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J. PIERPONT MORGAN PUBLICATION FUND
REPORTS OF THE
PRINCETON UNIVERSITY EXPEDITIONS
TO PATAGONIA, 1896-1899
Jobe At CrHER
IN CHARGE
EDITED BY
WHEETAM Bs SC Oma
BLAIR PROFESSOR OF GEOLOGY AND PALAZONTOLOGY, PRINCETON UNIVERSITY
VOLUME VII
PALAZKONTOLOGY IV
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PRINCETON, N. J.
THE UNIVERSITY
STUTTGART
SCHWEIZERBART’SCHE VERLAGSHANDLUNG (E. NAGELE)
1910-1932
* -3 2X
LANCASTER PRESS, INC.
LANCASTER, PA.
T
g.Cee -
J. PIERPONT MORGAN PUBLICATION FUND
REPORTS OF THE
PRINCETON UNIVERSITY EXPEDITIONS TO PATAGONIA
1896-1899
VOLUME VII
PALAAONTOLOGY IV
PART I LITOPTERNA OF THE SANTA CRUZ BEDS
By
WILLIAM B. SCOTT
PRINCETON UNIVERSITY
PNR JN ANAS Ole WUs, SAINI CUZ IIBIDIS
By
WILLIAM J. SINCLAIR AND MARCUS S. FARR
PRINCETON UNIVERSITY
PART III NATURE AND ORIGIN OF THE SANTA CRUZ FAUNA
WITH ADDITIONAL NOTES ON THE ENTELONYCHIA AND ASTRAPOTHERIA
By
WILLIAM B. SCOTT
PRINCETON UNIVERSITY
RPRINGERON] No Je
THE UNIVERSITY
SPW UT GAIR
SCHWEIZERBART’SCHE VERLAGSHANDLUNG (E. NAGELE)
1910-1932
ITTAUSIEJS, (Ole (COINTMEINITS, WOW, WIT,
PARTIE J IMaNS ILINCORIN SAIN Ole Wisls GAIN GRU Welds,
By W. B. SCOTT.
INTRODUCTION : ‘ : : ‘ é :
SYSTEMATIC POSITION OF THE LITOPTERNA .
PROTEROTHERIIDE . :
Diadiaphorus Amegh.
Licaphrium Amegh. .
Licaphrops Amegh.
Proterotherium Amegh.
Tetramerorhinus Amegh.
Tichodon Amegh.
Thoatherium Amegh. .
MACRAUCHENID
Theosodon Amegh.
Adianthus Amegh.
BIBLIOGRAPHY
PARI JL AWIES Ole Wiss SAINI CINUZ IssIDIS).
By W. J. SINCLAIR anp M. S. FARR.
HISTORICAL : : : 4 : : : :
THE SKELETON OF PELECYORNIS sy WILLIAM J. SINCLAIR .
SYSTEMATIC ZOOLOGY sy Witi1Am J. SINCLAIR
Phororhacos
Aves Incertz Sedis
BIBLIOGRAPHY : ‘ L ' A ;
ADDITIONAL LITERATURE NOT REFERRED TO IN THE TEXT
154
155
157
159
183
190
190
190
I9I
vi CONTENTS.
PART III. NATURE AND ORIGIN OF THE SANTA CRUZ
FAUNA WITH ADDITIONAL NOTES ON THE
ENTELONYCHIA AND ASTRAPOTHERIA.
By W. B. SCOTT.
GEOLOGY OF PATAGONIA
SANTA CRUZ VERTEBRATES $
THE ORIGIN OF THE SANTA CRUZ FAUNA 3
NOTE ON ADDITIONAL MATERIAL OF THE ENTELONYCHIA AND ASTRA-
POTHERIA .
Homalodontotherium Flower :
SYSTEMATIC POSITION OF THE ENTELONYCHIA
Astrapotherium Burmeister
TAXONOMIC POSITION OF THE ASTRAPOTHERIA
POSTSCRIPT
INDEX
ERRATA.
Page 53, line 15: Strike out Tichodon.
Page 60, line 25: For (Pls. XI, fig. 4, etc.) read (Pls. XI, fig. 8, etc.).
Page 203, line 20: For (Plate G) read (Plate J).
Page 212, line 12: For (Pl. G) read (Pl. J).
line 20: For Plate H, read Plate G.
Page 213, line 9: For (Plate J) read (Plate H). ‘
Page 217: after line 9: Insert TOXODONTID& (10).
DATES OF PUBLICATION OF THE PARTS OF VOLUME VII.
Pp. 1-156, Pll. I-XX, published October 12, 1910.
Pp. 157-191, Pll. XXI-XXXV, published January 8, 1932.
Pp. 193-238, Pll. A-K, published April 20, 1932.
193
201
218
222
223
232
234
238
238
239
J. PIERPONT MORGAN PUBLICATION FUN
Reports of
The Princeton University Expeditions
J. B. HATCHER, tn Cuarce
EDITED BY
WILLIAM B. SCOTT
BLAIR PROFESSOR OF GEOLOGY AND PALA ONTOLOGY, PRINCETON UNIVERSITY :
VOLUME VII—PALHONTOLOGY
Parr I, LiroprerNa oF THE Sana Cruz Baps ; A
af Ramage
BY
PRINCETON UNIVERSITY
(Pp. 1-156. Pls. I-XX)
BRUNCH TON, Nojo 5
THe UNIVERSITY _
STUTTGART
E. ScHWEIZERBART’SCHE VERLAGSHANDLUNG (NAGELE & Dr. SPROESSER) — | a
1910 A
Realy Ne
Page 53, line 15: Strike out Z7zchodon from the list of synonyms of Pro-
terotheriume.
EAgeOOmlne 254707) (PIs lig. 4, ete:)\\ vead (Pls. XI, figs 8} ete:).
wits 3 an ; : : i
“A : ¥ oe ; i Piet
t a é seat fy Sat sah. une i Mees
ae oh ae ie Case: sot ees ¥ re 4% ean
He a ix F
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Divas Ratan icles = ge Sy es
ae S it 5 age
SeacF ae Saha cae * -
MAMMALIA OF THE SANTA CRUZ BEDS.
PART I. LITOPTERNA.
BY
VV IIL IE eI 18. SC ©) IT,
PRINCETON UNIVERSITY.
HE memoir on the Litopterna was originally to have been written
by the late Mr. Hatcher, but through his lamented death, the work
has devolved upon myself. Unfortunately, during my visit
to La Plata, my limited time was so fully taken up with other groups of
Santa Cruz fossils, that it was impossible for me to make any satisfactory
studies of the Litopterna in the collections of Dr. Ameghino and the La
Plata Museum. This lack has, to some extent been repaired by the kind-
ness of Dr. Ameghino, who has with his usual courtesy sent me excel-
lent photographs and plaster-casts of nearly all of his types of the Santa
Cruz Proterotheriide and these have proved very helpful in the deter-
mination of the genera and species.
The materials for the study of this group in the collections of Princeton
University and the American Museum of Natural History are abundant
and admirably preserved, and a very full account of the dental and skeletal
structure may be given. On the other hand, the determination of species,
more particularly of the genus Proferotherium, is exceeding difficult. To
solve the problem of species in a satisfactory and convincing manner, it
would first be necessary to have a detailed stratigraphical knowledge of
the Santa Cruz formation and, further, to ascertain the exact position in
the beds of every specimen collected. In the absence of such knowledge,
it is not yet practicable to distinguish contemporary and fluctuating varia-
tions from successive and relatively fixed mutations, and where a genus was
in a state of vigorous development, the number of species which should
be assigned to it becomes largely a matter of conjecture. For the most
part, the genera of the Santa Cruz Litopterna are well-defined and easily
distinguishable, save such as are still very incompletely known, and the
families are even better and more clearly distinguished.
I
2 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
It is still a matter of some uncertainty as to the number of families rep-
resented among the Santa Cruz Litopterna. At one time or another,
_Ameghino has referred to this order four families, the Notohippidz, Pro-
terotheriide, Macrauchenidz (including the Mesorhinidze) and the Adian-
thidz. Of these, the Notohippidz, which Ameghino has latterly referred
to the horses, his order ‘‘ Hippoidea” (04, 33), I agree with Roth (03,
33) in regarding as nearly allied, if not actually referable, to the Toxo-
dontia. As to the Proterotheriida and Macrauchenidz there is no dif-
ference of opinion, they are clearly defined and unmistakable family
groups. The Adianthidz are so very imperfectly known, that their status
is still quite uncertain; they are here merged with the Macrauchenide,
from which a separation of them is, at present, at least premature.
The Litopterna are an unusually interesting group of mammals, because
of the fundamental problems of descent which they raise, and a definite
determination of their systematic position and relationships will illuminate
many obscure questions of evolutionary philosophy. Especially is this
true as regards the great problem of parallel and convergent development,
the independent acquisition of similar structures in unrelated or remotely
related groups.
The dentition, whichis always brachyodont inall of the known members
of the order, differs considerably in the two Santa Cruz families, more par-
ticularly in the anterior region. In the Proterotheriidz the constant dental
formula is Iz, Ci, Pz, M3, and the single upper incisor and external lower
incisor (i? and is) are enlarged, growing from persistent pulps, to four
small, sharp-pointed tusks; the upper canine is lost and the lower is so
small as to be nearly or quite functionless. In the Macrauchenidz the
number of teeth is unreduced from that typical of nearly all groups of early
placental mammals, giving the formula Ig, Cr, Pz, Ms. The incisors,
canines and foremost premolars are of subequal size and simple, com-
pressed conical form.
In all of the Litopterna, even those of the Pleistocence, the premolars
are nearly all simpler in pattern than the molars. In the Santa Cruz
genera the fourth (and sometimes the third) lower premolaris quite molari-
form, and the fourth upper approximately so. The molars havea pattern
which has often been compared to that of Paleotherium, but, so far as the
upper teeth are concerned, the resemblance is not at all close and, indeed,
the plan is quite different from that of any of the lophodont Perissodac-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 3
tyla. The upper molars have two equal, concave and somewhat crescentic,
external lobes, which unite ina mesostyle, and two principal internal, more
or less conical cusps (the proto- and hypocone). Anterior and posterior
conules are prominently developed, but do not fuse into well-defined trans-
verse crests, the posterior crest being especially incomplete. The internal
cingulum is so elevated as to enclose deep fossettes, the number and position
of which differ in the various genera. The internal cusps are always close
together and often connate, or connected by aridge. The lower molars
are composed of two crescents, one behind the other, a pattern which is
common in early members of both Artiodactyla and Perissodactyla, such
as the Anoplotheres, Palzeotheres, Titanotheres, etc. A very character-
istic feature is the pillar or spur in the inner concavity of the posterior
crescent, which, there is reason to believe, was originally common to all
of the Litopterna, but in the Santa Cruz several genera have it in very
reduced form and others have lost it altogether. It is more reduced in
the Proterotheriidz and in Adzanthus, more developed in the other Mac-
rauchenide. The Pampean genus Wacrauchenza has no trace of it in the
true molars, but retains it in the milk-premolars. The third lower molar
may have a small talon, but more commonly there is none.
All of the antemolars have predecessors in the milk-series, the teeth
of which in general resemble their permanent successors. The deciduous
grinding teeth, except dp 4, unlike those of the perissodactyls, are simpler
than the permanent molars.
The sku@ differs much in the two families, being of more normal ap-
pearance in the Proterotheriidz than in the Macrauchenidz, in which the
nasal bones are greatly shortened and the anterior nares correspondingly
enlarged, showing that a proboscis was at least in an incipient stage of
development. No alisphenoid canal is present in any known member of
the group and the foramina rotundum and ovale are confluent. The
tympanic is very loosely attached to the skull and imperfectly ossified
not forming a bulla, but merely a small plate, with large, irregular meatus
externus, which is not at all tubular. A high sagittal crest is present in all
of the genera of both families.
One of the most noteworthy differences between the two families is in
the length of the neck; in the Proterotheriidze the neck is very short and
the canal for the vertebral artery occupies the normal position, perforating
the transverse processes of the cervical vertebree. In the Macrauchenide,
4 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
on the other hand, the neck is greatly elongated and, in most of the
cervicals, the vertebrarterial canal passes through the neural arch, very
much as in the Tylopoda, to which Macrauchenia was originally referred.
In both groups, the odontoid process of the axis retains its primitive
cylindrical form. The number of trunk-vertebrz is not positively known
for any genus of either family, but it is very probable that this number is
19 in the Macrauchenidz and 21-22 in the Proterotheriidz. The lumbar
and posterior thoracic vertebree have zygapophyses of the semicylindrical,
interlocking type, which is especially characteristic of the Artiodactyla,
but is found also in the horses. The last two lumbars and the first sacral
have additional articulations by means of large facets on the transverse
processes. The sacrum is long, tapering much posteriorly, which indi-
cates that the tail was short, though no caudal vertebrze have yet been
found.
The “mds are long and slender, but the feet are only moderately
elongate, except in one monodactyl genus (7hoatherium) of the Protero-
theriide. The scapula has both acromion and metacromion, which are
most prominently developed in the Macrauchenidz. No clavicle is known.
The humerus is short and has a very simple, pulley-like trochlea. The
fore-arm bones are separate in all of the Santa Cruz Litopterna and the
ulna is remarkably large, while the radius is relatively slender. The
femur has a prominent third trochanter and a large pit for the plantaris
muscle. The leg-bones are not ankylosed in any of the Santa Cruz
genera, but the fibula, though complete, is much more reduced than the
ulna and always retains an articulation with the calcaneum.
The feet are quite different in the two families, though both are char-
acterized by mesaxonic, or perissodactyl symmetry. In the Protero-
theriidee they have a very horse-like appearance, the median digit being
much enlarged and supporting the whole weight, while the lateral digits
are reduced to mere dew-claws. In one genus of this family, 7Zoatherium,
complete monadactylism is attained and only minute vestiges of the lateral
metapodials remain. The ungual phalanges have a decidedly equine
character. On the other hand, in the Macrauchenidz, the feet are func-
tionally tridactyl and almost isodactyl, the three digits being of approxi-
mately equal length and thickness, though the median, or third, is slightly
the longest. The ungual phalanges are short and heavy, almost nodular,
and have a rhinocerotic rather than an equine appearance. In both families,
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 5
the arrangement of the bones in the carpus and tarsus is much more
primitive than in even the most ancient and primitive known perisso-
dactyls. In the carpus the arrangement is almost serial, except that the
scaphoid extends over upon the magnum, though the lunar is widely
separated from the unciform. The calcaneum bears a large facet for the
fibula and the astragalus has a depressed-convex head, which rests only
upon the navicular and has no contact with the cuboid. The tarsus is
thus not at all perissodactyl in character, but is more like that of the
Toxodonta, Typotheria and other South American ungulate groups.
The mode of digital reduction is that which Kowalevsky has called ‘“in-
adaptive,’ and even in the monodactyl 7hoatherium, the articulations of
the carpals and tarsals with the metapodials show but little modification
of the plan characteristic of a pentadactyl foot.
SVSTEMUNING IPOSIIMON, Ole Walls, ILO IMR IN VAY
That the Litopterna have a strong resemblance to the Perissodactyla, it
needs no argument to prove, but is obvious at the first glance. The inter-
pretation of this resemblance in terms of genetic relationship is a very
different and by no means easy problem. It is not surprising that students
of the Litopterna should have reached opposite conclusions regarding the
systematic position of the group, for this is merely another case of the oft
recurring problem, as to how far certain resemblances are offset by differ-
ences of structure. The answer to this question is largely conditioned by
the opinion which is held concerning the mode in which the evolutionary
process acts, and how generally similar structures are acquired in unrelated,
or distantly related groups. Even though such parallelism of development
be admitted to the fullest extent, great difficulties arise in the application
of the principle to concrete cases and in distinguishing between those
resemblances which are the evidences of genetic relationship and those which
have been independently acquired. No better illustration of this general
problem could be desired than that afforded by the Litopterna.
It would seem that the general opinion is that the Litopterna are nearly
related to the Perissodactyla. Ameghino, who first distinguished and named
the group, has all along maintained its perissodactyl relationship, and, in
his later publications, has not employed the term Litopterna, but has simply
referred the families to the Perissodactyla (’04, 52). This is the more
remarkable, since he now separates the horses from the Perissodactyla as
6 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
a distinct order, the Hippoidea (0. cz#.). Zittel also does not recognize the
group as of even Subordinal rank, but includes the families among the peris-
sodactyls (’91, 263, 267), an example which is followed by Gaudry and appar-
ently alsoby Roth (’03). Lydekker, on the other hand, holds avery different
view and believes that the Litopterna, the Toxodontiaand the Astrapotheria
‘have originated from a common ancestral stock, though apparently before
the perissodactyles were differentiated from an earlier group known as the
Condylarthra” (’96, 77). This represents very nearly the conclusion
which I have reached, that the Litopterna ave more nearly related to the
Toxodontia than to the Perissodactyla, and that the striking resemblances
to the latter are largely due to parallelism of development, but in part
also to the retention of certain primitive characters once common to all
ungulates, or even to all mammals.
The significant likenesses between the Litopterna and the Perissodactyla
are, toa very great extent, conditioned by the fact that in both groups the
feet are constructed upon a plan of meSaxonic symmetry, while such
structures as are unaffected by this symmetry are, for the most part, funda-
mentally different in the two orders, and are much more primitive in all
of the Litopterna than in the most ancient known perissodactyls. Indeed,
one highly significant result of a comparison of the two groups is that
their earlier representatives are no more alike than their later members.
In other words, so far as their history can be traced back, the two orders
show no signs of converging to a common ancestry.
The resemblances between the Litopterna and the Perissodactyla are
not so much between the two groups, as wholes, as between the horses
and the Proterotheriidz, which are certainly very remarkable, and yet
even here, the fundamental dissimilarity of plan is none the less obvious,
as revealed in all parts of the skeleton, but especially in the carpus and
tarsus. In addition to the mesaxonicsymmetry of the feet and the lophodont
molar plan, the only other point of special resemblance to the perisso-
dactyls is the third trochanter of the femur. This, however, is a feature
common to nearly, if not quite, all early mammalian groups, and there-
fore is of no great weight in deciding questions of relationship.
The more significant differences between the Litopterna and the Perisso-
dactyla are expressed in the following table.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 7
PERISSODACTYLA.
Upper molars with conules early
fusing into two transverse crests.
Lower molars without pillar in pos-
terior crescent.
Alisphenoid canal present.
Tympanic usually forming a bulla.
Odontoid process of axis spout-
shaped in long-necked genera.
Zygapophyses of posterior thoracic
and lumbar vertebrz with plane
faces (except in horses).
Mesosternal segments broad and
depressed.
Scapula without acromion (except
in early horses) or metacromion.
Ulna greatly reduced in genera with
enlarged digit III.
Carpus strongly interlocking, with
scaphoid resting on magnum and
lunar on unciform.
Fibula not articulating with cal-
caneum.
Distal end of astragalus flat, articu-
lating with navicular and cuboid.
Digital reduction adaptive.
LITOPTERNA.
Upper molars imperfectly lopho-
dont, posterior crest not formed.
Lower molars with pillar in pos-
terior crescent (sometimes re-
duced).
No alisphenoid canal.
Tympanic scale-like.
Odontoid process always peg-like.
Zygapophyses of posterior thoracic
and lumbar vertebrze semicylin-
drical.
Mesosternal segments mostly nar-
row and compressed.
Scapula with acromion and meta-
cromion largely developed.
Ulna little reduced and proximally
larger than radius.
Carpus semi-taxeopod, with sca-
phoid resting on magnum, but
lunar not touching unciform.
Fibula articulating with calcaneum.
Distal end of astragalus depressed-
convex, articulating with navicu-
lar only.
Digital reduction inadaptive.
To my mind, the preponderance of evidence is thus decidedly in favor
of the view that the Perissodactyla and Litopterna are no more closely
related than two ungulate orders must necessarily be (if the monophyletic
origin of the hoofed animals be a fact) and that resemblances between
them are due to parallelism and not to genetic affinity. The primitive
features of the Litopterna, such as the semi-taxeopod carpus and tarsus,
extensive articulation between the fibula and calcaneum, and the inadap-
tive method of digital reduction, are all as distinctly marked in the highly
8 PATAGONIAN EXPEDITIONS: PALAZSONTOLOGY.
specialized and monodactyl 7oathertum as in the tridactyl and isodactyl
genera. When it is remembered that 7/oathertum greatly surpasses the
horses in completeness of digital reduction, the retention of so many
primitive characters becomes all the more remarkable and significant.
The most important characteristics in which the Litopterna differ from the
Perissodactyla are points of agreement between the former and the Toxo-
dontia, most of which have tridactyl feet with mesaxonic symmetry. The
principal difference between the Toxodontia and the Litopterna is in the
structures of the auditory region, which, as Roth (’03) has pointed out, is
very remarkably specialized in the former, but normal in the latter. To
this question it will be necessary to return in the chapter dealing with the
Santa Cruz fauna as a whole, but I may so far anticipate that chapter as
to say that, in my judgment, despite this very striking and important dif-
ference, the Litopterna and Toxodontia “originated from a common an-
cestral stock,’ as Lydekker has expressed it.
IIR) IABISAO) MeO zee.
The two families into which the Santa Cruz Litopterna are divided are
sharply marked off from each other and represent two strongly divergent
lines of development. The Proterotheriidz are remarkable for the strik-
ing way in which they parallel and imitate the horses, especially in foot-
structure, and they even surpass that perissodactyl family in the complete-
ness with which the monodactyl foot is attained.
The Santa Cruz representatives of the present family are all of small
or moderate size and most of them are slenderly built; none are massive
or of great stature.
All of the Santa Cruz genera have the same dental formula: Ik, Cy, Pi,
M3. The single upper incisor is enlarged into a small, more or less tri-
hedral and sharp-pointed tusk, growing from a persistent pulp; the outer
lower incisor in all of the genera, except 7/oatherium, is correspondingly
enlarged. The lower tusk bites behind the upper, which is therefore
worn on the posterior face. The median lower incisor is usually very
small and of little or no functional importance, having no upper tooth
opposed to it. The homologies of these incisors are not quite certain,
but there is much reason to believe that, as in the toxodonts, they are the
second upper and third lower of the original three (17 and is). The wide
separation between the two upper tusks makes it almost certain that at least
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 9
one incisor has been lost from each premaxilla, and that the tusk is not i*
is shown by two considerations: (1) In some individuals of 7/oatherium
a very small deciduous incisor is inserted in the premaxilla behind the tem-
porary tusk; (2) the fact that the lower tusk bites de/zud the upper is evi-
dence that the former is one degree farther back and therefore represents ts.
The upper canine is always absent and the lower, though present in all
cases, is much reduced in size and can have had no functional significance.
The premolars are never altogether molariform, though p* approximates
the molar pattern, and pzand rarely ps have that pattern quite completely.
Though characteristically differing in the various genera, the upper molars
are much alike throughout the family and have two well-defined, external,
concave cusps, with two conical internal cusps and anterior and posterior
conules. The transverse crests, especially the posterior one, are incom-
pletely formed by the fusion of the internal cusps and the conules, and there
is a tendency for all of these internal elements to become confluent and
form an antero-posterior ridge. The varying extent to which this con-
fluence is carried, forms one of the diagnostic features of the different
genera. Where the tendency is least pronounced, as in Diadiaphorus,
there is a certain resemblance to the molar-pattern of the Palzeotheriidz,
though differing in the absence of the posterior transverse crest, or
metaloph.
The lower molars have the bicrescentic pattern so common in early and
primitive families of both Artiodactyla and Perissodactyla, such as the
Anoplotheriidz, Palzeotheriide, Titanotheriidz, etc., but often with the
addition of the characteristic pillar in the concavity of the posterior crescent.
This element, so general among the South American ungulates, is found
in the Santa Cruz Proterotheriidz in varying stages of reduction; it may
be quite conspicuous (Lecaphrium), very minute and observable only in
perfectly unworn teeth (Proterotherium), or entirely wanting (Dzadzaphorus,
Thoathertum). \Nhen present, this element is an isolated conical pillar, not
connected with the outer wall by a transverse spur or ridge, as it typically
is in the Macrauchenide. The last lower molar may either be without
any talon (7hoatherium, Diadiaphorus) or may have a very small one
(Proterotherium), or a larger one (Licaphrium).
The skull has a moderately capacious and well rounded brain-case, with
high and thin sagittal crest and orbits completely encircled with bone. The
tympanic was so loosely attached that it has been lost from all the avail-
10) PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
able skulls and probably, as in the Macrauchenidz, was very small and
did not form a bulla. The nasals are usually of normal length, articulat-
ing with the premaxillz, but may be somewhat shortened, as in 7oathe-
vium, or considerably so, as in Diadtaphorus. However, this reduction is
never comparable to that in the Macrauchenidz.
The neck is always remarkably short in comparison with the length of
the limbs, and the cervical vertebrz have the vertebrarterial canal in the
normal position, perforating the transverse processes. The odontoid pro-
cess of the axis is always peg-like. The number of trunk-vertebrze is not
definitely known, for no complete back-bone has yet been found, but a
careful study of the available material renders it probable, that this number
did not exceed 21-22, 14-15 thoracics and 7-8 lumbars. The posterior
thoracic and lumbar vertebrz have semicylindrical, interlocking zygapophy-
ses. The sacrum is long and tapers so much posteriorly, that the shortness
of the tail is made quite certain, even in the absence of any known caudal
vertebra. The ribs are of the ordinary ungulate type, and the sternum
has not yet been recovered.
The limbs are long and slender, but the feet, except in 7hoatherium,
are of only moderate elongation and the metapodials are usually short.
The scapula is large and has a prominent metacromion and a small acro-
mion, the two processes being quite near together, much nearer than in the
Macrauchenidz. The humerus is short and the fore-arm bones are always
separate ; the ulna is surprisingly little reduced, in view of the great degree
of digital reduction attained in the family. The elongation of the fore-
arm is not so great and that of the manus greater than in the Macrau-
chenidz.
The pelvis has a decidedly equine appearance, though the division
of the iliac plate into dorsal and ventral processes is less marked, and the
tuberosity of the ischium is small in all of the genera in which the pelvis
is known. The limb-segments have somewhat different proportions from
those of the Macrauchenidz, the femur being relatively less, and the tibia
and pes more elongate. The femur has a strikingly equine character,
which is due to the proportions of the head and shaft, the high, bluntly
pointed great trochanter and the prominent third trochanter, which is larger
than in the Macrauchenide. The tibia and fibula are always separate,
though the latter is slender and much more reduced than the ulna, and the
articulation with the calcaneum is retained in all the genera.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. II
A highly characteristic feature of the Proterotheriidz, which strongly
distinguishes them from the Macrauchenidz, is the structure of the feet.
These are moderately elongate, except in 7hoatherium, which has very
long feet, and the elongation is largely due to the length of the phalanges,
the metapodials being quite short. In both manus and pes the third
digit is greatly enlarged and carries the whole weight of the body, while
the second and fourth are very much reduced and either form dew-claws,
or, in the case of the monodactyl 7hoatherium, nothing remains of the
lateral digits except vestiges of the proximal ends of the metapodials.
This isa more complete degree of monodactylism than in any other known
mammal. Thus, in all of the Santa Cruz genera of the family, the aspect
of the feet is strikingly and surprisingly horse-like, a resemblance which is
borne out by the very equine character of the ungual phalanges.
Despite this high degree of specialization, carpus and tarsus retain a
very primitive structure, which is not only not in the least equine, but is
not even perissodactyl. The carpus is almost taxeopod, except that the
scaphoid has extended over upon the magnum, the lunar having no
contact with the unciform, from which it is excluded by the articulation,
entirely lateral, between the magnum and pyramidal. The tarsus is
equally primitive; the calcaneum has a large facet for the fibula and the
astragalus is widely separated from the cuboid, articulating with the navic-
ular by means of a convex head, which is less flattened than in the Macrau-
chenidz. The method of digital reduction, which in all known perisso-
dactyls, both fossil and recent, is according to the mode which Kowalevsky
called ‘‘adaptive,” is in the Proterotheriidz “‘inadaptive.”’ That is to say,
the vestigial digits retain the carpal and tarsal connections which they
originally had. A slight degree of adaptive modification may be observed
in the tarsus of 7/oatherium, but as compared with the pes of the less
perfectly monodactyl horse, it is surprisingly incomplete.
Aside from certain imperfectly known and doubtful forms, the Santa
Cruz Proterotheriidz are divisible into four well-marked genera, dis-
tinguished by the following characteristics.
A. Feet tridactyl ; internal cusps of upper molars distinct ; lateral lower incisor (iz) much larger
than median (i;), which is very small.
I. Nasals much shortened ; lower molars without pillar in posterior crescent ; last molar without
talon. Diadiaphorus.
II. Nasals of normal length; lower molars with pillar in posterior crescent ; last molar with
talon.
12 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
1. Teeth more massive ; upper premolars less differentiated ; upper molars with inner cusps
partly connate; pillar in posterior crescent of lower molars large; animal stouter.
Licaphrium.
2. Teeth with thinner cusps; upper premolars more complex; upper molars with inner
cusps separate ; pillar of lower molars very minute and vestigial ; animal more slender.
Proterotherimm.
B. Feet monodactyl ; internal cusps of upper molars confluent ; lower lateral incisor (iz) but little
larger than median (i). Thoatherium.
The mutual relationships of these four genera are reasonably clear.
Thoathertum is in almost all respects much the most advanced and spe-
cialized and must have diverged from the others early in the history of the
family. One primitive feature, the subequal size of the lower incisors,
Thoatherium retains, and that this feature is really a primitive one, is
rendered very probable by the fact that in the other genera the milk-incisors
are of this type. voterotherium and Licaphrium are very closely related
and may be taken as the central line of the family; the former is somewhat
more advanced, as is shown in the more complex premolars and in the
reduction of the pillar to vestigial proportions. In dentition, Lzcaphrium
more nearly represents the primitive condition of the family than any of
the other genera. Dzadtaphorus is another divergent line, characterized
by the complete loss of the pillar from the lower molars, and the notable
shortening of the nasal bones, for most of the species also by a greater
bodily stature.
DIADIAPHORUS Ameghino.
(Plates I-V; XIII, Fig. 9.)
Diadiaphorus Amegh.; Enum. Sistematica, etc., 1887, p. 20.
Bunodontherium Mercerat; Revista del Museo de La Plata, T. I, 1891,
P- 450.
Oreomeryx Mercerat, in part; Ibid., p. 465 (jde Ameghino).
This genus includes the largest representatives of the family which are
found in the Santa Cruz beds, and is characterized (1) by the very com-
plete separation of the internal cusps of the upper molars, which have
nearly square crowns; (2) by lower molars without talon, or postero-
internal pillar; (3) by the much shortened nasal bones.
Dentition (Pls. Il, figs. 2-4 ; III, figs. 1-5, 8).
A. Upper Jaw. Thesingle upper incisor is large and caniniform, some-
what recurved and acutely pointed ; it is of triangular cross-section, with
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 13
apex directed forward, and the posterior face is abraded by the lower
lateral incisor.
A considerable diastema separates the incisor from the next succeeding
tooth, p>. The premolars increase in size posteriorly, an increase which
issudden between p* and p*, and gradual behind that. The first pre-
molar is quite small and implanted by two roots; the crown consists of a
single external lobe, which has a cordate and slightly convex outer face,
and a very low internal enamel ridge, or cingulum, which is divided by a
median sulcus intoanterior and posterior portions. The second premolar
is very much larger and is inserted by three roots; the crown is formed
essentially as in p+, but the external face has two convexities separated by
a shallow median depression; the internal ridge is better developed and,
in addition, there is an internal cingulum. The third premolar is still
larger and almost molariform, but has only three roots, of which the internal
one is very large; the external wall consists of two equal, concave cusps,
which unite to form a median ridge, but has no distinct anterior or pos-
terior style; the internal ridge is distinctly, but incompletely divided into
three cusps, the deutero- and tetartocones and the anterior conule, the
posterior conule being a minute pillar attached to the inner side of the
postero-external cusp (tritocone) ; the cingulum varies in prominence and
completeness. The fourth premolar is like p*, but larger, and the posterior
conule is much better developed and the extremely large internal root
shows signs of an incipient division into two.
The molar series is shorter than the premolar. The first and second
molars have a similar pattern and differ only in size, m® being the largest
of the series. The crown consists of two equal external lobes, the para-
and metacones, with concave outer faces, which meet in a prominent meso-
style, but, though the anterior and posterior borders are raised, there is no
distinct para- or metastyle. The two internal cusps, proto- and hypo-
cones, of which the former is somewhat the larger, are more or less con-
ical, or pyramidal in shape: the anterior conule is connected with the
antero-internal cusp (protocone), forming with it a very oblique transverse
crest, but is demarcated from the antero-external cusp (paracone) by a
deep, narrow, vertical cleft, while the posterior conule is a slender, iso-
lated pillar, connected at the base with the postero-external cusp (meta-
cone). From the postero-internal cusp (hypocone) runs a narrow promi-
nent ridge, perhaps an elevated cingulum, to the hinder edge of the
14 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
metacone, enclosing a deep fossa with the posterior conule. The cingu-
lum varies somewhat in development, but is always quite prominent on
the antero-internal and inner sides, enclosing shallow fossz before and
behind the protocone, and ending upon the hypocone.
When in an advanced state of wear, the molar-pattern has quite a dif-
ferent appearance ; an anterior, oblique, transverse crest, or protoloph, is
formed by the protocone and anterior conule, which become connate with
the paracone, and the posterior conule is confluent with the metacone,
from which it forms a projection. Thus there is produced a certain simi-
larity to the molar-pattern of Paleotherium, to which attention has often
been called, but the absence of the posterior crest (metaloph) and the
consequent irregular, S-shape of the valley are significant differences.
The third molar is the smallest of the series and is made asymmetrical
by the reduction of the posterior half of the crown; the metacone is con-
siderably smaller than the paracone and the hypocone is extremely small.
All of the grinding teeth are closely appressed, so that the postero-external
angle of each tooth actually notches the tooth behind it.
B. Lower Jaw. The median incisor (iz) is a very small, simple and
subconical tooth, which, to all appearance, can have been of little or no
functional importance, for even in very old animals it shows hardly any
sign of wear. The lateral incisor (is) is tusk-like, somewhat thinner and
more compresscd than the upper tusk, behind which it bites. The canine
is very small and simple.
The first lower premolar (pz) is much the smallest of the series and is
inserted by asingle root; the crown is simple and of elongate, compressed-
conical shape, with cingulum well defined on the inner, but not on the
outer side. The second premolar is of similar shape, but is very much
larger and is carried upon two roots; the cingulum is prominent both in-
ternally and externally and on the inner side are two low ridges, enclosing
Shallow fossze, of which the posterior is much the larger and deeper. The
third and fourth premolars are molariform, but ps has a minute pillar on
the inner side of the front end of the anterior crescent, and pz has a similar
pillar on the hinder end of the posterior crescent.
The lower molars are much like those of Auoplotherium, Paleotherium
and Zitanothertum and are composed of two crescents, without accessory
cusps or styles, but with prominent cingulum; mz has no talon or unpaired
lobe. In entirely unworn teeth, minute vestiges of the postero-internal
pillar may sometimes be observed in mg and sz.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 15
Milk Dentition.—The only example of the milk dentition which I have seen
in this genus is a young skull without mandible or premaxillary region; all
the milk-premolars are in place, as is also m+, while m* is visible in the jaw,
but had not yet come intouse. The temporary premolars closely resemble
their successors both in size and in pattern, but in all of them the two in-
ternal cusps are more distinctly separated, and dp* and +, at least, are
implanted by four roots, the internal pair of which differ from those of the
true molars in being of more nearly equal size, though the posterior root
is slightly larger than the anterior.
The Sku/7/ (Pls. II, figs. 1, 1a; IV, fig. 1) bears considerable resemblance
to that of the North American Oligocene genus, MJerycotdodon (Oreodon),
though this resemblance is entirely superficial. The upper contour of the
skull is a nearly straight line from the occipital crest to the tips of the
nasals; the cranium is long, with moderately full brain-case, which, however,
narrows much anteriorly; the face is short and the whole skull is deep
dorso-ventrally in proportion to its length. The orbits, which are closed,
are large and have a somewhat oblique position, so as to present slightly
forward, as well as laterally. The sagittal crest is very prominent, especially
posteriorly, where the roof of the brain-case slopes downward.
Asa whole, the occiput is high and narrow; on the ventral half, above
the foramen magnum, is a broad median convexity, with a shallow lateral
fossa over each condyle; the dorsal half, which is extremely narrow, is ~
concave. The occipital crest is very prominent in the dorsal region, dying
away ventrally upon the paroccipital processes. ‘These processes are long,
very broad and laterally compressed, almost plate-like, tapering distally
to a blunt point. The basioccipital is long and stout, with low and thin
ventral keel; it is broadest about the middle of its course, narrowing
slightly toward eachend. The condyles, which are formed entirely by the
exoccipitals, are rather small, but project prominently backward, and the
foramen magnum is relatively small. The exoccipitals are wide and low,
meeting in the median line; on each is a low, blunt process, the two
separated by a deep median notch. The supraoccipital, which forms
somewhat more than the dorsal moiety of the occiput, is high and narrow.
The periotic is exposed as a narrow strip in the deep, narrow cleft
between the exoccipital and the squamosal; it does not form a mastoid
process. The tympanic was not ankylosed with the periotic and was but
loosely attached to the skull. I have seen no example of this bone, which
is missing from all the skulls at my disposal.
16 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
The parietals are relatively long, extending forward to the postorbital
constriction, where, on the dorsal side, they diverge to receive the pos-
terior ends of the frontals. As already mentioned, the parietals support
throughout their length a thin sagittal crest, which is low anteriorly and
rises gradually behind, where it becomes very high. In this posterior
region the parietals are pierced by several conspicuous vascular foramina.
The squamosal extends well upward upon the side of the cranium, greatly
narrowing the parietal in this region, but is widely separated from the
frontal. The glenoid cavity is quite equine in character and may be
described in the words which Flower (’85, 187) has applied to that of the
horse; it is ‘‘greatly extended transversely, concave from side to side,
convex from before backward in front and hollow behind.” The only
difference is that the anterior convexity is less prominent in the Santa
Cruz genus. The postglenoid process is long, thick and spike-shaped,
rhinocerotic rather than equine in character, but relatively shorter and
more massive than in existing rhinoceroses. The posttympanic process,
which is small, but well defined, is applied closely to the periotic and
widely separated from the postglenoid. The zygomatic process is rather
short, arching out boldly from the cranium; it is laterally compressed and
thin, but quite broad dorso-ventrally, this breadth diminishing anteriorly
as that of the jugal increases. The latter is elongate, extending posteriorly
to the glenoid cavity and anteriorly to the lachrymal; the free portion is,
like the zygomatic process, laterally compressed, but the suborbital por-
tion is considerably thickened. The postorbital process is broad and
prominent, but not very long; it unites suturally with the much longer
process of the frontal. The lachrymal is large and considerably expanded
upon the face, forming part of the inferior and almost all of the anterior
wall of the orbit, and even some of the dorsal margin; it articulates with
the jugal, maxillary and frontal, but is widely removed from the nasal ;
the foramen is quite large and entirely external in position, and the spine
is a low tubercle.
The frontals are very large and form a broad, lozenge-shaped and nearly
plane forehead; they are widest over the orbits, narrowing gradually to
the sutures with the maxillaries and nasals, which form a nearly straight,
transverse, though somewhat irregular line. The frontals expand very
abruptly in front of the postorbital constriction and the temporal ridges,
which diverge from the sagittal crest, take an almost transverse course ;
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 17
from the hinder margin of each a low tubercle, or spine, projects into the
temporal fossa. The postorbital process, which is long, broad and plate-
like, has a somewhat twisted appearance, due to the fact that for most
of its length the principal diameter is transverse, while at the distal end
the principal diameter is antero-posterior. The foramen for the frontal
artery is double and is placed rather more mesially than in the horse ;
another vascular foramen in each frontal is somewhat forward of and
internal to the first and may be either single or double; from it a well
defined groove passes forward to the nasal.
The nasals are very short, extending but a short distance over the pre-
maxillaries, and quite broad behind; each is decidedly convex trans-
versely, with a deep groove along the sutural line, and for some distance
from the front end the two bones may be well separated. For nearly
half their length, the nasals are not in contact with the maxillary and this
free portion contracts rapidly to the blunt anterior point; the fore part
of each nasal has a thin lateral border and a thick mesial border, making
the bone triangular in cross-section.
The premaxillaries are quite rhinocerotic in shape ; they are short, broad
and heavy, with broad dorsal surfaces and short ascending processes, which
do not reach the nasals; the palatine processes are relatively large, but
the incisive foramina are small. The maxillary is very large; the sub-
orbital portion is low, but the preorbital, or facial, portion is very high,
especially in view of the entirely brachyodont dentition ; a short process
of the maxillary, between the premaxilla and the nasal, forms part of the
boundary of the anterior nares ; the small infraorbital foramen is situated
far in advance of the orbit, above the anterior part of p* and is constantly
double. The hard palate is long, narrow, contracting slightly forward, and
deeply concave transversely. The palatines are rather small, extending
to the posterior margin of p*, and the posterior palatine foramina are in
the suture between the palatines and maxillaries. The posterior nares are
also relatively small, with nearly parallel sides ; the anterior border is oppo-
site the middle of m*. The pterygoids, which are inconspicuous and early
fuse with the alisphenoids, have no fossze or hamular processes.
The cranial foramina are quite characteristic and do not entirely agree
with those of either the artiodactyls or the perissodactyls. The optic
foramen and foramen lacerum anterius are near together and are enclosed
in a common, deep fossa ; the latter foramen is very large, especially in
18 PATAGONIAN EXPEDITIONS: PALZONTOLOGY.
dorso-ventral diameter. There is no distinct foramen rotundum, the large
foramen ovale, which is entirely within the alisphenoid, probably having
transmitted both the second and third branches of the trigeminal nerve.
No alisphenoid canal ispresent. Loss of the tympanic renders the eusta-
chian foramen and foramen lacerum medium indistinguishable, but the
course of the eustachian canal is probably indicated by a long, well-defined
groove on the alisphenoid. The glenoid foramen is large and conspicuous.
The foramen lacerum posterius notches the anterior border of the exocci-
pital, and the condylar foramen is almost concealed by the condyle, when
the skull is viewed from below; it opens into a small, but deep and con-
spicuous fossa on the exoccipital.
The mandible has considerable resemblance to that of Wyracodon, a
genus of rhinoceroses from the North American Oligocene; the two rami
are codssified at the symphysis, which is narrow, of no great length and
deeply concave on the dorsal side. The horizontal ramus is elongate,
rather shallow dorso-ventrally, but quite thick and stout. The ascending
ramus is rather broad and quite high, the condyle being raised wellabove
the level of the teeth; the angle, which is regularly rounded and thin,
projects prominently behind the condyle, with convex external and concave
internal face ; the masseteric fossa is quite small, but well defined, and is
situated very high upon the ascending ramus, reaching from the condyle
to the level of the alveolar border. ‘The condyle is sessile, so that there
is no definite sigmoid notch, and is much extended transversely, especially
toward the inner side; on the posterior face of the condyle, near the inner
end, is a considerable facet, which articulates with a corresponding surface
on the postglenoid process. The coronoid is high, rising much above the
condyle and, when the jaws are closed, projecting above the zygomatic
arch; it is thin, but moderately broad and is either erect, or inclined
slightly forward. “The inferior dental foramen is situated behind and a
little below mz, and there is a large mental foramen on each side below
the canine or pr.
Vertebral Column and Ribs (Pl. 1).—In no individual of the Protero-
theriidee has a complete series of vertebree been found, as yet. There is,
however, reason to believe that the formula was as follows: C. 7, Th. 15,
L. 6-7, 5S. 6,Cd.?. In one specimen belonging to the American Museum
(No. 9290), the neck is preserved with all the vertebree in place and 15
trunk vertebrae are also present. The neck is decidedly short and quite
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 19
stout and, as in all this family, is in very marked contrast to that of the
Macrauchenidze both in length and in the form of the individual vertebree.
The atlas (Pl. IV, figs. 2, 2a) is relatively rather long, as well as high
dorso-ventrally; the anterior cotyles are large, widely separated dorsally,
but closely approximated at the ventral ends; the neural canal is large
and subcircular, the neural arch is thick and quite broad in both directions,
without spine. The transverse processes are narrow, having hardly more
than half the fore-and-aft extension of the atlas and there is, of course,
no atlanteo-diapophysial foramen; the processes have a very elevated
position and ventral to them there is a deep fossa on each side of the
vertebra. The very short vertebrarterial canal perforates the base of the
transverse process.
The axis (Pl. IV, fig. 3) has a moderately elongate, broad and very
much depressed centrum, with prominent ventral keel; the cotyles for the
atlas are low and wide and have somewhat saddle-shaped faces; the
odontoid process is short, blunt and massive and is separated from the
cotyles by a deep sulcus on each side; the facet for the inferior arch of
the atlas is very strongly convex, extending more than half-way around
the odontoid. The neural canal is rather small and the pedicles of the
neural arch are quite narrow antero-posteriorly ; the neural spine is a large,
prominent, hatchet-shaped plate, which projects well over the third vertebra
and is very different from the long, low ridge seen in 7heosodon. The
vertebrarterial canal is of large diameter, but short, and pursues an oblique
course, from behind, upward and forward through the base of the trans-
verse process.
The third cervical has a short and somewhat opisthoccelous centrum,
and a low, broad neural arch, without spine, for nearly half of its antero-
posterior length is overhung by the spine of the axis, leaving no room for
one on the third vertebra. The transverse process is a large, oblique plate,
short transversely, but much extended antero-posteriorly, especially for-
ward, where it overlaps the centrum of the axis. The fourth cervical is so
like the third as to call for no particular description, further than to note
that it has a slightly smaller and more slender centrum. The three
remaining cervicals have centra which progressively decrease in length,
though only to a moderate degree, shorter neural arches, which are more
deeply incised between the postzygapophyses, and an increasing develop-
ment of the spines. On the fifth cervical the spine is still very incon-
20 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
Spicuous; it is much more prominent on the sixth and still more on the
seventh. The transverse processes are much less extended antero-pos-
teriorly than on the preceding vertebrze, but appear to be wider transversely.
As already pointed out, the neck as a whole is short, which is also true
of all of the known Santa Cruz representatives of the family. Taking the
basal length of the skull as 100, that of the neck is 72.2, as nearly as can
be calculated from the material now available.
The number of trunk vertebrze (Pl. I) is not definitely known, but it is
highly probable that this number was 21 or 22. Of these 15 were prob-
ably thoracic, and it is certain that there cannot have been less than 6
lumbars. Assuming that there were fifteen thoracic vertebrae, their com-
bined length, measured around the ventral curve of the spinal column, may
be calculated as approximately 136, the basal length of the skull being too.
The first thoracic vertebra has a broad, much depressed centrum, with
well defined ventral keel; the prezygapophyses are of the cervical type,
while the postzygapophyses have the thoracic pattern and are placed on
the ventral side of the neural arch; the neural spine is not very high and
_ is quite slender, with a moderate inclination backward; the transverse
processes are heavy and prominent and bear large facets for the ribs. After
an interval of perhaps four vertebrae, not represented in the collections,
follows a series of four in their natural connection. These have rather
small, slightly depressed and somewhat opisthoccelous centra, of the ordi-
nary ungulate type, and slender neural spines which are strongly inclined
posteriorly. In the figure of the skeleton (PI. I) this inclination does not
appear so marked, because of the oblique position of the centra in this
part of the column. The transverse processes are quite prominent and
arise high up on the sides of the neural arch.
In the posterior part of the thoracic region the centra are larger than in
the median portion and quite broad and depressed; the zygapophyses
are cylindrical and interlocking, very much like those typical of the Artio-
dactyla, and the metapophyses are very prominent. The short transverse
processes still arise from the neural arches rather than from the centra;
even on the last thoracic these processes have facets for the rib-tubercles.
The neural spines, which are rather low, are thin transversely, plate-like and
broad antero-posteriorly. The penultimate thoracic is the anticlinal verte-
bra, the neural spine of the last one having a distinct forward inclination.
The lumbar formula in Diadiaphorus is 6—7 though not more than six
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 21
of these vertebrze have been found in association with any one individual.
The lumbars (PI. IV, figs. 4-5) have elongate and rather narrow centra,
which are but moderately depressed ; they are quite sharply constricted in
the middle and have low, sharp ventral keels; only in the last vertebra
does the centrum become notably broad and low. The neural canal is
quite small and the neural spines are relatively short, with a strong for-
ward inclination; transversely these spines are much compressed and thin,
antero-posteriorly they are broad at the base, narrowing to the tip; the
zygapophyses are cylindrical and interlocking, as in the posterior tho-
racic region, and the metapophyses are very prominent. On most of the
lumbars the transverse processes are long, depressed, tapering and antro-
verted, but on the last two they are short and very broad, becoming on
the last one broader than the antero-posterior diameter of the centrum
and forming a pair of exceedingly large plates ; on the anterior border of
each process is a well-defined articular facet for a corresponding surface on
the transverse process of the penultimate lumbar, and on the hinder bor-
der a still larger one for the first sacral.
The sacrum consists of six vertebree, of which only the first two sup-
port the ilium; the centra diminish in size posteriorly, becoming very
small in the last three vertebrz, as does also the neural canal. None of
the sacral vertebree has a neural spine, but the metapophyses of the last
four are connected by high, continuous ridges, making this region trans-
versely concave: the neural arches are not everywhere continuous, but
leave a median vacuity between each successive pair of vertebra. On
each transverse process of the first sacral is a large convexity, which articu-
lates with the concave facet on the transverse process of the last lumbar,
as already described.
No caudal vertebrze of this genus have yet been identified, but, from
the small size of the last sacral and the great reduction in the diameter of
its neural canal, it is evident that the tail must have been short.
A few fragments show that the ribs are laterally compressed and plate-
like and, though not very broad, they are of the usual ungulate character.
Nothing is yet known of the sternum.
A ppendicular Skeleton.—The skeleton of the limbs and feet is very
fully known. The scapula (Pl. I) is known, as yet, in only two genera
of this family, Déadiaphorus and Proterotherium, and, though the bone is
quite different in shape in these two genera, there are no structural differ-
22 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
ences of importance. In Deadzaphorus the blade is high, narrow and of
subquadrate outline, and across it the prominent spine pursues an oblique
course, dividing it into two nearly equal, triangular areas. Of these, the
anterior, or prescapular fossa is wider distally, while the postscapular fossa is
wider proximally. The neck is broad, especially the portion in front of
the spine, and the glenoid cavity is a simply concave oval, with the antero-
posterior diameter somewhat exceeding the transverse. The coracoid is
a large and rugose, but not conspicuous, rounded tubercle. There is a
distinct, though shallow, coraco-scapular notch, above which the coracoid
border is strongly convex and curves gradually into the suprascapular
border. In the only available specimen of the scapula of Dzadiaphorus
the postero-superior portion is broken away, but the strongly inclined
course of so much of the glenoid border as is preserved, indicates that the
proximal portion of the postscapular fossa was very broad.
The spine is prominent and recurved, making the anterior surface convex
and the posterior concave. There is a single, well-developed metacromion,
which is much more distal in position than that of the Macrauchenide ;
the acromion itself is broken and may not have been continued distally,
but, nevertheless, stands out very prominently from the neck. This is in
marked contrast with the Perissodactyla, in which the spine dies away
gradually upon the neck.
No trace of a clavicle has been found in this or any other representative
of the Litopterna.
The humerus (PI. IV, figs. 6, 62) is short and stout, with large head
projecting prominently behind the plane of the shaft; the great tuber-
osity is high and the deltoid ridge is very long, extending down more
than half the length of the shaft, upon which it dies away gradually,
not forming any prominence or hook. ‘The distal trochlea is rather narrow
and of very simple form, without division into separate facets, and the
internal border has a very prominent flange for the ulna. Both the an-
coneal and the supratrochlear fossze are small, but deep, and are connected
by an irregular perforation ; the external epicondyle is distinct, while the
internal one is obsolete, but the postero-internal angle of the distal end
is a prominent rugosity, somewhat as in the horse; the supinator ridge
is distinct, though not prominent.
The fore-arm bones are quite short in relation to the humerus and are
in contact for most of their length, making but a short and narrow radio-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 23
cubital arcade. The radius (Pl. IV, figs. 7, 7@) is relatively slender ; its
head, though occupying the whole width of the humeral trochlea, is not
broad, and has a transversely oval, antero-posteriorly compressed shape;
on the inner side of the head is a small, oblique facet, which abuts against
the internal flange of the humeral trochlea; this facet is continuous with
the proximal articular surface, which is composed of a low internal con-
vexity and a very shallow external concavity. The proximal ulnar facet
is very small and is confined to the postero-internal side of the head. On
the internal side of the shaft, just below the head, is the large and rugose, but
low, bicipital tubercle. The shaft is moderately arched forward and inward
and is of transversely oval cross-section, broadening slightly to the distal
end. Thedistal end is quite heavy, with a single broad and shallow tendinal
sulcus on the dorsal surface; there is a small facet for the ulna on the
external side. The facets for the scaphoid and lunar are sharply demar-
cated by a ridge and are concave dorsally, becoming convex toward the
palmar side; the lunar facet is reflected farther upward upon the palmar
aspect of the bone than is that for the scaphoid.
In view of the degree of digital reduction in the manus, which is func-
tionally all but monodactyl, the ulna (Pl. IV, fig. 8) is surprisingly large
and heavy, relatively quite as stout asin the tapir. The olecranon is well
developed and is much thickened and rugose at the free end; it projects
upward and backward, extending well behind the plane of the shaft; the
coronoid process is very prominent and the -sigmoid notch quite deep,
though short proximo-distally, its articular surface is continuous, but dis-
tally the external portion is produced considerably farther, extending
around the head of the radius, for which it has a small facet. The shaft
is strongly arched forward and very heavy, of subtrihedral cross-section and
contracting slightly to the distal end. The distal facet for the radius is a
small, but prominent oval convexity; the pyramidal facet is relatively large
and simply convex, while that for the pisiform is exceedingly small.
As Ameghino has shown (944, p. 266) the manus (PI. V, figs. 1, 12, 18, 3, 4)
has undergone a remarkable degree of reduction and bears a striking,
though entirely superficial, likeness to that of one of the three-toed horses,
such as Protohippus, for example. The carpus is not at all equine, or even
perissodactyl, in character and may be defined as semi-taxeopod, the
scaphoid articulating with the magnum, but the lunar not coming into
contact with the unciform. In the carpo-metacarpal connections, this
24 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
manus is an excellent example of what Kowalevsky has called the ‘‘ina-
daptive”’ method of reduction in the Artiodactyla.
The scaphoid is a large, nearly cubical bone; its proximal end is covered
by the radial facet, which is convex on the dorsal, concave on the palmar
side; distally, it articulates with the trapezium, trapezoid and magnum;
the facet for the trapezium is small, that for the trapezoid is the largest of
the three and deeply concave, while the articulation with the magnum is
quite extensive and is made by a process which descends below the level
of the trapezoid facet.
The lunar is quite large, exceeding the scaphoid in proximo-distal length;
the radial facet consists of two parts, a dorsal portion, which is broad,
convex and oblique, rising quite steeply toward the ulnar side, and a much
narrower palmar extension, which is saddle-shaped. Distally, the lunar
rests entirely upon the magnum and is very widely separated from the
unciform.
In proximo-distal diameter, the pyramidal is much the longest of the
carpal elements, almost equalling the combined lunar and magnum in
length, but in width and thickness it is considerably inferior to the scaph-
oid; the ulnar facet is of moderate size and slightly convex, and is
continuous with that for the pisiform, which is narrow, oblique and slightly
saddle-shaped. Distally, the bone is covered by a large, concave facet for
the unciform, while on the radial side of the distal end is a large surface
for the magnum, which is an unusual arrangement in an ungulate carpus.
In the present genus the pisiform is still unknown.
In view of the tridactyl and functionally monodactyl character of the
manus, the trapezium is quite large; itis of an irregularly polygonal shape,
with the maximum diameter directed proximo-distally, and is so displaced
toward the palmar side as to be almost invisible when the manus is seen
from the front: the trapezium articulates with the scaphoid, trapezoid and
second metacarpal. The trapezoid is not very much larger than the tra-
pezium and, like the latter, its principal diameter is the proximo-distal one:
proximally it has a slightly convex facet for the scaphoid and on the ulnar
side are two facets, for the scaphoid and magnum respectively, which meet
at a very open angle; distally, the trapezoid articulates only with mc. II.
In correlation with the great enlargement of me. III, the magnum is
much the largest bone of the distal row, but is quite unlike that of the
horses in shape, being longer proximo-distally and narrower transversly
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 25
than in that phylum : the proximal end is divided unequally between
the scaphoid and lunar facets, the latter being somewhat, the smaller of
the two: on the radial side are two nearly equal facets for the trapezoid
and me. II; the distal facet for mc. III is convex and oblique, rising toward
the ulnar side, on which is a relatively large, concave surface for the pyram-
idal: there is no articulation with the unciform.
The unciform, though considerably larger than the trapezoid, is yet much
smaller than the magnum: it is narrow, thick and moderately elongate
proximo-distally: in correlation with the great length of the pyramidal,
the unciform projects much farther distally than any of the other carpals,
its proximal surface being below the distal end of the trapezoid. Conse-
quently, as already noted, there is no contact between the magnum and
unciform, the radial side of the latter being covered by the process of mc.
III: on the distal end is a concave facet for the head of mc. IV and, palmar
to this, a small surface for the rudimentary me. V.
The metacarpus is tridactyl and mesaxonic and, though the lateral
digits have their full complement of phalanges, they are mere dew-claws and
can have had little or no functional importance. Ameghino states (940,
p. 268) that in this genus there is a vestigial mc. I, which is quite long and
extremely slender and is placed on the palmar side of the manus. I have
seen no example of this.
Metacarpal II is much shorter and very much more slender than me.
III; the proximal end is relatively heavy and quite extensively overlaps
the head of mc. III and abuts against the radial side of the magnum, thus
entirely excluding me. III from any contact with the trapezoid. The shaft
is slender, much compressed laterally, but of considerable dorso-palmar
diameter, and has a strong forward curvature; the distal trochlea is very
narrow, but has a well-defined carina, which is reflected over upon the
dorsal face of the trochlea.
Metacarpal III is very stout and moderately elongate; the proximal end
is supported only by the magnum, for though there is quite an extensive
articulation with the unciform, this contact is entirely lateral. On the
other hand, the overlapping head of mc. II, by means of which part of the
weight is transmitted from the radius through the scaphoid and trapezoid
to me. III, may be regarded as functionally equivalent to another carpal
element. On the ulnar side, mc. III hardly projects at all over the head
of mc. IV. The shaft is heavy, palmo-dorsally compressed and broad
26 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
transversely, increasing in width toward the distal end; for nearly half its
length, the shaft has on each side a broad, shallow depression, to receive
the lateral metacarpals; on the dorsal side, near the radial border of the
proximal end, is a prominent tubercle for the attachment of the extensor
tendon. The distal trochlea is broad and very low proximo-distally, but
has a very prominent carina, which extends around the entire dorsal face
of the trochlea, quite as in the horses.
Metacarpal IV is the counterpart of mc. II: proximally, it is overlapped
but little by the head of mc. III and articulates with the unciform by
means of a slightly convex facet.
A vestige of metacarpal V is attached to the unciform and me. IV, and
is a very small, almond-shaped bone, ending distally in a blunt point.
The phalanges of the lateral digits are small, slender, laterally com-
pressed and resemble quite closely those of Profohippus : the unguals are
pointed and somewhat irregularly shaped. On the contrary, the phalanges
of the median digit are greatly elongated, together exceeding the meta-
carpal in length, and have a marked resemblance to those of the horses.
The proximal phalanx is especially long and is also broad, but is much
depressed palmo-dorsally: the proximal end is very broad and has a shal-
low, concave trochlea, deeply grooved in the median line to receive the
metacarpal carina, which, however, does not notch the dorsal border of
the trochlea. Below the proximal end the shaft at first narrows rapidly, then
more gradually, broadening again somewhat at the distal end: the distal
trochlea is very low and saddle-shaped, concave transversely and convex
palmo-dorsally.
The second phalanx is short and broad; the proximal end is quite thick
in the dorso-palmar dimension, but this thickness diminishes rapidly and
the distal end is strongly depressed: the proximal trochlea is a single
transverse groove, without such intercondylar ridge, or division into two
facets, as may be seen in the horses: the distal trochlea also lacks the
median groove of the equines and is more depressed. The ungual
phalanx is exceedingly like that of such three-toed equine genera as Pvo-
tohippus , itis broad, depressed, with rounded free border and conspicuous
median cleft at the distal end: the proximal trochlea is an undivided trans-
verse groove, and the lateral processes are moderately well developed :
the palmar surface is slightly concave, with a deep crescentic concavity near
the proximal end.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 27
Despite its resemblance to that of the horses, the manus of Diadzaphorus
is fundamentally different. Inthe carpus we find a retention of semi-taxeo-
pod conditions, in that the lunar is far removed from the unciform and
rests entirely upon the magnum. The carpals of the distal row, especially
the magnum, are much narrower than in the equine manus, while the
large, functional third metacarpal supports only the magnum, not extend-
ing, even on the palmar side, beneath the unciform on one side and the
trapezoid on the other, as it so conspicuously does in the horses, and the
second metacarpal retains its full connection with the magnum. As com-
pared with that of the horses, the metacarpal of the median digit is rela-
tively short, while the phalanges of this digit are very elongate. In brief,
the Santa Cruz genus, despite its markedly advanced degree of special-
ization in foot-structure, yet retains a surprising number of primitive
characteristics.
Like so many other elements of the appendicular skeleton, the pelvis
(Pl. I) has a decidedly equine appearance. The ilium has a shorter and
much broader peduncle, which expands anteriorly into a broad plate of very
similar shape to that of the horses, with median portion sharply curved up-
ward, to articulate with the sacrum, much as in the horse, but the external por-
tion has no such heavy crista asin the latter: the iliac surface is very broad
and the ilio-pectineal process is prominent and projects almost directly
inward. The acetabulum has a prominent border, which anteriorly be-
comes very heavy and rugose ; it is extensively invaded from the ventral side
by a large and deep sulcus for the round ligament. ‘The ischium is rather
short and slender and its dorsal ramus is trihedral, flattening posteriorly
into a strongly everted plate; the tuberosity is a conspicuous, but rather
slender spine-like process. The pubis is short, stout and much depressed,
and forms a long symphysis with its fellow of the opposite side. The
obturator foramen is relatively quite small and of irregularly oval shape.
Of all the bones in the skeleton, the one which is most strikingly horse-
like in character is the femur (Pl. III, fig. 6). The head is quite small,
and of depressed and somewhat irregular shape, and sessile ; the pit for
the round ligament is a V-shaped incision on the postero-internal side of
the head, much like that of the horse in shape and position, but smaller
and shallower. The great trochanter is very large, rising high above the
head, but less massive than in Aguas, and not divided by a sulcus into
two parts, as it is in the horses ; the digital fossa is large and deep: the
28 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
second trochanter is a compressed conical tuberosity, prolonged distally
into a ridge; the third trochanter is prominent, though rather small, and
has a more distal position than in Aguas: the shaft is long, quite slender
and laterally compressed. All of the femora certainly referable to the
present genus, which I have seen, are so injured that the pit for the
plantaris muscle is not shown, but as this fossa appears in all the other
genera of the family, it was doubtless present in Diadzaphorus also. The
trochlea is asymmetrical, with the inner border decidedly more promi-
nent than the outer, and the suprapatellar fossa is deep: the condyles are
quite small, projecting but little behind the plane of the shaft, and are
asymmetrical, the external one being larger and more convex than the
internal : there are no distinct tuberosities.
The patella is strikingly different from that of 7/eosodon, being short
proximo-distally, broad, very thick, and rugose on the anterior surface,
while the articular facet for the femoral trochlea is quite small.
As in all of the Santa Cruz representatives of the Litopterna, the leg-
bones (PI. III, fig. 7) are separate. The tibia is quite stout and somewhat
shorter than the femur; the condyles are widely separated, making a bifid
spine: the cnemial crest is prominent and very heavy proximally, but
extends only a short distance down the shaft and terminates abruptly, and
the sulcus for the tendon of the ex/ensor longus digitorum is much shal-
lower than in Aguus. The shaft is stout, almost straight and of subtri-
hedral section, becoming transversely oval near the distal end, which is
somewhat broadened and thickened: the astragalar surface is divided into
two unequal facets, of which the internal is the larger, by an intercondylar
ridge, which projects as a prominent tongue on both dorsal and plantar
sides, and is especially heavy on the latter; the dorsal tongue bears an
articular surface for the pit on the neck of the astragalus; the internal
malleolus is much reduced.
The fibula is far more reduced than the ulna: the shaft is straight, slender,
laterally compressed and of irregularly trihedral shape; near the distal end
it becomes quite thick antero-posteriorly, but remains narrow transversely :
on the external side of the distal end is a very deep sulcus for the peroneal
tendon, the borders of which groove are thickened and form tubercles
distally. The distal facet for the tibia is small and confluent with the
large plane surface for the astragalus; the calcaneal facet is relatively large
and quite complex, being composed of an anterior convexity and a pos-
terior concavity.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 29
Like the manus (PI. V, figs. 2, 2a), the pes has a striking, but essentially
superficial resemblance to that of the horses, the tarsus being even more
radically different from the perissodactyl type than is the carpus.
The astragalus is more artiodactyl than perissodactyl in character, though
sufficiently unlike the former group; it is narrow and elongate and has a
deeply grooved trochlea, which is slightly asymmetrical, owing to the
somewhat larger size of the external condyle: the neck is long, especially
on the tibial side, ending in quite a broad, depressed and convex head for
the navicular, but there is no contact with the cuboid, which is widely
removed from the astragalus. The external calcaneal facet is large and
so oblique as to have a lateral rather than a plantar presentation ; the sus-
tentacular facet has quite an artiodactyl appearance, being long and gently
convex proximo-distally, and becoming confluent with the navicular facet,
but is not of uniform width, broadening regularly to the distal end: a small
third facet for the calcaneum is on the outer side of the head. The navic-
ular facet is broad and convex, and, toward the fibular side, is reflected well
over upon the dorsal side of the neck, so that the proximal border of
the facet descends steeply from the fibular to the tibial side.
The calcaneum is long and is remarkable for the elongation of the portion
distal to the fibular facet: the tuber is much compressed laterally, thick
planto-dorsally, and has nearly parallel borders; the free end is thick and
rugose, but has no tendinal sulcus, such as occurs in the Artiodactyla; the
fibular facet is narrow, but quite elongate proximo-distally, and is made
up of a posterior convexity and an anterior concavity; the external astra-
galar facet is large, convex and oblique, presenting inward more than
dorsally. The sustentaculum is prominent and thick and its articular
surface is continued for some distance upon the body of the calcaneum,
extending to the third astragalar facet. On the tibial side, below the last
named facet, is an articular surface for the navicular. As already observed,
the distal portion of the calcaneum is very long and laterally compressed,
and together with the prominent fibular facet, gives a somewhat artio-
dactyl appearance to the bone; the cuboid facet is deeply concave planto-
dorsally and oblique transversely, descending steeply toward the fibular side.
The navicular is broad and also relatively elongate proximo-distally,
strikingly so as compared with the flattened, disc-like navicular of the horse:
from the plantar face is given off a very long and heavy hook-like process :
the astragalar facet is slightly concave transversely, deeply so in the dorso-
30 PATAGONIAN EXPEDITIONS: PALZONTOLOGY.
plantar direction, with the plantar border raised much higher than the
dorsal. The distal end is almost entirely occupied by the very large facet
for the ectocuneiform, which surface is also slightly concave planto-dorsally :
the facet for the middle cuneiform is extremely small and that for the
internal one is entirely lateral, or postero-lateral in position.
The entocuneiform is a large, flattened, scale-like bone, which is so far
displaced to the plantar side as hardly to be visible when the pes is seen
from the front, and its connections are entirely lateral, with the navicular,
mesocuneiform and-second metatarsal respectively. The mesocuneiform
is extremely small, with nearly square dorsal face; it likewise is much dis-
placed toward the plantar side and articulates only with mt. II, not touching
mt. III at all. The ectocuneiform is very large, much the largest bone of
the distal row, and nearly equals the navicular in size ; it has, as compared
with that of the horses, considerable proximo-distal diameter, and thus
helps materially in making up the great length of the tarsus, which is so
striking a feature of this pes. Transversely, the proximal border is concave
and the distal convex.
The cuboid is quite small, especially in width, the length on the plantar
side being considerable and the thickness planto-dorsally being much the
greatest of its diameters, which is due to the large and massive, though
not elongate, hook-like process from the plantar side: the proximal surface
for the calcaneum is saddle-shaped, concave and very oblique transversly,
convex planto-dorsally ; the distal end has a small, plane facet for mt. IV
and, internal to this, a small oblique surface for mt. III.
The metatarsals resemble the metacarpals in size and proportions and
in their inadaptive method of reduction. Metatarsal II is very much like
me. II; the proximal end bears a small facet for the mesocuneiform and
on the plantar side another for the entocuneiform ; it does not overlap the
head of mt. III and apparently has no contact with the ectocuneiform,
though I cannot satisfy myself entirely onthis point. Metatarsal III bears
the whole weight of the limb and is supported only by the ectocuneiform,
the limited contact with the cuboid being obliquely lateral, and there is no
articulation with the mesocuneiform. As a whole, the bone closely
resembles me. III, but is somewhat thicker planto-dorsally, and the process
from the plantar side of the proximal end is much longer and more slender.
In all of the specimens which I have examined me. III is of nearly the same
length as mt. IJ. Ameghino’s figures ('940, pp. 266-7, figs. 8-9) make
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 31
mt. III longer, but he does not state that manus and pes were derived
from the same individual. Metatarsal IV is very like the corresponding
metacarpal and its proximal end is hardly at all overlapped by that of mt. III.
The phalanges resemble those of the manus, but those of the functional
digit III are somewhat longer, more slender, more depressed and flattened,
while the ungual is decidedly longer, narrower and more pointed than is
that of the manus.
Restoration (Pl. 1). — The chief difficulty in the way of making a satis-
factory restoration of Diadzaphorus is the uncertainty as to the number of
trunk-vertebrze, which, of course, has an important effect in determining
the appearance and proportions of the animal. Ingeneral appearance, the
skeleton of Diadtaphorus bears considerable resemblance to that of Wyra-
codon, the lightly built, cursorial rhinoceros from the Oligocene of North
America, though an immediately obvious difference is the much shorter
neck of the Santa Cruz genus. The head is relatively rather small, though
deep and heavy dorso-ventrally, and the very short nasals are especially
characteristic of this genus. The neck is short, hardly equaling three-
quarters of the basal length of the skull, and quite slender, which is due
to the small size of the vertebreze and the shortness of the neural spines,
save that of the axis.
For reasons that have been sufficiently explained in the foregoing pages
(p. 10), 1t has been assumed that the number of trunk-vertebrz was 21, of
which 15 have been assigned to the thoracic and 6 to the lumbar region.
The back appears to have been nearly straight, without hump at the
shoulders, and with rather short and slender spines. The thorax was
probably long and the loins rather short. The caudal vertebre are still
quite unknown, but from the character of the sacrum it isevident that the
tail was short.
The limbs are moderately elongate and slender and resemble much
those of the three-toed horses, such as Profohippus. The humerus is
rather short and the fore-arm bones, which remain separate, are somewhat
longer. Femurand tibia, on the other hand, are of nearly the same length.
The tridactyl feet are also elongate, but this elongation is largely due to
the length of the phalanges, carpus and tarsus, the metapodials being
relatively much shorter than in the horses. Though the feet have three
complete digits each, only the median digit touches the ground, while the
laterals are mere dew-claws.
32 PATAGONIAN EXPEDITIONS: PALA®ONTOLOGY.
DIADIAPHORUS MAJUSCULUS Ameghino.
(Plates I; II, Figs. 1, 1a, 2; Ill, Figs, 4-7; IV; V; XIII, Fig. 9.)
D. mausculus Amegh.; Enum. sistematica, etc., 1887, p. 20.
D. diplinthius Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891, p. 298.
Bunodontherium moajusculum Mercerat; Revista del Museo de La Plata,
Gel Soi ps4 5A.
B. patagonicum Mercerat ; Ibid., p. 453 (fide Ameghino).
Oreomeryx Rutimeyert Mercerat; Ibid., p. 469 (fide Ameghino).
This is by far the commonest and best known representative of the
genus and the only one of which any considerable part of the skeleton
has been recovered: consequently, the diagnosis of this species, as of the
others, must be drawn principally from the teeth.
In D. majusculus the upper caniniform incisor is moderately heavy and
is followed bya long diastema. In the upper molars the posterior conule
is placed close to the postero-external cusp and separated by a deep cleft
from the postero-internal, so that even in well worn teeth the posterior
fossa still communicates with the median valley. The postero-external
cusp of m% is reduced in size to a degree which varies somewhat in dif-
ferent individuals. The development of the internal cingulum on the
upper teeth is subject to considerable individual variation and does not
afford a trustworthy criterion for the discrimination of species.
In the lower jaw, the small median incisors are separated by short inter-
spaces from each other and from the caniniform laterals, which are quite
large and but moderately divergent. The canine is isolated by very short
diastemata in front of and behind it and the second premolar has a fore-
and-aft position parallel with the axis of the jaw.
In the following table No. 1 is a cast of the type specimen of D. aplin-
thius , No. 9291 is a very perfect skull and mandible in the American
Museum of Natural History, and No. 9270, of the same collection, com-
prises a large part of the skeleton of an old and rather small individual,
perhaps a female, while No. 15,799 is the most complete skeleton in the
Princeton Museum.
MEASUREMENTS.
Vo. No. No.
No. Tt. 15,799. 9291. 9270.
Upper dentition, length . : é : 2 : .156 .150 145
Upper incisor, antero-posterior diameter . . : .009 .009
oe «transverse diameter . : : : .007 .007
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS.
No.r.
Diastema between i% and p+
Upper premolar-molar series, length
«premolar series, length .
Pt, length (2. ¢., antero-posterior diameter)
“ width (2. ¢., transverse diameter)
P2, length
“ width : : : 6 : ¢
P23 length . F ; : : : ; ; .O165
“ width 4 j ; ; : ; ; : .O185
P4, length . F ‘ i F , : : O18
“width . : ; 6 . : c .020
Upper molar series, length : : é
Mi, length . : ; : : : : 6 .O19
vyichi : . : : . : : .022
M2, length : : : : : :
“width «. : ; : : : : : No.
M3, length . : : ; c . ‘ 5 OOO.
“width ; : :
Lower dentition, length .
I,, greater diameter } : , 6 5 : .0085
“ lesser Coes : ‘ 5 é : : .0065
Lower premolar-molar series, length F 5 6 .109
«« premolar series, length ° : : 6 .054
P,, length . ; 0 : : . ; : .009
Cewiiclt hens : : : . : ; : .005
P,, length . 6 : : : : 6 ; .O14
“ width . F : : : : : : .0095
Pz, length . : i : : F 5 ; .O15
“width . : . c : . . 5 .O12
Pz, length . : ¢ : 2 : : 6 .O16
“width «. : F i : : : c .O14
Lower molar series, length . 6 : j . 055
M,,length . ; ; é 5 5 3 6 .016
cc itd : : ; : ‘ : ; .0135
M,, length . : : : : 0 ; : .019
Cwicltiin a: z ; ; : ‘ j : .O14
M,;,length . Aiea : : : : : .0205
“width .O10
Skull, length from occipital condyles to premaxilla incl.
Cranium, length to anterior edge of orbit
Face, length orbit to premaxilla
““ dorso-ventral height at m+
Occiput, height
No.
I5;799,
.027
.11Q
.0635
.O12
.O105
.O16
.018
.O17
.020
.020
.O21
.0583
.0205
.023
.0235
.025
.019
.022
.140
.009
.006
.125
.062
.0096
.006
-O15
.0085
.019
OIL
.O19
.0125
.063
.018
-O14
.O21
-O155
.0215
.O13
No.
9201.
.024
.118
.063
.O125
O15
O17
018
.058
.018
.023
.018
-1515
.008
sai
.062
.O10
.O14
O17
.O18
.059
.O17
.020
33
No.
9270.
.027
.109
.056
O12
.009
.O14
.O15
.O15
.018
.O15
.020
:053
.O17
O19
10235
.O17
O21
.143
239
-139
.108
.075
34 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
No. No. No. No.
9196. 15,799. 929T. 9270.
Occiput, width at base . : 3 6 3 .057 064,
Sagittal crest, length . 5 ; : ‘ : .097 -108
Zygomatic arch, length . F : : P ek any -101
Skull, width over zygomatic arches : : : 123 125
“_interorbital width : : : : : .080 .085
Nasals, length in median line . : : : ' .054
Mandible, length . é 5 0 : : . 223 .214
é height at condyle . : . 5 ° .107 .O81
sf «© coronoid . : 6 : : .I1O
re depth atm, . 5 6 : : 5 .034 .040 .035
“ Sami Dea: : 6 ‘ : .026 028 .025
ge length of siiphests : .048 .040 .045
N. B. The apparent discrepancies in the noite meeeners are due to the overlapping of
the teeth.
No. Vo. Vo.
9196. 15,799. 9270.
Atlas, length . : a : ‘ - : : .052 .054.
“« _ width over anterior eevee 3 : : i } 4 .055 .053
Axis, length of centrum . : . 3 : : ; ; ?.044 -044,
“width of anterior end : : : : ; : : .048
“length of odontoid . é : : : 2 . . .O17
OF sipproliinn ss é 5 : : ; : 4 -O125
5th cervical, length of Sota : j : : : : : .028
cs G width of anterior face. 0 : 3 : c .O21
Ist thoracic, length of centrum . : 5 : : : ; .022 .026
a as width of anterior face . : ; < : : -023
oY fs “over transverse processes . : : ; ..062
?4th lumbar, length of centrum : ; : : : 2 .034 .036
as width of anterior face . : : 0 3 . .025 023
ss ss height to end of spine . : : . 2 > .060
?6th es length of centrum. . ‘ 5 . : : .0315 .034
ce ce width of anterior face . : : é : ; .0265 .024
cs ‘ ““ over transverse processes . ; ° : .078
Sacrum, length : : : : j . ; : .128
Ist sacral, width of anterior fee 5 t 2 a ee ¢ .023
Last sacral, length . : : : ‘ : : 2 : .O15
«c __ «_~_ width of posterior face. 4 0 : . é .0085
Humerus, length from head : : 0 : : : ; a7 .176
ss distal width over epicondyles . ‘ : : : .0425 .043
“ width of trochlea : 5 : : : : : .0265 .027
Radius, length . : ‘ : é : : 5 5 ; Stal
“width of proximal end . ; 9 3 F : ; .026
ss emcurcistaleend : F o 0 : 0 . .025 .029
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 35
No. No. No.
9190. 15,799. 9270.
Ulna, length . é : : : ; : : c , .200
sf “of olecranon . ; é : j 5 ¢ ‘ .053
“width at sigmoid notch . : : ‘ : : 6 .027
ot “of distal end . P 0° 5 C : . .O13 .O14
* Carpus, lengthin median line. : ; 5 : : ; .025
fe greatest width . é é ; : : : 5 .037
Metacarpal II, length . : : F i : : ; .080
ft “ width of proximal end ; ‘ : : 6 .O10 .O10
< c Gc ohstail emel . ; : : : 0 .008
«6 Ill, length . : 0 : : : f j .092 .093
gs “width of proximal en : : ‘ ; ; .023 .025
ee a « “distal end . ‘ ; j j c .027 .030
ag IV, length . Y ‘ i F : : : .075
“a “width of proximalend . ; 3 : ; .006 .007
« « «distal end . ; : ; : : .008
Digit II, phalanx 1, length . : c : c : : .020
CO a «I, proximal width ‘ , ; F 3 .0095
SESS GE 2 leno the : ; ; . : : .O10
Ser see «2, proximal width : : . b d .008
ee Ses elenschi : 0 c c : D . +?.013
Digit III, phalanx 1, length . : : : ; ; j .047 -052
ae “I, proximal width : ; ; E : .025 .029
Spares a Ts “thickness . : : é : .O15 .O15
Soe «1, distal width . , 5 : - 5 .020 .022
Serie eee mn thicktress ; : : ‘ i .OII
sts a, eatin 5 : : ; 5 i .020 .025
a «2, proximal width : é 6 : F 023 .027
GAS «2, distal width. : ; : c é .O14
gas cog hematin d . ; : : : .0355
oe es “3, proximal width c c c 5 : .0325 .033
bor ie Siete «thickness . ; : ! : .O10 .O12
Femur, length from head ‘ ; : : é : : 224
‘s “s “great trochanter ¢ : : é : .238
«width of proximal end f : : c J é .O61
as «« —« distal end over condyles . 3 : : : £048 .O51
“ « —_ “ rotular groove ; : ; : c : .028 .032
Tibia, length (exclusive of spine) : : : : : : .198 .193
“proximal width ; . : : 5 0 c : .050 .049
“distal width . : ; ; : c 0 . : .027 .035 .032
fs “thickness : ; : : : é 6 : .027 .036 .032
Fibula, distal width 6 ; 4 F : : : F .006 .006
es “thickness . 5 % , , ; 4 ‘ .020 .022 .O21
36 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
No. No. No.
9196. 15,799. 9270.
Tarsus, length from external astragalar condyle d : . .060 .068
“greatest width . : ; : ; ‘ : 2 .031 .036
Astragalus, length . : : : ° ; 9 q : .039 .044. .044
ih width of trochlea . : 0 ‘ ; ; ¢ .022 .026 .024
cs length of neck on fibular side . ; j : : OIL .O13 .013
Calcaneum, length . : 5 : é : . 5 : .088 .086
of «of tuber . i ‘ : : : : .044 .043
fs width of free end . : A : : . : .O21 .018
" « ‘distal end A : ‘ : : : -OIL .O12
Ectocuneiform, length in median line ; : : F : -O1I5 .OIL .OII
“ width : , : : : 4 : : .0205 .022 .023
Metatarsal II, length . : : : : : : : .072 .078
“ «(proximal width. ; : ; 5 5 : .0055
ef “ s thickness . ; : : 4 : .O13 .O15
a “distal width . F : ; : ‘ ; .007 .008
Metatarsal III, length . : , : ’ : : 5 .092 .092 .094
f “ proximal width : : . 3 é é .024 .026 .024
sf “distal width . 3 : ; : : : .027 .0255
Metatarsal IV, length . : : ; : : d : .O71
ss “distal width . 5 : : . : : .0075
Pes, digit III, phalanx 1, length é : d 5 : : .049
SE lemme “I, proximal width . : ; : : .024
Ente «1, distal width : Bate ane : : .0205
EG epider G 2, leer 5 : 6 ; | .O195
Siti aCe «2, proximal width . . b : : .022
tag 08 C2 adistallawidthyane : 3 : : .020
Shige) EB Be ss 3, proximal width . : 6 : : .028
Cen, ee sete 3) Ws thickness . , : : .OII
Pes, digit IV, phalanx 1, length . : é : 2 . .020
SEH eG ie EE &s I, proximal width ; c ; : .008
AS ae 2len otha : : 0 A : .009
fe EP EE a 2, proximal width : ; : ; .0063
The proportions of these two specimens (Nos. 9196 and 9270) differ so
much as to suggest that they belong to different species, possibly even to
different genera: No. 15,799, on the other hand, agrees well with Ame-
ghino’s figures.
Localities. —No. 15,799 was collected by Mr. Peterson on the Pata-
gonian coast, ten miles south of Coy Inlet: No. 9196 (A. M. N. H.) was
obtained by Mr. Brown, thirty miles south of Santa Cruz.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. * 37
DIADIAPHORUS ROBUSTUS Ameghino.
‘(Plate III, Figs. 1-3.)
D. robustus Amegh.; Enum. Synopt. des Mamm. Foss. de Patagonie,
1894, p. 47.
D. mayjusculus Lydekker, in part; Anales del Museo de La Plata, T. II,
1893, Pp. 59-
D. coelops Amegh.; Anales del Museo Nacional de Buenos Aires, Ser. 3,
ah. WUD, io. AGG
This species, which is not represented in the Princeton or the New York
collections, is known to me only from a cast of the type-specimen and from
Lydekker’s figure (’93, Pl. XXIV, fig. 2). These indicate an animal of
about the same size as D. majusculus, but rather more robust. The upper
tusk is considerably stouter and is followed by a shorter diastema; in m+
and ? the posterior conule is placed so near to the postero-internal cusp
as almost to block the connection between the posterior fossa and the
-median valley, so that, in a comparatively early stage of wear, the fossa is
isolated as an enamel lake. In the lower jaw the small median incisors
are separated from each other but are in contact with the large, tusk-like
laterals, which are very strongly divergent. The canine follows the lateral
incisor without a diastema, and the first premolar is pressed against the
canine and implanted obliquely to the long axis of the jaw. Naturally,
one is tempted to regard this species merely as the male of D. smajusculus,
but the differences in the upper molars can hardly be of a sexual nature.
In the table, No. 83 is acast of the type of D. vobustus and No. 85 of
the type of D. celops.
MEASUREMENTS.
No. 83. No. 85.
Upper dentition, length . : ‘ c : : : 6 : é .148
“incisor, greater diameter : ; : 3 c F ; é -OII
a «lesser Soni j ; : : : : , : .O10
«« premolar-molar series, length . : 6 . : , : : .118
Diastema between i2 andp! . j 5 ‘ ; : : F ‘ -O19
Upper premolar series, length . d : : , : 3 : ; .0625
PL, length (¢. ¢., antero-posterior diameter) f ; : : : : .013
“ width (2. 2,. transverse diameter) j P : : ; : ‘ .O105
p2slenathiee ; p ; F i : i ; ; : : .O155
“width F : ; : ; 3 : . 5 2 ‘ : .O17
P3, length . , : ; : ‘ 3 Z : ; ; F .O17
wicca 4 : 5 7 : : : : : 5 " .0205
33 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
No 83. No 85.
P4, length . : é : : : : P : : : j 018
cla = i : : : : : : : : 5 : .023
Upper molar series, length . 3 3 6 . : 3 : ° .056
Mi, length . i : 6 9 0 : 3 j : j : .0205 .0205
“width . : : A 5 : : 0 ; 0 5 , .025 .025
M2, length . : 6 : é : : : : 5 5 : .022
sytiehin ; ; : 3 0 : 0 : ¢ : : 028
M3, length . 3 : ; : . ‘ : 5 : f ; .O17 .O18
G Tyelin : 4 , F ; : 3 : : F i .025 .024
Lower dentition, length . : ; : : : : F : : .140
“tusk, greater diameter . : ; : : ; : : : -0095
es “lesser diameter. 9 : : ; : ; : : .0075
«“ _ premolar-molar series, length ‘ 3 : : : . ; 124
«premolar series, length 3 : : , : . 9 : .063
Ps, length . : : 2 : ‘ ; : : E ‘ ; .O15
co yl ; : : ; : : : : : : : .008
Pz, length . : : 0 : : 0 5 0 : . : .O185
“width . 0 . 5 3 ; . : . : 0 3 O12
Pz, length . ; . : ; : SRS . : : : .O18
“ “width ~~ é , i i: 5 : ; 5 : ‘ ‘ .O14
Lower molar series, length . : 5 : : : : : : Koloy
M;, length . : . . 0 : 0 : : . . 5 .018
“ width . 5 ; ‘ ; ‘ 4 : ; , : : .O14
Mg, length . : E F c 9 ; ; . 5 : 0 O21
“ width . ; : . : i : ‘ : 5 : : 013
Mz, length . : . : : 2 : : . : 0 6 .020
“width . é . : : : Q : P 0 : : OIL
Localities. — Not given for type of D. vobustus or for that of D. calops.
DIADIAPHORUS VELOX Ameghino.
(Plates II, Figs. 3, 4; III, Fig. 8.)
Diadiaphorus velox Amegh.; Enum. sistematica, etc., 1887, p. 20.
Of this, the smallest known species of Diadtaphorus, 1 have seen no
upper teeth. According to Lydekker (’93, p. 60), “the upper molars are
somewhat smaller than those of D. majusculus and of much more brachyo-
dont type, the valleys being shallower and more open and the columns
lower.” Lydekker’s figures (of. czt., Pl. XXV, figs. 7, 8) show that in this
species the upper grinding teeth are broader transversely in proportion to
their antero-posterior length than in the preceding species. Further, this
author says that ‘‘the associated lower molars show a small tubercle in
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. | 39
the posterior crescent.” Such an association is almost certainly an acci-
dental one of Proterotherium or Licaphrium with D. velox.
For the mandibular dentition, I have two individuals, one the cast of
a jaw in the Ameghino collection, marked ‘‘co-type,”’ the other (No.
15,295) in the Princeton collection. Between these two specimens there
are some striking differences, principally in the form of the caniniform
incisor and in the relative size of the molars. It may well be that we
have here to do with different species, but until more complete material
has been obtained, I shall prefer to consider the differences as sexual and
to regard the Princeton mandible as belonging to a female.
In the co-type the caniniform igs is broad and thin and the canine is
placed nearly midway between ig and px, while in the supposed female
the tusk is more slender and conical and very much less compressed, and
the canine is inserted somewhat nearer to ig than to pr. The grinding
teeth resemble those of the preceding species, except for their smaller size
and slightly greater relative width. Both of the mandibles indicate ani-
mals somewhat smaller than the type of the species.
As will be noted from the table, the molars are considerably larger in
No. 15,295 than in the co-type.
MEASUREMENTS.
Co-type. No.
15,295.
Lower dentition, length . : : ; ; é : ! ‘ .096
Iz, greater diameter : E ; F , i 5 ‘ : f .007 .0055
“lesser sf : 2 ‘ F ; : : ‘ ‘ j .003 .005
Lower premolar-molar series, length : ; : 5 P : é .07 4. .079
“premolar series, length 5 ; é : : : ‘ : .039 .039
P,, length (z. ¢., antero-posterior diameter) : : . : : ; .005 .006
““ width (¢. ¢., transverse diameter) ; Z ‘ F f } j .004 .004.
Pz, length . : é : : : : : : : é ; .O10 Ko} fo)
“ width é é : : : : C P , : ; : .005 .005
Pz, length . : : : j : 6 ‘ : , j : OIL -OII
“ width : : ; : é cl : : : : : : .008 .008
Pz, length. : : : é : i ° : é ; ; OIL OI
“ width ; : : ; ; ; i : , : : 3 .O10 .O10
Lower molar series, length . F : : , ? : : : .036 -O41
M,, length . : : ‘ : ; F . ‘ : : : .O105 .O12
Sewicltie : : : 6 : 3 : ‘ : F : .009 .O10
M,, length . i B : ; : ; : : L u 3 .OIIS .O13
Sonavwicit aime : é : : : 3 b : ; F ’ .009 .O10
M,, length . ‘ : : : ; ; ‘ : f : . .O12 .O15
“width . i : ‘ : c c c C : : : .0075 .008
40 PATAGONIAN EXPEDITIONS: PALAZSONTOLOGY.
Localities. — The type-specimen was found in “the cliffs of the Santa
Cruz River”; No. 15,295 was collected by Mr. Peterson on the coast of
Patagonia, ten miles south of Coy Inlet. The field label says: ‘base of
Santa Cruz beds.”
LICAPHRIUM Ameghino.
(Plates VI; VII, Figs. 1-72.)
Licaphrium Amegh.; Enum. sistematica, etc., 1887, p. 20.
Anitsolophus Mercerat, in part; Rev. del Museo de La Plata, T. I, 1891,
p. 462. "
There may be some doubt as to the propriety of separating this genus
from Proterothertum, for, although typical specimens of the two are quite
strikingly different, transitions between them are not wanting. Yet, as
there is no certainty that these transitional forms are all strictly contem-
poraneous, it would serve no useful purpose to unite the two genera.
Licaphrium may be distinguished by the following characteristics: (1)
The animal is relatively heavier and more robust and the teeth are more
massive than in Pvoterothertum. (2) The internal ridge of p? is not
divided into cusps, while p* and p* have no tetartocone. (3) In the
upper molars the two internal cusps are less distinctly separated and in
m* they are actually connected by an enamel ridge; in m® the hinder
half of the crown is less reduced and in some of the species there is a
small, but distinct hypocone. (4) In the lower jaw, the molariform pre-
molars and the molars have shallower and less defined valleys and in the
molars the postero-internal pillar is much larger than in Proterotherium,
while the talon of mz is not so clearly separated from the posterior cres-
cent. (6) The limb bones are heavier and the feet shorter and thicker.
Dentition (Pls. VI, figs. 1a, 16, 3-5; VII, figs. 2-7a).
Upper Jaw. The incisor has the same caniniform, tusk-like shape as in
Diadiaphorus and Proterotherium. Of p* I have seen no unworn speci-
mens; when well abraded, it resembles that of Pvroferotherium, while p*
differs from the type usual in the latter genus in not having the internal
ridge divided into two cusps. The third and fourth premolars, though
nearly molariform, differ somewhat from each other; p* is smaller, has
much smaller conules, less prominent anterior and posterior cingulum,
and a minute, incipient tetartocone, which is absent in p=. Both of these
teeth are thus distinctly less advanced in differentiation than those of Pro-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 41
tevothertum. The molars are broad and heavy, with thick, massive cusps:
in m+, and especially in m2, the internal cusps are less distinctly separated
than in Proterotherzum and in m2 these cusps are connected by a low ridge
of enamel. The third molar differs from that of the last named genus in
having the hinder half of the crown less reduced and, in several of the
species, a distinct, though very minute hypocone is present: m® closely
resembles p=.
Lower Jaw. The incisors do not differ in any noteworthy manner from
those of Pvoterotherium, except that they tend to be more procumbent.
The canine is small and, in most instances, is placed in contact with the
lateral incisor, but is sometimes separated from it by a very short space.
The first premolar is usually larger than in Proferothertum and pz resem-
bles that of the latter in form, but has less prominent internal ridges; pz
is almost molariform, but the anterior crescent has a shallower valley and
is less complete than the posterior, and the antero-internal cusp is a partly
separated pillar. In pz, which is quite molariform, the antero-internal
pillar is much reduced or absent, but the postero-internal one is well-
developed, though varying in degree of separateness.
In the typical species of Lecaphrium, such as L. flower, the lower molars
differ from those of Proterotherzum in their breadth and massiveness and
in the shallowness of their valleys, especially in the anterior crescents, but
in L. froxtmum, the proportions are much more nearly as in the latter
genus. A constant difference, however, is to be noted in the much larger
size of the postero-internal pillar, which is always very conspicuous, and
the talon of mg is less distinctly separated from the posterior crescent.
Comparatively little is known of the skeleton. I have seen no complete
example of the skull (Pls. VI, fig. 1; VII, fig. 1), but, so far as it is pre-
served in the available specimens, it has great resemblance to that of Pro-
tevothertum, but is heavier and more massive and the bones composing it
are much thicker. The occiput is broader than in Deadiaphorus, nar-
rowing less dorsally. The face is short and very deep dorso-ventrally,
though this proportion varies much in the different species. The orbit
has a somewhat lower position than in the last named genus, and in front
of the orbit the dorsal part of the maxillary has a curiously inflated appear-
ance, doubtless owing to an enlargement of the antrum. This swollen
appearance is most conspicuous in old animals. The lachrymal foramen
is placed a little in front of the oribital rim, as in Dzadzaphorus , the infra-
42 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
orbital foramen is larger than in the latter and is constantly double. The
material is insufficient for fully determining the character of the nasals and
anterior nares, but it is clear that these structures are intermediate in form
between Diadiaphorus and Proterotherium. The nasals are longer than
in the former and articulate with the premaxillee, of which the depressed
and rounded sheath of the tusks are shorter, and consequently, the narial
opening is less oblique.
The mandible has a very stout horizontal ramus, which in some species
is unusually deep dorso-ventrally, increasing this diameter of the face.
I have seen no vertebre of this genus, except two thoracics belonging
to L. flowert (A. M. N. H., No. 9271), evidently the penultimate and last
of the region. These vertebree resemble the lumbars of Dzadiaphorus,
and have large, depressed centra, cylindrical, interlocking zygapophyses,
with prominent metapophyses, and low, broad neural spines. On the
penultimate vertebra the spine is erect, showing that this is the anticlinal,
while on the last it has a slight forward inclination. Both have short,
though prominent, transverse processes and even the last one articulates
with the tubercle of the rib.
Bones of the limbs and feet (Pl. VI, fig. 2), so far as they are known,
resemble those of Dzadtaphorus, but are relatively somewhat more elongate.
LICAPHRIUM FLOWERI Ameghino.
(Plates VI, Fig. 3; VII, Figs. 1-4.)
Licaphrium flowert Amegh.; Enum. sistematica, etc., 1887, p. 20.
Licaphrium intermedium Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891,
p- 297 (typographical error).
Licaphrium intermissum Amegh.; Ibid., p. 345.
Antsolophus Fischeri Mercerat; Rev. del Museo de La Plata, T. I, 1891,
p. 465 (fide Ameghino).
Licaphrium granatum Amegh.; Enum. Synopt. des Mamm. Foss. de
Patagonie, 1894, p. 41.
This is the typical and one of the largest, heaviest and most abundant
species. Most of the specimens found are of very old individuals, with
teeth so worn that almost all trace of the tooth-pattern has been obliterated.
However, one of the Ameghino series of casts, marked ‘“co-type,” shows
m* and * in a moderately abraded condition. According to this specimen,
m* has a metacone which is but little reduced in size, though quite oblique
re
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 43
to the plane of the paracone. Apparently there is no trace of the postero-
internal cusp, or hypocone, the posterior cingulum curving upward ata
right angle upon the posterior edge of the protocone, the inner side of
which is strongly convex. ;
The lower molars are very broad and heavy, with massive cusps and
Shallow valleys, especially of the anterior crescents; the postero-internal
crescent is thick and blunt, and the talon of mz large.
In the following table No. 33 is the co-type already referred to ; No. 34
is a cast of a mandible referred to this species; No. 36 is a cast of the
type of Z. granatum and No. 39 is also acast referred to the same species.
No. 9271 is the facial portion of the skull of a very old individual, in the
collection of the American Museum of Natural History; the small size of
the tusks indicates that this was probably a female.
MEASUREMENTS.
No. No. No. Vo. No. No.
33-34: 36. 39-927. 15,309.
Upper dentition, length . : : 128
«incisor, greater diameter : .008
as «lesser as : -006
«« premolar-molar series, length . O91
«« premolar series, length . : .04.7
2, length (. ¢., ant.-post. diameter) . .O12
“ width (¢. ¢., transverse diameter) . .0135
P3, length : 5 : ; ; .O13
“ width : : : : d .O16
P4, length : : ; : ‘ .O14
“ width . : : : : : .O17
Upper molar series, length : : .044.
Mi, length . : : : : O13
“width 6 : ‘ 6 : .O19
M2, length ; : : F a ONL7, .O16
“width : 4 é : O2s .022
M3, length . : ; ; . O13 .O14
“width : . . c O22 021
Lower lateral incisor, greater diameter. .007 .009
cs oa Ge lesser iy ot .005 .0055
Lower premolar-molar series, length .096 .097 .I01
«premolar series, length . 5 .048 .049 .O51
P;, length c 0 : c . .O10
“width Es F : 5 : .005
Ps, length ‘ ‘ : : c .O14 .013
44 PATAGONIAN EXPEDITIONS:
Ps, width
Pz, length
“width
P3, lerigth
«width :
Lower molar series, length
Mj, length
“width
Mg, length
“width
Mg, length
“width 6 6
Mandible, depth below mz
“ G 19 =
Pz
No.
33.
PALAZONTOLOGY.
No No. No
34 36. 39.
.006 .007
.016 .O15
.OII .OII
.O14 .O14 .O14
013 .O13 .013
.048 .O47 .050
.O14 .O145 .O15
.O12 .O14 .O14
.O15 .O15 -O165
.O13 .O14 .O14.
.O17 .O175 .O185
.O115 .O115 O13
No.
9271.
No.
15,309.
.O14
.013
O51
.O145
.O14
.O165
.O145
.020
.O125
.033
.023
It may be well to add here the measurements of the supposed L. zufer-
missum Amegh., which I believe should be referred to this species ; they
are taken from casts of the type.
Upper premolar-molar series, length
cc
premolar series, length
P4, length (¢. ¢., ant.-post. diam.) .
“width (2, ¢., transverse diameter)
P2, length
“width
P3, length
“width :
Upper molar series, length
M1, length .
“width
M2, length .
“width
M3, length .
“width
I;, greater diameter
“lesser diameter
Lower premolar-molar series, length
MEASUREMENTS.
.086 Lower premolar series, length
.050 P;, length
.O10 “ width
.007 Ps, length
-O113 “ width
.O12 Ps, length
.O125 “width
.018 Pz, length
.038 “ width 3
.O19 Lower molar series, length
.036 M,, length .
.013 «width
O21 Mg, length .
.O12 “width
.020 Mg, length .
.008 “width :
.0045 Mandible, depth below mz
092 Fa , oi Par
.048
.O10
0045,
.O12
.005
.O14
.0085
.O14
.O12
:044
.013
.O1T5
.013
.O12
.O17
.O105
.033
024
It is made plain by the measurements that this individual is somewhat
smaller than most examples of Z. flowerz, but not sufficiently so to require
its Separation as a distinct species, and the teeth are all so abraded that
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 45
no peculiarities of pattern are visible. That the animal was a female, is
perhaps indicated by the very thin lower tusk.
In L. flowert the cranium is not known. The facial region (Pl. VIII,
fig. 1) is short and of remarkable dorso-ventral depth ; taking the length
of the upper dentition as 100, this depth, measured from the alveolar
border of m# upward, is 59.3, while in Diadzaphorus majusculus this pro-
portion is only 43.6, being actually as well as relatively less in the latter.
The skull, with the mandible, must have had something of the same
square, heavy outline in side view as is found in Hyvacodon. The frontal
sinus and antrum together form a large, convex surface in front of and
above the orbit. The nasals are broad and strongly convex from side to
side; their full length is not preserved, but the portion remaining is
actually longer, and therefore proportionately much longer, than in Dza-
adiaphorus mausculus; they also differ from the latter in having an articu-
lation with the premaxillze, which appears to be relatively shorter than in
Proterothertum, and the rounded, depressed alveolar sheath of the tusk-
incisor is also shorter than in some species of the latter. As in all of the
Santa Cruz members of the family, the palatine processes of the premaxillze
are small, those of the maxillaries extending forward between the very
broad ascending rami of the former to the incisive foramina. The anterior
narial opening is high and narrow, with moderate backward inclination,
and the posterior opening is very far back, with front border between the
second molars.
All of the mandibles are unfortunately incomplete, lacking the angle,
coronoid and condyle. The horizontal ramus is notably stout, thick in
all parts and very deep dorso-ventrally in the posterior part, where the
alveolar border and tooth-row curve upward; anteriorly the ramus becomes
shallower and the symphysial region is procumbent.
Associated with this skull fragment are the two thoracic vertebrae pre-
viously described, the astragalus, calcaneum and third metatarsal. Except
for their smaller size and slightly more slender proportions, these bones
display hardly any tangible difference from those of Dzadvaphorus mazus-
culus, except that the proximal part of mt. III is distinctly more com-
pressed planto-dorsally and that the plantar surface is broader than in the
latter.
46 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
MEASUREMENTS.
Face, length orbit to premaxillary . .105 Astragalus, length of neck on fib-
“ dorso-ventral depth atm2 . .076 ular side. : : ; : .O15
Penultimate thoracic, length of cen- Calcaneum, length : : ; 081
trum . : j ‘ F : .031 ag GO itelose : .043
Penultimate thoracic, width of ante- fe width of free end . : .O16
rior face. ; ; : : .023 Kc « « distal end . .OII
Last thoracic, length of centrum . .032 Metatarsal III, length . , : .084
a s width of posterior face 025 ms “proximal width 3 .024,
Astragalus, length . 5 : : O41 Ks “ distal width . : .025
cs width of trochlea . : 023
Localities. —The type of the species was found in the cliffs of the Santa
Cruz river, but no locality is given for the types of ZL. granatum or L.
tntermissum. No. 9271 (A. M. N. H.) was collected by Mr. Brown at
Mantes Casa, 7 miles south of the Coy River; No. 15,309 by Mr. Peterson
20 miles south of Coy Inlet.
LICAPHRIUM PYRAMIDATUM Ameghino.
(Plate VI, Figs. 4, 5.)
Licaphrium pyramidatum Amegh.; Anales del Mus. Nac. de Buenos Aires,
See 8, 1, WU O, AW,
This species is known to me only from casts of the type-specimen, frag-
ments of the maxillary and mandible, each with the four last teeth in place.
In size and proportions of the teeth this species agrees closely with Z.
flowert, but there are certain differences in the pattern which justify the
separation. In m# the postero-external cusp (metacone) is more reduced
in size and the single internal cusp (protocone) is larger and has a plane
internal face, giving a characteristically pyramidal shape; the conules,
especially the posterior one, are smaller. The lower grinding teeth have
less massive cusps and more open valleys, and in m, the postero-internal
pillar and talon are more slender, giving quite a different appearance to
the tooth.
MEASUREMENTS.
P4, length (@. ¢., ant.-post. diam.) . .O145 M2, width . : : 5 3 .022
“ width (2. ¢., transverse diameter). .020 M8, length . 5 : : : .O14
Upper molar series, length . : .047 “ width . F : ‘ : .022
M1, length . i ‘ : j .O155 Pz, length . i : 5 : .O14
Se widthyaee : : : 4 .020 “ width . é 4 .O125
M2, length . : j ‘ : .O175 Lower molar series, length . : .O51
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 47
MEASUREMENTS.
M,, length . : : 3 : .O15 Mz, width . é ; ; ‘ .O13
“width . é 3 : : O12 My, length . : 6 . : .020
M,, length. F : ; : .O16 “width . : : : : .O12
Locality. — Not given.
LICAPHRIUM PROXIMUM Ameghino.
(Plate VII, Figs. 6-72.)
Licaphrium proxtimum Amegh.; Anales del Mus. Nac. de Buenos Aires,
Sem 2, 1. IMM, jo. alco.
Of this species I have seen only the casts, which I owe to the kindness
of Dr. Ameghino. ‘The type-specimen is a fragment of the right maxillary
containing m* and # and accompanying it isa separate m®* of the left side;
the second specimen is part of the right ramus mandibuli, with all the
molars and the last two premolars in place. Assuming that these are all
properly referable to the same species, the distinctness of that species is
indisputable. The third upper molar resembles that of ZL. pyramidatum
in having the protocone flattened on the inner side, but differs in the
presence of a minute, but distinct hypocone, which is but partly detached
from the prominent posterior cingulum.
The lower teeth differ from those of the other species of Lecaphrium
and resemble those of Profevotherium in their proportions, in the lack of
massiveness of the cusps and in the deep and widely open valleys. At
the same time, the propriety of referring this species to Licaphrium is
made evident by the very large size of the postero-internal pillar and by
the talon of mg. All of the teeth preserved, with the exception of mz,
have very broad posterior crescents, which bulge outward over the roots
in a very characteristic way.
MEASUREMENTS.
M1, length ( ¢., ant.-post. diam.) .O14 Pz, width : : .0095
“ width (2. ¢., transverse diameter) .O19 Lower molar series, length . : .043
M2, length . i : : : .016 M,, length . ; ‘ : : .O12
“« width . ; : c : .0205 “ width . : : : ; .O10
M3, length . : ; ; : .0135 My, length . : : : : .O14
wi thus : : : : .0215 co aymiahdn, : ; : : {OUT
Pz, length . : : 6 j .O155 Mg, length . : : : : .O165
i Tati : : ; : .009 “width . : : : : .0095
Pz, length . : c c . .013
Locality. — Not given.
48 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
LICAPHRIUM PYNEANUM sp. NOv.
(Plate VI, Figs. 1-2.)
Among the fossils collected by Mr. Hatcher at Lake Pueyrredon is the
incomplete skull and mandible of a Licaphrium, different from any that
has yet been described. Associated with the skull are the femur, tibia
and part of the pes. The remains are those of a young animal, with
almost unworn teeth ; the premolars are all in place, but the last molar,
above and below, was just in process of eruption and not yet in use.
Actually, the teeth are of nearly the same size as in L. flowerd and are
therefore considerably larger in proportion to the size of the skull. Inno
other specimen of the genus have I seen perfectly unworn examples of
p? and * and am therefore unable to make an exact comparison of these
teeth in the different species. In p* the transverse diameter is relatively
somewhat less than in L. flower? and the other preceding species: it has
a single, large, cordate external cusp and a low, ill-defined internal one ;
the inner cingulum forms two discontinuous loops, of which the anterior
curves backward to the apex of the deuterocone, while the posterior one
curves forward inside of the latter, extending beyond the end of the ante-
rior loop, but quite widely separated from it transversely.
The third upper premolar has a more nearly square crown than in Z.
fiowevt and the inward projection of the antero-internal portion is much
less prominent ; the conules are small, especially the posterior one. Ante-
riorly the cingulum is a low, broad shelf, the inner end of which curves
backward and dies away against the base of the deuterocone, while the
posterior cingulumis much more elevated and rises to join the apex of the
deuterocone. A minute, incipient tetartocone arises from this cingulum;
I am unable to say whether this minute cusp is present in other species
of the genus, but its variability is shown by the fact that, in the individual
before us, it is more distinct on the right side than on the left.
The fourth upper premolar, like p?, has a more nearly square crown
than in L. flower and, in particular, the inward production of the antero-
internal portion is less, so that the tooth has a more symmetrical outline:
the conules are larger and more conical than in p® and the posterior cin-
gulum is separated by a cleft from the deuterocone. On the right side,
there is no tetartocone, as in the other species of the genus, but on the
left side, there is an extremely feeble indication of it.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 49
The first and second upper molars have been badly broken and the prin-
cipal difference from those of the other species which may still be noted is
their relatively less transverse width. The third molar is proportionately
larger than in the other species and has a less reduced metacone, though the
external face of this cusp is very oblique; the protocone is large and ap-
pears to have a convex internal face; the hypocone, though small, is
much more distinct than in L. proxzmum, being almost separated from
the cingulum, which passes around it.
All of the lower teeth in front of pz are broken away level with the jaw;
the lateral incisor, which is very large and procumbent, would seem to
indicate that the animal was a male. The last two premolars and the
molars have broad and heavy crowns, but the cusps are less massive and
the valleys much deeper and better defined than in ZL. flowerz, but less so
than in ZL. Jroxtmum. On all of the lower molars the postero-internal
pillar is extremely large and prominent and, as in L. proxtmum, it is
largest in mz, while in Z. flower7 it is largest in mz: the talon of mz is
smaller than in either of the species named.
MEASUREMENTS.
2, length (7. ¢., ant.-post. diam.) . .013 Iz, lesser diameter : : ; .0055
‘““ width (. ¢., transverse diameter) 013 Lower premolar-molar series, length .099
P3, length . ; ; : : .O14 «« premolar series, length : .052
GS sich : : : : .O17 Pz, length . 3 : 3 é O15
P4, length . ; : : ; .O145 “ width . : j ! 3 .O10
“ width . é : : : .018 Pz, length . : 3 : . O15
Upper molar series, length . : .043 «width . ; : : : .O115
M4, length . : : : : O15 Lower molar series, length . : .O47
“width . : : ‘ ; .O19 M;, length . ; ‘ : ‘ .O145
M2, length . : : : : .O165 “width . ‘ : ; : .O12
«width . 6 : : é .020 Ms, length . : : : : .O17
M3, length . ; ‘ : : .O165 “width . ‘ F : 3 .O145
“width . ; : ; ; .O14 M;, length . ‘ F ; : .O17
Iz, greater diameter . ‘ : O11 «width . 6 6 é 5 .018
The skull (Pl. II, fig. 1) has a long cranium, with full and rounded
brain-case; the temporal ridges and sagittal crest are much as in Dzada-
phorus, but the crest is much thicker. Though the dorsal moiety of the
occiput is badly broken, it is plain that it was relatively broader than in
Diadiaphorus and even somewhat wider than in Proferotherium. Appar-
ently, the periotic is entirely excluded from the surface of the skull by the
50 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
junction of the squamosal and occipital. The basioccipital is long and
broad, with median convexity, which bears a ventral keel, and shallow
concavities on the sides. On each side of the basioccipital is a very large
vacuity, which was partly closed by the missing tympanic. The basi-
sphenoid is long, broad behind, tapering forward, so that the anterior end
is very narrow. The posterior nares extend farther forward than in Z.
flowert, to the middle of m.
One of the most striking differences of this specics from L. flowerd is
the comparative shallowness, dorso-ventrally, of the facial region, even
making all due allowance for the vertical crushing which the skull has
undergone. In fact, this proportion approximates that found in Pvofer-
othertum. The supra-orbital foramen, which is single on each side, is
very large.
The horizontal ramus of the mandible is thick and stout, but shallower
dorso-ventrally than in L. fowerz, thus making still more marked the dif-
ference between the two species in the vertical diameter of the skull.
MEASUREMENTS.
Cranium, length to anterior rim of Face, depth at m2 : : 5 ROS
orbit : : : d ‘ .126 Mandible, depth at mz . : : .029
Occiput, width at base . ; F .054 sf oy aro : : .022
The femur is very similar to that of Dzadzaphorus, the head is small,
sessile and deeply notched on the inner side by the triangular sulcus for
the round ligament. ‘The great trochanter is very prominent and, though
not rising so high above the head as in Dzadzaphorus,is broader and
more recurved on the posterior side: the other trochanters are broken
away. The shaft, which has a very decided sigmoid curvature, is much
compressed laterally, thick antero-posteriorly; the pit for the plantaris
muscle is very deep and conspicuous.
The tibia is somewhat shorter than the femur and quite stout; the
cnemial process, though very prominent and with massive proximal end,
is Shorter than in Proferotherium, dying away more abruptly upon the
shaft. Of the distal end, the width slightly exceeds the thickness; the
astragalar facets are not deeply concave, despite the prominence of the
intercondylar ridge, the dorsal tongue of which is somewhat better defined
than in Pvoterotherium. Except near the dorsal side, to which the very
low internal malleolus is confined, the astragalar facet has no raised inner
margin.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 51
The tarsus (Pl. VI, fig. 2), so far as it is preserved, does not differ in
any important manner from that of ZL. fowerz, the distal end of the cal-
caneum has a somewhat narrower and less oblique facet for the cuboid.
Metatarsal III is somewhat shorter than in Z. flowervz and relatively
rather broader and more compressed planto-dorsally, and more flattened
on the plantar side. The phalanges of this digit resemble those of Dza-
diaphorus, except that the proximal one is thicker and has on its dorsal
face a more prominent tubercle for the extensor tendon.
MEASUREMENTS.
Femur, length from head. 3 .192 Mt. III, length . : é : .082
a s “grt. trochanter. 205 « «distal width. : ; .025
“proximal width é ° .058 Digit II], phalanx 1,length . 6 .044
«distal width =. : : .048 anes «I, proximal width .0285
Tibia, length (exclusive of spine) . 175 Se «1, distal width . .020
«distal width : é : .031 se BS Go a \enein : .018
“s “thickness . : : .027 Serre «2, proximal width .024.
Astragalus, length : 5 é .0385 aes «2, distal width . O21
i width of trochlea : .02T
Locality. —The type-specimen was collected by Mr. Hatcher on the
west shore of Lake Pueyrredon.
This species is named in honor of M. Taylor Pyne, Esq., Litt.D., to
whose liberality the Patagonian Expeditions are much indebted.
LICAPHRIUM PARVULUM Ameghino.
(Plate VII, Fig. 5.)
Licaphrium parvulum Amegh.; Enum. sistematica, etc., 1887, p. 20.
Licaphrium arenarum Mercerat ; Rev. del Museo de La Plata, T. II, 1891,
p- 460 (fide Ameghino).
The type of this species is a single tooth (mz), measuring 15 X 8 mm.,
which is distinguished by its small size and by the prominence of its talon.
A cast of another specimen, a fragment of the maxillary with the three
molars, kindly sent me by Dr. Ameghino, shows that m+ is of the type of
L. pyvamidatum, on a smaller scale, the posterior cingulum curving up to
join the apex of the single, large internal cusp. The mandibular teeth
which accompany this second specimen are, without doubt, referable to
Proterothertum. The cast has the following dimensions.
52 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
MEASUREMENTS.
Upper molar series, length . : .038 M2, width . ‘ : : d .O19
M4, length (., ¢., ant.-post. diam.) . O13 M3, length . F : j ; O13
“‘ width (@. ¢., transverse diameter) .018 “ width . 5 5 : : .020
M2, length . : : F : O14
SHSCWES UNCHRITAD Ss DUS)
The two following species, which have been referred to Lecaphrium, are
not sufficiently well known to make clear their generic reference.
LICAPHRIUM DEBILE Ameghino.
Licaphrium debile Amegh.; Enum. Synopt. des Mamm. Foss. de Patagonie,
1894, p. 42.
LICAPHRIUM TENUZ Ameghino.
Licaphrium tenue Amegh.; Ibid., p. 43.
This is the smallest known Santa Cruz representative of the family, but,
further than to say that it is not a species of Thoatherium, it is not possi-
ble to go with the existing material.
LICAPHROPS Ameghino.
Licaphrops Amegh.; An. del Mus. Nac. de Buenos Aires, Ser. 3, T.
III, p. 448.
I have seen no example of this genus, which is characterized by the
great development of the antero-internal cusp (protocone) of the upper
molars and the great reduction of the postero-internal cusp (hypocone),
giving the crown a somewhat triangular shape.
LICAPHROPS COALESCENS Ameghino.
Licaphrops coalescens Ameghino ; Loc. cit., p. 455.
This, the only known species from the Santa Cruz beds, is represented
by a single upper molar, which measures 15 mm. in antero-posterior by
13 mm. in transverse diameter.
PROTEROTHERIUM Ameghino.
(Plates VII, Figs. 8-11; VIII-X; XI, Figs. 1-11; XII, Figs. 1, 2; XIII, Fig. 8.)
Proterotherium Amegh.; Bol. de la Acad. Nac. de Cienc. de Cordoba, T.
V, 1883, p. 291.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 53
Anoplotherium Bravard (non Cuvier); Monogr. de los terren. e€oc., etc.,
1858.
Anchitherium Burmeister (wow v. Meyer); Descr. phys. de la Repub.
Asgents nie Mei S7oy ps 70:
Anisolophus Burm.; Anales del Mus. Nac. de Buenos Aires, T. III, 1885,
Pant 72:
Diadiaphorus Mercerat, in part; Rev. del Mus. de La Plata, T. I, 1891,
Pp. 458.
Oreomeryx Mercerat, in part; Ibid., p. 465.
Anomodontherium Mercerat ; Ibid., p. 461.
Thoatherium Mercerat (von Amegh.); Ibid., p. 455.
Diaphragmodon Mercerat; Ibid., T. III, 1893.
Diadiaphorus Lydekker, in part; Anales del Mus. de La Plata, T. III,
1893.
Tichodon Amegh.; Enum, Synopt. de Mamm. Foss. de Patagonie, 1894,
Pe Arse
Flepiaconus Amegh.; Ibid., p. 44.
Though closely allied to Dzadiaphorus, this genus comprises smaller
and more slenderly built animals and differs in many details of dental and
Skeletal structure from that genus. As the more salient characteristics
may be noted the following features. (1) In most of the species the second
upper premolar has the inner ridge divided into cusps, while p* and p*
have a small, though distinct postero-internal cusp (tetartocone). (2) The
upper molars have the internal cusps well separated, but in m* the hypo-
cone is usually absent or indistinguishably fused with the posterior cingu-
lum. (3) The last lower molar hasasmall talon anda very small postero-
internal pillar, which is still smaller in m,; and m;. (4) The nasal bones
are much longer than in Deadtaphorus. (5) The limbs and feet are much
more slender and elongate than in the latter.
Dentition (Pls. VII, figs. 10, 11; VIII, figs. 2-8; IX, figs. 1-10; X,
figs, 1-5, 7-15).
A. Upper Jaw. The single incisor is a caniniform tusk, resembling that
of Diadiaphorus and Licaphrium in form, but varying considerably in
size in the different species and almost certainly also in the two sexes.
A long diastema separates the incisor from the first premolar, which is
small and two-rooted, with compressed conical crown, and internal ridge
even less developed than in Diadtaphorus. The second premolar has
54 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
three roots; the crown has a single external, cordiform lobe and an in-
ternal ridge, which in most of the species is distinctly though imperfectly
divided into anterior and posterior cusps (deutero- and tetartocone),
while in Lecaphrium this ridge is not so divided. The third and fourth
premolars are nearly molariform and of a pattern which closely resembles
those of Diadtaphorus, but the two inner cusps are even less distinctly
separated. In certain individuals the posterior conule is absent in p3,
while in others it is well defined; in p* this conule is of variable size,
sometimes differing notably on the two sides of the same individual.
The difference of these premolars from those of Lzcaphrium is quite
decided and represents a more advanced stage of development.
The upper molars also are very like those of Diadzaphorus, but with
internal cingulum less prominent, or absent, while externally the cingulum
is better defined and is continued down upon the anterior border, making
a more distinct anterior style. The innercusps are well separated, almost
as deeply as in the last named genus. The third molar is the smallest
of the series and its posterior half is much reduced, having no distinct
postero-internal cusp, merely a prominent posterior cingulum. Between
the inner cusps of one or more of the molars sometimes appears a pointed
cingular tubercle, which is absent in most species, in others minute and
variable, while in only one species (P. acre) does it become at all con-
spicuous. Ameghino has referred this species to a distinct genus, Hepfa-
conus, but I think this is attributing too much importance to such a char-
acter. The molars are not so broad and heavy as in Lacaphrium and the
internal cusps are more separate.
B. Lower Jaw. The median incisor, presumably iz, has a small,
chisel-shaped, antero-posteriorly compressed crown, with transverse cutting
edge; the lateral incisor, probably is, is very much larger and caniniform
and is broad antero-posteriorly, very thin transversely, which is its prin-
cipal difference from the corresponding tooth of Diadzaphorus. The tusk
is less procumbent than in Lzcafhrium. The canine follows the lateral
incisor after a very short diastema and is separated from pz by a some-
what longer one; it is very small and has a compressed, bluntly conical
crown.
The first premolar is relatively a little smaller than in Lecaphriwm and
resembles that of Déadiaphorus, but is more compressed laterally; pz is
also much as in the latter, but is somewhat higher and more pointed and
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 55
has the antero-internal ridge rather better defined. The third premolar
is nearly molariform, with the difference that near the inner end of the
anterior crescent is a well defined vertical ridge, which is more prominent
than in Diadiaphorus and differs from that of Lzcaphrium in being a ridge
instead of a pillar. A remnant of the same structure appears in pz, but
the ridge is much smaller and is separated from the antero-internal border
only by a narrow groove. In perfectly unworn examples of pz a minute
internal cusp may be present at the hinder end of the posterior crescent,
a feature which is quite constant and better developed in Licaphrium.
The fourth premolar is more completely molariform and, as already men-
tioned, the antero-internal ridge is reduced to a mere vestige. The cingu-
lum varies in development on the premolars, but is never very prominent.
The molars are composed of two crescents, with the valleys opening
inwardly: on the inner side of the posterior end of the second crescent
is a small pillar, which is smallest in m, and largest in mz; in mj, this
pillar is visible only in unworn teeth, as it is rapidly removed by abrasion:
mz has in addition a small, but well defined talon. On the molars the
development of the cingulum varies much, even on the opposite sides of
the same jaw. Compared with those of Lzcaphrium, the lower molars of
Proterothertum differ in being narrower and less massive, and in having
better defined valleys and much smaller postero-internal pillar.
Milk Dentition. —\ have seen no examples of the anterior upper tem-
porary teeth and only much worn specimens of the deciduous premolars.
Doubtless, however, the relationships are essentially the same as in 7/oa-
thertum, which is described in a subsequent section. Both dp# and <, of
which the latter is much the larger, appear to be molariform in pattern.
All the mandibular milk-teeth are well displayed in the collection (Pl. X,
figs. 15, 15@) and all of the antemolars have predecessors in the milk-series,
but there are some interesting differences of form between the temporary
teeth and their permanent successors. The median incisor (di,) is larger,
more procumbent, more pointed and less chisel-shaped than 1,, while
the lateral, diz, is very much smaller than iz and hardly larger than the
median, so that the milk-incisors of Proferotherium might easily be mistaken
for the permanent ones of 7oathertum. The temporary canine differs
from the permanent one merely in being somewhat larger. The first milk-
premolar is far larger than p; and is implanted by two well separated
roots; dp; resembles pz in form, but is longer and thicker and the ridges
56 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
and valleys of the inner side are better developed. The third milk-pre-
molar is the largest tooth of the temporary series, which is chiefly due to
the enlargement of the anterior crescent; the antero-internal ridge is
smaller than in pz, but the postero-internal pillar is much more distinct.
The fourth temporary premolar is like pz, except in being somewhat larger
and more completely molariform, as the antero-internal cusp is absent
and the posterior pillar larger.
Skull (Pls. VIII, figs. 1, 1a, 4; IX, figs. 11, 11a). — The skull is very
like that of Dradiaphorus and Licaphrium, but has a lighter and more
graceful appearance, and there are many differences of detail. The
cranium is somewhat longer than in Deadvaphorus and the face corre-
spondingly shorter, but narrows forward more gradually. The orbit is
slightly lower in position and presentsrather more directly outward. The
occiput is relatively broader and the foramen magnum lower and wider,
while the fossa between the exoccipital and the squamosal is narrower, so
that the periotic is nearly, and in some cases quite, excluded from the
surface of the skull.
The parietal zone is somewhat longer and forms aslightly less full and
capacious brain-case, but extends a little farther down upon the side of
the cranium, narrowing the squamosals in a corresponding degree. The
zygomatic process is relatively broader dorso-ventrally and has a more
arched and elevated dorsal border, making a deeper groove between the
process and the side of the cranium ; the glenoid cavity is similar in form,
but has a deeper posterior concavity, and the postglenoid process is nar-
rowerand lessmassive. Anteriorly, the zygomatic process extends farther
into the more deeply notched jugal. The orbit is closed behind, as in
Diadiaphorus, but the posterior boundary, made up of the united frontal
and jugal processes, is more slender and less twisted: the lachrymal
foramen is larger and more conspicuous and has amore posterior position,
being placed on the rim of the orbit. The frontals are somewhat more
convex, which is probably due to a larger development of the sinuses.
The most marked difference from the skull of Dzadzaphorus is to be
found in the nasals and premaxillaries. The nasals are much longer and
narrower and taper more gradually to the anterior point ; each is convex
transversely, so that there is a well marked depression along the median
line of suture between them: they have quite extensive sutures with the
premaxillaries, while in Dzadzaphorus there is no such contact.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 57
In Proterothertum the premaxillz differ from those of Diadzaphorus in
the much smaller part which is broad and thick, with rounded and de-
pressed dorsal surface, and in the far broader ascending ramus, which has
a thinner and much more nearly vertical anterior border; the incisive
foramina are relatively larger, but are entirely confined to the premaxillz.
Owing to the differences of form of the nasals and premaxillaries, the
anterior nares have quite a different shape in the two genera. The max-
illaries are very similar in both, but in Pvoferotherium the infraorbital
foramen is proportionally much larger, though still very small, single and
placed nearer to the orbit. The palatines are very long, extending for-
ward to m+ or p=, and the hard palate is narrow and concave, while the
posterior nares are not produced so far forward as in Duadzaphorus.
The mandible differs but little from that of the last named genus ; the
symphysis is broader and more depressed, less concave on the dorsal side
and more procumbent, the ventral border rising very gradually to the
incisive alveolus. The coronoid, which is high and narrow, has a greater
inclination forward, especially in young animals, and the condyle is nar-
rower antero-posteriorly, more convex transversely.
Skeleton. — Except for smaller size and more slender proportions, all
the bones of the skeleton closely resemble those of Diadiaphorus. Very
few vertebrae have as yet been found in association with any of the speci-
mens. The atlas has a low, but distinct neural spine, and a well defined
hypapophysis, which projects backward from the hinder border of the
inferior arch: the atlanteo-diapophysial notch is in process of conversion
into a foramen, as is indicated by a short, pointed process arising from
the anterior border of the notch; the depression for the odontoid process
of the axis is narrow and deeply concave.
The lumbar vertebrze, so far as they are known, resemble those of Dza-
diaphorus in structure, though the metapophyses are relatively more
prominent. On the last lumbar the transverse processes are extremely
broad and articulate with those of the first sacral by deep concavities, as
appears to be the case in all of the Litopterna. The number of sacral
vertebree is not definitely known, but probably exceeded six. The first
vertebra (PI. XII, fig. 2) is very broad, but behind this the sacrum rapidly
contracts, becoming very narrow and very shallow dorso-ventrally, which
indicates that the tail was short: the coalesced neural spines form a low
ridge, with a somewhat higher ridge on each side of it, apparently due to
the fused metapophyses.
53 PATAGONIAN EXPEDITIONS: PALA®ONTOLOGY.
The scapula (Pl. XI, fig. 1) is short and quite broad and the spine is so
placed that the prescapular fossa is considerably larger than the post-
scapular, and the whole blade is relatively shorter, broader and more
rounded than in Dzadiaphorus. The neck is broad and there is no
distinct coraco-scapular notch; the glenoid cavity is of a somewhat pecu-
liar shape, contracting to a point anteriorly; the coracoid is not known,
but appears to have been small. The coracoid border curves forward
strongly in ascending from the neck to the widest part of the blade, which
is about the middle of the proximo-distal height, thence curving backward
and upward to the suprascapular border: the glenoid border is straight.
The spine rises steeply and is somewhat recurved, with convex anterior
face, ending distally in a short acromion: the single metacromion is a
prominent triangular process, placed just above the acromion, and appears
to have been distinctly larger and more prominent than in Diadzaphorus.
This scapula differs very strikingly from that of 7/eosodon (q. v.).
The humerus (Pl. XI, fig. 2) is almost exactly like that of Dzadiaphorus
on a smaller scale: it is short and rather slender, the deltoid ridge is
obscurely marked and the distal trochlea is of a simple, pulley-like shape.
Although the ulna and radius are not fused at any point, they are in
contact with each other for nearly their entire length, so that there is
hardly any radio-cubital arcade. The radius (Pl. XI, figs. 2, 10) is short,
somewhat shorter than the humerus; the shaft is slender, of oval cross-
section, but somewhat irregular in shape. The ulna (Pl. XI, fig. 3) is
hardly reduced at all and is nearly as thick as the radius; its distal end is
compressed and plate-like and, in addition to the surfaces for the pyramidal
and pisiform, has a small, though distinct facet for the lunar.
The carpus (Pl. XI, figs. 9, 9a) closely resembles that of Dzadzaphorus
in the shape and mutual connections of its various elements, but there are
many minor differences. Thescaphoid is higher proximo-distally in pro-
portion to its width; the dorsal convexity of the radial facet~is more
sharply defined and the trapezoid facet incises the bone more deeply; the
facet for the trapezium is relatively very large. The lunar is proportion-
ately higher and narrower; its proximal surface is similarly oblique,
descending steeply toward the radial side, and the facet for the ulna,
though very small, is much more distinct, while the knob-like protuber-
ance from the palmar face is smaller. Except for its smaller size, the
pyramidal is almost exactly as in Diadzaphorus, but the facet for the ulna
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 59
is rather more convex and that for the pisiform makes a more open angle
with it. The trapezium is an irregular, nodular bone; it articulates prox-
imally with the scaphoid by a large, slightly convex surface, laterally with
the trapezoid and has an extensive oblique facet for the second metacarpal ;
the distal end is not bluntly pointed and rugose, as it is in 7/eosodon
and the Perissodactyla, but transversely truncated and smooth, as though
for the attachment of a vestigial first metacarpal, such as Ameghino has
described in Diadiaphorus ('946, p. 268). The trapezoid resembles that
of the latter genus, except in being relatively narrower, as is also the
magnum, of which the width but slightly exceeds the proximo-distal
height, and the facet for the lunar is slightly more raised and convex in
the dorso-palmar direction, while that for the scaphoid is more concave
transversely. I have seen no example of the unciform.
The metacarpus (PI. XI, figs. 4, 9, 9a), like the other bones of the extrem-
ities, much resembles that of Déadzaphorus, but is rather more slender.
Metacarpal II is longer in proportion to III than in the last named genus,
but is of similar shape and has similar connections with the carpus.
Metacarpal III is somewhat more slender than in Dzadtaphorus, (though
the difference is not so great as it appears at first sight, because of the
smaller size of Proterotherium) and broadens less to the distal end: the
tuberosity near the proximal end for the attachment of the extensor tendon
is less prominent and the distal carina is rather sharper. Metacarpal IV,
like II, is relatively longer than in Dzadzaphorus, but otherwise similar.
I have seen no example of the vestigial mc. V, but its presence is demon-
strated by a minute facet on the head of me. IV.
The phalanges of the median digit (Pl. XI, figs. 9, 9a) are very like
those of Diadtaphorus and the proximal phalanx has almost the same pro-
portions as in that genus; the second is of more uniform width, contract-
ing less toward the distal end, while the ungual is a little more depressed,
with less convex dorsal surface. Obviously, there is some mistake in
Ameghino’s figure of P. zutermixtum {sic| (’946, p. 269, fig. 10) which is
apparently due to the association of phalanges of 7hoatherium with the
metacarpals of Proterotherium.
The pelvis (Pl. XII, fig. 2) has considerable resemblance to that of the
equine genus Mesohifpus from the Oligocene of North America. The
ilium is short and has a short peduncle, which rapidly expands into the
very broad anterior plate; this plate is obscurely divided by a shallow
60 PATAGONIAN EXPEDITIONS: PALAZZONTOLOGY.
emargination of the crista into a shorter and narrower internal portion,
which curves dorsally above the sacrum, and a very long and pointed ex-
ternal portion; the acetabulum is large and prominently projecting. The
ischium is short and laterally compressed, but quite stout. The pubis is
short and depressed and the obturator foramen is large and of longitu-
dinally oval shape.
The femur (PI. XI, fig. 5) hasa more equine appearance than any other
long bone of the skeleton, though it differs from that of Dzadzaphorus
merely in being more slender, in the narrower and deeper rotular groove
and in the more prominent backward projection of the condyles.
The patella (Pl. XI, figs. 6, 6) is a short and broad, shield-shaped bone,
which narrows distally to a bluntly rounded point. It differs from that of
Diadiaphorus in being much less massive and thick antero-posteriorly.
The tibia (Pl. XI, fig. 7) is heavy and considerably shorter than the
femur: the spine is low and bifid, with its two parts quite widely sepa-
rated ; the cnemial crest is prominent, but short, speedily dying away upon
the shaft, and the sulcus for the tendon of the extensor longus digitorum
is very deep and conspicuous. The distal moiety of the shaft is of more
trihedral, less oval, section than in Deadtaphorus and the astragalar facets
are deeper, while the anterior intercondylar tongue is more prominent.
The fibula (Pl. XI, fig. 7) has a much reduced and irregular shaft, with
ends which are laterally compressed, but expanded antero-posteriorly.
The two leg-bones are in contact only at the proximal and distal ends, but
the space between them is very narrow throughout. |
Like all other parts of the skeleton, the pes (Pls. XI, fig. 4; XII, fig. 1)
closely resembles that of Dzadzaphorus, with many differences of detail.
The astragalus has a trochlea which is slightly narrower in proportion to
the length of the bone, and somewhat more deeply and sharply grooved:
the neck is relatively longerand is less obliquely directed toward the tibial
side: on the plantar surface the facet for the sustentaculum of the cal-
caneum is not continued so far proximally and narrows less in the same
direction, being of almost uniform width, except near the distal end, where
it suddenly widens, making the external border of the facet much more
concave than in Dzadtaphorus; this facet is separated from the ectal cal-
caneal facet by a narrower and shallower sulcus than in the latter.
The proportions of the calcaneum are quite as in Diadzaphorus,; the
sustentaculum arises nearer to the plantar border, is not so heavy and has
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 61
a more rounded, less angular outline: the facet for the astragalus is nar-
rower and somewhat less concave and is bounded externally by a larger
and deeper sulcus, while the cuboid facet is somewhat less oblique and
concave. The articular surface for the fibula is small and irregular in
shape. The navicular resembles that of Diadiaphorus, except that the
proximal surface contracts less on the plantar side. The entocuneiform is
very large , but compressed and scale-like, attached to the navicular later-
ally rather than proximally and articulating extensively with the second
metatarsal. The mesocuneiform is very small in all three dimensions,
being much more reduced, especially in proximo-distal length, than in
Diadiaphorus. The large and heavy ectocuneiform has nearly the same
proportions as in the latter, except that the facet for mt. III narrows less
abruptly toward the plantar side.
The metatarsus shows some noteworthy differences, though of a very
minor character, from that of Dzadzaphorus. Owing to the reduction of
the mesocuneiform, the second metatarsal rises higher above the head of
mt. III than in the latter and has a much more extensive lateral contact
with the ectocuneiform and also extends farther distally, so that, as a
whole, it is considerably longer than in the genus last named. Metatar-
sal III is somewhat longer and considerably stouter than metacarpal III,
thus reversing the relative lengths which occasionally are found in Deadza-
phorus and the difference in breadth is also greater than in that genus.
I have seen no complete specimens of mt. IV, the proximal end being
absent; distally it extends to the same level as mt. II.
The proximal phalanx of the median digit is of the same length as that
in the manus, or, it may be a little shorter, somewhat thicker and less
depressed planto-dorsally. The second phalanx is likewise thicker and a
little longer than in the manus. Of the ungual I have seen no example.
Species. —Of all the Santa Cruz genera of this family, Proterotherium
is the most varied and abundant, and was evidently in a state of vigorous
development. This renders the discrimination of species exceedingly
difficult, and for no other genus of the Litopterna does the absence of any
minutely exact stratigraphical knowledge of the Santa Cruz beds have a
more unfortunate effect in confusing the taxonomy. Most of the species
are very variable and it is rare to find two individuals that seem to be
specifically identical. There is no ground for surprise, therefore, to find
that among the casts of the Ameghino collection there is frequently as
62 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
great a difference between two specimens referred to the same species as
between two nominal species. Unless one is prepared to form a different
species for almost every individual, it is impossible to do more than to
make a tentative and more or less arbitrary arrangement.
It cannot be supposed that eighteen or twenty species of asingle mam-
malian genus should have co-existed at the same time and place; the diffi-
culty lies in determining how many of these forms were actually contem-
poraneous, or, in other words, to distinguish between variants and
mutants. Probably, the number of species to be recognized will be
materially reduced as the result of future investigations, for several of those
already proposed have been founded upon insufficient material and almost
all upon variations of the teeth only.
It is significant of the rapid modification which Proterothertum was
undergoing in Santa Cruz times, that the variations appear to be largely
hap-hazard and that the species, or varieties, do not obviously fall into
groups, or subgenera, each group distinguished by some relatively impor-
tant characteristic. With great constancy in general plan, almost every
element of the tooth-pattern is subject to many minor variations, and
these variations do not occur together in a definite manner, but in all sorts
of combinations. It is as though some substantial improvement were
being sought by the method of ‘‘trial and error.”
In a recent paper on the black bear of Labrador, Dr. J. A. Allen has
described a somewhat similar case among existing mammals. “ Individ-
ual variation is especially manifest in the size and form of M*, which varies
greatly in skulls otherwise similar in general size and form. This tooth
varies in length, in specimens that seem unquestionably of the same sex,
from 22 to 27 mm., or about 20 per cent. of the mean. While these
variations are evident from the table of measurements, they are far more
impressive when the actual teeth are compared, since the shape of the
tooth varies as much as the size, especially in the development of the
‘keel’ portion. This is usually about one-third the length of the tooth,
but may be only one-fourth as long. The relation of width to length is
also markedly variable” (Allen, ’10, pp. 3-5).
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 63
PROTEROTHERIUM AUSTRALE (Burmeister).
(Plates IX, Figs. 7, 8; X, Figs. 2, 3, 14.)
Anchithertum australe Burmeister; Descr. phys. de la Répub. Argent., T.
TE 1870; ps 4779:
Anisolophus australis Burmeister; Anales del Mus. Nac. de Buenos
AMES, 10, JONG ISIS o, ae.
Proterothertum australe Amegh.; Enum. sistem., etc., 1887, p. 19.
Diadiaphorus australis Mercerat; Rev. del Mus. de La Plata, T. I, 1891,
P. 459.
Antsolophus Burmetstert Mercerat; Ibid., p. 464 (fide Ameghino).
Proterothertum cingulatum Amegh.; Rev. Argent. de Hist. Nat., T. I,
1891, p. 296.
Proterotherium angulatum Amegh.; Ibid., p. 345 (typographical error).
Proterotherium curtidens Amegh.; Ibid., p. 296.
Proterotherium mixtum Amegh.; Enum. SAMO, GUE., USO, JD, SO)
This species is apparently not represented in the Princeton or New York
collections save by one imperfect skull in the former (No. 15,368), and the
present account is chiefly derived from the descriptions and figures of
Burmeister and Ameghino and from the casts sent me by the latter. The
type specimen is a fragment of the upper jaw, with six of the grinding teeth
(p2—m®) in place, but these teeth are broken and lack the outer wall; they
show, however, the essential features of the pattern. I am inclined to refer
to the present species such representatives of the genus as are of moderately
large size and have the postero-internal cusp (tetartocone) well developed
in p* and +, while in m® the postero-external cusp is considerably nar-
rower than the antero-external and the postero-internal (hypocone) is
wanting. The presence or absence of a cingulum, which Ameghino em-
ploys in the discrimination of species, is a very untrustworthy criterion
and, I believe, is quite without value in this group.
The definition of P. australe given above is necessarily quite elastic and
permits the inclusion in the species of a considerable range of variation
both in size and in the minor details of the molar-pattern, but no greater
in either respect than Allen has shown to exist in the recent Ursus amer-
canus (loc. cit.).
In the following table of measurements No. 6 is a cast of the type speci-
men of P. mextum, No. 21 of P. curtidens, and No. 5 of the co-type of
64 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
P. cingulatum. In all of these cases the reference to P. australe is more
or less uncertain, but the available evidence is, in my judgment, insufficient
for any separation.
MEASUREMENTS.
No.
No. 6. No. 21. No. 5. 15,368.
Upper dentition, length i2—m3 : 109 III
«« premolar-molar series, length . .080 .072 .O81
«premolar series, length , .044 .038 .044
Pi, length (. é., antero-posterior diameter) .O10 - .0085 .0095
“ width (@ ¢., greatest transverse diameter) .009 .008 .0075
P2, length .O105 .009 .O10
“width .O12 -OII .O1I5
P3, length -O105 -0095 -O1I5
“width .O145 .O12 .O14
P4, length .O13 OL .O12
“width : .O165 .O14 .0165
Upper molar series, length .038 .034 .038
M4, length .O13 .O10 .O12
“width .O18 .O17 .O17
M2, length .O14 .O12 .0135
“width .020 .O17 0185
M3, length .0125 .O105 .O125
“width j ‘ .018 .0165 .018
Lower dentition, lengthi,—-m, . .102 .104
““ premolar-molar series, length . 083 .086
«« premolar series, length .044 .044.
Pz, length .008 0085
“ width .004, .004.
P5, length .O10 OII
“width .000 .007
Pz, length .O12 O13
“width .008 0095
Pz, length .013 .O13 .O12
“width : ; : .O10 -O103 -OII
Lower molar series, length .O41 .040 .042
M,, length .O12 .O1I5 .O12
«width .O10 .O10 .O105
Ms, length O13 .013 .013
“width .O1L -O10 -OII
Mg, length .O15 .O145 .O16
“width .OIL .0095 .O10
N. B. The discrepancies in the totals are due to overlapping of the teeth.
It will be observed that there is a remarkable difference of size between
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 65
the upper and lower teeth of P. curtidens and, though both casts are
marked “type,” there is probably some mistake involved, for the two can-
not be of the same individual, and in the original description of the species
only the mandibular dentition is mentioned (’91, 296).
Localities. —The type of P. australe was found on the banks of the Rio
Chico, for the other supposed species localities have not been given. No.
15,308 was collected by Mr. Hatcher at Killik Aike.
PROTEROTHERIUM PRINCIPALE Ameghino.
(Plates X, Figs. 4, 5, 8, 11; XII, Figs. 1, 1a.)
Diadiaphorus velox Lydekker (won Amegh.); Anales del Mus. de La
Pilate, I, Wl, WeteR, (0, Oo,
Proterotherium principale Amegh.; Enum. Synopt., etc., 1894, p. 37.
Proterotherium divortium Amegh.; Ibid., p. 38.
Proterotherium dichotomum Amegh.; Anales del Mus. Nac. de Buenos
Aves, Sem BI. ION jo. Wee.
Though nearly allied to P. australe, this appears to bea distinct species,
being not only larger than the latter, but also having certain peculiarities
of tooth pattern which appear to be of specific importance. P2 has no
posterior conule and the postero-internal cusp (tetartocone) is very small
and imperfectly separated from the antero-internal (deuterocone), while in
p* this element is somewhat larger and more distinct, though decidedly
less so than in P. australe. The third upper molar has no hypocone, or
a very minute one, and the posterior ridge, formed by the cingulum, is
unusually low; the protocone is very large, of pyramidal shape, and ex-
tends across nearly the entire internal face of the crown.
In the mandible, the diastemata between the lateral incisor and the
canine and between the latter and the first premolar are very short.
P. divortium (Pl. X, figs. 4, 5), which was established upon portions of
the upper and lower jaws, appears to be only an individual of the present
species with slightly more slender mandible than is common. Of P.
adichotomum (PI. X, fig. 8), the type is an isolated upper molar (m*) which
agrees quite closely in size and pattern with the corresponding tooth of
P. principale.
In the subjoined table of measurements, No. 16 is a cast of the type;
No. 14 is a cast of a second and considerably older individual, an incom-
66 PATAGONIAN EXPEDITIONS:
PALZ/ONTOLOGY.
plete mandible associated with an isolated m%; No. 13 (Pl. X, fig. 11),
a cast of a fragment of the mandible, also marked ‘‘type,” but evidently
belonging to a much older animal.
divortium and No. 27 a cast of the type of P. azchotomum.
is a young animal with mz and z not yet fully protruded.
Upper dentition,
length i2 —m3
Upper premolar-
molar series,
length
Upper premolar
series, length .
P1 length (2. ¢., ant.-
post. diam.)
Pl, width ( ¢.,
greatest transv.
diam.)
P2, length
“width
P3, length
“width
P4, length
“ width
Upper molar,
series, length
M4, length
“width
M2, length
“width
M3, length
“width
Lower dentition,
length iz —myz
Lower premolar-
molar series,
length
Lower premolar
series, length
P;, length
“width
.087
.0465
.0095
.0095
.O10
.O12
.O13
.O16
.0135
.O18
.042
.O15
.O185
.O17
.O21
.O14
.020
MEASUREMENTS.
.O13
.O18
.O41
.O13
.O18
.O15 .O155
.O195 ‘ .020
.0135 O14
0195 .020
.009
.004
No. 17 is a cast of the type of P.
No. 15,436
No. Vo.
15,732. 15,430.
-112
.089
.046
.008 5
.004.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 67
No. No. No. No. Vo. No. Vo.
16. I7. T4. 73. By. LEGGE, HE ABO
Ps, length . : .O12 O12 OIL O11
“ width P : .006 .0065 .006 .005
Ps, length . ; .O14 .0135 .O14 .0135 -0135
So vicl: ae ; .009 .O105 -O105 .009 .009
Pz, length . : .OI4 013 .013 .O14.
«width . ; .O125 .O12 .O11 OIL
Lower molar series,
length : ; 045 .043 .044.
M;, length . A .013 .O125 .013
“width . : .O12 .OII -OII
My, length . : .O145 .O15 O14
“width . : .O12 .O12
Ms, length . ‘ .O17 .O16 .O17
CG syatcliin ‘ OIL .O1L
Mandible, depth
below pz . : .0215 .023 .0215 .023
Associated with the mandible, No. 15,436, is the somewhat incomplete
hind-foot shown in Pl. XII, fig. 1. It is remarkable for the relative short-
ness and heaviness of most of its elements and, had it been found alone,
would probably have been regarded as belonging to some species of
Licaphrium. With this specimen may be compared another, No. 15,712,
which, unfortunately, was not found in association with teeth, and there-
fore cannot be definitely referred to any species. The radius of this second
individual, shown in Pl. XII, fig. 10, agrees in the dimensions of the distal
end with those of P. cavum (see p. 76) but the hind-foot is apparently too
large for reference to that species.
MEASUREMENTS.
No. Vo
KARO, WEA.
Calcaneum, length . : ; ; : j ; ; : : , .0645 .069
“ width over sustentaculum . ; ; : : : : .024 .023
ss « atend of tuber . ‘ ; j : : ; : .O16 .O15
st « “ middle of tuber 6 é : j 5 6 . .009 .008
Astragalus, length . ; : : : : : ; : 0 4 .032
¢ width of trochlea . F 6 c : c . d : .O17
ss « «distal end : : 6 ; ; : : b -O165
Tarsus, length in median line . : : ; : F : j ; .042
«width : ; : : : 6 : : : c 0 .028
Ectocuneiform, length . ; ; : : . : : : i .008
a width . 4 ; : ‘ : 3 : § ‘ .O16
68 PATAGONIAN EXPEDITIONS: PALAZSONTOLOGY.
Vo. No.
15,430. 15,712.
Metatarsal II, length . : : ; é 6 : i é : 061 .059
st “proximal width : : : : : : ; : .004. 004.
os ay as thickness . : : : 4 2 ‘ ‘ .O10 .0095
“ “distal width . : ‘ 3 5 Z : : : .006 .006
cs “thickness : ; é : : 5 6 6 .O105 .O105
Metatarsal III, length . : : : é j 6 . : : .075
“proximal width 6 é : é 6 : 0 E .O19
cz ee a thickness over hook . : : : : : .O21
ee “distal width . ; 6 b ; : : . : .020
Phalanx 1, digit III, length. : ; ; f P : ‘ i .037 .037
a 1, “ ‘ proximal width : 5 0 : . 0 : .020 .020
“ Ts Lech ns BCS ss thickness . j j ‘ : : : .OI2 .O12
Phalanx 2, digit III, length . j 6 : 5 ; : : ° .021
a 2, “ proximal width : : 5 : : : 0 .O165
Localities. — Ameghino gives no localities for P. principale or P. divor-
tium,; the type of P. dichotomum was found at Mt. Observation. No.
15,732 was collected by Mr. Hatcher at Halliday’s Ranch and No. 15,436
at Killik Aike.
PROTEROTHERIUM PYRAMIDATUM Ameghino.
(Plate VIII, Fig. 5.)
Proterotherium pyramidatum Amegh.; Enum. Synopt., etc., 1894, p. 37.
As in the species of Lacaphrium of the same name, the antero-internal
cusp (protocone) of m* is relatively large, flattened on the inner face and
of quite pyramidal shape; there is no hypocone and the posterior cingulum ~
turns sharply forward at the inner angle, becoming continuous with the
sharp edge of the protocone.
Among the casts sent to me by Dr. Ameghino are two specimens
referred to the present species. One of these (No. 9), the type, is a frag-
ment of the right maxillary with all three molars in place, and the other
(No. 10) has all of the grinding teeth of both upper and lower jaws, except
mg. Although both individuals conform to the definition of the species
as given above, there are some instructive differences between them in the
character of m?. In the type, that tooth is much reduced in size, the
antero-external border not overlapping the hinder margin of m?; the two
external lobes are of nearly the same size and the posterior conule is
placed very near to the posterior cingulum. In No. to, on the other
hand, m2 is relatively larger and the anterior margin overlaps the hinder
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS.
69
border of m*; the two outer lobes are of less equal size, owing to the
narrowness of the posterior cusp, and the posterior conule is more removed
from the cingulum than is the case in the type. This second individual
shows that the upper premolars are of the P. australe type, p® and * having
nearly square crowns, with well developed tetartocone, while pz is very
small and single-rooted.
MEASUREMENTS.
Type.
Upper premolar-molar series, length
«premolar series, length
P1, length (2. ¢., antero-posterior diameter).
“ width (@. ¢., greatest transverse diameter)
P24, length
“ width
P3, length
“width
P4, length
“ width : ‘ F ; : : : i : ‘ :
Upper molar series, length . ‘ F : 6 é 5 é 3 .037
M1, length . : : : ; F ; ; i ; ‘ : .013
“ siprcliin ‘ F F F : : : : : : : 018
M2, length . ‘ ; : ‘ : é 0 3 ; : ; 0135
“ width . : : : : ; 0 : . : . : .018
M3, length . ‘ ; : i ; : : é : : : .O10
“ width . ‘ ; : 3 : ; : ; : ‘ .O165
Lower premolar series, length
P;, length
“width
P;, length
“ width
Ps, length
“ width
Pz, length
“ width
Mj, length
“width
Mz, length
“width
Locahties. — Not given.
No. To.
.O81
-044
.009 ~
.009
.O105
.O12
.O12
.O15
.O125
.O17
038
.O13
.O175
.O14.
0175
.O12
.018
.039
.0055
.0035
.O10
.0065
.O12
.009
.O125
.OII
-OII5
-OII
.O13
-OII
70 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
PROTEROTHERIUM BROWNII sp. nov.
(Plate IX, Figs. 2, 2a.)
The type and only known representative of this species is a specimen
belonging to the American Museum of Natural History (No. 9568) and
containing the upper dentition almost complete and unworn. The species
closely approximates P. australe in size and the grinding teeth most
resemble those of the latter. The second upper premolar has two small
and conical internal cusps, which are almost median in position, and a
large posterior heel, defined by the elevated cingulum. This pattern is
different from that of the corresponding tooth in any other species which
I have observed, and, if constant, is doubtless a valuable diagnostic char-
acter. In p® and “the tetartocone is well developed and in the upper molars
the posterior conule is almost exactly midway between the two internal
cusps. M?# is remarkable for the extreme reduction of the postero-external
cusp, a reduction greater than in any other known example of the genus.
MEASUREMENTS.
Upper dentition, length i2—m3 : .106 P3, width . ; : 0 ¢ .O15
12, antero-posterior diameter ; .007 Pe lengthy: : i . : .O125
““ transverse ss j .0075 “ width . i : : : .O16
Upper premolar-molar series, length .076 Upper molar series, length . 5 .0365
«« _ premolar series, length : .042 M4, length . : : , : .013
P1, length (z. ¢., ant.-post. diam.) . _—?.008 “ width . : : : ; .O17
_ “ width (2. ¢., transverse diam.) . .007 M2, length . : : 4 : .O14
P2, length . : : 5 : .O105 ewicthie j : ; F 018
“ width . 5 : ; ; .O1I5 M3, length . : 3 0 : .O10
P3, length . F ; : - .O12 “ width . 5 ; 6 5 .018
Locality.—The type was collected by Mr. Barnum Brown at Monte
Leon.
This species is named in honor of Mr. Brown, who discovered and
collected it.
PROTEROTHERIUM BRACHYGNATHUS Ameghino.
(Plate X, Figs. 12, 13.)
Proterotherium brachygnathum Amegh.; Enum. Synopt., etc., 1894, p. 38.
Licaphrium prochvum Amegh.; Ibid., p. 42.
The type of this species is a fragment of the symphysial region of the
mandible, with only one tooth, pr of the left side, intact. The lower tusk
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. qi
is slender and procumbent, doubtless an indication that the animal was a
female. All of the teeth, from is backward, are closely crowded together
and without diastemata, which is the diagnostic feature of the species.
The single complete tooth, pz, measures 12.5 mm. in antero-posterior, by
9.5 mm. in transverse diameter, and the depth of the mandible below p*
is 19.5 mm.
The type of Lecaphrium prochvum is the right horizontal ramus of a
mandible with all of the teeth, except the median incisor and the canine,
in place, and appears to have been a slightly smaller animal than the pre-
ceding individual. The lower tusk (iz) is much larger and more erect
than in the latter, but this is probably merely a sexual difference. The
alveolus of the missing canine is almost in contact with those of iz and p,,
and the latter, which is small, extensively overlaps the anterior border of ps.
In the table, the measurements are taken from a cast of the type of Z.
prochvum.
MEASUREMENTS.
Lower dentition, lengthi,-m,; .092 Py, width . ° : 5 : 008
I,, antero-posterior diameter . : .008 Pz, length . : i 4 3 .O115
“ transverse “ ; : .005 “width . j ‘ : : .O10
Lower premolar-molar series, length 077 Lower molar series, length . : .038
«« premolar series, length F .039 M,, length . : : : : -OII
P;, length (@. ¢., ant.-post. diam.) . .0075 Coe width : ; : ; .O10
“ width (2. ¢., greatest trans. diam.) .003 My, length . ‘ i F : .O125
P;, length . ¢ : . : -O105 “ width . 6 : c 6 .O10
“width . ‘ ; : 6 .005 Mg, length . j : : : .0135
Py, length . : : : : .O12 “width . : ; ‘ : .0095
Localities. — Not given.
PROTEROTHERIUM INTERMEDIUM Ameghino.
(Plates VIII, Figs. 4, 4a; X, Figs. 7, 9, 10.)
Proterotherium intermedium Amegh.; Enum. Synopt., etc., 1894, p. 38.
The type of this species (Pl. X, fig. 7), is the right horizontal ramus
mandibuli of an old individual, with the anterior teeth badly broken. A
specimen in the collection of the American Museum (No. 9267, Pl. X, figs.
9, 10) consisting of the facial region of a skull and associated lower jaw, and
a young mandible in the Princeton collection (No. 15,996, Pl. VIII, figs.
4, 4a), appear to be referable to the same species. The posterior upper
premolars, p* and *, are intermediate in type between those of P. austvale
72 PATAGONIAN EXPEDITIONS: PALA‘ONTOLOGY.
and those of P. cavum, the postero-internal cusp, or tetartocone, being
smaller than in the former species, larger than in the latter. In m* the
progress of abrasion has united the posterior conule with the hypocone,
as in P. australe, and in both m* and m? between the two internal cusps
is a minute pillar, which is present, though apparently not constant,
in many of the species, but attains importance only in P. acre (q. v.).
M2? agrees closely in size with that of P. perfolitum and also in the very
unusual feature that the two external lobes of this tooth are of nearly
equal width. It differs, however, from the latter species in the develop-
ment of the hypocone, which is larger than in any other species which I
have observed, but is wanting in P. ferfolitum. In the mandible, the
canine is separated by unusually short diastemata from the tusk and pj.
The latter is very small and has a single cylindrical root.
In the succeeding table, No. 20 is a cast of the type-specimen; No.
9267 is in the collection of the American Museum and No. 15,996 in that
of Princeton University.
MEASUREMENTS.
No. No. No.
: 9267. 20. 15,996.
Upper dentition, length i2 -m2 : ‘ é : j ; .094,
I2, antero-posterior diameter . : : : : : : .007
“‘ transverse diameter . : 3 ; ‘ 6 6 ; .006
Upper premolar-molar series, length . : : ; : ; .070
«premolar series, length . : . : 3 : 5; .036
P4, length (@. ¢., antero-posterior diameter) : : ; : .0075
“« width (2. ¢., greatest transverse diameter) : : : 3 .006
P2, length : : : : ‘ ; : ; 2 : .008
“ width = : - ; : 4 : 5 5 -O105
pe length. : : : : 6 9 . : é .O105
“width 0 : 6 : : 0 : i 3 . .O12
P4, length 6 : ¢ é c : é : : 6 O11
“width : ; 3 : : ; 5 4 F : .O145
Upper molar series, length : ; : : : : 6 .035
M1, length . : é : : : : : : ; .O12
“width c : . : : 6 : . 6 3 .O16
M2, length . ; ‘ 6 : , ‘ ; : : .O13
“width ; : ¢ 6 : : : : ; F .O17
MS length . 2 é : j : : 6 ‘ : ,O1I5
“width : : : : : : , : ‘ ; .0165
SCOTT: LITOPTERNA OF THE, SANTA CRUZ BEDS. 73
Vo. No. No.
92067. 20. 15,996.
Lower dentition, length i,-m; . : . ; : Z ; .O915 .089
I, antero-posterior diameter . ; ; : ; : : .0075 .008
“transverse diameter . ; 3 : : : : j .004. .003
Lower premolar-molar series, length . : : ; : : .074 .074
«« premolar series, length . j ; : : ‘ : .038 .038
Py, length =. , : ; : : : : ; : .006 .005
“width : ; : ; ; i : : : ‘ .003 .003
P,, length ; : : : : , : 5 ; ; .O10 .O10
“width : ; : s 5 : ‘ : : j .006 .005 .005
P,, length : : ; ; : i : : ; ; .OII .O1I5 .O12
“width : ; : : i ; : : : ‘ .007 .0075 .008
Pz, length i : i : : : : : F : OI .OIT .OLI5
“width : : , 3 ; : 3 : : : .0085 .0095 .O10
Lower molar series, length. ; F : : ‘ : : .036 .036 .036
M,, length . F : ‘ : F F : : ; -OIL OIL .O115
“width ; : : ; F : : i : : .0095 .009 .009
My, length 5 : : : : ! : ; : : .O12 .O12 O13
“width : : ‘ ‘ ‘ ; : ; : : .0095 .009 .009
Mg, length : 4 , : : : : : : 2 .013 .O14 013
“width i : 5 : ‘ : : : : F .0085 .008 .008
Mandible, depth below px .O19 .O17
Locahties.— Not given for type; No. 15,996 was collected by Mr.
Peterson, four miles south of Coy Inlet, and No. 9267 by Mr. Brown, but
the locality record has unfortunately been lost.
PROTEROTHERIUM PERPOLITUM Ameghino.
(Plate IX, Fig. 9.)
Proterotherium perpolitum Amegh..; Enum. Synopt., etc., 1894, p. 36.
This species, which is very inadequately known from a single tooth
(m= of the right side), may be distinct, or may be merely a variant of the
preceding one. The type agrees closely in size with the corresponding
tooth of P. zufermedium and also in the very unusual character of having
the two external cusps of almost equal width, but, on the other hand, the
hypocone, which in P. zntermedium is relatively very large, is entirely
wanting in the present species, and thus the tooth has a somewhat triangu-
lar outline.
The type-specimen measures 11 mm. in antero-posterior, by 1'7 mm. in
transverse diameter.
Locality. — Not given.
74 PATAGONIAN EXPEDITIONS: PALAZZONTOLOGY.
PROTEROTHERIUM CAvUM Ameghino.
(Plates VIII, Figs. 1-3; IX, Figs. 11, 11a; X, Figs. 15, 15a; XI, Figs. 9-92.)
Proterotherium cavum Amegh.; Enum. sistem., etc., 1887, p. 19.
Diadiaphorus sancte-crucis Lyddeker ; Anales del Museo de La Plata,
1, 0G Wsog, ps Co.
This would appear to be the commonest and one of the most distinctly
marked of the Santa Cruz species of the genus. It is characterized by
small size, though in this respect there is much variability, and by the
comparative simplicity of the upper premolars, p* and * having a smaller
tetartocone, or postero-internal cusp, than in any of the preceding species.
In m* the postero-external cusp (metacone) is less reduced than in most
species of the genus, but narrower than the antero-external (paracone)
and the hypocone is small, but it appears to be constantly present.
In the mandibular dentition, the canine is isolated by short, but distinct,
diastemata in front of and behind it, and px, though quite variable in size,
is generally larger than in P. zzfermedtum and is implanted by two roots.
In the table of measurements, No. 23 is a cast of an upper jaw in the
Ameghino collection labelled ‘‘co-type”’; No. 24 is the cast of a mandible,
also labelled ‘‘co-type,” but of a considerably smaller individual; No.
25 is a cast of an upper jaw of the same collection, while No. 26 is the
cast of the mandibular dentition of a fourth individual referred to this
species; No. 9245 is the skull in the American Museum of Natural
History which is shown in Plates VIII, figs. 1 and 14; IX, figs. 11, 11a.
The identification of this skull is somewhat uncertain, as the teeth are so
worn that the pattern is almost obliterated. The measurements of the
type are taken from Ameghino (894, 561).
MEASUREMENTS.
No.
Type. No. 23. No.25. 9245.
Upper dentition, length i2—m2 . ; é : & .099 .093 -IO1
2, antero-posterior diameter . : . ¢ 5 .006 .008 .006
“ transverse diameter . 4 : 4 5 .005 .008 .0055
Upper premolar-molar series, ener : ; j .075 .074 .068 5 .076
«« premolar series, length . : 2 : .040 .0375 -O415
P1, length (@. ¢., antero-posterior diameten) ; : .008 .009 .008 .O10
“ width (z. ¢., greatest transverse diameter 0 : .007 .007 .009 .007
8 ba)
P2, length : : ‘ : c . 0 .009 .O10 .0085 .O10
“width 6 5 2 6 : : . : .008 OI! .O12 .O105
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS.
P3, length
“ width .
P4, length
“width . 6 .
Upper molar series, length .
M1, length
“width
M2, length
“width .
M3, length
“width .
I,, antero-posterior diameter
“ transverse diameter :
Lower premolar-molar series, length
““ premolar series, length.
P5, length
“width
Pg, length
“width
Pz, length
“width
Pz, length~ .
“ width :
Lower molar series, length
M,, length
“width
Mg, length
«width
M,, length
“width
Type.
.009
.O10
.O10
013
.O10
.O16
.O14
.O17
.O12
.O15
No. 23.
.O1I
.O14
.OII
.O145
.036
.0125
.O16
.013
.O17
.O12
.O17
No, 24.
079
.040
.007
.003
.O105
.0055
.O12
.008
.OII
.009
:039
.OIL
.009
.O12
.009
.O14
.009
No. 25.
.0095
.O145
.O1T5
.O16
.033
.OII
.O17
.013
.O17
.O10
.018
No. 26.
.006
.004
:073
.036
.0065
.004.
.OII
.0065
.OII
.008
.OLI
.O10
-037
.O105
.O10
.OII
.O10
.013
.009
ik)
No.
92435.
-O105
.013
.OIT
.O15
035
.OIT
.O17
.O125
.O18
.O1I5
.O17
No.
15,722.
.007
.004
.080
.O4I ©
.009
.004
.OII
0055
.O12
.009
.O1TS
.O105
:039
.OII
.O10
.O12
.O10
.O16
.0095
Quite a notable difference may be observed between Nos. 23 and 25
in regard to the proportions of the premolars, which are considerably
shorter and broader in the latter.
In the succeeding table all of the measurements are taken from No.
9245.
76 PATAGONIAN EXPEDITIONS: PALA:ONTOLOGY.
MEASUREMENTS.
Skull, length in median basal line . .168 Occiput, width at top . : ; .029
“f “condyle to premax- Cranium, width at constriction é .032
illary : ; , : : .180 a greatest width é : O41
Cranium, length condyle to anterior Zygomatic arch, length ‘ ; .094.
rim of orbit . : : ; .110 Palate, length in median line . é .092
Face, length orbit to premaxillary . .070 “width at p+ : : : .020
Occiput, height . ; F ; .0575 Face, width over lachrymals . : .045
a width at base . ; i .047 Rostrum, width . : : , .022
A fragmentary fore-limb, No. 15,728, not associated with skull or teeth,
may be provisionally referred to this species. From this the following
measurements were taken.
MEASUREMENTS.
Radius, distal width . : : .023 Metacarpal III, proximal width . ?.016
us “thickness : : .O175 wg a ie thickness .O13
ag «width over articular Phalanx 1, digit III, length . : .037
surface. ; : : ; .O19 6G I, “ “ prox. width . .020
Radius, distal thickness over articu- Gt mi, @ @ Gd tdovieleness .O12
lar surface 3 : : : .O12 GC gg G w lenin . .0185
Ulna, distal width F : : .007 Gg WG WG to, Wiclin - .018
ce “thickness . ’ : -O105 Go gp 9G 0G ahh, sitet .O17
Carpus, length in median line . .020 Ungual, digit III, length ; 6 .028
WGN c : 6 025 “ « «greatest width . .025
Metacarpal II, proximal width ; .008 & « «prox. width F .018
A fore-foot, lacking the phalanges, is associated with the mandible, No.
15,722, and, as the measurements of the teeth indicate, this was an animal
of advanced age with unusually heavy grinding teeth. In the absence of
the upper premolars, the reference is provisional only. This specimen is
shown in Plate XI, fig. 9.
MEASUREMENTS.
Metacarpal II, proximal width ; .008 Metacarpal III, proximal thickness .O12
se a sf thickness . .O12 “ “distal width . ; .018
Metacarpal III, length . ; : .069 Metacarpal IV, proximal width . .007
sf “proximal width . .016 i a “ thickness .0085
Localities. — The type-specimen was found in the cliffs of the Rio Santa
Cruz; Nos. 15,722 and 15,728 were collected by Messrs. Hatcher and
Peterson at Killik Aike, and No. 15,712 five miles south of Coy Inlet.
In the collection of the American Museum, No. 9245 was obtained by Mr.
Brown at Felton’s Estancia, Rio Gallegos.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. Wil
PROTEROTHERIUM NITENS Ameghino.
(Plate IX, Fig. 4.)
Proterotherium nitens Amegh.; Enum. Synopt., etc., 1894, p. 37.
The propriety of separating this species from P. cavum is very doubtful.
It agrees well with the latter in stature and in tooth-pattern, especially in
the diagnostic character of the small size of the tetartocone in p* and * but
differs in the absence of the hypocone in m3, and the small prominence
of the external vertical crests, particularly of the mesostyle. This median
ridge is quite obsolete in p® and * and low and inconspicuous in the
molars. The cast of the type-specimen, however, gives the impression
that the jaw has been rolled and abraded and some of the teeth are more
or less broken. Besides, such a character may well be individual rather
than specific.
MEASUREMENTS.
Upper dentition, length . P : .068 P4, width . : c : ; .013
«« premolar-molar series, length .037 Upper molar series, length . : .031
P4, length (2. ¢., ant.-post. diam.) . .0085 M4, length . : 6 ; P .O10
“ width (2, ¢., greatest trans. diam.) .0075 “width . ; é : : .O17
P2, length . : 5 ; ; .0085 M2, length . ? é ; ; .O1I5
“ width . : : : 0 .010 “width . : : : : .O175
PS, length . ; ‘ : : -O10 M3, length . : : : : .0095
“width . : F 3 : .O12 “ width . : : F : O17
P4, length . : ° c : OI
Locatities. —Not given.
PROTEROTHERIUM KARAIKENSE Ameghino.
(Plate IX, Fig. 3.)
Proterotherium kavatkense Amegh.; Anales del Mus. Nac. de Buenos
WES, See, ey Is IUU (o, Bofey
This is a well-defined species, in which the molar pattern more nearly
approximates the perissodactyl type than in any other known Santa Cruz
representative of the family. The type specimen is a fragment of the
left maxillary, containing the five posterior teeth in intact and almost
unworn condition. In p® the anterior conule is hardly indicated, the
tetartocone is extremely small, and on the outer face the mesostyle is
quite obsolete. P*is more completely molariform than in P. cavum,
having asomewhat better developed tetartocone and more quadrate shape.
78 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
The perissodactyl similarity of the molar pattern is produced by the
slight backward displacement of the posterior conule, bringing it into
closer connection with the hypocone and opening the valley internally.
When abraded, the tooth shows two transverse crests, which though in-
complete, suggest those of Mesohippus or Anchithertum. The hypocone
is small in m? and absent in m*. In the latter, the posterior crest formed
by the elevated cingulum does not reach the external wall and thus the
longitudinal valley opens backward in quite peculiar fashion. On the
outer wall of the molars the mesostyle is unusually low and the external
cusps have but a slight concavity.
MEASUREMENTS.
P3, length (2. ¢., ant.-post. diam.) . OIL M4, width . : 5 j 5 .O165
“ width (2. ¢., greatest trans. diam.) . O13 M2, length . ; : : : O14
P4, length . 6 c 5 : .O12 “width . 0 : : 6 .O17
<owict hye ; : ; : O15 M3, length . F ; ; : .O12
Upper molar series, length . é 035 “width . : é : : .O17
M1, length . : : : : .O12
Locatity.— The specimens in the Ameghino collection were found at
Kar Aike.
PROTEROTHERIUM POLITUM Ameghino.
(Plate IX, Fig. 10.)
Proterotherium politum Amegh.; Anales del Mus. Nac. de Buenos Aires,
See, 3, U. WU, jo. 2E2,
This supposed species, represented by a single tooth, is quite indeter-
minable. No locality is given for the type.
PROTEROTHERIUM DODGEI Sp. nov.
(Plates IX, Figs. 1, 1a, 5,6; XI, Figs. 1-8; XII, Fig. 2.)
Among the material collected by Mr. Hatcher at Lake Pueyrredon is a
species of Proterotherium, represented by two very fragmentary skeletons,
which differs in significant details from any of the species previously
described. There is reason to believe that the Santa Cruz beds displayed
at Lake Pueyrredon represent a Somewhat lower and older horizon than
the beds along the Atlantic coast and it is therefore probable that we have
to do here with actual specific mutations and not with mere contempo-
rary variations.
The type of P. dodgez is a specimen (No. 15,107) consisting of the
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 79
facial region of a skull, with all of the upper teeth intact and in a moder-
ately advanced state of wear, the hinder portions of the left ramus man-
dibuli, with the molars in place, and several limb- and foot-bones in a more
or less incomplete condition, as figured in Pl. XI. The relatively large
size of the tusks and the prominent cingulum of the grinding teeth, exter-
nal in the upper teeth and internal in the lower, probably indicate that the
animal was a male.
The upper dentition, so far as can be judged in its worn condition, does
not differ in any important way from that of P. australe. P* is quite
simple and has a low internal cingulum ; p* and = have a large, well-devel-
oped postero-internal cusp (tetartocone), which gives the crown, especially
of p*, a subquadrate outline. M* has a much reduced postero-external
cusp (metacone) and the hypocone, which in P. australe is wanting, is
small, but quite distinct. Itisin the lower molars that the most distinctive
features appear and, had these teeth alone been found, one would have
had little hesitation in referring them to Lzcaphvium. As in that genus,
the valleys are shallow, the crescents thick and massive, and the pillar in
the posterior crescent is much larger and more conspicuous than in any
of the foregoing species of Proterotherium.
MEASUREMENTS.
Upper dentition, length i2—-m2 ; .108 M4, length . : j P : .O13
I2, antero-posterior diameter . 4 .0075 “ width . ; é 5 : .O17
“ transverse diameter . : : .007 M2, length . : ‘ : : .O14
Upper premolar-molar series, length .079 «width . : ; : : .0185
““ premolar series length. 6 .044 M2, length . : : : : .O12
P4, length (2. ¢., antero-post. diam.) .0095 “ width . ; : : : 018
“ width (2. ¢., greatest trans. diam.) .007 Lower molar series, length . : .O415
P2, length . 6 ; é : .O105 Mj, length . : c F F .O12
“ width . : 6 6 . OIL “width . : : 6 : .O10
P3, length . : : ; c .O12 M;, length . : ¢ Heer O13
“ width . a 6 : : .0135 “ width . é 3 é : .OIL
P4, length . : : : é O13 Ms, length . : : ; 3 .O16
“width . : é : : .O16 “ width . 6 : : 0 .O10
Upper molar series, length . ; .037
Most of the bones are in such a broken and crushed condition that accu-
rate measurements are very difficult or quite impracticable. The dimen-
sions in the following table are, however, close approximations to the
truth.
80 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
Face, length from anterior rim of Radius, proximal width , 0 .016
orbit 5 : 3 : : .078 “distal width . : i .O185
Cranium, width at postorbital con- Femur, proximal width ; ? .042
striction . : : ; : .033 Tibia, length on inner side. : .133
Rostrum, width . : : : .025 «distal width : : : .O19
Palate, length in median line . ; .O9I Fibula, distal width . : 6 .004.
“« widthatplL . : j .022 es “thickness ‘ : .009
fs CCenTT = : : ‘ .027 Astragalus, length : j a O32
Humerus, length from head . A 128 6 width of trochlea . : .018
“ proximal thickness 6 O41 « « “distal end : .O16
as distal width over trochlea 018 Metacarpal II, proximal width : .008
ss distal width over epicon- ss III, length . : . .068
dyles : : § .0295 “ proximal width . .O16
Radius, length . , : : 113
Locatity.— Lake Pueyrredon.
This species is dedicated to Cleveland H. Dodge, Esq., of New York,
whose oft-exercised liberality has been one of the main supports of the
Patagonian work.
PROTEROTHERIUM ACRE (Ameghino).
(Plate VIII, Fig. 7.)
Fleptaconus acer Ameg.; Enum. Synopt., etc., 1894, p. 44.
As was pointed out on a preceding page (p. 54) it frequently happens
in various species of Proterothertum that a small enamel pillar makes its
appearance, as a development of the cingulum, between the internal cusps
of the upper molars. In most cases, however, this pillar is minute and
very variable, differing much even in the opposite sides of the same jaw.
One individual, shown in Plate X, fig. 1, and perhaps belonging to an
undescribed species, has this pillar small, though very distinct on p*, m+
and +, at least, as these are the only teeth with completely preserved
crowns, and it may very well have been present in p? and m# also. In
Proterotherium acre the pillar attains a large size, becoming nearly as
large and prominentas the hypocone. So far, this species is known only
from a single tooth, an upper molar of the left side, which measures 14
mm. in antero-posterior, by 19 mm. in transverse diameter.
Locality. — Not given.
TETRAMERORHINUS Ameghino.
(Plate VII, Figs. 8-11.)
Tretramerorhinus Amegh.; Enum. SwiTOOite, GWE, MSIL, (D> BS:
—_
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 81
Though very doubtful as to the propriety of separating this supposed
genus from /votevotherium, I prefer to let it stand as distinct until more
material shall have been obtained for deciding the question. In his
original description Ameghino says of it: “Les os du nez sont formés
par quatre piéces distinctes, les deux nasaux et deux autres os qu’on peut
appeler des internasaux. A peu prés vers le tiers en avant de leur jonction
avec les frontaux, les nasaux se séparent formant comme les deux branches
dune fourche, entre lesquelles s’intercalent les os internasaux ; ces os se
prolongent trés peu en avant des nasaux et terminent en pointe. Par la
position que ces os occupent on ne peut pas les regarder comme les
homologues des prénasaux de plusieurs mammiferes”’ (’94a@, pp. 39-40).
Whether this structure represents anything more than an individual
abnormality, remains to be determined.
TETRAMERORHINUS FORTIS Ameghino.
(Plate VII, Figs. 8, 9.)
Tetramerorhinus fortis Amegh.; Enum. Synopt., etc., 1894, p. 40.
The type and only known specimen of this species has teeth which are
much worn, but display no significant difference from those of Pvofero-
thertum australe. The skull, as is clearly indicated in the cast, has been
subjected to some vertical crushing and the ‘“internasals” have been
pushed down below the level of the nasals. The edges of the latter are
smooth and rounded and the shape of the opening made by the depression
is very nearly symmetrical, so that the structure is apparently not due to
fracture from crushing. I am inclined to believe, however, that this is
merely an abnormal individual of P. australe, but a larger number of
specimens must be obtained before such a reference would be fully justi-
fied. The rostrum and whole nasal region are broader than is usual in
Proterothertum, and the supraciliary ridges are more elevated above the
brain-case.
The dimensions in the following table are taken from a cast of the
typical and only known representative of the species.
MEASUREMENTS.
Upper dentition, length i2-m3 : .106 Upper premolar series, length : .045
I2, antero-posterior diameter . ; .0005 P1, length (2. ¢., ant.-post. diam.) . .O1O
“« transverse diameter . ; .0065 ““ width (¢.¢., greatest trans. diam.) .009
Upper premolar-molar series, length .082 P2, length . 6 ; 6 ; .O105
82 PATAGONIAN EXPEDITIONS: PALAZEONTOLOGY.
MEASUREMENTS.
P2, width . ‘ : ; : .O12 Mi, width . : 2 : , .O185
P3, length . ; : 5 : .O12 M2, length . : F : : O14
“width . 3 : : : .O16 “width . : : : é .O19
PS,length . . : . : -O14 M3, length . ‘ - : 5 .O125
COWEN ag eg ah . .0175 “width . LOU SiS Seo th aeog
Upper molar series, length . . -039 Cranium, width at constriction . .036
M+, length . . : : . 0125 Rostrum, width . ‘ : ; .029
Locality. — Not given.
TETRAMERORHINUS LUCARIUS Ameghino.
(Plate VII, Figs. 10, 11.)
Tetramerorhinus lucavius Amegh.; Enum. Synopt., etc., 1894, p. 40.
The separation of this species from /voferotherium is of even more
doubtful propriety than in the case of 7: forts, from which it differs in
its decidedly smaller size. The teeth are very similar in size and struc-
ture to those of Proterotherium cavum, to which, it seems very probable,
this species should be referred. Such differences in the tooth-pattern as
may be noted are no greater than may well be regarded as mere individ-
ual variations. Thus, p® has a smaller and less prominent inner tubercle,
while in p? and * the postero-internal cusp (tetartocone) is somewhat larger.
Though unwilling to make any positive statement from the exami-
nation of a cast, I cannot but think that the division of the nasal bones,
which is asymmetrical and irregular, is a result of the vertical down-crush-
ing which the skull has evidently undergone. The somewhat unusual
width of the rostrum is probably likewise a result of the same cause.
Should, however, the division prove not to be due to crushing, it would
go far to confirm Ameghino’s interpretation, as it is very unlikely that
individuals of different species should show the same abnormality.
MEASUREMENTS.
Upper premolar-molar series, length. .0675 P4, length . : : 0 : -O105
“« premolar series, length. .. .036 “ width . : 2 : 5 013
P1, length (7. ¢., ant.-post. diam.) . .008 Upper molar series, length . ; .032
“width (2. e., greatest trans. diam.) .005 Mi, length . . : . . O11
P2, length . Q ‘ : ; .009 “ width . : F 3 : .O155
“width . : : : .008 M2, length . ; ‘ : 3 .O12
P3, length . i : 5 é .O10 “ width . : : 6 : .O16
“width . : F .O12 M2 length . : : : ; .O10
Locality. — Not given.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 83
TICHODON Ameghino.
(Plate VIII, Fig. 8.)
Tichodon Amegh.; Enum. SyMOpty sete. 1SOA pare:
TICHODON QUADRILOBUS Ameghino.
(Plate VIII, Fig. 8.)
Tichodon quadrilobus Amegh.; Enum. Synopt., etc., 1894, p. 43.
Known only from a single tooth and of quite indeterminate position.
This tooth, mz of the left side, measures 14 mm. in antero-posterior, by
6.5 mm. in transverse diameter.
Locahty. — Not given.
THOATHERIUM Ameghino.
(Plates XI, Fig. 12; XII, Figs. 3-13¢@; XIII-XV.)
Thoatherium Amegh.; Enumeracion sistematica, etc., 1887, p. 19.
Merycodon Mercerat; Rev. del Mus. de La Plata, T. I, 1891, p. 466 (fide
Ameghino).
Rhagodon Mercerat ; Ibid., p. 468 (fide Ameghino).
Proterotheritum WLydekker, in part; Anales del Mus. de La Plata, T. II,
1893, p. 63.
This genus represents the extreme modification among the Protero-
theriidze as regards digital reduction; indeed, it is the most completely
monodactyl animal known, decidedly surpassing the horses in this respect.
However, the relatively isolated position of the genus is shown not only
in the feet, but in all parts of the skeleton also. It may be characterized
as follows: (1) The upper lateral incisors are caniniform, but smaller than
in any of the preceding genera. (2) In the upper molars the two internal
cusps and the anterior conule are connected by a continuous .crest, while
the posterior conule is vestigial, or absent. (3) The lower lateral incisor
is not caniniform and is hardly larger than the median. (4) The lower
molars have no internal pillar and mg is without a talon. (5) The nasals
are shorter than in Proterotherium, longer than in Dzadiaphorus, and the
dorsal portion of the occiput is remarkably narrow and projects far behind
the plane of the condyles. (6) The limb-bones are all more slender and
elongate than in any of the preceding genera and the ulna and fibula are
more reduced. (7) The feet are strictly monodactyl, the lateral digits
84 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
being reduced to mere nodular vestiges of the proximal ends, and the
metapodials are longer and more slender than in any other genus of the
family.
Dentition. —(Pl. XIII, figs. 14-18.)
A. Upper Jaw. The upper incisor, though caniniform, is notably smaller
than in Proterotherium and is somewhat more rounded and less trihedral in
cross-section. Though young skulls with the milk-teeth are not uncommon,
I have seen no skull with unworn premolars. When considerably worn
the last three premolars have a narrow, triangular valley in the middle of
the crown. While the elements of the molar crown are the same as in
Proterotherium, yet the appearance is quite different; in m+ and m* the
anterior conule and the two internal cusps are connected by a continuous
and somewhat longitudinal ridge, the various cusps projecting but slightly
below the level of the crest and demarcated by very shallow vertical
grooves. The apices of the cusps are very early worn away and then the
tooth has merely a central enamel valley like that of the premolars. The
posterior conule is greatly reduced and forms but a narrow and slender
spur from the longitudinal ridge, which may or may not reach the outer
wall of the crown. The third molar differs from the other two in the
great reduction of the postero-external cusp, which is convex and more
posterior than external in position; the postero-internal cusp is very small
and separate from the antero-internal.
B. Lower Jaw. One of the characteristic features of 7zoatherium is to
be found in the relative size of the two lower incisors, the lateral being very
little larger than the median, a marked distinction from all the other
genera of the family. Both of the incisors are more procumbent than in
Proterotherium, pointing almost directly forward. The canine and first
premolar resemble those of the last named genus, but the second differs
in the internal ridges, of which the anterior one is smaller and the pos-
terior one larger. The third and fourth premolars are molariform. The
molars resemble those of Dzadiaphorus rather than those of Proterothe-
vium, as they have no postero-internal pillar and mz has no talon, while
the external angles of the crescents are more rounded and not so sharp.
Milk- Teeth. —The upper deciduous incisor is somewhat smaller than its
successor and of rather more trihedral shape. After a short diastema this
tooth is followed in some individuals, not in all, by a second, very small,
premaxillary tooth, probably di?, which is acutely conical in shape. The
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 85
first upper milk-premolar (dp+) is larger than p+; its crown is made up of
a very large external cordate cusp and two internal cusps, of which the
anterior is very small and hardly more thana raised cingulum; on the
outer side of the tooth, near the anterior border, is a deep vertical groove.
The second upper temporary premolar is of similar pattern, but much
larger and with better developed internal cusps. The third is like a
molar, with two external cusps, but has a relatively greater antero-pos-
terior elongation, while dp* is altogether molariform.
The difference in size between the median and lateral incisors of the
mandible is even less in the temporary than in the permanent dentition
and the milk-canine is smaller than its successor. In the premolar series,
dpr is like px, but dpz is larger than pz and has quite a different appear-
ance; of the two internal cusps, the anterior one is better developed and
the posterior one less so, while the ridge that runs back from the summit
of the protoconid ceases at the postero-internal cusp, while in pz it is con-
tinued for the whole length of the crown. The last two milk-premolars
differ from ps and z only in their greater elongation antero-posteriorly.
Skull (Pls. XIII, fig. 12; XIV). —JIn general, the skull resembles that
of Proterotherium, but is smaller, lighter, more slender and graceful, and
there are several constant differences in details. In the first place, there
are certain differences of proportion, which though not striking, are yet
not without importance. The cranium is somewhat shorter and the face
correspondingly longer, the orbit, which is relatively larger, having a
rather more posterior position: the sagittal crest is considerably shorter
and the temporal foramina have a conspicuously shorter antero-posterior
diameter ; the face tapers forward more gradually and the muzzle is
narrower and more slender. Another and very characteristic difference is
in the shape of the occiput, which is quite as broad at the base as in
Proterothertum, but narrows rapidly, making the dorsal moiety extremely
narrow and pointed, like a slender, lanceolate arch: this dorsal portion of
the occiput projects backward much farther than in Proferotherium. The
basioccipital is relatively broader than in the latter and has a better defined
median keel and the occipital condyles are more widely separated ventrally.
The brain-case is shorter, fuller and more rounded than in Pvofero-
thertum and descends more abruptly behind, making the posterior part
of the sagittal crest very much higher. The squamosal is much as in the
latter genus, but the postglenoid process is shorter and has a more
86 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
swollen, mamillate appearance, and is more extensively invaded by the
very large and conspicuous glenoid foramen: the zygomatic arch is shorter
and its dorsal border is continued as a low ridge up to the sagittal crest,
making a more definite posterior boundary to the temporal fossa. The
very large lachrymal is more extended upon the face and has no spine;
the foramen is, as in Diadzaphorus, placed in front of the orbit, not on its
rim, as it is in Proterothertum. The frontals are longer than in the latter,
reaching farther behind the orbits, especially in the median line, where they
extend farther between the divergent ends of the parietals. The sinuses
are larger and cause more prominent protuberances on the forehead ; the
superficial prominence on each side is divided into two parts by the vas-
cular groove which runs forward from the supraorbital foramen. This
arrangement, which is not well shown in very young skulls, becomes very
conspicuous in old animals and gives a characteristic appearance to this
region of the skull.
The nasals are considerably shorter than in Proterotherium, longer than
in Diadtiaphorus and, as in the former, they articulate with the premaxille,
though the suture is shorter. Consequently, the anterior nares are inter-
mediate in form between the two genera, being longer and more oblique
than in Proterothertum, shorter and more vertical than in Déadiaphorus.
Otherwise, the premaxillze are much as in Proferotherium, but the incisive
foramina are larger and the spines correspondingly longer, and in the
edentulous region between the incisor and first premolar the palatal sur-
face is not so contracted, nor so distinctly demarcated from the lateral
surfaces. The facial, or preorbital, portion of the maxillary is lower dorso-
ventrally than in Protevotherium ; the palatine processes extend forward
between the premaxillze so as to take part in the formation of the incisive
foramina. The palate is of more uniform width than in the last named
genus and less deeply concave ; the palatines are very long.
The mandible is very like that of Proterotherium, the differences being
chiefly in the ascending ramus, the ventral border of which descends less
below that of the horizontal ramus and thus the inferior profile of the jaw
is less sinuous in this region ; the coronoid is more slender, recurved and
tapering, and the sigmoid notch is much wider, while the masseteric fossa
is shallower.
Vertebral Column and Ribs. — As already mentioned in the account of
the family given on a previous page (p. 10) the vertebral formula is quite
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 87
uncertain. Of the present genus I have 4 cervical, 8 thoracic, 4 lumbar and
2 sacral vertebre, most of them belonging to asingle individual. A care-
ful comparison of these with the complete back-bone of 7Zeosodon makes
it appear probable that the number was a little greater than in that genus;
viz., C. 7, Th. 15, L. 6. All of the vertebrze preserved resemble the cor-
responding ones of Proferotherium, though much smaller and lighter, and
there are many differences in points of minor importance.
The atlas (Pl. XII, figs. 3, 3a) is short, broad and high dorso-ventrally ;
the anterior cotyles are large, widely separated dorsally, but quite closely
approximated ventrally, and slightly emarginated in the middle of the
lateral border. The neural arch is thick and convex and the spine is
reduced to a vestige. The posterior cotyles are small and nearly plane
and are not connected with the fossa on the inferior arch, which is narrow
and deeply concave, but quite short antero-posteriorly ; the hyapophysis is
a spine-like tubercle on the hinder edge of the inferior arch. The verte-
brarterial canal is very short, opening anteriorly into a large fossa on the
side of the neural arch, which is deeper and better defined than in the atlas
of Proterotherium. The atlanteo-diapophysial notch shows no tendency
to become a foramen, as there is no process from the anterior border.
The axis (Pl. XII, fig. 4) has a curiously shaped centrum; seen from
below, it is of subquadrate outline, the anterior width exceeding the length.
Anteriorly, the centrum is broad, much depressed and very thin dorso-
ventrally, behind the transverse processes it narrows and thickens, mak-
ing the posterior face trihedral; the ventral keel is well defined, though
not very prominent. The anterior cotyles for the atlas are low and broad,
of irregularly trapezoidal outline, the outer border exceeding the inner in
dorso-ventral length: the articular surface is saddle-shaped, concave trans-
versely and convex dorso-ventrally. When the atlas and axis are placed
together, there appears to be a surprising lack of adjustment between the
respective articular surfaces, which would necessitate the presence of un-
usually thick cartilages to make up for this. One’s first suspicion natur-
ally would be that the two bones belonged to different animals, but the
conditions under which they were found seem to exclude such a possi-
bility. The odontoid process is strikingly long and slender and of irregu-
larly cylindrical shape, which is in marked contrast to the short and heavy
process of Diadtaphorus. On each side of the base of the odontoid is a
deep and narrow sulcus, separating it from the cotyles. The transverse
88 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
processes are very slender and each is perforated by a vertebrarterial canal
so short as to be hardly more than a foramen. The neural canal is quite
large, especially the anterior opening; the spine is so broken that its
shape cannot be accurately determined, but evidently it was a large, more
or less hatchet-shaped plate. The postzygapophyses are quite small.
The (?) fifth cervical (Plate XII, fig. 5) has a short, broad, moderately
depressed and slightly opisthoccelous centrum; the transverse process is
pierced in the normal way by the vertebrarterial canal, which is very much
longer than in the atlas or axis, and the inferior lamella, which is well
developed, is divided into anterior and posterior portions. The neural
canal is relatively large and the spine is distinct, though short and slender,
and inclined forward. The anterior zygapophyses are large and slightly
concave, the posterior much smaller.
The only other cervical preserved is an uncharacteristic fragment of a
centrum, noteworthy only for the obliquity of the posterior face.
In view of the great elongation of the limbs, the neck in 7Zoatherium
is surprisingly short, considerably shorter than the skull, to the basal
length of which it bears the proportion of 81 : 100, approximately.
As already mentioned, the number of thoracic vertebrze is quite uncer-
tain, though the available evidence seems toindicate 15 as the more prob-
able number. On this assumption, the thoracic region, measured in a
straight line would stand in proportion to the skull as 160: 100. The
first thoracic vertebra has a small, somewhat depressed, trihedral centrum ;
the transverse process is short, but very broad and depressed, ending ina
very large deeply concave facet for the tubercle of the first rib: the neural
canal is large and the spine broad, heavy and, presumably, high, with
moderate backward inclination. In Dzadiaphorus even the second thoracic
has a slender, tapering and relatively short spine, such as is found in the
posterior cervicals of many ungulates. The prezygapophyses are of
cervical type and the postzygapophyses quite like those of a lumbar
vertebra, small, convex and semicylindrical, projecting from the sides of
the neural arch: there are no metapophyses.
The second thoracic has a slightly smaller centrum than the first and
considerably shorter and more rod-like transverse processes, which bear
much smaller and but slightly concave facets for the tubercles of the second
pair of ribs, while the neural canal and spine are similar to those of the
first ; the prezygapophyses are also similar, but smaller and less concave,
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 89
and bear low, spine-like, incipient metapophyses: on the other hand, the
postzygapophyses are of the normal thoracic type, placed on the under
surface of the neural arch and very large.
In the middle portion of the thorax (Pl. XII, fig. 7) the vertebrae have
larger and more depressed centra, with kidney-shaped faces; the trans-
verse processes are prominent, but short and rod-like, and the metapophyses
are prominent; the neural canal is small and the spines have a remarkably
strong backward inclination; the zygapophyses are long, extremely narrow
and widely separated. In the posterior thoracic region (Pl. XII, fig. 8)
the centra become longer, broader and more depressed, while the trans-
verse processes are greatly reduced, becoming vestigial on the last two or
three vertebra. Curiously enough, on the last four or five vertebree the
transverse processes have no articulation with the ribs, which is not true
of Diadiaphorus or Theosodon, but does occur in the Santa Cruz Typo-
theria. Probably the final thoracic is the anticlinal vertebra, as in the
two genera last named, and on what is presumably the antepenultimate
vertebra the postzygapophyses assume the lumbar pattern.
It is exceedingly likely that there were six lumbar vertebree, and the four
preserved are the last and probably the first, third and fourth. Assuming
the formula of-six, the length of the loins is to that of the skull as 86: 100,
and the entire length of the trunk, measured around the curve of the spinal
column, is 251, when the basal length of the skull is taken as 100. The
anterior and median lumbars have long, rather slender and depressed
centra, with distinct ventral keels, broad, plate-like and antroverted trans-
verse processes, and broad spines with moderate forward inclination; the
zygapophyses are cylindrical and interlocking, the metapophyses are greatly
reduced and the neural canal is large. Compared with those of Profero-
therium, these vertebrz are distinguished by their more slender transverse
processes, the smaller metapophyses and the less inclined spines. The
last lumbar (Pl. XII, fig. 9) is quite different from those described ; it has
a wide, very much depressed centrum, with broad anterior and extremely
small posterior face; the transverse processes are very broad and each has
on its anterior border near the centrum a small, slightly convex facet for
the fifth vertebra, and on the posterior border a much larger, deeply
concave surface for the prominent convexity on the pleurapophysis of the
first sacral: each of these posterior facets is actually larger than the hinder
face of the centrum. The neural canal is broad and the somewhat narrow
90 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
spine has but a slight forward inclination. Of the zygapophyses, the
anterior ones are large, the posterior much smaller.
As in Proterotherium, the number of sacral vertebree probably exceeded
six, but only two are preserved, belonging to a very young animal with
milk teeth. The first sacral has a broad, extremely depressed centrum,
which narrows much posteriorly; the neural canal is very much smaller
than that of the last lumbar, especially in the dorso-ventral diameter, and
the arch is separated by a considerable interspace from that of the second
vertebra, though this may be due to the immaturity of the animal, while
the spine is merely a vestigial crest. The anterior zygapophyses are
much reduced in size, though functional, and the posterior ones are
minute. The pleurapophyses are large and heavy, supporting the ilia
almost entirely, as the contact of these bones with the second vertebra is
very limited. On the anterior face of each pleurapophysis is a large,
prominent, convex and transversely oval facet for the concavity on the
transverse process of the last lumbar.
The second sacral is much smaller than the first and it is evident that,
as in Proterotherium, the sacrum becomes exceedingly slender posteriorly,
with neural canal reduced to a minimum.
No caudals are known, but the conformation of the sacrum renders it
almost certain that the tail was very short, as appears to have been the
case in all the known Santa Cruz representatives of this family.
A few fragments of ribs indicate that the anterior ribs were compressed
and plate-like, though quite slender, and the posterior ones more rounded
and rod-like.
_ Appendicular Skeleton. — Of the fore limb-bones, only a few fragments
have been preserved, the distal half of the humerus, the greater part of
the radius, the proximal and distal ends of the ulna and most of the manus.
Ameghino has, in addition, figured and partially described an almost com-
plete manus (944, p. 271, fig. 12), and thus a fairly adequate conception
of the structure of the fore limb may be reached. On the whole, the limb-
and foot-bones are much the same as in /voterotherium, but they are
relatively more elongate and much more slender and graceful, and there
are also certain other significant differences.
The humerus (Pl. XII, figs. 10, 10a) has a more slender shaft than in
Proterotherium ,; the distal trochlea has the same simple, pulley-like char-
acter as in the latter, but the supratrochlear fossa is shallower and the
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. gI
anconeal fossa is deeper, while the supinator ridge is almost entirely
obsolete.
The fore-arm bones (PI. XII, fig. 11) are separate throughout. The
head of the radius is more compressed antero-posteriorly than in Profero-
thertum and has better distinguished facets for the various parts of the
humeral trochlea, while the bicipital tubercle is more prominent; the
proximal part of the shaft is likewise more compressed antero-posteriorly,
but, for most of its length, the shaft is stouter than in the genus last
mentioned ; the distal end, however, is not so thick and the groove on its
anterior face for the extensor tendons is much shallower and less clearly
marked: the facets for the scaphoid and lunar are more deeply impressed,
more distinctly separated, and have a greater dorso-palmar diameter in
proportion to their width.
Of the ulna, we have only the proximal and distal ends ; the olecranon
is large, laterally compressed, thickened and slightly incurved at the
proximal end; the proximal part of the shaft is stout and trihedral, but —
very probably it was greatly reduced for most of its length, as the distal end
is relatively smaller than in Proterotherium, though it still retains a lateral
articulation with the lunar.
The carpus (Pl. XI, fig. 12) is essentially the same as in the tridactyl
genera of the family and still remains semi-taxeopod, the scaphoid articu-
lating with the magnum, but the lunar excluded from the unciform. The
modifications of the carpus, as compared with that of Proferothertum, are
less than would be expected from the strictly monodactyl character of the
manus, the differences being almost entirely in matters of minute detail.
Indeed, there is even less difference in the shape and mutual connections
of the carpal elements between Zhoatherium and Proterotherium than
between the latter and Dzadiaphorus.
The scaphoid has proportions almost identical with those seen in Pvo-
terotherium, but differs slightly in the shape of its facets; the surface for
the trapezoid notches the bone more deeply, giving a more nearly cuboidal
shape to the distal extension which carries the magnum facet, while that
for the trapezium is somewhat smaller.— The lunar is proportionately not
quite so high and narrow as in Protevotherium and the proximal facet, for
the radius, does not incline so steeply toward the internal side, and on
the outer side of this facet is a very small, though distinctly marked, sur-
face for the ulna, a facet which does not appear in Protevotherium. The
Q2 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
lunar articulates only with the magnum, the facet for which is somewhat
less concave palmo-dorsally than in the genus last named. —The pyramidal,
which is not yet definitely known in Proterotherium, is elongate proximo-
distally and very narrow transversely, giving to the bone a scale-like
shape; the proximal end bears a simply convex facet for the ulna, and the
distal end a small concavity for the unciform.—Of the pisiform I have
seen no example in either Diadiaphorus or Proterotherium, in Thoa-
therium it is quite elongate, very slender near the proximal end, expand-
ing toward the free end, which is also slightly thickened and incurved.
In none of the specimens which I have seen is the trapezium preserved,
but the facet for that element upon the scaphoid demonstrates its presence
and also that it was somewhat smaller than-in Pvroterotherium.—The
trapezoid is likewise rather smaller relatively than in the latter and differs
in being shorter proximo-distally.— As in all the known members of the
family, the magnum is the largest bone in the carpus ; in form, it bears a
general resemblance to that of Proferotherium, but is relatively somewhat
lower in the proximo-distal dimension, wider transversely and shallower
palmo-dorsally, which is chiefly due to the smaller size of the tuberosity
on the palmar face. The proximal surface is almost equally divided
between the facets for the scaphoid and lunar; the latter hardly rises so
prominently above the former as it does in Pvroterotherium and is more
saddle-shaped. On the distal portion of the radial side is a small, but
distinct, facet for the second metacarpal.—The unciform is very small,
especially in the transverse diameter; the proximal facet for the pyramidal
is almost a groove on account of its concavity transversely: the distal end
bears a small facet for the vestigial fourth metacarpal and a still smaller
oblique surface for the head of the third. The hook-like process, which
projects from the palmar face, is preserved, despite the very small size of
the bone.
The metacarpus (Pls. XI, fig. 12; XIII, fig. 10) consists of a single
functional member, mc. III, and two minute vestiges, which represent the
proximal ends of mc. II] and IV. Yet, notwithstanding this remarkably
perfect monodactylism, which is more complete than in any other known
mammal, the metacarpals retain their primitive connections with one
another and with the carpus in a surprising manner. The reduction,
complete and thoroughgoing as it is, is yet entirely of Kowalevsky’s
‘“inadaptive” type, and shows that Kowalevsky was mistaken in suppos-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 93
ing that a foot-structure of perissodactyl symmetry did not admit of the
inadaptive method of reduction. As a matter of fact, however, this
method has not been observed in any of the genuine Perissodactyla.
Metacarpal II is a mere vestige and consists only of the proximal por-
tion of the original bone; the head is relatively large, both transversely
and palmo-dorsally and quite extensively overlaps the head of mc. III, the
facet for which presents distally and covers the radial portion of me. II
for its whole dorso-palmar diameter. The facet for the trapezoid occupies
the entire proximal surface; that for the trapezium, which is relatively
much smaller than in Proterotherium, is obliquely lateral in position. On
the ulnar side is a facet for the magnum, and thus all the original connec-
tions are retained. — Metacarpal III, the only functional one of the series, is
relatively longer and much more slender than that of Proterotherium.
The proximal end is considerably expanded and is of nearly the same
dimensions as in the smaller species of Proterotherium, but the following
differences should be noted: (1) the facet overlapped by the head of me.
III is less oblique and more directly proximal; (2) the facet for the mag-
num is less simply concave transversely, becoming convex toward the ulnar
side; (3) the unciform surface is much smaller and presents more prox-
imally, less laterally ; (4) the shaft is longer, more slender and rounded,
less compressed palmo-dorsally. As in all of the members of this family,
the carpal connections of me. III are primitive, as the bone is excluded
from contact with the trapezoid and touches the unciform only by a mi-
nute lateral facet. Although the functional metacarpal bears such a
close general resemblance to that of the modern horse, it differs notably
from the latter in mode of articulation with the carpus.
Me. IV is a minute rudiment, measuring only 1 cm. in extreme length,
and is a compressed, scale-like bone, tapering distally to a blunt point.
These minute splint bones differ from those of the horse, not only in their
very much smaller size, but also in their more lateral position: me. II
still retains its connection with the magnum, and excludes me. III from
the trapezoid
The proximal phalanx is much narrower and less depressed than that
of Proterotherium and its distal trochlea is more grooved in the median
line; the second phalanx also is much more slender, while the ungual is
longer and narrower, more concave on the palmar face and with much
more prominent median dorsal beak for the trochlea of the second phalanx.
94. PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
The pelvis is represented by only a single specimen, derived from an
immature animal and lacking the anterior portion of the iliac plate. The
ilium, so far as it is preserved, resembles that of Proterotherium, but has
an even shorter peduncle, from which the anterior expansion broadens out
more abruptly ; the ischial border is sharp and well defined, but the pubic
border is very short and the acetabular border is obscure: the gluteal
surface is but slightly concave and there is no ilio-pectineal spine, but there
is a roughened tubercle at the anterior margin of the acetabulum, presu-
mably for the attachment of the gluteus minimus muscle. The ischium is
short, slender and laterally compressed, expanding posteriorly into a broad,
thin and strongly everted plate, which bears a small tuberosity : the sciatic
notch is very feebly indicated. The pubis is short, compressed and plate-
like, but has a slender backward prolongation on the ventral side, which
makes the symphysis long. The obturator foramen is a long, narrow
oval, smaller than in Proferotherium.
The femur (Pl. XII, figs. 12, 12@) is remarkably equine in appearance,
strongly resembling that of A/esohippus. The head is small and placed
upon a short, distinct neck, and is thus less sessile than in Proterotherium,
more antroverted and with the pit for the round ligament less extended
proximally, but of similar ovoid shape, with the long axis directed antero-
posteriorly ; while the bridge between the head and the great trochanter
is more deeply notched. The great trochanter is much more prominent
and rises much higher above the head than in the last named genus and
the digital fossa, though hardly so deep, is more elongate ; the second
trochanter is a long, thin ridge, gradually dying away upon the shaft ; its
proximal portion is not so thickened and rugose as in Proterotherium ; the
third trochanter is rather less prominent and antroverted, but longer proxi-
mo-distally than in the latter. The shaft is moderately stout and has a
slight sigmoid curvature; the linea aspera externa is less developed than in
Proterotherium, but the fossa for the plantaris muscle is even deeper and
more distinct. The rotular groove is narrower and slightly asymmetrical,
owing to the somewhat greater elevation of the internal border, and there
is a deep suprapatellar fossa. The condyles are widely separated and
asymmetrical, the external one being larger and more convex ; the articu-
lar surface is not continuous between the condyles and the rotular groove,
but is interrupted by a narrow, non-articular space on each side.
The patella is rather short proximo-distally and relatively broad and
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 95
thick. It is shield-shaped, tapering to a blunt point at the distal end.
The anterior face is somewhat rugose and the surface for the rotular
groove of the femur is quite small and obscurely divided into two facets
by a low intercondylar ridge.
The tibia (Pl. XII, figs. 13, 13@) is relatively longer and more slender
than in Proterotherium and slightly exceeds the femur in length, exclusive
of the great trochanter; the two parts of the bifid spine are even more
widely separated than in the latter genus and the facets for the femoral
condyles are of more unequal size, the external one being relatively larger ;
the cnemial crest is very prominent and heavy, but short, speedily dying
away upon the shaft, and the sulcus for the extensor tendon is very
deep and conspicuous ; the proximal fibular facet is extremely small. *The
shaft is slender and has a distinct lateral sigmoid curvature. The distal
end is narrow, the antero-posterior diameter exceeding the transverse; the
distal fibular facet is very small and divided into two parts, one lateral
and the other distal, the tibia extending over the fibula in a manner not
seen in any of the preceding genera of the family, somewhat like that
characteristic of the ruminant artiodactyls ; the internal malleolus is much
reduced and of little functional importance. The astragalar surface is much
as in Pvroterotherium, but with certain differences: the fossa for the inner
condyle of the astragalus is much shallower and the internal border much
lower, the posterior intercondylar tongue is longer and narrower, while
the facet on the anterior tongue for the pit on the neck of the astragalus
is more distal. In certain individuals the astragalar surface is invaded
from the inner side by a narrow, non-articular strip, which passes across
the intercondylar ridge, but not the outer condyle. This sulcus, the dis-
tinctness of which varies much, is not present in any specimen of Profero-
thertum which I have examined.
In marked contrast with the distal end of the tibia in 7/oatherium is
that of the horse, with its broad, antero-posteriorly compressed shape,
deeply concave facets for the astragalus, and very large and prominent
internal malleolus, while the fibula is firmly ankylosed with the tibia:
this structure is much better adapted to prevent dislocation than is the
arrangement found in 7oatherium, in which indeed the structure would
seem to be inadequate.
The fibula (Pl. XII, fig. 13) is much reduced and very slender, but
shows no tendency to coalesce with the tibia; the shaft is irregular and
96 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
very thin and the expansion of the ends is chiefly in the antero-posterior
direction; the sulcus for the peroneal tendon is even deeper than in Pro-
terothertum and its recurved anterior border ends in a larger and more
rugose tubercle. Anteriorly, the distal end extends somewhat beneath
the tibia, a ruminant rather than a perissodactyl character; the facet for
the calcancum is elongate antero-posteriorly, but very narrow, and that
for the astragalus is quite large and C-shaped and is principally confined to
the anterior portion of the distal end.
Of particular interest is the pes (Pl. XIII, figs. 13, 13@) of 7hoatherium,
as showing the extreme of inadaptive modification of the monodactyl foot,
just as the horses display the extreme of adaptive monodactylism. Further,
these fossils present us with an extraordinary case of convergent develop-
ment, since no one, after a study of them, will be inclined to bring the
Proterotheriidze into any close relations with the horses.
In the tarsus there is relatively little change from Proterotherium. The
proportions of the astragalus as to length and width are the same as in
the latter and form a strong contrast to the short, broad astragalus of the
horse: the condyles have a slight obliquity, which varies in different indi-
viduals, and have narrower borders than in /Pvotervotherzum, while the
articular surface is not reflected so far over upon the tibial side; the pit
on the dorsal side of the neck for the anterior distal tongue of the tibia is
shallower than in the latter and its distal border is less raised. The two
parts of the ectal calcaneal facet meet at a more acute angle and the surface
is much more deeply notched by an incision from the fibular side. The
neck is shorter and the navicular facet is reflected farther upon the dorsal
face along the fibular border; the sustentacular facet narrows more prox-
imally, somewhat as in Deadzaphorus.
The calcaneum differs from that of Proterothertwm in a number of par-
ticulars: the tuber, which is of the same relative length and similar form,
is rather more compressed and slender, with less thickened and club-like
free end, which has a straighter proximal border, owing to the less promi-
nent projection of the ventral portion: the fibular facet is somewhat
broader and less inclined toward the tibial side: the sustentaculum has a
more abruptly truncated inner side and the distal end of its facet is carried
up farther upon the body of the calcaneum : the distal end is considerably
shallower planto-dorsally.
The navicular is like that of Proterotherium, but the plantar border of
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. Q7
the deeply concave astragalar surface is narrower transversely. I have
not seen the entocuneiform, but Ameghino’s figure (’944, p. 270, fig. 11D)
shows it to be a large, irregular, scale-like bone, shorter and wider than
in Proterothertum. The mesocuneiform, which Ameghino has incorrectly
supposed to be a vestigial first metatarsal (’944, p. 270, explanation of
fig. 11), is extremely small and even more reduced than in the genus last
named. ‘The very large ectocuneiform has a greater proximo-distal length
in proportion to its width than that of Proterotherium, and the distal facet
for mt. III differs in being L-shaped, one arm extending across the dorsal
half and the other along the tibial side ; in the angle between the two arms
is a roughened, non-articular surface, thus making some approximation to
the condition seen in the horses: on the plantar side is a small facet for
the plantar hook of mt. III.
The cuboid differs in several respects from that of Proterotherium ; the
plantar hook projects more prominently backward, but does not descend
so far distally, and on its tibial side is a long, narrow facet for the plantar
hook of mt. III, a facet which has not been observed in any of the tri-
dactyl genera of the family: the facet for mt. III, though still oblique, is
more distal than lateral, and that for mt. IV, which is very much smaller,
is shifted so as to be behind the surface for mt. III.
In the horses the tarsus forms a nearly closed ring, the entocuneiform
and cuboid almost meeting on the plantar side, while in 7Zoatherium this
tendency is but slightly indicated in the articulation of the cuboid with the
plantar hook of mt. III.
The metatarsus, like the metacarpus, consists of one functional member,
mt. III, while mt. I] and IV are reduced to mere nodular vestiges ; these
vestiges are attached laterally to mt. III, though mt. IV is somewhat
shifted to the plantar side, while in the horse the attachment of both splints
is entirely plantar. Metatarsal II,as in Proterotherium, articulates with all
three cuneiforms, excluding mt. III from contact with the mesocuneiform.
According to Ameghino’s figures ('944, pp. 271, 273, figs. 12, 13) meta-
tarsal IIT is of the same length as the corresponding metacarpal ; it is rela-
tively much more elongate and slender than in Proterotherium and of asome-
what different shape, the head being broader with reference to the shaft,
which is much more nearly cylindrical and less compressed planto-dorsally ;
the cuboid facet presents rather less laterally and more proximally, and
that for the ectocuneiform is interrupted by a large non-articular surface,
98 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
corresponding to the similar area on the tarsal, as above described. A
very marked difference from Pvoterotherium is in the large plantar hook,
or beak, which in the latter genus projects very prominently backward,
but rises very little above the ectocuneiform facet and has no articulation
with the cuboid or ectocuneiform. In 7/oatherium, on the other hand,
the hook does not project so far backward, but rises far above the level of
the proximal articular surface and bears upon its fibular side a long,
narrow, oblique facet for the cuboid, and on the dorsal side is a very small,
but prominently projecting facet for the ectocuneiform.
Metatarsal IV is a small nodule, tapering distally to a blunt point and
articulating by small, plane facets with the cuboid and mt. III. Ame-
ghino has figured a minute bone (’944, p. 270, fig. 118) attached to the
fibular side of the cuboid, which he regards as a vestigial mt. V. In none
of the specimens which I have examined is this bone retained, nor is there
any facet for it upon the cuboid. I am therefore inclined to believe that
this bone cannot be regarded as a normal member of the metatarsus,
especially as nothing of the kind is indicated in any of the preceding
genera of the family.
Phalanges are present only in the functional digit. The proximal
phalanx is longer, much more slender and less flattened planto-dorsally
than in Proterotherium,; the groove of the proximal trochlea for the meta-
tarsal carina is wider and has more sloping sides, and notches the dorsal
border somewhat more deeply: the distal articular surface is not reflected
so far upon the dorsal surface and narrows more proximally.
The second phalanx is also narrow and less depressed than in Profero-
thertum, the proximal trochlea is more deeply concave and the median
dorsal beak is much more pronounced, while the distal trochlea is more
concave transversely.
The ungual phalanx is longer, narrower, more pointed and much less
depressed than that of the manus, and consequently has a much more
convex dorsal surface; the proximal trochlea is obscurely divided into two
condyles and has a smaller transverse and greater dorso-plantar diameter
than that of the manus. Curiously, the hoofs of 7oatherium have a less
equine appearance than those of the tridactyl genera, which is perhaps to
be explained by the small size and lightness of the animal.
On a superficial examination, the pes of Z7oatherium appears to be
strikingly like that of the horse, but a closer study reveals a number of
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 99
very significant differences, which preclude any close association of the
two families. (1) In 7hoatherium the tarsus is fundamentally different ;
(2) the calcaneum retains its primitive connection with the fibula and is
nearly intermediate in character between the artiodactyl and the perisso-
dactyl type (the fibulo-calcaneal articulation of the horses has been sec-
ondarily acquired and is of an entirely different nature); (6) the astraga-
lus is long and narrow and has a depressed-convex head for the navic-
ular, which recalls that of the Condylarthra, and is widely removed from
the cuboid, while its facet for the sustentaculum is very artiodactyl in
character; (c) the navicular and ectocuneiform retain their relatively great
proximo-distal length, very different from the low, broad, disc-like bones
of the horse; (@) the cuboid and ectocuneiform are well separated on the
plantar side.
(2) The mode of digital reduction is inadaptive, mt. III being shut off
from the greatly reduced mesocuneiform, which, though almost atrophied,
is not ankylosed with either of the adjoining bones; the cuboid surface is
oblique, as much lateral as proximal, while the ectocuneiform surface is much
less extensive than in the horse. In the horses, mt. III articulates with
all the distal tarsal bones by surfaces which present proximally and which
are so arranged as to cover almost all the periphery of the proximal end,
and there is no plantar hook. In 7/oatherium these facets form less than
a semicircle, though this is, to a certain extent, compensated for by the
great hook which arises from the plantar side and articulates with the
cuboid and ectocuneiform. In brief, the Litopterna have solved the
problem of monodactylism in a manner which is distinctly different from
that followed by the Perissodactyla.
Restoration (Pl. XV).—The lightness and grace of Thoathertum are
conspicuous features. The head is smaller and lighter, proportionately
somewhat longer than in Diadzaphorus (see Plate I), but of more slender
shape and much shallower dorso-ventrally. The neck is strikingly short,
which is made all the more conspicuous by the elongation of the limbs.
The length of the trunk remains largely conjectural and the appearance of
the skeleton, as given in Plate XV, might be materially changed by the
discovery of a complete vertebral column. From the evidence now avail-
able, it seems very likely that the trunk was intermediate in relative length
between the artiodactyl and the perissodactyl type, a little longer than in
the former and slightly shorter than in the latter. The remains preserved
100 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
indicate a moderately elongate thorax and a short lumbar region. That
the tail was short, is made evident by the character of the sacrum. The
limbs are long and slender, much more so than in any other known repre-
sentative of the family and, in particular, the feet are much more elongate
than in any of the preceding genera. Limbs and feet have a strong, though
superficial, resemblance to the horses and, as frequently emphasized, the
feet are more strictly monodactyl than in any other known mammal. The
equine likeness is confined to the appendicular skeleton; there is little in
the skull and still less in the vertebral column to suggest such likeness.
Species. —In strong contrast to Proterothertum, Thoatherium is not
characterized by great variability or by numerous species, well or ill
defined. Only one species is at all well known and the others which
have been named are founded upon very imperfect material.
THOATHERIUM MINUSCULUM Ameghino.
(Plates XI, Fig. 12; XII, Figs. 3-13¢; XIII, Figs. 1, 2,5, 10-18; XIV, XV.)
Thoatherium minusculum Amegh.; Enum. sistemat., etc., 1887, p. 19.
Merycodon rusticus Mercerat; Rev. del Mus. de La Plata, T. I, 1891, p.
467 ( fide Ameghino).
Merycodon Damest Mercerat ; Ibid. ( fide Ameghino).
Rhagodon gracilis Mercerat ; Ibid., p. 468 (fide Ameghino).
Thoatherium crepidatum Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891,
D> 297:
Proterotherium cavum Lydekker (zon Amegh.); Anales del Mus. de La
Platay stein sosip ao?
Thoatherium rhabdodon Amegh.; Enum. Synopt., etc., 1894, p. 45.
By far the most abundant and the only well known species of the genus is
T. minusculum. As the generic description has been taken almost entirely
from this species, it is unnecessary to repeat the accounthere. It may be
added, however, that unworn examples of m2 show that the hypocone is
absent and that the very large protocone is separate from the posterior
transverse cingulum, though there is some variability in the pattern of
this tooth. 7: crepidatum and T. rhabdodon differ from 7: minusculum
only in the development of the basal cingulum, a very untrustworthy
criterion. In the table, No. 62 is the cast of a mandible in the Ameghino
collection labeled ‘“‘ 7: mcnusculum, co-type”; No. 60, a cast of frag-
mentary upper and lower jaws referred to the same species ; No. 66, a cast
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. IOI
of the type of 7: crepidatum, and No. 69, a cast of a second individual
with similar reference, while No. 75 is from the type of 7: rhabdodon.
All these casts are from originals inthe Ameghino collection. No. 15,721
is the skull of a very old animal. No. 15,714 is the mandible of an old
animal and No. 15,719 an animal at maturity.
MEASUREMENTS.
No. No. No. No. No. No. No. No. No.
62. 60. 66. 69. 75. 15,240. 15,721. 15,714. 15,719.
Upper dentition,
length i2-m2 —. .100 .100 §©.094
Upper cheek-teeth
series, length i 070 =.073 .072
Upper premolar
series, length ; 036 §=.038 .037
Pl, length . E .007. +.0085 .008 .008
“width é 6 007. .007 .007 .007
P2, length ‘ i .008 .009 .009 .009 .0085
“ width ; 0 009 .O1I0 .O10 .0095 .O10
P3, length 5 : .0IO .O10 .O10 .0095
“width é ‘ O12 012 .013 .O12
P4, length ‘ : OIIT .OII .OI1I .O1I5 .O10 .O10
“width ‘ : O14. .O14 .0135 .O13 .O125
Upper molar series,
length . ; : 035 .035 .036 .034 .031
M4, length . : O12. O12 .O1I5 .O115 .O10 .0095
“width : : O14. .O14 .O15 .O14 O15 .O14
M2, length . ; 013. .O14 .013 O12 .OII
“width ; : 016 .O17. .O16 O16 = .O15
M3, length . 3 013. .O125 .O125 .O1I2 .O105
“width : ‘ O16 O15 .O15 UR Owy
Lower dentition,
length, iz-m; . .090 .092 .0o9I —.O9I
Lower cheek-teeth
series, length F .070 .073 .073 +~.076
Lower premolar
series, length : .034 .036 .030 .037
Pz, length : : .007 .006 .006 =. .0065
“width : : .004. .004. .004, .004
Ps, length . : .009 .009 .O10 = .O105
“width : 5 .0055 .006 .005 .006
P;, length .. ; .0095 .O105 0105 .OLI
“width : : .008 .0075 .008 ~=—-.008
Pz, length . ; .O1IS .O12 ,OIL O15
102 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
No. No. No. No. No, No. (No. No. No.
62. 60. 66. 69. 975. 15,240. 15,721. 15,714. 15,719.
Pz width .008 .009 .008 .009
Lower molar series,
length .036 .037 037. + .039
M,, length .O10 .O105 -O105 .O115
“width .008 .008 5 .008 .009
M,, length O12 013 .0125 .013. 0135
“width .009 .0095 .0085 .009 .0095
Mx, length 014 .O14 .O14 O13 .O14
“width .009 =. .008 .008 .008 =. .008
The dimensions of the skull in the following table are taken from No.
15,721, a rather small and very old individual, which had lost the anterior
premolars (p1—p3) during life, and those of the mandible from No. 15,719,
a much younger animal, in which mz had just come into use.
Skull, median basal length
“length condyles to premax. .
“extreme length
Cranium, length condyles to anterior
rim of orbit ,
Cranium, width at postorbt con-
striction
Cranium, greatest aHtGith
Occiput, height
as width at base
a ““ over condyles .
at top
Face, length orbit to osisageeell
ce ce
MEASUREMENTS.
.150 Forehead, width over middle of orbits
.162 Face, width over lachrymals .
-181 Rostrum, width
Palate, length in median line
.093 «width at m2
Mandible, length 5
.035 ‘s « angle to mz
O41 3 height of coronoid .
.053 sf «condyle
.047 ‘s length of symphysis
.031 us depth below pz
O15 “ e “my
.078
057
.O51
.023
.085
.023
-139
.048
079
.063
.028
Kop fe)
.024.
A comparison of these dimensions with the corresponding ones of Pyo-
terotherium cavum (p. 76) will show how different are the proportions of
the two skulls.
The measurements of the vertebrze given below are derived from three
individuals, Nos. 15,719, 15,721, and 15,722, all of which agree closely
in size.
Atlas, length
«width over ant. eatsiles
‘ec oe “ce post. “ce =
trans. processes
“ “ “ce
MEASUREMENTS.
.0295 Atlas, dorso-ventral height
.034 Axis, length excl. odontoid .
-034 “ «incl. “ 0
.047 “width of anterior face .
.029
.027
.038
.030
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS.
Axis, width of posterior face
? Fifth cervical, length of centrum
fs width of anterior face
a « « — “ post. face
Median thoracic, length of centrum .
fs “width of ant. face .
The fore-limb is very incompletely represented in the collections
MEASUREMENTS.
.O15 ? Fourth lumbar, length of centrum .
.019 s «« ~_ width of post. face .
.O14 Last lumbar, length of centrum
.O16 Be " width of anterior face .
.020 . ss « “posterior face
.O16
the following measurements were taken from several individuals.
Humerus, distal width over trochlea
gf fs ss “ epicond.
Ulna, length of olecranon
“distal width .
“ «thickness
Radius, proximal width .
@ cS thickness
«distal width
MEASUREMENTS.
.O16 Radius, distal thickness
.024 Carpus, length in median line
.034 “ width
.009 Metacarpal II, proximal meen
.006 “ jh, :
.O16 f ff ss thickness .
-009 ss IV, length .
.017 tf “ proximal width
103
-027
.O21
.018
.O19
.O13
and
.006
.O175
.020
.006
.016
.O12
.O10
.004
The measurements of the hind-limb are taken from a single individual,
No. 15,719.
Femur, length from head
ss ss “ gr't trochanter
a6 proximal width
ss distal width
s «thickness over cond.
Tibia, length, excl. spine
«proximal width
«distal width
“ «thickness
Fibula, distal width
a «thickness
Calcaneum, length
Astragalus, length :
s width of trochlea
“ distal end
Ectocuneiform, length .
fs width
Metatarsal III, length .
ce “
MEASUREMENTS.
-I4I Metatarsal III, proximal width
.159 “ «proximal thickness
.039 a “distal width .
.034 ss IV, length .
.O41 a “proximal width
.143 Phalanx 1, digit III, length
.034 Gi, Sayopre, Wichdn
.O19 i SUR “thickness
.020 GC a, © & Ghictall yaichin
.008 «2, “ “ proximal width
.O13 Go G 8 eleteil within
.056 a 2, GH lisrayatin
.0285 on mwiclthotttocklea)
.O16 (2 cmmoteatestawidt ne
.O14 Phalanx 3, digit III, length Ce
.008 side) :
.O145 Pes, length in median ine
.083
.O17
.O17
.O17
.OII
.0025
-037
.O165
.O12
.O125
.0135
.0125
.025
.O14
.O16
.018
+193
Localities. — The type-specimen was found in the cliffs of the Rio Santa
Cruz and the numerous individuals brought home by Messrs. Hatcher &
104 PATAGONIAN EXPEDITIONS: PALAZSONTOLOGY.
Peterson were all obtained on or near the Atlantic coast ; at Coy Inlet,
five or ten miles south of that inlet; at Killik Aike on the Rio Gallegos
and two miles west of that point, and at Halliday’s Ranch, near North
Gallegos.
Ameghino has named several species upon very incomplete material,
which are listed below.
THOATHERIUM VELATUM Ameghino.
(Plate XIII, Figs. 3, 4.)
Thoathertum velatum Amegh.; Anales del Mus. Nac. de Buenos Aires,
SEE 4) 1, UN, jo Atos
Type, an incomplete cranium and isolated eth. Characterized by the
small size of the hypocone in m+ and ? and the absence of a distinct
posterior conule in all the upper molars. M+ has no hypocone and the
protocone is connected with the postero-external angle of the crown by a
curved crest. This species is somewhat larger than 7: mzenusculum, m*
measuring 15 mm. in antero-posterior by 17 mm. in transverse diameter,
and in m® these dimensions are 13 by 17 mm.
Locality. — Rio Santa Cruz.
THOATHERIUM KARAIKENSE Ameghino.
(Plate XIII, Fig. 6.)
Thoatherium karatkense Amegh.; Anales del Mus. Nac. de Buenos Aires,
Sem 2 If WO jos aug.
Type, a fragment of the left maxillary with m® in place. This species
differs from the preceding ones in the larger size of the hypocone, which
is present on m* as an isolated pillar, separated from the protocone and
the external wall. This tooth measures 13 mm. antero-posteriorly by 16
mm. transversely.
Locality. — Kar Aike.
THOATHERIUM BILOBATUM Ameghino.
(Plate XIII, Fig. 7.)
Thoathertum bilobatum Amegh.; Anales del Mus. Nac. de Buenos Aires,
Sym) 3, 10, NUL, 05 AUS).
Locality. — not given.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 105
MACRAUCHENIDA:.
The second family of Santa Cruz Litopterna is that of the Macrauchen-
idze, which differ markedly in almost all points of structure from the Pro-
terotheriidee, yet with such unmistakable fundamental similarity as to leave
no question as to the propriety of referring both families to the same order.
Aside from the little known and still problematical genus Aadzanthus,
the Santa Cruz representatives of the present family, so far discovered,
all belong to a single genus, 7%eosodon, which may be regarded, with
great probability, as directly ancestral to the Pampean genus MJacrau-
chenta. In what follows, except with regard to the dentition, no account
is taken of Adianthus, of which only the teeth are known, and the fact
that it was a small animal.
The species of 7eosodon are much larger animals than the contempo-
rary Proterotheriidz and of very different appearance and proportions.
In the present family there is no reduction in the number of teeth, the
formula being I3, Ci, Pz, M3, and there is no enlargement of incisors or
canines to form tusks. The first five teeth, from i1 to p1, inclusive, are a
series with simple, recurved, compressed-conical crowns, which have a
curiously reptilian, almost crocodilian appearance. The second and third
premolars are smaller and simpler than the molars, while the fourth upper
premolar is nearly, and the fourth lower quite, molariform. The pattern
of the upper molars is, at first sight, very different from that of the Protero-
theriidze, but a closer examination reveals the identity of plan. As in the
latter family, the brachyodont crown consists of two external, concave
crescents, and two more or less conical internal cusps, the peculiarity of
pattern arising from the development of accessory crests and ridges and
the great elevation of the cingulum at the antero-internal angle. In
moderately worn teeth two or three enamel lakes are characteristic. The
lower molars are very similar to those of the Proterotheriidze and are made
up of two crescents, in the posterior one of which is a very conspicuous
pillar, connected with the external wall by a spur. In Adzanthus this
element is absent.
The antemolars all have predecessors in the temporary series and the
milk-teeth, are, in general, like their permanent successors and only the
last deciduous premolar, in each jaw, has the molar pattern.
The skull is long and narrow, with slender brain-case and rather short
106 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
but quite prominent sagittal crest. The tympanic bone is very small,
scale-like and flattened, not forming a bulla, and with an irregular meatus,
which is not prolonged into a tube. The orbits are partially open behind
and the horizontal rami of the mandible are very slender. The especial
peculiarity of the skull is, however, to be found in the great reduction of
the nasals and elongation of the anterior nares, which indicate the
presence of at least an incipient proboscis.
The neck is very long, in striking contrast to the short neck of the Pro-
terotheriidz, yet the odontoid process of the axis retains its primitive,
peg-like shape. In no other ungulate with a neck of comparable length,
does the odontoid fail to assume the concave, spout-shaped form. All
the cervical vertebrae, except the atlas, are greatly elongated and much
resemble those of the camel and, as in the latter, the vertebrarterial canal
traverses the neural arch, except in the first and sixth vertebrze, in which
it still perforates the transverse process. Thus the shifting of the position
of the arterial canal is not so complete as it afterwards became in
Macrauchenia. The number of trunk-vertebree, though not yet known
with complete certainty, should very probably be stated as nineteen, 13-14
thoracics and 5-6 lumbars, another difference from the Proterotheriide,
in which the number can hardly have been less than twenty-one. As
in the latter family, the long, tapering sacrum is indicative of a very
short tail. The sternum is very peculiar; the presternum and anterior
segments of the mesosternum are long, very narrow and deep dorso-ven-
trally, while the hinder segments of the mesosternum are broad and
depressed.
The limbs are long and slender and the limb-segments are proportioned
differently from those of the Proterotheriidz ; the upper arm is short and
the fore-arm long, the thigh long and the leg short. The scapula is broad
and has a large acromion and very large metacromion, the latter about
midway in the course of the spine. The fore-arm bones are separate in
the Santa Cruz genus and the ulna is relatively heavy, the radius quite
slender. The long femur has a very large great trochanter and a well-
developed third trochanter, both of which are much more prominent in
the Santa Cruz than in the later representatives of the family. The leg-
bones, which have coalesced in Macrauchenia, are separate in 7heosodon
and the fibula is quite slender.
The feet are very different in appearance from those of the Protero-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 107
theriidae; the carpus has a similar semi-taxeopod arrangement, the peculiar
overlapping of the pyramidal upon the magnum seen in Macrauchenia
having not yet come about and the contact being still entirely lateral.
The metapodials are relatively longer and the phalanges shorter than in
the preceding family (except 7hoatherium), and the unguals are short,
broad and heavy, not in the least equine in character. The feet are tri-
dactyl and nearly isodactyl, the three digits being of nearly equal length
and thickness. The tarsus is closely similar to that of the Proterothe-
riidz, but the astragalus has a slightly more perissodactyl appearance in
the less convex and more depressed head.
In the Santa Cruz beds only two genera have been found which are
referable to the Macrauchenidz and one of these, 4adzanthus, may prove,
when better known, to be more properly assignable to a different family.
This Ameghino has already proposed (’94a, 27), but until the genus is
more completely understood, it seems an unnecessary complication.
I. Size of animal larger; lower molars with very conspicuous pillar and spur in
posterior crescent. Theosodon.
2. Animal very much smaller; lower molars without pillar or spur in either
crescent. Adianthus.
THEOSODON Ameghino.
(Plates XVI-XX.)
Theosodon Ameghino; Enumeracion sistematica, etc., 1887, p. 19.
? Pseudocelosoma Ameghino; Rev. Argent. de Hist. Nat., T. I, 1891, p.
204.
Oxyodontotherium Lydekker (von Amegh.); Anales del Mus. de La Plata,
I. ING WSR, jo O5;,
This genus which is the only well known Santa Cruz representative of
the family, is one of the commoner elements of the Santa Cruz fauna and is
quite fully represented in all the collections; it is thus now possible to
make out almost every detail of dental and skeletal structure. Through-
out, there is a close resemblance to the much later Pampean genus,
Macrauchenia, though, on the other hand, there are many important
modifications, especially of the skull, in the latter.
Dentition (Pls. XVII, figs. 1, 14, 3, 34, 4; XVIII, 1, 1@; XX, 1, 12).
—The dentition is complete and unreduced, having the formula, I$, Ct,
Ps, M3, = 44.
A. Upper Jaw. The incisors are arranged in an almost straight, antero-
108 PATAGONIAN EXPEDITIONS: PALA®ONTOLOGY.
posterior line and, though somewhat spaced apart, are yet inserted in an
imbricating manner; the two median incisors of the opposite sides are
separated by a wider space than any of the others. As already indicated
in the description of the family, the first five teeth, from i* to p* inclusive,
form a series of similar shape, but gradually increasing in size posteriorly.
The crowns are of compressed conical form, with trenchant edges and
acute points, and curve inward and slightly backward; the internal cin-
gulum is feebly developed near the anterior and posterior margins. The
canine differs from the incisors merely in being somewhat larger. Lydek-
ker states (’93, 66) that the upper canine has two roots, but this must
be merely an individual abnormality; in all of the numerous specimens
that I have examined, this tooth is single-rooted. My observations thus
agree with those of Ameghino (’940, 281).
The first premolar is isolated by very short diastemata in front of and
behind it and is implanted by a single, heavy root; it resembles the
canine in form, but is decidedly larger, especially in antero-posterior |
diameter, and has a complete internal cingulum. I have seen no per-
fectly unworn examples of p® and 2, but in the former the composition of
the crown is plain, even in much worn specimens of the tooth; it consists
of a single outer lobe, with pointed, cordate external face and a distinct
external cingulum, and a single, crescentic inner lobe, which appears to
be merely a greatly developed and complete internal cingulum; at all
events, no other internal cingulum is present. The tooth is inserted by
two massive roots. Premolar # is larger than p*, but, so far as can be
judged from the much worn teeth at my disposal, the crown is composed
of the same elements, although the inner crescent is not so regularly
developed, being enlarged and broadened at the postero-internal angle,
thus giving a more asymmetrical shape to the crown. On the other hand,
the fourth premolar is almost molariform; it has two external, crescentic
lobes, which are concave outward, but differs from the molars in having
only a single principal internal cusp, the deuterocone. The anterior conule
is represented by a ridge, which extends from the deuterocone to the
antero-external angle of the crown. In perfectly unworn teeth, this ridge
rises to an acute point, separated by a cleft from the deuterocone, but this
cleft is obliterated in an early stage of wear and then the ridge appears to
be a direct outgrowth from the deuterocone. In front of and behind the
deuterocone, the cingulum is much elevated and encloses two large,
SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. 109
enamel-lined fossettes, which, in the process of attrition, long remain as
enamel lakes. In advanced stages of wear, this tooth appears to have
quite the crown-pattern of a molar, though in unworn teeth the difference
is sufficiently obvious.
The molars are highly characteristic and form a rather short series; m+
and # are of nearly the same size, the former being, in some cases, slightly
wider transversely and shorter antero-posteriorly, though in others, m= is
a little the larger in both dimensions, while, in all cases, m® is consider-
ably the smallest of the series. The molar-pattern consists of two outer
crescents, which are quite deeply concave externally and meet in a promi-
nent median external pillar, or mesostyle; and, further, there are two
small, conical, inner cusps, which are separated internally by a deep fissure,
or narrow valley, but are confluent on their outer margins (z. e., toward
the external side of the crown). Intermediate conules are present; the
anterior one, as in p*, is a ridge, rising to an acute point, which is demar-
cated from the antero-internal cusp (protocone) by a cleft (z. e¢., in quite
unworn teeth), while the posterior conule is a ridge, sloping uninterruptedly
outward and backward from the postero-internal cusp (hypocone). A
spur of enamel extends from the hypocone transversely to the outer wall
of the crown, dividing the longitudinal valley into two fossettes, and in
some individuals, another spur projects from the postero-external cusp
into the posterior fossette, but this is a very variable feature. A third
fossette is enclosed between the much elevated anterior cingulum and the
protocone and anterior conule, and, in certain cases, a fourth and much
smaller fossette is formed between the two internal cusps and the internal
cingulum. This cingulum is, however, subject to great variation, and may
differ in degree of development on the opposite sides of the same indi-
vidual. In most of the skulls the internal cingulum is entirely absent
between the two internal cusps (proto- and hypocones) and, when present,
it may be a separate pillar, or a ridge connecting the two cusps and com-
pletely enclosing a fossette, or it may be attached to one cusp and not to
the other, making an imperfect fossette, which opens inward by a narrow
fissure (see Pl. XVII, figs. 3, 3a). Always this cingulum, when present,
appears to be confined to m* and *; I have seen no instance of its develop-
ment in m8. Variable as it is, this character can hardly have the generic
significance which Ameghino attributes to it.
The third upper molar is distinctly smaller than m* or *, the reduction
110 PATAGONIAN EXPEDITIONS: PALAZSONTOLOGY.
chiefly affecting the posterior half of the crown. The postero-external
cusp is much smaller than the antero-external and is no longer in the
same fore-and-aft plane with it, but is so inclined as to present backward
rather than outward.
The roots of all the upper molars are peculiar ; there are two external
roots of the usual character, and one very large internal root, which is
laterally compressed, but extends through the whole antero-posterior
length of the crown, and shows distinct indications of being formed by
the coalescence of two separate roots, of which the anterior is much the
larger. The coalescence is by means of a thin sheet of dentine and cement,
the two nerve-canals remaining separate.
In partially worn examples of the upper molars the various elements
of the crown-pattern can no longer be distinguished; the longitudinal
valley and the anterior and posterior fossettes remain as enamel lakes.
In more advanced stages of attrition the anterior part of the valley is worn
away and only two lakes are left, except in those cases in which a third
small lake is enclosed between the two internal cusps and the cingulum.
In very old individuals, of course, the lakes and all other elements disap-
pear, with the exception of the surrounding wall of enamel.
B. Lower Jaw. The lower teeth have somewhat less complex patterns
than the upper. The first seven teeth, from iz to pz inclusive, form a Series
of similar shape, increasing gradually in size and complexity backward.
The incisors are simple, compressed conical teeth, with crowns which
resemble those of the upper jaw in shape, but are somewhat lower and
broader and have a better developed internal cingulum. The median
incisors of the two halves of the mandible are almost in contact and bite
between the two corresponding upper teeth. The first and second incisors,
and sometimes the third also, are so inserted in the jaw that their principal
diameter is transverse. The canine is like the incisors, except in being
larger.
The first lower premolar may be described as an enlarged canine, and
is single-rooted ; pz, which is inserted by two roots, is still of the same
general form, though of larger size, and has amuch more prominent inter-
nal cingulum, which encloses small anterior and posterior basal fossettes.
The third premolar is much more elongated antero-posteriorly than pz
and shows the beginning of the bicrescentic pattern. Externally the crown
has but a single, undivided cusp, but on the inner side, a prominent
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. III
vertical ridge, or incipient deuteroconid, divides the surface into two
shallow concavities. The cingulum, both internally and externally, is
more prominent than in pz. The fourth premolar is quite molariform, and
is composed of two crescents, but there is no pillar or spur in the internal
concavity of the posterior crescent, and the internal cingulum opposite the
openings of the crescents is better developed.
The lower molars form a series nearly equalling in antero-posterior
length the premolar series, mz is the largest and mz the smallest of the
three. All have the same crown-pattern, with two antero-posteriorly
directed crescents, opening inward; in the inner opening of the posterior
crescent is a conspicuous spur, which, in perfectly unworn teeth, is seen to
be a vertical pillar, connected with the external wall by an obscurely ser-
rate ridge, above the level of which the unabraded apex of the pillar rises.
In such teeth, it may be plainly seen that the forward crescent is shorter
antero-posteriorly and more elevated dorso-ventrally than the hinder one,
though the difference in height is speedily obliterated by wear.
Milk Dentition (Pls. XVII, figs., 3, 3a; XVIII, 1, ta). — The tempo-
rary teeth differ but little inform from their permanent successors and are
32 in number; the formula is: Di, Dct, Dpi, all of them being changed.
A. Upper Jaw. The deciduous incisors are much smaller than the
permanent ones, with crowns which are lower vertically, but relatively
more elongate antero-posteriorly than the latter and acutely pointed. The
canine is of the same shape as the incisors, but larger. The first milk-
premolar is an enlarged canine in form, but differs from its permanent
successor in having two roots, which demontstrates that all of the teeth
of the temporary series are shed and replaced. The second milk-pre-
molar differs somewhat in form in different species. In 7: lalemanii it
is considerably smaller than p, though of similar pattern, and has a single
internal crescent, formed by the elevated cingulum ; in 7: 4ydekkerz it is
more like p* in form and has two internal crescents, of which the posterior
is very large, and a prominent posterior style appears at the postero-
external angle of the crown, an element which is rarely found in either p*
or * of the permanent series. The third milk-premolar is larger than dp
especially in transverse width, and differs from its permanent successor
chiefly in the presence of a very conspicuous posterior and a smaller
anterior style on the external face. The fourth milk-premolar is more
completely molariform than p*, in having two well-defined internal cusps
112 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
(deutero- and tetartocones), but the external median rib, or style, is less
prominent than in the true molars.
B. Lower Jaw. The lower milk-teeth are more closely set than the
corresponding permanent ones and the first six form an imbricating series,
the hinder edge of each tooth overlapping the one behind it; these teeth
all increase in size and complexity toward the posterior end of the series.
The milk-incisors and canines are lower, but relatively much more extended
antero-posteriorly than their permanent successors; each has on its in-
ternal face a low, median, vertical ridge, which becomes more prominent
on each succeeding tooth and is most conspicuous on dpz and =.
Lydekker (’93, 68) states that in the mandible of young individuals of
T. lydekkeri the alveoli of the incisors are directed forward almost hori-
zontally. Iam quite at a loss to understand this statement, for I have
seen nothing in the milk or permanent dentition which could justify, or
even suggest, such a description. On the contrary, in all of the individ-
uals examined by me the incisors, whether temporary or permanent, are
quite erect and show no tendency to become procumbent, and Ameghino
(946, 283) reports the same conclusion. I can only suppose that Mr.
Lydekker has had before him a specimen deformed by crushing, or pos-
sibly an abnormal individual
All of the milk-premolars are implanted by two roots; the third is im-
perfectly molariform, having two crescents and, in addition to the pillar
on the inner side of the posterior crescent which the molars also have, there
isa similar, though smaller, pillar in the concavity of the anterior crescent.
The fourth milk-premolar is indistinguishable from one of the permanent
molars, except for the presence of the pillar in the anterior crescent.
The specimens at my disposal show little regarding the manner in
which the teeth succeed one another. The first molar in both jaws is in
function before any of the milk-teeth have been shed; the second molar
is in process of eruption at the same time and was probably in use before
any of the second series. In one individual with milk-dentition still com-
plete, the fully formed, but as yet rootless, crown of p* is nearly ready to
displace dp*, and it therefore seems likely that that tooth is the first of
the second series to erupt.
If we compare with the dentition of 7/eosodon that of Macrauchenia
patachonica, from the upper Pampean beds, the latest and most special-
ized member of the family, we observe that the changes are surprisingly
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 113
few and small inamount. In JZ patachonica, the upper incisors are no
longer arranged in an antero-posterior line, but form a transverse series,
and have become relatively smaller and more chisel-shaped. In both
jaws, the incisors have an enamel pit, or ‘‘ mark,” somewhat resembling
that of the horses, and formed by the great growth of the internal cingu-
lum, which is in a merely incipient stage in 7/eosodon. Bravard’s figures
(Burmeister, 64, Pl. I, figs. 2, 3) appear to show that the upper canine
was two-rooted. The premolars are little or not at all more complex than
in Zheosodon. The upper molars are not quite so strictly brachyodont
as in the Santa Cruz genus; the external crescents are more angular and
more deeply concave, and the grinding surface is somewhat more com-
plicated, with three or more enamel lakes in the moderately worn stage,
but the change from 7/eosodon is not great. The lower molars are sim-
plified by the suppression of the pillar in the posterior crescent, but
Ameghino states that it is present in the milk-teeth (944, 279).
Skull (Pl. XVII, figs. 1, 1a, 16).—The skull of Zeosodon is extremely
interesting and peculiar and differs much more from that of Macrauchenia
than would be expected from a comparison of the teeth alone. As in all
the other known genera of this family, the skull of 7Zeosodon is long, narrow
and low, but the dorso-ventral shallowness is, in most specimens, exag-
gerated by the vertical crushing and distortion to which the skull has been
subjected. It is rare to find an individual which has suffered neither
lateral nor vertical distortion. Both cranium and face are elongate, the
anterior margin of the orbit, which is above the middle of m®*, forming
nearly the median point in the total length of the skull. The upper profile
of the skull rises but little from the occipital crest to the parietal eminence
and thence descends very slightly and gradually to the end of the nasals,
from which point it slopes down very rapidly to the low rostrum. In
Macrauchenia, the parietal eminence is higher and farther forward and
from it the upper profile descends in an almost uninterrupted slope to the
end of the rostrum, the minute, vestigial nasals forming the only break in
’ the line.
The occiput is quite high and narrow, broadest at the base and rapidly
contracting dorsally; above the foramen magnum, the surface is strongly
convex transversely; the foramen itself is quite large and of nearly circular
shape. The occipital crest is low and thin and passes uninterruptedly into
the dorsal border of the zygomatic process of the squamosal, thus com-
pletely defining the temporal fossa behind.
It4 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
All the available specimens are either of such old individuals, or have
suffered so much from crushing, that it is exceedingly difficult to make out
the various bones of the skull, and some I have not been able to determine
at all. The basioccipital is moderately elongate, broad and with a ventral
keel, the prominence of which varies in different individuals, becoming
higher with age: on each side of the bone is a conspicuous pit, or rugosity,
for the attachment of the vectus capif7s muscle. Even in very young skulls,
the basi- and exoccipitals are indistinguishably fused together, without
any trace of a suture. The exoccipitals are low, broad, extremely thick
and massive, and so dense that the cancellous structure is not immediately
obvious; the paroccipital processes are very conspicuous and of moderate
length, descending below the level of the condyles, and are broad and
antero-posteriorly compressed, with convex anterior, and concave posterior
surface. The condyles are quite large and the articular surface of each is
prolonged forward upon the basioccipital in much the same way as in
Macrauchenia. Large condylar foramina perforate the basioccipital later-
ally and are entirely concealed by the overhanging condyles, when the
skull is viewed from below. The supraoccipital is a small, but very thick
and heavy bone, massive and dense and without a sinus.
The basisphenoid is broad and heavy, contracting forward. The limits
of the ali- and orbitosphenoids in the cranial wall cannot be definitely
made out in any of the specimens at my disposal. The parietals are very
large and form the greater part of the brain-case, which is narrow and
of no great capacity. Anteriorly, the parietals are deeply emarginated in
the median line, to receive the broad posterior processes of the frontals.
The sagittal crest is broad anteriorly, contracting posteriorly to a thin
ridge, the length and height of which are variable, though in general they
may be said to increase with age. There are also marked specific differ-
ences in the development of the sagittal crest, as, for example, between
T: lallemanti and T. garrettorum.
The squamosal is long and low, not rising much upon the side of the
cranium, most of which is formed by the parietal ; the posttympanic process -
is short and inconspicuous and is closely applied to the mastoid. The
zygomatic process is quite long, extending forward to form a small portion
of the lower margin of the orbit, but has no trace of a postorbital process ;
it is slender and laterally compressed, and arches out but little from the
side of the cranium ; the proximal portion, or root, of the process is much
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. II5
extended antero-posteriorly, forming abroad shelf. The glenoid cavity is
a large, almost circular depression, concave in both directions. The post-
glenoid process is rather short, but broad and heavy.
The tympanic is very loosely attached to the skull and, in most cases,
has been lost; it is very small and can hardly be said to form a bulla at
all, being little more than a flat, scale-like bone, with a large, irregular
auditory meatus, which is a mere hole and has no tubular prolongation.
The large periotic, which is concealed by the tympanic, is very dense
and antero-posteriorly elongated, laterally compressed, with convex
external, and nearly flat mesial surface. A small triangular area of the
mastoid portion is exposed on the surface of the cranium between the
exoccipital and squamosal.
The jugal is long, slender and laterally compressed ; posteriorly, it
extends almost to the glenoid cavity, and anteriorly, it articulates with
the lachrymal, thus forming nearly the whole lower margin of the orbit.
As a whole, the zygomatic arch is thin and weak, but relatively consider-
ably longer than in Wacrauchenza and the temporal opening is correspond-
ingly elongate, though actually quite small. It is true that Ameghino’s
figure ('94a@, 29, fig. 6) appears to show very long temporal openings, but,
in all probability, this is merely an appearance, due to the fact that the
matrix has not been removed from the root of the zygomatic processes.
As is shown in Plate XVII, fig. 10, the root of this process is much
extended antero-posteriorly, reducing the size of the temporal opening.
The lachrymal is rather small, and has but a moderate facial expansion ;
the foramen is single and is placed on the margin of the orbit, and the
lachrymal spine is a low tubercle.
The frontals are very large, especially in transverse width, and form a
broad forehead, which, in undistorted specimens, is strongly convex trans-
versely and indicates the presence of large frontal sinuses. The postorbital
processes are long and slender, with rugose margins and so curved as to
be concave anteriorly and convex posteriorly; they do not quite reach the
jugals and thus leave the orbits partly open behind. The supraorbital
margin is rough and tuberculated and is perforated by a large foramen,
which opens downward into the orbit, and, in addition, there is on each
side a large vascular opening, nearly midway between the sagittal suture
and the orbital margin. Anteriorly, the frontals send forward between
the nasals a pair of median processes, the size of which varies much in the
116 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
different species. In 7. garrettorum these processes are broad and con-
spicuous and widely separate the nasals, while in 7: /allemanti (lydekkere),
as figured by Ameghino (/oc. czt.), they are very much reduced.
The surface of the frontals is quite smooth and there is no indication of
the deep median depression, with pits and ridges for the insertion of the
muscles of the proboscis, which is so very conspicuous a feature in the
skull of Aacrauchenza.
The nasals are greatly reduced and very short, though much larger than
the vestigial remnants seen in the Pampean genus; they are strongly
curved transversely and almost semicylindrical, with dorsal and lateral
faces. According to Ameghino’s figure (/oc. cit), in 7. /allemantz, the
nasal processes of the frontals are short and narrow and the nasals them-
selves are in contact for nearly their entire length. In 7. garrettorum,
on the contrary, the very large processes so separate the nasals, that they
do not touch each other at any point. The great shortening of the nasals
is an indication that some sort of a proboscis, or prehensile upper lip,
must have been present in the living animal, while the absence of any
special area for muscular attachments shows that the proboscis cannot
have attained any such development as it had in Macrauchenia. ‘The
anterior narial opening is very long and narrow, differing much in shape
and position from that seen in the Pampean genus. As a whole, the
Opening is much more anterior in position than in the latter and extends
forward between the maxillaries for their entire length and even slightly
invades the premaxillaries, and posteriorly, it terminates in front of the
orbits, which themselves occupy a more anterior position than in
Macrauchenia.
The maxillaries are very elongate and immediately in front of the orbits,
where they articulate with the nasals, they have considerable dorso-ven-
tral height, but from the end of the nasal suture this height diminishes
rapidly and the anterior portion of the maxillaries is very low. Except
in the palatal region, the two maxillaries are nowhere in contact, being
separated for their entire length by the anterior nares. The infraor-
bital canal, which is rather small, opens above m*. The premaxillaries
are relatively elongate and very low dorso-ventrally, and are not distin-
guished into alveolar and ascending rami. They are broad, depressed
and flattened, slightly convex on the dorsal surface and overlapping the
maxillaries behind. For most of their length, the two bones are in contact,
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 117
diverging somewhat posteriorly and enclosing the front end of the narial
opening. Even in the oldest individuals, they display no tendency to
coéssify.
The bones of the hard palate are exceedingly thin and fragile and in
none of the specimens at my disposal are they in a satisfactory state
of preservation. Apparently, there are no incisive foramina, but merely
grooves in the position occupied normally by those foramina. In 7. gracilis
Ameghino (944, 32, fig. 9) figures very long, narrow foramina, separated
by a slender spine, but it seems likely that, in this instance, the draughts-
man was deceived by grooves filled with matrix. Lydekker’s figure (93,
XXVI, 2) would appear to be open to either interpretation. If, however,
no error be involved in Ameghino’s figure, the presence of the incisive
foramina would sharply distinguish 7: gvacz/s from the other species.
The maxillary part of the palate is of nearly uniform width between the
two parallel rows of teeth, broadening slightly in the anterior premolar
region. Shallow grooves run near the outer margins of the maxillary
palatine processes for nearly their entire length. At the anterior end of
these processes, as may be seen in Plate XVII, fig. 1@, is a median open-
ing, continuing forward as the premaxillary grooves already mentioned.
Probably this opening served to transmit the blood-vessels and nerves which
ordinarily pass through the incisive foramina, but so distorted is this region
in even the best-preserved skulls, that I cannot feel entirely confident of
this interpretation.
The palatines very early coalesce with the maxillaries and, even in
young animals retaining all of the milk-teeth, their limits are difficult of
determination. Apparently, however, they form a moderate portion of
the hard palate, with antero-posterior extent about equal to that of a molar
tooth ; the posterior palatine foramina, so far as can be judged from the
imperfect material, are entirely within the limits of the maxillaries. The
posterior nares are long, narrow and low, with nearly parallel walls; the
front border is on a line with the middle of m?, while posteriorly the walls
arise opposite the middle of the glenoid cavities. The pterygoids termi-
nate in low, inconspicuous hamular processes, and the fosse are mere
grooves. The vomer is strongly developed and divides the forward part
of the posterior nares into two openings.
Like so many other features of these more or less crushed and distorted
skulls, the cranial foramina are difficult to determine satisfactorily. So
118 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
far as they can be made out, they differin no important respect from those
of the other Santa Cruz family of the Litopterna, the Proterotheriidz.
The optic foramen is a large opening, situated low down upon the side of
the cranium and behind the orbit. Below and a little behind the optic
foramen, is the foramen lacerum anterius, also a large opening, especially
in the dorso-ventral diameter, but quite narrow and slit-like transversely.
There is no alisphenoid canal, and the foramina rotundum and ovale appear
to be confluent, a single large aperture perforating the alisphenoid inter-
nal to the glenoid cavity. A large,irregular opening in front of the tym-
panic doubtless includes both the eustachian canal and the foramen
lacerum medium. The foramen lacerum posterius is much smaller and
no carotid canal is discoverable. The postglenoid and stylo-mastoid
foramina are deep-set, but large and conspicuous. As already mentioned,
the condylar foramina perforate the basioccipital in a horizontal direction
and are concealed, in ventral view, by the overhanging condyles.
In the adult animal, the two halves of the lower jaw are indistinguish-
ably fused together at the symphysis, a coalescence which takes place at
quite an early period. The horizontal ramus is very low and shallow
dorso-ventrally, but quite thick and stout transversely; the ascending
ramus is broad, but, aside from the coronoid, is not very high and the
condyle is raised but moderately above the level of the teeth. The angle
projects much posteriorly, and its free border is rounded and somewhat
incurved; the masseteric fossa is large but very obscurely defined. The
condyle, which is almost sessile, is moderately convex; on the hinder face
of the internal half is an articular surface for the postglenoid process of the
squamosal. The sigmoid notch is very narrow and the coronoid process
is very high, slender and somewhat recurved; in the very young animal
the shape of the coronoid suggests that of the camel. The lineze obliquze
are very prominent and enclose quite a deep fossa, or depression, behind
the last molar. The inferior dental foramen is very large and there are
usually three mental foramina, beneath the canine and the first and second
premolars respectively.
Of the hyoid apparatus (Pl. XVII, figs. 1a, 2), two elements are pre-
served ; one is the relatively long, slender, cylindrical and outwardly
curved tympanohyal, which is not attached to the very small tympanic
bone, but to the posttympanic process of the squamosal. The other
element is the stylohyal (fig. 2), which has some resemblance to that of
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. lime)
the horse; this is long, slender, much compressed laterally and tapering
distally; the proximal end is expanded in the antero-posterior direction,
forming a large, thin, bony plate. Though chiefly posterior, this expansion
is less exclusively so than in the horse. °
The skull of Macrauchenia patachonica is manifestly of the same type as
that of ZZeosodon, but has undergone extensive modifications, chiefly in
response to the development of the proboscis. ‘The face has become rela-
tively more elongate, owing to the shifting of the orbits, which are now
behind the dental series and are completely encircled in bone. In corre-
lation with this shifting of the orbits, the zygomatic arches are shortened
and the temporal openings reduced in size. The cranium is shorter and
more rounded and the sagittal crest is replaced by a broad sagittal area.
The premaxillee are shorter and broader and are thoroughly fused together
in the median line, as are also the maxillaries for the greater part of their
length, thus forming a long, solid rostrum. The anterior narial opening
is greatly reduced in length and shifted backward between the orbits and
vertically above the posterior nares. Behind the superior narial opening,
there is a deep depression of the frontals, at the bottom of which are con-
spicuous pits and ridges for the attachment of the muscles of the proboscis.
As Ameghino has demonstrated ('946, 277 ff.) several genera of the
family, of intermediate geological dates, form a series of gradations in
dentition and skull structure between 7%eosodon and Macrauchenia. Of
these the most important are MJesorhinus and Scalabrinithercum. The
former, unfortunately still very incompletely known, has the premaxillaries
ankylosed and part of the maxillaries also; behind this symphysis is a
groove, which widens and deepens posteriorly and leads back to the ante-
rior nasal opening, which begins much farther back than in 7Zeosodon and
not so far as in Scalabrinitheritum. In thelatter genus the approximation
to Macrauchenia is still more marked; the orbits have shifted backward,
bringing the anterior rim over m*; the nasals are much reduced, though
still considerably longer than in the Pampean genus. The anterior nares
have been displaced backward, though notso far as in Macrauchenza, and
there is as yet no depression of the frontals for muscular attachments. The
upper molars have a somewhat more complex pattern than in 7heosodon,
a change which principally consists in the deepening of the external
crescents and in the development of the antero-internal cingulum into a
more independent crest.
120 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
Vertebral Column, Ribs and Sternum. —In one individual, the type of
T. garrettorum (No. 15,164) the vertebral column appears to be complete
to the end of the sacrum and gives the formula: C.7, Th.13, L.6, S.7.
This is a surprise in view of the widely held opinion that Macrauchenta
had the perissodactyl formula of 23 trunk-vertebre, and, at first sight, this
would seem to militate strongly against the derivation of the Pampean
genus from Z%eosodon. It is, however, very doubtful whether acrau-
chenta actually possessed so large a number of trunk-vertebre. Bur-
meister, it is true, definitely states ('91, 483) that in the La Plata Museum
skeleton the number of thoracic vertebrz is 18 and of lumbar vertebrz 5,
but there is some inexplicable mistake involved in the statement, as the
La Plata skeleton is much less complete than Burmeister seems to have
supposed. In fact, that skeleton, which Lydekker has figured (96, 76,
fig. 10) makes it very probable that the number of trunk-vertebree could
not have exceeded 19 or 20. On the other hand, it is not altogether
certain that the number 19 attributed to 7/eosodon is correct, for the speci-
men above referred to (No. 15,164) was not found with all the bones in
their natural connections and it is possible that some of the vertebrze are
missing. Still, the vertebrae, when put together, seem to form a complete
series without breaks.
In Zheosodon the neck is very long and its proportions have much
resemblance to those seen in the llama. The atlas (Pl. XVIII, fig. 2)
is quite elongate in proportion to its width, though very much shorter
than the succeeding cervicals, and has a large, subcircular neural canal.
The anterior cotyles for the occipital condyles are large, widely separated
dorsally, where the neural arch is quite deeply emarginated between them ;
ventrally, the cotyles are much more closely approximated. The poste-
rior cotyles for the axis are small and nearly plane, while the facet for the
odontoid is quite deeply concave transversely and is not confluent with
the posterior cotyles. The neural arch is broad in both directions and
moderately curved; the spine is a very low ridge, the height of which
varies somewhat in different individuals. The inferior arch is quite nar-
row antero-posteriorly and has but a very small hypapophysis, or none at
all. The transverse processes are very short, with regularly curved free’
border; anteriorly, they do not reach the outer wall of the cotyles but are
notched and posteriorly, the cotyles also project behind them. At the
base, the transverse processes are perforated by the vertebrarterial canal,
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 121
the posterior opening of which is small, while the anterior opening is
much larger. The only other foramina present are those in the neural
arch for the spinal nerves.
Compared with the atlas of 7zeosodon, that of Macrauchenia shows the
following differences: (1) As a whole, the atlas of the Pampean genus is
shorter, broader and more depressed, and the neural canal is much smaller,
while the neural spine and hypapophysis are much better developed. (2)
The anterior cotyles are more closely approximated, both dorsally and
ventrally, and their mesial ventral portions emarginate the inferior arch in
a characteristic way, not seen in 7/eosodon. (3) The transverse pro-
cesses are much longer, thicker dorso-ventrally, and decidedly recurved, pro-
jecting behind the posterior cotyles; anteriorly, the processes extend the
full length of the atlas, converting the atlanteo-diapophysial notches into
foramina for the inferior branches of the spinal nerves. (4) The trans-
verse processes are not perforated by the canals for the vertebral arteries.
The axis (Pl. XVIII, figs. 3, 3@) is extremely elongate. Anteriorly,
the centrum is much broadened by the articular surfaces for the atlas,
which are slightly convex in both directions and are somewhat inclined,
sloping dorsally and backward, so that when the atlas and axis are put
together, the two bones form a distinct angle. Dorso-ventrally, the dia-
meter of the cotyles is greater than transversely. Deep sulci separate the
cotyles from the odontoid and, internal to each one, is a conspicuous vas-
cular foramen. The odontoid process is moderately elongate, peg-like
and somewhat depressed, with a facet for the atlas on the ventral side.
It is very exceptional to find an ungulate animal with very long neck,
in which the odontoid process retains its primitive, peg-like shape. In
all other known instances, except the present family, the long neck is
associated with a spout-shape of the odontoid, and in many groups, such
as the horses and camels, the transformation of the odontoid keeps pace
with the elongation of the neck. This is another example of the curiously
primitive features which, in the Litopterna, so frequently persist despite a
high degree of specialization.
The centrum of the axis narrows much to the middle, expanding again
to the posterior face, which is decidedly opisthoccelous. On the ventral
side of the centrum is a keel, which divides posteriorly into two quite
prominent ridges. The neural arch is high and narrow in front, wider
behind; the spine is long antero-posteriorly, rather low and plate-like,
122 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
projecting anteriorly over the base of the odontoid and terminating behind
in a stout rod, which extends well behind the postzygapophyses. The
latter structures are narrow, but project far behind the centrum, so that
they are visible for their full extent when the vertebra is viewed from the
ventral side. The transverse processes are short, slender and imperforate.
The anterior opening of the vertebrarterial canal is large and pierces the
base of the neural arch in front of the transverse process. From this
point the canal runs diagonally upward and backward through the side of
the neural arch and opens posteriorly into the neural canal.
In Macrauchenia the axis differs from that of 7Zeosodon in the follow-
ing respects: (1) The centrum is broader and less constricted in the mid-
dle. (2) The odontoid process is shorter. (3) The neural spine is higher
dorso-ventrally and projects farther in front, not so far behind. (4) The
anterior opening of the canal for the vertebral artery is smaller and placed
higher up on the pedicel of the neural arch.
The third cervical is very long and has a centrum which, aside from the
anterior cotyles, is very like that of the axis, with a constriction in the
middle and broad, depressed faces; the ventral keel, as in the axis, divides
posteriorly into two divergent ridges. The neural canal is small and the
zygapophyses are long and narrow, projecting well in front of and behind
the centrum. The neural spine is a long ridge, with straight and nearly
horizontal border; anteriorly, the spine is quite high, posteriorly, the
neural arch rises so as to reduce the height of the spine, which dies away
upon the arch in front of the postzygapophyses. The anterior opening of
the vertebrarterial canal is at the base of the pedicel of the neural arch,
the remainder of the canal being concealed within the arch. The trans-
verse processes are short, but much extended in the antero-posterior direc-
tion; each is divided into two portions, a smaller anterior part, which
projects in front of the centrum, and a larger posterior part. Both parts
have a horizontal direction and lie in nearly the same fore-and-aft plane.
The fourth cervical differs from the third in several respects. The
centrum is less depressed and its faces have more nearly equal transverse
and dorso-ventral diameters. The neural spine is much less extended
antero-posteriorly, but nothing can be determined as to its height, since it
is broken in all of the available specimens; the zygapophyses are some-
what larger and the canal for the vertebral artery has a similar position.
On the other hand, the transverse processes are quite different; the ante-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 123
rior portion is bent downward, making the broad side present laterally,
somewhat as in the camel. This anterior portion is connected with the
centrum by a comparatively narrow neck and becomes much broader
antero-posteriorly on the ventral side. The hinder portion of the process
is much more extended from before backward than the forward portion, is
horizontal in direction and has a more elevated position, arising from the
centrum a little below the base of the neural arch.
In Macrauchenza, this vertebra has a broader, heavier and more depressed
centrum than in 7/eosodon, with faintly marked ventral keel, which does
not divide into divergent ridges. The anterior portion of the transverse
process is shorter from before backward, not projecting so far in front of
the centrum, has a much more thickened and rugose free border, and is
not constricted at the junction with the centrum.
In Zheosodon, the fifth cervical (Pl. XVIII, figs. 4, 4a) differs so little
from the fourth as hardly to require aseparate description. It is large and
heavy, has a neural spine which is low and shorter from before backward
and the anterior portion of the transverse process joins the centrum by its
full breadth, without constriction.
The sixth cervical is much shorter than any of the preceding vertebrze,
except the atlas, and the centrum is so curved that the ventral face is con-
cave antero-posteriorly, and has a very low and thin, but very distinct
median keel. The broad neural arch encloses quite a large neural canal,
and the spine has a forward inclination. The transverse processes are, as
usual in the Mammalia, divided into diapophysial and pleurapophysial
elements; the former is a short, broad plate, extending horizontally out-
ward from the sides of the centrum, with thick and rugose free border,
and, as in mammals generally, is perforated by the canal for the vertebral
artery. The pleurapophysis, or inferior lamella, is very large and promi-
nent, extends along the whole length of the centrum and is directed almost
downward, with thickened ventral border.
In Macrauchenia, this vertebra is of a similar type to that just described,
but differs ina number of details. (1) Thecentrum is considerably shorter
in proportion to the length of the fourth cervical, as well as broader and
more depressed. (2) The neural canal is smaller and the zygapophyses,
especially the posterior pair, are much more strongly divergent from each
other. (3) The diapophysis is thicker dorso-ventrally and is not perforated
by the vertebrarterial canal, while the inferior lamella is less prominent
124 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
and less vertical, having a more outward inclination, so that, when seen
from below, the lamellz of the two sides are more divergent.
The seventh cervical of Zeosodon is much shorter than the sixth and
has a broader and more depressed centrum, especially behind, where the
width is increased by the large rib-facets ; the ventral keel is quite promi-
nent and much thicker than on the sixth vertebra, with a rough tubercle
at the anterior end. On the dorsal side of the centrum, forming the floor
of the neural canal, is a wedge-shaped prominence from each end, with a
depression on each side of it; the two wedges do not meet in the middle
of the centrum and the concavities are connected between the apices of
the wedges. The neural canal is large, but the neural arch is quite narrow
and slender, being greatly reduced by the deep notches between each pair
of zygapophyses, which are more widely separated and the posterior pair
more strongly divergent than in any of the other cervicals. The trans-
verse processes are quite broad and depressed ; their full length is not
shown in any of the specimens, but was probably not great. A minute
canal pierces the base of the transverse process and may have transmitted
a branch of the vertebral artery, but is far too small tohave contained the
main trunk of that artery.
The number of trunk-vertebrz is not as yet determined beyond all
question, but, as we have already seen, was very probably 19, and their
division into regions varies slightly, as it does in existing mammals; the
thoracic vertebrae may be either 13 or 14, and the lumbars 6 or 5.
Curiously enough, the first thoracic vertebra (Pls. XVII, fig.5; XVIII,
6) is remarkably like a cervical in appearance, and especially the seventh
of that series, from which it differs principally in the presence of an addi-
tional pair of facets for the heads of the second ribs and of facets for the
tubercles of the first pair on the transverse processes. So, there can be
no question as to the place of this exceptional vertebra in the series. The
centrum is shorter than that of the last cervical, with narrow anterior and
broader posterior face, and much less distinct ventral keel. On the dorsal
side of the centrum are wedge-shaped prominences which are like those
of the seventh vertebra, but are more nearly in contact at their apices.
The anterior rib-facets are very large, the posterior smaller and more con-
cave. The neural canal is large and the arch narrow, though broader
than that of the last cervical. Although the neural spine is broken in all
of the specimens, it obviously was short and slender and had a decided
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 125
forward inclination, in very marked contrast to the spines of the succeed-
ing vertebra. The zygapophyses are of altogether cervical type, but those
of the posterior pair are less strongly divergent than in the seventh cer-
vical. The transverse processes also are very much as in the latter verte-
bra, but are not quite so broad antero-posteriorly and are thicker dorso-
ventrally, especially at the distal end, where they are very heavy and
rugose. On the ventral side of each process is an oval, concave facet for
the tubercle of the first rib.
Functionally, the first thoracic is, to a certain extent, a part of the very
elongate neck, not so much adding to its length, as increasing its flexi-
bility and ease of movement.
The second thoracic resembles the first of most ungulates. The cen-
trum is of a shape similar to that of the preceding vertebra, but is smaller,
and the wedge-shaped prominences on the dorsal side have coalesced into
a low, rounded ridge; the facets for the rib-heads are very large and the
anterior and posterior pairs are quite closely approximated. The trans-
verse processes are short and heavy, with facets for the rib-tubercles which
are more obliquely lateral than in the first thoracic. The prezygapophyses
are of the cervical pattern, while the postzygapophyses have the thoracic
character and are placed on the ventral side of the overhanging neural
arch. The spine, though incompletely preserved, was evidently higher
and heavier than that of the first thoracic, shorter and more slender than
in the succeeding vertebrze, and has a moderate backward inclination.
The following vertebrze of the anterior thoracic region (Pl. XVIII, fig.
5) have short, wide, somewhat depressed and opisthoccelous centra, grow-
ing more compressed and triangular and having flatter faces posteriorly ;
the anterior rib-facets are very elongate, but narrow, while the posterior
pair are rounder and more deeply concave. The transverse processes are
short, but heavy and conspicuous, with prominent metapophyses arising
from the dorsal border, and have subcircular, slightly concave facets for
the rib-tubercles. The neural canal is small and nearly circular and the
pedicels of the neural arch are deeply notched for the passage of the
spinal nerves. The neural spines are very high, laterally compressed
and broad, so that those of several successive vertebrz are in contact for
their whole length, and have a strong backward inclination or even a
backward curvature.
In the anterior thoracic region, the vertebrze closely resemble the cor-
126 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
responding ones of Macrauchenza, figured by Burmeister (64, Pl. II, fig.
17), but in the Pampean genus the metapophyses are not so prominent,
while the neural spines are narrower, thicker and more recurved.
In the middle of the thoracic region, in 7/eosodon, the neural spines
become narrow, more spaced apart and lower, though retaining their back-
ward inclination through nearly the entire region. In the hinder part, the
spines become shorter, broader and more erect; the anticlinal vertebra
may be either the last or the penultimate thoracic. The transverse pro-
cesses remain prominent throughout the series, gradually descending from
the neural arch to the centrum. The facet for the rib-tubercle persists
even on the last vertebra, in which the process has a different form, being
broader and more depressed. Between the tenth and eleventh thoracic
vertebrze, takes place the transformation of the zygapophyses from the
thoracic to the lumbar type. On the tenth, the prezygapophyses still
present upward and are small and nearly flat, but the metapophyses, which
are now close to them, are strongly concave on the mesial side and curve
around the postzygapophyses of the ninth, though not actually articulating
with them. The postzygapophyses of the tenth are convex and semicylin-
drical and the prezygapophyses of the eleventh are concave.
The lumbar vertebree (Pl. XVIII, fig. 7) are sometimes five and some-
times six in number. Except the last one, they have centra which are
laterally compressed and of subtrihedral shape, much like those of the
thoracic vertebrze, but larger, instead of the broad, depressed centra, usual
in the lumbar region. The last lumbar vertebra has a short, depressed
centrum, with broad anterior, very narrow and convex posterior face. As
in all of the known Santa Cruz Litopterna, the zygapophyses are of the
semicylindrical, interlocking character, most resembling those of the Arti-
odactyla. Metapophyses are present throughout, but are less prominent
than in the thoracic region and are very small on the penultimate lumbar.
The neural spines are high, broad and strongly curved forward and, except
in the first and second lumbars, they have not the abruptly truncated and .
thickened free ends which occur in the lumbar region of nearly all mam-
mals, but are gently rounded. On the last vertebra, the spine is decidedly
smaller than on any of the preceding lumbars.
The transverse processes are broad and curved forward; this breadth
increases posteriorly, reaching a maximum on the last vertebra. On the
hinder border of each transverse process of the penultimate lumbar and
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 127
the anterior border of the last, is a large oval facet, by means of which
the processes of the two vertebrze articulate. The last lumbar is further
characterized by the extremely large and deeply concave oval facets, much
larger than the posterior face of the centrum, on the hinder border of the
transverse processes, for articulation with corresponding surfaces on the
sacrum.
The sacrum (Pl. XVIII, figs. 8, 8a) is long and narrow and may consist
of seven vertebrze, only two of which articulate with the ilia. Even the
first sacral vertebra has but a small and much depressed centrum and on
each side of it, on the pleurapophysis, is a large, convex, oval boss, for
articulation with the transverse process of the last lumbar, as above
described. On the first sacral, the pleurapophyses are large and massive,
making this region of the sacrum very wide; those of the second vertebra
are much smaller. Posteriorly, the coalesced centra grow smaller and
smaller and that of the last vertebra is very small indeed. The first two
pairs of ventral foramina for the nerves are very large, the third pair are
of moderate size and the succeeding ones are minute. Functional pre-
zygapophyses are present on the first sacral and very small vestigial
remnants on the second; behind this, not even vestiges remain. The
neural canal is remarkably small, even anteriorly, diminishing in size
posteriorly, and the hinder aperture is a mere narrow slit. The coalesced
neural arches are deeply concave transversely, owing to the elevation of
the lateral borders into high ridges.
No caudal vertebree have yet been found, but it is evident from the
character of the sacrum and the greatly reduced size of the hindermost
centrum, that the tail must have been very short. é
The first rib is short and nearly straight, with large head set upon a
prominent neck, and very conspicuous tubercle ; the shaft is slender proxi-
mally, broadening and flattening toward the distalend. Speaking generally,
it may be said that the anterior ribs have large heads and tubercles, and
long, broad and curved shafts, while posteriorly they become more slender
and rod-like. Separate tubercles are present throughout, even on the
last rib.
The sternum (PI. XVIII, fig. 9), which is not completely preserved in
any of the specimens, is very peculiar. The presternum is long, laterally
compressed, and keel-like, with broader dorsal, and very thin ventral
border, and increasing in dorso-ventral depth posteriorly ; near the anterior
128 PATAGONIAN EXPEDITIONS: PALA‘ONTOLOGY.
end are facets for the first pair of ribs. This is succeeded by a number
of mesosternal segments (how many, it is not yet definitely known) which
are shorter and somewhat broader, but very deep dorso-ventrally and
laterally compressed. Next follows the complex shown in the figure. Of
this, the first segment is compressed and deep anteriorly, becoming broad
and dorso-ventrally depressed behind. The last segment of the meso-
sternum is wide and flat, and somewhat constricted in front of the pos-
terior expansion, which bears facets for three pairs of ribs. The xiphi-
sternum, which, in the adult animal, is ankylosed with the last mesosternal
segment, is quite narrow and appears to have been short.
The Appendicular Skeleton.— The scapula (Pl. XIX, figs. 1, 1@) is
high and rather narrow and, in its general proportions, recalls that of the
rhinocerotic genus /Zyvacodon from the North American Oligocene. The
position of the spine is slightly back of the median line of the blade, and
thus makes the prescapular fossa a little larger than the postscapular ; the
former has an irregular surface of low convexities and shallow concavities,
while the latter is more simply concave. The glenoid cavity is large and
concave in both dimensions and of subcircular outline, except anteriorly,
where the articular surface extends over upon the coracoid and is much
narrower.
The coracoid is a prominent, rounded and somewhat rugose boss, which
is not incurved and does not overhang internally. The neck of the
scapula is short and wide, and there is no definite coraco-scapular notch.
The coracoid border is somewhat sinuous ; after a short course upward
and forward from the neck, it becomes nearly straight for a considerable
distance and curves, without angulation, into the suprascapular border.
The latter is quite strongly convex and joins the glenoid border by a
rounded angle. The glenoid border is nearly straight and inclines down-
ward and forward till just above the neck, where it forms a concave curve.
For most of its length, this border is elevated as a ridge and in the distal
half of its course this ridge divides into two, both ridges dying away to
the neck. Beginning some distance below the suprascapular border, the
spine rises very gently to its full height and pursues a somewhat twisted
course, the proximal half being deeply concave behind, and the distal half
more nearly perpendicular to the blade. About midway of its length, the
spine gives off a very large triangular, and rugose metacromion. The
acromion proper is also very large and round, projecting strongly back-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 129
ward, but not at all distally, the distal border of the spine being nearly
straight and normal to the plane of the blade.
The fore-limb is long and slender and its three divisions are propor-
tioned somewhat as in Ayracodon, the cursorial rhinoceros from the
Oligocene of North America. That is to say, the upper arm is very short,
the fore-arm is greatly, and the manus moderately elongate.
As just indicated, the humerus (Pl. XVIII, fig. 10; Pl. XIX, fig. 5)
is relatively short and stout, hardly more than two-thirds the length of the
skull. The head is large and rather flattened and projects backward but
little ; the external tuberosity is very largely developed, as a high, massive
ridge, which rises far above the level of the head, while the internal tuber-
osity is very much smaller and less prominent. The bicipital groove,
which is single and without any tubercle, is wide and deep; the deltoid
crest is prominent and rugose and extends down for nearly half the length
of the shaft, ending abruptly below. The shaft is proportionately quite
massive and of the usual ungulate form. Proximally, the shaft is much
compressed laterally and very thick antero-posteriorly, though this latter
dimension is not so exaggerated as in Macrauchenia. Distally, the shaft
becomes wider transversely and thinner antero-posteriorly ; the epicon-
dyles are massive and the external one is quite prominent; there is no
entepicondylar foramen. The supratrochlear fossa is well-marked and
the anconeal fossa is large, of irregular shape and deep, but the two fossze
are not connected by a perforation. The trochlea, which is placed some-
what obliquely to the long axis of the shaft, rising toward the inner side,
is extremely simple and forms a pulley-shaped surface not unlike the
astragalar trochlea of a rhinoceros. Of the two borders, the internal is
the sharper and more elevated; posteriorly, the groove for articulation
with the ulna is very deep. The articular surface is continuous through-
out and shows no indication of a division into facets and there is no
median trochlear ridge.
The bones of the fore-arm (Pl. XIX, fig. 2) are long and slender and,
though without any tendency to codssification, they are in close contact
throughout their length and there isno radio-cubital arcade. Proximally,
the ulna is much stouter than the radius ; distally, the radius is the heavier
of the two.
The radius (Pl. XIX, figs. 2, 3, 3@) is elongate and very slender.
Indeed, in view of the tridactyl and mesaxonic manus, the enlargement of
130 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
the radius and reduction of the ulna are remarkably small, when compared
with Artiodactyla or Perissodactyla of a similar degree of specialization.’
The head is very small (see fig. 37), though its principal diameter is trans-
verse and there can have been no power of rotation upon the humerus.
The articular surface for the latter is very simple and slightly concave
antero-posteriorly ; on the inner side, this surface is sharply bent down-
ward so as to bear laterally against the prominent internal border of the
humeral trochlea. The proximal facet for the ulna is curiously small and
is confined to a very narrow area on the posterior face of the head near
the inner side, and a somewhat longer, narrow area near the outer side.
The amount of movement between the two fore-arm bones must have been
very limited.
The shaft is long, slender, irregular and with a decided, though not
very strong, forward curvature; it is antero-posteriorly compressed and its
principal diameter is transverse, broadening distally. The distal end is
moderately widened and thickened, so as to be quite massive, and exter-
nally, the widening is abrupt, fitting into a corresponding depression of
the ulna, the facet for which is a large concavity. No sulci for the extensor
tendons are visible on the anterior face. The carpal surface is very dis-
tinctly divided into two facets, for the scaphoid and lunar respectively, of
which that for the scaphoid is much wider and is reflected farther upward
upon the palmar face of the radius, while the lunar facet is deeper palmo-
dorsally. Each facet is composed of two parts, a dorsal concavity and a
palmar convexity, though the two parts form one uninterrupted surface.
The ulna (Pl. XIX, figs. 2, 4) has a very long olecranon, which pro-
jects upward and gently backward, its posterior extension not being
nearly so abrupt as in AZacrauchenia. The sigmoid notch is deep and
describes nearly a semicircle. On the inner side of the proximal half of
the notch, the articular surface is sharply reflected upward, so as to pre-
sent laterally, while on the outer side, the surface is broadly divided into
two parts. Distally, the facet extends forward beneath the humeral
trochlea and appears on the inner side of the head of the radius, when
viewed from the front.. The proximal facets for the radius are very small,
a larger internal, and extremely narrow external one.
The proximal part of the shaft is triangular and very stout, rapidly be-
coming laterally compressed and very narrow, but remains thick antero-
posteriorly and is of nearly uniform cross-section throughout its length.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 131
Above the distal end, the shaft is abruptly contracted, to receive the distal
expansion of the radius, and there is a rather large, convex facet for the
latter. The surface for the pyramidal is saddle-shaped and has its prin-
cipal diameter in the dorso-palmar dimension; it is continuous with the
small facet for the pisiform, which is quite internal in position.
In Macrauchenta, the fore-arm bones are coéssified, though not always
completely so; they are broader transversely and more compressed antero-
posteriorly than in 7eosodon, even at the distal end. Proximally, the
ulna is much heavier than the radius and the relative proportions of the
two bones remain very much as they are in the Santa Cruz genus.
The manus of 7heosodou (Pl. XIX, fig. 6) is surprisingly like that of
Macrauchenia even in the minor details, as has already been pointed out
by Ameghino ('940, 281). However, a few slight, though not entirely
insignificant, changes may be observed in the Pampean genus. The
manus is of mesaxonic symmetry and is tridactyl, not only structurally,
but functionally, the digits being of nearly equal length and thickness,
and each carrying its due proportion of the weight.
The carpus (Pl. XIX, figs. 6, 62) is low proximo-distally and wide
transversely, though relatively somewhat higher and narrower than in
Macrauchenia. WLydekker’s statement (’96, 79) that in the Pampean genus
the arrangement of the carpal elements is in vertical series, without inter-
locking, is not quite accurate. As will be seen, there is a certain degree
of interlocking, even in the Santa Cruz genus, and this is increased in
Macrauchenta.
The scaphoid is low, broad and very thick palmo-dorsally, and of irreg-
ularly quadrate outline; the proximal end is covered by the radial facet,
which has a dorsal convexity, dying away upon the inner side, and a
palmar concavity. On the distal end are three facets; internally, a small
concavity for the trapezium, then follows a very large surface for the
trapezoid, composed of dorsal and palmar concavities, the junction of which
formsa ridge. Finally, there is a heavy distal process, which projects some-
what internally and carries a facet for the magnum and, on the ulnar side,
one for the lunar. This extension of the scaphoid over upon the magnum
is the only departure from the serial arrangement to be found in this
carpus.
The lunar is very narrow, but moderately high proximo-distally, and
very thick palmo-dorsally. The radial surface is strongly convex, extend-
132 PATAGONIAN EXPEDITIONS: PALA‘ONTOLOGY.
ing well down upon the dorsal face, and becoming slightly concave near
the palmar side. The facet for the pyramidal is very large and somewhat
concave, but is confined to the distal moiety of the ulnar face; proximally,
the two bones are quite separate and not in contact (see Pl. XIX, fig. 62).
Distally, the lunar rests only on the magnum and is quite widely separated
from the unciform by the interposition of the pyramidal. On this side, the
carpus is strictly taxeopod in the arrangement of its elements.
The pyramidal is relatively large and has a greater proximo-distal height
than any of the other carpals. Proximally, this bone is rather shallow
palmo-dorsally, but becomes very thick in this dimension toward the distal
end, and a blunt, rugose process projects from the palmar side. The ulnar
facet is very large and saddle-shaped and that for the pisiform, which is
also large, presents internally as much as toward the palmar side. On
the radial side, near the distal end, is a large surface for the lunar and,
distal to this, a narrow facet for articulation with the magnum. This con-
tact is, however, entirely lateral, the pyramidal not overlapping the magnum
at all. Here we find a difference from the carpus of Macrauchenza, in
which the pyramidal extends over upon the magnum and thus forms
another departure from the serial arrangement. (See Gervais, ’55, Pl. 8,
fig. 2.)
The pisiform is short, heavy, of irregular shape and much thickened at
the free end, but nearly uniform in the other diameter. The proximal end
is also thickened and bears a high, narrow and somewhat saddle-shaped
surface for the pyramidal, and on the external side a very small plane
facet for the ulna. In Macrauchenza, the pisiform is of similar general
shape to that of Zeosodon, but is more compressed laterally, and con-
tracts to form a very much more slender proximal end.
The trapezium is much reduced in size and was of no great functional
importance. Proximo-distally, it is elongate, tapering to a bluntly rounded
point at the distal end, but the transverse and dorso-palmar diameters are
small. The proximal end is a small, simply convex surface for articula-
tion with the scaphoid, while on the ulnar side are two facets, one for the
trapezoid and, below this, a much larger concavity for the second meta-
carpal. The trapezoid I have not seen, though it may be readily recon-
structed from the space left vacant between the surrounding bones, which
shows it to have been nearly as large as the magnum. This element has
been figured by Ameghino (’944, 282, fig. 18).
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 133
The magnum is stout, but not very large, though it has a complete
system of articulations, being in contact with the second and third meta-
carpals and all of the carpals except the trapezium and pisiform. The
proximal end is unequally divided between the facets for the scaphoid and
lunar, the latter being somewhat wider and more completely proximal,
while the former has an oblique position. The “head” of the magnum
is quite low and there is no hook given off from the palmar face. On the
ulnar side are two nearly plane facets, a proximal one for the pyramidal
and a distal one for the unciform. Distally, the entire surface of the
magnum is covered by the large, somewhat saddle-shaped facet for the
third metacarpal, and on the radial side, near the distal end, is an oblique
facet for the second metacarpal, which extends across the whole dorso-
palmar diameter of the magnum. Above this is a small surface for articu-
lation with the trapezoid, and this facet is confined to the dorsal moiety
of the magnum.
In Macrauchenia, as above indicated, the magnum is further modified
by its extension under the pyramidal, or the overlapping of the pyramidal
upon it. In this way the facet on the magnum for the pyramidal becomes
proximal and an interlocking of a very exceptional type is brought about,
the magnum lying beneath the scaphoid on one side and beneath the
pyramidal on the other, while the lunar is excluded from any contact with
the unciform. In all Perissodactyla, on the contrary, interlocking is pro-
duced by the growth toward the ulnar side of the scaphoid and lunar,
accompanied by the reduction of the pyramidal. Thus the scaphoid rests
more or less extensively uponthe magnum and the lunar on the unciform,
the pyramidal being excluded from the magnum. In the Proboscidea, as
in the Macrauchenide, the magnum articulates with both scaphoid and
pyramidal, and, in both groups, this exceptional arrangement is, no doubt,
due to the relatively large size of the ulna.
The unciform of 7Zeosodon is considerably larger than the magnum;
it is low, broad and thick and has a short, massive and rugose process
projecting from the palmar face. On the proximal end is a large, saddle-
shaped surface for the pyramidal, and on the distal end, an almost equally
large facet for the fourth metacarpal, which, however, narrows much
toward the palmar side. A very small distal facet indicates the presence
of the vestigial fifth metacarpal. On the radial side are two facets, a large
one for the magnum and a smaller, oblique one for the third metacarpal.
134 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
The metacarpus consists of three functional members, mc. II, III and
IV, and a minute remnant of mc. V. In symmetry, the manus is mesax-
onic, or perissodactyl, the median plane bisecting the third digit, which is
symmetrical, while the lateral digits, II and IV, each asymmetrical in
itself, form a symmetrical pair. Functionally, the manus is almost iso-
dactyl, with three subequal digits.
Metacarpal II is elongate and relatively heavy. The head is large and
carries four distinct articular facets; on the radial side is quite a large,
convex surface for the trapezium and on the proximal end is the large,
irregular facet for the trapezoid. On the ulnar side, a prominent, heavy
projection abuts against the magnum and overlaps the head of me. III.
This magnum facet is slightly oblique and that for me. III is in two parts,
one presenting distally and the other toward the ulnar side; the latter is
a small, oval concavity, placed near the dorsal border. The shaft is stout
and heavy, of trihedral section and curved so as to make the radial border
concave. The distal trochlea is low and the carina is continued around
upon the dorsal face, though it is much more prominent on the palmar
side; where the dorsal and palmar portions of the keel meet, there is a
distinct notch. On the palmar face, a non-articular ridge extends upward
for some distance in continuation of this carina, of which it evidently acted
as a support, and gradually dies away upon the shaft.
Metacarpal III is longer, but decidedly more slender than either me. II
or IV. The head is quite heavy and is drawn out into a massive triangular
process on the palmar side; the facet for mc. II extends across the whole
dorso-palmar diameter of the head and, for most of its length, is obliquely
proximal in position, but near the dorsal border it curves downward and
presents toward the radial side. The proximal surface for the magnum is
large and irregularly saddle-shaped. From the ulnar side is given off a
very short projection, which articulates with the unciform, but occupies
only the dorsal moiety of the head. On the ulnar side, below the unci-
form projection, are two facets for mc. IV, which are elongated proximo-
distally, but very narrow; the one near the dorsal border is quite deeply
concave, the other near the palmar border is nearly plane. ‘The shaft is
long, narrow, straight and symmetrical, and subquadrate in section,
broadening slightly near the distal end. Distally, the semicylindrical
trochlea is higher than that of mc. II or IV, but the carina is less promi-
nent on the dorsal face, indeed, is but faintly indicated, while on the pal-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 135
mar side it is extremely prominent and sharp. It is strengthened, as in
the other metacarpals, by extending up the palmar side of the shaft into
a non-articular ridge.
Metacarpal IV is the counterpart of me. II, though slightly shorter, not
rising so high into the carpus proximally and extending distally a little
below the end of mc. II. The head bears a prominent palmar ridge-like
process, which, however, is less massive than that of mc. III; the unci-
form facet is convex and slightly oblique, broad dorsally and narrowing
much toward the palmar side. On the radial side of the head are two
surfaces for me. III, that on the dorsal side prominent and convex, that
on the palmar side sessile and plane, and on the ulnar side is a small
facet for the minute mc. V. The shaft and trochlea resemble those of
me. II reversed.
The vestigial fifth metacarpal has not been found, but its presence may
be confidently inferred from the facets on the unciform and me. IV.
The phalanges of the first row are long and slender and are much alike
in all three digits, except that in the median digit this phalanx is shorter
than in the laterals, a very unusual proportion in a foot of mesaxonic
symmetry, as well as broader and more depressed. In all the phalanges
of this row the proximal trochlea is a shallow concavity, deeply divided
by the groove for the metacarpal carina. The distal trochlea is simply
saddle-shaped, but with the articular surface reflected far over upon the
dorsal side.
In the second row the phalanges are short, broad and heavy, with thick
proximal and much depressed distal ends. In the median line the dorsal
lip of the proximal trochlea is produced into a more or less prominent,
beak-like process. The second phalanges of all the digits are of nearly
equal length; in the third digit it is slightly longer than in the second or
fourth.
The ungual phalanges are short, broad, thick and almost nodular in
shape, resembling somewhat those of the slender-footed Oligocene rhino-
ceroses, but they have lost all vestige of the median cleft. In digit III the
ungual is larger than in the laterals, broad and symmetrical, with rugose
free border, while those of digits II and IV are quite irregular and
asymmetrical.
The pelvis (Pl. XIX, fig. 7) is short and broad and resembles that of
Macrauchenia, but is less specialized in several particulars. The ilium
136 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
has a very short peduncle, which is deep dorso-ventrally, but laterally
compressed and thin, and which expands rapidly into the very broad iliac
plate. This plate is less strongly everted than in the Pampean genus and
the division into dorsal and ventral processes is less distinctly marked.
Another difference from J/acrauchenza is that the ventral process is wider
and has a much less thickened border. On the inner side of the dorsal
process is a large, rugose depression for the attachment of the sacrum, the
process rising well above the latter and concealing it in Side-view. On
the outer side, the gluteal surface is smooth and but slightly concave. The
pubic border of the ilium is very indistinct and speedily dies away upon
the inner side. The acetabulum is large and has a very prominent
anterior border, and a deep, conspicuous sulcus for the round ligament.
The ischium is quite short and stout, trihedral for most of its length,
but expanding posteriorly into a thin plate. The spine and sciatic notch
are feebly marked, more distinctly in some individuals than in others,
while the tuberosity is very strongly developed, being prominent and rugose,
though not nearly so long as in Macrauchenia. The pubis is short and
heavy, especially in the symphysial region, the anterior part of which is
very thick. As a whole, the symphysis is longer than in the last named
genus. On the anterior border of the pubis, near the acetabulum, is the
prominent and rugose spine. The obturator foramen is an elongate oval,
with its principal axis in the antero-posterior direction, while in A/acrau-
chenia it appears to be transverse.
The femur (Pl. XX, figs. 2, 3, 3a) is long and very much like that of Mac-
rauchenia, but considerably lighter and more slender. The head is sessile
and rather flattened and does not rise to the level of the great trochanter,
while in the Pampean type it is large and hemispherical and projects
prominently above the trochanter. The sulcus for the round ligament is
a broad and deep emargination of the articular surface on the posterior
aspect of the head and not visible in front-view. The great trochanter is
very high, heavy and rugose, rising proximally into a blunt point, which
extends above the level of the head, and is recurved so as to enclose a large,
deep digital fossa. In Macrauchenia the great trochanter is much reduced
in height, but is very massive and rugose. The second trochanter on the
femur of 7heosodon is quite small, forming a low, thin ridge, and placed
quite far below the head. The third trochanter also has a low position
on the shaft, nearly midway between the two ends, and projecting pos-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 137
teriorly almost as much as internally. It varies considerably in size in
different individuals and, though never very large, it is much better devel-
oped and more conspicuous than in Macrauchenza.
Proximally, the shaft is broad and strongly compressed and flattened
antero-posteriorly, narrowing and thickening downward and becoming
subcylindrical above the third trochanter, but with a strong forward cur-
vature. Inthe Pampean genus, on the other hand, the shaft has a greater
degree of antero-posterior flattening throughout. On the postero-external
side of the shaft and near the distal end (in 7/eosodon) is a large and
rugose pit for the attachment of the plantaris muscle and, on the anterior
face, there is a conspicuous suprapatellar fossa. The rotular trochlea is
narrow, deeply grooved and somewhat asymmetrical, due to its oblique
position and the greater elevation of its internal border; distally, the
articular surface is continuous with that of the external condyle, but is
quite separate from the inner condyle. The condyles are rather small
and irregular and quite widely separated ; the external one is narrower
and more convex and projects more laterally, the internal one more
posteriorly.
The patella (Pl. XX, fig. 4) is a long, narrow, irregular and rather thin
bone, the antero-posterior thickness of which is much less than in Jac-
vauchenta. The proximal end is obliquely truncate, rising toward the
inner side, and the distal end narrows toa blunt point. The anterior face
is moderately convex and not very rugose, and the posterior, articular
face is divided by an obscurely marked ridge into narrower external and
wider internal portions.
The leg-bones, which in Macrauchenza are codssified, are entirely sepa-
rate, and are considerably shorter than the thigh, thus reversing the pro-
portion of the segments which is found in the fore limb.
The tibia (Pl. XX, figs. 5, 5a), which is much shorter than the femur,
closely resembles that of Macrauchenia, except for its slenderness. The
proximal end is very heavy; the external condyle is narrower antero-
posteriorly, but more concave than the internal, which is nearly plane.
The spine is deeply bifid, and the portion formed by the external condyle
is higher, broader and heavier than that which belongs to the inner con-
dyle. The cnemial crest is short, soon dying away upon the shaft, but
its proximal portion is very massive and rugose and is deeply impressed
by the fossa for the insertion of the great extensor tendon of the thigh.
138 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
On the fibular side of the head is a deep sulcus for the tendon of the
extensor longus digitorum. The proximal facet for the fibula is small and
is confined to the postero-external angle of the tibial head.
The shaft is heavy and nearly straight, with trihedral proximal portion,
gradually contracting below and expanding again near the distal end,
where it becomes irregularly oval in cross-section. The distal end is
narrower and thicker than in Macrauchenza and is divided into a broader
external, and narrow and deeper internal portion, by a low intercondylar
ridge. Anteriorly, this intercondylar ridge is produced into a short, blunt
tongue, while the posterior tongue is much more prominent and larger
in every dimension. In some individuals the astragalar surface is inter-
rupted by a small, shallow sulcus, which is chiefly on the external condyle
and the intercondylar ridge. (See fig. 5a.) The internal malleolus is
singularly small and confined to the dorsal moiety of the internal side ;
in Macrauchenia this process is still further reduced and has, in fact,
almost disappeared. The distal fibular facet is large and oblique.
Of the fibula (Pl. XX, figs. 6, 6a) only the distal half is preserved in
the collections. That the proximal end was small, is shown by the facet
for it on the head of the tibia. The shaft is much more reduced and
slender than that of the ulna and its middle portion is quite thin and
laterally compressed, though retaining considerable antero-posterior thick-
ness. Distally, the shaft increases steadily in thickness. The distal end
which is stout and forms a heavy external malleolus, bears three facets ;
on the inner side is an inclined surface, which is overlapped by the tibia,
and this meets at an obtuse angle the surface for the outer condyle of the
astragalus. For the calcaneum is a large distal facet, consisting of an
anterior convexity and posterior concavity, though there is no interruption
in the continuity of the articular surface. On the outer side of the distal
end is a conspicuous groove for the peroneal tendon.
As in the case of the manus, the pes (Pl. XX, fig. 7) is very similar to
that of Macrauchenia, with only a few minor differences. The tarsus
(Pl. XX, figs. 7-9) which is relatively high and narrow, maintains in all
respects the character of the Litopterna and differs in points of fundamen-
tal significance from that of the Perissodactyla, despite the mesaxonic
symmetry of the foot.
The astralagus has quite a perissodactyl appearance, which, however,
is entirely superficial in character. The trochlea is deeply grooved and
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 139
asymmetrical, owing to the larger size and greater prominence of the ex-
ternal condyle; the neck is moderately elongate and bears, just below the
trochlea, a deep fossa, which receives the anterior tongue of the tibia, when
the foot is in extreme flexion on the leg. The head, which is depressed
and flattened in the dorso-plantar direction, is broad and quite strongly
convex; it articulates only with the navicular and is widely removed from
any contact with the cuboid. On the plantar side are two facets for the
calcaneum, an external one, which is rather small, deeply concave and
invaded by a sulcus, so as to be almost divided into two parts; the sus-
tentacular facet, which is narrow and quite widely separate from the exter-
nal facet, is almost plane.
In Macrauchenia the astragalus has a broader and less deeply grooved
trochlea, a shorter neck, without fossa for the tibial tongue, and a less
convex head. The two plantar facets are much more nearly approxi-
mated, and the external one is larger and is not invaded by a sulcus.
The calcaneum of Yeosodon is very elongate, especially the tuber,
which contracts toward the free end, where it again expands in a club-
shaped thickening, but has no tendinal groove. The fibular facet, though
narrow, is large, conspicuous, strongly convex; the external astragalar
facet is in two parts, which meet at anopen angle. The sustentaculum ts
large and prominent and bearsa plane, oval facet for the astragalus. The
distal end is occupied by the extensive, twisted-looking surface for the
cuboid, which is obliquely concave both transversely and planto-dorsally ;
there is no facet for the astragalus on the inner side of the distal end, the
two bones being separated at this point by a narrow space.
In Macrauchenia the calcaneum has a relatively shorter and heavier
tuber and a smaller facet for the fibula.
The navicular (of 7/eosodon) is rather narrow, but of relatively con-
siderable proximo-distal height, especially the external half of it. From the
plantar face is given off an extremely large and prominent process or
hook (see Pl. XX, fig. 8) which, though compressed laterally, is yet very
heavy. Proximally, the navicular bears quite a deep concavity, to receive
the head of the astragalus, and the distal end bears facets for the three
cuneiforms. That for the entocuneiform is small and obliquely lateral
rather than distal in position, that for the mesocuneiform is larger, while
the facet for the ectocuneiform is still larger and descends farther distally,
which gives an appearance as though a step were cut in the navicular to
receive the mesocuneiform.
140 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
In Macrauchenia the navicular is very. similar, but is relatively shorter
proximo-distally and the step on the distal end is less distinct.
The entocuneiform is a long, narrow, scale-like bone, convex on the
tibial and concave on the fibular side, and with abruptly truncated distal
end. Proximally, there is an oblique, concave facet for the navicular,
below this a small lateral facet for the mesocuneiform, and near the distal
end and dorsal border a small, oval surface for the second metatarsal. The
mesocuneiform is a relatively large, irregularly oval bone, broadest on the
dorsal side; the navicular facet is slightly concave in the dorso-plantar
direction, and that for the second metatarsal is saddle-shaped. Other
facets are a small one on the tibial side, near the plantar and proximal
edges, for the entocuneiform, and a still smaller one on the fibular side
for the ectocuneiform.
The ectocuneiform is very large; the dorsal face is nearly square, though
somewhat higher than it is wide, and thence the bone narrows to a blunt
edge on the plantar side, which bears a small, rugose tuberosity. Proxi-
mally, the surface for the navicular is irregularly concave in front, convex
behind, while the distal facet for the third metatarsal is quite deeply con-
cave planto-dorsally. On the tibial side, near the distal end, are two
widely separated facets for the second metatarsal, a small one near the
dorsal and a large one near the plantar border. Articulation with the
cuboid is limited to a small facet on the fibular side near the proximal
end.
The cuboid is a very large bone and, though widely separated from the
astragalus, is yet relatively high proximo-distally. The proximal surface
rises steeply toward the plantar side, making the height of the bone nearly
twice as great on this side as it is on the dorsal. On the tibial side are
three facets for the navicular, two near the proximal end and plantar side,
and the third a projection from about the middle of the tibial face, upon
which the navicular rests and which bears also a small facet for the ecto-
cuneiform. The fibular side has two prominent tubercles and, between
them, a tendinal sulcus. Distally, is a very large, concave surface for the
fourth metatarsal, and, external to this a minute facet for the vestigial fifth,
which is more lateral than distal in position.
The metatarsus consists of similar elements to those of the metacarpus,
three functional members arranged in mesaxonic symmetry, and a vestige
of another, the fifth.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 5 IAI
Metatarsal II is long and heavy ; the head is narrow, but thick, and has
a prominent hook-like projection from the plantar side. On the tibial
side, below the head, is a small concave facet for the entocuneiform. This
metatarsal rises far above the proximal end of mt. III and has an exten-
sive lateral bearing against the ectocuneiform by means of two facets, one
near the dorsal border and the other upon the plantar process. Beneath
the dorsal facet for the ectocuneiform is an elongate, narrow surface for
articulation with mt. III. The shaft is stout and trihedral, with rounded
borders, and the distal trochlea resembles that of mc. II, with the very
prominent carina extending over the dorsal face.
Metatarsal III is somewhat longer than mt. II, but as its proximal end
is at a lower level than that of the latter, its effective length is consider-
ably greater. The head is broad and thick, ending behind in a prominent
plantar hook, and carries a large surface for the ectocuneiform, which is
convex planto-dorsally, slightly concave transversely. On the tibial side,
near the dorsal border, is a facet for mt. I] and another on the plantar
hook, and on the fibular side are two facets, in corresponding positions
for mt. IV. The shaft is straight, slender and subquadrate, widening
somewhat near the distal end. The very prominent carina is plantar and
distal; on the dorsal face it is very obscurely indicated, being even less
distinct than in the corresponding metacarpal.
Metatarsal IV is the counterpart of mt. II, but is a little shorter and
heavier. A plantar hook is present, as in the other metatarsals, and the
irregularly convex cuboid surface extends the full depth of this hook. On
the fibular side of the head are two small facets for the vestigial mt. V,
and on the tibial side are two others for mt. III, the dorsal one a promi-
nent convexity and the plantar one circular and plane. The distal end is
asymmetrical, with a large rugose tuberosity on the fibular side, and the
carina is prominent on the dorsal face of the trochlea.
Metatarsal V has not yet been found, but its presence and its vestigial
character are indicated by the facets on mt. IV and the cuboid.
The phalanges of the pes are so like those of the manus as to require
no particular description.
Restoration (P|. XV1).—Of the many curious animals which make up
the Santa Cruz fauna, few can have had a more remarkable appearance
than Zheosodon. In size, there is no great difference among the various
species so far found in the Santa Cruz formation, the best known species,
142 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
T. garvettorum, is considerably taller and stouter than the llama, to which
it bears some resemblance in general proportions. The head is rather large,
but low and the much shortened nasals and immense, tapir-like anterior
nares give it a highly peculiar and characteristic appearance. The long,
slender rostrum and mandible, and the conical, sharp-pointed and slightly
recurved anterior teeth are almost reptilian in effect. The long neck and
limbs and the rather short trunk and very short tail are the especial
features which recall the proportions of the llamas, but the much shorter
tridactyl feet and separate metapodials form a striking difference from any
of the existing Tylopoda. An unusual character is to be found in the
relative lengths of the limb-segments; the upper arm is short and the
fore-arm very long, while in the hind limb this proportion is reversed, the
thigh being long and the leg short.
The skeleton of Macvauchenia bears an unmistakable resemblance to
that of 7eosodon, but, in addition to the numerous differences of detail
described in the preceding pages, there are some obvious differences of
proportion. M/acvauchenia was a much larger animal than the Santa Cruz
genus and has relatively longer limbs, with which the elongation of the
neck has not kept pace. The skull, in adaptation to the growth of the
proboscis, has become quite different in appearance and the trunk is prob-
ably shortened, though this is not altogether certain. At all events, the
trunk-vertebrze are proportionately smaller and have more slender spines,
which are more inclined in the anterior part of the thoracic region and
more erect in the lumbar. The scapula is much narrower than in 7/e-
osodon and the acromion and metacromion are far less developed, while
the pelvis is shorter, is set more nearly vertical to the axis of the spinal
column and has the iliac plates much more strongly everted. These dif-
ferences are just what we should expect to find between ancestor and
descendant and, so far as present knowledge is concerned, there is no
reason why we should not regard 7heosodon as directly ancestral to the
Pampean Macrauchenta.
Synonymy.— The isolated position of Z7eosodon in the Santa Cruz
fauna is such that there has been little difference of opinion as to the
proper nomenclature. Lydekker (93, 65) has made this genus a synonym
of Oxyodontotherium from the much later Parana beds, but with this view
I am quite unable to agree, on account of the differences in tooth-structure,
not to mention the highly probable differences in the skull. Ameghino
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 143
has described a genus, Pseudocelosoma, which he believes to be distinct
from Zheosodon, but which is here regarded as a synonym of the latter.
In the original description (’917, 294) the very large, single inner root of
the upper molars is given as the diagnostic character, but, as already
pointed out (p. 110), this is true of all the speciesof 7/eosodon. In a sub-
sequent paper (’04, 54) he writes that this animal shows numerous differ-
ences from the last-named genus, the only one of which mentioned is,
however, the presence of a pillar of the cingulum between the internal
cusps of the upper molars. As we have seen (p. 109), this is too variable
a character to be of generic significance.
THEOSODON LYDEKKERI Ameghino.
(Plates XVII, Figs. 3, 3a; XX, Figs. 6-7.)
Theosodon Lydekkevt Ameghino ; Enum. sistematica, etc., 1887, p. 19.
The original description of this species is founded upon fragments of a
large animal, the upper molar-series having an antero-posterior length of
73 mm. Ameghino’s subsequent descriptions of much more complete
material, assigned to this species, all refer to considerably smaller indi-
viduals with upper molar-series 62 mm. in length, or less. Such a differ-
ence of size, nearly 17 per cent., would not of itself be a sufficient reason
for the specific distinction between the larger and the smaller individuals,
but two circumstances lead me to the conclusion that such a distinction
should be made. (1) The differencein size is very constant and ina large
series of specimens there is no perceptible tendency to approximation,
though, no doubt, a still larger series would show some such tendency.
This constancy is in very marked contrast to the conditions seen in Pyo-
terothertum, in which size is extremely variable and wide differences are
connected by every intermediate gradation. (2) The milk-premolars of the
larger animals differ decidedly from those of the smaller, especially dp®
and *, which have much larger internal crescents and prominent posterior
pillars on the external face. Whether the permanent premolars show a
similar difference the known material does not enable me to say. In my
judgment, therefore, the name 7: /yd@ekkerz should be restricted to the large
individuals, which are, unfortunately, but very inadequately represented
in the collections.
The following measurements are taken from a young, incomplete skull
(No. 15,717) in which m+ has just come into use and m? is still concealed
in the jaw.
T44 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
MEASUREMENTS.
Upper milk-premolar series, length. 074 Dp3, width . i : : : .O17
Dp}, length (@. ¢., ant.-post. diam.) .013 Dp4, length : ‘ : : .022
“ width (z. ¢., greatest trans. diam.) .007 “width . ‘ : 3 : 0195
Dp?2, length : : : j .O195 M4, length . : : : : .024
“width . : : : : .O15 “width . : 6 : : .0223
Dp3, length : ; : : .019
In the collection of the American Museum of Natural History is a hind
foot (No. 9219), lacking the calcaneum, astragalus and navicular, which
is apparently referable to this species. The specimen is figured in PI.
XX, fig. 7, with the missing parts supplied from other individuals. In
one respect this foot is manifestly abnormal (not shown in the drawing)
namely, in the disproportionate width of the distal end of metatarsal III
and the adjoining part of the first phalanx. This width is undoubtedly
due to disease or accident in the lifetime of the animal.
Metatarsal II, length . ‘ : .134 Phalanx 1, digit II, distal thickness .O16
es “ proximal width : .020 Gig & Genet, : .037
as ef ss thickness . .032 GB By GB 8 soon, Well ~ .027
sf “ distal width . : .029 660 2 Ee KS ephickeness .022
Coe eenthickmness : .029 BB, CG Ghist, Welln .025
Metatarsal III, length . 4 . .146 Ungual phalanx, digit II, prox. width 022
s “proximal width =. .023 s i « «* dist. width. .030
GG GG a thickness. .035 Phalanx 1, digit III, length . , .057
a “distal width . : .040* Gf, HS Soros Yuh .039*
as Co cumestnicicneSS\aume .029* Cel eine ns Wem Omnat nicht ess .028*
Metatarsal IV, length . : 0 B27, [Oe ceeccunclistalawicthiam. .024
s “proximal width . .024 Phalanx 2, digit III, length . ~~. .034
gs a ag thickness. .034, CG 2 GB GB iors, Tell .025
ag “distal width . : .028 GB GG alge, yateltin .022
st i «thickness ; .028 Phalanx 1, digit IV, prox. width . .029
Phalanx 1, digit II, length . : .054 Goi @ chse, walin 5 .023
at I, “ “ prox. width . .029 Phalanx 2, digit IV, length . ; .033
a 1, “ “ «© — thickness .O21 GC 2 GB GG syrose wrkatin . .025
* Pathological.
Locahties. — Not given for type. No. 15,717 was collected by Mr.
Peterson 10 miles south of Coy Inlet.
THEOSODON LALLEMANTI Mercerat.
(Plates XVII, Fig. 4 ; XVIII, Figs. 1, 1a, 3, 3a, 7,9; XIX, Fig. 1; XX, Figs. 3, 32.)
Theosodon lallemanti Mercerat ; Rev. del Mus. de La Plata, T. II, 1891,
Peete:
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. T45
Theosodon Frenzel Mercerat ; Ibid.
Theosodon lydekkert Amegh., in part; Rev. Argent. de Hist. Nat., T. I,
1891, p. 294; Enum. Synopt., etc., 1894, p. 28; Les Ongules fossiles
de l’Argentine, Rev. del Jard. Zool. de Buenos Aires, T. II, 1894, p.
280.
Oxyodontotherium lydekkert Lydekker; Anales del Mus. de La Plata, T.
100, misiog, (9, Wr
If the restriction of the name 7: lydekkerz to the larger animals, as sug-
gested in the foregoing paragraphs, be correct, the oldest name available
for the present species is 7: /allemanti Mercerat, though our knowledge
of the animal is almost exclusively due to the work of Ameghino, who has
briefly described and fully illustrated the dentition, skull and feet.
T. lallemantt, which is much the commonest of the Santa Cruz species,
may be distinguished not only by its size, but also by certain features in
the dentition and skull. The upper molars may or may not have the two
inner cusps connected by a cingulum and thus in worn teeth either two or
three enamel lakes may appear, a very variable feature. The milk pre-
molars are quite different from those of 7: Lydekkerz, dp® and * having
much smaller and more symmetrical internal crescents and less developed
pillars on the external face. The sagittal crest is high and thin, expanding
anteriorly into a long, narrow sagittal area. The nasal processes of the
frontals are very short and narrow, and the nasals, though greatly shortened,
are longer than in 7: garrettorum, projecting farther in advance of the
maxillary border, and are in contact throughout their length.
In the table, No. 1 is the type of 7: /allemanti and No. 2 that of 7:
Jrenzel, the dimensions in both cases being taken from Mercerat’s paper.
MEASUREMENTS.
Vo. No. Vo. No.
15,210. 7 2. 16,003.
I2, length : ; : : : .O108
Upper premolar-molar series, eatin : : : HQ
«« premolar series, length . , 6 : O71
P1, length (2. ¢., antero-posterior alas). : : .O15 .013
““ width (2. ¢., transverse diameter) . : : : .O10
P2, length é ; : ¢ ‘ 6 : c .0178 .0169 .018
“width : ; : : ; é 6 3 .018
P3, length 6 c 6 : : : : 3 .0179 .018 .020
“width ‘ : : ‘ : : p 6 .O21
P4, length : Z : : : : é : .020 .0206 .O18
146 PATAGONIAN EXPEDITIONS :
P4, width : : :
Upper molar series, length
M3, length
“width
M2, length
“width
M3, length
“width
I;, length
Ts ; :
Te; 0 ;
Lower canine, length
P;, length
1 sf
Beas :
Pa oa ; 6 é
Lower molar series, length
M,, length
M;, “ 5 . : ; : 5
PALZZONTOLOGY.
No. No.
15,210. I.
0215
0234
.O14
.O145
.O155
.0167
.0198
.O19 .0214
.020 .022
.0225 .0226
.066
.022 .0226
.023 .023
.0215 .0226
No.
2.
.024
0175
.020
.025
.024
No.
16,003.
.022
.060
.020
.023
.0205
.0235
.020
.022
The measurements of the milk-teeth and associated molars are taken
from two individuals, those of the upper jaw from No. 15,359 and those
of the lower jaw from No. 16,002.
Di2, length . 5 ‘ : : .0093
oC Trclin 5 6 0 5 .0043
Di8, length . : : . 6 .O10
“width . : 5 : : .005
Ds, length . : : : ‘ -O1I5
Seawict ems : 5 : : .0055
Upper milk-premolar series, length. .068
Dp?, length 5 0 5 0 .O12
“width . : ; : : .007
Dp2, “ : : : ; OIL
Dp2, length - . : : : .O17
Dp4, “ : : : : O19
Upper molar series, length . : .062
M4, length . : 4 9 : .O21
“ width . 0 : : 0 -020
M2, length . 0 6 0 0 .022
“width . : : 6 : O21
M3, length . : : : i .018
“width 0 6 .018
Lower milk-dentition, length 0 ILI
Di;, length .
“width.
Dig, length .
“width
Dig, length .
“width
Dg length
“ width
Lower milk-premolar series, length.
Dp,, length
“width .
Dps, length.
«width .
Dps, length.
«width .
Dpz, length.
«width .
M,, length .
“width
.008
.004.
.O1I5
.005
.O125
.005
.O14
.0055
.OO1
.O16
.006
.020
.008
.0235
.009
.025
.013
.022
.O14.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 147
Ameghino gives the following measurements of his specimen: Length
of skull from condyles to premaxillaries, 32 cm.; length of lower dentition
from iz to mg, 19 cm.; depth of mandible below pz, 31 mm. (’91g, 294).
A considerable number of skeletal parts are associated with the jaw, No.
15,216, and from this individual the following dimensions have been taken.
These bones show that 7: /a//emant is a stoutly built animal, and that the
trunk-vertebree have heavy spines. Especially in the lumbar region are
the neural spines high and very broad antero-posteriorly. The third,
trochanter of the femur is large and prominent.
MEASUREMENTS.
Atlas, length : : : : .065 5th lumbar, width of anterior face . .035
« dorso-ventral height . : .047 ss us «posterior face. .030
Axis, length incl. odontoid . é 117 fs «« dorso-ventral height
a6 avexcls a . : .096 incl. neural spine : : : .119
«« width of anterior face . : .043 Sacrum, length . : : : .162
3d cervical, length of centrum : .104. ss anterior width of centrum. .033
ss «« —_width of anterior face . .040 as “ — over pleurap. 154
6th cervical, length of centrum . .076 “posterior width of centrum. .018
i ss width of anterior face . .042 Scapula, length in median line . 245
7th cervical, length of centrum . .048 «« —_-width of neck . : F .052
&¢ ce width of anterior face . -O415 Pelvis, length ; j C ; oh7/
13th thoracic, length of centrum . .044 “« _width over iliac plates . , -390
as as width of anterior face. .034 a ss eischialutuber wee oD
14th thoracic, length of centrum . .045 Acetabulum, ant.-post. diameter. .O51
fs « width of anterior face. .038 us transverse “‘ é .042
1st lumbar, length of centrum p .049 Pubic symphysis, length : : .098
ff «« —_ width of anterior face . .038 Humerus, length from head . : .239
sf « dorso-ventral height ‘s f ext tulbeiea 251
incl. neural spine ¢ é : 125 ss width of trochlea . : .047
2d lumbar, length of centrum : .047 es “over epicondyles . .066
«width of anterior face . .036 Femur, distal width . : : .074
3d lumbar, length of centrum : .049 cs “thickness : : .092
“f «width of anterior face . .036 Tibia, length including spine . : .260
4th lumbar, length of centrum : .052 “proximal thickness. : O81
as «width of anterior face . .038 «distal width P : 3 .046
5th lumbar, length of centrum 3 .048 & “thickness . : : .O41
Localities. —Neither Ameghino nor Mercerat give localities for their
specimens. No. 15,359 was found by Mr. Hatcher at Killik Aike, and
No. 15,216 was collected by Mr. Peterson 5 miles south of Coy Inlet.
,
148 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
THEOSODON GARRETTORUM Sp. nov.
(Plates XVI; XVII, Figs. 1, 2, 5; XVIII, Figs. 2, 4, 4a, 6, 8, 8a, 10; XIX, Figs. 1a, 2,
5-7; XX, Figs. 2, 5, 52.)
This species is of very nearly the same size as the preceding one, but
differs from it in a number of well-defined characters. The type-specimen
is the nearly entire skeleton (No. 15,164) figured in Plate XVI, though
completed with some addition of missing details from other species. The
name is given in honor of Messrs. John W. and Robert Garrett, of Bal-
timore, whose generosity has been one of the mainstays of the Patagonian
expeditions.
The permanent dentition is essentially similar to that of 7: /allemantz,
but there is no cingulum between the inner cusps of the upper molars and
m2 is more reduced in size, and in pg; the anterior inner fossa is not so
deeply concave.
MEASUREMENTS.
Upper dentition, extreme length . .190 ME, width . ; : ‘ : .019
I1, major diameter 5 i ; .O10 I,, major diameter j : j .013
“‘ minor diameter ; : F .006 “ minor diameter : : : .0085
12, major diameter ; : F .OII I, major diameter ‘ ; j .013
““ minor diameter 0 0 6 .008 “minor diameter 6 . : .0085
I3, major diameter i 6 ; .OII Lower canine, major diameter ¢ .O14
“minor diameter : . : .008 st “minor diameter 0 .009
Upper canine, ant.-post. diameter . 0125 Lower premolar-molar series, length .140
fs “transverse diameter . .009 «« premolar series, length : .070
Upper premolar-molar series, length .137 P;, length . : 6 : : .O15
«« premolar series, length 6 .074 “width . d d 5 : .009
P1, length (¢. ¢., ant.-post. diam.) . O15 Pz, length . . : 0 : O18
“ width (2. ¢., greatest trans.diam.) — .009 Seawidthiane 5 2 . : .0095
P2, length . : 0 0 0 .O165 Pz, length . j : : 6 021
“ width . 4 3 : : .016 <enwiclthinne ‘ : : 5 .O12
P3, length . 3 : 4 : .O18 Pz, length . : : A .022
GS osyptatin 4 : : ‘ .018 “width . 0 0 5 6 .0135
P4, length . ; 6 ; P .O195 Lower molar series, length . : .070
“ width . 5 : . : .020 M;, length . : 3 : ; .0225
Upper molar series, length . : .063 “ width . : 0 : : O15
M4, length . : : d d .020 My, length . . : . : 023
soe awidthiray " Gatan Mca sae ai teO2 2c POUR nan Word io!) KORO
v2 leno chi caer ain ate ERR 22) Mig ene thse i me O23
Se WAGEDMA Ms | ERENT MEW dice Shei Bboy Po PAWAGUh te 219/59) pelle a ene OTE
M3, length . é : : : .O1Q5
The milk-dentition of this species is not definitely known, but a frag-
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 149
ment of mandible (No. 15,378) with dps and z and the alveolus of mz, is
probably referable to it, as is indicated by the unusual shallowness and
thickness of the horizontal ramus.
MEASUREMENTS.
Dps, length. : : : ; .024 Dpg, length. : : ; : .026
«width . ; j : , .O1O «width . ; : ; : .O12
In construction, these teeth display no noteworthy differences from those
of 7: dallemante.
The skull, which in the type-specimen has suffered some distortion and
dorso-ventral flattening from pressure, differs from that of 7: /allemanti
ina number of significant details. The cranium is shorter, the brain-case
more rounded, and the sagittal crest is shorter and the anterior sagittal
area is narrower; the nasal processes of the frontals are very much more
developed, especially in transverse width, and widely separate the nasals,
which are not in contact with each other at any point. The nasals them-
selves are considerably shorter than in the preceding species and are
attached for their whole length to the maxillaries, not projecting freely
beyond them, as they do in 7: /alemantz. The free dorsal border of the
maxillaries is thinner and less rounded and anteriorly these bones send
out processes between the premaxillaries, almost excluding the latter from
forming any part of the narial opening, while in 7: /a//emanti they are
more extensively concerned in bounding the opening. Finally, the hori-
zontal ramus of the mandible is distinctly more shallow in the dorso-
ventral dimension than in 7: /alemanti and has a thicker and more
rounded ventral border. If the very young mandible above mentioned (No.
15,378) be properly referred to 7: garrettorum, then the difference in the
character of the ramus is even more marked in the young than in the adult.
Owing to the crushing to which the skull has been subjected, not many
measurements can be profitably given.
MEASUREMENTS.
Skull, length in median basal line. B23} Occiput, width at base . ; : .079
‘s “cond. to prmx. . : 339 Nasals, length , ; : : .047
See xtremeslenetiiines : ‘ 349 Mandible, depth below pg. : .028
Cranium, length to ant. rim of orbit . .177 fs as herical ayar : .033
Face, length orbit to prmx. . ° 179 height of condyle . 0 O81
The skeleton has been very fully described in the account of the genus
150 PATAGONIAN EXPEDITIONS: PALA‘ONTOLOGY.
and material is wanting for a comparison of the different species in regard
to the variations in skeletal structure among them. It may, however, be
pointed out that in 7: garretforum the vertebre, especially in the lumbar
region, have shorter, narrower and more slender spines than those of 7
Jallemant: and that the third trochanter of the femur is less prominently
developed.
MEASUREMENTS.
Atlas length. : ; . : .067 Radius, distal width . d ; .04.2
“« width over transv. proc. ; .IO1 s “thickness. . . .028
“ dorso-ventral height . : .047 Ulna, length. 2 : : : R75
3d cervical, length of centrum ; -105 “prox. width at rad. facets. .053
" «width of anterior face. .043 “distal width. : : : .O17
6th cervical, length of centrum . .072 off “thickness . : ; .036
e “width of anterior face. -O41 Carpus, length in median line. 5 .036
7th cervical, length of centrum .. .048 G qoln 4 F ‘ : .062
“ «width of anterior face. .045 Metacarpal II, length . : : .130
Ist thoracic, length of centrum. .038 ee “proximal width . .026
ih as width of anterior face. .037 ss sf s thickness . .026
2d thoracic, length of centrum : -035 ss “distal width . : .024
“ width of anterior face . .034 “s «thickness ‘ .026
1oth thoracic, length of centrum . -040 Metacarpal III, length . : . -145
G 1 width of anterior face .036 a “proximal width . .025
Last thoracic, length of centrum . .045 as a fs thickness. .028
ae ss width of anterior face .040 fc “distal width . : .025
2d lumbar, length of centrum : .048 sf f “thickness. .0245
ss “width of anterior face . .040 Metacarpal IV, length . : ; .122
4th lumbar, length of centrum. . .048 « “proximal width . .024
a «© width of anterior face . .0395 “ ss of thickness. .025
Last lumbar, length of centrum. .037 S “distal width . : .0245
ss «~~ width of anterior face. .038 os Gc GC UdwiclmnEess . .0245
i ff «© posterior face .027 Phalanx 1, digit II, length . : .058
Sacrum, length . : : : aisle os H, GS iors, Wan 0245
HY anterior width of centrum. .030 a To ant Ckaess .022
Ss POSLELIOL EL Cum sf .O12 oH 1, “ “ distal width . .020
Scapula, length . : : ‘ .253 of Toe emi chness .O16
width of neck . 0 d .052 Phalanx 2, digit II, length . : .028
Humerus, length from head . : .234 a 2, “ proximal width .0245
‘ GG C. exe, WOR o -255 s 2, “ “ distal width . .020
uy proximal thickness. é .090 Ungual phalanx, digit II, length . .0225
és dist. width over trochlea . .050 cs se Ce ypraldny .025
a « «© epicondyles .070 Pelvis, length : ; : : 305
Radius, length . : ; : 311 Ilium, length : j 5 . .192
«proximal width. s ; .035 “greatest width . j : .237
a « thickness . : .023 “width of peduncle 0 . .058
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. I51
MEASUREMENTS.
Ischium, length . : j : 114 Astragalus, width of trochlea. P 0415
Femur, length from head. : 325 Metatarsal II, length . : : .134
«« proximal width. : : .099 ‘ “proximal width : .O19
“distal width . : : .073 a of sf thickness . .031
«6 “thickness. : ‘ .086 fs “distal width . : .025
Tibia, length with spine. : : E2VAL as «thickness : .026
«« proximal width . : F .O81 Metatarsal III, length . F : .142
ee i thickness. ; .077 « “proximal width . O21
«distal width. : : 6 .053 “ s thickness. .033
ot “thickness . : : 044 sf “distal width . : .027
Astragalus, length : 2 . .058 s§ #6 “thickness- . .0255
Localities. — The type (No. 15,164) was collected by Mr. Peterson ten
miles south of Coy Inlet and the jaw fragment with milk-teeth (No. 15,378)
which is probably referable to this species, was also found by Mr. Peterson
at the same place.
THEOSODON FONTAN Ameghino.
Theosodon Fontane Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891, p.
294.
Oxyodontotherium Fontane Lydekker; Anales del Mus. de La Plata, T.
JL, BSCR, (Os Oy
No specimens definitely referable to this species are contained in the
Princeton or New York collections. According to the original description,
T. fontane is about the same size as 7: /allemanti, but relatively more
robust; the anterior part of the rostrum is shorter and broader; the molars
are heavier and the incisors and premolars are set more closely together,
not so spaced apart. (Ameghino, Joc. cit.)
THEOSODON GRACILIS Ameghino.
(Plate XX, Figs. 1, 14, 4, 8.)
Theosodon gracilis Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891, p.
295.
Theosodon patagonensts Mercerat; Rev. del Mus. de La Plata, T. II,1891,
p. 48 (fide Ameghino).
Theosodon debilis Mercerat; Ibid., p. 49 (fide Ameghino).
Oxyodontotherium angustidens Lydekker; Anales del Mus. de La Plata,
Ws I, SIR, fO. Go}
This species is a little smaller than 7: Zalemantd and of more slender
152 PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
proportions, the rostrum and symphysial region of the mandible are nar-
rower and more pointed, and more or fewer of the anterior teeth tend to
wear into horizontal instead of pyramidal grinding surfaces. This latter
feature, however, would appear to be less constant than Ameghino has
supposed.
In the collection of the American Museum is a skull (No. 9230), appar-
ently referable to this species, from which the following dimensions have
been taken.
MEASUREMENTS.
Upper dentition, length i1-m2 : .178 I,, major diameter : ‘ P .O113
I2, major diameter : : : .OII “ minor diameter 4 : : .009
“ minor diameter 6 : : -O10 Lower canine, major diameter : 013
13, major diameter : 4 : OIL a «minor diameter 6 -OLL
““ minor diameter : : : .O10 Lower premolar series, length é O71
Upper canine, major diameter : .O12 P;, length . : 6 0 : .O14
Gt «minor diameter : -OII GC nich : : 3 : -O105
P2, length (2. ¢., ant.-post. diam.) . .O17 P;, length . 3 ; : ; .O17
“ width (2. ¢., greatest trans. diam.) .O155 « width . : : i ; .O1O
P38, length . : ‘ d : .O17 P,, length . ; : : é O19
“ width . : 6 0 : .020 “width . : ; . : OI
P4, length . é 6 : : .O17 Pz, length . : : ‘ i 021
“ width . : : : : .022 “ width . : j : ; .O13
Upper molar series, length . : .058 M,, length . ; i : 3 .020
Mi, length . F : ; : .O18 “ width . P : 4 : .O13
Sommawicit hae 2 0 . : .022 My, length . 6 F 0 ; 022
M2, length . ; ; : : .O21 Ms, width i : j .O14
«width . ‘ : : ‘ .022 Skull, length in median basal line . -295
M3, length . : : ; : O21 “ “condyle to prmx. . Buz
«width . : : : : .O21 “extreme length . : : 57/7
I,, major diameter : ; 6 .008 Cranium, length cond. to rim of orbit .168
“ minor diameter 6 ; : .007 Face, length orbit to premaxillary . .163
I, major diameter : : j OIL Occiput, width at base . 6 : O81
“ minor diameter : : ; .008 5 Mandible, depth below py. : .038
A fragmentary skeleton (No. 15,798) obtained by Mr. Hatcher at Lake
Pueyrredon may be provisionally referred to this species, with which it
agrees fairly well in size, but the diagnostic portions of the skull are
wanting.
MEASUREMENTS.
P3, length . : : : : .O16 “width . F : : : .018
G synictin, , F F : 018 M4, length . ; : é : 018
P4, length . : : : 2 .O175 “ width . : ; : : .0205
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 153
MEASUREMENTS.
Axis, width of anterior face . : .062 Astragalus, length é ; : .053
Femur, proximal width. : : .09I tf width of trochlea. : .037
«distal width over condyles . .0745 us GC 6 igeall Gael . .030
Tibia, proximal width . : : .070 Metatarsal II, length . : ‘ .122
«distal width. : : : .050 ‘s “ proximal width . O21
ct “thickness . . : .039 « “ «thickness . .029
Tarsus, length in median line : .074 a “ distal width . : .0245
«width ; 6 j : .O51 Metatarsal III, distal width . 5 .024
Calcaneum, length : : : III Metatarsal IV, length . ; : 116
« width over sustentac- “proximal width . .0215
ulum é : 6 , , .O41 at “distal width . : .025
Localities. —Neither Ameghino, Mercerat, nor Lydekker gives any
localities for their specimens. No. 9230 was collected by Mr. Brown at
Halliday’s Ranch on the Rio Gallegos and No. 15,798 by Mr. Hatcher at
Lake Pueyrredon.
THEOSODON PATAGONICUS (Ameghino).
Pseudocelosoma patagonica Amegh.; Rev. Argent. de Hist. Nat., T. I,
1891, p. 294.
It has been pointed out in the foregoing pages that in several species of
Theosodon the two internal cusps of the upper molars are often connected
by a cingulum, but this is a very variable feature, differing even in the two
sides of the same jaw. Thus, in well worn teeth, the number of enamel-
lakes may be either two or three. In 7: fatagonicus the cingulum is
replaced by a pillar, in what appears to be a very constant fashion, and
equally constant is the presence of three lakes in the abraded grinding
surfaces. The species is not represented in the Princeton or New York
collections.
Localities. — Not given.
THEOSODON KARAIKENSIS Ameghino.
Theosodon karatkensis Amegh.; Nuev. Espec. de Mamif. Cretac. y Terc.,
1904, P- 54:
Very inadequately known from two molars, an upperand a lower, which
leave the specific characters much in doubt. The distinctness of the
species is, however, made probable by the horizon in which it occurs.
Locality. — Kar Aike.
154 PATAGONIAN EXPEDITIONS: PALA‘ONTOLOGY.
ADIANTHUS Ameghino.
Adianthus Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891, p. 134.
Adiantus Amegh.; Enum. Synopt., etc., 1894, p. 27.
This genus is known to me only from the author's descriptions, which
are substantially as follows: The third upper molar resembles that of
Macrauchenia in miniature, with similar number and arrangement of the
enamel lakes, but the external face lacks the mesostyle, which is replaced
by adepression. There are two external roots and one internal, the latter
very broad. (Ameghino, ’044, 52.)
The mandibular dentition has the formula, Iz, Cz, Pz, Ms, and the teeth
are arranged in continuous series. The lower molars differ from those of
Theosodon in having no trace of the spur or pillar in the posterior crescent.
The incisors are small and placed in the same longitudinal line as the
grinding teeth. Thecanine resembles the incisors in form and the anterior
premolars are like the canine, and the posterior premolars intermediate in
character between the anterior premolars and the molars. From the first
incisor to the last molar there is a gradual and successive modification of
form. The horizontal ramus of the mandible has a straight inferior
border and is of nearly uniform dorso-ventral depth throughout. (Ame-
ghino, ’94a@, 27, 28.)
ADIANTHUS BUCCATUS Ameghino.
Adianthus buccatus Amegh.; Rev. Argent. de Hist. Nat., T. I, 1891,
P- 134- ;
Adiantus bucatus Amegh.; Enum. Synopt., etc., 1894, p. 28.
This is a very small animal, far smaller than any species of 7/eosodon.
The lower dentition is62 mm. long; mris 7 and mz g mm. in length,
and the horizontal ramus below mz is 14 mm. in dorso-ventral depth.
(Ameghino, ’94a, 28.)
Locahties. — Not given.
SCOTT: LITOPTERNA OF THE SANTA CRUZ BEDS. 155
BIBLIOGRAPHY.
Allen, J. A.
1910 The Black Bear of Labrador. (Bulletin American Museum of Natural History, Vol.
SON VAUI, jo, Ta)
Ameghino, Florentino
1887b Enumeracion sistematica de las especias de mamiferos fosiles coleccionados por Carlos
Ameghino en los terrenos eocenos de la Patagonia austral. La Plata, 1887.
1889b Contribucion al conocimiento de los mamiferos fosiles de la Republica Argentina.
(Actas de la Academia Nacional de Ciencias de Cordoba, T. V.)
1891a Las antiguas conexiones del continente Sud Americano y la fauna eocena argentina.
(Revista Argentina de Historia Natural, T. I, p. 123.)
t891b Caracteres diagnosticos de cincuenta especias nuevas de mamiferos fésiles argentinos.
(Ibid., p. 129.)
1891d Mamiferos y aves fosiles argentinas. — Especias nuevas, adiciones y correccionas.
(Ibid., p. 240.)
1891g Nuevos restos de mamiferos fosiles descubiertos por Carlos Ameghino en el eoceno
inferior de la Patagonia austral.— Especias nuevas, adiciones y correcciones, (bid.,
p. 289.)
189th Observaciones criticas sobre los mamiferos eocenos de la Patagonia austral. (Ibid.,
p. 328.)
1894a Enumération synoptique des espéces de mammiferes fossiles des formations éocénes
de Patagonie. (Bol. de la Acad. Nac. de Cienc. en Cordoba, T. XIII, p. 259.) In
the citations from this paper given in the text the paging is that of the separate edition.
1894b Sur les ongulés fossiles de l’Argentine, examen critique de l’ouvrage de M. R.
Lydekker. A study of the extinct ungulates of Argentina. (Revista del Jardin
Zoologico de Buenos Ayres, T. II, p. 193.)
1898 Sinopsis geologico-paleontologica. (Segundo Censo de la Republica Argentina, T. I.
Buenos Aires, 1898, p. 113.)
1904a Recherches de morphologie phylogénétique sur les molaires supérieues des ongulés,
(Anales del Museo Nacional de Buenos Aires, Ser. 3, T. III, p. 1.)
1904b Nuevas especias de mamiferos Cretaceos y Terciarios de la Republica Argentina.
(Published in Anales de la Sociedad Cientifica Argentina, TT. LVI, LVII, LVIII.)
In citations from this paper given in the text the paging is that of the separate edition.
Bravard, Auguste
1858 Monografia de los terrenos terciarios.
Burmeister, Hermann
1864 Descripcion de la Macrauchenia Patachonica. (Anales del Museo Publico de Buenos
JNres, Al, 1, js B22)
1879 Description physique de la République Argentine, T. III.
1885 Examen de especies nuevas de la formacion terciaria del pais. (Anales del Mus. Nac.
de Buenos Aires, T. III, Ent. XIV.)
Cope, E. D.
1892 The Litopterna. (American Naturalist, 1892.)
156 PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
Gaudry, Albert
1904 Fossiles de Patagonie. (Mém. de la Société Géologique de France, Paléontologie, T.
XII, p. 5.)
Gervais, Paul
1855 Animaux nouveaux ou rares recueillis pendant |’expédition dans les parties centrales de
l’ Amérique du Sud... (Expédition dans les parties centrales de l’Ameérique du Sud .. .
sous la direction du comte Francis de Castelnau. 7™° Partie, Zoologie, T. I, p. 1.)
Lydekker, Richard
1893 A study of the extinct ungulates of Argentina. (Anales del Museo de La Plata, T. II.)
1896 A geographical history of mammals. Cambridge, 1896.
Mercerat, Alcides
18g9ic Sinopsis de la familia de los Bunodontheridz. (Revista del Museo de La Plata, T. I,
Pp. 445.)
1891e Caracteres diagnosticos de algunas especies del gen. Theosodon. (Ibid., T. II, p. 47.)
Roth, Santiago
1903 Los ungulados sudamericanos. (Anales del Museo de La Plata, T. V, p. 5.)
Zittel, Karl von.
1891 Handbuch der Palzontologie, Bd. 1V, Munchen und Leipzig, 1891-1893.
fm
ae
Gr, aay
‘ Sie
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
DO PILAINAMOIOIN, Ole je1LAVI18 IL.
DrapraPHorus mMayuscuLus: Restoration of the skeleton. Nearly all of the
bones in this drawing are from two individuals, No. 15,799, and No.
9270, American Museum of Natural History. In scale the figure is a
little less than 4 of the natural size
(VoL. vit) :
PAGE
31
PATAGONIAN EXPEDITIONS VOL. VII. IPL ZAIN IL
Bruce Horsfall del
DIADIAPHORUS
ee ie
g. 1a.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
IDIPILAINAUIIIOIN, Ole JFILAINS, JC
D1apDIAPHORUS MaAjUSCULUS: Skull, top view, X#. (A. M. N. H.,
No. 9291.) : : : ;
My et Skull, right side, x#. (A. M. N. Hy
No. 9291.)
« 96 P+, 2, M2, crown view, X+. From
a cast of the type specimen of D.
adiplinthius : 3 5
DIADIAPHORUS VELOX: Left ramus mandibuli, X +. From a cast of
a specimen, probably male, in the Ame-
ghino collection. 3 ; j :
43 bs Right ramus mandibuli, X +, of a presumable
female. (No. 15,295.)
(VOL. vil)
PAGE
15
32
28
38
PATAGONIAN EXPEDITIONS VOL. VIL PLATE, H.
ak
Bruce Horsfall del
Werner & Winter, Frankfort 2M
DIADIAPHORUS ‘
a
fora a
Quite li
PATAGONIAN EXPEDITIONS: PALAZSONTOLOGY.
SI LANAMINIOM, Ol® ILAITS, IOUL
. I, DraprapHorus rozsustus: M® of right side, crown view, X}. From
cast of type specimen of D. calops
Amegh. 6
5 WG, es as M+ of same individual
oe ff - type: Right upper dentition, crown view,
X+. From cast of type specimen
Amegh. collection ; :
eS. ae os type: Right lower dentition, crown view,
X 4, of same individual
ig. 4. DtapiapHorus Mayuscutus: Left upper dentition, crown view, x +.
(No. 15,799.) . : ; :
tee “ “ Left lower dentition, crown view, X +.
(No. 15,799.) . : ‘ j :
. 6. cs af Left femur, dorsum, X #. (No. 15,799.)
Ts cs 36 Right tibia and fibula, dorsum, X 2.
(No. 15,799.) .
. 8. DiapiapHorus vELOx : Right lower dentition, crown view, X t.
(No. 15,295.) .
(VoL. vit)
PAGE
tif
PATAGONIAN |
EXPE]
DIMTONS WOR. War
Bruce Horsvall del
DIADIAPHORUS
PLATE II.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
IPCAGANVAITKOIN, Ola lela, IN,
PAGE
Fig. 1. DiapiapHorus mayuscuLus: Occiput. (A. M. N.H., No. geo) B 15
Sissy, 2, a 06 Atlas, dorsal view. : : 19
iga2a: as ‘ lettaside
Biomess “ Axis, right side . : ‘ . ‘ 19
Fig. 4. a a Fourth lumbar, left side. 2 : 21
Fig. 5 “ ss Last lumbar, dorsal side. ; ‘ 21
lehige, g a Left humerus, front view . : : 22
Fig. 6a. ae ef ce fe distal end
tea i a Right radius, front view . : : 28
Fig. 7a. e ‘ & «distal end
Fig. 8. ie Right ulna, outer side... : 23
All the figures are three-fourths aeieaceall size andy except iguan, all ; are from
No. 15,799.
(VoL. vit)
VOLVIL. PLATE DV.
I
U
—
J
4
©
ZZ
Op)
PATAGONIAN EXP
|
Bruce Horsfall del Werner & Winter, Frankfort 2M
DIADIAPHORUS
re n
at
iit
Fig. qT.
Fig. 1a.
Bion 1:
Fig. 2.
Fig. 2a.
Fig. 3.
Fig. 4.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
EX<PEANAIMONGOE eb Aviis a?
DrapIAPHORUS MajuscuLUS: Left manus, dorsum. (A. M.N. H.,
“
No. 9196.)
The same, outer side.
Phalanges of the same, outer side.
Left pes, dorsum. (A. M. N. H., No.
9196.) F : : :
The same, outer side.
Right manus, dorsum. (No. 15,799.)
Right carpus, outer side. (No. 15,799.)
All the figures are three-fourths natural size.
(VOL. vit)
PAGE
23
26
29
23
PLATE) WV,
PATAGONIAN EXPEDITIONS VOLAIL
rere sneer
Bruce Horsfall del
DIADIAPHO
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
EXPLANATION OF PLAGE Vi:
Fig. 1. LicaPHRIuM PyNEANUM type: Skull, left side. (No. 15,711.)
Fig. 1a. i ee «Right upper teeth, crown view. (No.
EW) : : : :
Fig. 16. ‘ oe «« Left lower teeth, crown view. (No.
it 7/iNa)) : é 5 : 5
Pigg: e : «Right pes, dorsum, X #. (No. 15,711.)
Fig. 3. LicapHrium FLOwWERI: Right lower teeth, crown view. (No. 15,309.)
Fig. 3a. i Right lower teeth, outer side. (No. 15,309.)
Fig. 4. LicapHRiuM PyRAMIDATUM: Right upper teeth, crown view. From
cast of type in Amegh. Coll. . .
Fig. 5. ot “ Right lower teeth, crown view. From
cast of type in Amegh. Coll.
All the figures, except fig. 2, are natural size.
(VOL. vir)
PAGE
49
48
49
54
43
46
46
PAL VAIS) WAL
DITIONS VOL.VIL
EXP]
PATAGONIAN |
fall’ del
ors
Bruce H
Fig.
Fig.
Fig.
PATAGONIAN EXPEDITIONS: PALAZZONTOLOGY.
PA RILAINAIEILOIN,, Ql? JALAN INE WIOL,
1. LicAPHRIUM FLOWERI: Facial region of skull, right side. (A. M. N.
Jak, IN@s ©2775.) ; ; ;
2. gs Right lower teeth, crown view. From cast
of type of ZL. granatum. Amegh. Coll.
2B ss Ss Right upper teeth, crown view. From cast
of type of L. zxtermissum. Amegh. Coll.
4. “ Right lower teeth, crown view. From cast
of type of L. zntermzssum. Amegh. Coll.
5. LIcaPHRIUM PARVULUM: Right upper molars, crown view. From
cast of type. Amegh. Coll. :
6. LicaPHRIuM PRoxImum: Right upper molars, crown view. From
cast of type. Amegh. Coll.
Fe es iH Right lower teeth, outer side. From cast of
mandible. Amegh. Coll.
7a. us os The same, crown view.
8: TETRAMERORHINUS FORTIS: Facialregionof skull, dorsal side. From
cast of type. Amegh. Coll.
9. ct WG Right upper teeth, crown view, of the
same.
Fig. 10. TETRAMERORHINUS LUCARIUS: Facial region of skull, dorsal view.
From cast of type: Amegh. Coll. .
ioe pIit. ‘ Right upper teeth, crown view, of
the same.
All figures natural size.
(voL. vit)
PAGE
82
82
PLATE VIL
r
L
XPEDITIONS VOL. VI
2
PATAGONIAN E
p
¥
4
i!
ea, 2:
V
ae
Frankfort 7M
linter,
Werner & W
Bruce Horsfall del
UM
1>) 1/1
EB
ilies Int
imi (Ol
iy
@H
TX
PR
ION, ee
=
HR
(CJAUE
=
al
Fig.
Fig.
. 1a.
PATAGONIAN EXPEDITIONS: PALA‘ONTOLOGY.
EXPLANATION OF PLATE VIII.
PROTEROTHERIUM CAVUM: Skull, ventral side. (No. 9245, A. M. N.H.)
ee «Skull, dorsal side. (No. 9245, A. M. N. H.)
‘ «Left upper teeth, crown view. From
cast of co-type. Amegh. Coll.
«4 a Left lower teeth, crown view. From cast
of co-type. Amegh. Coll. ;
PROTEROTHERIUM INTERMEDIUM: Mandible, left side. (No. 15,996.)
“ & Left lower teeth, crown view. (No.
15,996.)
PROTEROTHERIUM PYRAMIDATUM: Right upper molars, crown view.
From cast of type. Amegh. Coll.
PROTEROTHERIUM sp.: Second upper molar, right side, crown view.
PROTEROTHERIUM ACRE: First upper molar, left side, crown view.
From cast of type of Heptaconus acer.
~ Amegh. Coll. ‘ : :
Fig. 8. TicHopon quapriLosus: Third lower molar, left side, crown view.
From cast of type. Amegh. Coll.
All figures natural size.
(VOL. vit)
PAGE
56
74
74
74
68
80
83
PATAGONIAN EXPEDITIONS VOL. VIL.
ae
PALATE WALL,
|
Bruce Horsfall del
PROT
el mt (O) Weal}
ERIUM
Werner & Winter, Frankfort 9M
ise, Ty
Big. ia.
ISG Bp
Fig. 2a.
dorms
Riga
Fig. 5.
ico:
Ieee, Fe
Rigk Ss.
IIe, @)
Fig. ro.
Eoamnate
Fig. 11a.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
JDC AGAINVATOIOIN, Ql IML IDX,
PROTEROTHERIUM DODGEI, type: Left upper teeth, outer side. (No.
15,107.)
s ie «The same, crown view. (No. oe )
PROTEROTHERIUM BROWNII, type: Left upper teeth, outer side. (No.
9568, A. M. N. H.)
ft ag «The same, crown view. (No.
9568, A. M. N. H.)
PROTEROTHERIUM KARAIKENSE: P4—M3, left side, crown view.
From cast of vie oo
Coll.
PROTEROTHERIUM NITENS: Upper teeth, right side, crown view.
From cast of type. Amegh. Coll.
PROTEROTHERIUM DODGEI: Dp3—M2, right side, crown view. (No.
15,838.)
ao M-~z, left side, crown view. (No. 28 838.)
PROTEROTHERIUM AUSTRALE: Right upper teeth, crown view. From
cast of type of P. curtzdens. Amegh.
Coll. ; .
a «+ Right lower teeth, crown view. rom
cast of type of P. curtzdens. Amegh.
Coll. : : : :
PROTEROTHERIUM PERPOLITUM: M23, right side, crown view. From
cast of type. Amegh. Coll.
PROTEROTHERIUM PoLitumM: M&, right side, crown view. From cast
of type. Amegh. Coll.
PROTEROTHERIUM cavuM: Skull, left side. (No. 9245, A. M.N. H.)
x Occiput. (No. 9245, A. M. N. H.)
All figures natural size.
(VoL. vit)
PAGE
79
79
77
Ui
79
63
63
73
78
56
PATAGONIAN EXPEDITIONS VOL.VIL. FAVE Xe
Bruce Horsfall del Werner & Winter, Frankfort 2M
PROTEROTHERIUM
2
IBGE, ho
Fig. 1a.
iowa:
Bigs) 3:
Toca:
Jane, 5
igo:
ie, 7
Jenga,
IEE, G);
Fig. 10.
EMSA shi
JOIeR, WA,
LENGE, 03},
Fig. 14.
Imes, UG,
Fig. 152.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
EXPEANAIIOIN TOE Ee Asim xe
PROTEROTHERIUM sp.: P2—M2, left side, crown view. (No. 15,408.)
. «« The same, external view. (No. 15,408.)
PROTEROTHERIUM AUSTRALE : Right upper teeth, crown view. From
cast of type of P. mzxtum. Amegh.
Coll.
“ iz Left lower teeth, crown view. Broz
cast of typeof P. mixtum. Amegh.
Coll.
PROTEROTHERIUM PRINCIPALE : Anterior lower teeth and aaadhbrles
symphysis. From cast of type of P.
divortium. Amegh. Coll.
‘af ce 4 M3 left side, crown view. From
castoftypeofP. divortium. Amegh.
Coll.
PROTEROTHERIUM DODGE! : Proximal ends of Mc. IT and IV, desecwn,
X 34. (No. 15,838.) :
PROTEROTHERIUM INTERMEDIUM: Right lower teeth, crown view.
From castoftype. Amegh. Coll.
PROTEROTHERIUM PRINCIPALE: Mz}, right side, crown view. From
cast of type of P. dichotomum.
Amegh. Coll. ;
PROTEROTHERIUM INTERMEDIUM: Left upper teeth, crown view. (A.
M. N. H., No. 9261.)
a f Right lower teeth, crown view. (A.
MEINE Ink, IN@,; O26i.)
PROTEROTHERIUM PRINCIPALE : Right lower seemelns, crown view.
From cast of type. Amegh. Coll.
PROTEROTHERIUM BRACHYGNATHUS: Mandibular symphysis. From
cast of type. Amegh. Coll. .
a cs Right lower teeth, crown view.
From cast of type of Lzcaph-
rium prochvum. Amegh. Coll.
PROTEROTHERIUM AUSTRALE: Pz—Mg, right side, crown view. From
cast of type of P. cingulatum.
Amegh. Coll. . : :
PROTEROTHERIUM CAvUM: Young mandible, leftside. (No. 15,997.)
a6 ag Left lower milk-teeth, crown view. (No.
15,997.)
All figures, except fig. 6, are natural size.
(VOL. viz)
PAGE
80
63
. 63
65
71
65
55)
PAL VAIEN OX.
7
Its
DITIONS WOOL va
IAN EXPE
=
N
PATAGOD
ter, Frankfort OM
Bruce Horsfall del
RIUM
OTHE
a >}
IES IY,
PROT
Fig.
Fig.
Fig.
Fig.
9a.
10.
Il.
12)
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
SQ ALAINVAINCOIN, Ole? IAL AMINE, XL
PROTEROTHERIUM DODGEI, type: Right scapula, outer side. (No. 15,-
107.) .
Left humerus, dorsum (No. 35,187. )
Left ulna and radius, outer side.
(INO GF, tOW))
Left metacarpals II and I, Jozi,
(No. 15,107.)
Right femur, dorsum. (No. age)
Right patella, dorsum. (No. 15,107.)
Right patella, outer side. (No. 15,-
107.)
Right tibia and fibula,dorsum. (No.
15,107.) F :
Left metatarsus, dewsuaa, (No. 15,-
107.)
PROTEROTHERIUM CAvUM? Left manus, Hioreuen xt (No. is, oan)
ce
“cc
(<
THOATHERIUM MINUSCULUM:
the lateral digits very incomplete.
Phalanges slightly reduced from No.
5/20 sme : 6 c
The same, radial side, val 4,
PROTEROTHERIUM sp.: Right radius, dorsum.
Right ulna, radial side. (No. 15,712.)
(No. 15,712.)
Right manus, a <a2 (No:
15,393-)
All figures, except 9, 9@ and 12, three-fourths natural size.
(VOL. vir)
60
60
60
58
58
gi
dies
PATAGONIAN EXPEDITIONS VOL VIL Awa
SN
Re
Bruce Horsfall del
PROTEROTHERIUM & THOATHERIUM
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
Bx eANATIONZOR Rida aie
1. PROTEROTHERIUM PRINCIPALE: Left pes, dorsum, X;+. (No. 15,436.)
2. PROTEROTHERIUM DODGEI :
a
Riga ia:
Fig.
lene,
iow 13a5 es
Ores als ie
lanes, Gy, sf
ie, ©; ‘i
IEE 77 %
1 6c
IER, Ss
lies, | Op “
Fig. 10. e
Fig. roa. ef
[Bigs iit, e
ioe etes
Leaps, ya, ef
Riga 13: ig
Fig. 13a. as
THOATHERIUM MINUSCULUM :
(ay
The same, outer side, X 7. (No.
15,436.)
Pelvis and sacrum, wenicall view. (No.
iO 7a) nee : 5 5
Atlas, dorsal view. (No. 15,721.)
The same, left side. (No. 15,721.)
Axis, left side. (No. 15,721.) .
? Fifth cervical vertebra, anterior end.
(No. 15,719.)
Anterior thoracic vere left side.
(No. 15,719)
Median thoracic yerebrs, late ade
(No. 15,719.) ‘ : :
Posterior thoracic, a side. (No.
15,719.) .
Last lumbar, cereal view. (No. ve Tee)
Left humerus, distal end. (No. 15,721.)
Distal view of humeral trochlea.
(No. 15,721.) :
Distal view of left ulna and radiuet
(No. 15,721.) : : : ¢
Left femur, dorsum. (No. 15,719.) .
Left femur, distal view. (No. 15,719.)
Right tibia and fibula, dorsum. (No.
15,719.)
Distal view of right tibia. (No. ree
All figures, except figs. 1 and 1a, three-fourths natural size.
(VoL. VII.)
PAGE
94
95
-
Bruce Horsfall del
PROT!
PATAGONIAN EXPEDITIONS VOL. VII
BROTH!
ERIUM & THOATHI
Werner & Winter, Frankfort 7M
i oomaate
Higa:
Bien init,
Fig. 18.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
BXPLANATION OF PEADRE Dail
THOATHERIUM MINUSCULUM: P# and M4, right side, crown view.
From cast of type of 7: rhabdodon.
Amegh. Coll. : 6
60 36 4+ and 4, right side, crown view.
From cast of type of 7. rhabdodon.
Amegh. Coll. ;
THOATHERIUM VELATUM: M4, right side, crown view. Brom as!
of type. Amegh. Coll.
% a M3, right side, of same individual .
THOATHERIUM MINUSCULUM: M2, right side, crown view. From
cast of specimen in Ameghino Coll.
THOATHERIUM KARAIKENSE: M3, left side, crown view. From cast
of type. Amegh. Coll.
THOATHERIUM BILOBATUM: M3, right side, crown view. From 8
of type. Amegh. Coll.
PROTEROTHERIUM sp.: Metatarsal III, proximal end, fibular idle.
DrapraPHorus MayuscuLus: Metatarsal III, proximal end, fibular
side. (No. 15,799.) :
THOATHERIUM MINUSCULUM: Metacarpal III, proximal end, nines
stele, (INO; 15)7.))
‘ es Metatarsal III, proximal end, Foul
side. (No. 15,719.)
se s Occiput. (No. 15,721.) . ‘ ;
“ cf Right pes, dorsum. (No. 15,719.) .
sf ss Right pes, fibular side. (No. 15,719.)
a & Right lower dentition, outer side.
(No. 15,719.)
‘f a The same, crown view
: os Right upper milk dentition, outer
side. (No. 15,236.)
ee és The same, crown view
se 6 Right lower milk dentition, crown view.
(No. 15,236.)
aC a The same, outer side
s Left upper teeth, crown view. From
cast of type of Z. crepidatum.
Amegh. Coll.
ss ‘s Left lower teeth, crown view. ‘Bian
cast of type of 7. crepfidatum.
Amegh. Coll. : 3
All figures natural size.
(VOL. VII.)
PAGE
100
100
104
104
100
104
104
61
30
92
97
85
96
84
84
85
100
100
pangpetaphstithioten
ee
ee
oe
PATAGONIAN EXPEDITIONS VOL. VII
Bruce Horsfall del
THOATHERIUM, PROT!
HROTHERIUM &]
DIADIAPHORUS
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
[SPI PIL AUNUEIUOIN) Oller TRILAN INE! IW
Fig. 1. THOATHERIUM MINUSscULUM: Skull, left side. (No. 15,721.)
igew2s ss m Skull, dorsum. (No. 15,721.)
IR, Bo i S Skull, base. (No. 15,721.)
All figures natural size.
(VOL. VII.)
PAGE
85
PATAGONIAN EXPEDITIONS VOL.VIL. Jelly NBEH OANA
Bruce Horsfall del Werner & Winter, Frankfort 9M
qT]
THOATHERIUM
st
PATAGONIAN EXPEDITIONS: PALA&0O
THOATHERIUM MrNUSCULUM: Restoration of skeleton, about one-third of th
natural size . ; é 5 ; ; 3 WF tisasy cane
(VOL. VII.)
PATAGONIAN EXPEDITIONS VOL. VII. PILATE, SOV
Bruce Horsfall del Nerner & Winter, F
mg
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
PCA EAINVATTION Ole ILA, XOV IE
PAGE
THEOSODON GARRETTORUM, type: Restoration of skeleton X about+. Almost
all of the bones are from the type-specimen, No. 15,164; the vertebra
of the neck and trunk appear to form an uninterrupted series of 19, but
this is somewhat uncertain. Missing details of the vertebrae have been
supplied from 7° /allemant and, for this reason, the neural spines of the
posterior thoracic and lumbar regions have been made somewhat ‘too
heavy . j 5 : ; 5; 5 6 5 5 : : : 141
(VOL. VII.)
PATAGONIAN EXPEI
T]
S)
=
————————E——————————
F.v.lterson
PATAGONIAN EXPEDITIONS VOLVIL PLATE XVI
Werner & Winter, Frankfort 2M
Fv. lterson
THEOSODON
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
BXPEANATION TOR PE sais exaviie
PAGE
Fig. 1. THEOSODON GARRETTORUM, type: Skull, from the right side, x 3.
(No. 15,164.) . : : F 113
lehlag, ie, 3g a «Skull, base view, xX %. (No. 15,-
164.)
Fig. 10, ce “Skull stop view, <5. a(Nosmsi=
164.)
Sige, ®. t wane “ Stylohyal of right side, X 7. (No.
15,04) \ a : f 2 3 118
Fig. 3. THEOSODON LYDEKKERI: Right upper milk-teeth, X +. (No. 15,717.
m+ first molar, with valley between
internal cusps partly closed.) . : : ITI
Fig. 3a. eg Left upper first molar, X +. (No. 15,717,
with inner valley completely closed.) . 109
Fig. 4. THESODON LALLEMANTI: Right upper teeth of young animal, X +.
(No. 15,539. f* last premolar, m3 last
molar.) . : ; : : ; : 145
Fig. 5. THEOSODON GARRETTORUM, type: First thoracic vertebra, from the
right side, X 3. (No. 15,164.) . : 124
(VOL. VII.)
PATAGONIAN EXPEDITIONS VOL-VIL. PLATE XVII
(3)
B.Horsfall del Werner & Winter, Frankfort?M
THEOSODON
Tees, 1s
Fig. 1a.
lei, -2
Wiig, 2,
Bigomsa
ictus
Fig. 4a
Ig
Riga 6
Iii, 9
Fig. 8
igay 3a.
igen:
Fig. ro.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
EXPLANATION OF FRE ATE Savi iE
THEOSODON LALLEMANTI: Left half of mandible, with milk-dentition,
x3. (No. 16,002. dz last milk-pre-
molar ; 73, first molar.)
Cheek-teeth of same individual, crown
view, X +.
‘THEOSODON GARRETTORUM, type: Atlas, ventral side, X 3. (No.
15,164.) . 5 : : ae
THEOSODON LALLEMANTI: Axis, left side, X 3. (No. 15,216.)
sh = Anterior view of same specimen, X 4
THEOSODON GARRETTORUM, type: Fifth cervical vertebra, right side,
x4. (No. 15,164.) .
e & « Fifth cervical vertebra, vente
side, X 3. (No. 15,164.)
THEOSODON sp.: Three anterior thoracic vertebre, left side, X 4
(No. 15,165.) . : : : 3 :
THEOSODON GARRETTORUM, type: First thoracic vertebra, anterior
view, X%. (No. 15,164.)
THEOSODON LALLEMANTI: First lumbar vertebra, left side, X 4
(Nesms5;216)) : 5 :
‘THEOSODON GARRETTORUM, type: Sacrum, entra side, x %. (No.
15,164.) . .
“ « «Sacrum, anterior face, x4 " (No.
15,164. JL’, facets for trans-
verse processes of last lumbar
vertebra.) .
THEOSODON LALLEMANTI: Posterior part of mesosternum, dorsal side,
: x4. (No. 15,216. X, xiphisternum.)
THEOSODON GARRETTORUM, type: Left humerus, dorsal side, x ¢
(No. 15,164.)
All figures, except fig. 1a, one-half natural size.
(VOL. Vil.)
PAGE
126
127
127
129
PATAGONIAN EXPEDITIONS VOL VII. | PLATE XVII
B.Horsfall del
= n=KONSKOND NON
oY TOR) = FEN ais * es
~
"7
vee or
Fig.
Fig.
I.
2
ig. 3a.
g- 5:
PATAGONIAN EXPEDITIONS: PALASONTOLOGY.
IDCIEAIN AITO Ole IeILATM a YOR
THEOSODON LALLEMANTI: Right scapula, external side, x 3. (No.
15,216. CC, coracoid.)
. Ia. THEOSODON GARRETTORUM, type: Left scapula, distal view of slaasid
cavity, <=. (Nos 5,164. GE
coracoid.)
ag a Left fore-arm bones, X 3. (No.
15,164. A, radius; U, ulna.) .
.: Right radius, distal end, x}. (A.M. N.H., No.
9257.) ; 5 5 5 :
Right radius, preeenel srl ven (A. M.N. H., No.
9257-)
Right ulna, proximal end, anterior face, X 2 (A.
M. N. H., No. 9257.)
THEOSODON GARRETTORUM, ayn: Left Heme, deel aad. xd. (No.
(as
15,164.)
&s “Left manus, dorsum, x 4. " (No.
15,164. S, scaphoid; JZ, lunar ;
Py, pyramidal; Ps, pisiform ; 77,
trapezium ; V, vestigial fifth digit.
This figure is a composite draw-
ing made up from several indi-
viduals, chiefly Nos. oe: and
15,165.)
PY “Left carpus, proximal anil, ME
(No. 15,164.)
ss ‘Right os innominatum, right side,
<a (UNG 155144)
All figures one-half natural size.
(VOL. vil.)
PAGE
128
129
129
130
129
131
135
PATAGONIAN EXPEDITIONS VOL VIL. ey AVE ane
B-Horsfall del Werner & Winter, Frankfort?M
THEOSODON
Lhe
Fig. 3a.
Fig. 4.
Fig. 5.
Fig. 5a.
Fig. 6.
Fig. 6a.
Bigea7e
Fig. 8.
Fig. 9.
PATAGONIAN EXPEDITIONS: PALAZONTOLOGY.
EEA NATION ORE Vi ee
THEOSODON GRACILIS?: Right upper teeth, external side, X j. (No.
15,798. p+, last premolar ; 723, last molar.)
6 a6 The same, crown view, X +. ‘ :
THEOSODON GARRETTORUM, type: Right femur, anterior side, x $.
(No. 15,164.)
THEOSODON LALLEMANTI: Right femur, posterior side ad distal 40%
HIG et (ONO RAMS 74 jorie lois
lances weaseS) j : :
ot a The same, distal end, X 3.
THEOSODON GRACILIS ?: Right patella, anterior face, x3. (No. 15,798.)
THEOSODON GARRETTORUM, type: Right tibia, anterior side, x3. (No.
15,164.) :
“ “ «« The same, distal end, x4 z
‘THEOSODON LYDEKKERI: Distal half of left fibula, external side, x 4.
(A. M. N. H., No. 9269.)
Bs ‘s The same, distal end, & $
46 4 Left pes, dorsal side, a little less than one-
half natural size. (A.M. N. H., No. 9269.)
The calcaneum, astragalus and navicular
supplied from other individuals
THEOSODON GRACILIS?: Right tarsus, internal side, X %. (No. 15,-
798. JV’, plantar hook of navicular ; Cz. 7,
entocuneiform ; Cz. 3, ectocuneiform.)
THEOSODON sp.: Right astragalus, plantar side, & %. (No. 15,717.
C’, external facet for calcaneum ; C”’, sustentacu-
lar facet.) .
All figures, except Figs. 6, 6a and 7, one-half pasnral size.
(VOL. VII.)
PAGE
138
138
139
PATAGONIAN EXPEDITIONS VOL ANIL. PL/I, NOX.
B.Horsfall d
oO
THEOSODON
IT
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