited area,
although the same genus (Teicophrys) occurs in certain areas of
south-central and southern Mexico. The other genus, Cadomastax,
is known only from a section of western Mexico. The Teicophryinae
do not occur south of the Isthmus of Tehuantepec, where several
other subfamilies of the Eumastacidae of more austral Neotropical
relationship are present. Presumably the Teicophryinae have
developed in Mexico.
Family A crididae. (1) Subfamily Romaleinae. The Romaleinae
is a well-marked subfamily of the Acrididae, or true grasshoppers,
with more than two score genera from South and Central America
and certain areas of the United States. Several Old World genera
have quite recently been referred to this assemblage, but I question
this association, which is now under careful study. Within this
262
J. A. G. REHN
subfamily Is found a wide range of structural modifications and de-
velopments, and adaptations to conditions ranging from those of
the densest of lowland rain-forest undergrowth to the most arid
desert environments. In my opinion the subfamily is clearly one of
Neotropical development. Its members occur over the Americas
from the Dakotas to central Argentina and Chile, with a single
endemic genus on one island (Cuba) of the West Indies.
Within the territory we are covering five genera of the subfamily
occur, one of which, Brachystola, sweeps north broadly from Mexico
over the Great Plains to South Dakota, and also is locally abundant
in central and southern Arizona; another, Taeniopoda, is narrowly
intrusive from Mexico and Central America, where the genus is
broadly developed, in border areas of the United States from
western Texas to central-southern Arizona; a third, Phrynotettix,
is an inhabitant of Sonoran deserts, brushland, hills, and mountains,
from western Texas to south-central Arizona, and also extends
southward in non-tropical Mexico; a fourth genus Tytthotyle, is
reported from the hottest and most arid Lower Sonoran deserts of
southwestern Arizona, southern Nevada, extreme southwestern
Utah, and southern California, although it doubtless occurs in suit-
able sections of Sonora and perhaps Baja California; while the
fifth genus, Dracotettix, is known only from the coastal ranges,
the San Gabriel and San Bernardino Mountains, the lower and
drier eastern slopes of the southern Sierras, the Panamint Range,
and other desert mountains of southern California, as well as extreme
northern Baja California, where the most generalized member of
the genus has been found.
The broad center of origin of our Romaleinae has clearly been the
Neotropical Region, but the genera in western North America have
doubtless developed as generic entities in our territory and in Mexico
(particularly in northern Mexico); only one of the genera,
Taeniopoda, extends as far south as Panama and none is represented
in South America. Romalea, the sixth genus of this subfamily, in
North America, is limited to the southeastern United States, ranging
only as far west as central Texas and not entering semi-arid country.
It would appear that the North American genera of the subfamily
indicate a number of incursions from the south, of which the first is
now represented by Romalea. The ancestral line of Romalea probably
entered the area at least as early as the Pliocene. Dracotettix, con-
DERMAPTERA AND ORTHOPTERA 263
ceivably just as old in California and Baja California, has no present
day relatives in Mexico proper (its nearest relative is the rare and
little known Litoscirtiis of Baja California, which for a number of
reasons I feel represents the ancestral line of Dracotettix) . The genus
Brachystola probably entered North America in the grass-dominant
Pliocene, as it is more frequently encountered in dry or desert
grass conditions than the other genera. The ancestral stock of
Phrynotettix, which is more truly an arid land genus, may have
reached our territory about the same time, as it has developed within
our limits two well-distinct specific lines. The genus Tytthotyle has
no very close relatives, and may have evolved within our territory and
northern Mexico from an old ancestral line, possibly dating back
of any of the others. It has a very circumscribed distribution, prefers
areas of creosote bush {Covillea tridenlata), and altitudinally does not
occur above 2,500 feet, yet is at home under the extremely rigorous
conditions on the floor of Death Valley in August. The genus
Taeniopoda, represented within our territory by the northern border
of the distribution of a widely ranging Mexican species, appears to
be a post- Pleistocene intrusive from Mexico.
(2) Subfamily Cyrtacanthacridinae. The great group of the
"spine-breasted" grasshoppers and locusts, which includes many of
the world's most important migratory and destructive locusts, is
represented in western North America by at least four well marked
tribes, the Leptysmini, the Cyrtacanthacridini, the Vilernini, and
the Melanoplini. Of these, the Leptysmini and the Vilernini are
entirely Neogaeic; the Cyrtacanthacridini, or "bird locusts," are
almost entirely Paleogaeic, and chiefly Paleotropical, with but a
single genus entering the Western Hemisphere; and the Melanoplini,
while predominatingly Neogaeic, also share the Palearctic Region
and, more narrowly, the Oriental.
Of the Leptysmini the single genus Leptysma occurs within the
limits of our symposium scope, and is found very locally in suitable
areas of tall grass and other vegetation growing generally in standing
water (a preferred habitat for members of the tribe, all of which
possess definite ability to dive into and swim for short distances in
water, usually to rest longitudinally on the stems of grasses or
rushes). In the Neotropical Region, particularly in its South
American section, are numerous species of Leptysma and certain
related genera. Within our territory Leptysma is clearly of Neo-
264 J. A. G. REHN
tropical origin, and it has broadly established itself, with a related
genus of similar Neotropical relationship, in suitable environments,
across parts of the southern United States. However, Leptysma
occurs across the entire southern border of the western United
States, and into Mexico, while the other genus (Opshomala) is
found within North America only in the southeastern United States,
It would appear probable that the presence of Leptysma in localized
areas in the southwestern United States is a reminder of a broader
dispersal, probably in Pleistocene times of a greater degree of
precipitation.
Of the Cyrtacanthacridini, to which tribe belongs the striking and
often exceedingly destructive "bird locusts," but a single genus,
Schistocerca, lives in the Western Hemisphere, and while it has
developed there a considerable number of endemic species, a single
member of the genus is limited to the Old World, and is there one
of their most serious plague forms (the desert locust, Schistocerca
gregaria). While this species is known to reach as far across the
Atlantic Ocean from the West African coast as the island of As-
cension, and has also been captured landing on a ship midway
between Africa and South America, there is no certainty that the
numerous New World species of Schistocerca, representing at least
ten diverse lines of the genus, have entered the New World by
flying the South Atlantic, as a number of our species are not addicted
to extensive flights, and also some are definitely localized in their
distribution and ecological preferences. The optimum differentia-
tion of the Cyrtacanthacridini clearly took place in the Old World,
and our stock was certainly derived from progenitors there. It
is possible that Schistocerca, from a basic ancestral stock of the
tribe, developed its various lines in the New World, and that the
one to which gregaria belongs, which is well represented in the
Americas, North, Central and South, later reentered the Old World,
giving it its troublesome S. gregaria. If the latter were a local or
restricted type we could conclude that the genus was Old World in
origin and is there dying out, but with gregaria in an entirely
different category, and the genus greatly diversified in the Americas,
it is plausible to conclude that its ramifications had their base in
the New World.
Of Schistocerca five lines occur within western North America,
and they are restricted to the same general area except that certain
DERMAPTERA AND ORTHOPTERA 265
of them reach into Mexico, with, however, the greater part of the
known range of three north of the Mexican boundary. One, 6*.
mexicana, is but narrowly intrusive in our territory from Mexico.
Also in the eastern, central, and southeastern United States are
four other lines of the genus, two there limited, one largely re-
stricted to that area, and the fourth also found rather broadly and
passing into Mexico, but almost limited westward by the eastern
border of the Great Plains. Clearly certain of these distinctive lines
of Schistocerca have been established in our territory for a consider-
able time. Their history is tied to our area because, where found in
Mexico, most of them are Sonoran only. One of the lines in the
eastern and central United States, but hardly encroaching on our
territory, is broadly developed in Central and South America,
there having spawned one of the most destructive locusts of the
New World, the Parana locust {Schistocerca paranensis) of Argen-
tina and many other areas of South and Central America.
The Vilernini are a most distinctive Neotropical assemblage of
a score or more genera, ranging from Argentina northward to
briefly north of the Mexican boundary, and are found in a variety
of habitats. Clematodes, the single genus in our region, is an apterous
thamophilous grasshopper, known only from the border regions of
western Texas, southern New Mexico, and Arizona, extending into
Mexico in several areas. It clearly has entered our territory from the
southward, and with us is probably more widely distributed in the
Lower Sonoran Life Zone than the records indicate (the secretive
habits of this grasshopper, which, among other situations, likes the
main stems of the intrusion-resisting cat-claw (Acacia), are largely
responsible for our limited knowledge of it).
European students have broadly assumed that the great assem-
blage of the Melanoplini is basically a Eurasian group, with an
Angara background, and that its presence in the New World is
attributable to a relatively recent extension from the Old. Recently
this assumption has been challenged, on the basis of a relatively
critical analysis of the whole picture for the tribe. Little help can be
drawn from the fossil picture, as the total of such evidence to date
indicates the presence of two existing species of two genera in the
Pleistocene of Starunia in the Polish Carpathians. What we do
know is that in the New World members of the Melanoplini occur at
localities reaching from the Arctic Circle to at least south-central
266 J. A. G. REHN
Argentina and Chile, thus well over one hundred degrees of latitude,
and occupy stations ranging from extremely arid ones below sea-
level to others as high as Arctic-Alpine in North America and the
Paramo in South America. Three major centers of evolution of the
Melanoplini in the Americas have clearly been indicated: (1) North
America south to the Isthmus of Tehuantepec; (2) the Venezuelan
Andes and adjacent, chiefly montane, areas in northern and eastern
Columbia; and (3) South America from approximately 15° south
latitude southward. Few genera of the tribe occur over the inter-
vening areas. In the Old World the tribe is much more circum-
scribed, for it is absent from the Ethiopian region, from most of the
Oriental region and from all the Australasian region. In Eurasia
twenty-seven genera occur, three of which are also in the Nearctic.
In the Nearctic and Neotropical combined, we find 59 genera,
including the three occurring also in Eurasia. In the New World
forty genera are known north of the Isthmus of Tehuantepec, the
majority only north of the Mexican boundary.
Within the northern United States we find one line of the Melano-
plini, the genus Podisma, which clearly is of Old World relationship,
for it has numerous species in Eurasia and only one in North
America, P. hesperus, in the Cascades of Oregon, the nearest relative
of which appears to be a species of northern Japan, P. sapporensis.
It is probable that the ancestral stock of this species reached our
continent in the Pleistocene, perhaps Interglacially, or even earlier.
Another line in North America, comprising the genera Dendro-
tettix and Appalachia, also represents an older invasion of the same
stock. (This line is not now present in western North America;
its two generic members occur, so far known discontinuously, in
the eastern and central parts of the United States.) These
two genera clearly developed within our territory. A third line,
including the single flightless genus Zubovskya, which occurs dis-
continuously in eastern forested areas of North America and in the
Cascades of Oregon, is also represented in a limited section of
eastern Asia by several distinct species. Whether Zubovskya is an
Asiatic genus that has traveled to North America and spread
broadly there, or is of North American origin and has narrowly
entered the Old World, remains to be determined. Clearly, however,
it has been present in North America since before the Glacial
period, as there can be little question but that the present dis-
DERMAPTERA AND ORTHOPTERA 267
continuous distribution of the genus in our continent reveals the
part the ice-sheets had in separating the eastern form of this forest
land genus from that now occurring in the Oregon Cascades. A
largely parallel case of discontinuous distribution of this type,
with apparently the same origin, is that of the flightless wood-
boring cockroach Cryptocercus.
It seems that all the other numerous lines of the Melanoplini in
western North America have developed within our territory, and
that a single species of the genus Melanoplus has crossed into the
Old World. The genus Melanoplus developed a considerable number
of specific lines in North America, with a very marked center of
speciation in the southern Appalachians and the adjacent lowlands,
while other lines, clearly representing evolutionary phyla, have
centered in the grasslands of the Great Plains, the Transition and
Canadian areas of the Rockies, the Great Basin region and its
various mountain areas, the Lower Sonoran Deserts of the south-
western United States and northern Mexico, the Sierra Nevadas,
and the coastal ranges of California and Oregon. In each of these
areas one or more definite lines of development of the genus will be
found. Some lines reach as high in their distribution as Hudsonian or
even Arctic-Alpine conditions, often with some species quite local-
ized. To the southward the genus Melanoplus enters Mexico,
where there is a considerable number of more broadly ranging and
endemic species, but the genus does not extend south of that country.
The Melanoplini of Mexico are rich in species and work now under
way will shortly give us a clearer picture of the richness of that
fauna, which with the western part of North America has been a
major site in the evolution of the Melanoplini.
Of the other genera of the Melanoplini in western North America,
the Campestran Great Plains apparently produced at least four,
Campylacantha, Argiacris, Phoetaliotes, and Hypochlora. Phoetaliotes
is more widely distributed in grassland areas (formerly of greater
extent, perhaps in the Pliocene, a grassland optimum), and relict
populations remain in sections of southern Arizona and certain
other areas. The genus Dactylolum, now widely distributed in
Sonoran situations in western North America, is doubtless of Mexi-
can origin, as there the genus has developed a broader specific
diversity than it has north of the Mexican line, although in the
latter territory its range is much more extensive. The same is prob-
268 J. A. G. REHN
ably true of the array of distinctive genera found broadly over
areas of central and western Texas {Phaedrotettix, Phaiilotettix,
Paratdemona, Chloroplus, and Agroecotettix). The genus Aeoloplides
is of broad distribution in the Great Plains, the Sonoran deserts of
the southwestern United States, the Great Basin, and areas of
California, and is probably a relatively old line, very adaptable to
the distinctly thamnicolous habitat it prefers. The genus Aidemona
is narrowly present in our territory as an intrusive from Mexico and
Central America (it ranges southward to Colombia).
In the Sonoran desert mountains and on the benches of the south-
western United States we find a group of genera that probably
originated there, or in adjacent northern Mexico, where they also
do or may occur. These are Conalcaea, Barytettix, Poecilotettix,
and Aztecacris. Another clearly Sonoran type is the genus Hes-
perotettix, which is of wide distribution over most of the lower level
land areas of the western United States and Canada, where its
favorite cover of yellow-flowered composites of several genera
("rabbit weed") occurs. Two lines of the genus undoubtedly entered
the southeastern United States from more western territory a
considerable period in the past and there developed a subsidiary
evolutionary center of the genus, while another line of campestran
relationship spread in ecologically suitable areas over much of the
eastern states. In many areas of California and of the Great Basin,
as well as the Columbia River and Snake River plains, the genus
Oedaleonotus has developed a marked radiative speclation. It
apparently is an autochthon which has no very close relatives.
In mountain areas of the western United States and southwestern
Canada there have developed a number of apterous, and of course
flightless, endemic genera, of which three, Bradynotes, Prumnacris
and Buckellacris, are of Canadian and Hudsonian Zone distribution.
The most highly specialized is probably Brady?iotes, which occurs in
isolated areas of the more northern Rockies in the United States
and adjacent Canada, the Cascades, the pumice plains east of the
Cascades in Oregon, and in the more northern Sierras. The genus
also reaches southward to the Kaibab Plateau of northern Arizona,
although in the main Rockies it is not known from south of South
Pass, Wyoming. It is possible future work may show that Prumn-
acris and Buckellacris, as well as the strange Nisquallia of the
Olympic Mountains of Washington, are more nearly related to
DERMAPTERA AND ORTHOPTERA 269
Old World genera than has yet been determined. Prumnacris and
Buckellacris are both distinctly northern montane types: Prumn-
acris occurs chiefly in the northern Cascades, and Buckellacris
extends from the same range northward to the Chilcotin area of
British Columbia, and eastward over the northern Rockies to south-
eastern Idaho. In the Rockies of the northern United States and
southern Canada, and in adjacent parts of Washington and the
northern Sierras of California, the distinctive genus Asemoplus
is localized, and in the southern Sierras only at or near timberline
do we find Hebardacris, which has nearest affinity to Bradynotes.
All these montane genera are clearly of relative antiquity, and
probably survived Glacial conditions by retreating moderate
distances before the advancing sheets or the encircling spread of
mountain glaciers. Some of them seem to have reoccupied only
limited sections of suitable terrain which was heavily glaciated.
(3) Subfamily Oedipodinae. The Oedipodinae comprise a large
number of chiefly ground-dwelling grasshoppers, some of which have
become of economic importance. The subfamily is poorly represented
in the Southern Hemisphere, and is best developed in Eurasia and
North America. In South America its members are limited to a few
genera, one of which, Trimerotropis, is markedly developed in North
America, while another, Heliastus, narrowly enters our territory.
The maximum diversity of the subfamily is in semi-arid grass-
lands, although it is also well represented in true deserts and semi-
deserts, and a number of types occur in more humid grasslands and
bush country; a very few are more partial to wooded areas. Some
of the species live in the most arid environments to be found in this
continent and in similar areas in Asia and North Africa. Some are
governed in their occurrence by the presence of favorite food plants,
but on this point our information is less conclusive than for some
other grasshoppers. Apparently most, if not all, of the North
American genera have developed in our territory or in northern
Mexico, although the possible relationship of a few of the genera to
those of Central Asia remains to be more accurately determined.
Broadly speaking, however, the oedipodine fauna of North America
is autochthonous. A number of the genera probably originated in the
Sonoran region of our southern Great Plains, the southwestern
United States, and northern Mexico. Certain of these genera have
extended their ranges into the more eastern United States and
270 J. A. G. REHN
adjacent Canada, and some have developed well-marked subsidiary
evolutionary centers there. Trimerotropis, an entity with a consider-
able number of North American species, is probably a relatively old
type, which has extended locally into boreal conditions, has formed
certain localized species in the eastern United States, and has further
intruded itself southward, so that today the genus is also present in
semi-arid and Andean areas of western South America. Its range
there is now cut off from the southern limits of its mass distribution
at the southern edge of the Mexican tableland. This discontinuous
distribution probably exemplifies a far broader and drier Pliocene
grassland distribution, and reflects the increased Pleistocene develop-
ment of forest areas in the intervening territory, which doubtless
eliminated Trimerotropis from Central America and parts of north-
western South America. A similar postulate would explain the
present discontinuous distribution of the grassland mantid Brunneria
and the acridine grasshopper genus Dichromorpha.
The genus Chortophaga is probably of southeastern origin, there
showing two types of the genus, one species of which, present over
much of the eastern and central United States, is also found in the
more temperate parts of Mexico and Central America as far south
as Costa Rica. The endemic Californian genus Chimarocephala is
rather an anomaly, although its ancestral stock may have had a
common origin with Chortophaga. The genus Cammda probably
developed from the same stock as Hippisciis or Encoptolophus,
possibly in the Cordilleran region, but it now has an unusual type of
distribution; it is essentially Boreal in the eastern and central
United States and Canada, broadly present in the Cordilleran
region, and much more localized westward (in southern California
it even descends to virtual sea level in coastal Lower Sonoran
conditions). The broadly spread but often localized genus Xaiithip-
piis, a close relative of Hippiscus, apparently developed in the
Sonoran region of our Great Plains, the southwestern United States,
and northern Mexico, with numerous localized and seasonally limited
montane forms, but it has not spread eastward, while the related
Cratypedes is much more definitely an inhabitant of the Cordilleran
and Great Basin areas. The genera Sticthippus and Agymnastus are
Californian endemics, clearly derived originally from the same basic
stock as Hippiscus, Pardalophora, and Xanthippus. The genera
Leprus and Derotmema are certainly of Sonoran origin, and both
DERMAPTERA AND ORTHOPTERA 271
have spread northward over the Great Plains and entered the Great
Basin, in which area Derotmema has developed a very distinctive
type {D. piiite). Hadrotettix, Tropidolophus, and Platyladista are
also Sonoran. The first two extend to varying degrees northward
over the Great Plains. Hadrotettix is also known from relict grassland
areas in northern Arizona.
The more dominantly eastern genus Spharagemon probably had
its origin in the eastern United States, where it now has three dis-
tinct lines. Two of these lines extend westward, but the extent of
the genus in that direction is virtually limited by the Rockies.
Spharagemon has four well-marked lines in the Great Plains and in
Texas, of which two also occur in the eastern United States. The
genus Dissosteira is widely spread over the United States, narrowly
entering Canada. One of its species is almost ubiquitous in the east-
ern United States, but west of the Rockies it chiefly occurs in the
Transition zone. A second species is basically a Great Plains form,
a third is largely Californian and Great Basin, and a fourth occurs
locally only in California. The genus is apparently of Sonoran origin,
and the same may be true of the related Scirtetica, which has one
locally distributed stock in coastal areas of the eastern and south-
eastern United States and in the Great Lakes sections of the
United States and southeastern Canada, while another stock is
isolated in the mountains of southern Arizona, with no representa-
tives known from the interv^ening sections of the territory the pres-
ent symposium is covering, or as yet from Mexico. The strange
little genus Microtes is an autochthon of the Californian coastal
mountains and adjacent valleys, with no very close relatives, and is
probably an old type. Lactista and Tomonotus are clearly Mexican
Sonoran entities rather narrowly intrusive in our border states.
The genera Trepidulus, Shotwellia, and Ciholacris are relatively
arid land Sonoran types. The last is also coastal in southern Cali-
fornia. All three probably range into northern Mexico, and doubtless
all had their origin in that great area on both sides of the inter-
national lioundary which, even in its diversity of surface features,
has to a considerable degree had a similar faunistic history. The
genera Mestobregma and Metator are clearly of Sonoran origin ; each
extends northward over the Great Plains and the Great Basin, with
distinctive lines in each of these areas, indicating a considerable
period of time for divergence and development of differentiating
272 J. A. G. REHN
stocks. Trachyrhachts, which clearly has had a similar history, has
also extended the range of one of its species eastward, probably
Postglacially, to parts of the Appalachian uplift in the eastern
United States. The genus Rehnita is an additional Sonoran type,
probably derived from the same basic stock as Mestobregma.
The genus Conozoa has more affinity to Trimerotropis, which has
already been mentioned, than to any other member of the sub-
family, and it may represent an offshoot from the same stock. If so,
its divergence was not recent. The genus occurs entirely within the
area of our coverage, only rarely east of the Continental Divide.
The chiefly Boreal and generally montane genus Circotettix may also
originally have been derived from the basic Trimerotropis stock.
Its distribution is often discontinuous, extending eastward across
southern Canada and the northern United States into Boreal areas
in eastern North America. Its species are among the few grasshoppers
that perform aerial stridulating dances. Another genus with the same
proclivities, that may be related in some degree to the Eurasian
genus Bryodema, is Aerochoreutes, which occurs in Upper Austral
and even Transition areas of the northern Great Plains, northern
Great Basin, and the Columbia-Snake River semi-arid hills.
The extremely arid sections of the Lower Sonoran life zone are the
home of the genus Anconia, which also occurs some distance south-
ward into northern Mexico. It would appear to be endemic in the
territory where it now occurs. Its only known relative is Spaniacris,
which lives in limited, and intensely arid, sections of the same area
in southern California and extreme western Arizona. These two
genera clearly are old desert types, with no close relatives, markedly
specialized in a number of respects, and with distinctive habitat
preferences. The genera Xeracris and Coniana, smaller desert types
known only from the most arid sections of the Colorado, Yuma, and
Mohave Deserts, are similar to Spaniacris in distribution, but
are of different affinities. They are clearly authochthons without
any very close relatives, although further study on this matter is
required.
The genus Heliastus is a Mexican and Central American type,
which reaches even to northern South America, but in our territory
is found only narrowly and locally in southern Arizona and coastal
Texas. This is clearly a Sonoran genus which has spread southward —
a less frequent pattern. A Sonoran type of higher levels, largely
DERMAPTERA AND ORTHOPTERA 273
Upper Sonoran, is the genus Heliaula, which extends northward
over the Great Plains as far as eastern Colorado, but does not go
far west of the Continental Divide.
(4) Subfamily Acridinae. The Acridinae, or slant-faced grass-
hoppers, which in our section of the world are in considerable part
grassland forms, are very well represented in our fauna, and the
greater part of the forty or more genera reviewed clearly have
developed within North America west of the Mississippi. Two
genera, Chorthippus and Stethophyma, are certainly relatively
recent Palearctic intrusives in North America, the former so recent
that the single species we have is also widely distributed in Eurasia.
Chorthippus has a large number of Old World species, and it is possi-
ble we received C. longicornis in an Interglacial period. Our three
species of Stethophyma are endemic, two with preferences for Boreal
or sub-boreal conditions, the other of infrequent and very local
occurrence over a broad section of eastern North America. The
species of sub-boreal preferences occurs in widely separated parts of
western North America, but has been taken at only a few localities.
Presumably Stethophyma reached North America from Eurasia
prior to the advent of Chorthippus, as its species are well differenti-
ated from Old World forms.
One set of three genera, representing the group Chrysochraontes,
has presumably also been derived from Eurasia, probably through a
succession of waves. The earliest invasion was probably that of
an ancestral stock of the genus Chloealtis, which today is chiefly an
inhabitant of the more northern parts of eastern North America,
although it narrowly reaches our included territory in eastern
Colorado. Apparently a second intrusive line of the same group is
represented by Chrysochraon, which occurs broadly in the Pale-
arctic, and of which we have a single endemic species in Cordilleran
montane localities. A third line of the same group comprises the
equally endemic genus Napaia of Coastal Range mountains of
southern Oregon and California, as well as the San Gabriel Range in
the latter state. The members of the Chrysochraontes are peculiar
in that they usually oviposit in dead wood, an unusual situation for
acridids. Another genus of Palearctic relationship is Aeropedellus
a Cordilleran and high Great Plains genus, which clearly has been
derived from the same stock as a number of Palearctic genera
related to, and including, Gomphocerus and Aeropus. A distant
274 J. A. G. REHN
relative of Aeropedellus, but without Old World relatives, is Brun-
eria, which is a northern type, usually found under Boreal, or even
Hudsonian, conditions, from southern Canada sporadically and
very locally south in the Cascade-Sierran uplift to northern Califor-
nia and in the Cordilleran massif at least as far as southern Utah.
It appears to have developed in the territory where it now occurs,
with greater diversity in the Cordilleran section than elsewhere.
Three of our acridine genera, Amblylropidia, Orphiilella, and
Rhammatocerus, are clearly of Neotropical origin. All have a far
greater specific development and areal extent southward than in
our area, extending to southern Brazil and Argentina. Amhlytro-
pidia is only narrowly represented along our Mexican border by
one of a number of Mexican species, although a distinct endemic
species occurs rather broadly over the southeastern United States.
Rhammatocerus is similarly represented along the Mexican border,
but not elsewhere in North America. Both of these genera apparently
are more recent intrusives than Orphulella, which is broadly present
in North America from Atlantic to Pacific. Because of its habitat
preferences Orphulella is of much more localized occurrence in the
western part of its range than in the East. A considerable number
of the genera of the subfamily in North America, including Paro-
pomala, Acrolophitiis, Amphitornus, Opeia, Cordillacris, Phli-
bostroma, Boopedon, Ageneotettix, Drepanoptertia, and Aulocara,
I would regard as autochthonous in our Great Plains, the adjoining
Texas Sonoran area, or the Sonoran areas to the westward. Other
genera, including Achurum, Eremiacris, and Morseiella may, with
reasonable assurance, be regarded as having developed in Mexico,
and species there found, or closely related ones since evolved,
occur on our side of the border. Another genus that should be
placed in this category is Syrbida, although it apparently entered
our territory quite some time in the past, as one of its species,
which also is distributed over much of Texas, is broadly established
in our more southern and southeastern states. The genus Mermiria
is represented in the West by four of the well-difi'erentiated lines
that it has evolved in the United States. In all probability this
genus developed in the Sonoran region, spread broadly over the
Campestran, and then extended its range into the southeastern and
central states, where three of its lines occur. One of its most dis-
tinctive species, M. texana, is present on both sides of the Mexican
DERMAPTERA AND ORTHOPTERA 275
border, on arid rocky hills and in brush land, while another, definite-
ly a Campestran (Great Plains) type, narrowly extends into Mexico.
Pseudopomala, a near relative of Mermiria, is widely distributed
over the more northern section of the United States, occurring
sparingly in restricted environments. At least some of its present
spotty distribution probably can be explained as a subsequent
readjustment to Glacial displacement, but on this point more
study is needed.
The highly specialized genus Radinotatum is largely limited to
the southeastern United States, but includes a quite distinct species
in southern Texas. Its nearest relative is apparently Achurutn,
which is Mexican in origin, although found within our limits in
southern Arizona. The genus Prorocorypha is of localized occurrence
in certain mountains of extreme southern Arizona. Its nearest rela-
tive is the rather broadly distributed and highly specialized, equally
graminicolous Sonoran genus Paropomala. The genera Acantherus
and Horesidotes are apparently endemic generic types of the Sonoran
Mexican border country in Texas, New Mexico, Arizona, and
California. The same is true of the strictly thamnophilous genera
Ligurotettix and Goniatron, the former of which does not occur east
of the Continental Divide and extends northward as far as west-
central Nevada, while Goniatron lives almost entirely east of the
Continental Divide in the Chihuahuan Desert area and is much
more limited in its north and south distribution, but with its range
definitely known to extend a considerable distance into northern
Mexico. In habitat Goniatron is restricted to "black brush" (Flour-
ensia), while Ligurotettix is found on more than one species of
shrub, but often on creosote bush (Covillea).
The genus Pedioscirtetes comprises two lines of development, one
of which occurs in the Mexican border territory from western
Texas to southern Arizona, as well as some distance southward into
Mexico; the other is known only from very limited, distinctly more
elevated areas in northern Arizona, Nevada, Utah, and southern
Idaho. It appears to me that the genus originally developed in our
older plateau areas adjacent to the Cordilleran mass, and that one
element moved southward, perhaps in Pleistocene times, while the
other remained, survived lower temperatures, and has even extended
its range northward. The genus Bootettix is always associated with
the Lower Sonoran creosote bush {Covillea), and is almost never
276 J. A. G. REHN
found off of it. It clearly developed in the area of our Mexican
border. One species occurs on the Pacific side of the more elevated
Continental Divide, the other on the Atlantic side; both are known
to extend southward, with their host plant, into Mexico.
The genera Esselenia and Eupnigodes are Californian endemics.
The former is found only in the central section of the Coast Range
region, and has no known close relatives. On the other hand
Eupnigodes, which is more broadly distributed over the San Joaquin
Valley and the lower western slopes of the Sierra Nevada, is rela-
tively close to Ageneotettix, which is a quite widely dispersed
Sonoran genus, and clearly the stock from which Eupnigodes
developed in relatively recent times. Another apparent development
from the Ageneotettix line is Zapata, of which a few species are quite
locally distributed in southern Arizona, western Texas, and northern
Mexico. A genus almost exclusively Texan Sonoran is Mesochloa,
which is clearly derived from Eritettix. The latter, probably also of
Sonoran origin, is broadly distributed northward over the Great
Plains and westward along sections of the Mexican borderland.
One species of Eritettix has deeply penetrated into the central and
eastern United States, where it occurs from New England and
Nebraska southward. A related, and apparently derived, endemic
genus, Macneillia, is restricted to peninsular Florida.
The genus Dichromorpha is probably of Sonoran origin, but
ranges northward over most of the central and eastern United
States, with several species in Mexico, while to the southward, after
a gap of some thousands of miles, it reappears in areas of Paraguay
and northern Argentina. It is a grassland type and its distribution,
like that of the mantid Briinneria, probably reflects the much
broader extent of grasslands in the Pliocene, and their later restric-
tion by the moister and colder Pleistocene, with its greater develop-
ment of forests.
A dominant genus of largely arid or semi-arid sections of the
whole Sonoran region, also occasionally entering the Transition Life
Zone, is Psoloessa, one line of which extends as far northward in
the Upper Sonoran as the Okanagan Lake country of extreme
southern British Columbia, and also to sections of the Great Plains
of southern Alberta, Saskatchewan, and Manitoba. Southward one
line of Psoloessa reaches as far as the Mexican states of San Luis
Potosi, Guadalajara, and Mexico. Psoloessa is probably one of the
DERMAPTERA AND ORTHOPTERA 277
types that developed in areas of our Southwest, or it may have been
intrusive in our area from Mexico, though I am more incHned to
place its origin as north of the Mexican line, since one of the three
main elements of the genus does not, as far as we know, reach
Mexico, and it is, with us, always an Upper Sonoran or Transition
species. A second of these main elements is restricted to the western
section of the southern half of California and several areas of Baja
California, while the third is broadly distributed from east-central
Texas west to west-central Arizona and northward over the Camp-
estran region to South Dakota.
ORDER ORTHOPTERA: SUBORDER ENSIFERA
Superfaniily Tettigonoidea
Family Tettigoniidae. Passing now to the great assemblage of
what we Americans call the "katydids," but which are elsewhere, in
the English-speaking world, referred to as "long-horned grasshop-
pers," or technically the Tettigoniidae, we have first the virtually
cosmopolitan subfamily of the Phaneropterinae. This is represented
in western North America by eight endemic genera, none of which is
Holarctic, and by one, Microcentrum, the " angular-winged katydid,"
that is clearly Neotropical in origin and is much more variedly de-
veloped in that region. This genus reaches on one hand to California,
and on the other is broadly spread over the interior and eastern
United States, but does not reach high altitudes in the Cordilleran
section. One genus, Platylyra, is endemic in the California coastal
mountains, and probably represents a relatively early development,
perhaps from fundamentally Neotropical ancestors. The genus
Insara was certainly Neotropical in origin, but it clearly has been in
and has undergone a considerable part of its evolution in the broad
Sonoran region, developing there at least four lines, one of which
lives only on the creosote bush (Covillea). Other species of Insara
range from Mexico to Panama, while related genera are known
from Panama and northern Argentina. The genus Brachyinsara,
which as clearly has had a common ancestry with Insara, is known
only from extreme southern California and Baja California.
The genus Arethaea, composed of spectral, ghostlike species, is
clearly a development of the Sonoran center. Certain of its species
are found in northern Mexico, but the majority occur within the
limits of the United States, ranging northward in the Great Plains
278 J. A. G. REHN
to the Dakotas and western Iowa. A single very distinctive species
is isolated in the extreme southeastern United States. The greatest
specific diversity of Arethaea is in southwestern Texas and adjacent
Mexico, and only one species reaches westward to southern Cali-
fornia and southern Nevada. Another genus with a similar, and
clearly Sonoran, pattern of development and distribution is
Dichopetala, a thamnophilous flightless genus of nearly a score of
species, which range from Oklahoma, Texas, New Mexico, southern
Arizona, and southern California southward to the Rio Balsas
Valley and northern Vera Cruz, Mexico, with several species simi-
larly referred generically from Peru and Ecuador. However, its
greatest specific development is in southern Texas and the north
and central parts of the Mexican tableland and its bordering
eastern Cordillera. It is possible that the South American species
may require generic separation or that they represent a southward
extension of the genus across the "Panama fault," rather than the
more usually postulated one of a reverse movement. However, the
maximum diversity of Dichopetala is clearly in the Sonoran region,
very largely east of the Continental Divide.
The genus Scudderia, which apparently developed from a Neo-
tropical center, includes a certain number of species limited to
Central America, and others intrusive into the western United
States from Mexico. However, a secondary evolutionary center
most certainly developed in the southeastern United States. From
that area, apparently some of the most distinctive members of the
genus extended. Several broadened their range into the western
United States, reaching the Pacific Coast, and also into southern
Canada. The genus Amblycorypha, which probably came from a
Neotropical ancestral stock, developed an evolutionary center in the
eastern and southeastern United States. Four of its five lines center
there, whereas only one is definitely Sonoran. The Sonoran line ex-
tends narrowly along the Mexican border area from western Texas
and Coahuila to southern Arizona. The broad north to south range of
Amblycorypha in western North America reaches from southern
Manitoba and Wyoming to Zacatecas, Mexico.
The subfamily Pseudophyllinae, which is a greatly diversified
and remarkably developed, almost entirely pantropical, assemblage
is represented in North America by a single tribe, the Pterophyllini,
which may be called the "true katydids." This tribe is a Neogaeic
DERMAPTERA AND ORTHOPTERA 279
group that has three peculiar genera In North America, two in the
West Indies and one in South America. The center of development
of the North American elements of the subfamily seems to have
been eastern and midland North America, where two (Pterophylla
and Lea) of the three genera are most diversely developed, while
the third (Paracyrtophyllus) is essentially Campestran and Sonoran.
No member of the tribe is found west of the Continental Divide.
The Copiphorinae is a subfamily of broad distribution, more
strongly developed in the Neotropical Region than elsewhere.
While a number of its genera occur in Mexico, Central America, and
the West Indies, but a single genus, the predominatingly Neo-
tropical Neoconocephalus, enters w^estern North America. It occurs
but sparingly In the Campestran area. West of the Continental
Divide a single species has been taken in southern Arizona and
southern California. It may be intrusive from Mexico, where the
same species is broadly distributed. Any such intrusion seems to be
largely or wholly unrelated to the marked secondary developmental
center for Neoconocephalus in the southeastern United States, that
Is clearly indicated by the varied lines of the genus there present and
In part there limited.
The subfamily Conocephalinae includes the small species of
katydids often referred to in economic works as "meadow grass-
hoppers." One of its two genera found within western North
America, Orchelimum, is strongly developed in the eastern and
central United States, and reaches into the Sonoran In Texas and
eastern Mexico. A single sub-boreal species extends from eastern
Canada across the northern United States to Montana, Washington,
and northern California. Orchelimum, while known only from Amer-
ica north of Tehuantepec, is closely related to the very widely
spread genus Conocephalus, and probably represents a line that has
developed in our territory from the Conocephalus stock. Like
Neoconocephalus, Orchelimum prefers grassy and usually quite
moist meadows, and unless the continuity of such conditions has
been assured, as In the eastern and southeastern United States,
Orchelimum is usually not present, and hence we do not find in west-
ern North America the varied representation of Orchelimum that is
present to the eastward. The nearly cosmopolitan genus Conoce-
phalus has habits rather similar to those of Neoconocephalus and
Orchelimum, and but four of the eighteen species known from
280 J. A. G. REHN
North America occur west of the Continental Divide. Two of the
three subgenera of Conocephalus known from North America are
almost entirely confined to the eastern and central parts of the
continent. We doubtless received the ancestral stock of these lines
from the Neotropical Region well before the Pleistocene, and they
probably evolved almost entirely in the southeastern United States
between their advent there and the present. It is also quite probable
that the two forms of the genus peculiar to the western United
States have evolved from eastern species, while the other two there
present are relatively localized western extensions of broadly
dominant eastern species.
Until very recently the subfamily Listroscelinae was not con-
sidered to be present in North America or even in Mexico. Recent
work has shown that the genus Rehnia, which occurs from Kansas
to the Rio Grande and southward into northern Mexico, and there
westward to Sinaloa, is a member of the Listroscelinae, a subfamily
chiefly of pantropical distribution, with a number of most distinc-
tive genera in South America. Apparently Rehnia is a bush- and
tree-loving Sonoran development from a line of the subfamily,
the entry of which into our general region from a Neotropical stem
probably dates back a considerable time. Another genus of the
same subfamily Neobarrettia is an inhabitant of the very hot Rio
Balsas Valley of Guerrero, Mexico, while the remainder of the
Neogaeic genera of the subfamily occur almost exclusively in South
America and more southern Central America.
The subfamily Decticinae is made up of a very extensive array of
genera occurring almost entirely in the Nearctic and Palearctic re-
gions. A very few narrowly extend southward and several isolated
genera are known from South America. A large percentage of the
members of the subfamily are bush- or thicket-loving species,
but some are grassland types, and others live entirely on the ground
in forested areas; a very few, such as the Mormon cricket {Anabrus)
and the coulee cricket (Peranabrus) are often economic problems,
and these latter, although flightless, have well-developed migratory
instincts when in search of food. In North America only one genus
{Atlanticus) is limited to its eastern part, while twenty-one genera
are known from, and all but one are peculiar to, the western part of
our continent. One interesting peculiarity is that the one eastern
genus, Atlanticus, is the only one having its greatest diversity in
DERMAPTERA AND ORTHOPTERA 281
our continent that is also found outside of North America (in the
last few decades a fair number of species of the genus have been
made known from eastern Asia). This distribution is paralleled in
part by the acridid genus Zubovskya, the blattid genus Cryptocercus
and also by numerous genera of trees and shrubs which have similar
patterns of discontinuous distribution and are now unrepresented in
western North America.
Of the various genera of the Decticinae in western North America,
a single genus {Metrioptera, s. 1.) is shared with the Palearctic
region. This genus with us is a truly boreal type, not occurring south
of Alberta. Its nearest relative is considered by some European
authorities to be M. iissuriana of the Soviet Far East. Of truly
Sonoran development we would regard the genera Eremopedes and
Pediodedes. Genera limited to, and probably developed in, the very
arid western section of the Sonoran are Anoplodiisa and Ateloplus.
The genus Aglaothorax is limited to the Mohave Desert and the
Great Basin, and to the latter the exceedingly rare and local Za-
cydoptera is also restricted. Plagiostira, although chiefly a Great
Basin genus, extends southward over parts of the Arizona Plateau
and eastward into sections of New Mexico, and Capnobotes, which is
chiefly a western Sonoran type, also extends northward in mountain-
ous portions of the Great Basin.
Probably originally of Sonoran origin, but now extending its
distribution widely over the Great Basin and the Columbia Plains,
and even to very considerable elevations in the Rocky Mountains,
is the genus Anabrus, the dreaded Mormon cricket. In the north-
western United States are two endemic decticid genera, Pemnabriis
the economically important coulee cricket, and Apote, which is
chiefly localized in the Columbia Plains, but reaches southern
British Columbia and is apparently restricted in its occurrence. It
is possible that further study may show that both Anabrus and
Peranabrus have Palearctic relationships, and the same also may be
true of Apote. Material for such study is now available and will be
used in the near future.
In the broadly Pacific area from British Columbia to southern
California are a number of clearly endemic genera of Decticinae,
such as Neduba, which often is taken on the ground in heavy conif-
erous forests from British Columbia to the mountains of southern
California, and Idiostatus, from more arid regions of the same
282 J. A. C;. REHN
general territory east to Montana, while the little-known Oreo-
pedes and Crytophylliciis are Sierran endemics, occurring respectively
on the eastern and western slopes. Only at high elevations in the
Sierras, generally above timberline, occurs the flightless Acrodectes,
which is known from the summit and vicinity of Mount Whitney,
and which also may be found to have Palearctic affinities. Californian
endemic decticid genera of lower levels are Idionotus, Decticita,
and Clinopleura. The last-named genus apparently developed from
the same basic line as the genus Steiroxys, which is chiefly a Cordill-
eran and Great Basin type, with, however, a few records from east
of the Rockies (its distribution as a whole is at present poorly
understood). It is possible that Clinopleura and Steiroxys may be
found to have Palearctic affinities.
It is possible, and even probable, that a comprehensive study,
now outlined, may show that the very complex and greatly dif-
ferentiated decticid fauna of western North America represents
several lines of infiltration of Palearctic elements, and that they
have come into our territory long since the sole eastern representa-
tive of the subfamily, Atlanticus, either moved into our territory
from eastern Asia, or conversely traveled to the latter area from
eastern North America, where today it has a number of distinct
specific lines. Clearly, however, a number of our genera of western
North American Decticinae, such as Aglaothorax, Neduba, Zacy-
cloptera, Capnobotes, and Plagiostira, have no approximate counter-
parts in the Palearctic region, while others, such as Eremopedes,
Pediodectes, Ateloplus, Idiostatus, and Idionotus, exhibit almost as
well-marked differences and represent distinct lines from the many
Old World genera of the subfamily. Certainly a very considerable
period of time, isolation, and evolutionary pressure and oppor-
tunity has been required to make evident what we see in our western
American Decticinae.
Family Gryllacrididae. The Gryllacrididae, for which the most
generally used vernacular name is "camel crickets," are an ex-
tremely complex and difficult group systematically. Their ancestral
stock, according to Zeuner, who is probably our most able scholar
in this respect, diverged from the Protorthoptera probably in the
Mesozoic. What he regards as ancestral stocks have been found in
the Upper Jurassic of Solenhafen, although typical Gryllacrididae
are not known from earlier than the Tertiary. Several genera from
DERMA PTERA AND ORTHOPTERA 283
the Florissant Miocene have been referred to the family. The
majority of fossil forms, which can in a general way be associated
with this family, or superfamily as some regard it, belong to the
family Prophalangopsidae, or the subfamily Prophalangopsinae,
depending on the rank accorded it, and occur in deposits as old as
certain Mesozoic formations of Turkestan. Two living genera have
been referred to this assemblage, one Prophalangopsis of India
(known only from the unique type taken nearly ninety years ago),
and Cyphoderris of the northwestern United States and adjacent
Canada. Cyphoderris, however, has by some authors been referred
to the gryllacridine subfamily Heniclnae, in which nearly two
score existing genera have been placed (the majority of these genera
occur only in the Southern Hemisphere, from which several reach
northward in the Neotropical Region to Central America and the
Greater Antilles). The Henicinae are also regarded as having a
single representative within our territory in Cnemotettix, an endemic
genus of San Clemente, one of the Californian coastal islands.
Except for the two Nearctic genera which have been placed in it,
the members of the Henicinae occur in areas which could be asso-
ciated as parts of the often postulated "Gondwan aland." There can
be no question but that Cyphoderris is a relict genus, and of a line
that definitely has long passed its optimum development. It also
should be noted that the area where Cyphoderris occurs is also the
chief center in the New World of Grylloblatta, which is probably the
most aberrant and primitive orthopteron still existing.
The subfamily Stenopelmatinae, which has fossil representatives
as far back as the Lower Miocene of Croatia, is well represented in
western North America, but only by the typical genus Stenopel-
matus, which apparently developed from a Sonoran center, thence
spreading southward at least as far as Costa Rica, and northward
over the campestran Great Plains to the Dakotas and Montana,
over the Great Basin to southern Idaho, and along the Pacific
Coast area to British Columbia, whereas eastward it does not
extend beyond the Great Plains. It is a highly specialized apterous
burrowing genus, whose existing relatives are of South African and
Indian distribution. Its pattern of relationship would indicate the
fragmentation, well in the past, of a once widely spread assem-
blage adapted to subterranean life. The presence of Sienopelmatus
in the New Worid cleariy is not a matter of very recent times. As a
284 J. A. G. REHN
genus, it evidently has evolved in our liemisphere, probably within
the broad limits of the semi-arid and arid Sonoran life center.
In the subfamily Rhaphidophorinae one definitely placeable
genus, Prorhaphidophora, is known from as far back as the Lower
Oligocene amber of East Prussia. Existing members of the subfamily
are wingless, usually nocturnal, and many are cavern-dwelling.
More than a score of genera are represented in Europe, Asia, North
America, Australia, and New Zealand. Only one of the thirteen
genera in North America occurs outside of this continent, and this
genus, Tachycines, is a rather recent accidental introduction from
eastern Asia, now well established under protected conditions in the
eastern and central United States as far west as the Dakotas and
Colorado. The remaining twelve North American genera are all
endemic. They are related to two genera occurring to the southward,
Phoheropiis in the mountains of Central America and Argytes on the
Pacific side of the Mexican Plateau. It is clearly evident that this
assemblage of more than one hundred species, which Hubbell, who
has done detailed work on it, regards as the tribe Ceuthophilini,
has as a whole developed in North America, and to a lesser
degree in adjacent Mexico and northern Central America.
Three of the genera of the Ceuthophilini are western North
American endemics: Tropidischia, which ranges northward in Pacific
territory to British Columbia; Rhachocnemis , which is known only
from the unique type from "California"; and Gammarotettix, which
occurs in various non-desert parts of California, with one species
also occurring about the headwaters of the Gila River in eastern
Arizona. The genus Pristoceiithophilus occurs solely in western
North America from British Columbia to north-central Mexico,
often in montane localities. Styracosceles is limited to areas of the
southwestern United States east to Colorado. The very unusual
recently described genus Salishella is known only from the mountains
of north-central Idaho and the Olympics of Washington. It is a type
of marked specialization, that probably developed in a north-
western center, as it has no close relatives in any surrounding
territory. The genera Daihiniodes and Daihiniella are definitely
Sonoran in their distribution. Ammobaenetes has a similar pattern,
in sand areas. The genus Udeopsylla is truly Campestran. Daihinia
has a similar range, but reaches into adjacent Cordilleran territory.
The widely spread genus Ceuthophilus is represented by some scores
DERMAPTERA AND ORTHOPTERA 285
of species in North America south only to northern Mexico, and
they are considered to have had as their main centers of differentia-
tion (a) the Eastern Deciduous Forest, {b) the Sonoran region, and
(c) the northern Great Basin. In the more arid regions of western
North America specific Hnes of Ceuthophilus appear Hmited to
mountain areas, probably as hot lower levels are less favorable for
their existence. It is very probably that the tribe had a broader and
less localized range in western North America in the moister and
cooler Pleistocene, and that present distributional patterns, as for
many other groups, reflect an average greater aridity in Recent
times.
Superfaniily Gryllodea
The second superfamily of the existing suborder Ensifera, the
Gryllodea, has, in a conservative evaluation of its component
major groups, three families in our fauna, the Gryllotalpidae, or
mole crickets, the Tridactylidae, or pygmy crickets, and the
Gryllidae, to which belong the true crickets.
The oldest fossil of an undoubted mole cricket, from the Upper
Miocene of Germany, is considered to represent an existing genus,
Gryllotalpa, and to be closely related to the existing European
G. gryllotalpa. Zeuner believes that both the Gryllotalpidae and the
Gryllidae have developed independently from the Liassic Proto-
gryllinae, and that the Gryllotalpidae have not evolved through
the medium of the Gryllidae. In western North America we find
but one genus of the Gryllotalpidae, which is variously referred to
as generically identical with Gryllotalpa of the Old World, or
representative of a New World genus Neocurtilla. It is clearly evi-
dent, however, that the two distinct species of this genus in North
America are of Neotropical derivation, as one, found broadly over
the United States west to the Rockies, is also widely spread over
eastern South America, and the other, the sole species occurring
very locally and infrequently from Texas to California, is closely
related.
The position of the Tridactylidae, or pygmy locusts, which were
long considered gryllids, is now regarded broadly as with the
acridids. I mention the group here, as this is the position given in
most past literature. Their ancestral stock is now known from the
Tertiary, but the single genus found broadly in North America
286 J. A. G. REHN
is the almost cosmopolitan Tridactyliis, one of the very few genera
of these strangely specialized orthopterons.
Passing to the true Gryllidae, of which a number of subfamilies
are generally recognized, the Myrmecophilinae, composed of ant
inquilines, is represented in our fauna by the single widely spread
genus Myrmecophila. While members of the genus occur in certain
tropical countries, most of our knowledge of the group has been
drawn from representatives found in more temperate regions. At
least four species occur in western North America. No fossil forms
are known and any postulate as to centers of origin seems at present
unwarranted.
The subfamily Mogoplistinae, of which also no fossil forms are
known, is represented in western North America by two genera, one
of which, Cydoptiliim, is distributed broadly over the southeastern
United States, narrowly enters the Campestran region, extends
from Texas to coastal southern California, and is intrusive in the
Colorado- Virgin rivers area to southeastern Utah. Cydoptiliim is
broadly distributed in tropical regions, even occurring in Polynesian
islands, but it apparently developed certain centers of evolution or
radiation, where a number of distinct species occur, one in the south-
eastern United States, and another in its southwestern section,
Baja California and apparently extreme northern Mexico. The
second genus, Hoplosphyrum, is peculiar to the Sonoran region of
North America, Baja California, and mainland Mexico, with one
species in each of these areas, but it does not, as far as we know,
extend greatly to the southward.
The single genus of the subfamily Nemobiinae in western North
America is virtually cosmopolitan in distribution. The subfamily
is known fossil only from the Oligocene, in Prussian amber and
Isle of Wight deposits. The dominant and widely distributed genus
Nemobius clearly developed an evolutionary center in the eastern
and central United States, where a number of endemic species occur.
Six species and subspecies of the genus occur in western North
America which the genus appears to have entered by this group
from both Mexico and the eastern United States. Several species
are but narrowly present in the southwestern United States. Another
is a Campestran subspecies of an eastern species and reaches the
foot of the Rockies in eastern Colorado. Of two subspecies of a dom-
inant and widely spread eastern species, N. fasciatus, one reaches
DERMAPTERA AND ORTHOPTERA 287
westward as far as Salt Lake City, Utah (possibly an accidental
introduction) and eastern New Mexico, and northward to southern
Manitoba, Saskatchewan, and Alberta, and the other, a more
southern race, extends west to central Texas.
The subfamily Gryllinae is represented in western North America
by three genera, each with a very limited representation of species.
A single species, A. assimilis, of the virtually cosmopolitan genus
Acheta ranges over the greater part of the Neogaeic from Canada
to southern South America. It is now regarded by some as comprising
a group of probably physiological subspecies, as morphologically
these subsidiary elements intermingle to an inextricable degree,
and also they have no clearly defined gc§graphic allocations.
Members of the genus Gryllulus are known from the Tertiary of
both Europe and Argentina, and it is probable that in the New World
Gryllulus has had a very ancient history, but fossil evidence is very
limited.
The genus Miogrylliis, which is represented in western North
America by two species, is clearly of Neotropical origin. Members
of the genus, including one of those found in North America, ran ge
southward to central Argentina, while others are more closely lim-
ited in the Neotropical Region. One of the North American species
is known in our territory only from a portion of the southwestern
United States, reaching from southern California to portions of
Texas and eastern Colorado. The second species, which is that also
of wide Neotropical distribution, occurs rather broadly over the
southeastern and central United States westward to Nebraska,
Kansas, Oklahoma, and central Texas.
The genus GryUita is also Neotropical. The one species known in
the southwestern United States, has been found only in the
Baboquivari Mountains of Arizona, only a few miles from the
Mexican border, south of which undoubtedly the species also occurs.
Other members of the genus GryUita are known from more southern
Mexico, Central America, and the Greater (Cuba) and Lesser
(St. Vincent) Antilles, and its occurrence within our territory has
clearly been due to extension from a more austral center.
The subfamily Oecanthinae is a cosmopolitan assemblage, includ-
ing the so-called tree crickets, because many of them frequent the
foliage of trees or bushes. The little we know about them as fossil
forms is that specifically unidentifiable remains have been found
288 J. A. G. REHN
in the Lower Oligocene and Upper Miocene of Germany and France.
In the present world fauna members of the subfamily are to be found
wherever their chosen environment exists in virtually all parts of
the temperate and tropical regions. They are represented in the
Nearctic fauna by two genera, one of which Neoxabea occurs in
Nearctica only in the eastern part of North America, but other
members of that genus are well distributed over the Neotropical
Region south of Mexico, as far as northern Argentina. The other
genus, Oecanthus, is cosmopolitan over the temperate and tropical
parts of the world, but its greatest concentration of species is in
North America. A definite area of marked specific differentiation is
in eastern North America, and three of the four specific lines of the
genus represented in western North America, are there at the
extreme western limits of distribution of more widely spread and
dominant eastern species of the genus. The status of at least one of
the endemic species reported from the western United States is at
present uncertain, but another one, 0. calif ornicus, is clearly autoch-
thonous and doubtless will be found to extend into northern
Mexico.
The subfamily Pentacentrinae is an aberrant group of small
crickets broadly distributed within the tropics. A single genus,
Trigonidomimus , enters our territory in central Texas, while to the
southward it ranges across Mexico and Central America to Panama.
The other genera of the subfamily are known from Brazil, Cuba,
Madagascar, West Africa, Ceylon, and Formosa. Clearly Trigoni-
domimus entered our territory from the Neotropical Region. No fossil
members of the subfamily are known.
A single genus, Anaxipha, of the subfamily Trigonidiinae is
represented within western North America by one species which is
largely eastern in its distribution, reaching to central Texas and to
the eastern parts of Nebraska and Kansas. The subfamily is found in
virtually all the warmer parts of the earth, on foliage or in low
plant cover, and is also represented in Pleistocene or post-Pleisto-
cene African copal. The genus Anaxipha is entirely New World
in its distribution, with many tropical American species. A secondary
evolutionary center for the subfamily and also for the genus Anaxi-
pha apparently developed in the southeastern United States,
where several other distinctive genera of the subfamily occur, one of
which is entirely restricted to that area.
DERMAPTERA AND ORTHOPTERA 289
Superfamily Grylloblattoidea
Family Grylloblattidae. The exceedingly strange orthopteron
Grylloblatta, which was first made known by my old friend, Dr. E.
M, Walker, in 1914, from material taken near Banff, Alberta, has
probably provoked more discussion as to its relationship and its
phylogenetic position than any other living insect discovered in
the last half century. Its original describer fully realized the
unique character of the insect and modestly created the family
Grylloblattidae for it. Crampton in 1915 erected the order Notop-
tera to include it, and while some have followed this ordinal arrange-
ment, another school inclines toward the belief that in Grylloblatta
we have a connecting link between the saltatorial Orthoptera (the
true Orthoptera of some present day scholars) and the Oothecaria
(or Dictyoptera) and the Phasmatoidea (or Cheleutoptera). Zeuner
recently succinctly stated, "Since it has a number of features
which are more characteristic of the true Orthoptera, it might
rightly be called a living, though specialized representative of the
ancient Protorthoptera."
Our knowledge of the family Grylloblattidae has grown con-
siderably since Grylloblatta was described. It is now known to be
made up of Grylloblatta, which is entirely Nearctic, Grylloblattina , of
the southern Maritime Provinces of Siberia, and Galloisiana, of
Japan. The genus Grylloblatta contains six species, all from montane
localities in southwestern Canada and the western United States.
They are known from localities in southern British Columbia,
montane Alberta, similar areas in Washington, Montana, Yellow-
stone National Park, the Cascade region of Oregon, and the Sierran
section of California as far south as Mammoth Crest. Almost all
the species seem to have very special humidity and temperature
requirements, occasionally are found in contact with snow or ice,
grow with exceeding slowness, and exhibit numerous attributes
that clearly indicate their overall primitive character. It is clearly
evident that today the Grylloblattidae is a Holarctic assemblage.
Its segregation into three distinctive generic units was probably
accomplished well in the past, as the genera are well defined and
regionally limited. The species of Grylloblatta also show in their
distribution, that the relatively numerous forms of the genus (five)
now known from California, Oregon, and Washington (the last also
reaching northward into British Columbia) apparently differenti-
290 J. A. G. REHN
ated at different periods from the line represented by G. campodei-
formis (the genotype), which ranges in the Cordilleran region from
as far north as Jasper Park, Alberta, to the Yellowstone National
Park. The fact that the Cascadan and Sierran species are more
divergent from campodeiformis, would indicate to me that these
more southern representatives have been established as divergent
entities for a longer time. The greatest known specific differenti-
ation in the family has taken place in North America, and it is fair
to assume that the family had its beginnings in western North
America, and that ancestral lines probably traveled eastward over a
Bering Sea land bridge well in the past. We have parallel cases in
the Orthoptera, such as the decticid genus Atlanticus and the
acrid id Zubovskya.
Superfamily Phasmatoidea
(Cheleutoptera of some authors)
The Phasmatoidea, or "walking-stick insects," are a very dis-
tinctive assemblage, much more diversely developed in the number
of genera and species in certain tropical areas than in more temperate
ones. The areas of optimum differentiation are the Neotropical,
the Indo-Malayan, and the Australian. Africa has in proportion a
relatively smaller representation, even its great forested area
having a much less marked diversity than similar regions in the
Neotropical and Indo-Malayan regions.
In North America we find representations of four entities of
higher rank (variously regarded as families or subfamilies), one of
which, elsewhere entirely Neotropical, occurs in the southeastern
and central United States but does not enter more western territory.
One very distinctive line, which is almost universally regarded as a
family, the Timemidae, with the single genus Timema, is as far as
known restricted to certain areas of the western United States.
Timema possesses a number of unusual, possibly primitive, char-
acters, and its six species are known from well-separated areas in the
mountainous areas of California and of extreme southeastern
Arizona. The species are, as far as known, tree or bush dwelling.
The family is clearly an autochthon of the general area where it is
now found, and it shows a pattern of distribution essentially
parallel to that of the three genera composing the Morseinae of the
Eumastacidae. Perhaps as our knowledge becomes more compre-
DERMAPTERA AND ORTHOPTERA 291
henslve we may find that this, and similar correlations, indicate
parallel spreads of widely distinct entities, but of similar faunistic
histories. While it is purely a postulate, it is my belief that the
distributional evidence here reflects Pleistocene conditions, and
heavier precipitation and lower temperatures then over extensive
areas now largely desert or semi-desert, and that the genesis of the
Timemidae probably took place in California very much before
the Pleistocene.
The subfamily Pachymorphinae, a group widely spread over the
world is represented in much of the western half of North America
by the genus Parabacillus. Its range extends northward over the
Great Plains to the Dakotas and elsewhere into New Mexico, Ari-
zona, southern Nevada, and southern California. While it also ex-
tends a considerable distance into Mexico, its greatest distribution
is northward over the Great Plains, and I would regard it as Cam-
pestran in origin, with closest relationship probably to certain rather
poorly known Asiatic genera.
The subfamily Heteronemiinae is entirely one of Neogaea, with
representatives distributed from Canada to at least Paraguay.
Five genera have been reported from western North America, and
all but one of these I would regard as of Sonoran development.
The exception is Sermyle, which is clearly a Mexican and Central
American Neotropical type, with a single species found in southern
Texas. Of the other four genera, Megaphasma is an endemic usually
infrequent in forest, generally bottom, land of eastern Texas, Okla-
homa, Louisiana, and other Mississippi valley areas, but narrowly
entering the territory we are considering. Two of the three remain-
ing genera, Rhabdoceratiies and Psendo sermyle, are limited to west-
ern North America, except for narrowly reaching into Sonoran
sections of Mexico. They doubtless have developed in the great
Sonoran area, where Pseiidosermyle in particular is a dominant
type. The remaining genus, Diapheromera, is probably also a Sonoran
derivative, for several of its species are limited to that area. One
species of the genus, however, has spread more broadly eastward
over most of eastern North America, and there also has developed a
very distinctive species in the southern Appalachians. The south-
eastern and central United States apparently have served as a
secondary developmental center for the Heteronemiinae, not only
for Diapheromera, but also in producing there an endemic genus
292 , J. A. G. REHN
(Manomera) which Is not found to the westward. However, I would
regard the basic developmental center for Diapheromera as Sonoran
on account of the specific diversity in the genus there.
ORDER ORTHOPTERA: SUBORDER OOTHECARIA
(Dictyoptera of some authors)
Superfamily Mantodea
The Mantodea are represented in western North America by
members of five subfamilies or families (the exact rank of the higher
entities is debatable). Two of these subfamilies are known only from
the New World, while the others are found in both hemispheres.
One of the latter is the Amelinae, which has two genera in North
America, both found only within its western part and in northern
Mexico. These are curious, almost entirely terrestrial mantids, one
of which, Yersiniops, has considerable saltatorial powers. The genus
Litaneutria occurs rather broadly over western North America
and northern Mexico, reaching northward to North Dakota, Mon-
tana, Washington, and extreme southern British Columbia. Yersini-
ops has a more limited distribution, extending from western Texas
westward to central southern Arizona and northward to parts of
Colorado. A related genus, Yersinia, occurs in northern Mexico.
All three genera clearly developed in a Sonoran faunal center.
The widely distributed subfamily Manteinae is represented in our
territory by a single genus, Stagmomantis, which is clearly of
Neotropical origin. Species of this genus range southward to Ama-
zonia. The greatest diversity of Stagmomantis is in Central America,
where a number of lines of the genus not present elsewhere are de-
veloped. It later, probably, spread both to the north and to the
south. In western North America there are four species of Stag-
momantis. S. Carolina, a dominant eastern species, which is also
widely spread southward over Central America and northern South
America, reaches as far westward as the Great Plains in the pan-
handle of Texas, eastern New Mexico, and the Arkansas Valley of
eastern Colorado. 5. gracilipes, a very distinctive type, is known
only from several mountain areas in southern Arizona. 6". californica
occurs rather broadly in desert conditions from western Texas to
southern California, southern Nevada, Utah, and western Colorado.
S. limbata is broadly intrusive from Mexico, where it is widely
DERMAPTERA AND ORTHOPTERA 293
distributed. In our limits it occurs from central Texas and eastern
and northern New Mexico to Needles and Calexico, California.
Within our territory the subfamily Oligonicinae is represented
only by the genus Oligomcella, which, like the subfamily, is clearly
of Neotropical derivation. The two species of the genus within our
limits are known there only from Texas and southern Arizona.
One, which elsewhere has a broad distribution in the southeastern
United States, extends across Texas to its trans-Pecos section.
The other, an intrusive from Mexico, is known only from extreme
southern Texas and southern Arizona.
The subfamily Vatinae, a Neotropical assemblage, includes two
genera that narrowly enter our territory from northern Mexico.
Both also range broadly over Central and South America. One of
these genera, Phyllovales, has a single species of much broader
distribution occurring with us only in extreme southern Texas, and
the other, Vates, is represented by one endemic species in certain
mountain areas of extreme southern Arizona.
The subfamily Photininae, all the other members of which are
entirely Neotropical, is represented in our territory by one species
of the striking genus Brunneria, which ranges from the grass
prairie country of east-central Texas to central North Carolina.
The North American species of Brunneria, B. borealis, is partheno-
genetic — no male has ever been taken, although hundreds of females
have been secured at a considerable number of localities. The genus
has a discontinuous distribution; no member other than B. borealis
is known from north of central Brazil, Paraguay, and northern
Argentina, where other species occur with the male sex as frequent
as the female. All members of the genus are strictly grassland forms,
and the postulate that what we see is a reflection of the far greater
extent and former broader prevalence of grasslands in the Pliocene,
with their marked restriction in the more humid Pleistocene,
with the correlated augmentation of lowland forests in that period
in the tropics, seems to be the logical explanation. A theory of
drift across the Caribbean has been advanced to explain the sit-
uation, but the genus does not occur in northern South America as
far as known, in fact at no place between Texas and territory much
south of the Amazon. Somewhat parallel conditions exist in other
genera of the Orthoptera which are grassland forms, and for which
the same postulate seems applicable.
294 J. A. G. REHN
Superfaniily Blattodea
The superfamily Blattodea or cockroaches is represented in
North America by twenty-seven genera, of which eleven are re-
garded as adventives. Some of these were probably introduced
several centuries ago in the early historic periods of the Atlantic
states and provinces. Others were brought in during the early years
of the present century, particularly from the West Indies. The
original home of a number of these adventives was Africa, and the
early transport was by cargo or slave ships. Of these eleven ad-
ventives, six are now known to be present in western North x'\merica,
namely Supella, Blattella, Neostylopyga, Blatta, Periplaneta, and
Pycnoscelus. Of these Periplaneta was doubtless brought in by the
slave trade, as the genus, while now almost cosmopolitan in the
warmer regions, is clearly a native of Africa, where feral species
of the genus also occur. Supella probably had a similar history in
reaching the West Indies, as it was not known from the United
States until the early years of this century, although its dominant
species, 5. supellectilium, the only one that has reached America,
had long been established in the West Indies. The genera Blatta and
Blattella reached America in much the same way as the black rat
{Rattus rattus) and the Norway rat (Rattus 7iorvegicus) , and their
spread westward across Europe coincided very much in sequence and
time with the spread of the two species of domiciliary rats. Both of
these cockroach genera are probably natives of northeastern
Africa, where a number of feral species of each genera occur.
Pycnoscelus is of Oriental origin, and wild species of the genus
are known from Farther India. Today the domiciliary species,
P. surinamensis, is frequent in subtropical, as well as tropical,
America. It presents another case of usual parthenogenesis.
The Oriental genus Neostylopyga, very readily recognized by
its form and coloration, is common in the Philippines and also over
much of Indo-Malayia, and west to Madagascar and the eastern
coast of Africa. The first report of its one domiciliary species,
A^. rhombifolia, in America was made in 1865. It was reported from
Acapulco, Mexico, and from Venezuela and Argentina. From
Acapulco it has spread to the Cape Region of Baja California,
northward over Sinaloa, and even to the railroad entry port of
Nogales, southern Arizona. Acapulco was the port at which in
colonial days the Spanish galleons from Manila landed their cargoes
DERMAPTERA AND ORTHOPTERA 295
for land transfer across Mexico for shipment to Spain. In coming
years Neostylopyga probably will gradually become established in
parts of the southwestern United States, as well as in much of the
warmer parts of Mexico.
Seven of the blattid genera that are endemic in western North
America can definitely be called Neotropical in origin. The majority
belong to the subfamily Pseudomopinae, which is a cosmopolitan
assemblage that is highly developed in the Neotropical Region.
Of these the genus Euthlastoblatta is known in our territory only
from extreme southern Texas, although other members of the genus
occur southward to Panama. Latiblattella, another basically Neo-
tropical genus, has a single species in western North America,
restricted to certain mountain areas of southern Arizona. A number
of other species of Latiblattella occur in Mexico and Central America,
and one is endemic in peninsular Florida. The genus Ischnoptera is
another very diverse and basically Neotropical genus, of which
two species reach North America: the endemic /. deropeltiformis,
which is widely distributed in eastern North America and reaches
westward as far as central Texas, and /. rufa occidentalism a race of a
widely spread Neotropical species, which has a broad range in
Mexico and Central America, entering our territory only on the
Gulf Coast of Texas.
The flower-haunting harlequin-patterned cockroach Pseiidomops
is another very widely spread Neotropical genus, of which a single
species enters our territory, and is found in Texas north to the
central part of the state. The remaining genus of the Pseudomopinae
in our territory is Parcoblatta, which, unlike all the other genera of
the subfamily, is strictly limited to North America. Of the twelve
species of this genus four eastern ones narrowly impinge on our
territory in eastern Texas; bolliana is found westward to central
and southern Texas, and north to Nebraska; desertae is distributed
from eastern New Mexico to central Texas and Oklahoma ; /zz/^e^-
cens ranges westward to central and southern Texas, north to the
Red River, but not west of Texas; pensylvanica extends west to
central and southern Texas, north to Nebraska; americana is a
Pacific species distributed from Oregon to western Arizona and
Nevada; and notha is an endemic species of certain mountain
areas of central and southern Arizona. Apparently Parcoblatta has
developed from a relatively early Neotropical ancestor, and the
296 J. A. G. REHN
center of differentiation, on the basis of present diversity, pre-
sumably was in the eastern and central United States.
Another subfamily of the Blattodea, the Panchlorinae, aside
from the already mentioned Pycnoscelus, is represented in our terri-
tory by a single species of Panchlora, which may be autochthonous
with us in a circumscribed area. The genus is greatly diver-
sified in tropical America, and also has a few endemic species in
forested West Africa. The single species we have within our bound-
aries, P. cubensis, is broadly distributed to the southward, but
reaches its northern natural limit in the Brownsville area of southern
Texas. This insect is often brought in accidentally in bananas,
but cannot survive our usual winter conditions. The subfamily
Chorisoneurinae is a Neotropical assemblage made up of a large
number of species, although but a single genus and species, Choris-
oneura texensis, reaches our territory, where it ranges rather broadly
over the southeastern United States from North Carolina to eastern
and southern Texas in the Brownsville area. The genus, with us, is
clearly intrusive from the south, for our representative is the most
northern member, and the number of species represented regularly
increases as one goes southward in Mexico and Central America.
The subfamily Attaphilinae, the members of which are ant
inquilines, is represented in our territory by the single genus Atta-
phila, of which the genotypic species is known only from central
Texas. This genus is represented by a number of other species in
South America, and a number of allied genera are found in the
Neotropical Region. It is evident that Attaphila, along with its
host Atta, has been derived from that great center.
The subfamily Corydinae is represented in North America by a
single genus, Compsodes, the sole species of which in our territory is
known from the mountains of southern Arizona and from localities
in south and central Texas and Baja California. The genus, as well
as a number of related ones, is clearly Neotropical in origin. A
number of genera of this subfamily are inquilines with various
Hymenoptera, as well as with Isoptera.
The morphologically very distinct subfamily Polyphaginae is
made up of genera that are largely desert forms, and that show
marked antigeny between their sexes. The greater number of the
genera, and the bulk of the species, are Palearctic, with others
arid Ethiopian. In Neogaea we have representatives of the sub-
DERMAPTERA AND ORTHOPTERA 297
family in North America and in Mexico. The North American
species represent two quite distinct genera, one of which, Arenivaga,
is now considered by Russian colleagues also to include certain
Central Asian species. Of Arenivaga seven species are now recognized
in North America, all but one of which are found within the territory
covered by this symposium. Several also occur in northern Mexico.
The one exception is known only from Florida, but it clearly has
been derived from the Sonoran area where the other species have
developed. The forms of Arenivaga in our territory range from
east-central Texas west to southern California, and north as far as
Monterey, California, St. George, Utah, and Oklahoma. The other
genus Eremoblatta, is more exclusively a desert type. Its distribution
extends from eastern New Mexico and extreme western Texas to
the Mohave and Colorado deserts of California, north to Kern
County, California, and to Las Vegas. Nevada.
The last genus of the Blattodea to be considered is in some
respects one of the most interesting of our North American blattids.
This one, Cryptocercus, is the sole member of the subfamily Panes-
thiinae in the New World. Like many of the other species of the
subfamily it lives in dead wood, can digest cellulose, bores channels
in dead logs, preferably of fir or chestnut, and is also wingless. In
North America the genus, and its single American species, is dis-
continuously distributed. It is found in the eastern Appalachians
and the Appalachian Plateau from New York to Kentucky and
Georgia, and again is present in western Washington, the Cascades
of Oregon, and possibly the Sierras of California. It is absent from
virtually all the Middle West, the Great Plains, the Rockies, and
the intervening basins, even where these are heavily timbered.
Apparently the separation of the two distinct areas of the distribu-
tion of the species has been due to the southward advance of the
lobes of the various Glacial ice sheets, which severed previously
connected areas and isolated the two elements of the species, in the
same way the two segments of the acridoid genus Zubovskya were
developed (but in that case specific entities were established).
The particularly interesting feature in connection with Crypto-
cercus is that it, with several distinct species, also occurs in eastern
Asia. Clearly we have here a case basically parallel to those of the
acridid Zubovskya and the decticid Atlanticus, although the ex-
planations for each may not be identical, but in their patterns they
298 J. A. G. REHN
are clearly expressive of the roles of Bering Sea connections and of
Glacial ice in past biogeographic movements or controls.
CONCLUSIONS
In the absence of adequate fossil evidence which would integrate
with living elements we must draw our relevant evidence from the
known centers of existing genera and their allies. Of the 229 genera of
Dermaptera and Orthoptera that occur west of the eastern edge of
the Great Plains, exclusive of purely Mexican ones, 35% (82 genera)
are clearly Sonoran types, using this term in its broad sense or,
when limited, to that area of the same east of the Continental
Divide. This great evolutionary center has been the outstanding
North American center of generic differentiation for Orthoptera.
In descending importance 14.8% (36 genera) clearly were derived
from the Neotropical Region; 7.3% (17 genera) represent a dis-
tinctive and endemic coastal and non-Sierran montane California
fauna; 6.5% (15 genera) are endemic there and probably developed
in Lower Sonoran Zone deserts; 5.6% (13 genera) are introduced
adventives; 4.8% (11 genera) are at present Sierran endemics and
most probably autochthons, and 5.2% (12 genera) holds for a
group of genera also of Palearctic occurrence or relationship; while
3.9% (9 genera) similarly are Cordilleran in their present distribution
and probable origin. A number of the genera here regarded as
developed in the Sonoran center also moved eastward, and sub-
sequently established specific evolutionary centers in the eastern
and southeastern United States. I regard 8 genera (3.5%) as
derived from purely eastern centers of development. The remaining
4% (13) represents basically Sonoran types that developed sub-
sidiary radiative centers in eastern North America, Mohavan and
Great Basin endemic types, cosmopolitan genera, and others
considered purely Nearctic Boreal and restricted Campestran.
The occurrence of certain genera in both western North America
and eastern Asia leaves unanswered the natural query as to whether
their original center was in the one or the other, with much of the
weight of evidence in some of the genera in favor of a North Ameri-
can, and also definitely pre-Glacial, origin.
1
Geographical Origins and Phylogenetic Affinities
of the Cerambycid Beetle Fauna
of Western North America
E. Gorton Linsley
University of California, Berkeley
1 he two previous papers deal with dis-
tributional patterns, respectively, of groups of cool-adapted an-
imals, including northern and montane insects, particularly caddis-
flies and sawfhes, and of certain free-living terrestrial forms (Orth-
optera and Dermaptera). The Cerambycidae, or long-horned
beetles, as larvae, are mostly internal feeders in living, dead, or
dying woody plants, a fact that has greatly influenced the dis-
tributional and evolutionary history of the family. Nearly 900
species are now known from America north of the Mexican bound-
ary. The adults of a few groups are flightless, but most are relatively
strong but somewhat inefficient fliers. They seek the appropriate
host plant before or after mating and subsequently oviposit in
cracks or crevices in the bark or in notches cut by the female.
The degree of host specificity varies. The forms that attack living
trees and assemble on the host plant for mating usually exhibit the
greatest specificity, and those that attack dead or decomposing
wood, the least. The fact that many of the latter group congregate
on flowers for mating precludes or weakens selection for host
specificity. Thus the close association of Cerambycidae with woody
plants and the varying degrees of intimacy in relation to particular
trees and shrubs must be considered in any analysis of the origins
and affinities of the North American elements of the family.
Based on analyses of contemporary distributions, on phylogenetic
and ecological relationships, and on the limited fossil record, the
North American cerambycid fauna appears to be a complex of
diverse distributional elements or subfaunas, of which five are
rather readily identified: a Holarctic element (largely Ijoreal),
299
300 E. G. LINSLEY
a Neotropical element (largely austral), an Alleghenian element
(centering mainly in the Appalachian and Ozark plateaus), a
Vancouveran element (centering along the Pacific Coast), and a
Sonoran element (centering in southwestern United States and
northern Mexico).
The modern Holarctic and Neotropical constituents are of
relatively recent derivation and endemism is expressed largely at
the species level (Table I). The Alleghenian, Vancouveran, and
Sonoran elements are of more ancient origin, although the first two
were apparently derived largely from an early Holarctic fauna,
and the last originated almost entirely from the early Neotropical.
Much of the endemism in these subfaunas is at the generic level
(Tables I and II).
Table I. Primary
Geographical F
Ian
ges of
Contemporary Species ^
North American Ci
eramb]
y'cidae
Number
Per cent
Holarctic
9
1.03
Nearctic
14
1.60
Alleghenian
264
30.28
Vancouveran
147
16.86
Rocky Mountain
39
4.47
Great Basin
27
3.09
Californian
45
5.16
Sonoran
194
22.25
Austro-Riparian
46
5.28
Neotropical
87
9.98
Totals
872
100
Table II. Con tern
iporary Occurrence
of Genera of Cerambycidae No
Represented in
North America
Number
Per cent
World-wide
4
1.70
Holarctic
34
UA1
Nearctic
10
4.26
Alleghenian
30
12.76
Vancouveran
16
6.81
Rocky Mountain
2
0.85
Californian
18
7.66
Sonoran
44
18.72
Eastern Austral
10
4.26
Neotropical
67
28.51
Totals
235
100
CERAMBYCID BEETLE FAUNA 301
EVIDENCE FROM THE PALEONTOLOGICAL RECORD
In North America, fossil Cerambycidae have been found only in
the Florissant beds of Colorado. The lacustrine deposits at this
site contain abundant plant remains and the richest modern-type
insect fauna yet discovered on this continent. MacGinitie (1953)
made a critical taxonomic and ecological study of the fiora, which he
regards as of Lower Oligocene age but, based upon vertebrate
evidence, R. A. Stirton (w litt.) treats the beds as middle Oligocene.
In any event, by comparing the fossil plant community with
living plant communities and considering the chemical and physical
aspects of the sediments, MacGinitie has reconstructed the en-
vironment as follows:
The Oligocene forest occupied streamside and lakeside habitats in a
piedmont of low relief and moderate elevation which bordered the Rocky
Mountain uplift on the east. The drainage was disorganized and partly
ponded by successive volcanic outbursts which covered the area with
dust, pumice, and mudflows.
The fossil fauna and flora were deposited in the resulting shallow and
ephemeral lakes. The climate was subhumid and warm temperate, not
unlike the present climate of Monterrey, in the state of Nuevo Leon,
Mexico. Warm winters and hot summers prevailed, and abundant sun-
shine is indicated. The vegetation on the high ground, away from the
stream and lake borders, was characterized by pines and evergreen oaks
and was most probably of an open, scrub-forest type, with grass and
microphyll shrubs in the drier areas.
MacGinitie has provided a useful table of the fossil gymnosperms
and angiosperms together with the modern occurrence of the most
similar living species. Of these last, 57.1 per cent are found in
habitats encompassed by a circle of radius 400 miles, centered in
southwestern Coahuila, Mexico, especially in the southern Rockies
of San Luis Postosi and Texas and northeastern Mexico. The west
Mexican and southern Arizona area now contains only three or
four additional species. The Ozark-southern Appalachian area and
the Asiatic area have nearly equal representation and together
comprise 57.1 per cent of the list. These living forms are very
largely mesic, streamside types of warm-temperature aspect, and
many of their fossil equivalents were found by MacGinitie to be
relatively abundant forms. However, nineteen of the Ozark species
are also found elsewhere; only six are unique to the region. The
species now living in California he regards as having no particular
302
E. G. LINSLEY
ecological significance as a group, being either wide-ranging forms
or species with restricted distribution isolated by events of the
late Tertiary and Pleistocene.
Less than thirty species of Cerambycidae have been named from
these beds (Linsley, 1942). Among the species that are well enough
preserved to permit interpretation (Table III), about two-thirds are
northern types and some of these are very close to, if not identical
with, living forms. About half of these belong to genera that are
Table III. Modern Occurrence of Some Genera of Cerambycidae
Represented in the Oligocene Beds of Florissant, Colorado"
Fossil
Recent
Recent
Recent
Recent
Recent
Floris-
East
Alle-
Mexican
Van-
Euro-
Genus
sant
Asiatic
ghenian
Plateau
couveran
pean
Gaurotes
P
3
2
3
1
1
Anoplodera
2 +
12±
12
2
23
20±
Grammoptera
1
2±
3
4
9±
Leptiira
2
10±
5
5
20±
Callimoxys
1
—
1
1
1
Semanotus
1
1
1
3
4
Phymatodes
2
6±
5
10
15±
Pidonia
2
4
1
2±
Saperda
2
8±
15±
1
9±
Dryobius
1
1
Leptostylus
1
6±
15±
1
Psapharochus
1
1
8±
— -
Megacyllene
1
3
8±
Stenosphenus
1
1
12±
« Modified from Linsley (1939, 1942).
^ Numerals indicate approximate number of known endemic species (widely dis-
tributed species excluded).
now more or less equally represented in the present day Vancouveran
and Alleghenian subfaunas. Grammoptera, Anoplodera, Leptura,
and Gaurotes are flower-visiting forms of low host specificity associ-
ated with dead and decomposing conifers and hardwoods; Callimoxys
attacks Ceanothus and certain other shrubby plants (the fossil
form suggests the modern Alleghenian subspecies); Semanotus is
now associated largely with Taxodiaceae and Cupressaceae ; and
Phymatodes includes some species that attack conifers and some that
attack hardwoods (the fossil species resemble the latter). Six species
belong to genera better represented today in the Alleghenian sub-
CERAMBYCID BEETLE FAUNA 303
fauna than in the Vancouveran (Pidonia, Leptostyhis, and Saperda,
now associated with broad-leaved deciduous trees) and four belong
to genera found in the present Alleghenian but not in the Van-
couveran (Dryobius, Slenosphenus, Psapharochus, and Megacyllene,
which are also associated with hardwoods, the last with Gary a and
Robinia, which were represented in the Florissant flora). Among the
fossil genera with recognizable affinities, Protospondylis is apparently
related to the living genera Spondylis (with one species in the
Palearctic Region, one in the Vancouveran subfauna, another on
the Mexican Plateau, but none in the Alleghenian) and Scaphinus
(one living species in the Alleghenian). All known members of this
group are associated with conifers (Pinaceae). Protipochus and
Parolamia appear to be related to forms now living in the Med-
iterranean region. The affinities and/or interpretations of the
remaining fossil genera are obscure.
In Europe among the oldest records for species that might belong
to modern cerambycid genera are fragments from the Middle
Eocene of the Geisel Valley near Halle (Pongracz, 1935). Baltic
Amber contains many fine examples, but these have not been
adequately studied, although modern Holarctic genera are well
represented (Klebs, 1910). From Early and Middle Tertiary,
Handlirsch (1908) listed 70 species, but most need to be reexamined
in the light of current classifications. However, Statz (1938) re-
ported on a small sample of cerambycids from the Middle Oligocene
sediments at Rott am Siebenbirge, all of which could be placed in
modern genera (about half are now Holarctic in distribution, the
remainder Palaearctic) . He emphasized that the varied and rich
growth of deciduous trees and shrubs of the Rott environment
provided an abundance of living and decaying wood for larval
development and numerous composites, umbellifers, and flowering
shrubs for pollen-feeding adults, yet cerambycids represent only
0.6 per cent of the known beetle fauna in contrast to the 9 per cent
of the living forms. Although, in part this may reflect lower pop-
ulation levels in the family, Statz considers that their over-all
representation in the Tertiary record as from 3 to 4 per cent of the
beetle fauna reflects a less highly developed group, at least in the
Early and Middle periods, than at present.
Although no later fossil Cerambycidae are known from North
America, Axelrod (1956) has characterized several Mio- Pliocene
304 E. G. LINSLEY
floral provinces in the Far West. These represent the beginnings of
our modern floral and climatic provinces and undoubtedly had a
profound influence on the distribution and evolution of the present
fauna of cerambycid beetles. In his words:
... a North-coastal province, extending along the coast from Washington
to central California, supported a relict warm-temperature facias of the
Arcto-Tertiary Geoflora. At the north it graded inland into the Columbia
Plateau province which was characterized by a typical temperate Arcto-
Tertiary Geoflora, and which gave way at higher levels and eastward to
a cool-temperate conifer facies. Near its southern margin the North-coast
province merged eastward into a floodplain facies of the Arcto-Tertiary
Geoflora which occupied central California, extending to the foothills of
the ancestral Sierra Nevada. On these better-drained slopes the floodplain
forest was replaced by vegetation representing an ecotone between the
Arcto-Tertiary and Madro-Tertiary Geofloras; owing to its near-coastal
position this ecotone included more humid types than that in west-
central Nevada. At higher levels in the Sierra, Madro-Tertiary species
were supplanted by the more mesic, temperate Arcto-Tertiary plants.
A South-coastal province, extending from coast-central into southern
California, was characterized by arid subtropical climate in which a
relict Neotropical-Tertiary Geoflora was in ecotone with the subhumid
Madro-Tertiary Geoflora. To the eastward, in the drier interior Mojave
province, the Madro-Tertiary Geoflora was dominant, grading northward
rapidly into an ecotone with the Arcto-Tertiary Geoflora in west-central
Nevada.
MacGinitie has contributed to this symposium a vivid account of
the Tertiary climates of western North America. These have pro-
foundly influenced the distributional and phylogenetic histories of
the modern floras of western North America, including the redwood
forest, the black oak-madrone forest, the North Coast Douglas
fir forest, the upland conifer forest of the Sierra Nevada, and the
Rocky Mountain forest (Mason, 1947), which support large seg-
ments of the endemic cerambycid fauna.
According to Axelrod (1948), most of the important trees and
shrubs now characterizing the Redwood, Sierra-Cascade, Rocky
Mountain, and North-coast conifer forests have close equivalents in
the West American Element of Miocene floras from the Columbia
Plateau and adjacent areas. These species are in such genera as
Abies, Acer, Alnus, Amelanchier, Betula, Castanopsis, Chamaecy-
paris, Corniis, Fraxinus, Gaultheria, Libocedrus, Lithocarpus, Ma-
honia, Rhododendron, Rosa, Salix, Sequoia, Sorbiis, Thuja, Tsuga,
CERAMBYCID BEETLE FAUNA 305
and Vacciniiim and their modern counterparts are largely hosts of
Vancouveran Cerambycidae with northern affinities. Regularly
associated with these plants are fossil species that find their nearest
relatives in the temperate, summer-wet eastern portions of North
America and Asia. In the East American Element are fossil species in
genera no longer indigenous to the region west of the Rocky Moun-
tains, such as Carya, Carpinus, Castanea, Fagiis, Liqiiidamhar ,
Nyssa, Taxodmm, and Ulmus, whose closest counterparts are now
found in eastern North America and serve as hosts for Alleghenian
Cerambycidae. Also included in this element are fossil species
of genera such as Acer, Betula, Crataegus, Fraxinus, Popiilus,
Prunus, Smilax, Quercus, and Vaccinium which have their nearest
relatives in eastern North America. Members of the East Asian
Element are distributed in Ailanthus, Cercidiphyllum, Ginkgo,
Keteleeria, Metasequoia, and Pterocarya, genera no longer indigenous
to North America; in species of Carya, Ilamamelis, Hydra?igea,
Ostrya, Lindera, Sassafras, and other genera that are represented
also in eastern North America; and in certain fossil species of
Acer, Abies, Picea, Populus, Quercus, and Prunus, which have
their nearest homologues in the temperate forests of eastern Asia.
Another important modern ecological type, the Woodland
formation, with dominant live oaks and such associated conifers as
pinyon pine, juniper, and digger pine, according to Axelrod, makes
up a prominent part of the Madro-Tertiary Flora, which ranged
widely over southwestern North America in middle and later
Tertiary times. Members of the Sierra Madrean Element have
their nearest equivalent species in summer-wet areas extending
from the Cape region of Baja California across the Sierra Madre
of eastern and western Mexico and into the southwestern United
States. This element includes plants that are no longer represented
generically in California, Nevada, or Colorado, such as Bumelia,
Clethra, Eysenhardtia, Ilex, Pistacia, Rohinia, Sapindus, Ungnadia,
and Zanthoxylum, as well as certain species of Arbutus, Cupressus,
Forestiera, Fraxinus, Populus, Quercus, and Rhiis that now have
their closest homologues in areas with summer rains and mild
winters. The California Woodland Element, with species in such
genera as Celtis, Juglans, Lyonothamnus , Platanus, Pinus, Populus,
Prunus, Quercus, and Umbellularia, finds its nearest relatives
making up living California woodland associations. Cerambycidae
306 E. G. LINSLEY
attached to these woodland associations exhibit both northern and
southern affinities.
Chaparral, according to Axelrod (1948) in such genera as Arcto-
staphylos, Ceanothus, Cercocarpus, Dendromecon, Fremontia, Garrya,
Photinia, Quercus (scrub oak), and Rhus, has a large representation
in the Madro-Tertiary Flora. Close relationship is apparent with
the sclerophyllous associations now in California, Arizona, and
Coahuila. The Cerambycidae now associated with this formation
include several forms with southern affinities discussed below as
"Californian" as well as overflow species classed as Vancouveran.
EVIDENCE FROM PRESENT DISTRIBUTIONAL PATTERNS OF
PHYLOGENETIC RELATIONSHIPS OF CONTEMPORARY
GENERA AND SPECIES
The modern Holarctic elements of the cerambycid fauna appear
to be more or less equally represented in the northern forests and
mountainous regions of Europe, Asia, and eastern and western
North America. Their distribution reflects Postglacial dispersal and
their hosts are largely spruces and other northern and high-elevation
Pinaceae or northern-type deciduous trees as Salix and Populus
(Salicaceae). In western North America these are the dominant
Cerambycidae of the Canadian and Hudsonian life zones, but occur
also in dilute form in the coniferous phases of the Transition and
Upper Austral life zones, and a few species are represented in the
high-altitude coniferous forests at least as far south as Guatemala.
Representative genera of this Holarctic fauna include: Asemum,
Arhopalus, and Tetropium of the Aseminae; Callidium, Semanotus,
Xylolrechiis, and Clytus of the Cerambycinae ; Toxotus, Pidonia,
Grammoptera, Leptura, and Anoplodera of the Lepturinae; and
Monochamus, Acanthocinus, and Pogonocherus of the Lamiinae.
In addition to genera, there are a number of species with a similar
circumpolar or Holarctic distribution. Among these are Tragosoma
depsarium (Linnaeus), Asemum striatum (Linnaeus)^, Arhopalus
rusticus (Linnaeus), Stenocorus inquisitor (Linnaeus), Acmaeops
pratensis (Laicharting), Pachyta lamed (Linnaeus), Judolia sex-
macidata (Linnaeus), and Saperda popidnea (Linnaeus). The last
of these is associated with poplar, the remainder with conifers.
The recent neotropical elements, derived from areas of high
temperatures and humidity and attached largely to southern-type
CERAMBYCID BEETLE FAUNA 307
hardwoods and Leguminosae, have penetrated northward very
unequally. They are largely restricted to the Austro-Riparian belt
bordering the Gulf of Mexico, the Atlantic coastal plain, and a few
warm river valleys as those of the Mississippi, the lower Rio Grande,
and the lower Colorado. About a half dozen wide-ranging species
in this category reach southeastern California, e.g., Achryson
surinamiim (Linnaeus), Dendrobias mandibidaris Audinet-Serville,
Lissonotus flavocinctus Dupont.
Representatives of the recent Neotropical elements of the Ne-
arctic region include the following genera: Archodontes and Steno-
dontes (Prioninae); Strangalia, Euryptera, and Ophistomis (Lep-
turinae) ; Sniodicum, Eburia, Elaphidion, Chion, Psyrassa, Heter-
achthes, Ibidion, Plinthocoelmm, Megacyllene, Euderces, Rhopalop-
hora, Ancylocera, Agallisus (Cerambycinae) ; and Lagocheirus,
Leptostylus, Leiopus, Lepturges, Eupogonius, Oncideres, Ecyrus,
Ilippopsis, and Spalacopsis (Lamiinae). Some of these groups
apparently came into North America by way of the Antilles and
are poorly represented on the coastal plain of Mexico, e.g., Spala-
copsis. The majority of the species of West Indian origin are not
found north of the southern tip of Florida, most appear to be recent
arrivals, and none has reached western North America. However,
the largest representation of subtropical Cerambycidae in the United
States is found in the lower Rio Grande Valley of Texas. More than
eighty species have been collected in this area, and all have southern
affinities. Twenty-two occur also in the Austro-Riparian or Carolin-
ian life zones of southeastern United States, ten in the Sonoran
subfauna, and the remainder are strictly Neotropical. Thus these
faunal elements bear little relationship to those of western North
America. Only one austral genus, Neoclytus, has successfully in-
vaded all the northern forests, and it is extremely doubtful if this
is a recent arrival. The genus is most highly developed in South
America and is entirely absent from the Old World, thus suggesting
southern affinities, yet its wide distribution in North America
indicates that it must have been established very early in the
Tertiary. The majority of the species feed upon broad-leaved and
hardwood trees, but N. nubiliis Linsley and A^. muricatuliis Kirby
are restricted to conifers.
The term "Alleghenian" was proposed by Wallace (1876) to
designate a large area covering much of eastern North America
308 E. G. LINSLEY
More recently it has been used in reference to the subfauna that
centers in the Appalachian and Ozark plateaus. It includes a large
number of endemic cerambycid genera and species. The affinities of
these beetles are predominantly and clearly northern, but in many
respects their relationships appear to be nearer to those now found
in the Japano-Manchurian region than with those in the present
day Vancouveran of western North America. Unlike the recent
Holarctic elements, which are associated mainly with conifers and
northern type hardwoods, the Alleghenian species are mostly found
on lowland hardwoods, where they exhibit a preference for areas
with warm, humid summers, and apparently have little tolerance
for cold and for high altitudes. Few of the Alleghanian species have
successfully penetrated the Canadian and Hudsonian life zones.
One of the most interesting of the old, relict endemics in the
Alleghenian subfauna is the primitive monotypic genus Scaphinus,
which represents one of the two living genera of its subfamily. Its
only relative is Spondylis, with a single species in the Palaearctic
regions, another in the Vancouveran, and a third in the high moun-
tains of the Mexican plateau. Other endemic genera with relatives
in eastern Asia or southern Europe are: Cytrophorus and Micro-
clytus (the only New World Anaglyptini), Zammodes, Tylonotus,
Physocnemum, Cyrtinus, Psenocerus, Hetoemis, and Dorcaschema.
At least one genus, Michythisoma, is now phylogenetically isolated,
but all its living relatives, although distant, are associated with
northern coniferous forests.
Some endemic Alleghenian species fall in Old World genera not
found elsewhere on this continent (Table IV). Genera like Ropalopus,
Hesperophanes, and Clytanthus, highly developed in the Palearctic
region, have one species each in the Alleghenian subfauna. Other
species, numerous in the Alleghenian, represent Holarctic genera
absent, or nearly so, from the Vancouveran subfauna. The genus
Saperda, with two postglacially dispersed, poplar- feeding species
occurring from coast to coast, includes fifteen endemic species
associated with various deciduous elements of the Alleghenian
forest, and one in the Vancouveran subfauna, S. horni Joutel,
attached to Salix. Similarly, Oherea has eighteen Alleghenian
endemics with various deciduous hosts, and one (0. quadricallosa
LeConte, also attached to Salix) in the Vancouveran. The Old
World-Alleghenian genera Tetrops and Typocerus are both absent
CERAMBYCID BEETLE FAUNA
309
from the Vancouveran, and Gaurotes is represented by only a single
species in that subfauna.
The present Alleghenian subfauna is not, however, entirely
composed of northern elements. A few southern derivatives became
established at a date early enough for them to persist as endemics,
e.g., the clytine genera Glycohius and Sarosesthes, and the lepturine
genera Bellamira, Charisalia, and Strangalia. Several Neotropical
Table IV. Discontinuous Distribution of Some Holarctic Genera of
Cerambycidae Differentially Represented in the Vancouveran and
Alleghenian Faunas of North America"
Western
Eastern
North
North
A merica
A merica
{Van-
South
Japano-
{Alle-
Genus
couveran)
Europe
China
Manchuria
ghenian)
Hesperophanes
7±
1
2
1
Rhopalopus
10+
6
1
Clytoleptiis
8 +
6+
8 +
1
Saperda
1
9 +
3
10±
15±
Oberea
1
8 +
25±
18 +
18±
Spondylis
1
(1)
(1)
Rosalia s. str.
1
1
1
1
Cortodera
10 +
25 +
Xylosteus
1
1
Ergates
2
1
Callimelliim
2
9
Plectrura
1
1
« Numerals indicate approximate numbers of known endemic species.
genera e.g., Neoclytus, Leptostylus, Lepturges, and Leiopus, also give
evidence of having come into the fauna at an early date, and indeed,
some of these are represented in the fossil beds at Florissant. The
early southern elements may be eastern counterparts of the "Cal-
ifornian" discussed below, but in the absence of climatic barriers
that have maintained the integrity of the "Californian" they have
apparently blended with the northern Alleghenian elements and
shared their late Tertiary geological history.
The Vancouveran subfauna (Van Dyke, 1919, et seq.), in its
purest form, occurs along the coast of western North America from
the Aleutian Islands to central California, more broadly in the
310
E. G. LINSLEY
Bitter Root and northern Rocky Mountains, the Cascades, Sierra
Nevada, and the detached mountain systems of southern Cahfornia
and northern Baja Cahfornia (San Bernardino, San Jacinto, and
San Pedro Martir Mountains). In more dilute form, elements are
recognizable in the southern Rocky Mountains as well as in the
high coniferous forests of southern Arizona and northern Mexico
Fig. 1. Primary geographical ranges of some Cerambycidae classed
as Vancouveran in the narrowest sense (dark shading), broader sense
(with addition of intermediate shading), and widest sense (with addition
of lightest shading).
CERAMBYCID BEETLE FAUNA 311
(Fig. 1). These are the dominant Cerambycidae of the Transition
Life Zone of Merriam (1898) and show closer afifinities with those of
Europe and eastern Asia than with their Alleghenian counter-
parts in eastern North America. Thus, in the Vancouveran subfauna,
we find the endemic Opsimus and Dicentrus (only New World
Saphanini), Synaphaeta (only New World genus of Mesosini),
and Brothylus, Leptalia, Ulochaetes, Hybodera, and Lophopogotiius,
all with related genera in the Old World. Several other genera
share species with both the Vancouveran subfauna and those of the
Palearctic Region, but not the Alleghenian (Table IV). These include
Plectrura (one species in Japano-Manchurian region, one in Van-
couveran) ; Spondylis (one species Palearctic, one Vancouveran) ;
Megasemum (one species in Japano-Manchurian, one in Vancouver-
an) ; Callimellum (eight species in southern Europe and Asia Minor,
two in Vancouveran) ; Cortodera (numerous species in both Europe
and Vancouveran) ; Xylosteus (one species in southern Europe, one
in Vancouveran) ; and Rosalia (one species in Japano-Manchurian,
two in south China, one in Europe, one in Vancouveran). Other
genera endemic in the Vancouveran fauna are Xylocrius (two
species), Poecilobrium (one species), Enmichthus (one species),
Holopleura (one species), Ortholeptura (three species), Piodes (one
species), and Pyrotrichiis (one species). Presumably all these have
ancient northern affinities.
The relict trees of the genus Sequoia, growing within the area
occupied by the Vancouveran subfauna, are hosts of several endemic
cerambycid species or subspecies (all members of the tribe Callidini).
These include Callidium vandykei Linsley, C. sempervirens Linsley,
and Semanotus ligneus sequoiae Van Dyke, which are limited to the
coast redwood {Sequoia sempervirens), and Callidium sequoiae
Fisher, on the big tree [S. gigantea). A more striking group of
Cerambycidae is found on the Sargent Cypress (Cupressus sargentii)
which grows only in a few restricted areas of serpentine rock in the
foothills of northern California. Confined to this host are Vatidykea
tuber culata Linsley, Atimia helenae Linsley, and Callidiellum cup-
ressi (Van Dyke). The last species has a close relative, C. rufipenne
(Motschulsky, in Japan, associated with Crytomeria japonica and
Chamaecyparis obtusa, another, C. villosulum (P^airmaire), in China,
on Cunninghamia lanceolata, all members of the Cupressaceae or
312 E. G. LINSLEY
Taxodiaceae. However, Vandykea is isolated taxonomically and
apparently has southern rather than northern affinities, and I
have classed it as "-Calif ornian" (see below).
In Oregon and California, the Sierra-Cascades (arid) phase of the
Vancouveran subfauna is quite distinct from the coastal (humid)
phase, although the two approach each other more closely in Wash-
ington and merge in British Columbia. In general, most Ceram-
bycidae that occur in the Sierra-Cascade Vancouveran are found
also in the coastal phase. Apparent exceptions include: Desmocerus
auripennis Chevrolat, Tetropium ahietis Fall, Oeme calif ornica
Linsley, Pachyta armata LeConte, Leptura obliterata soror LeConte,
Semanotus amethystinus LeConte, Clytus planifrons LeConte, C.
clitellarius Van Dyke, Neoclytus mibilus Linsley, and Leptostylus
nehulosus Horn. Species of the coastal Vancouveran not known to
occur in the Sierra-Cascade phase include: Evodinus vancouveri
Casey, Leptura obliterata obliterata LeConte, Desmocerus cribri-
pennis Horn, Callidium vandyke, C. sempervirens Linsley, Clytus
blaisdelli Van Dyke, and Plectrura spifiicauda Mannerheim. Mela-
nism is a marked characteristic of the humid Vancouveran and is
particularly pronounced in Piirpuricenus dimidiatiis Horn, Necyd-
alis laevicollis LeConte, and Judolia quadrillum LeConte.
The Rocky Mountain area, lying between the Vancouveran and
Alleghenian endemic reservoirs, has few endemic cerambycid genera
of its own (e.g., Elatrotrypes, with ancient northern affinities),
and the intermountain or Great Basin area contains only one,
the monotypic Megascheuma, obviously derived from the austral
Megacyllene and adapted for life in the roots of shrubby compositae.
The present cerambycid fauna is made up primarily of Holarctic
elements of recent origin, with an intrusion of Vancouveran forms,
especially in the north and, to a lesser extent, of Sonoran elements
in the south. A few Alleghenian representatives are to be found on
the eastern slopes of the mountains, emphasizing a long separation
of Vancouveran and Alleghenian elements, and these are mostly
recent arrivals, many of which have followed up the river courses
from the Mississippi Valley, e.g., Neoclytus caprea Say. The Great
Plains area to the east, which apparently began to develop some of
its present characteristics in the Miocene, has produced the prionine
subgenus Homaesthesis, and this, like Megascheuma, exhibits
CERAMBYCID BEETLE FAUNA 313
specialization for life associated with plant roots (in this case, of
prairie grasses).
The endemic Sonoran elements among the Cerambycidae are
almost entirely of early Neotropical derivation (in the geographic
sense) and exhibit various modifications of structure and habit
associated with the arid conditions under which they now exist.
They are characteristic of the Lower Sonoran Life Zone of Merriam
and occupy most of the central and northwestern plateaus of Mexico,
western Texas, much of New Mexico and Arizona, southeastern
California and eastern Baja California, and they are associated
with desert trees, shrubs, and Cactaceae, e.g., Anefliis, Osniidus,
Anepsyra, Rhodoleptus, Metaleptiis, Schizax, Tylosis, PUonoma,
Taranomis, Sphaenolhecus, Batyle, Moneilema, Peritapnia, Coenopiis,
and Glaucotes. Other genera, dominantly Neotropical, but well
represented in the Sonoran (and also in the Austro- Riparian)
are: Derobrachus, Methia, Elaphidion, Ophistomis, Euryptera,
Stenosphenus, Elytroleptus, Stenaspis, Dendrobias, Acanthoderes,
Oncideres, and Ataxia. A major derivative of the Sonoran fauna
occupies the intermountain area of the Great Basin. It is represented
by genera (e.g., Crossidius, Tetraopes, Mecas) associated with the
roots of shrubby Compositae ( as Artemisia and Chrysolhamnus)
and asclepiads. However, in the mountains, Eucrossus and Haplidiis
are present. These are endemic genera with southern affinities,
primarily associated with pinyon pine, which I have classed as
"Californian" in the broad sense. The small endemic subfauna,
designated by Van Dyke (1919) as the " Calif ornian"^ is also
deserving of brief discussion. In its restricted form it occurs from the
middle of the west coast of Baja California to Santa Barbara County
and in the interior from the San Pedro Martir Mountains to the
Tehachapi region of southern California (Fig. 2). This area is
characterized by many endemic groups of insects, particularly in
the Tenebrionidae, and corresponds generally to the center of
distribution attributed to the broad-sclerophyll vegetation of the
Pacific Coast by Cooper (1922), although many of the forest elements
included in his classification could be called " Vancouveran" on the
basis of the Cerambycidae associated with them. In a broader
1 This term is applied in various senses by students of biogeography and ecology.
I have not attempted to determine priority of usage.
314
E. G. LINSLEY
sense the "Californian" includes some elements now occurring in
the foothill region of the western Sierra Nevada and in the eastern
Coast Range, surrounding the great valley of California, and in the
Chiricahua and certain other mountain ranges of southern Arizona
Fig. 2. Primary geographical ranges of some Cerambycidae classed
as Californian in the narrowest sense (dark shading), and intermediate
sense (with addition of the lighter shading). Note that some of these over-
lap the ranges of forms classed as Vancouveran (Fig. 1).
(Fig. 2), and is sparsely represented in the Great Basin montane
(not shown in Fig. 2), Generally speaking, this is the cerambycid
fauna of the Upper Sonoran Life Zone of Merriam, but it is often
mixed with elements derived from the Sonoran and Vancouveran
subfaunas, especially the latter in so far as the Cerambycidae are
concerned.
CERAMBYCID BEETLE FAUNA 315
Like the Sonoran, the "Californian" subfauna has southern
affinities but it is older, perhaps comparable in age with the Vancou-
veran. It exhibits relationship with elements now found in the mon-
tane phases of the Mexican Plateau, but, judging from the beetles,
at least some of its affinities suggest a closer relationship to the
contemporary faunas of the arid and semi-arid west coast of South
America (Peru, Galapagos, Chile, etc.) than to those of humid
tropical America. As has been emphasized previously (Linsley,
1939), it appears probable that some time during the later Tertiary
a series of arid or semi-arid environments permitted the dispersal of
elements between the west coasts of North and South America.
It is possible that these environments were associated with mountain
ranges or chains of islands. At present, portions of the peninsula of
Baja California and the islands off the coast of southern California
exhibit arid (landward) phases and humid (seaward) phases, the
former usually characterized by desert or semi-desert conditions,
and Michener (1954) has emphasized that xeric communities now
exist in the vicinity of the Canal Zone in Panama. Such arid phases
might well have offered north-south dispersal routes for plants and
animals.
Among the Cerambycidae, a typical Californian genus is Ipochus,
a wingless group of closely related species or subspecies which
occupies an area from the middle of Baja California north to Santa
Cruz, California, including Guadalupe and Catalina islands, and
is also represented in the Huachuca Mountains. Other groups with
southern (but not Sonoran) affinities, apparently assignable as
endemics of the Californian in the broad sense, include the mono-
typic genera Megobrium, Eiidistenia, Meganoplium, Paranoplium,
Hesperanoplium, Neobellamira, Triododytus, and Sternidocinus
(associated primarily with oaks and chaparral shrubs); Vandykea,
which is attached to Sargent Cypress; Eucrossus and Haplidus,
occurring primarily with pinyon pine; and the polytypic genus
Poliaenus, with one species limited to Fremontia (a chaparral type),
others to pinyon and digger pines (woodland types).
The California insular fauna has been treated as a subdivision
of the Californian, but among the Cerambycidae, except as noted
for Ipochus (above), no endemic elements are known and typical
Californian elements are present (Fig. 2). Mason (1934) has shown
that the modern closed -cone pine forest now occupies areas that
316 . E. G. LINSLEY
can be demonstated to have been islands in the late Tertiary or
which are insular today (islands off the coasts of southern Califor-
nia and Baja California). Insect distributional patterns reveal a
similar discontinuity, not only among phytophagous wood-boring
forms but in such flightless groups as Pleocoma (Scarabaeidae) and
Omus (Cicindelidae). Among the Cerambycidae, this distribution
is evident in Megobrium edwardsi (LeConte), Ortholeptura insignis
(Fall) (hosts: Piniis muricata, P. radiata), and Paratimia conicola
Fisher (in cones of Pinus attenuata and P. holandari) . Other species
of the old California insular fauna apparently include Sternidocinus
barbarus (Van Dyke) and Necydalis barbarae Van Dyke. The
distribution of the former centers in the Santa Inez Mountains,
the latter in the region from Santa Barbara north to the Santa
Cruz Mountains. The Californian species Ipochus fasciatiis LeConte
and Atimia maritima Linsley, the Vancouveran Xylotrechus insginis
LeConte, and the widespread but austral Romaleum hispicorne
(Linnaeus) all occur today on one or more of the southern California
islands but, with the exception of the first two, give evidence of
being recent immigrants.
SUMMARY
Judging from an analysis of present day distribution and the
limited fossil record, the North American cerambycid fauna is a
complex of diverse elements of which five are rather readily identi-
fied: the Holarctic, Neotropical, Alleghenian, Vancouveran, and
Sonoran. The modern Holarctic and Neotropical constituents are
of relatively recent derivation, and endemism is expressed largely
at the species level. The Alleghenian, Vancouveran, and Sonoran
elements are of more ancient origin, although the first two were
apparently derived largely from an early Holarctic fauna associated
with the Arcto-Tertiary flora, the last almost entirely from the
early Neotropical. Much of the endemism in these subfaunas is at
the generic level.
The modern Holarctic elements are more or less equally represen-
ted in the northern forests and mountainous regions of Europe,
Asia, and eastern and western North America. Their distribution
reflects Postglacial dispersal. Their hosts are largely conifers and
northern-type deciduous trees as Salix and Populus. In western
North America these are the dominant Cerambycidae of the
CERAMBYCID BEETLE FAUNA 317
Canadian and Hudsonian life zones, but they are also represented
in the coniferous phases of the Transition and Upper Sonoran.
The recent Neotropical elements, derived from areas of high
temperatures and humidity and attached largely to southern-type
hardwoods and Leguminosae, have penetrated northward very
unequally. They are largely restricted to the Austro-Riparian belt
bordering the Gulf of Mexico, the Atlantic coastal plain, and a few
warm river valleys like those of the Mississippi, the lower Rio
Grande, and the lower Colorado. About a half-dozen wide-ranging
species in this category reach southeastern California.
The Vancouveran elements, in their purest form, occur along the
coast of western North America from the Aleutian Islands to
Central California, in more dilute form in the Bitter Root and north-
ern Rocky Mountains, the Cascades, Sierra Nevada, San Ber-
nardino, San Jacinto, and San Pedro Martir Mountains. These are
the dominant Cerambycidae of the Transition Life Zone and they
show closer affinities with those of Europe and eastern Asia than
with their Alleghenian counterpart in eastern North America.
The endemic Sonoran elements are almost entirely of early
Neotropical derivation and exhibit various modifications of structure
and habit associated with the arid conditions under which they now
exist. They are characteristic of the Lower Sonoran Life Zone and
occupy most of the central and northwestern plateaus of Mexico,
western Texas, much of New Mexico and Arizona, southeastern
California and eastern Baja California and are associated with
desert trees, shrubs, and Cactaceae. A major derivative of the
Sonoran fauna occupies the intermountain area of the Great Basin.
It is dominated by genera associated with the roots of shrubby
Compositae (as Artemisia and Chrysothamnus) and asclepiads.
A small endemic cerambycid subfauna with southern affinities
occurs from Monterey County, California, to the middle of the west
coast of Baja California and in the interior from the Techachapi
area to the San Pedro Martir; its influence is also seen in the foothill
areas surrounding the central valley of California and in some of
the mountain ranges of southern Arizona. This subfauna, sometimes
called the " Calif ornian," also has an insular phase. Some affinities
with the subfauna now occurring along the arid west coast of South
America but the Calif ornian also has characteristics of its own,
and about a dozen endemic cerambycid genera, mostly mono-
318 E. G. LINSLEY
typic, have been assigned to it. It appears to have been associated
with the Madro-Tertiary Flora.
REFERENCES
Axelrod, D. I. 1948. Climate and evolution in western North America
during middle Pliocene time. Evolution, 2: 127-144.
. 1956. Mio-Pliocene floras from west-central Nevada. Univ.
Calif. Pubis. Entomol..33: 1-322.
Blackwelder, R. E. 1946. Checklist of the coleopterous insects of Mexico,
Central America, the West Indies and South America, Ft. 4. U. S.
Natl. Museum, Bull., 185: 551-763.
Bradley, J. C. 1956. The distribution of northeastern insects. Entomol.
News, 57: 257-261.
Cockerell, T. D. A. 1908. Fossil insects from Florissant, Colorado. Bull.
Am. Museum. Nat. Hist., 24: 59-69.
. 1916. Some American fossil insects. Proc. U. S. Natl. Museum,
51: 89-106.
Cooper, W. S. 1922. The broad-schlerophyll vegetation of California, an
ecological study of the chaparral and its related communities.
Carnegie Inst. Washington Publ. 319: 1-124.
Darlington, P. J. 1938. The origin of the fauna of the Greater Antilles,
with a discussion of the dispersal of animals over water and through
the air. Quart. Rev. Biol, 13: 274-300.
Davis, A. C. 1932. A list of the Coleoptera of Ft. Tejon, California.
Bull. Southern Calif. Acad. Sci., 31: lS-^1 .
Dorf, E. 1933. Pliocene Floras of California. Carnegie Inst. Washington
Publ. 412: 1-112.
Fall, H. C. 1897. List of the Coleoptera of the southern California
Islands. Can. Efitomologist, 29: 233-244.
. 1901. List of the Coleoptera of southern California. Occ. Paper
Calif. Acad. Sci., 8: 1-282.
Fall, H. C, and A. C. Davis. 1934. The Coleoptera of Santa Cruz Island,
California. Can. Entomologist 66: 143-144.
Garnett, R. T. 1918. An annotated list of the Cerambycidae of California.
Can. Entomologist, 50: 172-177, 205-213, 248-252, 281-284.
Gressitt, J. L. 1951. Longicorn beetles of China. Longicornia, 2: 1-667.
Hamilton, J. 1889. Catalogue of the Coleoptera common to North Amer-
ica, Asia, and Europe. Trans. Am. Entomol. Soc, 16: 88-162.
Handlirsch, A. 1908. Die fossilen Insekten und die Phylogenie der rezenten
Formen. Leipzig, pp. 1121-1430.
Hardy, G. H. 1926. Cerambycidae of Vancouver Island. Kept. Prov.
Museum Brit. Columbia, 1926: 1-10.
Horn, G. H. 1876. Notes on the Coleoptera of Guadalupe Island. Trans.
Am. Entomol. Soc, 5: 198-201.
CERAMBYCID BEETLE FAUNA 319
Horn, G. H. 1894. The Coleoptera of Baja California. Proc. Calif. Acad.
ScL, 4: 302-449.
Hulten, E. 1937. Outline of the History of the Arctic and Boreal Biota
during the Quaternary Period. Stockholm.
Klebs, R. 1910. Uber Bernsteineinschliisse im allegemeinen und die
Coleopteren meiner Bernsteinsammlung. Schrift. Physik.-okonom.
Ges. Konigsberg, 51: 217-242.
LeConte, J. L. 1859a. The Coleoptera of Kansas and eastern New Mexico.
Smithsonian Contribs. to Knowledge, 11: 1-58.
. 1859b. Catalogue of the Coleoptera of Ft. Tejon, Calif. Proc.
Acad. Nat. Sci. Phil., 1859: 69-90.
Linsley, E. G. 1939. The origin and distribution of the Cerambycidae of
North America with special reference to the fauna of the Pacific
slope. Proc. Sixth Pacific Sci. Congr., 4: 269-282.
. 1942. A review of the fossil Cerambycidae of North America.
Proc. New Eng. Zool. Club, 21: 17-42.
Linsley, E. G., and J. O. Martin. 1933. Notes on some longicorns from
subtropical Texas. Entomol. News, 44: 178-183.
MacGinitie, H. D. 1953. Fossil plants from the Florissant beds, Colorado.
Carnegie Inst. Washington, Publ. 599: 1-198.
Mannerheim, G. C. G. 1843. Beitrag zur Kaefer-Faana der Aleutischen
Inseln, der Insel Sitkha und New-Californiens. Bull. Soc. Naturalistes
Moscoiv, 16: 175-314.
. 1846. Nachtrag zur Kaefer-Fauna der Aleutischen Inseln und
der Insel Sitkha. Bull. Soc. Naturalistes Moscow, 19: 501-516.
• — — ■ — . 1852. Zweiter Nachtrag zur Kaefer-Fauna der Nord-Ameriken-
ischen leander des Russischen Reiches. Bull. Soc. Naturalistes Mos-
cow, 25: 283-387.
1853. Dritter Nachtrag zur Kaefer-Fauna der Nord-Ameriken-
ischen leander des Russischen Reiches. Bull. Soc. Naturalistes
Moscoiv, 26: 95-273.
Mason, H. L. 1934. A Pleistocene Flora of the Tomales Formation.
Carnegie Inst. Washington, Publ. 415: 81-179.
— ■ — ■ — . 1936. The principles of geographic distribution as applied to
floral analysis. Madrono, 3: 181-190.
. 1947. Evolution of certain floristic associations in Western North
America. Ecol. Monographs, 17: 201-210.
Merriam, C. H. 1898. Life zones add crop zones of the United States.
U. S. Dept. Agr., Bur. Biol. Survey, Bull. 10: 7-79.
Michener, C. D. 1954. Bees of Panama. Bull. Am. Museum Nat. Hist.,
104: 5-175.
Mitono, T. 1940. Cerambycidae. Catalogus coleopterorum japonicorum,
pars 8: 1-283.
Pongracz, A. 1935. Die eozane Insektenfauna des Geiseltales. Nova
Acta Leopoldina Carol., 2: 483-572.
320 E. G. LINSLEY
Schaeffer, C. 1908. List of longicorn Coleoptera of Brownsville, Texas,
and Huachuca Mts. Bull. Brooklyn Inst. Arts Sci., 1: 325-352.
Scudder, S. H. 1878. An account of some insects of unusual interest from
the Tertiary Rocks of Colorado and Wyoming. Bull. U. S. Geol.
Geog. Surv. Terr., 4: 519-543.
. 1890. The Fossil Insects of North America, with Notes on Some
European Species. New York. 2 vols.
Statz, G. 1938. Funf neue fossile Cerambyciden-Arten aus den mitteloli-
gocanen Ablagerungen von Rott am Siebenbirge. Entomol. Blatter,
34: 173-179.
Van Dyke, E. C. 1919. The distribution of insects in western North
America. Ann. Entomol. Soc. Am., 12: 1-12, map.
. 1924. The Coleoptera collected by the Katmai Expeditions.
Natl. Geogr. Soc. Contrihs., Tech. Paper 2: 1-26.
. 1926. Certain peculiarities of the Coleopterous fauna of the
Pacific Northwest. Ann. Entomol. Soc. Am., 19: 1-12.
1929. The influence which geographical distribution has had in
the production of the insect fauna of North America. Trans. IV
Intern. Congr. Entomol., 2: 555-566.
Vogt, G. B. 1949. Notes on Cerambycidae from the Lower Rio Grande
Valley, Texas. Pan-Pacific Entomol., 25: 137-144, 175-184.
Wallace, A. R. 1876. The Geographical Distribution of Animals. London.
2 vols.
Wickham, H. F. 1911. Fossil Coleoptera from Florissant, with descrip-
tions of several new species. Bull. Am. Musem Nat. Hist., 30: 53-69.
. 1912. A report on some recent collections of fossil Coleoptera
from the Miocene shales of Florissant. Univ. Iowa Lab. Nat. Hist.,
6: 49-67.
. 1913a. Fossil Coleoptera from the Wilson Ranch near Florissant,
Colorado. Univ. loiva Lab. Nat. Hist., 6: 3-29.
. 1913b. The Princeton collection of fossil beetles from Florissant.
Ann. Entomol. Soc. Am., 6: 359-366.
— . 1913c. Fossil Coleoptera from Florissant in the United States
National Museum. Proc. U. S. Natl. Museum, 45: 283-303, 5 pis.
. 1914a. Twenty new Coleoptera from the Florissant Shales.
Trans. Am. Entomol. Soc, 40: 257-270, pis. 5-8.
. 1914b. New Miocene Coleoptera from Florissant. Bull. Museum
Comp. Zool. 58: 423-492.
. 1916. New fossil Coleoptera from Florissant. Bull. Nat. Hist.
Soc. Univ. Iowa, 7 : 10.
1917. New species of fossil beetles from Florissant, Colorado.
Proc. U. S. Natl Musevm, 52: 463-472.
14
Distribution of Butterflies in the New World
William Hovanitz
Department of Biology, California Institute
of Technology, Pasadena
1 he butterfly fauna of North America is proba-
bly better known than that of any other large group of insects.
The reason for this is clear: butterflies are day fliers and thus are
apparent to everyone. They are brightly colored and therefore have
been collected for non-scientific purposes, for collection hobbyist etc.
The result of this activity has been both advantageous and disad-
vantageous to the knowledge of the group from a scientific stand-
point. On the advantageous side is the tremendous job done by the
non-scientific or semi-scientific workers on ferreting out butterfly
haunts over the entire world and making this information available
in collections and the literature, so that the geographic distributions
of this group of insects is better known than that of any other. On
the disadvantageous side is the lack of organized study on the
butterflies due to lack of biological education by the hobbyists on the
one hand, and lack of much work by scientific workers created by
fear that work in this field will place them in the light of immature
or peculiar "butterfly collectors."
Butterflies are a major evolutionary branch of Lepidoptera,
adapted to day-flying habits. It is not certain that the group as a
whole has had a common origin, or is therefore a natural group. It is
almost certain that the skippers (Hesperiidae) originated inde-
pendently. No data are given for the Hesperiidae because they are
not regarded as naturally related to the other families, even though
they have commonly been considered to be a part of the butterflies,
and because the taxonomy of the group involves special problems
that do not lend themselves well to this analysis.
The families of butterflies other than the Hesperiidae are fairly
distinct, but appear to be closely related. All groups seem to have
had a past history of tropical origin. Since their body temperature
321
322
W. HOVANITZ
approximates that of the environment, their activity depends on
warmer temperatures. The PapiHonidae, Pieridae, Danaidae,
Morphidae, Satyridae, Brassolidae, NymphaHdae, Erycinidae, and
o
•< o
PAPIL ION I OAE
Fig. 1. New World distribution of butterfly families.
Lycaenidae are all represented by far more genera or species in the
tropical parts of the world than in the temperate or boreal parts.
Independently, certain genera or species of some of these families
appear to have become adapted to life in colder regions, so that
some of these would be considered as arctic types or temperate types,
despite the fact that the family as a whole is tropical.
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 323
DISTRIBUTION OF MAJOR GROUPS (EXCLUSIVE OF THE
HESPERIIDAE)
The distribution of the major taxonomic groups In North and
South America is shown by a series of histograms (Figs. 1-19). The
histograms are constructed In the following manner. Blocks indi-
cating distributional range are drawn on a scale from left = north to
right = south, reading from 82° N. Lat. to 55° S. Lat. Each block
covers 5° of latitude and 1,000 meters of elevation above sea level.
For example, in the charts on distribution of the Paplllonldae (Figs.
2-3), if a species exists at an elevation of 1,500 meters at 46° S.
Lat., this fact is indicated by a block extending from right to left
at 45°-50° S. Lat. and up and down from 1,000 to 2,000 meters. On
some histograms, where the data warrant and the distributional
relations are thereby clarified, the bars are terminated between the
arbitrary 5° class limits, and, occasionally, the altltudlnal limits are
set at 500-meter intervals. Where the ranges are disjunct, a line has
been drawn to connect the base of the separated parts. Where the
altltudlnal information on a genus Is inadequate, the latitudinal
distribution is indicated by a thin line.
For comparison with these ranges, a histogram is shown at the
top of each figure to indicate the extent of land and habitat avail-
able in North and South America, for the absence of a butterfly
group in any area may be caused by the absence of a particular
elevation at a certain latitude so that no habitat Is available there.
This comparative chart is drawn In the same way as those for the
butterflies, with the exception that blocks of 1° latitude are used in-
stead of 5°. Also, since in some areas high elevations are represented
solely by a few mountain peaks, these are indicated by the sign A ,
while short ranges are Indicated by H, mountain passes (breaks In
distributional ranges) are indicated by U, and three areas of nearly
complete break in the cordillera are indicated by v .
All areas potentially inhabitable by butterflies are shaded ; areas
of perpetual frost or cold, in Greenland and southern Chile, are
unshaded.
Generic names of the butterflies are taken from Seitz's Macro-
lepidoptera of the World, even though it is now known that many of
these are not correctly used. The reason for this usage is to avoid
difficulty in identification due to conflicting opinions.
From the chart of the families (Fig. 1) it can be seen that the
324 W. HOVANITZ
Papilionidae inhabit America from 68° N. Lat. to 35° S. Lat., and
range to their highest elevations (4,000-5,000 meters) in the lati-
tudes 35° N. to 49° N. only. South of 35° N. Lat., the elevation drops
ofif to less than 3,000 meters, south of 10° S. Lat. to 2,000 meters,
and south of 20° S. Lat. to 1 ,000 meters. This distribution indicates
a large tropical group of Papilionidae that does not exist in the
higher, colder parts of the Andes, and also indicates a northern
group that exists in the far north and in the mountains of the tem-
perate zone. This northern group apparently has not been able to
extend southward into the mountains of the tropical regions.
The Pieridae on the other hand have a wider range, extending
from 82° N. Lat. to 55° S. Lat. — the entire possible range of land.
They also inhabit the largest part of available elevations at all
points, and are absent primarily only from the higher elevations in
the extreme north and south. For further understanding of this
group one must study its constituents in the following charts.
The Danaidae occupy primarily a centralized tropical position,
from 40° N. Lat. to 30° S. Lat., and occur at high elevations only in
the equatorial regions. Summer extensions of range are shown by
white bars to 55° N. Lat. and to 55° S. Lat.
The Morphidae are indicated to be even more tropical, as they
probably do not reach the Tropic of Cancer and extend little beyond
the Tropic of Capricorn. Within these limits, however, they range
locally up to 3,000 meters. The range in the south (to 28° S.) is
greater than in the north (to 20° N.).
The Satyridae are indicated to have a very complex distribution,
covering most available habitats from north to south and at all
elevations. In distribution they resemble the Pieridae, but they do
not extend quite so far north.
The distribution of the Brassolidae is shown to be almost equiva-
lent to that of the Morphidae, as each is wholly tropical. As for
certain other tropical groups, the distribution of this family ranges
upward to 3,000 meters and farther southward than northward.
The Nymphalidae are a large group, with a range equivalent to
that of the Pieridae in both elevation and latitude, but they usually
do not extend so high in the equatorial regions.
The Erycinidae are largely tropical, but extend northward to
50° N. Lat. and southward to 35° S. Lat., and upward to 3,000 meters
in the broad center of the range. This family thus has a range similar
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 325
to that of the Danaidae, Morphidae, and BrassoHdae, except for the
greater north-south distribution.
The Lycaenidae occupy a strangely tropical-appearing range, but
extend to 82° N. and to 40° S. Lat. In the equatorial regions they
range up to 5,000 meters, and from 45° N. to 15° S. they continuously
extend up to 4,000 meters. These ranges must be studied individually
by analyzing their constituents, since some forms in the group are
clearly cold-adapted.
Observation of the charts as a whole shows that members of the
Pieridae, Nymphalidae, and Lycaenidae extend farther to the north
than do any other families. The first two are joined by the Satyridae
in extending to the southern tip of South America. There are, by
the way, no butterflies in Antarctica.
The Lycaenidae equal the Pieridae and the Nymphalidae in
northernmost range, and in southernmost range nearly equal those
families, as well as the Satyridae and the summer migrants of the
Danaiidae. Next in order of northernmost occurrence are the Satyri-
dae and the Papilionidae, each of which nearly reaches to 70° N.
Lat. The Satyridae extend all the way to the tip of South America,
along with the Nymphalidae and the Pieridae, but do not extend so
far north. All the other families have much more restricted north-
south distributional ranges, and should be considered tropical in
their entirety.
The same families that extend far into the north and south lati-
tudes are also found at high elevations in the mountains of the middle
latitudes of North America: the Papilionidae, the Pieridae, the
Satyridae, the Nymphalidae, and the Lycaenidae. Contrary to
expectation, these families are not necessarily the same ones that
are found at the highest elevations in the mountains of the equatorial
belt, here treated and charted as from 20° N. Lat. to 20° S. Lat.
Instead, some of the purely tropical families exceed the northern
ones in elevation in this belt, where they occupy cold zones high in
the mountains. For example, the tropical Danaidae exist up to 4,000
meters in a broad equatorial belt, where the Papilionidae do not
exceed 3,000 meters. Elevations reached by the Papilionidae, the
Satyridae, and the Nymphalidae are considerably higher in the
middle latitudes of North America than in the central equatorial
latitudes.
Of the six families with resident examples in the northern lati-
326 W. HOVANITZ
tudes north of 40° N., only three extend beyond 40° S. South of the
equatorial belt the butterfly fauna is quite depauperate, because of
the relative lack of typically cold-adapted forms of northern origin.
On the other hand, many typically tropical forms are seen to extend
farther southward than northward for reasons that can only be
conjectured but are probably a combination of (1) lack of competi-
tive forms in the far south and (2) warmer winters at the same lati-
tudes south of the equator than to the north.
DISTRIBUTION OF GENERA AND SOME SMALLER GROUPS
Following the chart (Fig. 1) that compares the distributions of the
families of American butterflies, block histograms (Figs. 2-19) are
presented to show the latitudinal and altitudinal distributions of the
genera and of certain lesser groups, when this is deemed desirable.
The histogram for each family is repeated, in finely crosshatched
form, at the head of the series of black histograms for the contained
genera. Within the family divisions coarsely hatched histograms for
the recognized subfamilies head the appropriate series of black
histograms. As a variation in the scheme, below the black histogram
(on Fig. 2) showing the distribution of the first-entered genus,
Papilio, there are given three coarsely hatched histograms, each of
which gives the range of one of the main "groups" into which this
large genus is first divided. Each of the hatched histograms is in
turn followed by black histograms for the contained natural species
groups; and the first of the three main divisions, the Aristolochia
Papilios, is first divided into sections A and B (also shown in black).
Under the papilionid genus Parnassius black histograms portray the
distribution of the three American species. In the Satyriidae, under
the genus Euptychia, black histograms show the ranges of the 27
species groups. Otherwise, the black histograms portray the dis-
tribution of genera.
Papilionidae (Figs. 2-3)
This family is represented by only four genera, of which one
{Papilio) is very large and is subdivided many times. It probably
should be divided into many genera or subgenera, but so far no
other really good natural division has gained acceptance. The
groups as organized by Jordan are satisfactory for our purpose.
The genus Papilio has almost the same distributional range as the
DISTRIBUTION OF BUTTERFLIES IX THE NEW WORLD
327
PA PILIONIDAE
Fig. 2. New World distribution of Papilionidae (1).
328
W. HOVANITZ
< 'J
i^
"V
^^"^yu^y^
eo 70 60 50 40 30 20 10
20 30 40 50
Fig. 3. New World distribution of Papilionidae (2) and Pieridae (1).
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 329
family, being exceeded by the family only in the northern parts of
the range and only by the genus Parnassius. The latitudinal range
is greater in the north than the south, going to 65° N. and to only
35° S. Also, the elevations attained are higher in the north than in
the south: to 4,000 meters at about 35° N. Lat. and to only 1,000
meters at 35° S. Lat.; to 3,000 meters at 10° to 20° N. Lat. but to
only 2,000 meters at 10° to 20° S. Lat. The distribution of the genus
has a northern skew, because, as shall be seen below, some groups of
northern origin are superimposed in the north on groups of tropical
or equatorial origin.
The genus is subdivided into three natural groups, the Aristo-
lochia, the Fluted, and the Kite Papilios. The Aristolochia group,
extending from 42° N. Lat. to 35° S. Lat. has a tropical range, ex-
tending into the non-equatorial regions only where winter tempera-
tures are not too cold and long. Elevations to 2,000 meters are
attained in the equatorial range. Of two sections of the Aristolochia
Papilios, only one, comprising the Polydamus group, extends north
of the equatorial area more than 5°. The other section (A) is tropi-
cal, but extends farther south (35° S.) than north (25° N.). This
section consists of three natural groups {Ascanius, Aeneas, and
Ly Sander), which have about the same range in the equatorial region.
The Fluted Papilios have nearly the same range as the genus
itself, and comprise both northern and tropical members. The
species groups considered here are clearly seen on the chart to be
divisible into two parts, a northern part consisting of the Machaon
and Glaucus groups and an equatorial part consisting of the re-
maining six groups. The Machaon and Glaiccus groups extend to
65° N. Lat. and the Machaon group reaches 3,000-4,000 meters in
elevation in the region of 35-40° N. Lat. Both groups extend into
the equatorial regions at middle elevations (2,000-4,000 meters)
and the Machaon group extends as far as 10° S. Lat. in the Andes.
The Glaucus group does not reach across the barrier presented by the
Panamanian isthmus. Of the tropical groups, only Thoas extends
much north of the Tropic of Cancer and then only to 42° N. Lat.
Except for the Homerus group, the others are strictly equatorial
and tropical, not exceeding 1,000 meters in elevation. The Homerus
group ranges up to 3,000 meters in the equatorial belt.
The equatorial Kite Papilios are represented north of the Tropic
of Cancer only by the Marcellus group. The Lysithiaus and Thyastes
330 W. HOVANITZ
groups extend slightly farther south than north. The Marcellus
group extends to 40° N. and to 30° S., with an apparent gap of
some 25°.
The genera Euryades and Baronia are considered as primitive
members of the Papilionidae. Their distributional ranges are typical
of relict species at the far corners of a once wider range. Euryades
exists in the southeastern part of South America where it has a
latitudinal range of 15° on the plains. It extends to 35° S. Lat.,
which is as far south as is reached by only one group in Papilio.
Baronia is isolated in southern Mexico, where it exists with a range
of less than 5° latitude and of less than 1,000 meters elevation.
Parnassius, the remaining genus in the Papilionidae, is northern
in origin and distribution. It has a range from nearly 70° to 35° N.
Lat. and occurs at elevations from sea level to 5,000 meters. The
three species that comprise the genus in America are indicated
separately: P. thor is restricted to a range of less than 10° latitude
at near sea level in Alaska ; P. smintheiis occurs from sea level in the
north (65° N.) to 5,000 meters in the south (35° N.); P. clodius is
found from sea level in the north (65° N.) to both sea level and 5,000
meters in the south (35° N.) (it accomplishes this dual range in the
south by existing along the cool-summer Pacific Coast as well as in
the cool-summer mountains of the interior).
Pieridae (Figs. 3-5)
This large family covers the entire range of land from north to
south and at nearly all elevations. It is subdivisible into four natural
groups, the Pierinae, the Rhodocerinae, the Euchloinae, and the
Dismorphiinae. Except for the last, each of these is large in itself
and covers almost the same range as the family. The range of the
Pierinae is less than that of the Pieridae only in that it extends in the
far north only to 68° N. Lat. instead of to 82° and reaches lower
elevations in North and South America. The subfamily consists of
several genera, most of which are divisible into types with narrow
temperature tolerance. Neophasia is limited to a range of 30° to
55° N. Lat., and should be considered one of the rare types of
temperate origin. Eucheira is a relict type found only from 20° to
30° N. Lat. at elevations of from 2,000 to 3,000 meters.
Tatochila has an unusual distributional range in that it exists
from 55° S. Lat. to 10° N. Lat., wholly within the continent of South
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
331
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Fig. 4. New World distribution of Pieridae (2).
332
W. HOVANITZ
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EUCHLOINAE
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Fig. 5. New World distribution of Pieridae (3) and Danaidae (1).
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 333
America, from sea level in the south to 3,000-4,000 meters in the
north. It has a counterpart in the north, Pieris, which extends from
68° N. Lat. (at sea level) to 15° N. Lat. (at 2,000-4,000 meters).
The ranges of these two nominal genera are separated by low-
elevation barriers in Central America. There is good reason for
considering them to be congeneric, since the differences between
them are not greater than those between species within each group.
The remaining genera of the Pierinae are all equatorial; only one,
Ascia, ranges north of the Tropic of Cancer. The altitudinal range
of some of the genera is narrow (less than 1 ,000 meters) , of others
wide (up to 4,000 meters). Catasticta ranges from 20° N. Lat. to
20° S. Lat., and at all elevations from sea level to 3,000 meters.
The range of the Rhodocerinae is wider than that of the Pierinae
and is equivalent to that of the Pieridae as a whole. The genera are
divisible again into temperature-tolerance groups as is shown by the
histograms.
Eurema is equatorial; it ranges to 30° N. Lat. and to 25° S. Lat.,
and up to 3,000 meters in the central Andes. Phoebis is equatorial
but extends farther north than Eurema (to 35° N. Lat.,) although it
has a more limited altitudinal distribution. Anteos is also equatorial;
it extends north and south only to 25° and has a limited elevational
distribution (to 2,000 meters). Kricogonia is subtropical with a
range extending only from 10° to 30° N. Lat., at near sea level. This
is unusual in that most species or genera that inhabit the tropics
cover the entire tropical area from the Tropic of Cancer to the Tropic
of Capricorn with little in the way of further limitations.
Colias is low-temperature dependent, as is shown by the histo-
gram. It ranges from 82° N. Lat. to 55° S. Lat., is present across the
equator at high elevations, but is absent in the low elevations in the
tropical regions and exists farther north and at higher elevations
than any other butterfly genus. The altitudinal range in North
America (to 5,000 meters) and in the Andes is as high as any or-
ganism can live. The range is broken by a gap of 5° latitude from
Guatemala to Venezuela and Colombia.
Zerene resembles Colias in pattern of distribution, but usually
lives in warmer regions and at lower elevations. It exists only to 40°
N. Lat. and 30° S. Lat., is absent from lower elevations across the
equatorial regions and inhabits the middle-equatorial altitudes
(1,000-3,000 meters), in a zone intermediate between the hotter
334 W. HOVANITZ
tropics at lower elevations and the cooler regions higher in the
mountains.
Nathalis resembles Kricogonia in having a limited distributional
range from 5° to 35° N. Lat. ; within this range, however, it occupies
a wide altitudinal belt up to 4,000 meters (but typically only to
3,000 meters). It has failed to pass from the North American tropics
into the South American tropics despite the apparent absence of a
barrier.
The Euchloinae comprise six genera the distribution of which, for
such a small group, is especially diverse: two are wholly northern,
three are wholly southern, and one is equatorial with a southern
expansion. Euchloe, a typical northern type, is found as far north as
60° N. Lat. with a sea level extension along the Pacific Coast to
30° N. This pattern is nearly duplicated by that of Anthocharis ,
with the exception that the latter extends farther south, to 25° N.
Lat. at elevations of 3,000-4,000 meters, and thence to 15° at 2,000
to 3,000 meters.
Eroessa duplicates, to a certain extent, these distributions south
of the equator, covering elevations of from 1,000 to 3,000 meters
with a latitudinal range from 25° to 40° S. Lat. Hesperocharis is the
connecting link between the genera of the southern hemisphere and
those of the northern hemisphere. It covers all elevations from sea
level to 3,000 meters, from 20° N. Lat. to 20° S. Lat., and, in addi-
tion, extends southward up to 1,000 meters to 45° S. Lat. It thus
overlaps in distributional range all other genera except Eiichloe.
Andina is represented by a very limited distributional range at
4,000-5,000 meters elevation in the Andes, from 15° to 20° S. Lat.
Phalia extends this range downward to 2,000 meters, over a lati-
tudinal range from 15° to 25° S. Lat. These distributions appear to
indicate that the Euchloinae are a closely knit group with specific
temperature tolerances, with the possibility that the basic origin of
the group was tropical and that its northern {Euchloe, Anthocharis)
and southern (Eroessa, Andina, Phalia) representatives were inde-
pendently derived from the tropical Hesperocharis, or from its
ancestors. Of course it is always possible that the entire American
group was derived from Asiatic representatives, via Euchloe and
Anthocharis, that Hesperocharis was derived from these, and the
southern types from Hesperocharis. The direction of derivation
cannot be deduced from present day distributions alone.
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 335
The Dismorphiinae comprise a small group that may not be
derived from the Pieridae. Its range is wholly tropical, with a slightly
greater extension to the south than to the north of the tropics. Of
the two genera, Dismorphia has the same distribution as the sub-
family and P seudopieris is restricted to a range from 15° N. Lat. to
15° S. Lat.
Danaidae (Figs. 5-7)
The Danaidae comprise thirty-five genera, all but one of which
are restricted, or almost confined, to ranges between the Tropics of
Cancer and Capricorn. The only genus not so restricted is Danais,
one species of which extends its range annually to latitudes of 55° N.
and 55° S. by seasonal migration. In addition, this species manages
to remain at home at latitudes up to 40° N. and 30° S. The distribu-
tional range of the family as a whole forms a pyramidal histogram
with the median point centered at about 10° N. of the equator,
rather than being centrally placed across the tropics. Higher eleva-
tions are inhabited north of the equator than southward, but it is
possible that this apparent phenomenon is due to the lack of suffi-
cient information for the humid region on the east side of the Andes
south of the equator.
The Lycoreinae with two genera are equatorial at low elevations.
The Mechanitinae are also equatorial but extend to 25° S. Lat.
This is a very large subfamily ranging from sea level to 2,000 meters.
All thirty genera are found within this range; some occupy the
whole range, others only a narrow segment. For example, Athesis
occupies a range from 10° N. Lat. to 5° S. Lat. at elevations of only
1,000 to 2,000 meters. Sais is found only from 5° N. Lat. to 0°. No
reasons for the restricted ranges of some of these genera are apparent
from the histograms. A great proportion of genera occupy the area
from 10° or 15° N. Lat. to 10° or 15° S. Lat., although there are no
geographic barriers in these regions to hinder their expansion to 20°
in either direction. The family as a whole should be considered as
one of entirely tropical origin, for no representative lives perma-
nently in cold regions.
Morphidae (Fig. 7)
The Morphidae are represented by one genus (Morpho), which is
entirely equatorial though extending to considerable elevations (up
336
W. HOVANITZ
80 70 60 50 40 30 20 10
10 20 30 40 50
Fig. 6. New World distribution of Danaidae (2).
DISTRIBUTION OK BUTTERFLIES IN THE NEW WORLD
337
E P I S C A A
PTEPONYMIA
M I R A L E R 1 A
VELAwrST/
^ Y P O L E fl I A
P5EUDOSCA0A
D I S M E N I T I S
H Y M E N I T I S
lETEROSAlS
MORPHID AE
M R P M O
SATYRlOAE
80 70 60 50 40 30 20 10
20 30 40 50
Fig. 7. New World distribution of Danaidae (3), Morphidae, and
Satyridae (!)•
338 W. HOVANITZ
to 3,000 meters). As is usual for a number of tropical or equatorial
groups, the range southward (to 28° S. Lat.) is greater than north-
ward. There is no indication of any but a tropical origin for this
group.
Satyridae (Figs. 7-12)
The Satyridae comprise a huge family that extends from the arctic
regions at 70° N. Lat. to 55° S. Lat. They occur at nearly all eleva-
tions throughout this range. Tropical genera, however, are far more
abundant than northern genera. The family is an interesting one
since many genera have highly restricted habitats both within and
outside the tropics.
Callitaera, Haetera, Pierella, and Antirrhaea are confined almost
wholly within the tropical regions; except for Callitaera they range
up to 2,000 meters. Sinarista has a restricted range from 7° N. Lat.
to the equator and from 1,000 to 2,000 meters in elevation (it exists
only in the northern Andes of Colombia and Ecuador) . Coerois and
Tisiphone are equatorial ; the former is the more restricted. Tisiphone
extends southward to 30° S. Lat. and up to 2,500 meters between
the tropics.
Enodia, on the other hand, occupies a north temperate habitat
ranging from 25° to 45° N. Lat. in the eastern part of North America.
Since it has no northern affinities but only tropical ones, it may be
assumed to be of tropical origin.
Taygetis has a full range between the tropics up to 2,000 meters
and extends south to 30° S. Lat. Amphideda, on the other hand, is
restricted to lower elevations south of Panama.
Euptychia is a large genus of certainly tropical origin, but includes
at least four groups that extend northward to 45° N. Lat. and several
that extend southward to 35° S. Lat. The genus is subdivided into
groups in the histograms, to show how some groups are restricted
tropical, some are extensive tropical, and a few are restricted
temperate types. In the first classification (restricted tropical) are
the Nossis, Pronophila, Liturata, Gera, Lea, Tolumnia, and Agaga
groups. In the second classification (extended tropical) are the
Hesiofie, Mollma, Saturnus, Harmonia, Necys, Pacarars, Batesii,
Cephus, and Arnaea groups. In the third category (restricted tem-
perate either north or south) are the Paeon, Cluena, Phocion, and
Pyracmon groups. A fourth set might be recognized, namely, those
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
339
Fig. 8. New World distribution of Satyridae (2).
340
W. HOVANITZ
80
70
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Fig. 9. New World distribution of Satyridae (3).
50
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
341
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Fig. 10. New World distribution of Satyridae (4).
342
W. HOVANITZ
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Fig. 11. New World distribution of Satyridae (5).
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 343
with panequatorial distributions that extend far into the temperate
zones. These are the Ocypete, Renata, and Hermes groups.
The restricted range (15°-20° N. Lat. at 1,000-2,000 meters sug-
gests that the genus Pindus is a relict group similar to Baronia.
Cyllopsis has a similar distribution but extends from 10° to 25° N
Lat. and from 1,000 to v3,000 meters in elevation. Oressinoma ex-
tends from 10° N. Lat. to 20° S. Lat. Paramecera is restricted to the
same general area as Pindus (17° to 25° N. Lat. and 1.000-2.000
meters elevation). It too suggests a relict group.
Satyrodes, Coenonympha, Neominois, Cercyonis, Oeneis, and
Erebia are all northern genera that have no contact with the tropics.
The charts show typical histograms of forms with cold-temperature
tolerances, by increasing in elevation in the south. In distribution
these northern forms are somewhat duplicated south of the equator
by Argyrophorus, Cosmosatyrus, Tetraphlebia, Faunida, Neosatyrus,
Neomaenus, Epinephele, Elina, and Eteona. No other family has
developed so many genera south of the equator. It may be assumed
that they developed from tropical relatives independently of
northern genera.
Many of the genera (perhaps not good ones) have very restricted
distributions in equatorial habitats. Many have very restricted
altitudinal ranges as well; for example:
Manerebia, 15°-20° S. Lat., 2,000-3,000 meters
Indioneura, 5° N. Lat., -0° 2,000-3,000 meters
Pseudomaniola, 15°-20°S. Lat., 3,500-5,000 meters
Calisto, 16°-27.5° N. Lat., 0-2,000 meters
Pseudosteroma, 5° N. Lat. -15° S. Lat., (discontinuously?) 2,000-
3,000 meters
Steremnia, 10° N. Lat. -15° S. Lat., (discontinuously?) 2,000-3,000
meters
Gyrocheilus, 13°-35° N. Lat., 2,000-3,000 meters
Eretris, 10° N. Lat., -5° S. Lat. 2,000-4,000 meters
Daedalma, 10° N. Lat.. -15° S. Lat. 2,000-3,500 meters
Polymastus, 5° N. Lat., -10° S. Lat. 2,500-3,500 meters
The great prevalence of restricted, narrowly ranging genera in the
Andes suggests a center of rapid divergence of these forms in the
area. This may not have been the center of origin of the family, but
almost certainly has been a secondary center of origin for many
genera.
The northern genera of the family have affinities with Asia, and
344 W. HOVANITZ
it is possible that these have had their origin there, and that the
tropical forms of the family have been derived secondarily from
these (or from their ancestors). From existing distributions, it is not
possible to decide in which direction the migrations went. The
systematics of the remaining groups (Figs. 8-12) are too uncertain
to warrant extended discussion.
Brassolidae (Fig. 12)
All nine genera of the Brassolidae are equatorial, although as usual
for distributions of this type the ranges extend farther south (to 30°
S. Lat.) than north (to 20° N. Lat.). The altitudinal range is only to
2,000 meters, except in a restricted part of the range of Caligo. The
origin of the group is to be regarded as tropical since there are no
indications of affinities elsewhere.
Nymphalidae (Figs. 12-16)
This huge family is not exceeded in its diversity by any other,
and it is equaled in its distributional range only by the Pieridae.
Many of the subfamilies are wholly tropical, but others are northern.
Some of the most interesting distributions are found in this family.
The distributional range, as in the Pieridae, is from 82° N. Lat. to
55° S. Lat. and from sea level to 5,000 meters in elevation.
The four subfamilies are not of equal size or character. The three
smaller ones are tropical, or nearly so, and the larger one has the
same distributional range as the family itself. The Acreinae are
represented by only one genus, which has an equatorial range from
20° N. Lat. to 30° S. Lat. and an altitudinal range to 3,000 meters.
Actinote provides no exception to the rule already indicated for
other groups that the ranges of equatorial species often extend
farther south than north.
The Heliconiinae are another equatorial subfamily, larger than the
preceding, with five genera. Three of these extend slightly beyond the
confines of the equatorial belt, one as far as 35° N. Lat. and 35° S.
Lat. Except for Metamorpha these exist as high as 2,000-3,000
meters in elevation. Heliconius, Eulides, Colaenis, and Dione have
the full range from north to south ; the range of Metamorpha ceases
at Panama (10° N. Lat.) as is typical of the range of many southern
genera.
The Clothildinae are represented by one genus, Clothilda, having a
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
345
80 70 60 50 40 30 20
10 20 30 40 50
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80 70 60 50 40 30 20 10
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Fig. 12. New World distribution of Satyridae (6), Brassolidae, and
Nymphalidae (1).
346
W. HOVANITZ
A„„ ,^",nrai,.„ [1n-((i
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Fig. 13. New World distribution of Nymphalidae (2).
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
347
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Fig. 14. New World distribution of Nymphalidae (3),
348
W. HOVANITZ
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Fig. 15. New World distribution of Nymphalidae (4).
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
349
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Fig. 16. New World distribution of Nymphalidae (5) and Erycinidae (1).
350 W. HOVANITZ
narrow range from only 10° to 20° N. Lat. It is absent from South
America.
The Nymphalinae comprise the major part of the family Nympha-
lidae, and are not easily subdivided into further parts. The family
Pieridae can be divided into several large natural subfamilies. On
the other hand, the Nymphalidae can be subdivided only by remov-
ing a few odd forms since no large natural cleavage lines are ap-
parent. In fact, even the line between the Nymphalinae and the
Heliconiinae is poorly defined.
The genera of the Nymphalinae do not fall into definite classes
such as tropical and northern. Instead, each seems to have its
specific range of temperature tolerance. One may be wholly tropical,
another subtropical, and another cold adapted.
Euptoieta is tropically adapted but exists north and south to 3>S°,
and to 3,000 meters in the central equatorial region. Probably all
temperatures short of freezing are satisfactory, as colonies are quite
common at 3,000 meters in the Tierra Fria of the equatorial belt.
Argynnis, on the other hand, is a cold-adapted genus. It exists to
82° N. Lat. and to 55° S. Lat., but it is absent in the equatorial
regions between 25° N. Lat. and 15° S. Lat., even at the higher
elevations. As is typical of northern types, the elevations at which it
survives are higher southward in the northern hemisphere and higher
northward in the southern hemisphere. Argynnis is a large genus
that exists around the world. If is best considered subdivided into
various subgenera. If this were done for the /\merican forms, at
least four subgenera would be recognized for North America and a
fifth for South America. Two of the groups that would be treated as
subgenera in North America extend nearly to the Bering Straits
and are represented in Asia. Thus, there is recent gene continuity
between America and Asia. The third subgenus is separated by a
considerably greater distance and, at least during the quaternary,
has been completely severed from the nearest relatives in Asia.
There has developed in the North American temperate zone a par-
ticular type not represented elsewhere. Likewise, the South Ameri-
can subgenus has been isolated so long that its type is not represented
elsewhere in the world.
The genus Melitaea occupies the temperate part of North America
(also Eurasia) and is not represented south of 20° N. Lat. Phyciodes,
on the other hand, covers somewhat the same territory in the north,
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 351
but it occupies in addition the equatorial zone at 3,000 or 4,000
meters altitude to 20° S. Lat. and extends to 25°.
The genus Chlosyne is equatorial and occupies the lower elevations
(less than 2,000 meters), with extensions to 35° N. Lat. and 25°
S. Lat.
Microtia, Gnathotriche, and Morpheis occupy narrow zones in the
northern part of the equatorial region. Undoubtedly, revision of
these genera would prove desirable and would indicate relationships
better.
Polygonia is a northern type that extends from 68° to 20° N. Lat.
and occurs at higher elevations in the south. Nymphalis {Vanessa)
is slightly less a northern type, extends less far to the north (to
50° N. Lat.), but farther to the south (to 10° N. Lat.). Vanessa
(Pyrameis) is also not such a northern type, having about the same
northern distribution as Nymphalis but extending over the tropics at
2,000-3,000 meters elevation and existing south of the equatorial
regions as well. Representatives of this genus exist throughout the
world in cold or temperate regions. Contact with Eurasia is broken
by a considerable distance across the Bering Straits, but probably
only a little increase of ocean temperatures would be sufficient to
connect them again.
All the remaining genera of this subfamily are equatorial and
seem to owe their origin to America. A few, however, have been able
to survive colder temperatures and are found north or south of the
equatorial zones. Victorina extends to 30° N. Lat. and to 30° S. Lat.
Didonis extends to 30° S. Lat. Cystineura and Megalura ( = Timetes)
extend to 27° N. Lat. and to 25° S. Lat. Myscelia extends to 30 N.
Lat. and to 25° S. Lat. Historis and Pyrrhogyra extend to 25° S. Lat.
A few genera, for example Lucinia, Balboneura, and Peria, have very
restricted ranges. These suggest relict genera. Several genera extend
northward only to Panama (for example, Cybielis, Callithea, Haema-
tera, Panacea, Agris, and Zaretes). Others that extend north or south
of the equatorial zone by 5°-10° are Cybielis, Eunica, Callicore,
Dynamine, Cyclogramma, Adelpha, Ageronia, Chlorippe, Prepona,
and Anaea. Some of these extend only to the north; others only to
the south.
Two of the genera having equatorial affinities, Limenitis ( =Basi-
larchia) and Asterocampa, are found only in the northern temperate
latitudes. Limenitis extends from 15° to 50° N. Lat. and Asterocampa
352 W. HOVANITZ
from 15° to 43° N. Lat. A reconsideration of these genera may indi-
cate that they are not of generic stature; for example, Leminitis is
possibly congeneric with Adelpha.
A number of genera of very restricted ranges in the tropics are
insufficiently known to be able to offer reasons for their restriction.
Judging from distributions alone, some of these, for example Gnatho-
triche, Morpheis, Lucinia, Peria, Balboneura, Libythma, Batesia,
and Coenophlebia, appear to be relict types. However, study of
other relationships is required before differentiations can be made
between those that are newly adapted to a localized habitat and
those that are relicts.
Contrary to the distributional patterns in the Satyridae, few
genera of the Nymphalidae are restricted to intermediate or high
elevations in the equatorial regions, or, on the other hand, to a
wholly Southern Hemisphere distribution.
Erycinidae (Figs. 16-19)
Few genera of the Erycinidae occur outside the equatorial regions,
or nearby. Only two of the genera range far into northern latitudes.
The histogram shows, however, a range from 50° N. Lat. to 35° S.
Lat. and to 3,000 meters in the equatorial and desert mountains.
Most of the equatorial genera extend farther south of the Tropic
of Capricorn than they do north of the Tropic of Cancer. In fact,
in this family 23 of the 28 equatorial genera whose ranges reach the
Tropic of Capricorn extend beyond at least to 30° S. Lat. The
equatorial genera are nearly all adapted to the lowest elevations
(0-1,000 meters), though a few extend upward in the Cordillera to
2,000-3,000 meters. Only one genus is restricted to higher eleva-
tions, namely, Imelda at 1,000-2,500 meters.
The genus Charts has an equatorial range but extends also to 42°
N. Lat. and to 33° S. Lat. Apodemia, on the other hand, is restricted
to the North Temperate zone, from 50° to 20° N. Lat. A Southern
Hemisphere range from 20° to 30° S. Lat. is also indicated, but is a
basis that requires further generic study for certainty.
Lycaenidae (Fig. 19)
The Lycaenidae is a very large family extending from 82° N. Lat.
to 55° S. Lat., and from sea level to 5,000 meters in elevation. Over
much of its range it exists together with the Nymphalidae and
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
353
ns^:--^-^^^
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A L E 5 A ; ]
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Fig. 17. New World distribution of Erycinidae (2).
354
W. HOVANITZ
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Fig. 18. New World distribution of Erycinidae (3).
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD
355
< o
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80 70 60 50 40 30 20
C U U A E U£
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80 70 60 50 40 30 20
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Fig. 19. New World distribution of Erycinidae (4) and Lycaenidae.
356 W. HOVANITZ
Pieridae. The family contains some huge and diverse genera, which
are badly in need of comprehensive study. On the whole, the genera
are northern rather than tropical, such as the genera of the Ery-
cinidae. However, since the largest genera are tropical, it is likely
that the bulk of species exists in the equatorial range.
Eumaeiis has a tropical range extending northward to 30° N. Lat.
and up to 2,000 meters in elevation, but southward only to 15°
S. Lat.
Theorema has a very limited range near sea level from 15° N. Lat.
to 0°. Trichonis is even more restricted, to from 0° to 5° N. Lat.
The largest genus from the standpoint of species, but also the
most difficult to subdivide naturally, is Thecla. This genus has a
tropical core that ranges from tropic to tropic at elevations from
to 4,000 meters (some species even to 5,000 meters). But it also
exists northward in cold areas as far as 60° N. Lat., and at eleva-
tions up to 4,000 meters as far north as 40° N. Lat. In addition, it
extends southward to 55° S. This genus is virtually a family in itself
and probably ought to be considered at least a subfamily.
Theclopsis has a limited equatorial range from 10° N. Lat. to 15°
S. Lat. at elevations not over 1,000 meters. Scolitaritides has a limited
distribution south of the tropics; it ranges from 0° to 40° S. Lat.,
at elevations from 3,000 to 4,000 meters in the equatorial region
and at sea level southward.
Chrysophanus has a strictly northern distribution ; it ranges from
72° to 25° N. Lat., and at high elevations toward the south. This
genus is also Eurasiatic, as might be expected.
Feniseca is restricted to a narrow latitudinal range from 35° to
45° N. Lat. at lower elevations. Few genera of any family are so
restricted to the North American temperate zone.
Leptotes is equatorial, extending from tropic to tropic at 0-2,000
meters, but extending also northward to 40° N. Lat.
Brephidiiim is North American tropical and temperate, extending
from 10° to 45° N. Lat. at all elevations from to 2,000 meters. Few
butterfly genera have such a restricted North and Central American
range.
Hemiargiis lives at elevations from to 3,000 meters and extends
slightly farther north (to 30°) than south (to 25°).
Hylos is found only in the cold temperatures of the Andes from
2° N. Lat. to 20° S. Lat. and occurs at elevations between 3,000
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 357
and 5,000 meters. In this zone of endemism it is accompanied by
some Pieridae, Nymphalidae, and Satyridae.
Everes along with Leptotes has a tropical core but exists also north-
ward to 50° N. Lat. and southward to 25° S. Lat.
Plebejus, Philoles, and Glaucopsyche are North Temperate genera.
Plebejus ranges from 82° to 15° N. Lat., at higher elevations south-
ward, especially at about 40° N. Lat. Philotes is restricted to the
range 25° to 40° N. Lat. Glaucopsyche has a similar range but goes
to 50° N. Lat. Plebejus and Glaucopsyche are also Eurasiatic.
Lycaeniopsis exists at low elevations from 10° to 65° N. Lat., but
at the higher elevations of 2,000-3,000 meters only in the central
part of its range.
CHARACTERISTIC DISTRIBUTIONAL PATTERNS
The generic and family distributional charts have indicated a
number of recurring and characteristic distributional patterns.
The distribution of the families of butterflies (Fig. 1) can be
divided into two kinds: (1) the tropical distribution (or nearly so)
and (2) the non-specific or general distribution. These are as follows:
(1) (2)
Tropical General
Danaidae Papilionidae
Morphidae Pieridae
Brassolidae Satyridae
Erycinidae Nymphalidae
Lycaenidae
The genera of the second grouping can be classified according to
the nature of their distribution. Two major classifications are
readily apparent. These are the strictly equatorial genera ranging
generally between the Tropics of Cancer and Capricorn, or at most
only a little north or south. Examples of this type of distribution are
those of CatasHcta and Appias (Fig. 4). Few genera of this classifi-
cation are found in Eurasia or Africa.
The second major distributional pattern is that of the northern
types, which extend to far northern latitudes and typically occur at
increasing elevation to the south. Most of these genera live also in
Eurasia or Africa. Included in this group are a few genera that occur
also across the equator at high levels and in southern latitudes.
358 W. HOVANITZ
An enumeration of the genera (including "groups") of these two
types for each family shows :
(1)
(2)
(3)
(4)
Panequatorial
Northern
Other
Total
Papilionidae
Pieridae
14
18
3
5
2
7
19
30
Danaidae
15
19
34
Morphidae
Satyridae
Brassolidae
1
18
4
7
60
4
1
85
8
Nymphalidae
Erycinidae
38
29
7
1
25
19
70
49
Lycaenidae
5
5
5
15
Total
142
28
141
311
Many genera of the northern distributional pattern have close
relatives, or even continuity of species, in Eurasia, or, if they do not
at present, did in the immediate past when the northern latitudes
were warmer. Except when particular circumstantial evidence pro-
vides a measure of plausibility, there seems to be no sound basis for
inferring that any given form of this type originated in the Old
World or the New.
It can be seen from the figures above that no family has more
genera of northern distributional pattern than of panequatorial
pattern. If numbers alone were important, this would seem to
indicate that all families were, or could be, tropical in origin. Only
three families completely lack genera classed as of the northern type.
Except for the Morphidae, containing the one well-known Neo-
tropical genus Morpho, all the families contain genera that do not
appear referable to either the panequatorial or the northern cate-
gory. In four families, more than half the genera are regarded as of
other types. The Papilionidae, however, have but 2 such genera out
of 19 genera or groups (Figs. 2-3). These are Euryades and Baronia
(Fig. 3), both of which are clearly relict types of restricted distribu-
tion.
The Pieridae (Figs. 3-5) have 7 such types out of a total of 30
genera. One of these, Eucheira, is similar to Baronia in range, for it
is restricted to a narrow elevated range near the Tropic of Cancer
Tatochila complements Pieris in the southern hemisphere and
probably should be considered at most a subgenus. Two of these
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 359
seven genera display a common equatorial distributional pattern in
which the distribution would be panequatorial were it not that the
northern range stops at 10° N. Lat., that is, at the Isthmus of Pan-
ama. Since these are usually well-adapted tropical types existing at
low elevation, there is no discernible reason for this abrupt termina-
tion except for the few that cannot cross the Andes from the eastern
to the western tropical regions in Colombia or Venezuela. The two
pierid genera of this category are Leucidia and Leodonta (Fig. 4).
Complementary distributions from 10° N. Lat. northward are less
common. These are in effect circum-Caribbean types, which are
represented in the Pieridae by Kricogonia and Nathalis (Fig. 4), the
latter of which reaches as far south as 5° N. Lat. In the Eiichloinae
three genera, Eroessa, Andina, and Phalia (Fig. 5), are restricted to
southern latitudes at high elevations.
In the Danaidae (Figs. 5-7), 19 out of a total of 34 genera fit into
neither the northern nor the panequatorial pattern. Since all these
are tropical, the reason for their restricted range is not immediately
apparent. Ten of the 19 reach their northern limit at 10° N. Lat.,
but most of these also do not extend far southward. The other 9 are
limited to belts of varying degrees of latitude in the vicinity of the
equator. This would seem to indicate that temperature is not the
limiting factor in their distribution.
In the Satyridae (Figs. 7-12), fully 60 of the 85 genera have ranges
that do not fit into the two major categories. The Panamanian limit
(10° N. Lat.) characterizes only 18 of the genera. The others are
limited in various ways. The most common limitation in this family
is restricted altitudinal range for a short latitudinal distance in the
equatorial Andes. This family is rich in genera of limited distribu-
tion in the Andes and in the Central American Cordillera. Included
are genera of very small range at almost every latitudinal belt from
30° to 40° N. Lat. to 30° to 40° S. Lat. In fact, this family has more
genera than any other, and most of them are limited in range. No
other family has so many genera (fully 14) restricted to a south
latitudinal distributional range or so many (22) restricted to a range
of less than 10° of latitude.
In the Brassolidae (Fig. 12), of the four genera not included in the
panequatorial distributional pattern, two cease their northern range
at the Panamanian 10° N. Lat. limit, and two are restricted to a
narrow (10°) range south of the Tropic of Capricorn.
360 W. HOVANITZ
In the Nymphalidae (Fig. 12-16), 25 of the 70 included genera are
neither fully panequatorial (38) nor northern (7). The Panamanian
10° N. Lat. limit disqualifies only 3 genera, Metamorpha, Cybielus,
and Agrias, from the panequatorial category. Others having narrow
distribution are Gnathotriche, Lucinia, Peria, Balboneura, Libythinia,
Batesia, Morpheis, and Caenophlebia with 5° limits; Vila and Poly-
grapha with 10° limits; Napeodes and Megistanis with 15° limits;
Haematera, Panacea, Callithea, and Zaretes with 20° limits. Clothilda
like Kricogonia, has a pan-Caribbean distribution (10°-20° N. Lat.).
In the Erycinidae (Figs. 16-19), 19 of the included 49 genera are
neither panequatorial (29) nor northern (1). Ten of the 19 are limited
in the north by the Panamanian 10° N. Lat. barrier, even though all
exist at the lowest altitudinal ranges. The others are tropical but
limited in latitudinal distribution, usually at the lowest altitudinal
levels.
The 15 lycaenid genera (F'ig. 19) are equally divided into the
three major groups. None seems to be affected particularly by the
Panamanian 10° N. Lat. barrier. One of the 5 has a 25° equatorial
range, another 15°, one 10° in the temperate zone of the north, one
at the higher levels of the southern Andes, and one (Brephidium) in
the tropics and temperate zones north of 10° N. Lat.
Altogether 45 genera out of the total of 311 have a distributional
range that is equatorial save for the 10° N. Lat. limits. This number
exceeds the combined total (28) of northern genera. Nearly one-
third (96) of the total genera have ranges that do not fit into the
normal patterns, largely because the ranges are too limited. Only 4
genera, Kricogonia, Nathalis, Clothilda, and Brephidium, are both
tropical and restricted latitudinally north of South America (pan-
Caribbean). Some genera are restricted to less than 5° latitude,
mostly in the mountain belt between 30° N. Lat. and 30° S. Lat.
Exceptional areas of endemism of this sort are: (1) the Mexican
mountains, especially in the south, (2) the higher parts of the Andes,
especially in Peru and Bolivia, and (3) the plains of South America
from 20° to 35° S. Lat.
SIGNIFICANT FACTORS
Butterflies are directly temperature-controlled (i.e., cold-blooded).
The larvae are plant feeders. The adults are day fliers, mostly
dependent on direct solar radiation for flight. These three factors
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD vS61
appear to be the most significant in controlling the distribution of
butterflies.
Because they are dependent on the heat of the environment for
their activity, butterflies become inactive at temperatures below
freezing. The tropical environment therefore appears to be ideal.
This is reflected by the facts that 262 of the 311 genera (and species
groups) are equatorial and that 142 of these occupy the whole, or
almost the whole, distance from the Tropic of Cancer to the Tropic
of Capricorn. Adaptation to existence in northern or southern
latitudes with seasonal cold weather has been attained by members
of 7 out of 9 of the families in one of two ways: (1) by remaining
during the cold time of the year in an inactive state (diapause), or
(2) by migrating out of the area. The former method has been em-
ployed most successfully by members of 6 families, which thereby
are enabled to exist in areas of freezing winters. The members of the
seventh family (Danaidae), without diapause, avoid the hazard
of cold by migrating into warmer regions each winter. In fact, it is
not unusual for many species of several families to migrate south-
ward in winter and northward in summer, especially in areas on the
fringes of their ranges.
Most species appear to have a limited range of temperature toler-
ance. This is obviously narrower for species than for genera, but
even for most genera it appears from the charted distribution to be
narrower. Genera adapted for cold climates seem to be unable to
exist in areas of continuous high temperatures. Their ranges typically
rise in altitude as they progress southward in the northern latitudes,
or northward in the southern latitudes. Even the distribution of
genera appears to be partly controlled by temperature tolerances. For
example, Colias is cold-adapted and skips over the tropics and sub-
tropics, whereas Zerene is adapted to subtropical conditions and
remains below the cold regions (altitudinally and latitudinally) and
above the hot temperatures (Fig. 4). Other genera occupy the hot
areas. The species within a genus occupy belts of latitudinal diversi-
fication. The species of Colias can be arranged in consecutive order
from those most cold-adapted to those most warm-adapted. The
most warm-adapted species {Colias enry theme) lacks a diapause and
depends for its survival in the winter either on migration or on
resistance to the relatively short winters in the temperate zone. It
cannot survive in the far north. It migrates northward in the Mis-
362 W. HOVANITZ
sissippi Valley in summer and southward in winter. The species
Danais plexippus does so also throughout the whole of its temperate
zone range.
Nearly all plant-eating insects develop a high degree of specificity
in their food habits. One species or race of insect is commonly re-
stricted to one species or group of plants. Such restrictions naturally
limit the geographical ranges of the insects to the range of the nec-
essary plants. These restrictions of temperature or habitat further
narrow insects to but a portion of that range. The limited ranges of
many tropical genera, indicated before, are undoubtedly related to
the distribution of food plants.
With few exceptions, all butterflies depend on direct solar radia-
tion for activity. The few exceptions are certain genera of the Brasso-
lidae Danainae, and Ithomiinae, which fly in the partial shade of the
tropical forest. A close relationship exists between temperature and
solar radiation, with regard to the tolerances of certain butterflies.
These tolerances are controlled even to groups as small as the color
phases of a single species. For example, the white and orange color
phases of Colias eury theme have been shown to respond differentially
to these two environmental factors, which operate in combination
(higher temperatures partly compensate for lower solar radiation
and vice versa).
Areas with little or no direct solar radiation, especially where the
temperatures are low, do not support butterfly populations. This is
true in the Aleutian Islands, Iceland, and southwest Chile.
CHANGING DISTRIBUTIONS
Distributional maps, or the histograms here shown, give an undue
impression of permanence. The distributions change in time: over
many years (as with climatic changes), over one year (annually),
during part of one year (seasonally), or even daily.
There is much circumstantial evidence for distributional changes
in past time. Restriction of colonies of northern species in southern
mountains with no recent contact suggests a once wider range with
continuity during a colder period. For example, the population of
Colias philodice in Guatemala is separated now from its nearest
relatives by the whole of Mexico; the population of Colias interior
in the southern Appalachians is separated now from the nearest
northern stock in the White Mountains of New Hampshire; Colias
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 363
behri is located in the southern Sierra Nevada from its presently
nearest relative in central Oregon. Many other examples of such
disjunction could be cited.
Tropical forms occasionally invade more northern areas, where
they may stay for a season or two. Extremes of climates are usually
the limiting factors controlling distributions, but they do not always
occur annually. Thus colonies can often survive out of their more
permanent range for several years until an unusual year wipes them
out. Colias eurytheme periodically invades the colder regions of
northern Canada where it may survive for a number of generations.
Then a cold winter kills all individuals. Phoebis periodically invades
northern areas during the summer and may even survive mild
winters.
Ice age distributions may or may not have been very different
from what they are now, but great areas were undoubtedly denuded
of all populations by the glaciers. Such areas are still being repopu-
lated. Some of the reinvasions from opposite sides of the former
continental glacier of North America have led to interesting read-
justments of species relationships. Colias hecla and Colias nastes, for
example, hybridize in that area to form a third species, not found
elsewhere. There is often a narrow line of demarcation between two
species, one that existed south and east of the glacier, and one that
held out in the unglaciated area to the northwest. For example, in
Limenitis, the two species astyanax (south) and arthemis (north) now
narrowly overlap in the Great Lakes area. Similarly, Colias interior
(south) and Colias palaeno (north) narrowly overlap across central
Canada.
Colias eurytheme is absent from the Gulf Coast of the eastern
United States in summer, since the temperatures there are unsatis-
factory for its existence. However, it is reestablished by migrants
from the north in autumn, and passes through two or three genera-
tions before the hot summers arrive again. In the meantime, cold
winter weather forces the adults to disappear for a month or two.
Daily differences in activity and distribution have been indicated
for the genetically determined color phases of Colias. It is of course
the selective effect of climate on individuals that determines in a
broader sense the distribution of species, of genera, and of families.
The groups are no more important than the individuals of which
they are composed.
364 W. HOVANITZ
ORIGINS
Genetically speaking, the point of origin of any species, genus, or
family can be any location inhabited by the genetically aberrant
individual ancestor. Origins can ordinarily be determined only by
circumstantial evidence and thus are no more certain than the evi-
dence used. Inferences on the origin of any group depend on the
distributional pattern of the group, particularly on its isolation, and
on the number of forms that have remained isolated in a particular
area.
It has been seen that for the American butterflies an Old World
origin can plausibly be postulated for all those types having a
northern range, as they all have affinities in Eurasia. However, it
could be proposed with similar plausibility that these forms origi-
nated in North America and dispersed into Eurasia. Moreover,
since all these northern types also have affinities in the American
tropics, it is possible that they originated in the tropics or at least
from the tropical forms. It seems probable that the tropical forms as
we know them have originated in the American tropics. The degree
of differentiation of the New World butterfly fauna from the faunas
of Eurasia and the African-Australian region increases progressively
in proportion to the distance from Bering Straits. This suggests long
and great isolation of the American tropical fauna from the faunas
of the Old World tropics. Such continuity as exists is only through
the few northern types.
Primary origins, whether of the northern or the tropical groups of
butterflies, can seldom be securely determined, or even plausibly
suggested. Secondary origins or centers for butterfly types, however,
are indicated for various regions, including the zones of endemism
already discussed. In the North American temperate region there
has been an extensive development of characteristic subgenera in
such genera as Colias, Argynnis, Melitaea, Oeneis, Satyrus, Pieris,
Limenitis, Plebejiis, and Glaucopsyche. Colias and Argynnis give
evidence of other secondary origins in the temperate zones of South
America. The tremendous development of satyrid genera in the
Andes is unique, as is the development of a number of genera in
several families on the Altiplano of Peru and Bolivia. The Caribbean
region shows relatively little endemism, but four genera are re-
stricted thereto.
By analogy and by theory it seems plausible to postulate that
DISTRIBUTION OF BUTTERFLIES IN THE NEW WORLD 365
centers of origin for many species and genera of butterflies have
often been places where invading species have encountered many
new, unoccupied habitats, for, it is generally assumed, adaptive
speciation is rapid and extensive in such places. Such a process has
probably led to the evolution of the endemic genera of Satyridae in
the Andes, during the relatively recent grand uplift of the Cordillera.
A similar basis may be inferred for the development in northern
regions of new species of Colias, Argynnis, and other genera that
probably invaded the disturbed lands of North America, some in
relatively recent time. Such centers of origin are areas where diverse
genetic types on new arrival have found readily available habitats
for their occupancy. The trial and error system of natural selection
probably succeeds best under such conditions.
BIBLIOGRAPHY
Below is a partial compilation of the literature that has provided a
large part of the data for the present digest. Nearly every paper published
on American butterflies is important in providing geographical or ecologi-
cal information. A bibliography such as this cannot, however, list every
paper seen or read. The author's observations have also been essential in
providing accuracy on the altitudinal and geographical distributions in
Alaska, the Northwest Territories, the Yukon Territory, Alberta, and
British Columbia, the Sierra Nevada, the Rocky Mountains, Mexico,
Central America, Colombia, and Ecuador. Without these observations, it
would probable have been impossible to have constructed the histograms.
Accuracy in the Mexican region is due in large part to the data of Hoff-
mann. The region poorest known is that of the central to southern Andes,
in Peru, Bolivia, Argentina, and Chile. Data obtained from collections
should also be mentioned, even though many of these do not give alti-
tudinal details.
Barnes, William, and J. J. McDunnough. 1911-1922. Contributions to the
Natural History of the Lepidoptera of North America, Vols. 1-5.
Decatur, 111.
Bates, Marston. 1935. The butterflies of Cuba. Bull. Museum Comp. Zool.
Harvard. 78: 61-258.
Bowman, Kenneth. 1919. Annotated Check List of the Macrolepidoptera of
Alberta. Alberta Natural History Society, Red Deer, Alberta. With
revisions 1919, 1920, 1921, 1924, 1928, 1934, 1938, 1944.
Breyer, Alberto. 1936. Lepidopteros de la Zona del Lago Nahuel Huapi
Territorio del Rio Negro. Rev. soc. entom. arg., 8: 61-63.
. 1939. Uber die Argentinischen Pieriden. VII Intern. Kongr.
Entom., Berlin, 1938: 26-55.
366 W. HOVANITZ
Brooks, G. Shirley. 1942. A check list of the butterflies of Manitoba.
Can. Entomologist, 74: 31-36.
Brown, F. Martin. 1941-43 (continued series). Notes on Ecuadorian
butterflies. Various journals.
. 1943-45 (continued). Notes on Mexican butterflies. I-V.
. 1950. The American Papilios. Lep. Neivs, 4: 39-42; 63-67.
. 1953. The Papilios of Ecuador. Rev. Ecuatoriana Entomol. y
Parasitol., 1: 41-60.
Carpenter, G. D. Hale, and C. B. Lewis. 1943. A collection of Lepidoptera
from the Cayman Islands. Ann. Carnegie Museum, 29: 371-396.
Clark, Austin H. 1932. The butterflies of the District of Columbia and
vicinity. Smithsonian Institution, U. S. Natl. Museum Bull. 157.
Comstock, John A 1928. Butterflies of California. Los Angeles.
Comstock, Wm. P. 1944. Insects of Puerto Rico and the Virgin Islands:
Rhopalocera or butterflies. N. Y. Acad. Sci., 12, Pt. 4: 419-622.
Davenport, Demorest. 1941. The butterflies of the satyrid genus Coeno-
nympha. Bull. Museum Comp. Zool. Harvard, 87: 215-349.
Dillon, Lawrence S. 1948. The tribe Catogrammini. Part 1. The genus
Catogramma and allies. Reading Museum Sci. Pubis. No. 8.
Dyar, Harrison G. 1904. The Lepidoptera of the Kootenai District of
British Columbia. Proc. U. S. Natl. Museum, 27: 779-938.
. 1914. Report on the Lepidoptera of the Smithsonian Biological
Survey of the Panama Canal Zone. Proc. U. S. Natl. Mus., 47: 139-
350.
Edwards, William H. 1868-1897. The Butterflies of North America. Boston
and New York.
Elrod, Morton J. 1906. The butterflies of Montana. Univ. Montana Bull.
30, Biol. Ser. 10.
Elwes, H. J. 1898. A revision of the genus Erebia. Trans. Entomol. Soc.
London, 1898: 169-207.
Field, Wifliam D. 1938. A manual of the butterflies and skippers of
Kansas. Bull. Univ. Kansas, 39 (12): 1-328.
Fiske, W. F. 1901. Butterflies of New Hampshire. New Hampshire Col-
lege Agr. Expt. Sta. Tech. Bull. No. 1.
Forbes, William T. M. 1945. The genus Phyciodes. Entomol. Americana,
24: 139-207.
Fox, Richard M. 1940. A generic review of the Ithomiinae. Trans. Am.
Entomol. Soc, 66: 161-207.
. 1947. Ithomiinae of Rancho Grande, Venezuela. Zool., 32: 173-
178.
Garth, John S. 1935. Butterflies of Yosemite National Park. Bull. South-
ern Calif. Acad. Sci., 34: 1-39.
. 1950. Butterflies of Grand Canyon National Park. Grand Canyon,
Ariz. Nat. Hist. Assoc, Bull. 11.
Gay, H. 1849. Fauna Chilena. Santiago de Chile.
DISTRIBUTION OK BUTTERFLIES IN THE NEW WORLD 367
Gibson, Arthur. 1920. Report of the Canadian Arctic Expedition 1913-18,
Vol. 3, Insects: Pt. 1, Lepidoptera. Ottawa, Canada.
Godman, Frederick D., and Osbert Salvin. 1879-1901. Biologia Centrali-
Americana. Insecta-Lepidoptera-Rhopalocera. Vols. 1, 2, 3.
. 1891. in Whymper's Travels among the Great Andes of the Equator,
Appendix, Lepidoptera, Rhopalocera.
Grinnell, Joseph, and F. Grinnell, Jr. 1907. Butterflies of the San Ber-
nardino Mountains, California. /. TV. Y. Entolol. Soc, 15: 37-50.
Grossbeck, John A. 1917. Insects of Florida. IV. Lepidoptera. Bull. Am.
Museum Nat. Hist., 37: 1-147.
Hayward, Kenneth J. 1931. Los Nymphalidoes Argentinos. Rev. Soc.
entomol. arg, 4 (1-3): 1-199.
Hoffmann, Carlos C. 1940. Catalogo Sistematico Zoogeografico de los
Lepidopteros Mexicanos. Primera Parte. Papilionidea. Anales inst.
hiol. {Univ. nac. Mex.), 11 (2): 639-739.
Hovanitz, William. 1945. Comparisons of .some Andean butterfly faunas.
Caldasia, 3: 301-36.
— ■. 1941. Parallel ecogenotypical color variations in butterflies.
Ecology, 22: 259-284.
. 1943. Geographical variation and racial structure of Argynnis
callippe in California. Am. Naturalist, 77: 400-425.
— . 1945. Distribution of Colias in the Equatorial Andes. Caldasia, 3:
283-300.
1950. The biology of Colias butterflies. Wasmann J. Biol., 8:
49-75.
Jorgensen, Pedro. 1916. Las Mariposas Argentinos familia Pieridae. Ann.
Mus. Hist. Nat., Buenos Aires, 28: 427-520.
Kaye, William J. 1904. Catalogue of the Lepidoptera Rhopalocera of
Trinidad. Trans. Entomol. Soc. London, 1904: 159-228.
— . 1914. Butterflies of Trinidad, Pt. 1. Agricultural Society, Trinidad
and Tobago, Port-of-Spain, Trinidad.
1921. A catalogue of the Trinidad Lepidoptera Rhopalocera.
Mem. Dept. Agr., Trinidad and Tobago.
Leighton, Ben. V. 1946. The butterflies of Washington. Univ. Wash.
Pubis. Biol, 9: 47-63.
Longstaff, G. B. 1914. Butterflies of Tobago: On some butterflies of
Tobago. Reprinted from Trans. Entomol. Soc. London, 1908.
McAlpine, W. S. 1918. A collection of Lepidoptera from Whitefish Point,
Michigan. Occ. Papers Museum Zool. Univ. Mich. No. 54.
Macy, Ralph W., and Harold H. Shepard. 1941. Butterflies (esp. Min-
nesota). University Minnesota Press, Minneapolis, Minn.
Reed, Edwyn C. 1877. Monografia de las Mariposas Chilenos. Anales
Univ. Santiago, 1766: 647-736.
Rothschild, Walter, and Karl Jordan. 1906. A revision of the American
Papilios. Novitates Zoologicae, 13: 411-745.
368 W. HOVANITZ
Ureta, Emilio. 1936-37. Lepidopteros de Chile. Rev. Chilena Hist. Nat.
Schudder, Samuel H. 1889. The Butterflies of the Eastern United States and
Canada. Cambridge.
Seitz, Adalbert. 1924. Macrolepidoptera of the World. Various authors. The
American Phopalocera, Vol. 5, Stuttgart.
Warren, B. C. S. 1936. Monograph of the genus Erebia. British Museum,
London.
. 1944. Review of the classification of the Argynnidi, etc. Trans.
Roy. Entomol. Soc. London, 94: 1-53.
Wright, William G. 1906. Butterflies of the West Coast of the United States.
San Bernardino, Calif.
PAMT II
Geographic Distribution of
Contemporary Organisms
Introduction
E. Raymond Hall
The University of Kansas, Lawrence
W hen a biologist accurately depicts the geo-
graphic distribution of species of contemporary organisms, he does,
in a sense, about what the merchant does when he completes an
inventory of his stock of goods. When the biologist maps also the
geographic distribution of these same kinds, and also other kinds, of
organisms of the immediately preceding geological epoch, he does,
in a sense, what the merchant does when he examines his inventory
list of a year ago. Paleontology for the biologist and history of stocks
of goods for the merchant better than almost any other information
permit the biologist and merchant, respectively, to forecast what lies
ahead.
For the biologist who studies evolution and its modus operandi,
speciation is of major importance because "species" means "kinds,"
and the biologist has to distinguish one kind of organism from all
others before he can plot the distribution of any one kind. Further-
more, the biologist must, on the one hand, decide on a subjective
basis whether a particular morphological ensemble is a species or a
genus and, on the other hand, on an objective basis whether that
ensemble is a species or a subspecies. In order to decide on species
versus subspecies much field work, especially collecting at the right
places and times, is required. If the two kinds intergrade in nature,
they are subspecies of a single species. If the two kinds do not any-
where in nature intergrade, they are two species.
Therefore, the nontaxonomist should remember when he views a
reasonably accurate map of the geographic distribution of an or-
ganism that the map represents several steps along the road to an
understanding of how evolution occurred in nature.
From what the speakers showed and told and from what was
said in the ensuing discussion, I judge that (1) several problems have
been solved, but that the solution of a particular problem ordinarily
371
372 E. R. HALL
poses new unsolved problems; (2) the geographic distributions of
many kinds of organisms in the temperate region of North America
are explained by Quaternary climates — climates of the immediate
past geologically speaking; and (3) shifts of geographic range now in
progress are primarily northward.
On the second point, it seems that the alternation of dry and moist
periods in the central part of what is now the United States left their
marks on contemporary organisms. These alternations of climate
are thought to have been associated with recessions and extensions
of glaciers in the northern part of North America. There is reason
to suppose that each of several mammalian stocks now separated
into two species (eastern and western) formerly ranged as one species
across the United States from the Atlantic to the Pacific. For ex-
ample, the Eastern Cottontail of the eastern region that supports
shrubs and trees and Nuttall's Cottontail of the western region that
supports shrubs and trees probably owe their existence as separate
species to a period of aridity, south of the glacial front, so marked
that the common stock withdrew from most of the region that we
now designate as the Great Plains. In the now still arid Great Plains,
albeit less arid than at some times in the past, the two stocks have
reinvaded the region but only by following the few ribbonlike
riparian plant associations that extend from west to east across the
grassy plains. Where the two stocks of cottontails now meet, they
do not intergrade (crossbreed), having evolved, while separated from
each other, along different physiological and physical lines. The
Shrews of the Sorex vagrans group recently reported on by Dr. James
S. Findley {Univ. Kansas PubL, Mus. Nat. Hist., 9: 1-68, 18 figures,
December 10, 1955) provide a second example of the effect of a
period of aridity, in this instance in the Great Basin of the western
part of the United States. While the two stocks of Sorex vagrans —
east and west — were separated, evolution did not proceed quite so
far as in the Cottontails and so the two stocks of shrews crossbreed
at a few of the places where their geographic ranges ultimately met
again. At other places they do not crossbreed. Indeed the geographic
ranges broadly overlap and provide one of the few examples in
mammals of two subspecies of the same species occurring together
over a considerable geographic region.
Incidentally, it seems to me, that the effectiveness of the grass-
lands of the Great Plains, extending from Mexico to Canada, in
INTRODUCTIOX 373
isolating closely related stocks of land vertebrates from each other
has seldom been recognized by zoogeographers and certainly has
not been carefully assessed.
In illustration of the third point I again draw on the Mammalia.
Shifts of geographic range now in progress are evident in the Nine-
banded Armadillo, in the Hispid Cotton Rat, and seemingly in the
Southern Bog Lemming. The northern margin of the geographic
range of the Bog Lemming seems to have shifted northward in the
past 30 years in the eastern part of the Great Plains. In the same
region in the past 40 years the Armadillo has extended the northern
margin of its range 75 miles and in the same region and period of time
the Cotton Rat has done the same thing by moving approximately
200 miles.
Pleistocene Ecology and Biogeography of
North America'
Paul S. Martin
Geochronology Laboratories,
University of Arizona, Tuscan
Uuring the past ten years, the related fields of
Pleistocene chronology, biogeography, palynology, and prehistory
have experienced vigorous growth. This growth may be attributed in
part to methods of isotope dating, fresh interest in periglacial
geomorphology, the application of pollen stratigraphy to archaeo-
logical and chronological problems, and increased appreciation of
"vertebrate microfossils." Students of animal and plant distribution
find themselves increasingly committed to archaeological and
geological data. The information exchange is mutual and poses a
challenge in interdisciplinary communication. For attempting to
unify Pleistocene concepts within archaeological, biological, geologi-
cal, and climatological specialities we are especially indebted to
Braun (1955), Clark (1952), Deevey (1949, 1953), Flint (1957),
Frenzel and Troll (1952), and Moreau (1955). In North America
Dillon's mapping of Pleistocene life zones (1956) has filled something
of a vacuum in the area of biogeographic reconstruction.
My present purpose is to identify some of the problems that
appear important in the terrestrial ecology and biogeography of
North America during the late Pleistocene. This project follows the
logical principle advocated by Deevey (1949) that students of
plant and animal distributions are obligated to consider the Pleisto-
cene before working backward. To do so does not mean ignoring or
neglecting the instructive record of Tertiary environment and life.
The adopted course, however, is based on the belief that Pleistocene
climatic change was not confined to the glacial border. Until
proved otherwise, the more useful working hypothesis is that
' Contribution No. 9 of the Program in Geochronology, University of Arizona.
375
376 P. S. MARTIN
existing range gaps and relict populations date from the Glacial
period. From the viewpoint of the biologist the foremost events in
terrestrial ecology of North America during the Pleistocene appear
to include the following: (1) the climatic sequence proper with its
attendant displacement of biotic zones; (2) the arrival of prehistoric
man; (3) the extinction of late Pleistocene vertebrates. To an un-
unknown degree these events appear interrelated. The first part of
my analysis is devoted to problems of climatic and environmental
change, the second to extinction and the effect of man.
LATE PLEISTOCENE ENVIRONMENT
In view of the relatively poor pre-Wisconsin fossil and sedimen-
tary record, it is expedient to concentrate on the last (Wisconsin)
glacial sequence. Environmental change during the Wisconsin
glaciation can be considered subequal to that which accompanied the
earlier (Nebraskan, Kansan, lUinoian) glaciations. This assumption
is based on the coincidence of the four glacial drift borders in eastern
North America, the four equivalent periods of glacial temperature
drop as recorded in oxygen-isotope analyses of marine foraminifera
from the equatorial Atlantic (Emiliani, 1955), and the apparent
sequence of cool and warm mammalian faunas found in unglaciated
North America (Hibbard, 1958).
Generally, biogeographers keep abreast of modern findings in
glacial geology and are not deterred by such views as that of Scharff
(1912, p. 156) that glacial drift was formed by marine deposition
and that the climate of the Pleistocene was never colder than at
present. Admittedly, there is lack of agreement concerning Pleisto-
cene environment and life in the region where glacial geology pro-
vides least information, namely in the temperate and tropical zones
south of the drift border. Braun (1951, p. 145) felt that "... the
deciduous forest zone, although narrowed, maintained itself on the
Appalachian Plateaus in southern Ohio and Kentucky while glaciers
extended southward in Ohio." Thomas (1951, p. 166) followed suit:
"The distribution and the ecology of many Ohio animals, I believe,
raises strong presumption that they survived the Wisconsin, or
perhaps the entire Pleistocene, close to the glacial border; some
species in refugia within the limits of glaciated territory." Plants in
question include buckeye (Aesculus octandra), sweet gum {Liqui-
dambar), Agave, and Magnolia. Animals with distributions that also
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 377
parallel the Wisconsin drift border in Ohio include the fence lizard
{Sceloporus undulatus), copperhead {Agkistrodon contortrix), and
upland chorus frog {P seiidacris brachy phono). To date there is no
sound paleontological support for the postulated ice margin popula-
tions of temperate biotas.
On the contrary, evidence of Pleistocene spruce in southern
Louisiana and spruce and fir pollen in northern Florida and eastern
Texas seems impeccable (cf. Deevey, 1949; Braun, 1955). The
interpretation of the evidence, however, is not immediately shown.
Does it prove the existence of boreal forest at this latitude? Or does
it reflect an azonal mixture of temperate and boreal floras through-
out the unglaciated east as Braun (1955) and Drury (1956) main-
tained? Presently spruce grows near sea level in Connecticut and
southern Michigan, 400 to 500 miles beyond the southern limit of
spruce-fir-jack pine boreal forest. The Florida and Texas records of
boreal elements may also represent marginal populations of species
whose position of dominance lay farther north. We need not insist
that fossil spruce meant boreal forest in Texas and Louisiana, but it
may well represent population outliers of boreal forest occupying
Kentucky and the Carolinas.
An area of intense frost action extending 50 to 100 miles south
of the ice sheet is generally accepted by geologists (Flint, 1957),
at least for eastern North America. Denny's studies (1951, 1956) of
periglacial land forms in unglaciated Pennsylvania are relatively
conservative, Peltier's (1949) more sweeping in their paleoclimatic
conclusions. Quite recently a series of herb-dominated pollen zones
have been reported from inorganic sediments in eastern North
America (Andersen, 1954; Davis, 1957; Deevey, 1951; Leopold,
1956; Livingstone and Livingstone, 1958; Martin 1958a). I consider
these findings as palynological confirmation of Full- and Late-glacial
tundra zones.
At this point it may be helpful to insert a definition. Within the
scope of the term tundra I would include the following: (1) treeless
vegetation in the Arctic; (2) treeless Alpine zones on temperate and
tropical mountains; (3) pollen zones in Pleistocene sediments featur-
ing high percentages of herb pollen plus a small amount of spruce
and other boreal tree pollen.
There is no question of floristic identity between these communi-
ties. As an example. Ambrosia, an element in the Late-glacial pollen
378 p. S. MARTIN
zones of New England and Michigan, is not found in the Arctic.
Both Ambrosia and Ephedra, another steppe species in the Late-
glacial of Europe and America, present the problem of how we might
distinguish cool prairie from tundra in a pollen diagram. Today these
vegetation types are separated by a belt of woodland and forest.
Is it possible that they were in contact during the glacial periods?
Perhaps the periglacial landscape was not entirely treeless. If
scattered spruce, larch, or jack pine grew near the ice margin, they
would have formed a taiga or boreal savanna. Presently the taiga
lies between boreal forest and treeless tundra (Rousseau, 1952 ; Hare,
1954). Occasionally pieces of coniferous wood are found in glacial
drift (Flint, 1957, p. 323). Rather than indicating that forest was
overridden by ice, they may mean that the glacier swept through a
taiga type woodland, a more plausible ice-margin environment. The
relatively well-known and widely discussed Two Creeks "forest"
bed, silted and covered by Valders ice (Wilson, 1932, 1936) is not an
exception. In stump diameter, taper, and growth rate the Two
Creeks trees resemble spruce woodland in central Ungava (see
Hustich, 1954, for comparative data). In brief, fossil wood is not
proof of forest !
We may expect that Full-glacial tundra, boreal forest, and
deciduous forest formations were not identical in species composition
or even in vegetational structure with their present bioclimatic
analogues. Nevertheless, if there is an adaptive relationship between
vegetation and climatic zones, it seems unreasonable to postulate an
azonal system during the glacial period, as Drury has done (1956,
pp. 80-90). The model proposed by Dansereau (1957), with nar-
rowed tundra bordering the ice at one point and maple or oak forest
at others, also does not agree with either the concept of bioclimatic
gradients or with Late-glacial pollen diagrams. In general the suc-
cession of pollen zones, tundra -^ boreal forest — » deciduous forest
in New England and boreal forest — > mixed deciduous forest -^ oak-
pine forest in North Carolina (Frey, 1953)^ shows, I believe, the
2 My interpretation of boreal forest in North Carolina is based on Frey's pollen zone
M2 in Singletary Lake and Jones Lake J-1. This reveals dominance of pine, including
many small grains, with up to 9% spruce, 7% oak, 1% birch, and 1% hickory. In fair-
ness to Frey (1953, 1955) it should be noted that, although he regarded his results as
evidence of climatic change, he does not advance the hypothesis of Boreal Forest in the
Carolinas. The case I would make for Boreal Forest rests chiefly on the small but crucial
percentage of spruce and the scarcity or absence of broad-leaved species.
Another authority on this region, D. R. Whitehead (personal correspondence) takes
strong exception to such an interpretation of Frey's work, noting: (1) Size-frequency
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 379
historical integrity of generalized vegetation zones. On this convic-
tion I have attempted to map late Pleistocene vegetation zones in
two periods (Figs. 2 and 3). They are based on pollen stratigraphy,
periglacial geomorphology and scattered plant and animal fossil
records. Presumably, such a map will be of more value to the bio-
geographer than one based largely on biogeographic evidence that
leads to a circular argument. If boreal forest replaced temperate
deciduous forest in the Cumberland Plateau and southern Appala-
chians, it seems preferable to attempt to establish this fact in terms
of pollen analysis, buried soils, and other fossil evidence.
Modern Vegetation Zones (Fig. 1)
Dansereau (1951) has stressed the importance of structure to the
geographer and general ecologist, a viewpoint that I believe to be
profitable also in paleoecology. Reconstruction of forest community
composition from pollen data is beset with difficulties, for example in
evaluating relative pollen rain among different wind-pollinated
species and correcting for underrepresentation of insect-pollinated
plants. However, it seems possible to determine structure of the
simplest type, to distinguish forest, savanna, and grassland biochores
and, within the first, coniferous and deciduous formations (for
definitions of these and other vegetational concepts, see Dansereau,
1957). The six major vegetation zones or formations in eastern North
America include: (1) treeless tundra; (2) boreal woodland or taiga,
a savanna formation of needle-leaved trees scattered in a shrub and
lichen mat; (3) boreal forest with a continuous canopy dominated
by needle-leaved evergreens; (4) temperate forest dominated by
broad-leaved deciduous trees and shrubs; (5) temperate prairie and
savanna; (6) subtropical savanna of evergreen sclerophylls and tall
grasses. These six zones represent arbitrary divisions of an adaptive
gradient controlled in general, if not always in detail, by climate. Is
it unreasonable to assume that this gradient maintained its struc-
tural features and sequence during the glacial periods?
features have not been worked out carefully for all the species of pine which are, or
might be, expected in this area. Thus the allocation of small grains to the boreal species
P. bankesiana is premature. (2) Zone M2 from Frey's core LS-2 contains fairly high
percentages of oak (about 15%) and hickory (about 10%) as well as some pollen of
Taxodium, Nyssa, and other temperate elements. (3) The predominance of pine might
be the result of "over-representation" of a species such as P. serolina, which surrounds
boggy sites in the southeast today. In other words, oak, hickory, and associated tem-
perate plants occurred at sites some distance from the bay lakes but were "swamped-
out" by the well-known heavy rain of pine pollen.
380
p. S. MARTIN
Fig. 1. Vegetation zones of eastern North America. Small, isolated
mountain-top populations of boreal forest in parts of the Appalachians
are not shown. The southeastern pine forests are considered part of the
deciduous forest formation in a broad sense. Taiga is mapped on the
basis of its savanna-like structure; floristically it is not very different
from boreal forest. P = prairie.
Full-Glacial (Fig. 2)
Of utmost importance to the student of animal and plant distri-
butions is the extent of Full-glacial biotic displacement. Following
Flint we may date this period as ending roughly 17,000 years ago.
In New Mexico the San Augustin Plains, 7,000 feet in elevation,
were occupied by forest with a spruce pollen frequency of 20%
(Clisby and Sears, 1956). In Postglacial time the spruce has dis-
appeared and non-arboreal species have become more important.
In eastern North America there are only two radiocarbon-dated
pollen diagrams that may represent pollen sedimentation of the
Full-glacial period. From a piedmont marsh in unglaciated Pennsyl-
vania the peak in non-arboreal pollen lies 80 cm below a radiocarbon
date of 13,500 B. P. (Martin, 1958a). Apparently the formation of
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 381
Pennsylvania piedmont swale marshes 50 miles beyond the ice
margin dates from the Full-glacial period and coincides with a
tundra-taiga vegetation of grasses, sedges, other non-arboreal
species, and scattered spruce and jack pine.
A longer late Pleistocene pollen sequence, perhaps extending
back into the middle Pleistocene, has been found in the Carolina Bay
lakes (Frey, 1951, 1953, 1955). Possibly rebedding and truncation
have occurred (Wells and Boyce, 1953; Frey, 1955). If the upper 10
feet of Frey's sequence is continuous, his zones Ml, M2, and MS
should correspond to the Full-glacial period. In these pollen zones
oak and other deciduous trees are scarce or absent; pine predomi-
nates with a high frequency of small-sized grains suggesting Pinus
banksiana. There is a low but constant frequency of spruce. In terms
of structure, the M zones indicate boreal, needle-leaved forest, with
dominance of jack pine attributable to its well-known preference
for sandy situations.
The local records of spruce pollen in Texas, Florida, and Louisiana
are undated and, except for Potzger and Tharp's work (1947, 1954),
unaccompanied by detailed stratigraphic study. If maximum dis-
placement is represented, the difference between Full-glacial and
present southern limits of marginal spruce populations would seem
to be the same as the corresponding past and present southern limits
of the boreal forest formation, that is, 800 miles.
Some type of mixed deciduous forest occupied the extreme south,
with subtropical vegetation largely driven from Florida. Further
discussion of Florida awaits expansion of the pollen studies begun
by Wilson (Davis, 1946).
Certain periglacial land forms including boulder fields, colluvial
soil mantles, and various types of patterned ground constitute rea-
sonably secure evidence of climatic change. Others, such as loess,
are apparently less reliable indicators of ice-margin conditions
(Hack, 1953; Dylik, 1954). Uncritical identification of all "peri-
glacial" features with a Full- or Late-glacial tundra climate is to be
avoided. A few of these features can form at midlatitudes today.
Yehle (1954) described soil tongues similar to periglacial frost cracks
appearing in calcareous soils under the present climate. Goodlett
(1954) reported patterned ground in miniature appearing on bare
earth in central Pennsylvania. Recent colluvial creep and earthflows
382 p. S. MARTIN
in the unglaciated Appalachian Plateaus "... appear to be most
common in pastures, but field and woodland areas are not entirely
free from such movements" (Sharpe and Dosch, 1942).
Wolfe's description (1953) of frost-thaw basins and related peri-
glacial features in unglaciated New Jersey has been subjected to
certain criticism. Yehle (1954) questioned the authenticity of the
alleged frost cracks. Rasmussen (1953) and Deevey (1957) noted
that basins of rather similar appearance occur in the Carolinas and
coastal Texas, beyond the limit of possible periglacial frost action.
However, the involutions and ventifacts which Wolfe described
would appear to remain sound evidence of a periglacial tundra
climate.
Farther south, in the latitude of Washington, D.C., Hack (1955)
and Nikiforoff (1955) found little geomorphological indication of a
"periglacial climate," beyond stabilized dunes and a soil hard pan of
uncertain origin. For this reason, I have included this area within
the Boreal Forest (Fig. 3).
In the Appalachians the block fields or stone streams (Flint, 1957)
and glades including "bear wallows" may mark the lower limit of
Full-glacial alpine tundra (Braun, 1955; Martin, 1958a). Cranberry
Glades in West Virginia at 3,350 feet (Darlington, 1943) is perhaps
the best known of the anomalous glade bogs; Core (1949) discussed
others. In the Smoky Mountains inactive block fields covered with
mosses and ferns and occasional yellow birch trees extend down to
at least 4,500 feet. Braun (1955, p. 361) believed that they indicate a
vertical tree line depression of 2,000 feet. It seems the present
regional tree line does not lie at the top of the peaks as Braun im-
plies. Spruce and fir grow as forest at 6,500 feet, the top of the
Smokies (Whittaker, 1956). I would allow an additional 2,000 feet
for subalpine taiga and "krumholtz" and locate the theoretical
present alpine zone at 8,500 feet. This would bring the relative
depression of the Alpine Zone in eastern North America into line
with that observed at the same latitude in the west, 4,000 to 4,500
feet (Antevs, 1954). In either case the distribution of glade bogs and
inactive block fields reveals that a Full-glacial treeless zone extended
down into the Great Smokies.
To the south of the region of a periglacial treeless zone we might
expect buried organic soils, fossilized "string bogs," or organic ter-
rain of the type that typifies subarctic taiga and boreal forest (Drury,
PLEISTOCEXE ECOLOGY AND BIOGEOGRAPHY
38J
1956). Drury (pp. 86-87) believed that fossil peat and muck deposits
resembling those of Alaska are absent from the unglaciated east. It
would appear, however, that serious search for ancient boreal forest
landforms has not been made in the latitude formerly occupied by
this vegetation type (Fig. 2). The famous buried soil of Spartans-
burg, South Carolina (Cain, 1944), might possibly represent such a
BOREAL FORES T ^f^fii^ 2 p
.'DECIDUOUS FOREST
FULL-GLACIAL
18,000 B.P.
POLLEN PROFILES
1. Marsh, Po.
2. Slngletory Lake, N,C.
Fig. 2. Vegetation zones during the Full-glacial of the late Wisconsin.
Tundra and taiga are mapped as a single zone with no attempt to dis-
tinguish them. Shelf exposure following sea level depression permitted
some extension of vegetation beyond the present coast line.
feature, lying at the southern margin of the Full-glacial boreal forest.
In addition to some hickory and oak these soils contain high per-
centages of spruce, jack pine, and fir pollen. ^
Vertebrate fossils may provide some independent support to the
existence of a narrow Full-glacial tundra zone. While uncritical ac-
ceptance of large mammals as climatic indicators is to be avoided,
' D. R. Whitehead (personal correspondence) is presently analyzing pollen from these
soils and thinks that they are more likely Interglacial than Full-glacial. He reports
finding less spruce and fir than Cain (1944) encountered.
384 P. S. MARTIN
the fossil distribution of Ovibos (see map of Kitts, 1953) fits the Full-
glacial tundra zone fairly well. The barren ground caribou, Rangifer
arcticus, is reported from late Pleistocene deposits and its Full-
glacial range should be roughly similar to that of Ovibos. Apparently
the Postglacial distribution of these species has been so modified by
both prehistoric and modern man that their value as tundra indi-
cators is uncertain.
Rather than in eastern North America, the main Full-glacial
refugia for tundra mammals and birds (Rand, 1948) lay in ungla-
ciated Alaska. The tundra lemmings, Dicrostonyx and Lemmus, have
not been found as fossils south of the ice sheet. The present range of
the Peary Caribou, Rangifer ardicus pearyi, in northern Greenland
and Ellesmere Land dramatizes the ability of caribou to survive at
high latitudes under existing glacial conditions. It is barely possible
that cyclonic nourishment of the Laurentian ice sheet in central
Canada was accompanied by very low precipitation and sufficient
ablation to expose the northern part of Greenland and the Arctic
Islands. Mercer (1956) indicates ice of uncertain depth, but evidently
not very thick, on Baffin Island in the glacial period. The evidence
that Banks Island was largely unglaciated (Manning, 1956) adds
support to the concept of local, restricted glacial activity in the
Arctic during the Full-glacial of the Wisconsin, and of earlier periods.
The poverty of mammalian biotypes in the tundra of north-
eastern Canada compared with northwestern Canada and Alaska is
noteworthy. Tundra species of the northwest include Sorex timdren-
sis, Citellus undulatus parryi, Clethrionomys ruHlus, Microtus
oeconomicus, and M. micrus. These lack vicariants in eastern Canada.
A faunal parallel to Hulten's Beringia rejiigium for the Arctic flora
seems obvious.
Late-Glacial (Fig. 3)
It is sobering to recall that pollen evidence of a North American
tundra dates back no farther than Deevey's study of Aroostook
County in northern Aiaine (1951). Since then, Livingstone and
Livingstone (1958) have confirmed Deevey's tentative recognition
of an Allerod type sequence and, by a radiocarbon date of basal
organic material, have shown that it was indeed contemporaneous
with the Lower Dryas-Allerod-Upper Dryas period in Europe. The
subsequent history of Late-glacial tundra, presumably moving
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY
385
rapidly into central Canada during the Post-glacial period, remains
a mystery.
Although they document changes in forest composition, Potzger
and Courtemanche's Quebec profiles (1956) fail to throw much light
on this problem. How was the glaciated portion of the Arctic re-
Fig. 3. Vegetation zones during the Valders readvance. Tundra and
taiga are not distinguished; the tundra may have been absent west of the
Appalachians. Gillis Lake, Nova Scotia, within the tundra-taiga zone at
this time (Livingstone and Livingstone, 1958), is not shown. Horizontal
ruling marks Lake Agassiz and the proglacial Great Lakes. East of Michi-
gan the position of the Valders drift border is uncertain. P = prairie.
populated? For the present it may be wise to avoid the issue, noting
simply that it is unnecessary to assume a direct continuity of tundra
from mid-latitudes to high latitudes. If the last ice to stagnate and
melt was the Laurentian sheet, it may have "trapped" the retreating
Late-glacial tundra in southern Quebec during deglaciation of
northern Quebec, and permitted tundra plants to invade north-
eastern Canada from the partly unglaciated Arctic Archipelago.
In eastern L^^nited States the Late-glacial, from 17,000 to 10,200
386 p. S. MARTIN
B.P., represented a period of stagnation and retreat, with several
climatic reversals and readvances of ice. Pollen records are still
scattered, and dated diagrams are not as abundant as we might
wish. However, they begin to approach in detail those available for
Postglacial time. The stratigraphic break between the Postglacial
and Late-glacial, which generally marks a rise in organic sedimenta-
tion, is a convenient level for a radiocarbon date. Partly for this
reason, I have found it possible to assemble sufficient dated pollen
horizons to attempt a vegetation map for the end of the Late-glacial
during the Valders readvance. Even though ice returned to central
Michigan, considerable climatic improvement is indicated over the
Full-glacial conditions. In northern New England Deevey's dis-
covery of Valders tundra is confirmed by Livingstone (see Table I).
C^^ dating of pollen zone A-4 in Connecticut indicates the presence
of boreal forest rather than taiga or tundra. The Valders readvance
did not affect radically the forests of southern New England.
Mixed hardwoods and conifers, including spruce, occupied Glade
Bog (2,700 feet) in Tennessee (Johnson, personal correspondence).
Pine-spruce-birch-hemlock dominated the Cranberry Glades of West
Virginia (3,400 feet). Alpine tundra had retreated or perhaps en-
tirely disappeared from the southern Appalachians. Small ice fields,
almost certainly surrounded by tundra, excavated circs in the
Catskills, Adirondacks, and other high mountains of New England
(Manley, 1955). Perhaps of greatest interest is the evidence from
pollen studies that mixed deciduous forest had replaced the pine-
spruce forest of the Carolina Coastal Plain (Frey, 1953). The Valders
forests of that area supported mesophytes such as beech and hem-
lock, temperate species no longer part of the regional pollen rain.
West of the Appalachians the situation is less clear. Andersen
(1954) considered a typical Late-glacial profile from the George
Reserve in southern Michigan to be of Younger Dryas age (Valders
as currently understood in North America). However, if the C^^ dates
from the George Reserve (M-223, M-224, each 11,450±600 B.P.)
are from the same core as was used in Andersen's study, his NAP
zone is older. Possibly it represents the Older Dryas (Port Huron)
period. Andersen presented a thoughtful and skilled analysis of the
problem of "rebedded" and "redeposited" pollen in Late-glacial
sediments and made a strong case for allochthonous origin of such
temperate genera as oak, sweet gum, and ash. The regional pollen
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY
587
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388 P. S. MARTIN
rain represented in the George Reserve clay is predominantly of
spruce, various sedges, and grasses. With an NAP pollen sum not
exceeding 40%, it appears that the vegetation may have been a taiga
rather than a treeless tundra. For my immediate purpose, which is
to map vegetation zones during the Valders maximum, it seems best
to withold judgment on the age equivalent of Andersen's profile. It
does tell us that there was a taiga-tundra period during deglaciation
of Michigan.
Pollen studies of Potzger (Zumberge and Potzger, 1956) reveal
Postglacial events in the Michigan basin and interrelate shifts in
vegetation with changes in lake levels. Potzger failed to encounter
any indication of tundra or taiga conditions during the period that
he felt should have represented the Valders readvance. In this re-
gard his results agree with those of Davis, Leopold, and others in
southern New England. Unfortunately, confidence in Potzger's
sequence is considerably undermined by his consistent failure to
recognize such pollen zones in any of his numerous studies through-
out eastern North America. His rock-flour samples from the inor-
ganic sediments underlying lake gyttja from Hartford Bog indicated
no appreciable NAP pollen sum. Elsewhere in both Europe and
America inorganic sediments of Late-glacial age generally mark
zones of abundant herb pollen, such as Andersen encountered at the
George Reserve. LInless Potzger's results are confirmed, I assume
that the rock-flour levels in Hartford Bog record a tundra ortaiga
phase in the vegetational history of southern Michigan.
The inconclusive results of both Andersen and Potzger provide
poor material for attempting to locate formation boundaries during
the Valders readvance. In extending the zone of taiga-tundra on Fig.
3 south through southern Michigan I have assumed that the pro-
glacial Great Lakes reenforced the periglacial climatic influence of
the Valder's ice sheet producing a poor environment for growth of
forest. This judgment may be only slightly less arbitrary than my
location of the boundaries of boreal forest and temperate deciduous
forest in this region. West of the Appalachians there is no paleo-
ecological record definitely of Valders age to assist in locating these
zones.
Postglacial
Beyond refinements in chronology and mounting evidence of a
very close correspondence between climatic events in the New and
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 389
Old World (Deevey and Flint, 1957), little has been added to the
Postglacial pollen sequence summarized by Deevey in 1949. The
Hypsithermal, also known as Thermal Maximum, Xerothermic,
Altithermal, etc., extended with intermittent pulsations from 9,500
to 2,000 years ago (Deevey and Flint, 1957). It is the most important
climatic event of the period. Documentation of the classic Midwest
Prairie Peninsula extension continues with Smith's recent valuable
analysis of terrestrial vertebrates (1957). In addition to mapping
relict outposts of prairie animals. Smith showed that it is possible
to interpret anomalous and otherwise confusing splits in subspecific
populations in terms of post-Xerothermic isolation. Instructive
examples are found in Agkistrodon contortrix (copperhead), Natrix
erythrogasler (copper-bellied water snake), Diadophis punctatus, and
Opheodrys vernalis. In a bold and original interpretation Smith
explained the history of the Pseudacris nigrita (chorus frog) complex
in terms of invasion of P. n. feriarum, the eastern, forest-inhabiting
race, by P. n. triseriata, a grasslands form from the west. Post-
Xerothermic isolation left a segment of P. n. triseriata, recently de-
scribed as P. n. kalmi, in New Jersey and the Delmarva Peninsula.
Thus on both sides of the Appalachians separate, isolated, popula-
tions of triseriata type chorus frogs integrate wnth feriarum.
Postglacial pollen diagrams indicate Thermal Maximum (C-2
pollen zone) shifts in species composition, with an increase in oak
and hickory in southern New England and, locally, of hemlock in
northern New England. In many diagrams a recovery of spruce
follows in C-3. During the Thermal Maximum Whittaker (1956, p.
60) believed that spruce and fir were pinched off the tops of certain
mountains in the Smokies. Displacement upward of 1,000 feet or
more is indicated by absence of these trees in presumably suitable
sites on peaks of less than 5,500 feet elevation.
Thermal Maximum changes, which command attention of the
student of community composition, the evolutionist, and the bio-
geographer, were inappreciable in terms of the plant formations
mapped in Fig. 1. They do not justify an attempt at a separate
vegetation map.
Western United States, Mexico, and the Tropics
Exclusion from Figs. 1-3 does not imply that these areas escaped
considerable late Pleistocene climatic and environmental change.
For the present, however, it seems impossible to express this effec-
390 p. S. MARTIN
tively on a Pleistocene vegetation map, unless one relies largely on
biogeographic data as Dillon (1956) has done. Topographic com-
plexity inevitably leads to considerable difficulties in large-scale
mapping of vegetation. Twelve major units on Leopold's very use-
ful vegetation map of Mexico (1950) suggest something of the
problem.
Paleobotanical study of the Willow Creek flora of Santa Cruz
Island, California, revealed a latitudinal shift in Pseiidotsuga,
Cupressus, and Pinus of perhaps 440 miles, less than the 800 miles of
zonal displacement in eastern North America (Chancy and Mason,
1934). Studies of late Pleistocene fossil birds indicate an even less
drastic shift. "The avifaunas of the Carpinteria asphalt and of some
of the Pleistocene caves of northern and central California (Miller,
1937, 1939) indicate that the boreal avifauna extended 200 miles
farther south along the coast, at least, and 1,000 feet lower on the
interior mountains. Possibly even more extreme extensions occurred
in other parts of the Pleistocene" (Miller, 1951, p. 610). The latter
comment is crucial; either the Carpinteria and other Pleistocene
cave faunas are not of Full-glacial age or the avifaunal displacement
is discordant with that represented by the Willow-Creek flora.
Actually, neither deposit may represent maximum displacement of
the coldest period.
The same logic can be directed toward the Rancholabrean biota of
the famous tar pits. While the living representatives of this assem-
blage typify environments subequal to those found today in the Los
Angeles basin (summary in Schultz, 1938), the spectacular finds of
extinct animals stamp the assemblage as late Pleistocene. In the
absence of C" dating or other absolute age estimate, it is futile to
urge any bioclimatic theory relating the Rancholabrean biota to
Pleistocene chronology. However, one suspects that certain bio-
geographers have assumed that the fauna is of Full-glacial age and
that it proves lack of climatic change at this latitude. Assumptions
about the cause of large-mammal extinction in this biota, as in
others, may be intertwined with climatic inference. In view of the
results of isotope dating of similar late Pleistocene faunas, it seems
we may anticipate an age postdating the Wisconsin maximum for the
Rancholabrean fauna.
Except for Clisby and Sears' work in New Mexico, late Pleisto-
cene pollen studies have been confined to the Pacific Northwest and
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 391
Alaska (Hansen, 1947, 1953; Heusser, 1953, 1955). They have de-
veloped a sequence that parallels the Postglacial pollen zones of
eastern North America. Hansen (1947) found a rise in grass-
chenopod-composite pollen in south central Oregon in the Thermal
Maximum. Apparently, grassland habitats replaced forest along the
prairie-woodland border. Elsewhere in the west, archaeological cave
sites and pluvial lake beds of the Great Basin promise much to the
pollen analyst. Radiocarbon dating of lake sediments may be the
most profitable means of correlating pluvial and glacial events, and
radiocarbon dates of Searles Lake in southern California confirm a
direct relationship between Great Basin pluvial lakes and the classic
Wisconsin sequence (Flint, 1957, p. 232). To the ornithologist this
should signify abundant and highly productive aquatic environ-
ments at a time when glacial ice covered most of the present breed-
ing grounds of waterfowl and scolopacid shore birds. ,
An original analysis was made by Antevs (1954) of zonal dis-
placement in New Mexico during the Wisconsin. Snowline depres-
sion, the hydrography of pluvial Lake Estancia, and the former
distribution of Marmota indicate a lowering of life zones in New
Mexico on the order of 4,000 to 4,500 feet. The yellow-bellied
marmot is reported from Basket-maker burials at 7,000 feet in
northeastern Arizona (Lange, 1956). This, and its distribution in
grassland of Utah at 4,500 feet, make it a less reliable Pleistocene
thermometer than Antevs (1954), Stearns (1942), and Murray
(1957) have assumed. Nevertheless, the vertical displacement of
snowline and, apparently, of treeline (Martin, 1958b) seems to
require a major shift in montane vegetation gradients.
Spruce (Picea) should be an ideal indicator of temperature change
in the Southwest and should afford some biological control on the
geological evidence of climatic change. Clisby and Sears' pollen
study of the San Augustin plains (1956) indicated Full-glacial spread
of spruce through central New Mexico at 7,000 feet, with a maxi-
mum frequency of 40%, sometime before 27,000 B.P. During the
Pleistocene, almost certainly in the Wisconsin, spruce reached the
Valley of Mexico (Sears et al., 1955). To enter the Mexican Plateau,
spruce, and any associated boreal animals and plants, had to descend
to lower elevation. The lowest point on the Continental Divide be-
tween the Rockies and the Sierra Madre lies at about 4,500 feet in
southern New Mexico. In the adjacent Chiricahua Mountains spruce
392 P. S. MARTIN
is found today in narrow, northerly ravines at 8,500 feet. These
outposts are in extremely favorable microhabitats, and vertical
displacement from a sheltered north slope at 8,500 feet to a level
site at 4,500 feet would require climatic change of greater magnitude
than the temperature depression encountered between these points
(average lapse rate of 0.6° C per 100 meters or a total drop of 7.2° C.)
Mysteriously, spruce disappeared south of Chihuahua, Mexico,
in Postglacial time. Subalpine conifers immediately below treeline at
10,000 to 12,000 feet in the transverse volcanic belt of the Mexican
Plateau include Pinus hartwegii, Abies, and Cupressus. Superficially,
these boreal montane forests appear quite suitable for Picea, and
more than one biologist has referred to them casually as "spruce-
fir."
The best record on climatic change in Mexico comes from the
sedimentary studies of Sears et al. (1955) and Hutchinson et al.
(1956). They demonstrate important climatic fluctuations. How-
ever, the correlation of moist climatic intervals in Mexico with
Cordilleran glacial advances (i.e., Flint, 1957, p. 233) is considerably
less secure than Glacio-pluvial correlations in western North Amer-
ica. Biogeographical evidence and climatological theory raise the
possibility that Postglacial pluvial periods in the Mexican Plateau
are negatively correlated with minor glacial advances at high latitudes
(Martin and Harrell, 1957). In the Thermal Maximum there is no
sound evidence of drought in the Plateau.
The presence of Pleistocene spruce in the Valley of Mexico, the
biogeography of relict montane plant formations such as Cloud
Forest (see below), glacial circ depression on A/Iexican volcanoes
(White, 1956), Chirripo in Costa Rica (Weyl, 1955), and other
tropical mountains above 13,000 feet makes it convenient to infer
climatic cooling at low latitudes during the glacial period. The
presence of an extensive North American ice sheet would, however,
eliminate the present high-pressure system which brings summer
cyclones to Mexico and the Southwest (J. E. McDonald, personal
communication) and one wonders if winter Pacific storms would be
shifted sufficiently to produce truly pluvial conditions in the Valley
of Mexico in the Full-glacial period. Sears et al. (1955, p. 525) inter-
preted their Mexican diagrams as climatic oscillations of moist-warm
and dry-uncertain, the latter representing the Wisconsin glaciation.
Within Mexico and Central America some of the strongest indi-
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 393
cations of climatic change are found in plant-animal distribution in
fragmented and isolated habitats such as the Cloud Forest. Griscom
(1932, 1950) noted rather remarkable uniformity from northern
South America to Mexico in bird life of the Subtropical Life Zone,
which includes Cloud Forest. This habitat generally appears on
windward slopes between 3,000 and 7,000 feet elevation. To account
for the faunal uniformity Griscom (1932) postulated Pleistocene
continuity of the Subtropical Zone, the result of its depression to
sea level. It displaced the lowland tropical fauna which withdrew
southward.
Stuart (1951, p. 32) noted that the present range of montane
lizards and other temperate animals on either side of the Isthmus of
Tehuan tepee (e.g., Barisia and Sceloporus malachiticiis) indicated a
past cool corridor across the arid lowlands. But Stuart questioned
the displacement of lowland Tropical Rainforest, which Griscom
(1950, p. 358) located far south of its present limit in the period of
extreme Pleistocene glaciation. "... a descent to sea level of a sub-
tropical zone would have brought about either widespread exter-
mination of the tropical fauna or acclimatization of that fauna to
subtropical conditions. . . . The evidence, therefore, points to the
presence of a [lowland] tropical environment in northern Central
America even at the height of Pleistocene glaciation" (Stuart, 1951,
p. 29). It seems we must have the argument both ways, altitudinal
depression of subtropical conditions to achieve some continuity of
Cloud Forest through Middle America from Mexico to Colombia,
but with persistence as far north as Mexico of Arid-Tropical scrub
and Tropical Rainforest. Actually, 3,000 feet may be too rigid a lower
altitudinal limit for marginal populations of Cloud Forest species.
Under extremely humid conditions subtropical animals may descend
to 2,000 or 1,000 feet (Wetmore, 1943, p. 223).
The nature of Cloud Forest vegetation, avifauna, and biogeog-
raphy in tropical America is under study by B. E. Harrell (1951).
Marshall's exemplary analysis (1957) of Mexican oak-pine wood land
also illustrates the biogeographic advantage of studying environ-
mental rather than political units.
A brief summary of environmental changes in western North
America and Central America during the late Pleistocene would
include the following points: (1) direct correlation between glacial
conditions in the Cordilleras and the growth of pluvial lakes in the
394 p. S. MARTIN
Great Basin; (2) coincidence of the Thermal Maximum in eastern
and western North America; (3) very doubtful correlation of Glacio-
pluvial conditions in the subtropical latitudes and a negative correla-
tion, controlled by summer cyclones, in Post-glacial time; (4) 4,000
to 4,500 feet displacement of biotic zones in the Southwest during
the Full-glacial period ; (5) displacement of tropical zones by perhaps
3,000 feet in the Pleistocene, exact time unknown, but possibly
during the Glacial maximum.
EARLY MAN IN THE NEW WORLD
The foregoing cursory analysis of late Pleistocene environments
is intended to clear the ground for a brief review of two events that
stand foremost in Pleistocene ecology and paleontology. The im-
portance of these events to students of modern biogeography is not
immediately obvious and is often ignored. However, both the ar-
rival of prehistoric man and the extinction of late Pleistocene ani-
mals pose major biogeographic, as well as paleontological, problems.
Man's arrival in the New World is a matter of continuing con-
troversy. Fluted points, once associated mainly with early man in
western North America, are appearing in many parts of the east.
They confirm much older evidence of early man, evidence dis-
counted during the Hrdlicka period of skepticism regarding Pleisto-
cene man in the New World. The Schoop site in Pennsylvania
(Witthoft, 1952), the Quad site in Alabama (Soday, 1954), fluted
points in Michigan (Quimby, 1958), in North Carolina, and an
apparent Late-glacial flint industry in the Manitoulin Islands (Lee,
1957) point to the presence of early man in Late-glacial as well as
early Postglacial time in the eastern United States. Quimby (1958)
related the geochronology of the Lake Michigan basin to archaeologi-
cal discoveries and infers an association of spruce-fir forest, masto-
dons, and fluted points from about 10,000 to 7,500 B.C. Williams
(1957) extended the latter to a more recent date, indicating no
obligate relationship between mastodons and spruce-fir.
The biologist who may wish to review the impressive archaeologi-
cal record of early man will profit by consulting Wormington's
excellent book (1957) and Sellards' equally readable account (1952).
Early man is not invariably associated with fluted points; the old
desert cultures such as those at Danger Cave in LTtah (Jennings,
1957) and at Frightful Cave in Coahuila (Taylor, 1956) represent
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 395
hunting-gathering people who did not prey on large animals. Fluted
points may be an independent New World invention ; they have not
been found with paleohthic sites in Siberia (Wormington, 1957).
In South America early man had arrived at least by early Post-
glacial time as is demonstrated by the well-known association of
man and sloth at Palli Aiki Cave, Chile. Cruxent and Rouse (1956)
and Rouse and Cruxent (1957) report Paleo-Indian sites in northern
Venezuela.
From the biological viewpoint it does not seem necessary to enter
the Interglacial man controversy. If the Tule Spring site, Nevada, is
correctly dated at older than 23,800 years, it clearly indicates that
prehistoric man arrived before the Wisconsin maximum of 17,000
years ago. Presumably this would require arrival in Alaska, at least
by early post-Sangamon time, of a people whose economy was
specialized for hunting large animals in treeless tundra. It seems
easier to establish a trans-Bering population in southern Alaska
than to understand how, during the Wisconsin glacial period, such a
population spread south through what is mapped as glaciated
terrain.
For the ecologist and biogeographer one point remains clear.
From the time of man's arrival we may assume a radical change in
fire frequency. In the strict sense, theoretical climatic climax vegeta-
tion in savanna and grassland areas (Stewart, 1951, p. 319), and
even in parts of the Eastern Deciduous Forest, cannot postdate
man's arrival. In addition to savannas many areas of temperate
forest may have been greatly modified and subcHmax, consolidation,
or even pioneer species favored at the expense of those typical
only of climax positions in plant succession. The paleoecological
dilemma posed by the B zone pine pollen period (Dansereau, 1953)
may be resolved in terms of an archaeological disclimax controlled by
early man. There is no longer much doubt about his presence in the
East at that time.
LATE PLEISTOCENE EXTINCTION
In the words of Darwin : " It is impossible to reflect on the changed
state of the American continent without the deepest astonishment.
Formerly it must have swarmed with great monsters; now we find
mere pigmies, compared with the antecedent allied races." {Voyage
of the Beagle, 1855, p. 222). In the hundred years since Darwin wrote,
396 P. S. MARTIN
discoveries in both prehistory and paleontology have enriched
considerably our knowledge of late Pleistocene fauna. Radiocarbon
dates (Fig. 4, Table II) confirm the fact, evident to Darwin and
Lyell, that extinction was mainly a Postglacial event. South of
Alaska there is abundant proof that the time of maximum glaciation
preceded most New World extinction.
Despite these refinements, the extinction of large mammals in
continental North and South America and of small mammals in the
West Indies has been a major unsolved problem, one certainly not
inappropriate in a symposium dedicated to such matters. Until the
cause or causes of extinction are understood, biogeographic and
ecological interpretations based on the assumption that all fossil
mammalian records are of paleoclimatic significance may be overly
bold, if not entirely erroneous. Specifically, I would question paleo-
climatic deductions based on fossil records of Marmota and Cervus
in northeastern Mexico, Erethizon (porcupine) and Hydrochoerus
(capybara) in the Melbourne beds of Florida, "musk-ox-like"
genera in New Mexico and Mexico, and Tapirus in Arizona (Haury
et al., 1950) and Pennsylvania. Strict application of the uniformi-
tarian doctrine is to be avoided in each case ; no responsible ecologist
would insist that modern tapir habitat, Tropical Rainforest and
Cloud Forest, extended into southern Arizona or eastern Pennsyl-
vania in the late Pleistocene.
As Darwin stressed in The Origin of Species, extinction is the
inevitable consequence of evolution and in itself will occasion no
surprise. Through the Cenozoic equid genera disappear; Hyra-
cotherium and others in the Eocene; Mesohippiis in the Oligocene;
Miohippus, Parahippus, and others in the Miocene; Calippus,
Hipparion, etc., in the Pliocene; and Nannippus and Plesippiis in
the early Pleistocene. They represent a record of replacement by
morphologically modified and adaptively improved types of horses.
In the late Pleistocene the extinction of North American Equus
and South American Equus and Hippidium is not an equivalent
event for it constitutes extinction without replacement. For perhaps
3,000 to 6,000 years in the Americas the horse was absent. Follow-
ing post-Columbian reintroduction, feral horses reoccupied grass-
land habitats with unseeming haste. Darwin (1855, p. 299) reported
that they spread from Buenos Aires to the Straits of Magellan, 1,300
miles, in 43 years.
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY
397
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Tai
3LE II. Radiocarbon Dates Associated with the Extinct Late Pleistocene Fauna
in America"
Sample
Location
Fauna
Comment
Years, B.P.
1.
L-290 R.
Santa Rosa Is.,
Calif.
Dwarf mam-
moth
Charred bone
29, 700 ±3000
2.
C-914
Tule Springs,
Bison alleni,
Ancient occupa-
> 23, 800
Nev.
mammoth,
camel
tion site, later
flooded
3.
M-38
Fairbanks area,
Bison crassi-
Horn sheaths from
16,400±2000
Alaska
cornis
gold-bearing
gravels
4.
L-244
Santa Rosa Is.,
Dwarf mam-
Wood from base
15,820±280
Calif.
moth
of mammoth-
bearing alluvium
5.
C-301
Fairbanks
''Extinct mam-
Wood from 30- to
12,622±750
Creek,
mal bones"
60-ft. depth
Alaska
6.
L-245
Winnemucca
Lake, Nev.
Horse, camel
Lowest occupa-
tion in Fish-
bone Cave
11,200±250
7.
C-484
Mylodon Cave,
Mylodon
Dated sloth dung,
10,800±570
Chile
no artifacts
10,864±720
8.
C-221
Gypsum Cave,
Nothrotherium
Dated sloth dung
10, 902 ±440
Nev.
shastense
10,075±550
9.
L-231
Sussex Co.,
N.J.
Mastodon
Peat associated
with remains
10,890±200
10.
L-137 G
Seward Penin-
—
Organic material **
10, 200 ±800
L-137 N
sula, Alaska
9,400±750
11.
L-303
Plainview,
Texas
Bison ?antiquiis
Snail shells from
bone bed with
Plainview
material
9, 800 ±500
12.
W-223
Pictograph
Musk-ox
Bones partly im-
9, 700 ±600
claim, S.D.
{Wvibos)
pregnated with
caronite
13.
M-282
Lenawee Co.,
Mich.
Mastodon
Wood immediately
above a tusk
9,568±1000
14.
A-9
Naco, Cochise
Mammuthus
Charcoal in clay
9,250±300
A-10
Co., Ariz.
columbt
matrix around
bones
15.
M-66
Orleton Farms,
Mastodon
Wood from im-
8,420±400
Ohio
mediately under
skeleton; first
two dates are of
black carbon
8, 460 ±400
9, 600 ±500
16.
C-485
Palli Aike
Sloth, horse,
Burned bones.
8,639±450
Cave, Chile
guanaco
with artifacts
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY
399
Ta!
BLE II. R
adiocarbon Dates .
Associated with tl
[le Extinct Late Pleis
tocene Fauna
in
America" — Continued
Sample
Location
Fauna
Comment
Years, B.P.
17.
A-30 to
Lehner site,
Mammuthus
Dates between 6,356 ±450 and
A-34,
Cochise Co.,
columbi
12,000db450; mammoth kill
A^Oa
Ariz.
should be older than overlying
A-40b
organic material d
7,000 B.P.
ated at about
18.
A-69
Murray Springs,
Cochise Co.,
Ariz.
Mammoth
Sample overlies
clay containing
bones
8,250±200
19.
A-67
Double Adobe,
Equus, Cants
Charred wood,
8,200±260
Cochise Co.,
dims, mam-
Sulphur Springs
Ariz.
moth. Bison
artifacts; same
site as C-216
20.
C-216
Double Adobe,
Equus, Canis
Mammoth lies
7,756±370
Cochise Co.,
dims, mam-
above the
Ariz.
moth. Bison
sample
21.
Y-341
Five-mile
Condor, extinct
Extinct scavan-
7,675±100
Rapids, Ore.
vulture
{Coragyps
occidentalis)
gers with at-
latls, burins,
flaked stone
tools
22.
C-823
Burnet Cave,
Extinct mam-
Sample from the
7, 432 ±300
N. M.
mals"
8- to 9-ft. level
in the fill
23.
M-67
Washtenaw Co.,
Mastodon
Acid-soluble car-
6, 100 ±400
Mich.
bonates from
tusk
6,300±500
24.
M-138
Cromwell, Ind.
Mastodon
Associated wood-''
5, 300 ±400
25.
W-288
Kassler Quad.,
Woolly mam-
Date on twigs
4, 885 ±160
Colorado
moth
under a bone,
possibly in-
trusive
26.
M-354
Lagoa Funda,
Minas Gerais,
Brazil
"Giant bear"''
3, 000 ±300
27.
L-211
St. Petersburg,
Fla.
Extinct mam-
mals
Charcoal*
2, 040 ±90
o All dates have been published in Science. Initials indicate the laboratory: L, Lamont;
C, Chicago; M, Michigan; W, Washington; Y, Yale; A, Arizona.
* Organic material from muck of deposits that fill valleys of minor streams, "... under-
lain by blue-gray silt or by an older muck that contains fossil remains such as elephant,
horse, and bison, which are conspicuously absent in the dated muck.
" Equus excelsus, Camelops sp., Sangamona sp., Asinus conversidens, Euceratherium
collinum, Preptoceras sinclairi, Stockoceros onusrosagris, Bison antiquus, and Rangifer?
fricki.
'' "Material from this site should date the age of the extinct Giant Bear."
* Charcoal from newly exposed canal. "Associated with extinct Seminole Field mam-
mals, an archaic spear point, ilint chips and burned bone."
•^ Tusk fragments of this mastodon yielded a much older date, M-139, 12, 630 ±1000
years {Science, 127: 1099).
400
p. S. MARTIN
c
o
15
10
5
MARSUPIALS
10
5
M
INSECTIVORES
PI
M
P
PI
15 •
PRIMATES
/
10 ■
/
5 ■
^
J
10
5
M
RABBITS
PI
15
10
5
'I
M
RODENTS
— T-
Pl
/ (40)
10
5
• I
M F
CETACEANS
PI
I I I
M P PI
Geological Epoch
15
10
5
EDENTATES
(28)
J
M
PI
15-
10'
5.
CARNIVORES
pinnipeds
M
PI
10
5
NOTOUNGULATES AND
LIPTOTERNS
M P PI
PROBOSCIDEANS
10-
5"
PERISSODACTYLS
15 ■
ID-
S'
I I
M P
ARTIODACTYLS . .
I
-T-
Pl
M
PI
Fig. 5. Caption on facing page.
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 401
Before proceeding directly into a consideration of possible causes,
it appears essential to examine the nature of late Pleistocene extinc-
tion more closely [cf. Simpson (1953) for a general treatment of
phyletic extinction]. If it is no different from that of the early
Pleistocene or Tertiary there is little point in proceeding farther.
Extinction without Replacement
In addition to Equus, cited above, the following North American
genera, representing specific ecological life forms with respectable
Tertiary lineages, disappeared in the late Pleistocene or sub-Recent
time: the elephants and mastodons Mammuthus and Mammut,
the camels Tanupolama and Camelops, the Old World antelope
Saiga, the cervid deer Sangamo?ia, and Cervalces, the shrub-oxen
Symbos, Eucemtherium, and Preptoceras, the pronghorns Breameryx
and Stockoceros, the giant beaver Castoroides, and others. They re-
flect abandonment of grazing and browsing habitats by roughly three-
quarters of the mammalian herbivore fauna. In the West Indies four
genera of ground sloths and sixteen of hystricomorph rodents, also
herbivores, disappeared in sub-Recent time.
The general rule that abandonment of life forms and the disap-
pearance of genera or subfamilies without replacement occurred only
in the late Pleistocene may have a single minor exception. Boro-
phagus, a New World equivalent of the hyaenid life form, is unknown
beyond the First Interglacial (Hibbard in Flint, 1957, p. 462). How-
ever, at no time since the extermination of the Upper Cretaceous
duck-bills and other herbivorous dinosaurs has there been un-
balanced extinction of equal magnitude.
Fig. 5. Generic extinction rate curves for various mammalian orders.
The number of genera last recorded divided by estimated age for each
epoch is shown for three Late Cenozoic epochs: M = Miocene, 17 million
years; P = Pliocene, 11 million years; PI = Pleistocene, one million years.
Pleistocene extinction rates rose sharply in the primates, rodents, eden-
tates, fissipeds, notoungulates, liptoterns, proboscideans, perissodactyls,
and artiodactyls. There was no comparable rise in extinction rates among
the insectivores, rabbits, cetaceans, pinnipeds, and sirenians. Data on
extinct genera were obtained from Simpson (1945) ; orders with poor late
Cenozoic fossil records, as the bats, pangolins, and hyraxes, are not
included.
402 V. S. MARTIN
Cenozoic Extinction Rates Rise in the Pleistocene
Extinction rates in number of genera per million years for several
mammalian orders increased greatly at the end of the Cenozoic
during the Pleistocene (Fig. 5). The data from Simpson (1945) repre-
sent last appearances of genera in each of twenty mammalian orders.
To obtain extinction rates, one divides the number of genera last
recorded in each period by the geological estimate of elapsed time,
17 million years for the Miocene, 11 for the Pliocene, and 1 for the
Pleistocene.
It is obvious that only certain orders exhibit a strong Pleistocene
effect. Those include the artiodactyls, proboscideans, marsupials,
edentates, rodents, perissodactyls, fissipeds, and primates. Certain
groups with moderately good late Cenozoic fossil records, as the
cetaceans and pinnipeds, appear unaffected. The extinct Pleistocene
genera of marsupials are all Australian and include large kangaroo
and phalangeroid herbivores. Within the primates, 8 of 14 extinct
Pleistocene genera were lemur-like forms from Madagascar. Among
the rodents, a rise in Pleistocene extinction rate can be attributed
in part to the extinction of insular genera, 15 of them West Indian.
Regarding the entire late Cenozoic record of mammals, extinction
rates rise from 25 per million years in the Miocene, 40 in the Plio-
cene, to 203 in the Pleistocene. From this we may believe that
Pleistocene extinction transcends that of the rest of the Cenozoic.
Was it caused by climatic change of the Glacial periods?
Pleistocene Extinction Rates Rise in the Last Glacial Period
Hibbard's valuable list (1958; also in Flint, 1957) of Pleistocene
mammals shows a considerable measure of extinction in the First
Interglacial, the Aftonian. However, with the single exception of
Borophagus, there is continual replacement of generic types until
the Wisconsin.
Estimating the Glacial periods arbitrarily at 100,000 years each
and the interglacials at 250,000 years we obtain for North America
the following extinction rates, expressed as number of genera per
100,000 years: Nebraskan, 1.0; Aftonian, 6.0; Kansan, 5.0; Yar-
mouth, 1.2; Illinoian, 1.0; Sangamon, 0.0; Wisconsin, 31.0 (ter-
minal records from Hibbard in Flint, 1957, with addition of Floridian
Melbourne mammals). On this basis it is possible to conclude (1)
that the extinction rate in the Wisconsin was considerably higher
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 403
than earlier in the Pleistocene and (2) that extinction is not related
to the Glacial period or to the climatic change brought on by
glaciation.
In part such figures may be an artifact of paleontological sampling.
Late Pleistocene sediments, bogs, caves, and alluvium, are better
preserved than older deposits exposed to a longer history of geo-
logical wear and tear. The late Pleistocene should be better known
than a preceding fauna. Nevertheless, accepting the fossil record at
face value, it seems that extinction was predominantly a Wisconsin
phenomenon. The facts do not agree with the proposal that the rise
in Pleistocene extinction rates is the result of climatic change.
Late Pleistocene Extinction Affected Only Large Animals
Obviously, this is not strictly true, as Eisley (1946) and Gill (1955)
pointed out. On the one hand, cetaceans and pinnipeds were unaf-
fected; on the other, small to medium-sized West Indian mammals,
lizards, and birds disappeared. In tropical forests and savannas
certain edentates survive, such as the anteaters and tree sloths.
Their plains-dwelling relatives of subequal size, such as Nothro-
therium and Chalmytherium, disappeared. Moose, elk, white-tailed
deer, and probably bison survived in temperate forests while, except
for one species of pronghorn and the mule deer, the grasslands were
stripped of large herbivores.
Nevertheless, the size relationship is crucially important. The
vulnerability on most islands of relatively small animals (from the
size of a Norway rat to that of a beaver) can be contrasted with
that on continental areas where, aside from possible trimming of
marginal populations, the extinction of such small animals did not
occur at the end of the Pleistocene. I am indebted to K. C. Parkes
for pointing out that, of the reasonably rich late Pleistocene passerine
avifauna, there are recognized only two extinct genera, both in the
family Icteridae and both cowbirds, Pandanaris and Pyelorhamphus
(Wetmore, 1956). It requires no great imagination to suggest that
they shared a commensal table with the modern cowbird genera,
Molothrus and Tangavius, and that extinction of the large herbivores
reduced the variety of ecological niches for both scavenger and
cowbird life forms. The extinct scavengers are more numerous and
include the genera Breagyps, Teratornis, Cathartornis, Neogyps, and
Neophrontops.
404 P. S. MARTIN
Extinction Marks the Boundary between the Pleistocene and
Recent
In the Rocky Mountain region Hunt (1953) reported that the
disappearance of such large mammals as elephants, camels, and
horses coincides with a widespread unconformity in the late Quater-
nary deposits. He correlated this break with the drought of the
Altithermal and finds that extinction immediately predates it.
While this relationship may be of geological utility in western North
America, chronological detail does not bear out such a distinction
between "Pleistocene" and "Recent" elsewhere on the continent.
In Alaska thin gravels and clays containing remains of extinct
mammals are at least of Late-glacial age or older. Organic material
overlying the remains of elephant, horse, and extinct bison has been
dated at 10,200±800 (L-137G) and 9,400±750 (L-137N) years
B.P., (see discussion by Sigafoos and Hopkins in Broecker et al.,
1956, pp. 156-157). Horn sheaths of Bison crassicornis were dated
at 16,400 ±2000 (M-38).
In Mexico the Upper Becerra Peat, containing remains of the
mammoth M. imperator is also considered as older than 10,000
B.P. (Wormington, 1957, pp. 91-99). Hibbard (1955) considered it
early Wisconsin. MacNeish's important and, in large part, unpub-
lished studies in southern Tamaulipas (1950, 1955) have revealed
leaflike points associated elsewhere with the Becerra mammoths, but
there is no evidence of extinct animals in his radiocarbon -dated
middens, which cover the entire Post-glacial period (personal com-
munication). Apparently extinction in both Mexico and Alaska
preceded that in the Rocky Mountains.
In Florida and South America extinction postdated the Alti-
thermal. Unquestionably this is the most controversial aspect of the
extinction chronology, partly because it all but eliminates climatic
change as an extinction cause. The vastly rich fauna of the Mel-
bourne and Seminole beds of Florida was dated on archaeological
and geochronological grounds by Rouse (1952) at 4,000 to 2,000
years ago. A radiocarbon date, L-2N, 2,040 ±90, of charcoal from a
newly exposed canal is "associated with extinct Seminole Field
mammals, an 'archaic' spear point, flint chips, and burned bone . . .
the date seems anomalously low in view of the extinct fauna" (field
description from unidentified collector in Broecker et al, 1956, p.
161). The fauna of the Seminole field includes the porcupine, capy-
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 405
bara, dire wolf, short-faced bear, smilodon, ground sloths, glypto-
donts, horses, a tapir, extinct peccaries, camels, mastodons, mam-
moths, and various small mammals conspecific with living species
(Cooke, 1945, pp. 308-309). Forty years of scrutiny have not re-
solved the apparent contradiction that a rich and varied extinct
savanna fauna survived here until a very late date, perhaps 4,000 to
2,000 years ago, contemporaneous with archaic man (Rouse, 1952;
Heizer and Cook, 1952).
In South America an extinct mastodon, Ciivieronius, was found
associated with pottery (Spillmann in Osborn, 1936, pp. 571-574).
More recently a radiocarbon sample from Minas Gerais, 3,000 ±
300 B.P. (M-354), "... should date the age of the extinct Giant
Bear" (genus unspecified, collected by Evans and reported in Crane,
1956, p. 672). The recent review of mastodon remains and radio-
carbon dates by Williams (1957) indicates that outside Florida the
genus endured in eastern North America until at least 6,000 years
ago and is associated with archaic artifacts.
One waits with keen anticipation additional study of these and
other problem areas such as the West Indies. Tentative conclusions,
based on the harvest of eight years of radiocarbon dates associated
with extinct animals, follow: (1) Mexican and Alaskan large mam-
mals were the first to be eliminated, this in Late-glacial time;
(2) the Plains Megafauna disappeared in the early part of the Post-
glacial period; (3) eastern temperate forest and tropical rainforests
were the last continental refugia for large mammals; (4) the Floridian
savanna, surrounded by forest, served as a refuge for plains her-
bivores after they had disappeared elsewhere in western North
America.
A LATE PLEISTOCENE EXTINCTION MODEL
An idealized descriptive model designed to illustrate probability
of extinction within the late Pleistocene terrestrial fauna would in-
clude many factors. Without doing violence to such a model we may
be able to limit it to three: (1) body size, (2) habitat, and (3) total
range of the species. Reasons for this choice and certain apparent
exceptions to the model will become evident subsequently.
The probability of extinction in the late Pleistocene appears to
have been maximized by large body size, usually accompanied by
low values of r (intrinsic rate of increase), and T (mean generation
406
p. S. MARTIN
pericnd); by open habitat, i.e., savanna, grassland, tundra, and
desert, and by limited range, either insular or on such ecological
islands as Alpine meadows surrounded by forest. Conversely, sur-
vival was enhanced by small size, forest habitat, and a large range
for the species in question.
O
UJ
N
CO
NORWAY RAT
PRONGHORN
MAMMOTH
FOREST
SAVANNA GRASSLAND DESERT
BIOCHORE
Fig. 6. A Late Pleistocene extinction model for New World mammals.
This generalized model is intended to indicate the interaction of variables
that appear to have been important in determining probability of ex-
tinction for any particular species or population. Points beneath the sur-
face of the solid lie within the region of high extinction probability; those
above the surface lie in the region of high probability of survival.
The primary question in late Pleistocene extinction revolves
around the herbivores (trophic level A2 in Lindeman's system).
According to ecological and evolutionary theory it is axiomatic
that a reduction in the number of species operating at one level will
require reduction at higher trophic levels. Our present task is to
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 407
describe the pattern of herbivore extinctions, with the assumption
that extinction of certain wolf, cat, cowbird, vulture, and vampire
life forms followed inevitably.
Figure 6 is a diagrammatic attempt at such a descriptive model,
showing high and low regions of extinction probability. The high
regions lie within the shaded portion of the solid ; the low regions lie
above in the unshaded portion. Following Dansereau (1957), habi-
tat can be divided conveniently into the four biochores: forest,
savanna, grassland, and desert. All terrestrial communities from the
equator to the Arctic fall within one of these units. Animal body size
is divided into four classes, represented respectively by (1) Norway
rat, (2) Norway rat to beaver, (3) beaver to pronghorn, (4) prong-
horn to mammoth. Total range of the species in square miles is
arbitrarily listed as very small (less than 2,000), small (2,000-
20,000), medium (20,000-200,000), and large (200,000 and more).
Three specific examples, which were used in constructing the model,
illustrate its predictive function :
Case A. Upper-left-rear corner of the diagram. Small animals in a
small area of forest, Puerto Rico.
Extinct. Nesophontes, an insectivore; Acratoc7ius, a small ground
sloth ; and six genera of hystricomorph rodents: Heptaxodon, Elasmo-
dontomys, Isolobodon, and Proechimys (surviving on mainland South
America), Heteropsomys, and Homopsomys.
Surviving. Eleven genera of native bats; introduced Rattus and
Mus.
Extinction intensity. Heavy.
Case B. Upper-left-front corner. Small animals in extensive
forest, eastern North America.
Extinct. None known.
Range possibly reduced : Neofiber, round-tailed vawskrSit ; Erethizon,
porcupine; Didelphis, opossum.
Surviving. Twenty-one genera of native rodents, various other
small terrestrial mammals and bats.
Extinction intensity. Very light.
Case C. Lower-center and right-front corner. Large animals in
extensive desert, grassland, and savanna habitats, the Basin and
Range province and western North America generally.
Extinct. Mammuthus, mammoths of two or three species; Mam-
408 P. S. MARTIN
mut, mastodon; Paramylodon, Nothrotherium, and Megalonyx,
ground sloths; Glyptotherium, glyptodont; Platygonus, peccary;
Tanupolama, long-legged llama; Camelops, camel; Sangamona,
extinct deer; Breameryx, tar-pit pronghorn; Stockoceros, pronghorn;
Euceratherium and Preptoceras, shrub-oxen; Bootherium, musk-ox;
Equus, horse and ass, various species.
Surviving. Antilocapra, pronghorn; Odocoileus, mule deer; Bison,
buffalo, one species only.
Extinction intensity. Heavy.
In addition to these three cases it is obvious that other regional
faunas fulfill the requirements. For example, the Greater Antilles ex-
perienced complete extinction of all beaver-sized and larger animals
and partial survival only among the small mammals and reptiles.
In Alaskan tundra and Mexican steppe there was a high extinction
rate for large herbivores (pronghorn size and over) , but not for small
or medium-sized mammals. Applying the model to South America
we would expect heavier extinction on the pampas and campo
cerrado savannas than in the Amazonian rainforest.
Paleontology of the Pampean formation (Simpson, 1940) showed
that a variety of ground sloths, glyptodonts, and other edentates,
horses, certain camels, and the native ungulates, as the macra-
ucheniids, toxodonts, mesotheres, and hegetotheres, disappeared
from the plains areas. Some extinction of forest forms must have
occurred, probably more than the scanty fossil record of mastodonts
and bears would indicate (tropical forest Pleistocene sediments are
all but unknown) . However, survival in the forest exceeds that on the
plains. Peccaries, large edentates, monkeys, tapirs, capybaras, and
various deer in the forest and forest margin contrast with the pres-
ence of only two large native herbivores in the pampas and in Pata-
gonia, the guanaco or wild llama and the pampas deer.
If the model is adequate in these cases, it by no means explains
lack of extinction under certain circumstances that call for it. The
survival of four species of native camamelids in South America, at
least two of them with relatively narrow ranges in the i\ndean Puna
is mystifying, both in terms of the model and the extermination of
the camamelids in North America. The survival of Capromys ingra-
hami on one of the smaller Bahaman Keys and of Testudo, the giant
tortoises of the Galapagos, introduce an additional problem that
appears worthy of special treatment.
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 409
WEST INDIAN VERTEBRATES AND GALAPAGOS TORTOISES
Late Pleistocene and sub-Recent insular extinction throughout
most of the world appears to have been intense. Certain oceanic
islands exhibit the phenomenon of extermination without replace-
ment noted in North and South America. Giant marsupials inhabited
Australia (Gill, 1955), large flightless birds survived in New Zealand
at least until 1300 a.d. (Deevey, 1955), and giant lemurs, tortoises,
and large birds lived in Madagascar (Sibree, 1915). West Indian
mammals, reptiles, and birds experienced extermination both of
relatively medium-sized genera (tortoises and ground sloths) and of
many smaller rodents. In this respect West Indian extinction differs
from the continental record. Summary articles by Allen (1911) and
Matthew (1919) have been superseded by Simpson's valuable zoo-
geographic synthesis (1956). Allen (1942) discussed most of the ex-
tinct mammals. Except for Cuban ground sloths (Allen, 1918;
Aguayo, 1950) and Jamaican bats and rodents (Anthony, 1920;
Koopman and Williams 1951; Williams, 1952b), the distribution of
most of the extinct mammals is covered in Miller and Kellogg's
Checklist (1955).
The extinction chronology is rather baffling and is not simplified
by the possibility that certain forms such as Nesophontes may yet be
found to survive in remote mountainous districts. I am indebted to
K. F. Koopman for pointing out that more than 300 years elapsed
between discovery of the islands by western man and the first serious
scientific description of their fauna. Extermination in this interval,
perhaps at the hands of superior competitors as Rattus, or as the
result of clearing and cultivation, will be difficult to distinguish from
prehistoric extermination. Nesophontes, for example, appears to
have been contemporaneous with Rattus. In contrast Testudo and
various ground sloths almost surely were not present at the time of
the conquest. Ground sloths may have existed into the ceramic
period (Aguayo, 1950), and the giant rodent Quemisia was ap-
parently known to Oviedo (Allen, 1942), but there is no certain
evidence of other large hystricomorphs (Elasmodontomys, Clidomys,
and Amblyrhiza) in post-Columbian middens and it is most unlikely
that their presence would have gone unrecorded by early observers.
Simpson listed twenty-two extinct genera of terrestrial mammals
in the Greater Antilles. Even assuming some unnecessary splitting,
the fossil fauna is quite impressive. By comparison, the present sur-
410 P. S. MARTIN
viving fauna of four genera is depauperate : Solenodon on Hispaniola
and Cuba, Oryzomys (recently extinct?) on Jamaica, Capromys (here
to include Geocapromys) on Cuba, the Plana Keys, Jamaica, and the
Swan Islands, and the closely related Plagiodontia on Hispaniola.
Considering the poverty of chiropteran remains elsewhere, the
fossil record of the West Indian bats is remarkably good. It has been
used to identify relative faunal ages in Jamaica (Koopman and
Williams, 1951 ; Williams 1952b). At first glance the presence of two
genera of fossil bats now extinct in Jamaica seems to contradict the
principle I have noted earlier that late Pleistocene extinction did not
affect such animals. Other than commensals and parasites of large
herbivores, such as the cowbirds and vampires, we would predict no
elimination of life forms among the bats and birds. In theory climatic
change during the Wisconsin and earlier Glacial advances altered
the ecological opportunities for various genera and changed faunal
composition at low latitudes. However, it is my present thesis that
generic extinction did not accompany such events. Koopman and
Williams' studies make it clear that the local extirpation of bats
{Tonatia and Brachyphylla) in Jamaica was accompanied by replace-
ment by related genera in the same subfamily. Tonatia and Brachy-
phylla survive in Central America and Hispaniola respectively. The
Jamaican bat fauna remained rich and bears no resemblance to the
annihilation experienced by the terrestrial herbivores. The shift in
the species composition of bats may be attributed to climatic change.
On the other hand, the survival of a rodent, Capromys {Geo-
capromys) ingrahami, on the tiny Plana Keys and of C. thoracatus
on the Swan Islands, seems a serious violation of the general rule
that the smaller the surface the greater the vulnerability to extinc-
tion (Fig. 6). The record of Capromys is instructive. C. ingrahami
was described in 1891. Closely related fossil populations were sub-
sequently found on the larger Bahaman Islands, Crooked, Eleuthera,
Long, Great Exuma, Great and Little Abaco. In 1955 Rabb and
Hayden (1957) revisited the Plana Keys, collected three specimens
of the "cootie" and noted that the island had undergone little change
since Ingraham's visit. East Plana Key is a small, rocky islet not
more than 50 feet above the ocean, one-half mile wide, four to five
miles long and "... entirely without fresh water except in the rainy
season, when pools of fresh water may be found in holes in the rocks"
(Allen, 1891). In the absence of fresh water it is doubtful that the
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 411
Carib Indians ever maintained permanent settlement on the island;
Rabb and Hayden note that it is uninhabited at present. This fea-
ture may be crucial. We can attribute the remarkable survival of
Capromys both on the Plana Keys and on the Little Swan Islands
to lack of permanent prehistoric habitation. For the archaeologist
this carries the corollary that the other Bahaman Islands were more
intensively occupied.
The foregoing account emphasizes the mammalian fossil record.
In addition, there were "giant" late Pleistocene lizards (Hecht, 1951,
1952) turtles (Williams, 1950, 1952a), and birds (Wetmore, 1937).
The record of the tortoises, Testudo, is an important adjunct to the
extinction of the large mammals. An interesting sidelight is their
apparent extinction in the Greater Antilles before the main period
of mammalian extinction (Williams, 1952a, p. 554). Elsewhere they
evolved through the Tertiary and into the late Pleistocene. Species of
relatively small size survive in northern South America. The New
World giant tortoises remain only on the Galapagos. As in the case of
Geocapromys on the Plana Keys, there is reason to believe that these
islands escaped permanent occupation in prehistoric times. Heyer-
dahl and Skjolsvold (1956) reported no archaeological evidence of
prehistoric occupancy of the Galapagos other than temporary or
seasonal visits, and no preceramic contact. With a long reproductive
time lag and no special defense against man, the giant tortoises
must have been especially vulnerable to human predation. This may
explain their early demise compared to the rest of the fauna in Cuba
(Williams, 1952a). The Galapagos and Plana Key exceptions to the
generalized extinction model (Fig. 6) indicate that it will apply only
to regions permanently inhabited by prehistoric man.
CLIMATIC INDICATORS, EXTINCTION, AND MAN
"A hypothesis which implies that practically all the important
fossil forms had existed until a comparatively Recent date and then
become extinct in a geologically short period of time had seemed
equally improbable to the writer; and yet it is to such a conclusion
that a study of the evidence leads" (Romer, 1933). Flint (1957),
Osborn (1936, pp. 1512-1513), and Sauer (1944) are also among
those who indicate that prehistoric man was the principal agent of
late Pleistocene extinction. If circumstantial evidence points to man,
it does not reveal his methods. Sauer's fire-drive hypothesis (1944)
412 p. S. MARTIN
may be Important in understanding the possible hunting techniques
of use against the large, gregarious plains herbivores. However, as
Eisley (1946) noted, even the most ardent proponent of fire as an
ecological force may hesitate to attribute the extinction of forest
mastodons, the giant beaver {Castoroides) , and the West Indian
hystricomorphs to this technique. The mysterious survival of large
African herbivores frustrates sweeping conclusions.
For paleoecological purposes it seems necessary to consider the
significance of large vertebrates as climatic indicators. If prehistoric
man is an extinction agent, how are we to interpret shifts in range in
terms of paleoecological uniformitarianism? Tapirs and capybaras,
today denizens of tropical forest, formerly ranged far to the north,
respectively to Oregon and Pennsylvania and to Florida and Arizona.
Are there compelling reasons to believe that, in the absence of man,
these animals would not occupy the same range under the present
climate?
The porcupine, opossum, and armadillo have notably extended
their ranges within historic time. The opossum and armadillo moved
northward (Guilday, 1958; Fitch et at., 1952), the porcupine south-
ward, into Sonora (Benson, 1953). These extensions can be at-
tributed to climatic change. They can also reflect the reoccupation
by these species of marginal positions in their former range, from
which they had been eliminated in prehistoric time by human preda-
tion. The mountain top populations of Marmota flaviventris in
southern Arizona, New Mexico, and northeastern Mexico were
trimmed. Subalpine and boreal habitats, apparently suitable for
marmots, persist in these areas today.
The giant tortoises, like the tapir and capybara, are another
group in which a complacent assumption of tropicality is read into
their ranges, for example, by Crook and Harris (1958, p. 241). Sur-
vival of tortoises only on remote oceanic islands seems to be at-
tributable to the circumstance that they here escaped pre-Columbian
extermination by man rather than to climatic change. Assumptions
of climatic change based on the present distributions of relatives of
the late Pleistocene fossil vertebrates are gratuitous as long as an
alternate cause of extirpation is possible. In brief we may inquire
whether tropical forests and remote islands constitute refugia from
climatic change or from the hunting practices of prehistoric man.
For sensitive indicators of climate and past environments it may
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 413
be necessary to consider only plant distributions plus those small
animals whose population density and reproductive capacity could
keep pace with human predation.
Within our present knowledge there seems little agreement on the
problem of extinction and man's role in it. Most authors who have
reviewed the problem reduce it to the outcome of an interaction of
all factors that can limit animal populations — predation, competi-
tion, parasitism, climatic change, evolutionary lag during environ-
mental stress, and also the effect of man (Colbert, 1938; Gill, 1955;
Hamilton, 1939; Osborn, 1906; Romer, 1945; Simpson, 1931, 1953).
I believe this multiple hypothesis does injustice to the temporal
and ecological record, i.e., (1) differential loss of large animals, (2)
lack of evidence of major climatic change during the extinction
period, (3) the narrow chronological range in which extinction oc-
curred, and (4) the phenomenon of removal without replacement. It
would appear that within the Cenozoic the late Pleistocene environ-
ment had some unique features. Man is the only one clearly
identified.
Acknowledgments
In part the viewpoints expressed grew out of seminars and less formal
discussions on Pleistocene matters at the universities of Michigan, Yale,
Montreal, and Arizona. In particular I would thank the following for their
help: P. Dansereau, M. B. Davis, E. S. Deevey, J. A. Elson, R. F. Flint,
F. K. Hare, B. E. Harrell, E. W. Haury, J. J. Hester, C. W. Hibbard,
K. F. Koopman, J. F. Lance, A. and D. Love, C. H. Lowe, G. Lowther,
M. Martin, J. E. McDonald, J. E. Mosimann, J. G. Ogden, G. B. Rabb,
J. Schoenwetter, T. L. Smiley, and D. R. Whitehead. Mrs. Helen Griffin
provided valuable clerical aid. I am indebted especially to palynologists
F. H. Barclay, M. B. Davis, E. B. Leopold, and D. A. Livingstone, who
forwarded advance copies of their unpublished pollen diagrams.
REFERENCES
Aguayo, C. G. 1950. Observaciones sobre mamiferos cubanos extinguidos.
Bol. hist, natural soc. Felipe Poey, 1: 121-134.
Allen, G. M. 1911. Mammals of the West Indies. Bull. Museum Comp.
ZooL, 54: 175-263.
. 1918. Fossil mammals from Cuba. Bull. Museum Comp. ZooL,
62: 133-148.
. 1942. Extinct and Vanishing Mammals of the Western Hemisphere.
American Committee for International Wild Life Protection, Lan-
caster, Pa.
414 p. S. MARTIN
Allen, J. A. 1891. Description of a new species of Capromys from the
Plana Keys, Bahamas. Bull. Am. Museum Nat. Hist., 3: 329-336.
Andersen, S. T. 1954. A late-glacial pollen diagram from southern Michi-
gan, U. S. A. Danmarks Geol. Under s^gelse, 80: 140-155.
Antevs, E. 1954. Climate of New Mexico during the last Glacio-Pluvial.
J. Geol., 62: 182-191.
Anthony, H. E. 1920. New mammals from Jamaica. Bull. Am. Museum
Nat. Hist., 42: 469-476.
Barendsen, G. W., E. S. Deevey, and L. J. Gralenski. 1957. Yale natural
radiocarbon measurements III. Science, 126: 908-919.
Benson, S. B. 1953. A record of the porcupine (Erethizon dorsatum) from
Sonora, Mexico. /. Mammal., 34: 511-512.
Braun, E. L. 1951. Plant distribution in relation to the glacial boundary.
Ohio J. Set., 51: 139-146.
. 1955. The phytogeography of unglaciated Eastern United States
and its interpretation. Botan. Rev., 21: 297-375.
Broecker, W. S., J. L. Kulp, and C. S. Tucek. 1956. Lamont natural
radiocarbon measurements III. Science, 124: 154-165.
Cain, S. A. 1944. Pollen analysis of some buried soils, Spartanburg
County, South Carolina. Bull. Torrey Botan. Club, 71: 11-22.
Chaney, R. W., and H. L. Mason, 1934. A Pleistocene flora from Santa
Cruz Island, California. Carnegie Inst. Wash. Puhl., 415: 1-24.
Clark, J. G. D. 1952. Prehistoric Europe. Methuen, London.
Clisby, K. H., and P. B. Sears. 1956. San Augustin Plains— Pleistocene
climatic changes. Science, 124: 537-539.
Colbert, E. H. 1938. The Pleistocene mammals of North America and
their relations to Eurasian forms. In Early Man, G. G. MacCurdy,
Editor. Lippincott, London. Pp. 173-184.
Cooke, C. W. 1945. Geology of Florida. Florida Geol. Survey, Geol. Bull.,
29: 1-339.
Core, E. L. 1949. Original treeless areas in West Virginia. /. Elisha
Mitchell Sci. Soc, 65: 306-310.
Crane, H. R. 1956. University of Michigan radiocarbon dates. Science,
124: 664-672.
Crook, W. W., and R. K. Harris. 1958. A Pleistocene campsite near
Lewisville, Texas. Am. Antiquity, 23: 233-246.
Cruxent, J. M., and I. Rouse. 1956. A lithic industry of Paleo-Indian
type in Venezuela. Am. Antiquity, 22: 172-179.
Dansereau, P. 1951. Description and recording of vegetation upon a
structural basis. Ecology, 32: 172-229.
. 1953. The postglacial pine period. Trans. Royal Soc. Can., 47:
23-38.
1957. Biogeography, an Ecological Perspective. Ronald, New York.
Darlington, H. C. 1943. Vegetation and substrate of Cranberry Glades,
West Virginia. Bot. Gazette 104: 371-393.
Darwin, C. 1855. Journal of Researches. Harper, New York.
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 415
Davis, J. H. 1946. The peat deposits of Florida. Florida Geol. Survey, Geol.
Bidl., 30: 1-247.
Davis, M. B. 1957. Late-glacial Pollen Diagrams from Central Massa-
chusetts. Ph.D. Thesis, Harvard University (unpubhshed).
Deevey, E. S. 1949. Biogeography of the Pleistocene. Bull. Geol. Soc. Am.,
60: 1315-1416.
. 1951. Late-glacial and postglacial pollen diagrams from Maine.
Am. J. Sci., 249: 177-207.
. 1953. Paleolimnology and climate. In Climatic Change, H.
Shapley, Editor. Harvard University Press, Cambridge, Mass.
. 1955. Paleolimnology of the upper swamp deposit. Pyramid
Valley. Records Canterbury Museum {New Zealand), 6: 291-344.
-. 1957. Limnologic studies in Middle America. Trans. Conn. Acad.
Arts Sci., 39: 213-328.
Deevey, E. S., and R. F. Flint. 1957. Postglacial hypsithermal interval.
Science, 125: 182-184.
Denny, C. S. 1951. Pleistocene frost action near the border of the Wis-
consin Drift in Pennsylvania. Ohio J. Sci., 51: 116-125.
. 1956. Surficial geology and geomorphology of Potter County,
Pennsylvania. U. S. Geol. Survey Prof. Paper, 288: 1-72.
Dillon, L. S. 1956. Wisconsin climate and life zones in North America.
Science, 123: 167-176.
Drury, W. H. 1956. Bog flats and physiographic processes in the upper
Kuskokwim River region, Alaska. Contribs. Gray Herbarium Harvard
Univ. 178: 1-127.
Dylik, J. 1954. (The problem of the origin of loess in Poland.) Biul.
Peryglacjalny (Lodz), /; 19-30, 125-131. (In Polish, English sum-
mary.)
Eisley, L. C. 1946. The fire-drive and the extinction of the terminal
Pleistocene fauna. Am. Anlhropogist, 48: 54-59.
Emiliani, C. 1955. Pleistocene temperatures. /. Geol., 63: 538-578.
Fitch, H. S., P. Goodrum, and C. Newman. 1952. The armadillo in the
southeastern United States. /. Mammal., 33: 21-37.
Flint, R. F. 1957. Glacial and Pleistocene Geology. Wiley, New York.
Frenzel, B., and C. Troll. 1952. Die Vegetationszonen des nordlichen
Eurasiens wahrend der letzten Eiszeit. Eiszeitalter u. Gegenwart, 2:
154-167.
Frey, D. G. 1951. Pollen succession in the sediments of Singletary Lake,
North Carolina. Ecology, 32: 518-533.
. 1953. Regional aspects of the Late-glacial and Post-glacial pollen
succession of southeastern North Carolina. Ecol. Monographs, 23:
289-313.
-. 1955. A time revision of the Pleistocene pollen chronology of
southeastern North Carolina. Ecology, 36: 762-763.
Gill, E. D. 1955. The problem of extinction with special references to
Australian marsupials. Evolution, 9: 87-92.
416 P. S. MARTIN
Goodlett, J. C. 1954. Vegetation adjacent to the border of the Wisconsin
Drift in Potter County, Pennsylvania. Harvard Forest Bull., 25: 1-93.
Griscom, L. 1932. The Distribution of Bird-Life in Guatemala. Bull. Am.
Museum Nat. Hist., 64: 1-439.
. 1950. Distribution and origin of the birds of Mexico. Bull.
Museum Comp. Zool., 103: 341-382.
Guilday, J. E. 1958. The prehistoric distribution of the opossum. /.
Mammal., 39: 39-43.
Hack, J. T. 1953. Geologic evidence of late Pleistocene climates. In
Climatic Change, H. Shapley, Editor. Harvard University Press,
Cambridge, Mass.
. 1955. Geology of the Brandywine area and origin of the upland
of southern Maryland. Geol. Surv. Prof. Paper, 267 A: 1-41.
Hamilton, W. J. 1939. American Mammals. McGraw-Hill, New York.
Hansen, H. P. 1947. Postglacial forest succession, climate, and chronology
in the Pacific Northwest. Trans. Am. Phil. Soc, 37: 1-130.
. 1953. Postglacial forests in the Yukon Territory and Alaska. Am.
J. Sci., 251: 505-542.
Hare, F. K. 1954. The boreal conifer zone. Geograph. Studies, 1: 4-18.
Harrell, B. E. 1951. The Birds of Rancho del Cielo, an Ecological Investi-
gation in the Oak-Sweet Gum Forests of Tamaulipas, Mexico. M. A.
Thesis, University of Minnesota (unpublished).
Haury, E. W., et al. 1950. The Stratigraphy and Archaeology of Ventana
Cave. University Arizona Press, Tucson.
Hecht, M. K. 1951. Fossil lizards of the West Indian genus Aristelliger
(Gekkonidae). Am. Museum Novitates, 1538: 1-33.
. 1952. Natural selection in the lizard genus Aristelliger. Evolution,
6: 112-124.
Heizer, R. F., and S. F. Cook. 1952. Fluorine and other chemical tests of
some North American human and fossil bone. Am. J. Phys. Anthro-
pol., 10: 289-303.
Heusser, C. J. 1953. Pollen profiles from southeastern Alaska. Ecol.
Monographs, 22: 331-352.
. 1955. Pollen profiles from Prince William Sound and southeastern
Kenai Peninsula, Alaska. Ecology, 36: 185-202.
Heyerdahl, T., and A. Skjolsvold. 1956. Archaeological evidence of pre-
Spanish visits to the Galapagos Islands. Am. Antiquity, 22: 1-69.
Hibbard, C. W. 1955. Pleistocene vertebrates from the Upper Becerra.
Contrib. Museum Paleontol., Univ. Michigan, 12: 47-96.
. 1958. Summary of North American Pleistocene mammalian local
faunas. Papers Mich. Acad. Sci., 43: 3-32.
Hunt, C. B. 1953. Pleistocene-Recent boundary in the Rocky Mountain
Region. U. S. Geol. Surv. Bull., 996 A: 1-25.
Hustich, I. 1954. On forests and tree growth in the Knob Lake area,
Quebec-Labrador Peninsula. Acta Geografica, 13: 1-60.
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 417
Hutchinson, G. E., R. Patrick, and E. S. Deevey. 1956. Sediments of Lake
Patzcuaro, Michoacan, Mexico. Bull. Geol. Soc. Am., 67: 1491-1504.
Iversen, J. 1954. The late-glacial flora of Denmark and its relation to
climate and soil. Danmarks Geol. Unders^gelse, 80: 87-119.
Jennings, J. D. 1957. Danger Cave. Mem. Soc. Am. Archaeology, 14:
1-328.
Kitts, D. B. 1953. A Pleistocene musk ox from New York and the dis-
tribution of the musk-oxen. Am. Museum Novitates, 1607: 1-8.
Koopman, K. F., and E. E. Williams. 1951. Fossil Chiroptera collected
by H. E. Anthony in Jamaica, 1919-1920. Am. Museum Novitates,
1519: 1-29.
Lange, A. L. 1956. Woodchuck remains in northern Arizona caves. /.
Mammal. 37: 289-291.
Lee, T. E. 1957. The antiquity of the Sheguiandah Site. Canadian Field-
Naturalist, 71: 117-137.
Leopold, A. S. 1950. Vegetation zones of Mexico. Ecology, 31: 507-518.
Leopold, S. B. 1956. Two late-glacial deposits in southern Connecticut.
Proc. Natl. Acad. Sci. U.S., 52: 863-867.
Livingstone, D. A., and B. G. R. Livingstone. 1958. Late-glacial and
postglacial vegetation from Gillis Lake in Richmond County, Cape
Breton Island, Nova Scotia. Am. J. Sci., 256: 341-359.
MacNeish, R. S. 1950. A synopsis of the archaeological sequence in the
Sierra de Tamaulipas. Rev. mex. estudios antropoL, 11: 79-96.
■ — ■. 1955. Ancient maize in Mexico. Archaeology, 8: 108-115.
Manley, G. 1955. A climatological survey of the retreat of the Laurentide
Ice Sheet. Am. J. Sci., 253: 256-273.
Manning, T. H. 1956. Narrative of a second Defence Research Board
expedition to Banks Island. Arctic, 9: 3-77.
Marshall, J. T. 1957. Birds of Pine-Oak Woodland in Southern Arizona
and Adjacent Mexico. Pacific Coast Avifauna, 32: 1-125.
Martin, P. S. 1958a. Taiga-tundra and the Full-glacial period in Chester
County, Pennsylvania. Am. J. Sci., 256: 470-502.
. 1958b. Pleistocene biogeography of a desert mountain. Am.
Phil. Soc. Yearbook, American Philosophical Society, Philadelphia,
Pa. Pp. 240-242.
Martin, P. S., and B. E. Harrell. 1957. The Pleistocene history of tem-
perate biotas in Mexico and Eastern United States. Ecology, 38:
468-480.
Matthew, W. D. 1919. Recent discoveries of fossil vertebrates in the
West Indies and their bearing on the origin of the Antillean fauna.
Proc. Am. Phil. Soc, 58: 161-181.
Mercer, J. H. 1956. Geomorphology and glacial history of southernmost
Baffin Island. Geol. Soc. Am. Bull, 67: 553-570.
Miller, A. H. 1951. An analysis of the distribution of birds of California.
Univ. Calif. Pubis. Zool., 50: 531-644.
418 P. S. MARTIN
Miller, G. S., and R. Kellogg. 1955. List of North American Recent mam-
mals. U. S. Natl. Museum Bull, 205: 1-954.
Moreau, R. E. 1955. Ecological changes in the Palearctic region since the
Pliocene. Proc. Zool. Soc. London, 125: 253-295.
Murray, K. F. 1957. Pleistocene climate and the fauna of Burnet Cave,
New Mexico. Ecology, 38: 129-132.
Nikiforoff, C. C. 1955. Hardpan soils of the coastal plain of southern
Maryland. Geol. Surv. Prof. Paper, 267 B: 45-62.
Osborn, H. F. 1906. The causes of extinction of mammalia. Am. Natural-
ist, 40: 769-795, 829-859.
— •. 1936. Proboscidea. American Museum of Natural History, New
York.
Peltier, L. C. 1949. Pleistocene terraces of the Susquehanna River, Penn-
sylvania. Penn. Topol. Geol. Survey, ser. 4, Bull., 023: 1-158.
Potzger, J. E., and A. Courtemanche. 1956. A series of bogs across Quebec
from the St. Lawrence Valley to James Bay. Can. J. Botan., 34:
473-500.
Potzger, J. E., and B. C. Tharp. 1947. Pollen profile from a Texas bog.
Ecology, 28: 274-280.
. 1954. Pollen study of two bogs in Texas. Ecology, 35: 462-466.
Quimby, G. I. 1958. Fluted points and geochronology of the Lake Michi-
gan basin. Am. Antiquity, 23: 247-254.
Rabb, G. B., and E. B. Hayden. 1957. The Van Voast-American Museum
of Natural History Bahama Islands Expedition. Am. Museum Novi-
tates, 1836: 1-53.
Rand, A. L. 1948. Glaciation, an isolating factor in speciation. Evolution,
2: 314-321.
Rasmussen, W. C. 1953. Periglacial frost-thaw basins in New Jersey: a
discussion. /. Geol., 61: 473-474.
Romer, A. S. 1933. Pleistocene vertebrates and their bearing on the
problem of human antiquity in North America. In The American
Aborigines, Their Origin and Antiquity, D. Jenness, Editor. Univer-
sity Toronto Press, Toronto, Canada.
. 1945. Vertebrate Paleontology. University Chicago Press, Chicago,
111.
Rouse, I. 1952. The age of the Melbourne Interval. Texas Archeol.
Paleontol. Soc, 23: 293-299.
Rouse, I., and J. M. Cruxent. 1957. Further comment on the finds at El
Jobo, Venezuela. Am. Antiquity, 22: 412.
Rousseau, J. 1952. Les zones biologiques de la Peninsule Quebec-Labrador
et I'hemiarctique. Can. J. Botan., 30, 436-474.
Sauer, C. O. 1944. A geographical sketch of Early Man in America.
Geog. Rev., 34: 529-573.
Scharff, R. F. 1912. Distribution and Origin of Life in America. Mac-
millan. New York.
PLEISTOCENE ECOLOGY AND BIOGEOGRAPHY 419
Schultz, J. R. 1938. A late quaternary mammal fauna from the tar seeps
of McKittrick, California, Carnegie Inst. Wash. Publ., 487: 115-
215.
Sears, P. B., F. Foreman, and K. H. Clisby. 1955. Palynology in southern
North America. Bull. Geol. Soc. Am., 66: 471-530.
Sellards, E. H. 1952. Early Man in America. University Texas Press,
Austin.
Sharpe, C. F. S. and E. F. Dosch. 1942. Relation of soil-creep to earth-
flow in the Appalachian Plateaus. /. Geomorphol., 5: 312-324.
Sibree, J. 1915. A Naturalist in Madagascar. Seeley, Service & Co.
Simpson, G. G. 1931. Origin of mammalian faunas as illustrated by that of
Florida. Am. Naturalist, 65: 258-276.
— . 1940. Review of the mammal-bearing Tertiary of South America.
Proc. Am. Phil. Soc, 83: 649-709.
. 1945. The Principles of Classification and a Classification of
Mammals. Bull. Am. Museum Nat. Hist., 85: 1-350.
— . 1953. The Major Features of Evolution. Columbia University
Press, New York.
1956. Zoogeography of West Indian land mammals. Am. Musetim
Novitates, 1759: 1-28.
Smith, P. W. 1957. An analysis of post-Wisconsin biogeography of the
Prairie Peninsula region based on distributional phenomena among
terrestrial vertebrate populations. Ecology, 38: 205-218.
Soday, F. J. 1954. The Quad Site, a Paleo-Indian village in northern
Alabama. Tenn. Archaeologist, 10: 1-20.
Stearns, C. E. 1942. A fossil marmot from New Mexico and its climatic
significance. Am. J. Set., 240: 867-878.
Stewart, O. C. 1951. Burning and natural vegetation in the United States.
Geog. Rev., 41: 317-320.
Stuart, L. C. 1951. The herpetofauna of the Guatemalan Plateau. Con-
tribs. Lab. Vert. Biol., Univ. Mich., 49: 1-71.
Taylor, W. W. 1956. Some implications of the carbon-14 dates from a cave
in Coahuila, Mexico. Texas Archeological Soc. Bull., 27: 215-234.
Thomas, E. S. 1951. Distribution of Ohio animals. Ohio J. Sci., 51:
153-167.
Wells, B. W., and S. G. Boyce. 1953. Carolina bays: additional data on
their origin, age and history. /. Elisha Mitchell Sci. Soc, 69: 119-141.
Wetmore, A. 1937. Bird remains from cave deposits on Great Exuma
Island in the Bahamas. Bull. Museum Comp. ZooL, 60: 427-441.
. 1943. The birds of southern Veracruz, Mexico. Proc. U. S. Natl.
Museum, 93: 215-340.
-. 1956. A Check-list of the Fossil and Prehistoric Birds of North
America and the West Indies. Smithsonian Inst. Pubis., Misc. Collec-
tions, 131: 1-105.
Weyl, R. 1955. Vestigios de una glaciacion del Pleistoceno en la Cordillera
420 p. S. MARTIN
de Talamanca, Costa Rica, A. C. Informe Trimestral, Inst. Geog. de
Costa Rica, pp. 9-32.
White, S. E. 1956. Probable substages of glaciation on Iztaccihuatl,
Mexico. /. Geol., 64: 289-295.
Whittaker, R. H. 1956. Vegetation of the Great Smoky Mountains.
Ecol. Monographs, 26: 1-80.
Williams, E. E. 1950. Testudo cubensis and the evolution of western
hemisphere tortoises. Bull. Am. Museum Nat. Hist., 95: 1-36.
. 1952a. A new fossil tortoise from Mono Island, West Indies, and
a tentative arrangement of the tortoises of the world. Bull. Am.
Museum Nat. Hist., 99: 541-560.
1952b. Additional notes on fossil and subfossil bats from Jamaica.
/. Mammal, 33: 171-179.
Williams, E. E., and K. F. Koopman. 1951. A new fossil rodent from
Puerto Rico. Am. Museum Novitates, 1515: 1-9.
Williams, S. 1957. The Island 35 Mastodon. Am. Antiquity, 22: 359-372.
Wilson, L. R. 1932. The Two Creeks forest bed, Manitowoc County,
Wisconsin. Trans. Wisconsin Acad. Sci., 27: 31-46.
. 1936. Further fossil studies on the Two Creeks forest bed,
Manitowoc County, Wisconsin. Bull. Torrey Botan. Club, 63: 317-
325.
Witthoft, J. 1952. A Paleo-Indian site in Eastern Pennsylvania: an early
hunting culture. Proc. Am. Phil. Sac, 96: 464-495.
Wolfe, P. E. 1953. Periglacial frost-thaw basins in New Jersey. /. Geol.,
61: 133-141.
Wormington, H. M. 1957. Ancient Man in North America, fourth edition,
Denver Museum of Natural History, Denver, Colo.
Yehle, L. A. 1954. Soil tongues and their confusion with certain indicators
of periglacial climate. Am. J. Sci., 252: 532-546.
Zumberge, J. H., and J. E. Potzger. 1956. Late Wisconsin chronology of
the Lake Michigan Basin correlated with pollen studies. Bull. Geol.
Soc. Am., 67: 271-288.
16
The Palaearctic Element in the New World Avifauna
Kenneth C. Parkes
Carnegie Museum, Pittsburgh, Pennsylvania
In the March 1946 issue of The Wilson Bulletin,
Ernst Mayr pubHshed an important paper entitled "History of the
North American bird fauna," a review that represents a much-
quoted landmark in the study of the zoogeography of North America.
Mayr summarized the recent advances in zoogeography in general,
with particular reference, of course, to birds, and pointed out
especially the contributions of the palaeontologist and the tax-
onomist. After a brief review of the geological history of North
America, he proceeded to classify the avifaunal elements of the
Americas on the basis of probable geographic origin. He pointed
out that it is impossible to place many of the bird families as to
probable major land mass of origin. In the first place, many families,
mostly oceanic or freshwater, are now so widely distributed as to
make speculation as to their genesis fruitless. Mayr calls these the
"unanalyzed element." This group includes such sea birds as the
petrels and gulls, such freshwater birds as ducks, herons, rails,
the shore birds, and a few families of land birds, including the
diurnal birds of prey, the woodpeckers, and the swifts.
Another group of uncertain origin is also widespread but only,
at present, in the tropics. Mayr calls this the "pantropical element"
(this adjective strikes me as less awkward than "tropicopolitan,"
used by Darlington (1957) and others). This group includes aquatic
birds like the anhingas and skimmers, and a few land birds, the
trogons, barbets, and parrots. In the arctic and north temperate
zones the loons, auks, and some other birds constitute still another
group of families that is now so widely dispersed that no continent
can be named as their original source.
The strictly New World families, or rather the families of New
World origin, since some of these have found their way to the
Old World, were divided by Mayr into (1) those of probable North
421
422 K. C. PARKES
American origin, (2) those of probable South American origin, and
(3) a Pan-American element now so widespread in both continents
as to be of uncertain continental origin (see Darlington, 1957, pp.
280-286, for a critique of Mayr's theories concerning these New
World groups).
Finally, there are the families that are generally acknowledged to
be of Old World origin, but that now form a component of the
avifauna of the Americas. This is the group which will be reviewed
here.
As Mayr pointed out, birds apparently crossed the Bering Strait
connection between Asia and North America more or less con-
tinuously through most of the Tertiary. This continuity of origin
is reflected in the complete spectrum of zoogeographic and taxon-
omic status of the Old World groups in the Americas. At one end of
the spectrum are families the representatives of which arrived so
early that there has been time for a major secondary radiation in
the Americas. Such a history is exemplified by the quails, derived
from the Old World pheasant and partridge family, and by the
jays, which are much more diversified in the New World than in the
Old. It should be acknowledged that factors other than the mere
time element are involved in the extent to which these secondary
radiations have developed; evolutionary opportunity in the form
of available ecological niches and comparative rates of evolution
must also be considered. But it seems safe to assume that a group
that has reached approximately the subfamily level of difi^erentia-
tion must have derived from a rather early invasion.
At the opposite end of the spectrum Mayr mentions species
which have only a slight foothold on this continent and are insep-
arable even subspecifically from their Old World progenitors.
These include two Alaskan birds, the Yellow Wagtail {Motacilla
flava tschiitschensis) and the Red-spotted Blue-throat {Luscinia
svecica svecica), and one species, the Wheatear, which has entered
Alaska from the west (as Oenanthe oenanthe oenanthe) and the east-
em Canadian Arctic from Greenland (as 0. o. lencorhoa). All these
species are obviously recent immigrants but belong to two families
(Motacillidae and Turdidae) with wide distribution in the New
World from earlier invasions. A category even beyond this can be
established for those Old World species that do not have a foothold
PALAEARCTIC ELEMENT IX NEW WORLD AVIFAUNA 423
on this continent in the sense that there is no known breeding
population, but which occur here from time to time as so-called
accidentals or casuals. It is here we encounter some of the "unsolved
problems" appropriate to mention in a symposium with the general
title, "Some Unsolved Problems in Biology, 1957."
In discussing the so-called accidentals, particular attention will
be paid to the Transatlantic species. Fewer Transpacific crossings
can be expected for obvious geographic reasons, and a stray Asiatic
bird might easily be overlooked along the Pacific Coast of North
America, which is much less closely scrutinized by bird-watchers
than is the Atlantic Coast.
It is widely known that American birds occur in western Europe,
particularly the British Isles, far more often than European birds
appear in eastern North America. Peterson, Mountfort, and Hollom
(1954) list 41 American species or subspecies of non-pelagic, non-
introduced birds as accidental in western Europe. The American
Ornithologists' Union Check-list of North American Birds (1957),
hereafter referred to as "A.O.U. Check-list," lists 24 such species
or subspecies from Europe as accidental in eastern North America.
And even the comparative figure 41 versus 24 is misleading, since
the actual number of individual occurrences of accidental birds is
much higher in Europe than in North America. Alexander and
Fitter (1955) listed 260 authenticated records of North American
herons, cranes, rails, and waders alone in western Europe, and an
additional 126 records of land birds. The figures for European
accidentals in North America would be far fewer, particularly since a
substantial number of these are among the ducks, gulls, and other
families not included in the figures given by Alexander and Fitter.
There is no great mystery here, as the prevailing winds across the
North Atlantic are predominantly from west to east. The unsolved
problem in this case lies with the species that do manage to get
across to the western side of the Atlantic with some frequency.
Six species of palaearctic water birds occur along our Atlantic
seaboard with such regularity that a large percentage of the bird-
watchers of Long Island and New England are familiar with them,
and keep an eye out for them every year. Two are ducks, the
European Green-winged Teal {Anas crecca) and the European
Widgeon {A . penelope) ; two are sandpipers, the Curlew Sandpiper
424 K. C. PARKES
(Erolia ferruginea) and the Ruff {Philomachiis pugnax) ; and two
are gulls, the Black-headed Gull {Lams ridibundus) and the Little
Gull (L. minutus)}
What particular attribute, if any, do these six species share to
give them the propensity for such frequent Transatlantic crossings
against the prevailing winds? Three of the species, the two ducks
and the Black-headed Gull, are known to nest as far west as Iceland.
But why, then, do not other, related, Iceland nesters make the
same trip? Among the gulls, for instance, the Lesser Black-backed
Gull (Larus fuscus) breeds in Iceland, but the two specimens of
this species that have been collected in North America were both
of the British rather than the Icelandic breeding race. Of the three
remaining species, the Little Gull nests as far west as Denmark and
the coast of the North Sea, the Ruff to western France, and the
Curlew Sanrlpiper only in eastern arctic Siberia. The breeding ranges
of all these species are more or less duplicated by those of related
species or other birds of similar migration patterns. Why, then, do
we see these six so much more often along our East Coast? Several
possibilities suggest themselves. One is that other vagrant species
are being overlooked. Readers familiar with the zeal of the bird-
watching groups on Cape Cod or Long Island will discount that
one immediately. It has been said that the publication of Peterson's
Field Guide to European birds in 1954 was a real boon to many
Massachusetts bird-watchers, who had by then worn out their
Field Guides to the birds of western North America!
Another possibility is some sort of innate tendency in these few
species to go astray, so to speak; perhaps a high incidence of error
in their "direction-finding apparatus," that mysterious organ for
which ornithologists still search in vain. This would be exceedingly
difficult to demonstrate, and seems rather unlikely from an evolu-
tionary point of view, since getting lost would not appear to be a
selectively advantageous trait. A third possibility and perhaps the
most reasonable, at least for some of the species, is the existence of
undiscovered breeding areas of these species much closer than any
we know of now, perhaps even in North America itself. Certainly
1 The list of eight European birds most regularly observed on the Atlantic Coast of
North America presented by Lindroth (1957, p. 251), which overlaps the above list by
four species, was based on an obsolete and incomplete reference, the 1931 edition of the
A.O.U. Check-list. Even the 1957 edition is misleading in this respect; see Eisenmann,
1958, for remarks on the status of certain European birds in the New York City region.
PALAEARCTIC ELEMENT IN NEW WORLD AVIFAUNA 425
the unexplored tundra in the New World arctic is vast enough to
hide a small local breeding population of the Curlew Sandpiper.
It may be less likely for some of the larger species, but certainly
cannot be discounted. Every year many thousand Eastern Dowitch-
ers {Limnodrormis grisens griseiis) pass on migration along our
East Coast, but as of 1957 the A.O.U. Check-list can only say of
this large shorebird, "Breeding range uncertain, but presumed to be
in the interior of the Ungava Peninsula." Thus these so-called
accidentals may yet be shown to be an established component of
the New World avifauna.
We turn next to those Old World groups known to be established
in the Americas. Mayr listed approximately twenty families of New
World birds as being of Old World origin — approximately, since
family limits are a subject for continuing debate among ornitholo-
gists. He divided these roughly into three groups; Early, Fairly
Early, and Recent Immigrants. Two principal types of evidence
are used to classify these groups. The fossil record, of the relatively
few species for which it is at all adequate, is naturally the best
evidence, but note the warning of Darlington (1957, p. 238) : "Birds
are a good example of the fact that, in zoogeography, a poor fossil
record interpreted too literally is almost worse than no record at
all." The other type of evidence is more inferential, based on the
relative numbers of species and genera in the New and Old Worlds,
the degree to which the New World forms have differentiated
taxonomically, and the distance into the Americas they have
penetrated. Mayr's tripartite chronological division is of necessity
arbitrary and, particularly for large families, may be misleading in
suggesting a lesser number of invasions than has probably occurred.
Mayr circumvented the latter difficulty by subdividing the rep-
resentatives of some families, as the Corvidae (crows and jays)
and the Turdidae (thrushes) into older and newer invasions. Even so,
additional subdivision beyond Mayr's seems desirable. For instance,
Mayr pointed out, on the basis of both fossil and Recent taxonomic
evidence, that the typical owls, family Strigidae, though almost
certainly of Old World origin, must have reached the New World
very early. Fragmentary remains assigned to an allied but extinct
family, Protostrigidae, are known from the Eocene of Wyoming,
and a Lower Miocene species from South Dakota is identified with
the living genus Strix (this and other data on fossil birds are chiefly
426 K. C. PARKES
from Wetmore, 1956). Six endemic genera of owls are currently
recognized from the New World. On the other hand, no fewer
than eight species, in six genera, are currently considered to be
conspecific with Old World owls ; among these is a panarctic species
with no races, the Snowy Owl [Nyctea scandiaca). Another species,
the Short-eared Owl {Asio flammeus), has a highly unusual dis-
tribution. The nominate race is found, without appreciable geo-
graphic variation, throughout Europe and northern and central
Asia, and in North America through about the northern half of the
United States. There is then a distributional gap, beyond which
the species reappears (as subspecies bogotensis) in the arid temperate
zone of the mountains and plateaus of the northern Andes. Again,
beyond a gap, appears the subspecies suinda, which ranges from
southern Peru and southern Bolivia to Tierra del Fuego. There are
isolated endemic subspecies on the Falkland Islands, the Hawaiian
Islands, the Galapagos Islands, Hispaniola, Puerto Rico, and
Ponape in the Carolines. Probably few living species of birds have
had so complex a distributional history.
A good illustration of the value of the fossil record where it is
available to counteract misleading evidence based on modern
distribution is furnished by the family Gruidae, the cranes. On the
basis of the living forms only, one would probably characterize
this family as a rather recent immigrant to the New World, for
there are only two American species, one of which also occurs in
eastern Siberia and both of which belong to a widespread Old
World genus, and cranes have penetrated only as far south in the
New World as Cuba. However, the evidence of the living species is
misleading. Cranes of as many as three extinct genera are known
from the Eocene of Wyoming, and one Eocene fossil is tentatively
assigned to the living genus Grus. But lest it be thought that cranes
became extinct in North America in, perhaps, the late Tertiary,
with the two living species representing a rather recent second
invasion, it should be pointed out that fossils indistinguishable from
the living species occur as early as the Pliocene: the Whooping
Crane in the Upper Pliocene, and the Sandhill Crane in the Lower
Pliocene.
Good examples of what were undoubtedly secondary New World
radiations from an early invading Old World stock are the cuckoos,
the pigeons, and the jays. The large and diverse Old World family
PALAEARCTIC ELEMENT IN NEW WORLD AVIFAUNA 427
Cuculidae is represented in the Americas by thirty species, which
are arranged in ten genera, not a single one of which occurs in the
Old World. In the pigeon family, Columbidae, there are nineteen
endemic New World genera, some highly distinctive. The twentieth
genus, which is shared with the Old World, is the eminently success-
ful genus Coliimba, to which the domestic pigeon belongs. There are
no fewer than eighteen New World species of Columba, of which
seventeen are confined to the warm latitudes between the Rio
Grande and south Florida to the north and approximately Buenos
Aires to the south. Darlington (1957, p. 273) argued for a tropical
New World origin of the genus Columba, with dispersal to the Old
World through the north. To me, the facts suggest, rather, (1) an
origin in the Old World, (2) a secondary radiation in the New World
tropics, and (3) a quite recent northward movement by a single
species, the Band-tailed Pigeon (C. fasciata), which now ranges
from Central America to southwestern British Columbia. That
Columba was originally a tropical genus is suggested not only by
the somewhat greater number of tropical than of temperate species
in the Old World, but by the fact that the genera currently placed
closest to Columba (Peters, 1937) are also confined to the Old World
topics. This would give strength to the idea that Columba is older
in the Old World than in the New, as would the fact that a larger
number of species has been able to become adapted to temperate
conditions in the former area than in the latter.
Turning now to the family Corvidae, we may note that the
greater diversity of the jays in the New World is evidence for an
early secondary radiation from corvid stock. It is, in fact, quite con-
ceivable that the few jays of the Old World may represent a re-
invasion of the Old World. One genus of jays, Perisoreus, now
inhabits northern coniferous forests of both hemispheres, with a
distinct but related species {"Boanerges'' internigrans) in the moun-
tains of western China. Amadon (1944, p. 5) believed that the
distribution of Perisoreus leaves "little doubt that it is an Old World
genus which reached America recently, later than the other American
jays." If the jays, as postulated above, represent a reinvasion of the
Old World by corvid stock which had differentiated in the New
World, then Amadon 's interpretation would require Perisoreus to
have returned, so to speak, to the New World. This is possible,
but a New World origin for Perisoreus itself must be considered.
428 K. C. PARKES
At any rate, members of the family Corvidae other than the jays
have continued to enter the New World, some so recently that the
American populations are barely separable subspecifically from
their Old World relatives (the family thus paralleling the owls in
this respect). The Magpie {Pica pica) now exists in North America
in two well-marked forms: the Black-billed [P. p. hudsonia), very
similar to Old World races, and the Yellow-billed, usually considered
a full species (P. nuttalli). Only the latter is known from fossil
(late Pleistocene) remains in North America, from within or close
to its present range in California. The magpies of North America
may well represent a double invasion by the same Old World
species (see Lanius, beyond). Again, within this family, the genus
Corvus has entered the New World at least twice, and probably
more often. A cluster of closely related species of this genus in the
southern United States, West Indies, and Mexico probably represents
a rather early invasion, since these species at present have no clear
affinities with any Old World crows. On the other hand, the southern-
most penetration of this genus in the Americas is that of the Raven
(C. cor ax), which has reached Nicaragua. Pleistocene fossils of the
Raven are known from as far south as Nuevo Leon, Mexico, yet
all New World Ravens are only subspecifically different from those
of the Old World, and the northernmost populations are barely
separable.
The weakness of the fossil record is nowhere better demon-
strated than in the large order Passeriformes, the perching birds,
to which half our living species belong. Wetmore (1956) listed from
North America (including the West Indies) only 51 species of
passeriform birds known from fossil (for one species Recent cave)
remains. Of these 51, no fewer than 44, or 86%, are Pleistocene
fossils of living species. A single species, for which the family
Palaeospizidae has been erected, is known from the Upper Miocene
or Oligocene; one extinct genus of finch is known from the Middle
Pliocene ; two extinct genera of blackbirds are known from the late
Pleistocene, and one of these may prove to be of Recent origin;
and two extinct species of living genera are known from the late
Pleistocene. All the extinct species of living passeriform families
belong to families of New World origin. Thus we have none of the
sort of evidence quoted earlier for the cranes to show that deductions
on the basis of the living forms only may be highly misleading.
PALAEARCTIC ELEMENT IN NEW WORLD AVIFAUNA 429
Evidence from other than fossil sources can, of course, be so over-
whelming as to be tantamount to proof of origin of some of these
passeriform families. The larks (Alaudidae), for instance, comprise
a diverse and widespread Old World family, which extends from the
arctic to the tropics. It is represented in the New World by a single
species, the Horned Lark {Eremophila alpestris), which, although it
has penetrated the Americas as far as the vicinity of Bogota,
Colombia, remains no more than subspecifically different from the
palaearctic forms.
The distributional history of other passeriform families in the
New World is far more obscure. The waxwings (Bombycillidae)
are a good example. Mayr, following Lonnberg, listed this family
without comment as being of North American origin. The evidence
from the three living species is anything but unequivocal. One
species {Bombycilla garrulus) is distributed across the northern
Palaearctic, from Scandinavia to Siberia, and also in northwestern
North America, and breeds about as far southeast into the continent
as Glacier Park, Montana. Another species, the Cedar Waxwing
{B. cedrorum), is found virtually throughout North America, from
southern Alaska and Newfoundland south to the upper southern
states. The third species {B. japonica) breeds only in a relatively
small area of eastern Siberia in the Amur River basin. There is
little here upon which to base conclusions as to origin, but I would
say that the balance might be tipped in favor of the Old World.
The next step would be to examine the families considered most
closely related to the waxwings. Their nearest allies appear to be
two other American groups which are, by some "lumpers," even
placed as subfamilies of the Bombycillidae. These are the Ptilo-
gonatidae of the southwestern United States and Central America,
and the Dulidae, a monotypic family known only from Hispaniola.
This would seem to argue for an American origin for the \\ax\\ ings.
On the other hand, recent investigations indicate that the odd
genus Hypocoliiis from the Persian Gulf region is closely related to
the waxwings. Such are the difficulties encountered in trying to
work out a distributional history for a small family of birds with no
significant fossil record and of uncertain near relationships.
One of the most plausible indications of double invasion of the
New W^orld by a palaearctic stock is furnished by the shrikes
(Laniidae). It seems clear that the two North American species
430 K. C. PARKES
have been derived from two incursions of the same stock. The de-
tails of these invasions may be inferred to have been as follows.
The first immigration took place prior to the Pleistocene glaciation
by birds belonging to the widespread Old World species that we now
call Laniiis excubitor. With the advent of glaciation this species
moved south. It is highly adaptable, as shown by its Old World
range, which extends from northern Scandinavia to India and
Arabia. Therefore, with the retreat of the glacier, populations of
this shrike were able to remain as far south as southern Mexico,
while northern populations reoccupied an area extending to central
Canada. At some uncertain time the species again crossed the
Bering Strait and quickly spread through the boreal portion of
North America. This second wave is currently regarded as con-
specific with and closely related to the Old World races through
the Siberian population, while the descendants of the first invasion
are given specific rank (L. liidovicianus) . Certain well-marked
differences that have evolved in these earlier and more southern
populations are invoked as specific characters. However, members
of this so-called species, the Loggerhead Shrike, resemble some of
the ecologically parallel populations of the Old World species
(Olivier, 1944, p. 43), Judging from published maps and range
descriptions, the Northern and Loggerhead shrikes nowhere come
into actual contact during the breeding season in North America.
There is thus no available natural testing site for the criterion
of reproductive isolation. We have here an interesting problem of
deciding what to call the two North American shrikes; although
they have almost always been listed as full species, there are argu-
ments and precedents for the opposite view. The problem they
illustrate is an interesting, although perhaps uncommon one:
the question of the taxonomic treatment of obvious derivatives,
from two well-separated invasions of the same stock, that are now
separated spatially, so that no evidence as to reproductive iso-
lation is forthcoming.
Perhaps the most intriguing problem connected with the palae-
arctic element in the New World avifauna, and the one least likely
to be solved, deals with the related questions "which?" and "why?"
— which groups made the trip, and why these and not others?
Undoubtedly the most striking aspect of this problem is the apparent
one-way traffic between the two continents; Darlington (1957,
PALAEARCTIC ELEMENT IN NEW WORLD AVIFAUNA 431
p. 279) reminded us that this pattern is also true of mammals and of
cold-blooded vertebrates. Lindroth (1957) listed twenty-four
species of passeriform birds as occurring in both Eurasia and North
America. After deducting the swallows and the waxwing, of uncertain
origin, and two species no longer considered conspecific with their
overseas counterparts {Pants atricapillus with P. borealis; Sitta
canadensis with S. corea, kruperi, villosa, and whiteheadi), we are
left with nineteen species in common. Of these, no fewer than
sixteen, of nine families, are regarded as of Old World origin and as
invaders of the New World, while only three species, of two families,
are treated as immigrants from the opposite direction. Two of
these species, the Lapland Longspur (Calcarius lapponicus) and the
Snow Bunting {Plectrophenax nivalis), are panarctic birds that have
developed a few weakly characterized subspecies. The third species,
on the contrary, is the highly polytypic wren Troglodytes troglodytes.
The A.O.U. Check-list (1957), which probably oversplits them,
recognizes no fewer than twelve North American races, while the
situation in Eurasia may be judged by Vaurie's recent paper (1955),
in which he reduced to eight a total of twenty-one proposed races
from eastern Asia alone. The question, of course, is why} Why has
this single passeriform species been so obviously successful? Why
was it one of the very few that has been able to "swim against the
tide," and what caused the "tide" in the first place? Why are the
palaearctic-derived siskins, pipits, and thrushes found all through
South i\merica in suitable habitats, whereas only a single group
of New World passeriform birds, the emberizine finches, has radiated
at all in the Old World? Such are the unsolved problems of this
corner of zoogeography, and most are likely to remain chiefly
intellectual exercises, since the likelihood of securing tangible
evidence with which to solve them appears small.
REFERENCES
Alexander, W. B., and R. S. R. Fitter. 1955. American land birds in west-
ern Europe. British Birds, 48: 1-14.
Amadon, Dean. 1944. The genera of Corvidae and their relationships.
Am. Museum Novitates, No. 1251: 1-21.
American Ornithologists' Union. 1957. Check-list of North American
Birds, 5th edition. Published by the Union.
Darlington, Philip J., Jr. 1957. Zoogeography. John Wiley & Sons, New
York.
432 K. C. PARKES
Eisenmann, Eugene. 1958. The new A.O.U. Check-list. Linnaean News-
letter (Linnaean Society of New York), 11, No. 7-8: [1-3].
Lindroth, Carl H. 1957. The Faunal Connections between Europe and North
America. John Wiley & Sons, New York.
Mayr, Ernst. 1946. History of the North American bird fauna. Wilson
Bull. 58: 1-41.
Olivier, Georges. 1944. Monographie des Pies-Grieches du genre Lanius.
Lecerf, Rouen.
Peters, James L. 1937. Check-List of Birds of the World, Vol. 3. Harvard
University Press, Cambridge, Mass.
Peterson, R. T., Guy Mountfort, and P. A. D. Hollom. 1954. A Field
Guide to the Birds of Britain and Europe. Houghton, Mifflin, Boston,
Mass.
Vaurie, Charles. 1955. Systematic notes on palearctic birds. No. 16.
Troglodytinae, Cinclidae, and Prunellidae. Am. Museum Novitates,
No. 1751: 1-25.
Wetmore, Alexander. 1956. A check-list of the fossil and prehistoric
birds of North America and the West Indies. Smithsonian Misc.
Collections, 131, No. 5.
Distributional Patterns of Vertebrates in the
Southern United States in Relation to
Past and Present Environments
W, Frank Blair
Department of Zoology, The University of Texas,
A iistin
1 he thesis of this discussion is that the present
distributions of vertebrates in the southern United States, on the
Gulf and Atlantic coastal plains in particular, can be explained only
on the hypothesis of drastic ecological changes in the deep south in
the Pleistocene. The germ of this concept was stated by Adams
(1902). More recently, Deevey (1949) expressed the hypothesis
clearly and reviewed some of the supporting evidence in his general
discussion of Pleistocene biogeography. The argument is essentially
that at peaks of glacial advance into the northern United States
climatic and ecological changes in the southern United States were
so great as to drive warmth-adapted species into separate refuges in
Florida and Mexico. Blair (1951) referred to additional evidence
from the vertebrates.
Braun (1955 and other papers) has been particularly vigorous in
opposition to this hypothesis and has argued that the conditions
that produced the Pleistocene glaciations had little effect in the
southern United States.
I now reopen the question, reviewing some of the evidence cited
by previous workers and introducing additional material. The evi-
dence is concerned primarily with past and present distributions of
tetrapod vertebrates, other than birds. One item in the past distribu-
tion of fishes is cited, but the present distribution of this group is
excluded from consideration. Similarly, no treatment of birds is
attempted, because of the author's relative unfamiliarity with this
group.
The area to which the discussion will be largely limited is the Gulf
433
434 W. F. BLAIR
coastal plain and the bordering grasslands to the west, although the
argument applies equally to other species in eastern North America
not today limited to the coastal plain. Two major biotic formations
are involved. The Austroriparian forest extends with only minor
variance in climate, ecological dominants, and general aspect from
eastern Texas to the Atlantic coast. The southern grasslands border
the forest of the west. These grasslands, with beginnings in the late
Miocene and great development in the Pliocene (Clements and
Chaney, 1937) stand today as a barrier to the westward distribution
of many forest animals.
I consider three major questions:
1. What is the evidence in regard to Pleistocene climates in the
southern United States? Were the climatic changes sufficiently
drastic as to force the withdrawal of warmth-adapted coastal plain
animals into separate eastern (Floridian) and western (Mexican)
refuges?
2. How effective were the grasslands as a Pleistocene barrier to
the southwestward withdrawal of warmth-adapted species into
Mexico?
3. How do present distributions fit the hypothesized Pleistocene
climatic changes?
SOUTHERN CLIMATES IN THE PLEISTOCENE
Evidence from various sources indicates major ecological changes
on the coastal plain in the Pleistocene, including far southward
shifting of northern plants and animals during stages of glaciation
in the north. Climatic implications from these shifts must rest on
the assumption that ecological requirements of living species and
genera do not differ significantly from those of their Pleistocene
progenitors. When single taxa are involved, this assumption some-
times may be of doubtful validity. When whole faunal or floral
assemblages are represented, little or no basis seems to remain for
questioning its validity.
Plant Fossils
Most of the scanty but highly significant evidence from plant
fossils has been reviewed by Deevey (1949, 1950). On the western
coastal plain, spruce {Picea) and fir {Abies) pollens have been found
at the base of bog deposits in Lee, Milam, and Robertson counties.
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 435
Texas (Potzger and Tharp, 1947, 1954). The determination that
spruce and fir pollens total 11% of the pollen in the lowermost foot
level in the Gause bog in Milam County was interpreted by the
authors as "adding to the accumulating evidence of a widespread
cool-moist climate, and migration of boreal genera far to the south
of the actual borders of the continental ice caps." On the eastern
coastal plain, Frey (1951) reported spruce and hemlock (Tsuga)
pollens from a profile from Singletary Lake, North Carolina, and
found a pine-spruce maximum at a zone of approximately 10,000
years age, determined by radiocarbon dating. Below this zone an
amelioration of climate is indicated, and above it successive changes
to warm, moist and to warm, dry are indicated. Spruce and fir
pollens have been reported from northern Florida, in Pleistocene
peats hypothesized as of late Wisconsin age (Davis, 1946).
Pleistocene macrofossils of northern types have been recorded
from a few southern localities. Larch (Larix) has been reported
from northern Georgia (Berry, 1907). Remains of larch, spruce,
and arbor vitae (Thuja) have been found along Little Bayou Sara in
southern Louisiana (Brown, 1938). Braun (1955) attempted to
rationalize these southern records of northern plants with her argu-
ment against general displacement southward of climatic zones in
the Pleistocene. The hypothesis that frost pockets existed near the
coast and that cold, foggy climates prevailed there was suggested as
the explanation of the past occurrence of northern species on the
southern Atlantic coastal plain. She further suggested that ecologi-
cal requirements of the northern indicator species may have been
at one extreme of the tolerance range as manifested today. On the
contrary, the past occurrence of species that now live in the region
of the Little Bayou Sara deposits with the northern invaders can
more plausibly be explained by the assumption that they then
existed there at the limits of their cold tolerance, rather than that
the northern species were there with them because of their own
warmth tolerance. It seems quite unreasonable to attribute the
appearance of the presently cold-adapted species near the present
Gulf shores to any circumstance other than climatic change, and it
seems only reasonable on Dr. Braun 's own argument to attribute
their coexistence with present warmth-adapted species to the ability
of the latter to exist under conditions bordering the limits of their
cold tolerance.
436 W. F. BLAIR
Vertebrate Fossils
Pleistocene fossils from the coastal plain itself are few, except in
Florida, which is postulated as a glacial-stage refuge. Records from
other areas, however, are strongly indicative of major southward
shifts of climatic zones. The evidence comes from individual species
with northern distributions today and from relatively large faunal
assemblages with similar distributions.
Southernmost records of the Pleistocene muskox Symbos (Hay,
1923, 1924) lie far south of the present distribution of the living
genus Ovibos (Fig. 1). These records show that this muskox ranged
at least as far south as LeFlore County, Oklahoma, and Natchez,
Mississippi. If it is assumed that Symbos even approached Ovibos in
its ecological requirements, and it is plausible to do so, these records
indicate much colder conditions than those of the present. The
Oklahoma and Mississippi records are far south of the glacial border
at the time of maximum advances.
The walrus (Odobenus) is known from several Pleistocene fossils
collected in the vicinity of Charleston, South Carolina (Hay, 1923),
but in historic times it has occurred only as far south as Maine
(Allen, 1930).
The moose (Alces) is known from the Pleistocene as far south as
Charleston, South Carolina, and Bigbone Lick, Kentucky (Hay,
1923), but within historic times has occurred only as far south as
northern New York (Miller and Kellogg, 1955).
Among small mammals, a shrew (Sorex cinereus) is known from
several Pleistocene localities far south of its present range (Fig. 2).
The southernmost of these is the San Josecito cave in southern
Nuevo Leon (Findley, 1953). This species is also listed in the Conard
Fissure fauna of northwestern Arkansas (Hay, 1924), and Hibbard
(1949) reported it from the Cudahy fauna, regarded as Kansan in
age, and from the Jones Ranch fauna, regarded as late Wisconsin,
of southwestern Kansas.
The marmot (Marmota) likewise lived south of its present southern
limits during parts of the Pleistocene. The southernmost record is
from San Josecito cave in southern Nuevo Leon (Cushing, 1945).
This rodent has also been recorded from Pleistocene cave deposits in
southern Arizona and New Mexico (Skinner, 1942; Stearns, 1942;
Murray, 1957). The present southern limit of Marmota fiaviventris
is in northern New Mexico, at elevations above 11,000 feet.
DISTRIBUTIONAL PATTERNS OF VERTEBRATES
437
'TO l«0 140 100 eO 40 30
Fig. 1. Present distribution of the muskox, Ovibos (shaded) and
southernmost records of the Pleistocene muskox, Symbos.
438 W. F. BLAIR
The climatic implications of the bog lemming {Synaptomys cooperi)
in the San Josecito cave fauna (Gushing, 1945) have been discussed
by Hibbard (1955a). The present southern limits of this species are
in northeastern Kansas, except for relictual populations in small
bogs in southwestern Kansas.
The most complete picture of the southward shift of northern
faunas comes from the work of Hibbard in southwestern Kansas and
northwestern Oklahoma. Four cool faunas are recognized and ten-
tatively identified with the four major glaciations of the Pleistocene
(Hibbard, 1953). Two warm faunas are attributed to the Second
and Third Interglacials, and only the First Interglacial is unrepre-
sented. Mammalian components of several of these faunas are listed
by Hibbard (1949). The Cudahy fauna, regarded as representing the
closing phase of a Glacial age (Kansan), has the following small
mammals of northern afifinity:
Sorex cinereus, present distribution (Fig. 2).
Sorex cudahyensis, extinct.
Sorex (Neosorex) lacustris, extinct; most closely related species
today mostly in Ganada, south in Rocky Mountains to northern
New Mexico.
Microsorex pratensis, extinct; most closely related species today
mostly in Ganada and Alaska, south to northern Iowa.
Synaptomys borealis, now north of Ganadian border.
Microtus paraoperarius, extinct ; related species operarius now in
northwestern Ganada and Alaska.
Microtus llanensis, extinct.
Pitymys meadensis, extinct.
Phenacomys sp., genus now mostly in Ganada, but south in Rocky
Mountains to northern New Mexico.
The assemblage contains a few cricetine rodents and a few species
of little climatic significance. The great preponderance of microtine
rodents and shrews, however, leaves no doubt that there was a shift
of a boreal fauna at least as far southward as southwestern Kansas.
There is no reason to assume that Hibbard 's work in this area was
done at the periphery of the range of this northern fauna, but the
evidence has yet to be accumulated to show how much farther south
it extended.
The Jones fauna (Hibbard, 1949), regarded as late Wisconsin in
age, includes the northern species Sorex cinereus, Citellus richardsoni,
DISTRIBUTIONAL PATTERNS OF VERTEBRATES
439
Fig. 2. Present distribution of the masked shrew, Sorex cinereus,
(stippled) and Pleistocene records of this species (dots).
440 W. F. BLAIR
and Microtus pennsylvanicus , along with various species and genera
that occur in southwestern Kansas today and some highly euryther-
mal forms.
Another fauna from the same general area is of extreme interest
because it includes a number of fishes (Smith, 1954). This fauna,
from Beaver County, Oklahoma, is regarded as Illinoian in age.
Along with species of presently wide distribution, it includes such
northern species as the muskellunge {Esox miisquinongy) and yellow
perch {Perca flavescens) , both of which have southern limits today
several hundred miles to the northeast. Spruce, fir, and pine pollens
were found in the deposits from which the fossils were taken. Mam-
mals listed in this fauna include the northern species Sorex cinereus
and Microtus pennsylvanicus and a few types that occur in the
region today.
Other faunas from this same region are regarded as Interglacial,
and are dominated by mammals of generally southern affinities
(Hibbard, 1949, 1955b). When considered along with the cool-
climate faunas, they indicate recurrent major climatic shifts in
the region.
The Conard Fissure fauna of northwestern Arkansas (described
by Barnum Brown and listed by Hay (1924), who regarded it as
possibly Illinoian in age) includes a number of mammals that occur
today considerably farther north, or have their closest relatives
there. These are: the red squirrel {Sciurus hudsonicus), which now
ranges south to southern Iowa; the porcupine {Erethizon dorsatum),
which now ranges south to central Wisconsin in the central states,
but is widely distributed in mountains of the west; the snowshoe
hare {Lepus americanus), which now reaches a present southern
limit in the central United States similar to that of the porcupine;
the masked shrew {Sorex cinereus) and the pigmy shrew {Micro-
sorex), which now range south to northern Iowa; the fisher (Martes
pennanti) , which now occurs north of the Great Lakes ; and the least
weasel (Mustela erminea), which now ranges south to southern
Nebraska. The extinct muskox (Symbos) is also represented.
Another cave fauna from much farther south includes a similar
representation of cold-adapted mammals. This is the Burnet Cave
fauna of the Guadalupe Mountains, New Mexico. As listed by Mur-
ray (1957) this assemblage includes various species that occur in the
region today and several of presently more northern distribution.
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 441
The latter are: the hoary marmot {Marmota flaviventris) , a microtine
{Microtiis longicaudus), the hoary packrat {Neotoma cinerea), the
white-tailed jackrabbit {Lepus townseudi), and the red fox (Vidpes
fulva). These species are associated today with yellow pine and
spruce-fir forests and with the exception of the microtine reach
their southern limits about 250 miles to the north at high elevations
in the mountains. An extinct caribou-like species, Rangifer fricki,
and an extinct bovid, Eiiceratheriimi collinum, of debated ecological
significance, are also listed.
As listed by Sherman (1952), the Pleistocene mammalian fauna of
Florida, which is commonly regarded as a refuge for warmth-re-
quiring species during the glacial stages, contains virtually no mam-
mals of boreal affinity. Possible exceptions are an elk (Cerviis sp.)
and a bog lemming {Synaptomys australis). The latter, however, is
associated with a presumably Sangamon (Third Interglacial) fauna
in Kansas (Hibbard, 1955b).
The evidence from plant fossils on the coastal plain, from pollen
profiles that show spruce, fir, and other northern species of plants as
far south as southeastern Texas and northern Florida, and from the
numerous Pleistocene occurrences of vertebrates and vertebrate
faunas far south of their present distributions, leads to the conclu-
sion that there were great ecological changes in the southern United
States in the Pleistocene. It is the thesis of the present discussion
that these changes, particularly those accompanying the glacial
stages, were sufficiently drastic to fragment the ranges of warmth-
adapted coastal plain species and to force their southeastward and
south westward withdrawal, respectively into Florida and Mexico.
EFFECTIVENESS OF THE GRASSLANDS BARRIER
It has been argued that the southern grasslands have existed as a
barrier to the interchange of forest biota between the eastern United
States and Mexico since the development of the grasslands under in-
creasing aridity in the Pliocene. Separation since pre- Pliocene times
and slow rates of evolution are explanations given for the strong
floral resemblance between the humid forests along the escarpment
of the Mexican Plateau and the eastern forests (Braun, 1955).
Martin and Harrell (1957) discussed this theory in the light of some
vertebrate distributions and suggested that "few temperate-forest
animals were able to cross the arid Texas barrier in the Pleistocene.
442 W. F. BLAIR
They probably did so along a cool savanna or open woodland
corridor."
The question of past conditions in the area occupied by the south-
ern grasslands is highly germane to the problem of Pleistocene dis-
junctions in the southern United States. Most of the evidence
pertinent to this problem has never been summarized. It involves
Pleistocene fossils and present relictual distributions. The specific
question is one of how permanent has been the arid grassland
barrier.
Invasion from South America
Several South American groups of mammals crossed the supposed
grassland barrier and the coastal plain in the Pleistocene. Their
arrival in North America must have followed the development of
the Central American land bridge in the late Pliocene and early
Pleistocene, and their dispersal around the Gulf of Mexico and east-
ward across the coastal plain must have occurred after the develop-
ment of the presumed grassland barrier. The known Pleistocene
faunas of Florida include several representatives of this element,
including: the common porcupine (Erethizon dorsatum), capybaras
(two genera, Hydrochoerus and Neochoeriis), glyptodonts {Boreo-
stracon), armadillos {Daspyus, Holmesina), and ground sloths
{Megatherium, Megalonyx, Paraniylodon, Thinobadistes) , as listed by
Sherman (1952). Of these, the porcupine and ground sloths must
have required trees for their dispersal, and others, the capybaras, at
least, would have required much greater moisture than is available
at present in the southern grasslands.
Fossil Evidence of Interglacial Conditions
Various Pleistocene fossils from the region of the present grass-
lands represent groups that probably could not exist there under
present conditions and that probably required greater moisture or
forest. One of the most striking of these is the water rat (Neofiber).
At present this rodent is limited to bog situations in peninsular
Florida (Fig. 3). In what was probably the Third Interglacial
(Sangamon) this water rat occurred in the Texas panhandle and in
central Kansas (Meade, 1952; Hibbard, 1943). This rodent is also
known from the Pleistocene of Pennsylvania (Hibbard, 1955c),
where it presumably lived during an Interglacial interval. Another
DISTRIBUTIONAL PATTERNS OF VERTEBRATES
443
444 W. F. BLAIR
significant distribution is that of an extinct bog lemming {Synap-
tomys australis), which is known from the Pleistocene of Florida
(Sherman, 1952) and from the Jinglebob fauna (Sangamon) of
southwestern Kansas (Hibbard, 1955b).
Ground sloths, which presumably depended on trees for browsing,
have been recorded from various localities in the present grasslands.
Paramylodon is known from the Jinglebob (Sangamon) fauna of
southwestern Kansas, where its fossils are associated with pine
(Pinus) and Osage orange (Madura) pollens (Hibbard, 1955b). This
sloth is also known from various localities in Colorado, Nebraska,
and Texas in the area of the present grasslands, and Nothrotheriiim
is known from such presently arid grasslands as the Big Bend region
and panhandle of Texas (Hay, 1924).
Tapirs {Tapir us) are even more indicative of forests than ground
sloths. These have been recorded from the present grasslands in
north central Oklahoma and as far west as El Paso, Texas (Hay,
1924) and southwestern Oklahoma (Hibbard, 1957). A mandible in
the Centennial Museum, Texas Western College, from a cave in the
Hueco Mountains, Texas, is not permineralized and possibly repre-
sents a late occurrence of the tapir in this presently arid and treeless
region (W. S. Strain, oral communication).
The preceding evidence implies that vastly different conditions pre-
vailed at times during the Pleistocene, where grasslands exist today.
It seems reasonable to hypothesize that under the vast shifts of
climatic regimes that characterized the Pleistocene a wide spectrum
of conditions from moist to arid might be expected to have existed
in the present grasslands in various combinations with temperature
conditions.
Relations of the Floridian Vertebrates
The present Floridian fauna includes various animals that have
been there for a long time, including some that have their nearest
living relatives in eastern Asia, but this circumstance is not perti-
nent to the present discussion except as it indicates the long-con-
tinued existence in the Southeast of a faunal center of distribution
and dispersal. The Floridian fauna also includes a considerable ele-
ment of species that belong to groups with centers of distribution in
the Southwest, where they are generally adapted to more xeric
conditions than exist today on the coastal plain. The presence of
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 445
this western element in Florida suggests past climatic fluctuations
on the coastal plain that favored eastward spread. This element
includes: Scaphiopus holbrooki, Bufo woodhousei, Microhyla caro-
linensis, Sceloporiis undidatus, Cnemidophorus sexlineatus, Crotalus
adamanteus, Speotyto cimicularia, Aphelocoma coerulescens, Pero-
myscus polionotus, P. gossypinns, Reithrodontomys humulis, R.
fulvescens, Geoniys pinetis, and Neotoma Jloridana. Some of these
(e.g., Microhyla carolinensis and Peromyscus gossypinus) have
become adapted to high-moisture situations of the coastal plain.
Others have tended to retain their xeric adaptations and exist today
in the most xeric situations available. The most extreme examples
of the latter group include Scaphiopus, Cnemidophorus, Aphelocoma,
and Peromyscus poliojiotus.
Relictual Distributions in the Southern Grasslands
Present relictual occurrences of forest plants and animals argue
against the past stability of the grasslands. The isolated populations
are reasonably assumed to be remnants of the widespread popula-
tions of post-Wisconsin time and indicate greater, or at least more
effective, moisture in the not distant past than prevails in the grass-
land today. The sugar maple group {Acer saccharum and others) is
an important example because it is representative of a group with
Mexican disjuncts that was regarded by Braun (1955) as having
been separated since pre-Pliocene times. Martin and Harrell (1957)
showed the occurrences of Acer skulchii in Mexico and Guatemala
and the general distribution of the saccharum group in the eastern
United States, but they overlooked a highly' significant group of
relictual populations in Texas and western Oklahoma, These are
shown in Fig. 4 along with an approximation of the western limits
of this group in the eastern forest and the approximate eastern limits
of the representative of this group (A . grandidentatum) in the south-
ern Rocky Mountain chain. In Oklahoma, these relicts occur in the
Wichita Mountains in the southwestern part of the state and in
Caddo Canyon, Caddo County. In Texas, there are relict popula-
tions along the southern escarpment of the Edwards Plateau (Sar-
gent, 1922). Sugar maples (identified as A. grandidentatum) occur in
moist ravines in the higher mountains of trans- Pecos Texas (Sargent,
1922, and author's observations). It does not seem possible that the
Oklahoma and Texas populations are relicts of a pre-Pliocene dis-
446
W. F. BLAIR
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DISTRIBUTIONAL PATTERNS OF VERTEBRATES 447
tribution. They are taken, instead, to indicate a Wisconsin or
post-Wisconsin distribution that could have connected the Mexican
and eastern populations of sugar maples.
The bald cypress {Taxodium distichum) occurs as far west in
Texas as the Devil's River (Sargent, 1922). Isolated palmetto
(Sabal minor) plants are found on the Edwards Plateau west of
Austin, Texas. One of these was found on the floodplain of Bear
Creek, Hays County, when we went to in\'estigate the locality at
which an isolated specimen of Microhyla carolinensis had been
collected far west of the continuous range of this eastern species of
frog. The loblolly pine {Pinus taeda) grows on sandy soil over an
extensive disjunct area in Bastrop County, Texas. A disjunct
population of the greenfrog {Rana clamitans) lives along Alum Creek
in this same area. A western montane species, the pinon pine {Pinus
ediilis) has disjunct growths as far eastward as Kerr County on the
Edwards Plateau.
The piiion mouse {Peromyscus nasutus), which is distributed in
the pinon belt and above in the southern Rocky Mountain chain,
is represented by a disjunct sibling species {P. comanche) in the
cedar {Jiiniperus) forests of the Palo Duro Canyon and other
canyons along the escarpment of the High Plains in the Texas pan-
handle. The two are separated today by more than 100 miles of arid
grassland (Blair, 1943). The brush mouse {Peromyscus boylei),
which is associated with montane forests in the west, has relictual
populations (Fig. 5) much farther east than the preceding species.
The most eastern of these is in the Ozarks and Ouachita Mountains
of Oklahoma, Arkansas, and Missouri and is so little differentiated
that it has been treated as the same subspecies as in western Texas,
An eastern forest species that shows relictual populations deep
into the present grasslands is the pine vole {Pitymys pinetorum)
which has a close relative {P. quasialer) in eastern Mexico. The map
of the distribution of these voles drawn by Martin and Harrell
(1957) gives an erroneous impression of the relation of the eastern
species to the grasslands, because the range of this species is drawn
to include these relicts. Actually (Fig. 6), the westward distribution
of the main body of the population of this species ends at or inside
the border of the eastern forest in eastern Texas and Oklahoma. The
relictual populations near Kerrville on the Edwards Plateau of Texas
(Bryant, 1941) and in the Wichita Mountains, Oklahoma (Blair,
448
W. F. BLAIR
DISTRIBUTIONAL PATTERNS OF VERTEBRATES
449
Fig. 6. Present distribution of pine voles, Pitymys: P. parvulus in
southeast; P. pinetorum in eastern United States, with reUcts in Texas
and Oklahoma; and relict P. qiiasiater in Mexico.
450 W. F. BLAIR
1939) live about 200 miles farther west. This species is closely asso-
ciated with forests throughout its range, and the relicts in Texas
and Oklahoma as well as the Mexican relicts must have reached
their present locations by way of forests.
The neotenic salamanders of the genus Eurycea on the Edwards
Plateau of Texas appear to be closely related to similarly adapted
E. tynerensis of the Ozarks and thus indicate a southward as well as
westward shift of conditions favorable for this group. The two groups
are separated today by a distance of over 400 miles. In both areas,
these salamanders are restricted to cool springs in forested regions.
Another plethodontid genus (Plethodon) shows an interesting but
more complex pattern of relictual distribution (Fig. 7). A population
of P. glutinosus on the Edwards Plateau is disjunct from the main
distribution of this eastern species, which reaches into eastern Texas.
On the Edwards Plateau this species is found in relatively moist
ravines and around springs or entrances to caves. Plethodon ouachitae
of Rich Mountain in southwestern Arkansas appears to be a relict
of an Appalachian group (Dunn and Heinze, 1933). x'\nother species
of this genus (P. neomexicanus) occurs in spruce-fir forests of the
Jemez Mountains of northern New Mexico (Stebbins and Riemer,
1950). This species is described as "close to Plethodon cinereus of
eastern United States and Canada." There are disjunct populations
of P. cinereus in the Ozarks and in eastern Missouri, but the main
body of the population is east of the Mississippi River. Stebbins
and Riemer surmised that southward dispersal through the Rocky
Mountains accounted for the New Mexico population, but dispersal
directly across Oklahoma in the Wisconsin seems a more plausible
explanation. The genus occurs along the Pacific Coast from northern
California to British Columbia, and there is a relict species in north-
ern Idaho. Another plethodontid genus with wide disjunctions is
Amides. One species lives in the Appalachian region of the eastern
United States, one in the Sacramento Mountains of southern New
Mexico, and three along the Pacific Coast. Lowe (1950) hypothesizes
geographical separation of the New Mexico species {A . hardyi) dur-
ing early Pliocene. We suggest alternatively that a connection
between it and the eastern population could have existed as re-
cently as the late Pleistocene.
An area on the floodplain of the San Marcos River in Gonzales
County, Texas, has an assemblage of eastern coastal plain plants
DISTRIBUTIONAL PATTERNS OF VERTEBRATES
451
452 W. F. BLAIR
and animals that are disjunct from their main populations. The
palmetto {Sabal minor), burr oak {Quercus macrocarpa) , wax myrtle
(Myrica cerifera) and ash {Fraxinus) are representative of a rather
large number of plants in this category. The vertebrates include
the canebrake rattlesnake {Crotaliis horridus), banded watersnake
(Natrix sipedon), and narrow-mouth frog (Microhyla carolmensis) .
PRESENT PATTERNS OF DISTRIBUTION
The vertebrate groups of the coastal plain under consideration are
characterized with few exceptions by a relative scarcity of closely
related sympatric species and by a rather large number of allopatric
species or populations that show evidence of relatively recent dis-
junction. Among the 40 genera of mammals, only seven include
species that are sympatric on the coastal plain. The best represented
genus is Peromyscus, with five species that represent three subgenera.
The lizard fauna is sparse, with only eight genera, of which three,
Sceloperus, Eumeces, and Ophisaiirus, include species that are
sympatric there. On the coastal plain, there are 25 genera of snakes
of which nine there include sympatric species, with the largest
representation in the genus Natrix. Four of the 13 genera of turtles
include species that are sympatric on the coastal plain. Five of the
seven genera of anurans include species that are sympatric on the
coastal plain, but only Ra?ia and Ilyla, which have their United
States center of distribution on the plain, include several species
that are broadly sympatric there. Six of the 12 genera of urodeles
include species that are sympatric on the coastal plain.
If the urodeles are excluded from the tabulation the some 40
cases of allopatry, secondary interbreeding, or narrow sympatry
indicative of past separation into east and west populations out-
number the cases indicative of north-south disjunction in a ratio of
more than seven to one. These east-west disjunctions follow a few
general patterns. One pattern involves present limitation of the
disjunct populations to forests. One example is that of Pitymys
(Fig. 6), which was mentioned earlier. Another example is furnished
by the flying squirrel (Glaucomys volans), which ranges west to the
border of the eastern deciduous forest and has a disjunct subspecies
in the mountains from Chihuahua to Honduras (Martin and Harrell,
1957). The opossum {Didelphis marsupialis) shows evidence of
secondary interbreeding of previously disjunct populations in
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 453
southern Texas (Blair, 1952). Peromyscus gossypinus of the coastal
l^lain and P. leucopiis overlap in a generally narrow zone along the
border of the coastal plain and along the deciduous forest border in
eastern Texas and Oklahoma (Osgood. 1909; McCarley, 1954). The
present distribution of this species pair can be explained as a result
of the westward and northward spread of the coastal-plain-adapted
gossypinus from a refuge in Florida and the northward and eastward
spread of leucopus from a Mexican refuge, where it would have been
adapted to less mesic upland forests. The remarkable call "races"
of the gray treefrog {Hyla versicolor) described by Blair (1958)
imply the splitting of this species into three populations along north-
south axes, with subsequent spread to bring about the present
relationships.
Other examples of forest-restricted isolates, discussed by Martin
and Harrell (1957), include: (1) the red-bellied snake {Storeria
occipitomaculata) , which is widely distributed in the eastern forest
with relicts in the central grasslands and in Mexico, (2) the yellow-
lipped snakes, which comprise Rhadinea flavilata to the east on the
coastal plain and a closely related species, R. laureata, disjunct in
Mexico, and (3) the barred owl (Strix varia), which has a Mexican-
Central American disjunct.
The largest group providing evidence of past or present disjunc-
tion into eastern and western populations is the one in which the
eastern population inhabits forests and the western population is
adapted to, or tolerant of, grasslands. The members of some of
these species pairs meet or approach at or near the forest boundary
in eastern Texas and Oklahoma. Two hylid frogs, Pseitdacris nigrila
and P. clarki, which are interfertile in the laboratory, overlap nar-
rowly along this boundary, where they show a complex set of isola-
tion mechanisms (Lindsay, 1958). Two narrow-mouth frogs,
Microhyla carolinensis and M. olivacea, overlap narrowly in this
same area, where they hybridize to a limited extent and where
their isolation mechanisms are apparently being reinforced (Blair,
1955). Two populations of toads referred to by some (as by A. P.
Blair, 1941) as an eastern species, Bufofowleri, and a western species,
B. woodhousei, meet and freely interbreed, secondarily, in this same
area (Meacham, 1958). The eastern pine snake {Pituophis melano-
leucus) and the western bullsnake (P. catenifer) either approach
range or interbreed in southeastern Texas (Smith and Kennedy,
454 \V. F. BLAIR
1951). The pigmy rattlesnakes comprise an eastern, forest species,
Sistruriis miliarius, a grasslands species, 5. catenates, and a disjunct
species, 5. raviis, in eastern Mexico (Smith and Taylor, 1945). The
eastern box turtle {Terrapene Carolina) and western box turtle (7".
ornata) overlap narrowly along the forest border. Two harvest mice,
the eastern Reithrodontomys humulis and the western R. montanus,
approach one another but apparently do not meet along the forest
border. The ranges of two packrats, the eastern Neotoma floridana
and the western N. micropus, Interdigitate in the broad forest-grass-
land ecotone. Two skinks, the eastern Eumeccs anthracmus and the
western E. septentionalis, overlap in eastern Oklahoma and Kansas.
An eastern newt, Diemictylus viridescens, ranges west to the edge of
the forest and is separated by a grassland gap from the related
species D. meridionalis of southern Texas and northeastern Mexico.
The group of species pairs discussed above interpret as having
reached their present distributional relationships through post-
Wisconsin spread to the margin of their respective environments,
where they have attained contact or near contact with their sibling
species. Another sizable group of species pairs shows a quite different
pattern in that the Mississippi Embayment, deep within the
Austroriparian forest, is involved in their separation. The species
pairs in this group have mostly remained widely disjunct. Two pairs
appear to be limited by soil types. An eastern pocket gopher, Geomys
pinetis, occurs on sandy soil of the coastal plain to the east of the
embayment, and a western species, G. bursarius, occurs on sands to
the west of it. The alluvial soils of the embayment appear to be the
ecological factor separating the present ranges of these allopatric
species. Two species of spadefoots (Scaphiopus) have essentially
similar distributions. The eastern 5. holbrooki and western S. hurteri
have been shown to be interfertile in the laboratory (Wasserman,
1956). A broader hiatus, of forested land, separates two chorus
frogs, Pseudacris streckeri and P. ornata (Fig. 8). P. streckeri occurs
west of the forest border, which imposes a limit to its eastward
distribution. P. ornata ranges west on the coastal plain to the Mis-
sissippi Embayment. There is little differentiation between the two
in mating call or morphology. Hybrids between them have been
produced, but one attempted backcross of a male hybrid to streckeri
failed (Mecham, 1957). Two species of Rana have a rather similar
distribution: The eastern gopher frog {R. capito) ranges west on the
DISTRIBUTIONAL PATTERNS OF VERTEBRATES
455
coastal plain to the Pearl River; the western crawfish frog (R.
areolata) is abundant on the coastal prairie in eastern Texas and
ranges northeastward in the grasslands but is limited in its eastward
distribution by the forest.
6-OHuoi w«ii «oo
Fig. 8. Present distributions of two closely related, allopatric species
of chorus frogs.
Both forest and grassland occur in the hiatus between the eastern
and western populations of the indigo snake {Drymarchon corais).
The eastern population occurs on the coastal plain east of the
Mississippi Embayment; the western population ranges from the
area of Corpus Christi in Texas southward into northern South
America. The eastern black-headed snake (Tantilla coronata) occurs
east of the embayment, and its western counterpart, T. gracilis,
lives west of the forest border. Eastern and western populations of
Amphiuma, distinguished by a difference in the number of toes,
meet at the Mississippi Embayment where they may act as species
456
W. F. BLAIR
-a
c
to
c
.2
"4-)
U
-M
t«
-5
+->
c
(V
C/2
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 457
(see Baker, 1947) or at most secondarily interbreed. A very wide
disjunction exists between an eastern treefrog, Hyla femoralis,
and the apparently related //. arenicolor of the west (Fig. 9) : H.
femoralis occurs on the coastal plain west to the embayment and
H. arenicolor ranges westward from trans-Pecos Texas, which means
there is a gap of some 700 miles between the ranges.
Another disjunction involving the Mississippi Embayment and a
forest gap is that of the diamondback rattlesnakes. The eastern
diamondback (C adamanteus) is limited on the west by the embay-
ment; the western diamondback (C. atrox), with a wide range in
northern Mexico and the southwestern United States has its east-
ward distril)ution limited at the forest border. An apparently
isolated (relict) population of this species is known from the vicinity
of Tehuan tepee, Oaxaca, Mexico (Stebbins, 1954). A third isolate,
C. ruber, in southern California and Baja California, possibly stems
from a Pleistocene isolate in Baja California fsee Gloyd, 1940).
The gopher turtles (Gopherus) also comprise three isolates (Fig.
10). The eastern species, G. polyphemus, ranges on the coastal plain
west to the vicinity of the Mississippi Embayment. Another, G.
berlandieri, occurs in northeastern Mexico and southern Texas and is
separated from the eastern species by a gap involving both grassland
and forest. The third disjunct. G. agassizi, ranges from northern
Sonora through western Arizona and southeastern California to
southern Nevada.
The cricketfrogs (Acris) have overlapping ranges that involve the
Mississippi Embayment and the margin of the coastal plain. The
eastern coastal plain species, A. grylliis, is limited westward by the
embayment. The western species, A. crepitans, overlaps the range of
the eastern species just east of the embayment and along the Fall
Line (see Blair, 1958). The distributional relationships of these
frogs are comparable to those of the Peroniyscus leucopus group ex-
cept for the limitation of the eastern population by the embayment,
and they are interpreted similarly as the result of post- Pleistocene
spread from Floridian and IVlexican refuges.
The distributional pattern of the Bujo americaniis group of toads
is a more complex variation of the same general pattern (Blair,
1958). The eastern coastal plain form, B. terrestris, is limited west-
ward by the Mississippi Embayment. A population to the north of
the Fall Line, B. americanus, is interpreted as having spread from a
458
W. F. BLAIR
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 459
southwestern refuge, leaving a relict, B. houstonensis , on the eastern
Texas coast.
The Mississippi Embayment also limits the westward distribution
of five species of anurans that have no western counterparts. These
are the oak toad {Bujo quercicus), bird-voiced treefrog {Hyla phaeo-
crypta), barking treefrog {H. gratiosa), little grass frog (//. ocularis),
and river frog {Rana heckscheri) .
The Peromyscus maniculatus group of mice, with one of the most
complex distributional patterns of any North American vertebrate
(Fig. 11), shows east-west speciation on the coastal plain (Blair,
1950). The beach mouse (P. polionotus), which occurs on the coastal
plain east of Mobile Bay, on morphological evidence is derived
from the grassland-adapted ecotype of the deer-mouse (P. manicula-
tus), which today ranges southward into south-central Texas (Fig.
11). The beach mouse presumably originated through an eastward
dispersal along Gulf Coast beaches and subsequent isolation in
Florida. The forest-adapted ecotype of the deer-mouse living today
in the southern Appalachians presumably moved south during
glacial stages into the area that is today a gap between the range of
the beach mouse and that of its Texas progenitor.
The brown water snake {Matrix taxispilota) , which ranges from
Florida into Mexico, has a disjunct population in southern Mexico
(Smith and Taylor, 1945). The rat snake (Elaphe obsoleta) shows
evidence of secondary interbreeding on the Edwards Plateau in
Texas. Turtles of the genus Graptemys are of dubious value here be-
cause of lack of agreement among specialists on the group. As
mapped by Carr (1952) the range of G. pseudogeographica is mostly
west of the Mississippi River, and that of G. geographica mostly east
of it. The mud turtles, Ki?tosterno7t, are represented by two species
in the eastern forest and three to the west of it (Cagle, 1957).
The bats have been omitted from the preceding discussion, but
they too show east-west disjuncts across the coastal plain. Examples
are found in the genera Tadarida, Eumops, Cory?iorhinus, Pipistrel-
lus, Dasypterus, and Lasiurus. In Lasiurus, the pattern of distribu-
tion is comparable to that of the Peromyscus leucopus group: the
western L. borealis overlaps the coastal plain L. seminolus along the
forest border in the west and along the Fall Line.
Some species of vertebrates, showing no evidence of previous dis-
junction, range today completely across the Gulf Coast, and conse-
460
W. F. BLAIR
bution of the Peromyscus maniculatus species group of
Fig. 11. Distri^^.,-..
mice (from Blair, 1950)
quently across the central area from which warmth-adapted species
are indicated to have been driven. Such species as the cotton rat
{Sigmodon hispidus) , cottontail {Sylvilagus floridanus) , coachwhip
{Masticophis flagellum), and green treefrog {Hyla cinerea) are
representative. Their wide distribution can be explained as having
been attained by spread from an eastern or western refuge or by
such a rapid spread from both refuges that contact of populations
and interbreeding were reestablished before marked differentiation
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 461
had occurred. Their existence does not controvert the evidence
presented above of extensive east-west fragmentation of ranges
among warmth-adapted coastal plain vertebrates in the Pleistocene.
Instances of north-south fragmentation of ranges involving
coastal plain species, exclusive of the urodeles, are contrastingly
scarce. The southern rough green snake {Opheodrys aestivus) and
northern smooth green snake (0. vernalis) constitute one example.
However, relicts of the northern species in central and southeastern
Texas (Davis, 1949) indicate a very different past distribution and
suggest the possibility that the present distribution is derived from
an east-west disjunction comparable to that postulated for the
Peromysciis leucopus group. In the common water snake {Matrix
sipedon) a freshwater ecotype shows secondary interbreeding with a
salt-marsh ecotype around the Gulf Coast. Pettus (1956j hypothe-
sized continuous distribution of the salt-marsh type in the Pleisto-
cene and a southern refuge or refuges for the freshwater type. Hyla
andersoni of the New Jersey pine barrens is an apparent relict of a
formerly more northern extension of H. cifierea on the xA.tlantic
coastal plain (see Blair, in press).
The Pseiidacris nigrita group, with the most complex distribution
pattern of any group of North American anurans, does show evi-
dence of north-south speciation in the eastern United States. A
small group of relicts of grasslands-adapted mammals in Mexico
and on the Texas coast (Blair, 1954) is consistent with the thesis of
southward displacement of cold climates and of the Arcto-Tertiary
forest. In the east there are a few such relicts of groups that occur
today in the northern United States. The spotted turtle {Clemmys
guttata) occurs as a relict in northern Florida. A northern species of
frog, Rana sylvatica, has left relict populations in northwestern
Arkansas and in the Flint Hills of Kansas (Smith, 1950).
The distributional patterns of warmth-adapted vertebrates on the
coastal plain as discussed above are overwhelmingly indicative of
east-west fragmentation of ranges as the initial agent of geographic
speciation in this fauna. The variations in distributional patterns
shown by allopatric populations undoubtedly reflect differences in
ability to reoccupy territory after the initial disjunction, differences
in the time that has elapsed since the initial separation, and other
more subtle factors. It might be argued that the east-west speciation
simply reflects adaptation to forest and grassland environments.
462 W. F. BLAIR
However, evidence inconsistent with such an explanation is pro-
\'ideci by the numerous hiatuses between eastern and western
populations that involve segments of one or the other environments
or segments of both.
Sympatric distributions of coastal plain groups may trace back to
the same kind of east- west disjunction exhibited by the allopatric
populations, but such history is difficult to demonstrate. McConkey
(1954) has theorized that the three species of legless lizards (Ophi-
saurus) of the coastal plain originated through east-west splitting
in the Third Glacial (Illinoian) and through subsequent isolation of
the third population on Florida islands in the Third Interglacial
(Sangamon).
DISTRIBUTIONAL PATTERNS OF ANURANS AND URODELES
A comparison of the distributional patterns of anuran and urodele
amphibians in the eastern United States illustrates as clearly as any
possible documentation the postulated Pleistocene history of the
coastal plain biota. The anurans are mostly a warmth-adapted
group, with more species on the coastal plain than anywhere else in
the United States. Ten of the 24 coastal plain species or species
groups show evidence of past or present disjunction into eastern and
western populations, as discussed in the preceding section. Seven of
the 10 have their eastern population limited to the coastal plain.
The other three, Biifo woodhousei, Pseudacris nigrita, and Hyla
versicolor, range widely in the eastern United States. Six of the
remaining 14 species are limited to the coastal plain east of the
Mississippi Embayment and are presumed to have spread to their
present limits from a Pleistocene refuge in Florida. Of the eight
remaining species, only three are limited to the coastal plain. Two
of these, Hyla cinerea and H. squirella, range across the coastal plain
from the Atlantic to Texas, and the range of the third, Rana grylio,
stops short of the forest border in eastern Texas. The five remaining
species, Hyla crucifer, Rana pipiens, R. palustris, R. clamitans, and
R. catesbeiana, all range northward into Canada, and on the basis
of their present distribution it seems likely that they could have
existed continuously across the coastal plain under Pleistocene
Glacial-stage conditions. North-south speciation in the anurans is
limited to the splitting off of Hyla andersoni and the speciation in
the Pseudacris nigrita complex discussed earlier.
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 463
The urodeles, by contrast with anurans, are typically a cool- or
cold-adapted group. The center of distribution of the large family
Plethodontidae, which includes a majority of the urodeles of the
eastern United States, is in the Appalachian highlands in remnants of
the Arcto-Tertiary forest, which the evidence shows to have shifted
southward in the Glacial stages of the Pleistocene. As might be
expected, there is for this group no strong pattern of east- west dis-
junction comparable to that of the warmth-adapted anurans. Of
some 56 species and species groups of urodeles in the eastern United
States, only 23 occur on the coastal plain, and only 11 are restricted
there. Only two of the coastal plain group, Diemictylus and Amphi-
uma, show evidence of east-west disjunction, as earlier mentioned.
The most obvious disjunctions in the eastern urodeles are ones that
are attributable to the southward and westward spread of the Arcto-
Tertiary forest and its urodele fauna under Glacial-stage climates
and to the isolation of relictual populations under locally tolerable
conditions, as the environment became warmer and dryer. This
would explain the relict populations of Plethodon, Hemidactylium,
and Eurycea in the Ozarks, of Plethodon and Eurycea on the Edwards
Plateau, and of Aneides and Plethodon in the mountains of New
Mexico. The absence of plethodontid relicts from the cloud forests
of Mexico, discussed by Martin and Harrell (1957), would be ex-
pected if these animals stayed with the Arcto-Tertiary forest in the
southern United States. The difference in the pattern of distribution
of anurans and urodeles results, then, from the fact that the urodeles
would have moved with the invading environment that fragmented
anuran ranges. Amelioration of the environment that permitted
reoccupation of the coastal plain by warmth-adapted anurans would
have led to the observed disjunctions in urodele ranges. Unlike the
situation in the anurans, there are numerous instances of north-
south or unoriented speciation in the urodeles of the eastern United
States.
SUMMARY
A large body of paleontological and zoogeographical data support
the thesis that present distributional patterns of the warmth-
adapted vertebrates of the Gulf of Mexico and southern Atlantic
coastal plains reflect Pleistocene splitting of this faunal group into
eastern and western populations. The agency of this splitting, as
464 W. F. BLAIR
hypothesized by previous workers, is considered to be the southward
shifting of cHmatic belts during the Glacial stages of the Pleistocene
and the resultant enforced withdrawal of the warmth-adapted biota
into separate refuges in Florida and Mexico.
The evidence from fossil pollens and from plant macrofossils
indicates that at times in the Pleistocene northern species of trees
such as spruce, hemlock, fir, larch, and arbor vitae extended onto
the Gulf and southern Atlantic coastal plains. Boreal mammals and
a few fishes of northern affinity are known from Pleistocene deposits
far south of their present distributions and as far south as southern
Nuevo Leon in Mexico. Both the plant and animal fossils are indica-
tive, then, of major ecological changes in the southern United
States in the Pleistocene.
Evidence from various sources indicates that the southern grass-
lands have not acted as a continuous barrier to the exchange of
forest biotas between the eastern United States and the Mexican
highlands since their origins in the late Miocene and early Pliocene.
The Pleistocene mammalian fauna of Florida includes various groups
of South American origin, some of them forest types, that must have
crossed the area of the present grasslands barrier, as their enti-y into
North America would necessarily have followed the emergence of the
Central American land bridge in the late Pliocene. Various Pleisto-
cene fossils from the area of the present grasslands are indicative of
greater moisture and of forests at times in this area in the Pleisto-
cene. These include such indicators of extreme departure from
present ecological conditions in the area as Neofiber in the Texas
panhandle and Tapirus in trans-Pecos Texas. An impressive number
of present day relicts of forest-adapted species in the grasslands
also argues against past continuity of grassland in the area.
Present distributional patterns of coastal plain vertebrates indi-
cate many east-west and very few north-south disjunctions. Some
of these involve eastern, forest-adapted and western, grasslands-
adapted populations, with the forest-grasslands boundary important
in their present distributional relationships. Other patterns involve
the Mississippi Embayment as a distributional boundary, and in
this group the hiatus between eastern and western populations may
include either forest or grassland, or both. Still other patterns in-
volve eastern and western forest-adapted types, some of which have
their western populations as relicts in the Mexican highlands.
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 465
The fossil evidence of ecological change in the southern United
States during the Pleistocene and the evidence derived from the
existing distributional patterns of vertebrates are consistent in
indicating that the east-west splitting of the warm-adapted biota
by the southward shift of colder climates and of the cold-adapted
biotas has been the chief agency initiating speciation in this area.
The urodeles of the eastern United States show very different dis-
tributional patterns from the anurans, because the conditions that
fragmented the ranges of the warmth-adapted anurans promoted
the southward and westward spread of the urodeles. Then, the condi-
tions that permitted reoccupation of the coastal plain by the anurans
would have forced northward and eastward the retreat of the
urodeles.
Acknowledgment
Base map for figures used with permission of University of Chicago.
Base map for Figs. 1, 2, and 6, copyright 1937 by the University of
Chicago. Base map used for Figs. 3, 4, 5, 7, 9, and 10, copyright 1938 by
the University of Chicago.
REFERENCES
Adams, Charles C. 1902. Southeastern United States as a center of
geographical distribution of flora and fauna. Biol. Bull., 3: 115-131.
Allen, Glover M. 1930. The walrus in New England. /. Mammal., 11:
139-145.
Baker, C. L. 1947. The species of amphiumae. /. Tenn. Acad. Sci., 22:
9-21.
Berry, E. W. 1907. Pleistocene plants from Alabama. Am. Naturalist, 41:
689-690.
Blair, Albert P. 1941. Variation, isolation mechanisms and hybridization
in certain roads. Genetics, 26: 398-417.
Blair, W. Frank. 1939. Faunal relationships and geographic distribution
of mammals in Oklahoma. Am. Midland Naturalist, 22: 85-133.
. 1943. Biological and morphological distinctness of a previously
undescribed species of the Peromyscus tniei group from Texas.
Contribs. Lab. Vert. Biol., Univ. Mich. 24: 1-8.
. 1950. Ecological factors in speciation of Peromyscus. Evolution,
4: 253-275.
. 1951. Interbreeding of natural populations of vertebrates.
Am. Naturalist, 85: 9-30.
. 1952. Mammals of the Tamaulipan biotic province in Texas.
Texas J. Sci., 4: 230-250.
. 1954. Mammals of the mesquite plains biotic district in Texas
466 W. F. BLAIR
and Oklahoma, and speciation in the central grasslands. Texas J.
Sci., 6: 235-264.
— -. 1955. Mating call and stage of speciation in the Microhyla
olivacea-M . carolinensis complex. Evolution, 9: 469-480.
. 1958. Mating call in the speciation of anuran amphibians. Am.
Naturalist, 92: 27-51.
In press. Call structure and species groups in U. S. treefrogs
(Hyla). Southwestern Naturalist.
Braun, E. Lucy. 1955. Phytogeography of unglaciated eastern United
States and its interpretation. Botan. Rev., 21: 297-375.
Brown, Clair A. 1938. The flora of Pleistocene deposits in the western
Florida parishes, West Feliciana Parish, and East Baton Rouge
Parish, Louisiana. State of Louisiana, Dept. Conservation, Geol. Bull.,
12: 59-96.
Bryant, M. D. 1941. A far southwestern occurrence of Pitymys in Texas.
/. Mammal., 22: 202.
Cagle, F. R. 1957. Reptiles. In Blair, Blair, Brodkorb, Cagle, and Moore,
Vertebrates of the United States. McGraw-Hill, New York.
Carr, Archie. 1952. Handbook of Turtles. Comstock Publ. Assoc, Ithaca,
New York.
Clements, Frederic E., and Ralph W. Chaney. 1937. Environment and
life in the Great Plains. Carnegie Inst. Wash., Siippl. Publ. 24: 1-54.
Gushing, J. E., Jr. 1945. Quaternary rodents and lagomorphs of San
Josecito Cave, Nuevo Leon, Mexico. /. Mammalogy, 26: 182-185.
Davis, J. H. 1946. The peat deposits of Florida. Their occurrence, de-
velopment and uses. Florida Geol. Survey, Geol. Bull., 30.
Davis, W. B. 1949. The smooth green snake in Texas. Copeia, 1949: 233.
Deevey, Edward S., Jr. 1949. Biogeography of the Pleistocene. Bull. Geol.
Soc. Am., 60: 1315-1416.
. 1950. Hydroids from Louisiana and Texas, with remarks on the
Pleistocene biogeography of the western Gulf of Mexico. Ecology, 31:
334-367.
Dunn, E. R., and Albert A. Heinze. 1933. A new salamander from the
Ouachita Mountains. Copeia, 1933: U1-U2.
Findley, James S. 1953. Pleistocene Soricidae from San Josecito Cave,
Nuevo Leon, Mexico. U^tiv. Kan. Publ. Mus. Nat. Hist., 5: 633-639.
Frey, David G. 1951. Pollen succession in the sediments of Singletary
Lake, North Carolina. Ecology, 32: 518-533.
Gloyd, Howard K. 1940. The rattlesnakes, genera Sistrurus and Crotalus.
Special Publ. Chicago Acad. Sci., 4: 1-266.
Hay, Oliver P. 1923. The Pleistocene of North America and its verte-
brated animals from the states east of the Mississippi River and from
the Canadian provinces east of longitude 95°. Carnegie Inst. Wash.
Publ. 322.
. 1924. The Pleistocene of the middle region of North America
and its vertebrated animals. Carnegie Inst. Wash. Publ. 322 A.
DISTRIBUTIONAL PATTERNS OF VERTEBRATES 467
Hibbard, Claude W. 1943. The Rezabek fauna, a new Pleistocene fauna
from Lincoln County, Kansas. Univ. Kan. Sci. Bull., 29, Pt. 2, No.
2:235-247.
— . 1949. Pleistocene vertebrate paleontologv in North America.
Bull. Geol. Soc. Am., 60: 1417-1428.
. 1953. The Saw Rock Canyon fauna and its stratigraphic signifi-
cance. Papers Mich. Acad. Sci., 38: 387-411.
• — . 1955a. Pleistocene vertebrates from the Upper Becerra (Becerra
Superior) formation, Valley of Tequixquiac, Mexico, with notes on
other Pleistocene forms. Contribs. Museum Paleontol., Univ. Mich.,
12: 47-96.
■ •. 1955b. The Jinglebob interglacial (Sangamon?) fauna from
Kansas and its climatic significance. Contribs. Museum Paleontol.,
Univ. Mich., 12: 179-228.
— . 1955c. Notes on the microtine rodents from the Port Kennedy
Cave deposit. Proc. Acad. Nat. Sci. Phila., 107: 87-97.
. 1957. Tentative list of Pleistocene fossil mammals in North
America, with their stratigraphic occurrence. In Flint, Glacial and
Pleistocene Geology. Wiley, New York.
Lindsay, Hague L. 1958. An analysis of variation and factors affecting
gene exchange in Pseudacris clarki and Pseudacris nigrita in Texas.
Unpublished doctoral dissertation, The University of Texas.
Lowe, Charles H., Jr. 1950. The systematic status of the salamander
Plethodon hardii, with a discussion of biogeographical problems in
Aneides. Copeia, 1950: 92-99.
McCarley, W. H. 1954. Natural hybridization in the Peromyscus leucopus
species group of mice. Evolution, S: 314-323.
McConkey, Edwin H. 1954. A systematic study of the North American
lizards of the genus Ophisaurus. Am. Midland Naturalist, 51: 133-171.
Martin, Paul S., and Byron E. Harrell. 1957. The Pleistocene history of
temperate biotas in Mexico and eastern United States. Ecology, 38:
468-480.
Meacham, W. R. 1958. Factors affecting gene exchange between two
allopatric populations in the Bufo woodhousei complex. Unpublished
doctoral dissertation, The University of Texas.
Meade, Grayson E. 1952. The water rat in the Pleistocene of Texas.
/. Mammal, 33: 87-89.
Mecham, John S. 1957. Some hybrid combinations between Strecker's
chorus frog, Pseudacris streckeri, and certain related forms. Texas J.
Sci., 9: 337-345.
Miller, Gerrit S., Jr., and Remington Kellogg. 1955. List of North Ameri-
can recent mammals. U. S. Natl. Museum Bull., 205.
Murray, Keith F. 1957. Pleistocene climate and the fauna of Burnet
Cave, New Mexico. Ecology, 38: 129-132.
Osgood, Wilfred H. 1909. Revision of the mice of the American genus
Peromyscus. North Am., Fauna, 28: 1-285.
468 W. F. BLAIR
Pettus, David. 1956. Ecological barriers to gene exchange in the common
water snake {Natrix sipedon). Unpublished doctoral dissertation, The
University of Texas.
Potzger, J. E., and B. C. Tharp. 1947. Pollen profile from a Texas bog.
Ecology, 28: 274-280.
. 1954. Pollen study of two bogs in Texas. Ecology, 35: 462-466.
Sargent, C. S. 1922. Manual of the Trees of North America (exclusive of
Mexico), second edition. Houghton Mifflin, Boston, Mass.
Sherman, H. B. 1952. A list and bibliography of the mammals of Florida,
living and extinct. Quart. J. Florida Acad. Sci., 15: 86-126.
Skinner, Morris F. 1942. The fauna of Papago Springs Cave, Arizona,
and a study of Stockoceros; with three new antilocaprines from
Nebraska and Arizona. Bull. Am. Museum Nat. Hist., 80: 143-220.
Smith, C. Lavett. 1954. Pleistocene fishes of the Berends fauna of Beaver
County, Oklahoma. Copeia, 1954: 282-289.
Smith, Hobart M. 1950. Handbook of amphibians and reptiles of Kansas.
Univ. Kan. Mus. Nat. Hist. Misc. Publ. No. 2: 1-336.
Smith, Hobart M., and J. P. Kennedy. 1951. Pituophis melanoleucus
ruthveni in eastern Texas and its bearing on the status of P. catenifer.
H er petal ogica, 7: 93-96.
Smith, Hobart M., and Edward H. Taylor. 1945. An annotated checklist
and key to the snakes of Mexico. U. S. Natl. Mus. Bull., 187.
Stearns, Charles E. 1942. A fossil marmot from New Mexico and its
climatic significance. Am. J. Sci., 240: 867-878.
Stebbins, Robert C. 1954. Amphibians and Reptiles of Western North
America. McGraw-Hill, New York.
Stebbins, Robert C, and William J. Riemer. 1950. A new species of
plethodontid salamander from the Jemez Mountains of New Mexico.
Copeia, 1950: 73-80.
Wasserman, A. O. 1956. Factors affecting interbreeding in sympatric and
allopatric species of spadefoot toads (genus Scaphiopus). Unpub-
lished doctoral dissertation. The University of Texas.
General Conclusions
Carl L. Hubbs
Scripps Institution oj Oceanography, University of
California, La Jolla
1 he fourteen papers from the symposium on
The Origins and Affinities of the Land and Freshwater Fauna of
Western North America, plus the three richly supplementing contri-
butions from the symposium on Geographic Distribution of Con-
temporary Orgafiisms, constitute a vast storehouse of information on
zoogeography, on companion fields, and on various sciences that
provide the background that is necessary for a full understanding of
zoogeography. The seventeen contributions deal not only with the
actual distribution of many but of course not all groups of land and
freshwater animals, along with some aspects of phytogeography, but
also with various biogeographical topics, and with the background
material. Most of the contributors deal largely with western North
America, but a few cover all of North America, and one even
straddles the whole New World.
The contributions are diverse not only in respect to the groups of
organisms, the areas covered, and the topics stressed, but also in the
angle of approach, in the length and completeness of review, in the
amount of original material, in the thoroughness (or lack) of docu-
mentation, and in the abundance, paucity, or lack of illustrations.
The separate articles vary from abstracts (two) and mere thoughtful
commentaries, on some phase of the general subject, to long, scholarly
studies that give us, for the first time, the summary of a distinguished
author's long-continued and intensive research.
The whole volume has both the strength and the weakness that
goes with diversity. It is strong in the variety of viewpoints and
specialties, in the high competence of each invited participant in
some aspect of zoogeography or in one of the basically related
sciences, and in the potential synthesis that is favored by the close
association of the diverse contributions. It is weak in the fragmenta-
469
470 C. L. HUBBS
tion of the subject, due to the increasing specialization of scientists,
in the lack of attention to some groups and topics (an unavoidable
defect in the age of specialization), and in the limited detail and
documentation in some of the papers.
The diversity of treatment calls at the outset for an organized
indication (Table I) of the coverage of the various papers, in terms
of geographic, evolutionary, systematic, and background considera-
tions.
The individual papers are referred to in the table (and in the fol-
lowing text) by number as given in the Contents. In the table,
degree of emphasis (in the papers as printed) is roughly approxi-
mated by the type: roman for least emphasis, italics, for more
thorough treatment, and boldface for most exhaustive coverage.
The emphasis on background considerations and on evolutionary
and systematic correlatives, brought to focus in the table, is a strong
indication of a healthy rebound from the course of overspecializa-
tion. The trend toward interdisciplinary research is exemplified in
several of the contributions, and is perhaps best illustrated, as well
as stated, in Martin's contribution (15) on Pleistocene ecology. The
same happy trend is glowingly evident in several of the other papers,
notably, for example, those by MacGinitie (2) and by Blair (17).
The overall treatment further indicates a shift from the classical,
purely descriptive biogeography to a kinetic approach, which is
more concerned with processes and explanations than with the
classification of the earth into a hierarchy of biogeographical regions.
Attention is focused on floral and faunal elements of diverse origin,
which may be mixed in any one area, and on the past and present
dispersions of these biotic elements. This concept of biotic elements,
which was advanced particularly by Ernst Mayr (followed herein
by Parkes, 16), penetrates into the limited regional classifications
of faunas in these symposia. Linsley (13), for example, maps the
same area of the central California coast as a diluted part of both the
Vancouveran and Californian faunas, and Rehn (12) apportions the
western North American orthopteran fauna according to regions
of origin.
Past and continuing shifts in biota receive considerable attention,
in line with the more kinetic approach that is fortunately coming
into vogue. The background for such biotic dispersals is elucidated
in several of the papers, notably by King's (1) sweep through the
GENERAL CONCLUSIONS 471
grand history of changes in the face of the earth over western
North America, by MacGinitie's (2) analysis of climatic trends and
fluctuations in this region since Cretaceous time, and by the excellent
reviews by Martin (15) and by Blair (17) on the dramatic events of
the Pleistocene and their consequences.
Some new, refined approaches in biogeographical analysis are
emphasized. One of these is the quantitative reconstruction of past
vertebrate biocoenoses through the study of all identifiable material
obtained by soil washing — a truly revolutionary (and long overdue)
development, as D. E. Savage (4) indicates. Another major refine-
ment is the more precise and penetrating systematic analysis, such as
is indicated in most of the reports, notably those by Peabody and
J. M. Savage (8), R. R. ^filler (9), and Parkes (16). Another cir-
cumstance favoring sound biogeographical conclusions is the life-long
devoted specialization on single groups, throughout their range, that
is obvious in the contributions by several of the authors, notably
A. H. Miller (6), R. R. Miller (9), and the entomologists: Ross (11),
Rehn (12), Linsley (13), and Hovanitz (14). Radiocarbon dating
becomes a tool of research in blogeography, as in other areas (Mar-
tin, 15). Quantitative studies, including pollen analysis, are helping
to displace inference with data. And, most effective of all as a lead
toward a fuller understanding of the events and processes in bio-
geography is the recourse to interdisciplinary and multidisciplinary
approaches.
The fabric of this symposium has been woven of threads that vary
so much in color, size, and strength as to make it difficult to pick
out these threads to reweave a simple review and conclusion. On
some basic lines, however, there is sufficient consensus to permit
some generalization.
One initial thought that seems justified is that blogeography is
still a propitious field of inquiry. Certainly, many of the defects of
the past are attributable to excessive inference on the basis of Inade-
quate data. Through more intensive research, sharpened by new
techniques and enriched by Interdisciplinary approach, sound data
are certain to result, and broader and more reliable interpretations
are bound to develop. Through the symposium there is to be found
much justification for this optimism.
A notable feature of the whole series of papers is that there is
hardly a mention of the transoceanic land bridges that blogeog-
472 C. L. HUBBS
raphers not long ago threw around with abandon. King (1) assures
us that geologists hold to the theory of the essential permanence of
the ocean basins, and the biologists seem to have proceeded on this
assumption. The verified intercontinental connections across the
Isthmus of Panama and especially across the Bering Strait region
are duly treated. The intimate relationships between the Palearctic
and Nearctic faunas are pointed out by Parkes (16) and other
authors, and are rightly assumed to indicate a past continuity, but,
as Burt (5), Rehn (12), and Hovanitz (14) point out with admirable
reserve, there is, as yet, usually little basis for postulating the region
of origin and the direction of dispersal. In some groups there may
have been a complex interchange.
In general, it is admitted, or apparently assumed, that the recon-
struction of the past history of a group, whether of origin or dis-
persal, cannot ordinarily be postulated with assurance on the sole
basis of the present distributional pattern. Considerable variance in
reserve or reliance, however, is displayed in such reconstructions.
Bartholomew (3) and Burt (5) go so far as to say there are no
separate "origins," because there has been a continuum of life, but
are they not playing with semantics? In terms of given natural
groups or stages of evolution there is an origin, in both time and
space.
The criteria of center of origin, or of differentiation, as some would
prefer to say, are definitely discussed by only two of the authors,
D. E. Savage (4) and Burt (5). Savage's criteria are the more impres-
sive because they emphasize the fossil record. His first criterion of
area of origin is the region from which the oldest fossil is known.
This is fine for groups with a well-known fossil record, but for groups
with few known fossils may, as Parkes (16) notes, be even more
treacherous than criteria based on present distributions. Savage's
second criterion is an earlier record of progenitors (the sort of
evidence that puts man's origin securely in the Old World) — again
good, if the data are adequate. His third criterion is the area of
greatest taxonomic diversity. This criterion may usually hold, but
certainly not always. It seems not to apply, for example, to the
origin of the catostomid fishes, which are almost restricted to North
America, but which R. R. Miller (9) and I believe, on scanty but
pertinent distributional and fossil evidence, to have originated in
Asia, though they seem to have undergone most of their difi^erentia-
GENERAL CONCLUSIONS 473
tion in North America. Savage argues wisely that phyletic age,
relict occurrence, and vagility must be taken into account, but he
doesn't indicate just how. Other frequently expounded criteria are
just mentioned, along with Mathew's hypothesis that primitive
forms are peripheral.
Savage sharply criticizes the location of the major center of
origin in the Old World tropics, on the basis of the evidence that the
present Holarctica is temperate to boreal. As both he and Mac-
Ginitie (2) point out, the northern lands were subtropical through
much of Cenozoic time. Obviously, much of evolutionary history is
still hidden in a fog of ignorance. The task of the historians of life
has barely begun. And until we know the past, we cannot fully
understand the present nor guess the future.
Several of the authors hold to the view long championed by
Chaney and by Axelrod, and here expounded by MacGinitie (2),
that world climate became progressively more arid and cooler
through Tertiary time, while increased relief and other factors
caused greater local diversity. It seems that there was a general
northward shift in the climatic zones. All this caused a great trans-
location of the geo-floras, and, presumably, of the accompanying
animal communities. Some zoologists, for example Peabody and
J. M. Savage (8), have been bold enough to reconstruct origins and
dispersals of certain animals on the basis of the history of the geo-
floras with which they infer these animals were associated. Are they
treading on firm ground or on quicksand?
It seems to be the general consensus that the vast uniformity of
life that characterized the early Cenozoic, in both space and time,
gradually changed to diversity throughout Tertiary time, in a grand
crescendo that reached ecstatic proportions in the Pleistocene.
Martin (15) and Blair (17) have compiled impressive evidence favor-
ing the view, which seems to me to be well justified, that the Ice
Ages were periods of intense cold, during which climatic belts were
displaced far southward (and far downward on the mountains), and
during which even the tropics were very considerably cooled. Dur-
ing the Wisconsin period the temperate biota of eastern North
America seems to have been forced into refugia in Florida and
Mexico (Blair, 17), while in the West (Miller, 9) there was extensive
extermination of the freshwater fauna in the north and a vast
development of lakes in the Great Basin and southward.
474
C. L. HUBBS
Table I. Index to Subject Coverage in Symposia on Zoogeography
Numbers in parenthesis refer to the separate papers by the stated
authors. Degree of emphasis is roughly approximated by type — roman
for least emphasis, italics for more thorough treatment, boldface for
most exhaustive coverage.
Evolutionary and
Systematic Considerations
PHYSIOLOGICAL BACK- PHYLOGEXIES : D. E
Geographical
Considerations
Background
Considerations
CRITERIA (on Centers
of Origin or Differ-
entiation) : D. E.
Savage (4), Burt
(5), Rehn (12),
Hovanitz (14),
Parkes (16)
EFFECTS OF MAN
Of Primitive Man :
Martin {15)
Of Modern Man:
Pennak (10)
AREAS TREATED
BIOGEOGRAPHICALLY
Entire New World:
Hovanitz (14)
Nearctica: D. E.
Savage (4), Mar-
tin (15), Parkes
(16), R. R. Miller
(9), Linsley (13)
Southeastern United
States: Blair (17)
Western North
America: King (1),
MacGinitie (2),
D. E. Savage (4),
Burt (5), Peabody
and J. M. Savage
(8), R. R. Miller,
(9), Rehn (12),
Pennak (10),
Ross (11), Lins-
ley (13)
ground: Bartholomew
(3), Hovanitz (14)
GEOLOGICAL BACK-
GROUND
General: King (1),
MacGinitie (2),
Peabody and J.
M. Savage (8)
Hydrographic His-
tory: R. R. Miller
(9), King (1)
Pleistocene Events:
Martin (15), King
(1), MacGinitie
(2), Blair (17)
Physiographic Re-
lations: King (1),
Peabody and J. M.
Savage (8), R. R.
Miller (9) , MacGinitie
(2), Hovanitz (14),
Blair (17)
PALEONTOLOGICAL
BACKGROUND
Plantes: MacGinitie
(2), Linsley (13),
Martin (15),
Blair (17)
Insecta: Linsley (13),
Ross (11), Rehn
(12), Martin (15)
Pisces: R. R. Miller
(9), Blair (17)
PHYLOGENIES:
Savage (4), Burt (5),
R. R. Miller (9),
Ross (11)
EVOLUTIONARY RATES :
Martin (15), D. E.
Savage (4), Ross
(11)
SPECIATION : Peabody
and J. M. Savage
(S),A. H. Miller
(6), Pennak (10),
Hovanitz (14),
Martin (15), Parkes
(16), Blair (17)
GROUPS TREATED
BIOGEOGRAPHICALLV
Plantes :MacGinitie
(2), Martin (15),
Linsley (13),
Blair (17)
Invertebrata:
Pennak (10)
Insecta
Dermaptera and
Orthoptera:
Rehn (12)
Northern and
Montane
Insects:
Koss (11)
Cerambycidae:
Linsley (13)
GENERAL CONCLUSIONS
475
Table I. Index to Subject Coverage in Symposia on Zoogeography
— Continued
Geographical
Considerations
Relations with Asia:
Burt (5),
Parkes (16),
MacGinitie (2),
D. E. Savage (4),
A. H. Miller (6),
R. R. Miller (9),
Ross (11), Rehn
(12), Linsley (13),
Hovanitz (14)
Relations with
South America:
Hovanitz (14),
D. E. Savage
(4), Burt (5), R. R.
Miller (9), Lins-
ley (13), Blair
(17)
Relations of East-
ern to Western
North America:
Blair (17), Pennak
(10), Burt (5),
A. H. Miller (6),
R. R. Miller (9),
Ross (11), Lins-
ley (13), Hovanitz
(14), Martin (15)
Background
Considerations
Amphibia and
Reptilia: Peahody
and J. M. Savage
(8)
Aves: Parkes (16)
Mammalia: D. E.
Savage (4),
Martin {15), Blair
{17)
PALEOCLIMATOLOGICAL
BACKGROUND
Cretaceous :
MacGinitie (2)
Tertiary:
MacGinitie (2),
King (1), Peabody
and J. M. Savage
(8), Linsley (13),
Blair (17)
Pleistocene: Martin
(15), Blair (17),
MacGinitie {2),
King (1), Stebbins
(7), Hovanitz (14)
PALEOECOLOGICAL
BACKGROUND :
MacGinitie (2),
Blair (17),
Martin {15), D. E.
Savage (4), Burt (5)
ECOLOGICAL BACK-
GROUND : Martin
(15), Pennak {10),
Linsley {13),
Hovanitz {14),
Blair {17), R. R.
Miller (9), Ross (11)
Evolutionary and
Systematic Considerations
Lepidoptera:
Hovanitz (14)
Pisces: R. R. Miller
(9), Blair (17)
Amphibia and
Reptilia : Peabody
and J. M. Savage
{8), Stebbins (7),
Martin (15),
Blair (17)
Aves : Parkes (16),
A. H. Miller (6)
Mammalia: D. E.
Savage (4),
Burt (5),
Martin {15),
Blair (17)
Man: Martin {15)
476 C. L. HUBBS
Despite the evidence of extreme climatic change at the close of
Wisconsin time and during the Postpleistocene millenia, Martin (15)
holds to the view that the extinction of the large Pleistocene mam-
mals is attributable not to climatic change, but to man. I favor the
theory of a combination of factors.
After the recurrent restoration of humidity in the Pleistocene,
the trend toward aridity seems to have continued in the West. The
deserts seem to have marched northward and to have spread out
like a vast desiccating fan toward the Pacific Coast and onto the
Great Plains. This trend is just mentioned in the abstract by
Stebbins (7), and it is considered, but I believe probably set too far
back in Cenozoic time, by Peabody and J. M. Savage (8). Desicca-
tion is plausibly held by R. R. Miller (9) and by Pennak (10) to have
been largely responsible for the impoverished freshwater fauna of the
West and for the high incidence of local endemism. A. H. Miller
(6) attributes the high ratio of endemism among the birds of the
Californian fauna to the isolation of this fauna by deserts.
In some groups, as the Orthoptera (Rehn, 12) and Reptilia, in
contrast, the intensification and spread of the Sonoran region seems
to have been a potent evolutionary stimulus.
Redispersals following the vast displacements of the Pleistocene
are held to have induced some very interesting speciational situa-
tions. Blair (17) postulates the genetic responses, during Recent
sympatry, of cognates that had been isolated in the Floridan and
Mexican refugia. Hovanitz (14) similarly treats the consequences of
cohabitation of butterflies previously segregated by the Wisconsin
ice sheet. One pair, he states, has, by hybridization, thus produced a
third species.
Geologically recent topographic changes are held to have condi-
tioned other significant speciational events. Hovanitz (14) attributes
the high incidence of endemism of butterflies in the Andes to the
new environments suddenly furnished by the rapid uplift of the
Cordillera, and he regards this type of response as of general signifi-
cance. Peabody and Savage (8) explain speciational relations among
amphibians and reptiles in California on the basis of the establish-
ment of a Coast Range Corridor. They cite evidence that the Sierra
Nevada and Coast Ranges were long separated on the south by a
marine barrier, so that the forms on the two ranges became sub-
specifically difi"erentiated, though intergrading where their ranges
GENERAL CONCLUSIONS 477
converged in the north. They postulate that when the corridor be-
came estabhshed the cognates met, but, because of the degree of
separation, remained distinct in cohabitation, behaving here as full
species at the respective ends of an otherwise specific continuum
(in other words, forming "open circles").
In a slightly Chauvanistic vein, these authors close their paper
with this exultation: "We may confidently reaffirm and echo A. B.
Howell's assertion of thirty years ago that the fauna of the Pacific
Coast is of unusual interest and presents many fascinating problems.
Californians have a land-bridge laboratory in their own back yard!"
But, as is suggested by the references just made to Hovanitz and to
Blair, similarly fascinating situations exist outside the Golden West.
Zoogeographical gold is where you find it!
Author Index.
Adams, C. C, 433, 465
Aguayo, C. G., 409, 413
Allee, W. C, 85, 94, 97, 127
Alexander, W. B., 423, 431
Allen, G. M., 409, 413, 436, 465
Allen, J. A., 410, 414
Allen, V. T., 40, 57
Amadon, D., 427, 431
Andersen, S. T., 377, 386, 414
Anderson, F. M., 19, 57
Andrewartha, H. B., 82, 93
Antevs, E., 72, 77, 382, 391, 414
Anthony, B., 219
Anthony, H. E., 409, 414
Atkinson, W. S., 209
Atwood, W. W., 28, 31, 33-35, 57
Atwood, W. W., Jr., 28, 31, 33-35,
57
Axelrod, D. I., 34, 41-43, 57, 69,
77, 100, 114, 126, 166-168, 170,
185, 303-306, 318, 473
Bailey, R. M., 198, 219
Baker, A. A., 14, 57
Baker, C. L., 457, 465
Baldwin, A. H., 198
Barclay, F. H., 413
Barendsen, G. W., 387, 414
Barnes, W., 365
Bartholomew, G. A., 85, 86, 88-
90, 472, 474
Bates, M., 365
Bell, R. Y., 59
Bell, W. A., 112, 127
Benson, R. B., 233, 252
Benson, S. B., 412, 414
Bentley, P. J., 89, 94
Berg, L. S., 197, 205, 219
Berry, E. W., 112, 127, 435, 465
Birch, L. C., 82, 93
Blackwelder, E., 213, 219
Blackwelder, R. E., 318
Blair, A. P., 453, 465
Blair, W. F., 433, 447, 453, 457,
459, 461, 465, 466, 470, 471,
473-477
Blaxter, K. L., 87, 94
Bogert, C. M., 85, 94
Bogolepov, K. v., 66, 77
Bowman, K., 365
Boyce, S. G., 381, 419
Bradley, J. C., 318
Bradley, W. H., 27, 28, 33, 57
Brame, A. H., 179, 186
Brattstrom, B. H., 160, 185
Braun, E. L., 375, 377, 382, 414,
433, 435, 441, 445, 466
Breyer, A., 365
Brock, V. E., 214
Broecker, W. S., 404, 414
Brooks, C. E. P., 64, 71, 77
Brooks, G. S., 366
Brown, A. L., 210
Brown, B., 440
Brown, C. A., 72, 77, 435, 466
Brown, F. M., 366
Bryan, K., 36, 57
Bryant, M. D., 447, 466
Bullock, T. H., 88, 94
Burbank, W. S., 14, 23, 57
Burt, W. H., 153, 472, 474, 475
Cabrera, A., 136, 137, 153
Cade, T. J., 86, 88, 93
Cagle, F. R., 459, 466
Cain, S. A., 134, 153, 383, 414
Camp, C. L., 160, 163, 164, 185
Carpenter, F. M., 233, 252
Carpenter, G. D. H., 366
Carr, A., 459, 466
Chandler, M. E. J., 65, 79
Chaney, R. W., 46, 57, 64, 66, 67,
69, 78, 100, 127, 129, 168, 185,
390, 414, 434, 466, 473
Chu, Y. T., 220
Clark, A. H., 366
479
480
AUTHOR INDEX
Clark, J., 129
Clark, J. G. D., 375, 414
Chatfield, P. O., 88, 94
Clements, F. E., 434, 466
Clisby, K. H., 380, 390, 391, 414,
419
Cockerell, T. D. A., 259, 318
Cohen, N. W., 85, 94
Colbert, E. H., 120, 127, 129,413,
414
Comstock, J. A., 366
Comstock, W. P., 366
Condit, C, 185
Cook, H. J., 104, 127
Cook, S. P., 405, 416
Cooke, C. W., 405, 414
Cooper, W. S., 313, 318
Cope, E. D., 192, 194, 220
Core, E. L., 382, 414
Courtemanche, A., 385, 418
Cowles, R. B., 85, 94
Craig, R. A., 71, 77, 78
Crampton, G. C, 289
Crane, H. R., 405, 414
Crook, W. W., 412, 414
Cross, W., 30, 58
Crowell, J. C, 52. 58
Cruxent, J. M., 395, 414, 418
Curtis, G. C, 58
Gushing, J. E., Jr., 436, 438, 466
Dane, C. H., 57
Dansereau, P., 378, 379, 395,
407, 413, 414
Darlington, H. C, 382, 387, 414
Darlington, P. J., Jr., 101, 102,
127, 134, 142, 153, 190, 199,
220, 318, 421, 422, 425, 427,
430, 431
Darwin, C, 97, 104, 127, 395, 396,
414
Davenport, D., 366
Davis, A. C, 318
Davis, J. H., Jr., 72, 78, 415,
435, 466
Davis, M. B., 377, 381, 387,
388, 413, 415
Davis, W. B., 461, 466
Davis, W. M., 38, 58
Dawson, W. R., 85, 86, 90, 93
Deevey, E. S., Jr., 141, 153, 375,
377, 382, 384, 386, 387. 389,
409, 413, 414, 417, 433, 434,
466
Denny, C. S., 377, 415
Denton, S. P., 202
Dibblee, T. W., Jr., 52, 58, 114,
127
Dietz, R. S., 53, 59
Dillon, L. S., 366, 375, 390, 415
Dorf, E., 62, 63, 78, 318
Dosh, E. P., 382, 419
Drury, W. H., 377, 378, 382, 383,
415
Dumas, P. C, 90, 94
Dunbar, C. O., 57
Dunkle. D. H., 106, 127
Dunn, E. R., 450, 466
Durham, J. W., 63, 65, 68, 78,
114, 127, 249, 252
Durham, W., 168, 185
Dyar, H. G., 366
Dylik, J., 381, 415
Eager, G., 206
Eardley, A. J., 10, 12, 57, 58,
164, 165, 185
Eastman, C. R., 220
Eaton, T. H., Jr., 203, 220
Edwards, R. S., 58
Edwards, W. H., 366
Eisenmann, E., 424, 432
Eisley, L. C, 403, 412, 415
Elias, M. K., 69, 78
Ellerman, J. R., 136, 137, 153
Elrod, M. J., 366
Elson, J. A., 413
Elwes, H. J., 366
Emerson, A. E., 99, 102, 127
Emiliani, C, 63, 72, 78, 141, 153,
249, 252, 376, 415
AUTHOR INDEX
481
Epstein, S., 249, 252
Erdbrink, D. P., 137, 145, 153
Estes, R., 161
Evermann, B. W., 198, 200, 202,
205, 207-209, 220
Evernden, J. F., 18, 58
Ewing, M., 8, 16, 58
Fall, H. C, 318
Fenneman, N. M., 57
Ferguson, H. G., 18, 58, 59
Field, W. D., 366
Findley, J. S., 372, 436, 466
Fiske, W. F., 366
Fitch, H. S., 412, 415
Fitter, R. S. R., 423, 431
Flint, R. F., 72, 74, 77, 78, 122,
127, 375, 377, 378, 382, 389,
391, 392, 401, 402, 411, 413,
415
Forbes, W. T. M., 366
Foreman, F., 419
Fox, R. M., 366
Frenzel, B., 375, 415
Frey, D. G., 378, 379, 381, 386,
387, 415, 435, 466
Fries, C. C., 106, 127
Frye, J. C., 70, 78
Garnett, R. T., 318
Garth, J. S., 366
Gay, H., 366
Gazin, C. L., 106, 127
Gibson, A., 367
Gilbert, C. H., 210, 220
Gill, E. D., 403, 409, 413, 415
Gilluly, J., 53, 58, 59
Gloyd, H. K., 457, 466
Godman, F. D., 367
Goldsmith, J. W., 59
Goodlett, J. C., 381, 416
Goodrum, P., 415
Gralenski, L. J., 414
Grant, M., 107, 127
Gressitt, J. L., 318
Griffin, H., 413
Grinnell, F., Jr., 367
Grinnell, J., 367
Griscom, L., 393, 416
Grossbeck, J. A., 367
Guilday, J. E., 412, 416
Hack, J. T., 381, 382, 416
Hall, E. R., 135, 153
Hamilton, J., 318
Hamilton, W. J., 89, 94, 413, 416
Handlirsch, A., 303, 318
Hansen, H. P., 391, 416
Hardy, G. H., 318
Hardy, R., 142, 153
Hare, F. K., 378, 413, 416
Harrell, B. E., 392, 393, 413, 416,
417, 441, 445, 447, 452, 453,
463, 467
Harris, R. K., 412, 414
Harriss, T. F., 18, 60
Haury, E. W., 396, 413, 416
Hay, O. P., 436, 440, 444, 466
Hayden, E. B., 410, 411, 418
Hayward, K. J., 367
Hecht, M. K., 411, 416
Heinze, A. A., 450, 466
Heizer, R. F., 405, 416
Herre, A. W. C. T., 214, 220
Hesse, R., 85, 94, 97, 127
Hester, J. J., 413
Heusser, C. J., 391, 416
Heyerdahl, T., 411, 416
Hibbard, C. W., 106, 122, 123,
127, 376, 401, 402, 404, 413,
416, 436, 438, 440-442, 444,
467
Hill, M. L., 52, 58
Hock, R. J., 88, 94, 95
Hodge, E. T., 47, 48, 58
Hoffmann, C. C., 367
Hollister, J. S., 51, 53, 59
HoUom, P. A. D., 423, 432
Horn, G. H., 318, 319
Hospers, J., 76, 78
Hotz, P. E., 59
Houpt, T. R., 95
482
AUTHOR INDEX
Hovanitz, W., 367, 471, 472, 474-
477
Howard, A. D., 36, 58
Howell, A. B., 159, 185, 477
Howell, T. R., 92, 93
Hoy, H. E., 215, 220
Hubbell, T. H., 284
Hubbs, C. L., 37, 42, 43, 58,
193, 203, 206-210, 212-214,
216, 217, 219-221
Hulten, E., 319
Hunt, C. B., 30, 35, 36, 58, 404,
416
Hussakof, L., 193, 220
Hustich, I., 378, 416
Hutchinson, G. E., 91, 94, 392,
417
Irving, L., 86, 94, 95
Irwin, J. H., 19, 31, 58, 59
Iversen, J., 417
Jameson, D. J., 59
Jarnum, S. A., 95
Jenness, D., 418
Jennings, J. D., 417
Jepsen, G. L., 120, 127, 129
Johnson, P., 95
Johnson, H. R., 58
Johnson, W. D., 31, 58
Jordan, D. S., 198, 200, 202, 205,
208, 209, 220
Jordan, K., 367
Jorgensen, P., 367
Kay, M., 9, 58
Kaye, W. J., 367
Kayser, C., 88, 94
Kellogg, R., 136, 137, 153, 409,
418, 436, 467
Kennedy, J. P., 453, 468
Ketner, K. B., 59
Khalaf, K., 245, 252
King, P. B., 36, 58, 470, 472, 474,
475
Kitts, D. B., 384, 417
Klebs, R., 303, 319
Knowlton, F. H., 65, 78, 112,
127
Koopman, K. P., 409, 410, 413,
417, 420
Krog, H., 94
Kulp, J. L., 414
Lack, D., 83, 94
Lance, J. P., 59, 221,413
Landry, S. O., Jr., 100, 127
Lange, A. L., 391, 417
Langston, W., Jr., 101, 127
Larsen, E. S., 30, 59
LeConte, J. L., 319
Lee, A. K., 89, 94
Lee, T. E., 394, 417
Lee, W. T., 36, 59
Leighton, B. V., 367
Leonard, A. B., 70, 78
Leopold, A. S., 390, 417
Leopold, E. B., 413
Leopold, L. B., 72, 78
Leopold, S. B., 377, 387, 388, 417
Lewis, C. B., 366
Li, Hui-Lin, 69, 78
Lindroth, C. H., 424, 431, 432
Lindsay, H. L., 453, 467
Lindsey, C. C., 187, 198, 211,
217, 218, 220
Linsley, E. G., 104, 128, 302, 315,
319, 470, 471, 474, 475
Lipson, J. I., 58
Livingstone, B. G. R., 377, 384,
385, 387, 417
Livingstone, D. A., 377, 384, 385,
387, 413,417
Longstaff, G. B., 367
Longwell, C. R., 10, 36, 39, 56,
59, 221
Lonnberg, E., 429
Lonsdale, J. T., 129
Louderback, G. D., 59
Love, A., 413
Love, D., 413
Lovering, T. S., 14, 23, 57
AUTHOR INDEX
483
Lowe, C. H., Jr., 74, 78, 179,
186, 413, 450, 467
Lowenstam, H. A., 249, 252
Lowther, G., 413
Lucas, F. A., 194, 221
Lydekker, R., 97
Lyman, C. P., 88, 94
McAlpine, W. S., 367
McCarley, W. H., 453, 467
McConkey, E. H., 462, 467
MacCurdy, G. G., 414
McDonald, J. E., 413, 492
MacDonald, J. R., 67, 78
McDunnough, J. J., 365
MacGinitie, H. D., 65, 67, 69,
79, 301, 304, 319, 470, 471,
473-475
McGrew, P. O., 107, 128
McKee, E. D., 19, 59
McKenna, M., 161
McKenna, M. C., 106, HI, 119,
128
MacLachlan, J. C, 59
MacLachlan, M. E., 59
MacNeish, R. S., 404, 417
Mackin, J. H., 25, 31, 34, 56, 59
Macy, R. W., 367
Main, A. R., 89, 94
Malin, J. C., 74, 79
Manley, G., 71, 79, 386, 417
Mannerheim, G. C. G., 319
Manning, T. H., 384, 417
Marshall, J. T., 393, 417
Martin, J. O., 319
Martin, M., 413
Martin, P. S., 377, 380, 382, 387,
391, 392, 417, 441, 445, 447,
452, 453, 463, 467, 470, 471,
473-476
Martynov, A. V., 254
Mason, H. L., 61, 79, 304, 325,
319, 390, 414
Matthew, W. D., 97, 101, 102,
104, 127, 134,409,417,475
Maxwell, R. A., 129
Mayr, E., 100, 102, 104, 128, 421,
422, 425, 429, 432, 470
Meacham, W. R., 453, 467
Meade, G. E., 442, 467
Mecham, J. S., 454, 467
Meek, S. E., 214, 221
Menard, H. W., 53, 59
Mercer, J. H., 384, 417
Merriam, C. H., 137, 141, 153,
311, 313, 314, 319
Michener, C. D., 315, 319
Miller, A. H., 92, 94, 390, 417,
471, 474-476
Miller, G. S., Jr., 136, 137, 153,
409, 418, 436, 467
Miller, R. R., 37, 43, 58, 193, 207-
210, 212-217, 220-222, 471-476
Mitono, T., 319
Monson, M., 94
Moore, T. E., 243, 244, 252
Moreau, R. E., 375, 418
Morrison-Scott, T. C. S., 136,
137, 153
Mosely, M. E., 232, 252
Mosimann, J. E., 413
Mountford, G., 423, 432
Muller, S. W., 18, 58
Murray, K. F., 73, 79, 391, 418,
436, 440, 467
Myers, G. S., 102, 128, 191, 221
Nelson, E. M., 199, 201, 221
Newman, C, 415
Nikiforofif, C. C., 382, 418
Noble, L. P., 52, 59
Nolan, T. B., 12, 38, 59
Norris, K. S., 85, 92, 94
Officer, C. B., 58
Ogden, J. G., 413
Olivier, G., 430, 432
Olson, E. C., 107, 128
Opik, E. J., 77, 79
Oriel, S. S., 59
484
AUTHOR INDEX
Osborn, H. F., 97, 128, 405, 411,
413, 418
Osgood, W. H., 135, 153, 154, 453,
467
Parkes, K. C, 403, 470-472, 474,
475
Patrick, R., 417
Patterson, B., 106, 120, 128
Peabody, F. E., 161, 180, 185, 186,
471, 473-477
Pearson, O. P., 85, 86, 95
Peltier, L. C, 377, 418
Pennak, R. W., 474-476
Peters, J. L., 432
Peterson, R. T., 423, 424, 427, 432
Pettus, D., 461, 468
Plass, G. N., 75, 77, 79
Pongracz, A., 303, 319
Potzger, J. E., 72, 79, 381, 385,
387, 388, 418, 420, 435, 468
Powell, J. W., 59
Press, F., 8, 58
Pruitt, W. O., Jr., 142, 154
Quimby, G. I., 394, 418
Quinn, J. H., 129
Rabb, G. B., 410, 411, 413, 418
Ramaswami, L. S., 203, 221
Rand, A. L., 384, 418
Rasmussen, W. C., 382, 418
Reed, C. F., 160, 186
Reed, E. C., 367
Reed, R. D., 51, 53, 59
Reeside, J. B., Jr., 57. 129
Regan, C. T., 199, 205, 221
Rehn, J. A. G., 470-472, 474-476
Reid, E. M., 65, 79
Repenning, C. A., 31, 37, 59, 193,
221
Riemer, W. J., 450, 468
Roberts, R. J., 12, 59
Robins, C. R., 210, 222
Robinson, G. D., 56
Romer, A. S., 101, 128, 411, 413,
418
Rosenthal, G. M., 171, 186
Ross, H. H., 234-236, 238, 239,
241-244, 251, 252, 471, 474, 475
Rostlund, E., 197, 198, 222
Rothschild, W., 367
Rouse, I., 395, 404, 405, 414, 418
Rouse, J. T., 30, 59
Rousseau, J., 378, 418
Russell, L. S., 106, 128
Salvin, O., 367
Sargent, C. S., 445, 447, 468
Sauer, C. O., 411, 418
Savage, D. E., 471-475
Savage, J. M., 179, 186, 471,
473-477
Sawyer, W. H., 85, 95
Schaeffer, B., 102, 128
Schaeffer, C., 320
Scharff, R. F., 376, 418
Schmid, F., 235, 252
Schmidt, K. P., 85, 94, 97, 101,
127, 128
Schmidt-Nielsen, B., 87, 95
Schmidt-Nielsen, K., 87, 95
Schoenwetter, J., 413
Scholander, P. F., 86, 95
Schultz, J. R., 390, 419
Schultz, L. P., 196, 219, 222
Schwade, I. T., 114, 128
Sclater, P. L., 97
Scott, W. B., 132, 141, 154
Scudder, S. H., 320, 368
Sears, P. B., 380, 390-392, 414,
419
Seitz, A., 323, 368
Sellards, E. H., 394, 419
Seward, A. C., 64, 79
Shapley, H., 415
Sharp, A. J., 74, 79
Sharpe, C. F. S., 382, 419
Shepard, H. H., 367
Sherman, H. B., 441, 442, 444, 468
AUTHOR INDEX
485
Shotwell, J. A., 108, 128
Sibree, J.,409, 419
Simpson, G. G., 97, 104, 106, 109,
110, 112, 120, 121, 123, 128,
136, 139-141, 143, 154, 401,
402, 408, 409, 413, 419
Skinner, M. F., 436, 468
Skjolsvold. A., 411, 416
Smiley, T. L., 413
Smith, C. L., 440, 468
Smith, H. M., 453, 454, 459, 461,
468
Smith, P. W., 74, 79,389,419
Snyder, J. O., 210, 211, 222
Soday, F. J., 394, 419
Spieker, E. M., 20, 59
Statz, G., 303, 320
Stearns, C. E., 391, 419, 436, 468
Stebbins, G. L., Jr., 100, 101, 128
Stebbins, R. C, 160, 162, 171,
178, 179, 186, 450, 457, 468,
475, 476
Stewart, O. C, 395, 419
Stille, H., 54, 59
Stirton, R. A., 194, 222, 301
Stock, C., 129
Stovall, J. W., 106, 129
Strain, W. S., 444
Stuart, L. C., 393, 417
Swanson, V. W., 59
Taliaferro, N. L., 17, 18, 53, 60,
164, 186
Taylor, E. H., 454, 459, 468
Taylor, W. W., 394, 419
Tharp, B. C., 72, 79, 381, 418,
435, 468
Theobald, N., 259
Thomas, E. W., 376, 419
Thorson, T. B., 86, 89, 95
Tillyard, R. J., 254, 259
Troll, C., 375, 415
Tucek, C. S., 414
Ulmer, G., 232, 252
Underwood, E. J., 88, 95
Ureta, E., 368
Urey, H. C., 72, 79
Usinger, R. L., 104, 128
Uyeno, T., 215, 221
Van Dyke, E. C, 309, 313, 320
Van Frank, R., 160, 162, 186
Van Houten, F. B., 25, 27, 28, 40,
41, 43, 60, 109, 112, 129
Vaurie, C., 431, 432
Vogt, G. B., 320
Wadia, D. N., 74, 79
Walker, E. M., 289
Wallace, A. R., 97, 307, 320
Wallace, R. E., 53, 60
Wallgren, H., 86, 95
Walters, V., 95, 198, 203, 222
Warren, B. C. S., 368
Wasserman, A. O., 454, 468
Waters, A. C., 46-48, 60
Wells, B. W., 381, 419
Wetmore, A., 393, 403, 411, 419,
426, 428, 432
Weyl, R., 392, 419
White, S. E., 392, 420
Whitehead, D. R., 378, 383, 413
Whittaker, R. H., 382, 389, 420
Wickham, H. F., 320
WiUmovsky, N. J., 196
Wilke, F., 90, 94
Willett, H. C., 71, 74, 76-79
Williams, E. E., 409-411, 417, 420
Williams, S., 394, 405, 420
Wilson, J. A., 106, 129
Wilson, L. R., 378, 381, 420
Witthoft, J., 394, 420
Wodehouse, R. P., 66-79
Wolfe, P. E., 382, 420
Wood, H. E., 106, 129
Woodford, A. O., 18, 56, 60
Woodring, W. P., 16, 60
Wormington, H. M., 394, 395,
404, 420
Wright, W. G., 368
486 AUTHOR INDEX
Wynne-Edwards, V. C, 201, 204, Zeuner, F. E., 62, 79, 259, 282,
222 285, 289
Yehle, L. A., 381, 382, 420 Zumberge, J. H., 387, 388, 420
Yepes, J., 136, 137, 153 Zweifel, R. G., 160, 180, 186
Index of Scientific Names-
Abies, 304, 305, 392, 434
Abramidinae, 203
Acacia, 265
Acantherus, 21 S
Acanthocinus, 306
Acanthoderes, 313
Acer, 67, 304, 305
grandidentatiim, 445, 446
saccharum, 445, 446
skutchii, 445
Acheta, 287
assimilis, 287
Achiridae, 189
Achryson surinamuni, 307
Achurum, 274, 275
Acipenseridae, 188
Acmaeops pratensis, 306
Acratocnus, 407
Acreinae, 344, 345
Acrididae, 259-277
Acridinae, 273-277
Acridoidea, 256-277
Acris, 457
crepitans, 457
gryllus, 457
Acrodectes, 282
Acrolophitus, 274
Actinote, 344, 345
Adelpha, 348, 351, 352
Adenostoma, 261
Aeoloplides, 268
Aeria, 337
Aerochoreiites, 272
Aeropedelliis, 273, 274
Aeropus, 273
Aesculus, 376
octandra, 376
Agallisus, 307
Agapetus, 239
^gaz'e, 376
Ageneotettix, 274, 275
Ageronia, 348, 351
Agkistrodon, 377, 389
contortrix, 377, 389
Aglaothorax, 281, 282
Agosia chrysogaster, 215
klamathensis , 211
nubila, 211
ylgrm5, 349, 360
^gm, 351
Agroecotettix, 268
Agymnastus, 270
Aidemona, 268
Ailanthiis, 67, 305
Alaudidae, 429
^Zce, 124
>lZce5, 137, 149, 436
a/ce5, 137
Alesa, 353
Alnus, 304
yl/o/>g.v, 124, 137, 148
la go pus, 137
Amauronematus, 243
Amblycorypha, 278
Amblygonia, 354
Amblyrhiza, 409
Amblytropidia, 274
Ambrosia, 377, 378
Ambystomidae, 161
Amelanchier , 304
Amelinae, 292
Amiidae, 218
Ammobaenetes , 284
Amphibia, 85, 475
Amphidecta, 338, 339
Amphipoda, 227, 228
Amphitornus, 274
Amphiunia, 455, 463
^wyzow, 193, 202
Anabrus, 280, 281
^«am, 349, 351
Anagapetus, 237, 238
bernea, 238
chandleri, 238
debilis, 238
hoodi, 238
Anaglyptini, 308
Anaptomorphidae, 110
487
488
INDEX OF SCIENTIFIC NAMES
Anartia, 346
Anas crecca, 423
penelope, 423
Anaxipha, 288
Anconia, 272
Ancylocera, 307
Ancylusis, 353
Andina, 332, 334, 359
Andrias scheuchzeri, 101
Anechiirella, 255
t;ara, 255
Anefltis, 313
Aneides, 450, 463
hardyi, 450
lugubris, 171, 172, 183
Anepsyra, 313
Anisolabis, 254
Anniella pulchra, 172
Anoplodera, 302, 306
Anoplodusa, 281
Anostraca, 227
^w/eo5, 331, 333
Anthocharis, 332, 334
Antilocapra, 124, 139, 149, 408
Antilocapridae, 121, 122, 133, 152
Antirrhaea, 337, 338
Antrozoiis, 125
Aphelocoma, 445
coeriilescens, 445
Aphredoderidae, 193, 197, 198
Aplodonfia, 125, 149
Aplodontidae, 121, 122, 146
Apodemia, 352, 354
^/>ote, 281
Appalachia, 266
Appias, 331, 357
Aprotopos, 336
Arbutus, 305
Archidermaptera, 254
Archodontes, 307
Archonias, 331
Archoplites, 199, 219
interruptus, 200
Arctocyonidae, 110
Arctostaphylos, 261, 306
Arenivaga, 297
Arethaea, 277, 278
Argiacris, 267
^rg3'«m"5, 346, 350, 364, 365
Argyrophorus, 341, 343
Argytes, 284
Arhopalus, 306
rusticus, 306
Ariidae, 188
Artemesia, 37, 313
Artiodactyla, 116, 117, 119
Ascia, 331, 333
Aseminae, 306
Asemoplus, 269
A senium , 306
striatum, 306
Asinus, 399
conversidens, 399
Asio flammeus, 426
fiammeus bogotensis, 426
flammeus suinda, 426
Astacinae, 227
Asterocampa, 348, 351
Astraeodes, 354
Astyanax fasciatus, 195
Ataxia, 313
Atelopus, 281, 282
Atherinidae, 189, 195
A thesis, 332, 335
Athripsodes, 245
cancellatus, 225
tarsipunctatus, 245
Athyrtis, 336
Atimia helenae, 311
maritima, 316
Atlanticus, 280, 282, 290, 297
^//a, 296
Attaphila, 296
Attaphilinae, 296
Atyidae, 225
Aulocara, 274
^z;g5, 472
Aztecacris, 268
Baeotis, 354
Baiomys, 124, 149
Balboneura, 347, 351, 352, 360
INDEX OF SCIENTIFIC NAMES
489
Barbicornis, 353
Barisia, 393
Baronia, 328, 330, 343, 358
Barytettix, 268
Basilarchia, 348, 351
Bassariscidae, 150
Bassarisais, 125, 148
Batesia, 348, 352, 360
Bathyyiella, 225
Batrachideinae, 259
Batrachoseps, 161, 179, 181, 183,
184
attenuatus, 179, 180, 184
leucopHs, 179
major, 179
pacificus, 179, 180, 184
wrighti, 179
5a/3;/g, 313
Bellamira, 309
fig/z</a, 304, 305
5ia, 345
Bison, 124, 149, 398, 399, 404, 408
alleni, 398
antiqmis, 398, 399
crassicornis, 398, 404
Blarina, 125, 148
Blasticotoma, 233
fi/a//a, 294
Blattella, 294
Blattoidea, 294-298
''Boanerges'' internigrans , 427
Bomhycilla cedrorum, 429
garrulus, 429
japonica, 429
Bombycillidae, 429
Boopedon, 274
Bootettix, 275
Bootheriiim, 408
Boreostracon, 442
Borophagus, 401, 402
Bothidac, 188
Bovidae, 121, 122, 147
Brachyinsara, 277
Brachyphylla, 410
Brachystola, 262, 263
Bradynotes, 268, 269
Brassolidae, 322, 324, 325, 344,
345, 357-359, 362
Brassolis, 345
Breagyps, 403
Breameryx, 401, 408
Brephidium, 355, 356, 360
Brothylus, 311
Brunneria, 270, 274, 276, 293
borealis, 293
Bryodema, 212
Bryozoa, 226, 228
Buckellacris, 268, 269
Bm/o americamis, 457
boreas, 170
fowleri, 453
hoiistonensis, 459
microscaphus, 170, 173
querciciis, 459
terrestris, 457
woodhousei, 445, 453, 462
Biimelia, 305
Cactaceae, 313
Cadomastax, 261
Caelifera, 256-277
Caenophlebia, 360
Calcarius lapponicus, 431
Caligo, 344, 345
Calippus, 396
Ca//iVo, 341, 343
Callicore, 348, 351
Callidiellum ciipressi, 311
rtifipenne, 311
villosulum, 311
Callidini, 311
Callidinm, 306
senipervirens, 311, 312
seqttoiae, 311
vandykei, 311, 312
Callimellum, 309, 311
Callimoxys, 302
Callitaera, 337, 338
Callithea, 348, 351, 360
Callithemia, 336
Callizona, 347
Calloleria, 336
490
INDEX OF SCIENTIFIC NAMES
Callorhinus ursinus, 89
Calydna, 354
Cambarinae, 227
Camelidae, 133
Camelops, 399, 401, 408
Camelus dromedarius, 87
Camnula, 270
Campo stoma, 204
ornatum, 214
Camptocercus, 226
Campylacantha, 267
Canidae, 121, 122, 145
Canis, 108, 124, 137, 148, 399
dims, 399
lupus, 137
Capnobotes, 281, 282
Capromys, 408, 410, 411
ingrahami, 408, 410
thoracatus, 410
Carinifex, 227
Carnivora, 110, 116-118
Carpinus, 305
Carpiodes, 202
Carpodaptes aulacodon, 110
Carpolestidae, 110
Carya, 303, 305
Castanea, 305
Castanopsis, 67, 304
Ca5/or, 120, 124, 049
Castoridae, 120-122, 146
Castor oides, 401, 412
Catagramma, 348
Catargynnis, 342
Catastica, 331, 333, 357
Cathartornis, 403
Catonephele, 347
Catostomidae, 188, 193, 195, 201-
203, 205, 212, 219
Catostominae, 201
Catostomini, 201, 202
Catostomus, 201, 202, 214, 215
ardens, 212
bernardini, 215
catostomus, 199, 203, 212, 218
columbianus, 212
rimiculus, 211
snyderi, 210
warnerensis, 216
wigginsi, 214
Ceanothus, 302, 306
Ce(/re/a, 69, 70
Celastrus, 67
Celtis, 305
Centrarchidae, 188, 193, 195, 199,
200
Centropomidae, 188
Centropomus, 214
Cerambycidae, 299-320, 474
Cerambycinae, 306, 307
Ceratinia, 336
Cercidiphyllum, 305
Cercyonis, 341, 343
Cerocarpus, 306
Cervalces, 400
Cervidae, 121, 122, 147
Cem/5, 149, 396, 441
Ceuthophilini, 284-285
Ceuthophilus, 284-285
Chalmytherium, 403
Chamaecyparis , 304, 311
obtusa, 311
villosulum, 301
Chamaelimonas, 353
Characidae, 195
Charts, 352, 354
Charisalia, 309
Chasmistes, 202, 212, 213
Cheimas, 342
Cheleutoptera, 289, 290
Chelisoches, 254
Chimarocephala, 270
Chimarra, 235
Chion, 307
Chiroptera, 103, 116-118
Chirostoma, 195
Chloealtis, 273
Chlorippe, 348, 351
Chloroplus, 268
Chlosyne, 346, 351
Choeronycteris, 125
Chorisoneurinae, 296
Chorisoneura texensis, 296
INDEX OF SCIENTIFIC NAMES
491
Chorthippus, 273
longicornis, 273
Chortophaga, 270
Chriacus sp., 110
Chrysochraon, 273
Chrysophanus, 355, 356
Chrysothamnus, 313, 317
Cibolacris, 271
Cichlidae, 188, 195, 205
Cichlasoma beani, 205, 214
cyanoguttatum, 195
Cincindelidae, 316
CircoteUix, 272
Citellus, 108, 125, 137, 146, 148,384
richardsoni, 438
iindtilatus , 137
undulatus parryi, 384
Cladocera, 226, 228
Clematodes, 265
Clemmys guttata, 461
C/e/Z^m, 305
Clethrionomys, 124, 137, 149, 384
rutilus, 137, 384
Clidomys, 409
Clinopleura, 282
Clothilda, 344, 346, 360
Clothildinae, 344, 346
Clupeidae, 188
Clytanthus, 308
Clytoleptus, 309
Clytus, 306
blaisdelli, 312
clitellarius, 312
planifrons, 312
Cnemidophorus, 445
sexlineatus, 445
Cnemotettix, 283
Coelenterata, 228
Coenonympha, 340, 343
Coenophlebia, 349, 352
Coenopus, 313
Coerois, 337, 338
Colaenis, 344, 345
Colias, 331, 333, 361-365
6e/in, 363
eurytheme, 361-363
hecla, 363
interior, 362, 363
nastes, 363
palaeno, 363
philodice, 362
Columba, 427
fasciata, 427
Columbia, 197, 219
transmontana, 198, 211
Columbidae, 427
Compositae, 68, 313
Compsodes, 296
Conalcaea, 268
Concho straca, 227
Condylarthra, 110, 116-118
Condyliira, 125, 148
Conepatus, 124, 145, 148
Coniana, 272
Conocephalinae, 279, 280
Conocephaliis, 279, 280
Conozoa, 272
Copepoda, 228
Copiphorinae, 279
Corades, 345
Coragyps, 399
occidentalis, 399
Cordillacris, 274
Coregonidae, 187, 188, 212
Coregonus clupeajormls, 211
Cornus, 304
Cortodera, 309, 311
Corvidae, 425, 427, 428
Corvus, 428
corax, 428
Corydinae, 296
Corynorhinus, 125, 459
Cosmosatyrus, 341, 343
Cottidae, 189, 193, 212
C0//M5, 187, 208, 210, 211, 213
annae, 208
&atV^^, 208, 212, 213, 218
beldingi, 212
princeps, 210, 211
tenuis, 211
Covillea, 275, 277
tridentata, 263
492
INDEX OF SCIENTIFIC NAMES
Crataegus, 305
Cratogeomys, 124, 149
Craty pedes, 270
Cremna, 349
Crenichthys, 207, 217
baileyi, 217
nevadae, 206, 217
Cricetidae, 121, 122, 146
Cricetinae, 146
Crossidius, 313
Crotalus adamanteus , 445, 447
atrox, 457
horridus, 452
ruber, 457
Crotaphytus wislizenii, 174
wislizenii silus, 174, 175
Cryptocerous, 258, 267, 281, 297
Cryptomeria japonica, 311
CryptophylUcus, 282
Cryptotis, 125, 148
Cuculidae, 427
Culicoides, 245
ohsoletus, 245
tristriatulus, 245
Cunninghamia lanceolata, 311
Cupressaceae, 302, 311
Cupressus, 305, 390, 392
sargentii, 311
Cuvieronius, 405
Cybielis, 348, 351, 360
Cycleptinae, 199, 202
Cycleptus, 199, 201, 202
Cy do gramma, 348, 351
Cyllopsis, 340, 343
Cycloptilum, 286
Cynomys, 124, 146, 148
Cyphoderris, 283
Cyprinidae, 188, 193, 195, 203-
205, 212, 219
Cypriniformes, 191
Cyprinodon, 207, 209, 213
Cyprinodontidae, 188, 193, 205,
206, 212, 213
Cyrenia, 353
Cyrtacanthacridinae, 263-269
Cyrtacanthacridini, 263-265
Cyrtinus, 308
Cystineura, 347, 351
Cytrophorus, 308
Dactylotum, 267
Daedalma, 342, 343
Daihinia, 284
Daihiniella, 284
Daihiniodes, 284
Z)a//ia, 196, 197
Danaidae, 322, 324, 325, 332,
335-337, 357-359, 361
Danainae, 332, 362
Danais, 332, 335
plexippus, 362
Dasyophthalma, 345
Dasypodidae, 121, 122
Dasypterus, 459
Dasypus, 125, 442
novemcinctus, 122
Davisonia, 244
Decapoda, 228
Decticinae, 280-282
Decticita, 282
Dendrobias, 313
mandibularis , 307
Dendromecon, 306
Dendrotettix, 266
Dermaptera, 254-256, 299, 471
Derobrachus, 313
Derotmema, 270, 271
piute, 271
Dermoptera, 103, 116, 117, 126
Desman, 108
Desmocerus auripennis, 312
cribripennis, 312
Diadophis, 389
amabilis, 175
punctatiis, 389
Diapheromera, 291, 292
Dicamptodon, 161
Dicentrus, 311
Dichopetala, 278
Dichromorpha, 270, 276
Dicosmoecus, 235
Dicrostonyx, 124, 137, 149, 384
INDEX OF SCIENTIFIC NAMES
493
Dictyoptera, 289, 292
Didelphidae, 110, 120-122
Didelphis, 120, 125, 148, 407
marsupialis, 89, 452
Didelphoidea, 100
Didolodontidae, 119
Didonis, 346, 351
Diemictylus , 463
meridionalis, 454
viridescens, 454
Dinocerata, 116, 117, 119
Dione, 344, 345
Diophthalma, 349
Dioriste, 342
Dipodomys, 124, 139, 149, 151
Dipoides, 108
Dipteronia, 67
Dircenna, 336
Dismenitis, 337
Dismorphia, 332, 335
Dismorphiinae, 330, 332, 335
Dissacus, 110
Dissosteira, 271
Docodonta, 116, 117, 119, 120
Dolerus, 243
Doloclanes, 233, 235
Dolophilodes, 234
Dorcaschema, 308
Dormitator, 214
Dorosoma, 187, 214
r)om, 254, 255
acideatum, 255
davisi, 255
lineare, 254, 255
Dracotettix, 262, 263
Drepanopterna, 274
Drucina, 342
Drymarchon carats, 455
Dryobius, 302, 303
Dulidae, 429
Dynamine, 348, 351
Dynastor, 345
Eburia, 307
EccUsomyia, 234
Ectypodus musciilus, 110
Ecyrus, 307
Edentata, 116-118, 126
Elaphe obsoleta, 459
Elaphidion, 307, 313
Elasmodontomys , 407, 409
Elatrotrypes, 312
Eleotridae, 189
Eleotris, 208
£/twa, 341, 343
Elopidae, 188
£Zo^5, 208
Elytroleptus, 313
Embiotocidae, 189, 209
Embrithopoda, 120
Emesis, 354
Empetrichthys, 206, 207, 213
Encoptolophus, 270
Efiodia, 338, 339
Ensatina, 162, 171, 180, 181
eschschoUzii, 178
eschscholtzii croceator, 178
eschschoUzii eschscholtzii, 178
eschscholtzii klauberi, 178
eschscholtzii oregonensis, 178
eschscholtzii platensis, 171, 178
eschscholtzii xanthoptica , 171,
178
Ensifera, 277-292
Entosphenus tridentatus, 210
Ephedra, 66, 378
Epinephele, 341, 343
Epiphile, 347
Episcada, 337
Epithomia, 336
Eptesicus, 125
fuscus, 122
£gMW5, 396, 399, 401, 408
excelsus, 399
£re&ia, 341, 343
Eremiacris, 274
Eremoblatta, 297
Eremopedes, 281, 282
Eremophila alpestris, 429
Erethizon, 124, 149, 396, 407
dorsatum, 440, 442
Erethizontidae, 121, 122, 151
494
INDEX OF SCIENTIFIC NAMES
Eretris, 342, 343
Ergates, 309
Erimyzon, 202
Erimyzontini, 202
Eritettix, 276
Eroessa, 332, 334, 359
Erolia ferruginea, 424
Erycinidae, 322, 324, 349, 352,
353-358, 360
Eryphanis, 345
Erythroneura, 239
Esocoidei, 196
Esox, 218
lucius, 218
musquinongy , 440
Esselenia, 276
Eteona, 342, 343
Etheostomatinae, 219
Etima, 348
Euarctos, 137
Euhorellia, 254
Eubranchiopoda, 228
Euceratherium, 399, 401, 408
coUinum, 399, 441
Eucheira, 328, 330, 358
Euchloe, 332, 334
Euchloinae, 330, 332, 334, 359
Eucrossiis, 313, 315
Euderces, 307
Euderma, 125
Eudis tenia, 315
Eulides, 344, 345
Eumaeus, 355, 356
Eumastacidae, 259-261, 290
Eumeces, 452
anthracinus, 454
gi/6er/i, 181, 182
lagunensis, 182
septentrionalis , 454
skiltonianus, 181
Eumichthus, 311
Eumops, 125, 459
perotis, 122
Eumorsea, 260, 261
Eunica, 348, 351
Eupnigodes, 276
Eupogonius, 307
Euptoieta, 346, 350
Euptychia, 326, 338-340, 343
Eurema, 331, 333
Euryades, 328, 330, 358
Eurybia, 349
Eurycea, 450, 463
tynerensis, 450
Euryptera, 307, 313
Euselasia, 349
Eutamias, 124, 137, 146, 148
Eutheria, 118, 119, 126
Eiithlastohlatta, 295
Eutresis, 332
Everes, 355, 357
Evodinus vancouveri, 312
Exbucklandia, 67
Eysenhardtia, 305
Fagus, 305
Fariila, 234
Faunula, 341, 343
Felidae, 121, 122, 145
/?e/i5, 108, 125, 141, 145, 148
concolor, 145
Feniseca, 355, 356
Flourensia, 275
Fluminicola, 227
Fores tier a, 305
Forficula, 254
Fraxinus, 304, 305, 452
Fremontia, 306, 315
Fumonta, 234, 235
Fundulus, 207, 213, 214
Ziwa, 215
nevadensis, 193
parvipinnis, 215
Gadidae, 188
Galbula ruficauda, 92
Galeichthys, 214
Galloisiana, 289
Gammarotettix, 284
Garrya, 306
INDEX OF SCIENTIFIC NAMES
495
Gasterosteidae, 189, 193
Gasterosteus, 214
doryssus, 193
Gastropoda, 228, 229
Gastrotrlcha, 225, 228, 229
GauUheria, 304
Gaurotes, 302, 309
Geocapromys, 408, 410, 411
Geomyidae, 121-133, 150
Geomys, 124, 149
bur sarins, 454
pinetis, 445, 454
Gerrhonotus coerulus, 175-177
coerulns coeridus, 176
coerulus palmeri, 176
coerulus principis, 176
coerulus shastensis, 176
kingi, 176, 177
muUicarinatus , 175, 177
multicarinatus nmlticarinatus,
176, 077
multicarifiatus scincicauda, 177
multicarinatus webbii, 176, 177
Gi/a, 193, 194, 204, 205, 207, 210,
213, 217
atraria, 212
bicolor, 210
ditaenia, 214, 215
minacae, 215
nigrescens, 214
orcutti, 214, 215
purpurea, 214, 215
robusta, 205
Gillichthys, 208
Ginkgo, 305
Glaucomys, 124, 139, 146, 148
volans, 452
Glaucopsyche, 355, 357, 364
Glaiicotes, 313
Glossosoma, 237, 241, 250, 251
alas cense, 250
parvulum, 250
penitum, 241
[Ripaeglossa) spp., 251
traviatum, 250
Glossosomatidae, 237
Glycobius, 309
Glyptostrobus, 67
Glyptotherium, 408
Gnathotriche, 346, 351, 352, 360
Gobiidae, 189
Gomphocerus, 273
Gomphomastacinae, 261
Goniatron, 275
Goodeidae, 195
Gopherus, 457
agassizi, 457, 458
berlandieri, 457, 458
polyphemus, 457, 458
Grammoptera, 302, 306
Graptemys, 459
geographica, 459
pseudogeographica, 459
Gruidae, 426
Gni5, 426
Gryllacrididae, 282-285
GrylHdae, 285-288
Gryllinae, 287
Gryllita, 287
Grylloblatta, 283, 289, 290
campodeiformis , 290
Grylloblattidae, 289-290
Grylloblattina, 289
Grylloblattoidea, 289-290
Grylloidea, 285-288
Gryllotalpa, 285
gryllotalpa, 285
Gryllotalpidae, 285
Gryllulus, 287
Gm/o, 124, 137, 148
gM/o, 137
Gymnotidae, 195
Gynaecia, 347
Gyrocheilus, 341, 343
Haballia, 331
i?a(/e5, 349
Hadrotettix, 271
Haematera, 348, 351, 360
Haetera, 337, 338
496
INDEX OF SCIENTIFIC NAMES
Hamamelis, 305
Hamearis, 354
Haplidus, 313, 315
Haplomi, 196
Hebardacris, 269
Heleioporus, 89
Heliastus, 269, 272
Heliaula, 273
Heliconiinae, 344, 345
Heliconius, 344, 345
Helicopsis, 349
Helicopsyche, 246, 248
borealis, 246, 248
limnella, 248
mexicana, 246, 248
piroa, 248
planata, 248
selanderi, 248
vergelana, 246, 248
Hemiargiis, 355, 356
Hemidactylium, 463
Henicinae, 283
Heptaxodon, 407
Hermathena, 349
Hesperanoplium, 315
Hesperiidae, 321
Hesperocharis, 332, 334
Hesperoleucus, 216
Hesperophanes, 308, 309
Hesperotettix, 268
Heterachthes, 307
Heteromyidae, 87, 121, 122, 133,
150
Heteronemiinae, 291-292
Heteropsomys, 407
Heterosais, 337
Heteroscada, 336
Hetoemis, 308
Himalopsyche, 241, 242
phryganea, 241, 242
spp., 242
Hipparion, 108, 396
Hippidium, 396
Hippiscus, 270
Hippopsis, 307
Hirsutis, 336
Hirudinea, 225, 228
Historis, 347, 351
Holmesina, 442
Holmskioldia, 67
Holo pleura, 311
Homaesthesis, 312
Hominidae, 121, 122, 145
ilowo, 124, 475
Homopsomys, 407
Hoplosphyrum, 286
Horesidotes, 275
Hybodera, 311
Hybognathus, 204
hankinsoni, 211
Hybopsis, 204
plumbea, 211
Hydracarina, 226, 228
Hydrangea, 305
Hydrobiosella, 235
Hydrochoerus, 396, 442
Ho'/a, 452
andersoni, 461, 462
arenicolor, 173, 456, 457
cinerea, 460, 461, 462
crucifer, 462
femoralis, 456, 457
gratiosa, 459
ocularis, 459
phaeocrypta, 459
regilla, 183
sguirella, 462
versicolor, 453, 462
Hylos, 355, 356
Hymenitis, 337
Hyopsodontidae, 119
Hypanartia, 346
Hypentelium, 202
Hypna, 349
Hypochlora, 267
Hypocolius, 429
Hypolagus, 108
Hypoleria, 337
Hyposcada, 336
Hyracoidea, 120
INDEX OF SCIENTIFIC NAMES
497
Hyracotherium, 396
Hysterocarpus, 187
traski, 209
Ihidion, 307
Ictaluridae, 188, 193, 195, 197
Ictalurus, 194, 197
meridionalis , 195
pricei, 214, 217
Ictiobinae, 199, 202
Ictiohus, 199, 202
meridionalis, 195
Idionotus, 282
Idionycteris, 125
Idiostalus, 281, 282
Iguanidae, 162
//ex, 305
Imelda, 352, 354
Indioneura, 341, 343
Insara, Til
Insectivora, 110, 116-119
Insects, 474
Invertebrata, 474
Ipochus, 315
fasciatus, 316
Ischnoptera, 295
deropeltiformis, 295
rw/a occidentalis, 295
Isolohodon, 407
Isopoda, 227, 228
Ithnonees, 353
Ithomia, 336
Ithomiinae, 362
Ithomiola, 353
I tuna, 332
Judolia qiiadr ilium, 312
sexmaculata, 306
Juglans, 305
Juniperus, 447
Junonia, 346
Kapis, 353
Kenkia, 225
Keteleeria, 305
Kinosternon, 459
Kisaiira, 235
Koelreiiteria, 67
Kricogonia, 331, 333, 334, 359, 360
Labia, 254
Labidolemur soricoides, 110
Lahidura, 254
Lactista, 271
Lagocheirus , 307
Lagochila, 201, 202
Lagomorpha, 116, 117, 119
Lagurus, 124, 149
Lamiinae, 306, 307
Lampropeltis zonata, 175
Laniidae, 429
Lanius, 428
excuhitor, 430
ludovicianus , 430
Larix, 435
Larus fuscus, 424
minutus, 424
occidentalis, 90
ridibundus, 424
Lasaia, 354
Lasionycteris, 125
Lasiophila, 342
Lasiurus, 125, 459
borealis, 122, 459
seminolus, 459
Latiblattella, 295
Lea, 279
Leguminosae, 307, 317
Leiopus, 307, 309
Lemmus, 124, 137, 149, 384
Lemonias, 354
Leodonta, 331, 359
Lepidomeda, 209
Lepidoptera, 321-368, 474
Lepomis, 194
Leporidae, 121, 122, 147
Lepricornes, 353
Leprus, 270
Leptacodon tener, 110
Leptalia, 311
498
INDEX OF SCIENTIFIC NAMES
Leptictidae, 110
Leptocottus, 210
Leptonycteris, 125
Leptophobia, 331
Leptostylus, 302, 303, 307, 309
nehulosus, 312
Leptotes, 355, 356, 357
Leptura, 302, 306
ohliterata ohliterata, 312
ohliterata soror, 312
Lepturges, 307, 309
Lepturinae, 306, 307
Leptysma, 263, 264
Leptysmini, 263-264
Lepus, 124, 149
americanus, 440
townsendi, 441
Leucidia, 331, 359
Leuciscinae, 203
Leuciscus rosei, 193
turneri, 194
Leucothyris, 336
Lihocedrus, 304
Libythea, 349
Libythina, 348, 352, 360
Ligurotettix, 275
L*7g, 214
Limenitis, 348, 351, 352, 363, 364
arthemis, 363
astyanax, 363
Limnephilus, 250
sublunatus, 250
Limnodromus griseus griseus, 425
hinder a, 305
Liodontia, 108
Liolaemus multiformis, 85
Liomys, 149
Liotettix, 256
Liquidambar, 305, 376
Lissonotus flavocinctus, 307
Listroscelinae, 280
Litaneutria, 292
Lithocarpus, 304
Litoscirtus, 263
Lophopo gonitis, 311
Zoto, 187
Loxia curvirostra, 92
Lucinia, 347, 351, 352, 360
svecica svecica, 422
Li^/m, 125, 137, 141, 148
Lycaenidae, 322, 325, 352, 355-
358, 360
Lycaeniopsis, 355, 357
Lycorea, 332
Lycoreinae, 332, 335
Lymanopoda, 342
Lymnas, 353
L^/wx, 124, 137, 148
Lyonothamnus , 305
Lype, 232
phaeopa, 232
sericea, 232
Lyropteryx, 353
Machairodus, 108
Madura, 444
Macneillia, 276
Macrosteles, 243, 244
ssp., 244
Macrotus, 125
Magnolia, 376
Mahonia, 304
Mammalia, 233, 475
Mammur, 400
Mammut, 407
Mammuthus, 398, 399, 401, 407
columbi, 398, 399
imperator, 404
Manerebia, 341, 343
Manomera, 292
Manteinae, 292-293
Mantoidea, 292-293
Margaritifera margaritifera, 227
Marifugia, 225
Marmota, 108, 125, 146, 148, 391,
396, 412, 436
flaviventris, 412, 436, 441
Marsupialia, 110, 115-117, 126
ikfar/e^, 108, 125, 137, 148
pennanti, 440
INDEX OF SCIENTIFIC NAMES
499
Masticophis flagellum, 460
Mecas, 313
Mechanitinae, 332, 335-337
Mechanitis, 336
Megacyllene, 302, 303, 307, 312
Megalonyx, 408, 442
Megalura, 347, 351
Meganoplium, 315
Megaphasma, 291
Megascheuma, 312
Megasemum, 311
Megatherium, 442
Megistanis, 347, 360
Megohrium, 315
edwardsi, 316
Melanoplini, 263, 265-269
Melanoplus, 267
Me/e/e, 331
Melinaea, 336
Meliosma, 70
Melitaea, 346, 350, 364
Meniscotheriidae, 119
Mephitinae, 145
Mephitis, 124, 145, 148
Mermiria, ll'^-llS
texana, 274-275
Mesene, 353
Mesochloa, 276
Mesohippus, 396
Mesonychidae, 110
Mesosemia, 349
Mesosini, 311
Mestobregma, 271, 272
Mestra, 347
Metacharis, 354
Metaleptus, 313
Metamorpha, 344, 345, 360
Metasequoia, 61, 67, 305
Metator, 271
Methia, 313
Methonella, 349
Metrioptera, 281
ussuriana, 281
Michythisoma, 308
Microcentnim, 277
Microclytus, 308
Microdipodops, 124, 149
Microhyla carolinensis, 445, 447,
452, 453
olivacea, 453
Microsorex, 125, 148, 440
pratensis, 438
Microtes, 271
Microtia, 346, 351
Microtinae, 121, 146
Microtus, 124, 137, 149, 384
llanensis, 438
longicaudus, 441
micrus, 384
oeconomicus, 137, 384
operarius, 438
paraoperarius, 438
pennsylvanicus , 440
Minytrema, 201, 202
Miogryllus, 287
Miohippus, 396
Miraleria, 337
Mogoplistinae, 286
Mohavacris, 260
Moina, 226
Molossidae, 121, 122
Molothrus, 403
Moneilema, 313
Monochamus, 306
Monotremata, 120
Mormoops, 125
Morpheis, 346, 351, 352, 360
Morphidae, 322, 324, 325, 335,
337, 338, 357, 358
Morpho, 335, 337, 338, 358
Morsea, 260, 261
Morseiella, 274
Morseinae, 261, 290
Motacilla flava tschiitschensis, 422
Motacillidae, 422
Moxostoma, 199, 201, 202
Moxostomatini, 201, 202
Mwgi/, 208
Mugilidae, 189
MuUituberculata, 110, 116, 117
500
INDEX OF SCIENTIFIC NAMES
Muridae, 121, 122
Mils, 124, 407
Mustela, 125, 137, 141, 148
erminea, 137, 440
nivalis, 137
Mustelidae, 121, 122, 145
Mygona, 342
Mylocheilus, 205
Mylocyprinus, 205
Mylodon, 398
Mylopharodon, 204, 205
My Otis, 125
Myrica cerifera, 452
Myrmecophila, 286
Myrmecophilinae, 286
Myscelia, 347, 351
Myxocyprimis, 199, 201, 202
Nahida, 353
Nannippus, 396
Napaeozapiis, 125, 149
Napaia, 273
Napeodes, 346, 360
Napeogenes, 336
Narope, 345
iVa5i/a, 148, 150
Nathalis, 331, 334, 359, 360
iVa^nx, 389, 452
er y thro gas ter, 389
sipedon, 452, 461
taxispilota, 459
Navajovius kohlaasae, 110
Necydalis harbarae, 316
laevicollis, 312
Necyria, 353
iVe^w&a, 281, 282
Nematoda, 225, 228, 229
Nematus, 243
Nemobiinae, 286-287
Nemohius, 286-287
fasciatus, 286
Neobarrettia, 280
Neobatrachus, 89
Neobellamira, 315
Neochoerus, 442
Neoclytus, 307, 309
caprea, 312
miiricatulus , 307
nubilus, 307, 312
Neoconocephalus, 279
Neocurtilla, 285
Neodiprion, 239, 240
spp., 240
Neofiber, 125, 149, 407, 442, 464
alleni, 443
Neogyps, 403
Neohipparion, 108
Neomaenus, 341, 343
Neominois, 340, 343
Neophasia, 328, 330
Neophrontops, 403
Neosatyrus, 341, 343
Neostylopyga, 294, 295
rhombifolia, 294-295
Neotettix, 256
Neotoma, 124, 149
cinerea, 441
floridana, 445, 454
micropus, 454
Neoxabea, 288
Nesophontes, 409
Nessaea, 347
Neurotrichus, 125, 148
Nisquallia, 268
Notemigonus, 203
Nothrotherium, 398, 403, 408, 444
shastense, 398
Notiosorex, 125, 148
Notoptera, 289
Notostraca, Til
Notoungulata, 116, 117, 119
Notropis, 204
formosus, 215
mearnsi, 214, 215
ornatus, 214
Novumbra, 195, 196, 219
/?M&&5i, 196, 211
Nyctea scandiaca, 426
Nymphalidae, 322, 324, 325, 344-
352, 357, 358, 360
INDEX OF SCIENTIFIC NAMES
501
Nymphalinae, 346-349, 350-352
Nymphalis, 346, 351
Nymphidium, 354
Nyssa, 305
Oberea, 308, 309
quadricallosa, 308
Ochetotettix, 256
Ochotona, 108, 125, 149
Ochotonidae, 121, 122, 147
Odobenus, 436
Odocoileus, 125, 139, 149, 408
Oecanthinae, 287-288
Oecanthus, 288
californicus, 288
Oedaleonotus, 268
Oedipodinae, 269-273
Oeme calif or nica, 312
Oenanthe oenanthe leucorhoa, 422
oenanthe oenanthe, 422
Oe«m, 341, 343, 364
OHgochaeta, 225, 228, 229
Oligonicella, 293
Oligonicinae, 293
Olyras, 332
Omiis, 316
Oncideres, 307, 313
Oncorhynchus , 216
Ondatra, 124, 149
Onychomys, 124, 149
Oothecaria, 289, 292-298
O^em, 274
Opheodrys, 389
aestivus, 461
vernalis, 389, 461
Ophiosaiiriis, 452, 462
Ophistomis, 307, 313
Opshomala, 264
Opsihanes, 345
Opsimus, 311
Opuntia, 255
Orchelimum, 279
Oreamnos, 124, 147, 149
Oreopedes, 282
Oressinoma, 340, 343
Orphulella, 274
Ortholeptura, 311
insignis, 316
Orthoptera, 256-299, 474, 476
Oryzomys, 124, 149, 410
Osmeridae, 188
Osmidiis, 313
Ostariophysi, 191
Osteoborus, 108
Ostracoda, 226, 228
05/r3'a, 305
0yi&05, 124, 149, 384, 436, 437
Oz;i5, 124, 149
Oxeoschistus, 342
Pachymorphinae, 291
Pachyta armata, 312
lamed, 306
Pachythone, 353
Palaeoesox, 197
Palaeospizidae, 428
Paleotaricha, 160, 161
Paliurus, 67
Panacea, 348, 351, 360
Panarche, 342
Panchlora, 296
cubensis, 296
Panchlorinae, 296
Pandanaris, 403
Panesthiinae, 297
Pantodonta, 116, 117, 119
Pantosteus, 201, 207, 216, 218
platyrhynchus , 211, 212
plebeius, 214
santaanae, 215
virescens, 212
Pantotheria, 116, 117, 119
Papatemyidae, 110
Papilio, 326-330
Papilionidae, 322-330, 357, 358
Parabacillus, 291
Paracyrtophyllus, 279
Parahippus, 396
Paraidemona, 268
Paramecera, 340, 343
502
INDEX OF SCIENTIFIC NAMES
Paramylodon, 408, 442, 444
Paranoplium, 315
Parapholyx, 227
Parascalops, 125, 148
Paratettix, 258-259
aztecus, 258-259
cucullatus, 258
Paratima conicola, 316
Parcohlatta, 295
americana, 295
bolliana, 295
desertae, 295
fulvescens, 295
notha, 295
pensylvanica, 295
Pardalophora, 270
Parnassius, 326, 328-330
clodius, 328, 330
smintheiis , 328, 330
/^or, 328, 330
Parnes, 354
Parolamia, 303
Paropomala, 274, 275
Parus alricapillus, 431
horealis, 431
Passeriformes, 428
Paulianodes, 234
P axilla, 259
Pecari, 149
Pedaliodes, 342
Pediodectes, 281, 282
Pedioscirtetes, 21 S
Pedomoecus, 235
Pelecanus occidentalis, 90
Pelecypoda, 227, 228, 232
Penetes, 345
Pentacentrinae, 288
Peranabrus, 280, 281
Percaflavescens, 440
Percopsidae, 188, 195, 198
Per cop sis, 197
Pereute, 331
Pma, 347, 351, 352, 360
Periplaneta, 294
Periptychidae, 110, 119
Periptychus, 110
super stes, 110
Perisama, 348
Perisoreus, 427
Perissodactyla, 116, 119, 126
Peritapnia, 313
Perodectes elegans, 110
Perognathus, 108, 125, 139, 149,
151
Peromyscus, 125, 133, 135, 149, 452
6o>'/ei, 447, 448
Comanche, 447
gossypinus, 445, 453
leucopus, 453, 457, 459, 461
maniculatus, 133, 135, 459, 460
melanotis, 460
nasutus, 447
polionotus, 445, 459, 460
sejugis, 460
sitkensis, 460
Perrhybris, 331
Per sea, 69
Petromyzontidae, 188
Phaedrotettix, 268
P/^a/ia, 332, 334, 359
Phaneropterinae, 277
Phasmatoidea, 289, 290-292
Phaulotettix, 268
Phenacodontidae, 110, 119
Phenacodus, 110
gidleyi, 110
grangeri, 110
metthewi, 110
Phenacolemur frugivorus, 110
Phenacolemuridae, 110
Phenacomys, 124, 139, 149, 438
Philibo stroma, 274
Philomachus pugnax, 424
Philopotamus, 235
Philotes, 355, 357
Phoberopus, 284
Phoebis, 331, 333, 363
Phoetaliotes, 267
Pholidota, 120
Photinia, 306
INDEX OF SCIENTIFIC NAMES
503
Photininae, 293
Phoxinus, 205
Phrynotettix, 262, 263
Phyciodes, 346, 350
Phyllostomatidae, 121, 122
Phyllovates, 293
Phylocentropus, 233
Phymatodes, 302
Physocnemum, 308
Pica nuttalli, 428
pica, 428
pica hudsonia, 428
Piceo, 305, 391, 392, 434
Picrodontidae, 110
Pidonia, 302, 303, 306
Pierella, 337, 338
Pieridae, 322, 324, 325, 328, 330-
335, 344, 356, 357-359
Pierinae, 328, 330, 331, 333
Pieris, 328, 333, 358, 364
Pitnephales, 204
promelas, 214
Pinaceae, 303, 306
Pindus, 340, 343
Pinus, 305, 381, 390, 392, 444
atteniiata, 316
hanksiana, 379, 381
holandari, 316
edulis, 447
hartwegii, 392
muricata, 316
radiata, 316
serotina, 379
toeJa, 447
Piodes, 311
Pipistrellus, 125, 459
Pisces, 474
Pistacia, 305
Pituophis catenifer, 453
melanoleucus, 453
Pitymys, 124, 149, 449, 452
meadensis, 438
parvulus, 449
pinetorum, 447, 449
quasiater, 447, 449
Plagiodontia, 410
Plagiostira, 281, 282
Plantes, 474
Platanus, 305
Platygoniis, 408
Platylactista, 271
Platylyra, 277
PlebejHs, 355, 357, 364
Plectrophenax nivalis, 431
Plectrura, 309, 311
spinicauda, 312
Pleocoma, 316
Plesiadapidae, 110
Plesiadapis gidleyi, 110
Plesiogulo, 108
Plesippus, 396
Plethodon, 450, 451, 463
cinereus, 450
glutinosus, 450, 451
neomaxicanus, 450, 451
oiiachitae, 450
Plethodon tidae, 161
Pleuroceridae, 225
Pleuronectidae, 188
Pleuroxus, lid
Plinthocoelium, 307
Plionoma, 313
Pliosaccomys, 108
Pliozapus, 108
Podisma, 266
hesperus, 266
sapporensis, 266
Poeciliidae, 188, 195, 205
Poeciliopsis, 205, 209
Poecilohrium, 311
Poeciloteitix, 268
Pogonocherus, 306
Polaeanodonta, 117
Poliaenus, 315
Polygonia, 346, 351
Polygrapha, 349, 360
Polymastus, 342, 343
Polyodontidae, 218
Polyphaginae, 296-297
Populus, 305, 306, 316
504
INDEX OF SCIENTIFIC NAMES
Porifera, 225, 228
Precis, 346
Prepona, 348, 351
Preptoceras, 399, 401, 408
sinclairi, 399
Primates, 110, 116-118
Prioninae, 307
Priscacara, 199
Pristoceuthophilus, 284
Proboscidea, 99, 116, 117, 119
Proboscis, 342
Procyon, 124, 148
Procyonidae, 121, 122, 147
Procyoninae, 150
Proechymis, 407
Prolabia, 254
Promastax, 259
Pronophila, 342
Prophalangopsidae, 283
Prophalangopsinae, 283
Prophalangopsis, 283
Prorhaphidophora, 284
Prorocorypha, 21 S
Proscopiidae, 260
Prosopium, 208
williamsoni, 208, 212, 218
Prosthennops, 108
Protarra, 234
Protipochus, 303
Protodiplatys, 254
Protoelytroptera, 254
Protogonius, 349
Protogryllinae, 285
Protorthoptera, 282, 289
Protospondylis, 303
Protostrigidae, 425
Protozoa, 225, 228
Prumnacris, 268, 269
Prunus, 305
Psapharochus, 302, 303
Psenocerus, 308
Pseudacris, 377, 389
brachyphona, 377
clarki, 453
mgnto, 389, 453, 461, 462
w. feriarum, 389
n. kalmi, 389
w. triseriata, 389
ornata, 454, 455
streckeri, 454, 455
Pseudomaniola, 341, 343
Pseudomopinae, 295-296
Pseudomops, 295
Pseudonica, 347
Pseudophyllinae, 278-279
Pseudopieris, 332, 335
Pseudopomala, 275
Pseudoscada, 337
Pseudosermyle, 291
Pseudosteroma, 341, 343
Pseudotsuga, 390
P soloes sa, 276-277
Psychomastax, 260, 261
Psyrassa, 307
Pterocarya, 67, 305
Pteromys, 146
Pteronymia, 337
Pterophylla, 279
Pterophyllini, 278
Ptilodontidae, 110
Ptilogonatidae, 429
Ptychocheilus, 193, 207, 210
Purpuricenus dimidiatus, 312
Pycina, 347
Pycnopsyche, 239
Pycnoscelus, 294, 296
surinamensis , 294
Pyelorhamphus, 403
Pyrameis, 346, 351
Pyrotrichus, 311
Pyrrhogyra, 347, 351
Quercus, 67, 305, 306, 452
macrocarpa, 452
Radinotatum, 21 S
Rana, 452, 454
areolata, 455
aurora, 170, 171
Z^o^M, 170, 180
capito, 454
catesbeiana, 462
INDEX OF SCIENTIFIC NAMES
505
clamitans, 447, 462
grylio, 462
heckscheri, 459
muscosa, 170, 180
palustris, 462
pipiens, 462
sylvatica, 461
Rangifer, 124, 149, 384, 399
arcticus, 384
arcticus pearyi, 384
/nc)^^", 399, 441
Raphidia, 233
i?a^/w5, 125, 407, 409
rattus, 294
norvegicus, 294
Rehnia, 280
Rehnita, 272
Reithrodontomys, 124, 149
fulvescens, 445
humulis, 445, 454
montanus, 454
Reptilia, 475, 476
Rhahdoceratites, 291
Rhachocnemis, 284
Rhadinea flavilata, 453
laureata, 453
Rhadinoceraea, 243
Rhammatocerus, 21 A:
Rhaphidophorinae, 284
Rhinichthys, 204, 207, 214, 216
cataractae, 211, 212, 218
05CW/M5, 207, 210-213, 215, 216
Rhodocerinae, 330, 331, 333-334
Rhododendron, 304
Rhodoleptus, 313
Rhopalophora, 307
Rhopalopus, 309
i?;iM5, 305, 306
Rhyacophila, 237, 239, 241-243,
245
acropedes, 241
6t^/a, 243
Carolina, 242, 243
castanea, 243
glareosa, 242, 243
hyalinata, 243
invaria, 242, 243
pepingensis, 242, 243
philopotamoides , 243
profusa, 243
rayneri, 243
scissa, 243
sihirica gp. spp., 241
vagrita, 242
verrula, 242
Rhyacophilidae, 237
Richardsonius, 193, 212, 213
halteatiis, 205, 212
Ripaeglossa, 237, 250, 251
Robinia, 303, 305
Rodentia, 116-118, 126
Rodinia, 353
Romalea, 262
Romaleinae, 261-263
Romaleuni hispicorne, 316
Romerologus, 124
Ropalopus, 308
i?05a, 304
Rosalia, 309, 311
Rotatoria, 225, 228
Rutilus bicolor, 210
^a^aZ minor, 447, 452
Sabatoga, 342
Saiga, 401
^ai^, 335, 336
Salamandridae, 161
Salicaceae, 306
Salishella, 284
5a/ix, 304, 306, 308, 316
5aZwo, 208, 214
c/ary^t', 208, 210, 212, 216, 218
gairdneri, 210
Salmonidae, 187, 188, 193, 212
Salvelinus malma, 218
Sangamona, 399, 401, 408
Saperda, 302, 303, 308, 309
horni, 308
populnea, 306
Saphanini, 311
Sapindus, 305
Sarosesthes, 309
506
INDEX OF SCIENTIFIC NAMES
Sassafras, 305
Satyridae, 322, 324-326, 337-345,
352, 357-359, 364, 365
Satyrodes, 340, 343
Satyrus, 364
Scada, 336
Scalopodinae, 121
Scalopus, 125, 148
Scapanus, 108, 125, 139, 148
Scaphinus, 303, 308
Scaphiopus, 445, 454
hammondi, 89, 173
holbrooki, 445, 454
hurteri, 474
intermontanus, 173
Scarabaeidae, 316
Sceloporus, 377, 393, 452
graciosiis, 174-176
graciosus gracilis, 175
graciosus graciosus, 174, 175
graciosus vandenhurghianus ,
175
malachiticus, 393
undulatus, 377, 445
Schistocerca, 264-265
gregaria, 264
mexicana, 265
paranensis, 265
Schizax, 313
Scirtetica, 271
Sciuridae, 121, 122, 146, 150
Sciurus, 125, 146, 148
hudsonicus, 440
Scolitantides , 355, 356
Scudderia, 278
Semanotus, 302, 306
amethystinus, 312
ligneus sequoiae, 311
Semenoviola, 254
Sequoia, 304, 311
gigantea, 311
sempervirens, 311
Sermyle, 291
Serranidae, 199
Shotwellia, 271
Sidesone, 349
Signiodon, 124, 149
hispidus, 460
Sinarista, 337, 338
Siphateles, 207, 210, 213, 214. 216,
217
&ico/or, 210, 211, 216, 217
Siseme, 354
^wyfeo, 234, 235
Sistrurus catenatus, 454
miliarius, 454
ravus, 454
5?'/to canadensis, 431
corea, 431
kriiperi, 431
villa sa, 431
whiteheadi, 431
Smilax, 305
Smodicum, 307
Smyrna, 347
Snyderichthys copei, 212
Solenodon, 410
Sonronius, 244
Sorbus, 304
^orerc, 125, 137, 144, 148, 384
cinereus, 436, 438-440
cudahyensis, 438
lacustris, 438
pacificus, 137
tundrensis, 384
vagrans, 372
Soricidae, 121, 122, 145
5or/05a, 234, 235, 237
Spalacopsis, 307
Spaniacris, 272
Speotyto cunicularia, 445
Sphaenothecus, 313
Sphaeriidae, 227
Spharagemon, 271
Spilogale, 124, 145, 148
Spondylis, 303, 308, 309, 311
Spongovostox, 254
Stagmomantis , 292
calif ornica, 292
Carolina, 292
gracilipes, 292
limhata, 292
INDEX OF SCIENTIFIC NAMES
507
Staladitis, 354
Steiroxys, 282
Stenaspis, 313
Stenocoriis inquisitor, 306
Stenodontes , 307
Stenopelmatinae, 283-284
Stenopelmatus, 283
Stenosphenus, 302, 303, 313
Steremnia, 341, 343
Sternidocinus , 315
barbarus, 316
Steroma, 341
Stethophyma, 273
Sticthippus, 270
Stockoceros, 399, 401, 408
onusrosagris, 399
Storeria occipitomaculata, 453
Strangalia, 307, 309
Strigidae, 425
Strix, 425
varia, 453
Stygobromus, 225
Styracosceles, 284
Supella, 294
supellectilium, 294
Sylvilagus, 124, 139, 149
floridanus, 460
Symbos, 400, 436, 437, 440
Symmachia, 353
Symmetrodonta, 116, 117, 119
Synaphaeta, 311
Synaptomys, 124, 149
australis, 441, 444
borealis, 438
cooperi, 438
Syrbula, 274
Tachycines, 284
Tadarida, 125, 459
macrotis, 122
Taeniodonta, 116-118, 126
Taeyiiopoda , 262, 263
Talpidae, 121, 122, 143
Tamias, 124, 148
Tamiasciuriis, 124, 139, 148
Tanaocerinae, 260
Tajiaocerus, 260
Tangavius, 403
Tantilla coronata, 455
gracilis, 455
Tanupolama, 401, 408
Taphacris, 259
Tapirus, 396, 444, 464
Taranomis, 313
Tardigrada, 225, 228
Taricha, 161
Tatochila, 328, 330, 333, 358
Taxidea, 124, 139, 148
Taxodiaceae, 302, 312
Taxodium, 305
distichum, 447
Tayassu, 120, 124
angulatus, 122
Tayassuidae, 120-122, 147
Taygetis, 338, 339
Teicophryinae, 261
Teicophrys, 261
Teleoceras, 108
Temenis, 347
Tenebrionidae, 313
Teratornis, 403
Terias, 331
Terrapene Carolina, 454
ornata, 454
Testiido, 408, 409, 411
Tetraopes, 313
Tetraphlebia, 341, 343
Tetrigidae, 256-259
rc/n'x, 256-258
arenosa, 256
brunneri, 258
ornata, 256, 257
ornata hancocki, 257
ornata insolens, 257
ornata occidua, 257
ornata ornata, 257
sierrana, 256
subulata, 257
Tetr opium, 306
abietis, 312
Tetrops, 308
508
INDEX OF SCIENTIFIC NAMES
Tettigidea, 259
lateralis, 259
Tettigoniidae, 277-282
Tettigonioidea, 277-285
Thalarctos, 124
Tharops, 354
Thecla, 355, 356
Theclopsis, 355, 356
Theope, 355
Theorema, 355, 356
Thiemeia, 342
Thinobadistes, 442
r/«5&e, 354
Thoburnia, 202
TJiomomys, 124, 139, 149
Tkryptacodon aiistralis, 110
r;«/./a, 304, 435
Thylakion, 235
Thymallidae, 187, 188
Thymallus, 218
arcticus, 211
Thyridia, 336
TiUodontia, 116-118, 126
Timema, 290
Timemidae, 290-291
Ti metes, 347, 351
Tisiphone, 337, 338
Tithorea, 336
Tmetoglene, 353
Tomonotus, 271
Tonatia, 410
Toxotus, 306
Trachyrhachis , 272
Tragosoma depsarium, 306
Trepiduliis, lU
Triaenodes, 245-247
6am, 245-247
tor^a, 245-247
ssp., 246, 247
Tribolodon, 205
Trichonis, 355, 356
Trichophanes, 193, 198
Triconodonta, 116, 117, 119
Tridactylidae, 285-286
Tridactyliis, 286
Trigonidiinae, 288
Trigonidomimus , 288
Trimerotropis, 269, 270, 272
Trinectes, 214
Triodoclytus, 315
Troglochaetus, 225
Troglodytes troglodytes, 431
Tropidischia, 284
Tropidolophus, 271
nz/ga, 304, 435
Tubulidentata, 120
Tnbulodon, 120
Turbellaria, 225, 228
Turdidae, 422, 425
Tylonotus, 308
Tylosis, 313
Typocerus, 308
Tytthotyle, 262, 263
Udeopsylla, 284
Ulmns, 305
Ulochaetes, 311
f/wa, 92
Umbellularia, 305
Umbra, 196
krameri, 196
Umbridae, 188, 195, 219
Ungnadia, 305
Uraneis, 353
Urocyon, 124, 148
Ursidae, 121, 122, 145
t/m^5, 122, 137, 148
arctos, 137
Vaccininm, 305
Vandykea, 313, 315
tiiberculata, 311
Fawg55a, 346, 351
Varanidae, 162
Fa/g5, 293
Vatinae, 293
Velamysta, 337
Vespertilionidae, 121, 122
Victorina, 346, 351
FV/a, 347, 360
Vilernini, 263, 265
INDEX OF SCIENTIFIC NAxMES
509
Vostox, 254
Vulpes, 125, 137, 148
fidva, 441
Wormaldia, 233, 234, 236, 237
spp., 236
Xanthippus, 270
Xantusia vigilis, 1 74
Xenacodon multllalus, 110
Xenarlhra, 117
Xeracris, 272
Xylocrius, 311
Xylosteiis, 309, 311
Xylotrechus, 306
insignis, 316
Xyrauchen, 201
texanus, 202
Yersinia, 292
Yersiniops, 292
Zabirnia, 342
Zabuella, 354
Zacycloptera, 281, 282
Zammodes, 308
Zanthoxylum, 305
Zanycteris paleocena, 110
Zapata, 276
Zapodidae, 121, 122, 147
Zapodinae, 121
Za/>/^5, 125, 149
Zarf/e.v, 349, 351, 360
Zelkova, 67
Zelotaea, 353
Zerewe, 331, 333, 361
Zubovskya, 258, 266-267, 281, 290
297
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