£
MEMOIRS
01 THE
CAENEGIE MUSEUM,
Vol. VII. No. 6.
THE AMERICAN DICERATHERES.
By O. a. Peterson.
(Plates LVII-LXVI.)
Introductory.
At the outset the writer wishes to acknowledge his indebtedness to Dr. W. J.
Holland for much valuable assistance and advice in the preparation of the following
paper, and for permission freely to use the material in the Carnegie Museum.
To the authorities of the Peabody Museum of Natural History at Yale University
thanks are due for their courtesy in allowing me to study and illustrate the types
of Professor 0. C. Marsh. I wish to express my gratitude Xo Professor F. B.
Loomis, of Amherst, for granting me free access to his collection of types and
drawings. I wish to gratefully acknowledge the kindness of the authorities of
the American Museum of Natural History for granting me the privilege of exam-
ining the material from the John Day beds forming a part of the collection of the
late Professor Cope, and allowing me to describe a new species of the genus Dicera-
therium. Thanks are also due to the Librarian of Congress for literature for-
warded for consultation to the Carnegie Museum, to Mr. James W. Gidley, of
the U. S. National Museum, and to Mr. Harold J. Cook for information. Mr.
Syndey Prentice has carefully executed the drawings here reproduced.
399
400 memoirs of the carnegie museum.
Earlier Investigations.
A number of papers dealing with the subject of this memoir have from time
to time appeared, based upon material obtained by different parties, who in the
past two decades have worked in western Nebraska and contiguous territory.
Some of these papers possess genuine value. Other papers have also appeared,
which indicate that the study given by their authors was hasty and of only a
preliminary nature, often containing mistakes, which cause more or less difficulty
to the student. One marked error has been the attribution of specific value to
certain characters of the dentition and other parts, which after a more exhaustive
study are clearly seen to be misleading. It is hoped that the following pages may
prove to be a stimulus to further study and the exercise of greater care in this
field of investigation.
In earlier contributions relating to the Diceratheres published by the author
it has been stated that a more detailed study of the large collection obtained in the
Agate Spring Fossil Quarries would be forthcoming, after the process of extracting
the fossils from the matrix should be completed. Since that announcement much
work has been done. The writer having at his command material consisting of
the remains of some two hundred or more individuals, was induced to question the
validity of some alleged specific characters. It is hoped that the following pages
may supply safeguards against error in the future. With only a few specimens
before him, a student may establish species to his own satisfaction upon characters
selected by him at the time, but which after more abundant material is accessible
to him may prove to be invahd.
In various publications^ there have been reported to be in the Agate Spring
Fossil Quarries and their immediate neighborhood no less than seven species of
the genus Diceratherium, besides a new genus, Metacoenopus. At first glance it
might appear that the characters relied upon by the authors in estabhshing the
different forms are valid, but after a more intensive study it is found that some
species must be abandoned, and others must be regarded as doubtful. The result
of our recent investigations proves that in this case we must either condense the
number of proposed species, or establish an infinite number of additional new forms.
The latter course would be eminently unscientific, though justifiable if we accept
as valid the characters employed and relied upon in discriminating the various
1 Loomis, F. B., Amer. Jour. Sci., Vol. XXVI, 1908, p. 51-64. Cook, Harold J., Amer. Naturalist,
Vol. XLII, 1908, p. 543-545; Nebraska Geol. Surv., Vol. Ill, 1908, p. 245-247. Barbour, E. H., Science,
N. S., Vol. XXIV, Dec. 14, 190fi, p. 780-781. Peterson, O. A., Science, N. S., Vol. XXIV, Aug. 31, 1906,
p. 282-283.
PETERSON: THE AMERICAN DICERATHERES. 401
species which have been proposed. Whether the views expressed in the work
upon the Diceratheres here offered shall prove to be conclusive, can only be ascer-
tained in the light of the future. The improbability of having been able to reach
an absolutely final conclusion is abundantly realized by the writer.
Stratigraphy.
Since the earliest descriptions of the European forms of the Diceratheres by
Pomel (1853), Duvernoy (1854), and the final determination of the genus by
Marsh (1875), many papers treating of the Rhinocerotidse have appeared in America
as well as in the Old World. Through the studies of Professor Osborn and Mr.
Hatcher, based upon some early American forms, we learn that the phylum Dicera-
therince had already acquired incipient nasal horns in the White River Oligocene
of South Dakota. It is now known that the forms, not alone of Diceratherium
from the succeeding John Day beds, but all other mammalian remains available
for comparison from the same horizon of the John Day in which Diceratherium
is found, represent an earlier facies than those from the Nebraska-Dakota Miocene.
In order to give conveniently a clear view of the stratigraphic correlation
the diagram on page 402 is inserted.
The Ohgocene in South Dakota, as is well known, is much more extensively
developed than in Nebraska. It comprises, besides the three usually recognized
faunal zones, the Titanotherium beds (= Chadron beds), the Oreodon, and the
Leptauchenia beds ( = Brule beds) , two other easily recognized divisions, one the
Metamynodon beds included in the Brule beds, and the other, the Protoceras
cHfMTA- sandstones, bt)th in the Leptauchenia clays^ which arose from deposits made by
streams. The Miocene section of South Dakota falls into two (Lower and Upper
Rosebud beds), instead of the four divisions, recognized in Nebraska. The four
divisions of the Nebraska Miocene comprise the Gering, the Monroe Creek, the
Lower and the Upper Harrison. The latter is regarded by the writer as the base
of the Middle Miocene. The lower portion of the John Day beds may be regarded
as of transitional character and should therefore be classed as either uppermost
Oligocene or lowermost Miocene, the only difference being that they are not
separated from the Middle John Day beds by any apparent stratigraphic break.
The MascaU beds of the John Day are somewhat later than the Upper Harrison
beds of Nebraska, as indicated by a comparison of the faunae.
We know the earlier progenitors of Diceratherium less clearly, though it is
held that Coenopus occidentalis (Leidy) from the middle Oligocene and Coenopus
402
MEMOIRS OF THE CARNEGIE MUSEUM.
South Dakota.
Nebraska.
John Day.
European.
§
Snake River
Beds. Sand
and soft sand-
stones, thinly
bedded.
Rattlesnake
Formation.
Upper Rosebud.
Soft sandstone
and sandy clays.
Upper Harrison Base of
Massive soft Middle
sandstone. Miocene
Mascall.
Tuffs, ashes,
etc.
Upper and
Middle
Miocene.
m
Lower Harrison .
Interstratified
with harder
sandstone led-
ges.
Dicera-
therium
cooki;
D. nio-
brarense.
Columbia.
Lava, basalt,
and tuffs.
g
s
Lower Rosebud.
Soft sandstone
and sandy clays.
Dicera-
thenium.
gregorii
sp. nov.
Monroe Creek
Beds. Hard
sandstone.
Upper John
Day
Lower
Miocene
(Aquita-
nian).
Gering. Soft Dicera-
sandstones and ther. sp.
sandy clays. [
Middle and D. an-
Lower John nectens;
Day. D. arma-
ium.
Dicerathe-
rium pleu-
roceros.
Upper Brule
Leptauchenia
clay and Proto-
eeras sand-
stones.
Canopus
tridacUj-
lus; C. da-
kotensis
sp. nov.
Upper Brule.
Leptauchenia
clay.
Lower John
Day transi-
tional from
Miocene to
Oligocene.
Rhinoce-
roses,
spp. ind.
Upper Oli-
gocene
(Stampian)
Lower Oli-
gocene
(Sannois-
ian).
!5
O
O
O
O
Loiver Brule.
Heavy bedded
clays, Metamy-
nodon sand-
stones.
Canopxis
occiden-
talis; C.
copei.
Lou'er Brule.
Clays and thin
sandstone
ledges.
Protacer-
atherium.
{Dicerathe-
rium) mi-
nutum.
Chadron. Clay
and sandstones,
Titanotherium
Beds.
Chadron. Clays
and sandstones.
Titanotherium
Beds.
copei (Osborn) from the lower Oligocene (ISIetamydon beds) may be looked upon
as at least in the line of this family. -
While the general trend of the characters of Coenopus tridactylus and Coenopus
dakotensis sp. nov. is obviously in the direction of Dicer atherium, it is in the John
Day that we first recognize the genus as occurring in America. The South
Dakotan and especially the Nebraskan series of Diceratheres are a later group
belonging to the lower Miocene, closely following the species of the John Day, while
the so-called R. oregonensis Marsh is an inadequate type, which furnishes infor-
mation altogether too meager to be assigned to Diceratherium as is done by Pro-
- O.sborn, H. F., Mem. Amer. Mus., Vol. 1, 189,8, p. 164.
PETERSON: THE AMERICAN DICERATHERES.
403
fessor Loomis. Among Professor Osborn's third phylum of the later Miocene
Rhinoceroses"' we may find a representative of this phylum.
In Europe Diceratherium pleuroceros (Duvernoy) is the most completely
preserved type from the Aquitanian. Its geological horizon apparently approxi-
mates in age the John Day beds of North America.
From the cast of this European species (Fig. 1) it is seen that the cranium back
of the orbit is very suggestive of D. annectens. The brain-case has similar small
Fig. 1. Diceratherium pleuroceros (Duvernoy). From a plaster replica in the Carnegie Museum. X 1/6.
proportions, the supra-orbital ridges converge gently to form a similarly short
sagittal crest, though less prominent and more rounded in the European form.
The inion is also somewhat higher in the latter. The muzzle is long, though
higher, and perhaps having more the proportions of that part in D. niobrarense
from the Nebraska Miocene. The basi-cranium in the cast of D. pleuroceros
is short and the mastoid process is in touch with the post-glenoid process. Thus
the contour of the skull of the European species apparently has combined char-
acters of D. annectens from the John Day and of D. niobrarense from the Nebraska
Miocene. The dentition of the European form is too much worn to allow accurate
comparison. By regarding such forms as Protaceratherium* {"Diceratherium^')
minutum (Cuvier) of the Stampian as approximately parallel to Coenopus of the
upper and middle Oligocene of North America, it appears that the family may be
traced back to nearly the same geologic time in Europe and North America,^
' Bull. Amer. Mus., Vol. XX, 1904, p. 321; Ap/ieZop.s {1 Peraceras) planiceps, p. 322; Aphelops
{? Diceratherium) brachyodus p. 324.
* Abel, 0., "Kritische Untersuchungen iiber die palaogenen Rhinocerotiden Europas," Abh. der K.
K. Geologischen Reichsanstalt, Band XX, Heft 3, 1910, p. 10.
^ Osborn, Henry F., "Phylogeny of Rhinoceroses of Europe," Bull. Amer. Mus. Nat. Hist., Vol.
XIII, 1900, p. 229-267; "Age of Mammals," p. 90.
404 MEMOIRS OF THE CARNEGIE MUSEUM.
while according to recent work by European authors Prohyracodon orientale Koch
is regarded as the earUest and most primitive representative of the Rhinocerotidse.*^
Diceratherium armalum of the John Day formation has the dentition as well
as certain other features of the skull in a much less advanced stage of development
2 3
Fig. 2. Diceratherium minutum (Cuvier). M^ X i. After Cuvier.
Fig. 3. Diceratherium douvillei. M^ X i- After Osborn.
than D. annectens of the same deposit (Compare PI. LVII with text-figure 11,
also with PL LXIII, fig. 6, and PI. LXVI, fig. 1). In the latter form we naturally
might expect to meet with a greater range of anatomical variations, especially in
connection with the dentition. We may reasonably expect to find grinding teeth,
having crests ranging from those which are quite plain to those which have the
various incipient projections, as crista, crochet, anti-crochet, etc. It is far from
my mind to depreciate some, or all, of these characters; on the contrary, indeed,
it is reasonable to expect that the dentition should be one of the first parts of the
organism to undergo modification with a change in the environment. It is never-
theless questionable whether the absence or presence of a crista, a crochet, and
anti-crochet, more or less developed, or of a cingulum of greater or less prominence,
should constitute a valid specific character in Diceratherium. I very much doubt
whether these characters are of sufficient constancy to be relied upon to establish
specific distinctions in a large collection of individuals from a given locality. Stress
has in times past been laid upon the development of branches or spurs of different
lobes of the cheek-teeth. It is plainly evident that D. annectens, as the result of its
mode of life, was already in the time of the John Day more advanced, having filled
out the grinding surface of its teeth more than its contemporary, D. armatum. In
animals representing a later development in geological time, we should expect
to find similar evidence of progression, and in a large assemblage of individuals
that not all the specimens, say of D. cooki for example, are provided with crista
and crochet united on the premolars and with crista small and crochet larger on the
molars, but that these features, being in a plastic stage of development, would be
found in an endless number of combinations from those less developed to those having
more complex forms, and all within one species.
« Abel, 0., I.e., p. 24, 44-45, 49.
PETERSON: THE AMERICAN DICERATHERES. 405
Another feature, which often has been misinterpreted in connection with the
study of the Diceratheres, is the difference in the contour of the skulls. It is a well-
known fact that in individuals of almost any group of mammals the contour of the
skuU changes until well after complete maturity. Furthermore the sexual differ-
ences in the form of the skull in the Diceratheritie branch of the Rhinocerotidse are
surprising. In the early development of the phylum the difference between the
sexes was weU indicated by the form of the skull. ^ This is undoubtedly due in
great measure to the possession of the prominent nasal horns by the male. In a
young male, for instance of D. cooki, there are found the incipient horn-cores, the
nasals are quite long and pointed in front of the horns, while back of the horns
there is relatively small lateral constriction of the nasals, the temporal ridges are
generall}^ weak and not united to form a sagittal crest, the zygomatic arches are
slender, often without, or with very shght, rugosities on the posterior angles.
This is also quite generally true of the skull of an adult female, with the exception
that in the latter there is a gradation from skulls without any horn-cores in the
young, to those having incipient horn-cores in some of the fully adult and old,
and that there is considerable variation in the prominence of the temporal ridges
and the manner of their convergence before they reach the inion. I have as yet
never seen a well-developed and heavy horn-core, the ends of the nasals short and
blunt, the skull much constricted laterally back of the horn-cores, saddle-shaped on
top, with a sudden lateral expansion and heavy rugosities on the posterior angles
of the zygomatic arches in D. cooki, except in association with well-worn or very
old dentitions. It is very plain to me that more latitude should be assigned to the
significance of the contour of the skull in the genus Diceratherium than has some-
times been done. In study and comparison especial pains should be taken (1)
to ascertain whether the skull is that of a male or a female, or of the young, or
not entirely adult animal; (2) skulls of fully adult or old males are more uniform
in contour than anj^ others, and therefore more reliable in establishing species;
(3) the significance of the crushing received by the specimen in one direction or the
other should be noted.
The following table of comparisons represents fairly well the large number
of skuUs of Diceratherium cooki in the collection of the Carnegie Museum. Remains
of very young animals are not included in this table, but will be treated separately.
The object of the descriptions given under H, Nos. 2816, 2463, and 2478 in the
following table are to draw attention to the great ease by which misinterpreta-
tions may result with only a portion of the skull in hand and displaying charac-
ters, some of which may be only pathological.
' Osborn, Henry F., "The Extinct Rhinoceroses," Mem. Am. Mus. Nat. Hist., Vol. I, Part III,
1898, p. 162.
406
MEMOIRS OF THE CARNEGIE MUSEUM.
Contour of Skull compared with the Dentition.
Contour of Skull.
Dentition.
A. No. 1572. Type of D.
cooki. Old male.
B. No. 1S41. Paratype of
D. cooki. Young male.
C. No. 1923. Young male.
Skull symmetrical in the region
of the parietals, occiput, zygomatic
arches, and palatal regions, but
very slightly depressed by crushing
in the frontal and nasal regions.
Horn-cores prominent, nasals
blunt and constricted back of
horns, frontal region broad and flat,
temporal ridges moderatelj^ promi-
nent, but not united to form a sagit-
tal crest, brain-case broad, arches
suddenly expanded posteriorly,
heavy and rugose on posterior angle.
Skull comparatively broad and low.
Skull somewhat distorted by
crushing and otherwise unreliable
on account of immature age.
Horn-cores incipient, nasals pointed,
not projecting over the premaxil-
laries, due partly to crushing, a
considerable constriction of nasals
back of horn-cores; f rentals com-
paratively narrow and slightly con-
vex from side to side, due partly to
crushing and partly to immaturity.
Temporal ridges less prominent and
not united to form a sagittal crest,
but quite broadly united with the
occiput, brain case broad, zygomatic
arches expanded posteriori}' and
plainly indicating the usual rugo-
sities formed in mature males.
Skull comparatively narrow, partly
due to immaturity and partly to
crushing.
Top of skull more symmetrical
than in No. 1841, but considerable
lateral crushing has taken place,
especially noticeable in the region
of the palatines. Base of skull
open at suture and basioccipital lost.
Horn-cores incipient, nasals pro-
jecting over the premaxillaries,
more than in some specimens,
slightly less pointed anteriorly and
more constricted back of the horns
than in No. 1841; frontals convex
from side to side and proportionally
narrow, due to crushing and imma-
turity; temporal ridges quite weak
especially on right side, not united
to form a sagittal crest; brain-case
wide, zygomatic arches heavy, indi-
dicating that on further develop-
ment of the skull the rugosities
on posterior angle would be heavy
as in old males generally. Skull
comparatively narrow and high.
Dentition considerably worn.
Crista of premolars worn off, me-
dian valley on P- and P' isolated by
wear, crochet of P- and P^ united
with ectoloph, cingulum on P'^ cjuite
strong, crochet on P"* not entirely
united with ectoloph; crochet united
with ectoloph, median valley open
and post-fossette isolated on M';
crista slight, crochet heavy, and
post-fossette open posteriorly on M*;
crista weak and crochet strong on
IVP.
Permanent incisors just appearing
in the alveoli of the premaxillaries.
P' considerably worn, causing the
post-fossette to have already become
isolated. P'^ very slightly worn,
crista and crochet very slightly de-
veloped and not united on tooth
of the right side, while that on the
left side has crista and crochet better
developed and would on much wear
form an isolated medifossette; anti-
crochet slightly indicated. P^ has
crista and crochet quite well de-
veloped and united. P* is well
worn, has a small tubercle in the
median valley between proto-and
metalophs, crochet well developed,
nearly meeting the crista, which is
only slightly indicated on the tooth
of the right side. M' with well de-
veloped crista and crochet nearly
meeting to isolate the medifossette.
M^ just erupted, and shows even less
development of crista, but with strong
crochet. M' buried in the maxillary.
P' in same stage of wear as in No.
1841, P^ quite simple, no crista, a
weak crochet, which on further
wear of the tooth would practically
disappear; post-fossette very large.
P^ not as yet worn, both crista and
crochet weak, but showing a ten-
dency to unite so as to isolate the
medifossette on further wear of the
tooth; post-fossette broadly open
posteriorly. D.P^ much worn, me-
dian valley nearly isolated by wear
of proto- and metalophs; a tubercle
of small size in the median val-
ley; post-fossette isolated. M' with
double, though small, crista; crochet
heavy nearly reaching the protoloph;
post-fossette broadly open poste-
riorly. M- just starting to receive
wear, crista extremely weak, crochet
stronger than usual. M' buried in
the maxillary.
PETERSON: THE AMERICAN DICERATHERES.
407
Contour of Skull compared with the Dentition. — Continued.
Contour of Skull.
Dentition.
D. No. 2467.
female.
Fully adult
E. No. 1855. Paratype of
D. cooki. Female.
F. No. 2809. Male.
Skull somewhat crushed back-
ward and to one side, though of
quite symmetrical appearance.
Only a suggestion of horn-cores,
nasals not projecting over the pre-
maxillaries, quite long and pointed
in front of the horn-cores and very
little constricted back of them;
frontals quite broad, though slightly
injured by lateral crushing; tem-
poral ridges prominent, and remain-
ing well apart throughout to the oc-
cipital crest; brain-case large, zygo-
matic arches light. Skull propor-
tionally high and narrow.
Skull somewhat crushed to one
side.
Nasals broken well back, but the
sides do not indicate as great a con-
striction as in skulls of males.
Frontals broad; temporal ridges
quite prominent and placed quite
close together before reaching the
inion, but not forming a sagittal
crest. Brain-case broad, zygo-
matic arches light. Skull rather
broad and low, to a great extent
brought about by crushing.
Skull slightly depressed by crush-
ing.
Nasal horn-cores very robust,
nasals extend in front of premaxil-
laries, bluntly pointed anteriorly
and gently constricted back of horn-
cores; frontals broad; temporal
ridges prominent and remaining far
apart all the way back to the occi-
put. Brain-case large; zygomatic
arches very robust on the posterior
angle. Skull rather low and broad.
Small functionless and persistent
canines indicated on both sides.
P' much worn. P^ with no crista,
but a weak crochet, the latter being
double on tooth of left side; a small
antecrochet present on this tooth of
the right and left jaws and the
post-fossette nearly enclosed. P^
without crista, crochet also poorly
developed, crenulated, and post-fos-
settes isolated by wear. P^ with
weak crista and crochet. All the
premolars with strong cingulum in-
ternally. M' with no crista, but
heavy crochet, a minute tubercle in
the median valley; a large post-
fossette and no cingulum on internal
face of the tooth. IV'P with weak
crista but strong crochet, a very
minute tubercle in the median
vallej', post-fossette broadly open
and cingulum only faintly indicated
on the internal faces of the tooth.
M' has received little or no wear.
Crista and crochet very poorly de-
veloped.
P^ much worn. P- with medi-
and prefossettes quite distinct;
crochet with crenulated border,
post-fossette large. P^ quite worn,
but medifossette indicated. Crochet
nearly united with ectoloph. Post-
fossettes quite large. P'' with medi-
fossette (especially on the tooth of
right side) isolated, prefossette and
median valley united. Post-fossette
large. Premolars with heavy cin-
gulum. M' much worn, no crista,
crochet nearly united with ectoloph;
post-fossette large, cingulum weak.
M^ with strong crista and crochet
(the two nearly meeting on tooth of
right side). Post-fossette large. ]\'P
with crista and crochet much better
developed on tooth of left side,
cingulum weak on molars.
Dentition represented onlj' by P^
and P* and IVP and M^. P^ with no
crista; crochet strong, crenulated
internally and nearly united with
ectoloph. Post-fossette large. P^
with no crista, crochet strong an
crenulated, as on tooth in advance
of it. Post-fossette large. IV'P with
no crista, but strong crochet, which
on a little further wear would unite
with the ectoloph. Post-fossette
nearly isolated by wear. M^ with
prominent crista and crochet. A
tendency to develop a small tubercle
in the median valley. Post-fossette
large. The premolars have cingulum
better developed than on the molars.
408
MEMOIRS OF THE CARNEGIE MUSEUM.
Contour of Skull compared with the Dentition — Continued.
G. No. 2408. Paratype of
D. cooki. Rather young
female.
H. No. 2463. Old female
with pathological de-
formity.
No. 2816, Male.
No. 2478, Male?
Contour of Skull.
Skull somewhat depressed by
crushing, especially over the poster-
ior part of the nasals and the fron-
tals.
Nasals not projected in front of
the premaxillaries, pointed, no horn-
cores indicated, but nasals thickened
in this region ; little or no constriction
back of the thickened region; fron-
tals broad and flat; temporal ridges
fairly prominent and early united to
form a sagittal crest before the inion
is reached (the latter is broken off) ;
brain-case broad; zygomatic arches
slender. Skull proportionally broad
and low, due partly to crushing.
Dentition.
Skull crushed so as to produce an
unusually, high occiput. Frontal
and nasal regions quite symmetrical.
Anterior portion of nasals and pre-
maxilla^ broken off.
Anterior portion of skull not un-
like that of No. 1572 (type of D.
cooki) in fact the general contour is
similar. However, the sagittal re-
gion is narrower, there being a de-
cided sagittal crest in the present
specimen.
Zygoma lighter, without the ru-
gose area on the posterior angle.
The comparatively light structure
of the skull clearly indicates a fe-
male specimen.
The greater portion of skull No.
2816 is preserved, while No. 2478 is
only represented by a portion of the
top and back.
These two specimens are no less
unique than No. 2463 just de-
scribed.
The chief feature is the inflated
condition of the frontals, which is not
unlike that in Rhinoceros bicornis,
except that in the fossil specimens
the swollen area is confined more to
the posterior portion of the frontals.
In No. 2478 the inflated area is
more pronounced than in 2816 and
also differs in the median line from
the latter, 'having this inflated region
continued backward as a promi-
nent rounded ridge between the tem-
poral ridges.
Judging from the heavy and ru-
gose zygomatic arches on No. 2816
the skull is undoubtedly that of a
male.
Dentition comparatively little
worn. P' well worn. P^ with medi-
fossette isolated, especially on tooth
of right side, tiny crenulation on the
face of the crochet wall, post-fossette
widely open behind. P with medi-
fossette isolated, crenulation on
crochet as on preceding tooth, post-
fossette large. P'' with medifossette
isolated, especiallj' on tooth of left
side, post-fossette large; prominent
cingulum on internal faces of pre-
molars. M' with moderate rounded
crista and heavy crochet, but not
united to form a closed medifossette,
post-fossette broadly open poster-
iorly. M* with more prominent
crista, which very nearly unites with
the crochet, post-fossette large. M'
well erupted, but not yet in contact
with the lower teeth, crista and
crochet rather delicately developed.
Cingulum little developed on the
internal faces of the molars.
P' of left side represented only by
an e.xtremely thin band of dentine.
P^ and M' closely succeeding one
another, nearly closing up the space
for P''. This was accomplished dur-
ing the life of the animal. M' of
both sides have curious metastyles
located on the postero-internal angle,
a deep fissure separating them from
the main body of the teeth; median
valley open, but crista and crochet
well shown. Dentition much worn
(See Fig. 4.)
The dentition of No. 2816 is essen-
tially that of D. cooki, while in No.
2478 there are no teeth represented.
PETERSON: THE AMERICAN DICERATHERES.
409
In comparing (D) No. 2467 in the above table with tlie description by Dr.
Loomis of his proposed species Diceratherium schiffi it will at once be observed
that while the general contour of the skull agrees fairly well, the dentition totally
disagrees in the presence of the minute canines^ and the difference of the config-
FiG. 4. Upper dentition of Diceratherium cooki, C. M., No. 2463, showing the reduced condition of
P^ of right side and accessory tubercles on M^. X J.
uration of the grinding surfaces of the teeth. We are not permitted, therefore,
according to the usually accepted view to refer this specimen to the above pro-
posed species. The same comparison with ((?) No. 2408 shows that while the
dentition agrees, the contour of the skull is less in accordance with the above-
mentioned description, and corresponds better with the original type of D. cooki,
sexual characters excepted. With another female skull (E) No. 1855, one of the
original specimens used as a paratype in my earliest paper, D. schiffi seems to agree
best, except that the temporal ridges come closer together before reaching the
inion. It is thus seen that in comparing female skulls it is frequently found that,
dentition and contour of skull do not both agree; on the contrary the material
affords numerous different combinations. There are of course female skulls which
occasionally answer to the description by Loomis somewhat more closely than in
the cases stated above. However, it is quite obvious that we would create a
difficult task for the systematist and student, not to say a non-scientific record
of the subject, were we to establish additional species founded upon our abundant
material. The different patterns of the premolar and molar teeth which were
formerly regarded as satisfactory for the establishment of species are obviously
not to be relied upon, at least not in connection with the study of the material
from the Agate Spring Fossil Quarries. The differences to which allusion is here
* The canines are probably deciduous teeth, which sometimes abnormally persist and their presence
may be regarded as only an individual peculiarity. Professor Owen speaks of a canine in the foetal
skull of Rhinoceros indicus ("Odontography," p. 592).
410 MEMOIRS OF THE CARNEGIE MUSEUM.
made should rather be regarded as in the main due to the varying extent to which
speciahzation has operated in the individual. The teeth, especially of the smaller
American species of the Diceratheres of the Nebraskan Miocene, may be said to be
in a stage of rather rapid and progressive change. It is hardly probable that
we shall be able to perfect anj' satisfactory adaptive radiation of forms, such as
has recently been suggested,'' from the study of this material. In paleontology
we are debarred from the finer subdivisions used in recent zoology. We have to
content ourselves with characters which stand out more prominentlj- and which may
be used not only to clearly determine species, but to give aid in the question of cor-
relations of faunse and demarcations in geology. From the studj' of the collection
above tabulated, we are forced to regard the variations shown as being individual,
sexual, juvenile, and pathological.
1. Rhinoceros C?Diceratherium) pacificus Leidy," incertce sedis.
Type. — Upper molar, left side. United States National Mu-
seum.
Horizon. — ? Miocene.
Locality. — "Alkali Flat" John Day region, Oregon.
Fig. 5. Di- Paratype. — A mutilated fragment of the upper jaw of the right
ceratheriutn pa. gi^g^ with portions of the fangs of the true molars and an inferior
cificum Leidy, ^lolar tOOth.
. ,^ ' .r Horizon. — ? Miocene.
After Leicly.
Locality. — Bridge Creek, John Day region, Oregon.
As indicated in Leidy 's original description this material from "Alkali Flat"
in the John Day region, Oregon, was provisionally referred to Coenopus (R.) occi-
dentalis. Receiving more material from the same general region Leidy again
restudied the "Alkali Flat" specimens and finallj' placed them, together wdth the
material from Bridge Creek, under his species R. pacificus.
This type like that of the John Day material referred to as R. hesperius we
now find to be inadequate, or of very doubtful generic value. Leidy was appar-
ently not clear as to the true association of these different fragments and teeth.
On page 222 (I.e.) he states that the second molar described, "may be a true molar
of the preceding species" [R. hesperius] described in his report.
I am miable to agree with Dr. Loomis in accepting this species as valid and
am obliged, as the result of the study I have made, to regard this type as incertm
' Loomis, F. B., I.e., p. 53.
'» Proc. Acad. Nat. Sci., Philadelphia, 1870, p. 112; 1871, p. 248; U.S.G.S. Terr., Vol. I, 187.3, p. 221.
Plates II, VII, Figs. 6-7, 24-25; Amer. Jour. Sci., Vol. XXVI, 1908, p. 55-56, Fig. 6.
PETERSON: THE AMERICAN DICERATHERES. 411
sedis. It pertains to an animal no larger than, for instance, D. annectens (Marsh),
but that is about all I feel justified in positively stating.
2. Rhinoceros (?Diceratheriuni) hesperius Leidy," incertce sedis.
Type. — A third upper molar. Location of the type uncertain.
Horizon. — Miocene?
Locality. — ^John Day region, Oregon.
The material from the John Day of Oregon, which Leidy finally referred with
a question to the Californian species "Rhinoceros hesperius,"^" is, as Leidy himself
states, inadequate. The more important features of the remains
of the skull appear to be the position and size of the infra-orbital
foramen and the position of the base of the zygomatic process of the
jugal. Of material referred to R. hesperius Leidy says (I.e., U. S. G.
S., Vol. 1, p. 220) : "The anterior extremity of the space included by Fig- 6. Di-
, 1 !■ 1 1 J ceratherium
the zygoma extends to a hne with the mterval oi the second and hesperium.
third molars; in Rhinoceros \Coenopus] occidentalis it extends only to a (Leidy) M'.
. X - After
line with the back part of the last molar. The infra-orbital foramen Lgi^y.
is large and occupies a position above the second premolar; in R. [C]
occidentalis it is over the third premolar." This description agrees with D.
cooki so far as the zygomatic arch is concerned, but the infra-orbital foramen
of the latter species is usually opposite the interval between P- and P^ both
in D. annectens and D. cooki. In D. annectens the space included by the zygoma
referred to by Leidy is slightly more posterior. In comparing the measurements
of well-known species of Diceratherium with the figures of specimens referred
to R. hesperius and R. pacificus it is seen that M^ of hesperius might well
go with the molar of pacificus. So far as the difference in size and even the
configurations of the crowns in these teeth go, there is now no valid reason for
separating the two on the evidence produced. The tubercle of the median valley
of M' of R. hesperius may well be questioned as a specific character, and is in all
probability, as Leidy suggests, "merely an individual peculiarity." In my opinion
these remains are generically and specifically unidentifiable, but hold the historic
position of being the first material of the Rhinocerotidse obtained in the John
Day region of Oregon.
"Proc. Acad. Nat. Sci. Phila., 1865, p. 176-177; 1870, p. 112; 1871, p. 248. U. S. Geol. Surv.
Terr., Vol. I, 1873, p. 220, PI. II, Figs. 8-9. Amer. Jour. Sci., Vol. XXVI, 1908, p. 55, Fig. 5.
1- Professor Osborn has placed this Californian specimen with Coenopus platycephalus, "The Extinct
Rhinoceroses," Mem. Amer. Mus., Vol. I, 1898, p. 144.
412
MEMOIRS OF THE CARNEGIE MUSEUM.
3. Rhinoceros (?Diceratherium) oregonensis Marsh/^ incertce sedis.
Type. — Penultimate upper molar. Peabody Museum of Natural History
No. 10,002.
Horizon. — ("Pliocene deposits of Oregon") Mascal formation.
Locality. — John Day region, Oregon.
In reference to this fragment Marsh says : '. . . At the union
of the transverse posterior ridge with the outer cusp, there is a
deep cavity, nearly circular, and enclosed by a vertical cylinder
of enamel. The anterior crest, also, is divided, a strong branch
being sent inward and backward from the posterior side into the
main transverse valley."
Whether or not this specimen pertains to a Dicerathere may
never be settled. I have recently examined this tooth and may
state that it may equally well belong to a middle Miocene Rhino-
ceros (Teleoceras) . I cannot now see any reason for regarding this
type as anything except of indeterminate value.
4. Diceratherium (?) truquianum (Cope), incertce sedis.
Type. — A symphysis of the lower jaws with all the incisors and the posterior
portion of the ramus with Ms and M3. American Museum Natural History (Cope
Collection) No. 7333.
Horizon. — Lower John Day, Miocene(?).
Fig. 7. (?Di
ceratherium) Rhi
noceros oregonen-
sis Marsh.
M^ X i.
After Loomis.
Fig. S. Diceratherium truquianum (Cope). No. 7333, Coll. Am. Mus. Symphysis and portion of left
ramus. X i.
In describing an incomplete mandible from the ("Truckee beds"^*) (Lower
John Day) Professor Cope says that the specimen "supports molar, canine
[= lateral incisor], and incisor teeth. . . . The crowns of the canines [= lateral
incisors] are considerably wider than those of the incisors [= median incisors],
but do not project very far beyond them. They are sub-triangular in outline,
" American Journal Science, Vol. V, 1873, p. 410. Ibid., Vol. XXVI, 1908, p. 60, Fig. 13.
" American Naturalist, Vol. XIII, 1879, p. 333.
PETERSON: THE AMERICAN DICERATHERES. 413
having a prominent shoulder at the base on their inner side. . . . Diastema long;
ascending ramus vertical, flat in front. Depth of ramus at last molar .065; length
of crown of canine [= lateral incisor] .027; width of do. at the base .024."
This type specimen, now in the Cope collection of the American Museum of
Natural Historj^ has recently been studied by the writer. After a comparison
with fragments of the lower jaw associated with a skull (No. 10,005) of Diceratherium
armatum in the Yale Museum I think it possible that this specimen may pertain
to that species. The thick and rather shallow ramus of Cope's type is character-
istic of D. armatum. The symphysis is similarly long and heavy, the mental
foramen is below Pi, as in the latter species, and the comparative measurements
of the two specimens agree fairly well. The question of the relationship of these
two species cannot, however, be entirely satisfactorily settled until more complete
material of the John Day forms is obtained.
Additional Measurements of Type of D. truqui.\num Cope.
Antero-posterior diameter of crown of median incisor 6 mm.
Transverse " " " " " " 8 "
Height " " " " " gi "
" " lateral " 26i "
Transverse " " " " " " 23 "
Antero-posterior " " " " M^ 44 "
Transverse " a « <i << 2g "
Anterior-posterior " " " " M^ 46 "
Transverse " " " " " 27 "
5. Diceratherium petersoni Loomis^^ incertce sedis.
Type.— First and second molars of left side. Amherst Museum, No. 1583.
Horizon. — Miocene.
Locality.— Agate Spring Fossil Quarries (quarry A) Sioux County, Nebraska.
Fig. 9. Diceratherium petersoni Loomis. M^ and MMeft side. No. 1583, Coll. Amherst Museum. X i.
After Loomis.
In the extensive collection from the Agate Spring Quarries and neighborhood
now in the Carnegie Museum, there are not found any teeth or other remains
1^ Amer. Jour. Sci., Vol. XXVI, July, 1908, p. 57, Fig. 7. Cook, Harold J., Neb. Geol. Surv.,
Vol. VII, Aug., 1912, p. 40.
414 MEMOIRS OF THE CARNEGIE MUSEUM.
comparable in size with this species. On the whole the configuration of the crowns
of these teeth, as represented, does not greatly disagree with that of the type of
D. niobrarense; one of the teeth being of a considerably younger individual than
the latter. The size of the species of Loomis is, however, decidedly larger than
D. niobrarense. If this does not prove to be a very large individual of the latter
form, it maj' be a distinct species; possibly in a more direct line from the large
form D. gregorii sp. nov., of the lower Rosebud beds of South Dakota (See page 421).
6. Diceratherium armatum Marsh. ^'^ (Plate LVII and text-figure 10.)
Type. — Complete skull somewhat crushed dorso-ventrally. Bones of fore
foot associated. Peabody Museum of Natural History No. 10,003.
Horizon. — Lower John Day Formation (?Lowermost Miocene).
Locality. — Near John Day River in eastern Oregon.
As is well known, the genus Diceratherium established by Professor 0. C.
Marsh in 1875 rests on this famous specimen in the Peabody Museum of Natural
History. The type was only briefly described by Marsh. Since that time no
Fig. 10. Diceratherium armatum Marsh., No. 10003, Coll. Peabody Museum of Natural History.
Top of cranium. X j.
complete illustrations or detailed description of its osteological structure have ap-
peared. For the purpose of more detailed records the writer was accorded the
privilege of studying the type material in the Peabody Museum. The descriptions
and illustrations of the type material follow the modified generic determination
of Diceratherium and the specific characters of D. armatum.
Generic Characters Established by Professor Marsh (Modified).
Males with osseous protuberances on the anterior portion of the nasals. Females
ranging from those with light or incipient nasal protuberances to those with nasals
more or less smooth. Incisors i, Canines %-h [in rare cases a very minute canine per-
sists]. Premolars i, Molars f. Fore and hind feet functionally tridactyl.
" Amer. Jour. Sci., Vol. IX, 1876, p. 242; Ibid, Vol. XXVI, 1908, p. 54, Fig. 2.
PETERSON: THE AMERICAN DICERATHERES. 415
Specific Characters. — Diceratherium armatum may be characterized as follows :
Frontals relatively broad over the orbits. Sagittal crest short. Inion light. Broad and
heavy nasals. Anterior nares not extended as far back of the horn-cores as in D.
cooki. Muzzle and premaxillaries long. Postglenoid and paroccipital processes
well separated. Cheek-teeth comparatively simple in the configuration of their crowns.
Animals of larger size than tapirs. [?Median lower incisors proportionally large.]*
General Description. — As stated above, the type specimen of this species is
somewhat depressed by crushing. In the Peabody Museum collection is an
additional specimen, a skull with fragments of the lower jaws, re-identified by
Professor F. B. Loomis. This second specimen has the contour of the top much
better preserved. From these two specimens it is at once observed that the fron-
tals are quite broad over the eyes, which causes a rather short, sharp, emargination
of the muzzle back of the horn-cores. The latter are, as in D. niobrarense, located
near the lateral border of the nasals; they are well developed though somswhat
less in proportion to those in D. annectens of the same horizon. The nasals as a
whole are, however, heavier than in the later forms from Nebraska, D. niobrarense
and D. cooki, while one might look for evidence to the contrary. Even when the
crushed condition of the John Day type is duly considered, it seems clear that the
nasals were not elevated over the premaxillaries as high as in the later Diceratheres
from Nebraska. The temporal ridges are rather weak and the sagittal crest is
not greatly developed and occupies a smaller antero-posterior area than in D.
niobrarense. The inion is not nearly as heavy as in the latter form, resulting in
a comparatively less saddle-shaped top. The nasals are unfortunately broken off
in front of the horn-cores, but enough is present to indicate that they were of con-
siderable length and possibly terminated in a rather sharp point. The premaxil-
laries are also broken off, but what remain of them indicates that they were of
greater length than in the Nebraskan species. There is present a heavy lachrymal
process in D. armatum. The palate is broad as are also the posterior nares. The
anterior margin of the posterior nares extends even with the anterior face of M^.
The post-glenoid and paroccipital processes are well separated, indicating the
condition found in earlier Rhinoceroses. That the alveolar border of the maxil-
lary terminates more abruptly back of M^ and the paroccipital process is less
robust than in some of the Nebraskan species are perhaps characters of less im-
portance.
The dentition of the type is perhaps better known than any other part of the
* The only lower jaw of a large species with median incisors present is D. truquianum Cope. If
the latter species should prove to be identical with D. armatum Marsh, then the above specific character
is valid.
416 MEMOIRS OF THE CARNEGIE MUSEUM.
type specimen. This is due to the studies of Professor Marsh and later students.
Therefore it is only necessary to here state that the ectoloph is perhaps thinner,
the excavations or valleys of the crowns larger, and the cross-crests simpler, than
in D. annectens or later forms from the Nebraska Miocene. P' is also observed
to be proportionally large, and the cingulum seems to be well developed, especially
on the internal faces of the teeth.
A case of reversion, or at least a non-uniformity of tooth-structure worthy of
note, is seen in the second specimen of D. armatum in the Yale Museum collection
(No. 10,055). The metacone on P- of the right side of this specimen displays a
curious primitive roundness, though connected with the ectoloph by the usual
thin cross-crest, while the corresponding tooth of the opposite side has this postero-
internal tubercle of the usual type seen in the Diceratheres. There is otherwise
little or no differences in the dentition from that in the type, except that No. 10,055
represents a younger animal. The crista, crochet, etc. are very little or not at
all indicated, while the cingula are prominent, especially internally.
With the skull No. 10,055 of the Yale Museum collection, referred to D. arma-
tum, there are associated fragments of lower jaws, which undoubtedly belong
with the skull, inasmuch as the third molars, both upper and lower, are not yet
entirely developed. These fragments of the lower jaw indicate that the hori-
zontal ramus was very heavy, but rather shallow, tlie symphysis strong, the mental
foramen of large size, and located directly below Pi. The roots of the lateral
incisors indicate that the crown was large and most likely of the usual type met
with in the family. The symphysis is broken ofT too far back to show any indica-
tion of the median incisors. Pi has a rather small antero-posterior diameter, but
the crown is quite high ; the tooth is broken externally and the grinding and internal
faces are buried in the matrix. This is also true of P2. The external face of the
latter tooth shows a very heavy cingulum, which extends around the entire pos-
terior face, but has a less upward oblique trend than is seen in the later forms
from Nebraska. The crowns of the cheek-teeth are little worn, indicating the
juvenile stage of the specimen. M2 has also a cingulum on the external face which
is, however, less developed than on P2; this is especially true of the posterior lobe
of M2.
The fourth metacarpal associated with the type of D. armatum is rather long
and broad, having a comparatively small antero-posterior diameter. The bone is
somewhat crushed, but the proximal end is not distorted and indicates that the
bone was not very thick fore-and-aft. The distal trochlea extends well up upon
the anterior face of the metacarpal. Judging from the unciform, which is present,
the carpus was fairly high.
.145
.112
Pi (greatest diameter) .
PETERSON: THE AMERICAN DICERATHERES. 417
Measurements op the Type of Diceratherium armatum
Length of skull from condyles to end of nasals as preserved (Points of nasals broken off) 503 mm
Length from occipital condyles to M^ •
M3 to end of maxillary (Point of maxillary broken offi approximately: '. '. 'Z "
Greatest width across the zygomatic arches ' .
Greatest transverse diameter of occipital condyles
Transverse diameter of occipital plate
Inferior surface of condyles to end of inion . . . ^^^
Length of dentition (molar-premolar series) l^^
Antero-posterior diameter of pi ^"^^
29
24
31
40
35
45
38
49
44
53
53
53
45
Length of Mc IV ^°
-1 Q'7
Greatest transverse diameter of head of Mc IV
Transverse diameter midway of shaft of Mc IV
Antero-posterior diameter of shaft of Mc IV (approximately) , .
Height of unciform
Transverse
" " pi
Antero-posterior
* * ti ■p2
Transverse
" " p2
Antero-posterior
' " pa
Transverse
' " ps
Antero-posterior
" p*
Transverse
' " p4
Antero-posterior '
" Ml
Transverse '
" Ml
Antero-posterior '
" M^
Transverse '
" M2
Antero-posterior
" M^
Transverse '
" M3
51
40
54
7. Diceratherium annectens (Marsh).'^ (Plates LXIII, Fig. 6; LXVI, Fig 1
and text-figs. 11 and 11a.) (See PL LVIII, Figs. 1, 2, 3.)
Synonym.— Diceratherium nanum (Marsh). ^^
Type.~A set of superior premolars of the left side; one superior incisor asso-
ciated. Peabody Museum of Natural History No. 10,001.
Hypotypes.-Skull nearly complete. Cope Collection, American Museum
Natural History, No. 7324, a male. Front of skull and lower jaws of Professor
Marsh's type D. nanum in the Marsh Collection, Peabody Museum of Natural
History, No. 10,004, a male.
Horizon.—Lower to Middle John Day Formation.
Locality.— l<iear John Day River in eastern Oregon.
ion« " ^Jt' ^' ^" ^"'" ^°"- ^''■' ^°'- ^' ''"'' P- ^- L°°"^'«' F- B. Amer. Jour. Sci., Vol. XXVI
1908, p. 54, Fig. 3. '
i« Marsh, 0. C, Amer. Jour. Sci., Vol. IX, 1875, p. 243.
418
MEMOIRS OF THE CARNEGIE MUSEUM.
Specific Characters. — Premaxillaries long and slender. Nasals and nasal horn-
cores of males broad and heavy. Muzzle long. Anterior naves excavated back of the horn-
cores in the same proportion as in D. arniatum. A well-defined and quite heavy sagittal
crest. Occiput overhanging, and the cranium well extended back of the posterior angle
of the zygomatic arches. Liberal separation between the postglenoid and paroccipital
processes. First premolar relatively large. Cheek-teeth with swollen cross-crests
and crowns otherwise complicated; crista and crochet present, especially on the pos-
terior premolars and the molar series. Median and lower incisors proportionally
large. Animal about the size of, or larger than, a tapir.
General Description of the Type Material.
From recent studies of the type material of Professor Marsh's collection in
the Peabody Museum and the splendidly preserved skull in the Cope Collection of
the American Museum there is now no valid reason for regarding the types of
Fig. 11. Diceratherinni annectens (Marsh). No. 10001, Coll. Peabody Museum of Natural History.
Premolar teeth of left side and superior incisor. X i-
D. annectens and D. nanum as belonging to separate species. D. annectens, having
been described before D. nanum, and also being now found to possess sufficient
characters for identification and comparison, must be regarded as the type.
In his description of D. annectens Professor Marsh was apparently not entirely
clear as to the composition of the specimen. Professor Loomis correctly associates
the type, but mistook some of the premolars for molars.
There is no doubt in the mind of the present writer that this series of pre-
molars belongs to one individual. In placing the teeth together one finds that
they fit against one another perfectly and the grinding surfaces form a natural
gradation generally obtained in specimens of D. cooki which have reached an equal
stage of wear. Whether or not the associated incisor tooth belongs to the type
is less satisfactorily determined, as it has received comparatively little wear and
appears small in proportion. The small amount of wear of the upper incisors
is, however, often found in skulls of D. cooki, when the cheek-teeth have been well
ground down.
PETERSON: THE AMERICAN DICERATHERES. 419
pi is very much worn, so that its configuration is practically obliterated.
P^ is also much worn, but plainly indicates that the cross-crests are more swollen
than in the larger species, D. armatum, so that on extreme wear of the tooth the
two crests become almost united internally and more nearly approximate the
condition in the Nebraskan form D. cooki; there is a shght indication of a crochet
in P^ P^ has the internal portion of the cross-crests even more closely united,
so that on extreme wear the tooth has a remarkably close similarity to that in
D. cooki. There is, however, no crochet shown in this worn tooth; the crista might
be said to be represented by a heavy fold on the inner face of the ectoloph. P^ in
its general characters is practically a repetition of P^ except that the crista and
crochet are more plainly shown. The crochet of P^ of this species represents,
undoubtedly, the most external process of the comb-like plate on the posterior
border of the medifossette in D. cooki; that is to say, the true crochet, which imites
with the ectoloph on extreme wear of the tooth. In the forms of the John Day it
appears that this crochet does not entirely unite with the ectoloph.
No. 10,004 of the Yale Museum CoUection (Marsh's type of D. nanum)
is laterally compressed by crushing. As a consequence the nasals appear less
broad than otherwise would be the case, and they are also possibly somewhat
lengthened by crushing. The horn-cores are well-developed and the points of
the nasals are quite heavy, and extend well in front; their tips are broken off.
The nasals as a whole are heavy and are elevated above the premaxillaries much as
in later forms, thus presenting large anterior nares. The infra-orbital foramen is
large, well up upon the maxillary and its posterior margin is opposite the middle
of P^ The premaxillary is long; it is also slender, though somewhat heavier than
in the later forms from Nebraska. There is a large upper incisor of the usual
cutting pattern. The premolars are very much worn.
The lower jaws of the same specimen are also slightly crushed laterally.
The most noteworthy feature of these jaws are the proportionally large median
incisors and the long diastemata from the cheek-teeth to the incisors. The lateral
incisor is robust, well sharpened by wear and procumbent in position. The cheek-
teeth are much worn, indicating the senility of the individual. There is a fairly
well developed cingulum on the lower premolars (PI. LVIII, Figs. 1-3.)
As in the lower jaw of D. armatum, the ramus is quite heavy, but somewhat
deeper in proportion. The internal face is also less convex supero-inferiorly.
This latter character may in part be due to crushing.
As stated above, the skull (No. 7324 Cope Collection) in the American Museum
is by far the best of the three specimens here described. (See Pis. LXIII Fig. 6;
420
MEMOIRS OF THE CARNEGIE MUSEUM.
LXVI, Fig. 1 and text fig. 11a.) From this material combined we are now in pos-
session of practically all the anatomy of the skull of D. annectens. With the
exception of the ends of the nasals, the anterior portion of the left horn, and the
points of the premaxillaries this specimen is quite complete. The skull is somewhat
depressed, so that the region about the horns and anterior portion of the maxil-
laries appears broader than in the New Haven specimen described above; however,
the present specimen is in reality more robust. In proportion the horn-cores
of D. annectens from the John Day are considerably heavier than in the later Ne-
braskan species and the tips of the nasals were evidently quite long. The constric-
FiG. Ho. Diceratherium annectens (Marsh). No. 7324, Cope Collection, American Museum of Natural
History. Hypotype. X i-
tion between the orbit and the nasal horn is, as in D. armatum, much shorter and
sharper than in D. niobrarense or D. cooki, and the occiput extends further back of
the posterior angle of the zygomatic arch and overhangs the occipital condyles
to a greater degree. There is also a well-defined and quite heavy sagittal crest.
The supratemporal ridges are distinct, but more gently oblique or more gradually
converging towards the sagittal crest than in the Nebraskan species, which is
due to the smaller brain-case in the form from the John Day. The occiput is
somewhat more elevated above the occipital condyles and the transverse diameter
of the occipital plate is actually less, though the skull is larger than that of the
average skulls of D. cooki found in the Nebraskan quarries. As stated, the pre-
maxillaries are broken off anteriorly, but it is very evident that the diastema from
the cheek-teeth to the upper incisor in this specimen was as long as in the type
at New Haven. The pre-orbital foramen is located above the anterior, or rather
the middle, region of P^ as in D. cooki, but it is further back of the narial border,
PETERSON: THE AMERICAN DICERATHERES. 421
due to the longer muzzle of the form from the John Day. The zygomatic arch of
the latter is somewhat lighter, especially at the posterior angle, which forms a
less direct right angle with the side of the skuU and is not nearly so rugose. The
region back of the pterygoid processes is decidedly longer in the John Day species
than in the eastern species. Thus there is a wide separation between the post-
glenoid and paroccipital processes in the earlier species, while in the later form
(D. cooki) these processes are closely united. Even the occipital condyles of the
John Day specimen are less sessile. The anterior margin of the posterior nares
is opposite the interval between M^ and jV'P as in the smaller Nebraskan form,
D. cooki, and the size of the nares is of the same proportion.
The premolars of the specimen in the American Museum are even more worn
than in the type, which is brought out in the illustration, PL LXIII, Fig. 6. They
are, however, not too far gone for identification and comparison, and they are
seen to agree with the type in New Haven. ISP has a decided antecrochet-like
swelling of the anterior lobe, which is as great as, or perhaps greater than, in any
of the Nebraskan specimens which I have seen. The crochet is of quite large
size and totally separated from the ectoloph, so that at no stage of wear wiU this
process apparently ever become imited with the ectoloph as in D. cooki. M^ has
the crochet generally less developed than in D. cooki. M^ has on the right side a
curious basal cusp on the posterior margin of the exit of the median valley which is
very similar to the same tooth in a specimen of D. cooki at the Carnegie Museum,
though less deeply separated from the main body of the tooth. (See Fig. 4, p. 409.)
On M^ of the left side there is also a minute tubercle situated in a position similar to
the one described above. With the exception of the relative size of the median
incisor and the first premolars D. annectens from the John Daj' and D. cooki from
the Nebraska Miocene differ less in the detailed structure of the dentition than
was anticipated.
On page 422 are tabulated measurements of the specimens above described.
8. Diceratherium gregorii^^ sp. nov. (Plate LI X and text-figure 12.)
Type. — Skull,? female. American IVIuseum, No. 12,933.
Horizon. — Miocene, Lower Rosebud beds.
Locality. — Near Rosebud Indian Agency, South Dakota.
Specific Characters: Occiput low, but overhanging, as in the John Day form
{D. annectens) Sagittal crest low, but well defined. Postorbital ridges converging
very gradually, as in the John Day form, but the brain-case proportionally larger in
size. Greater robustness of the inion, shorter basicranium and premaxillaries, when
" In honor of Dr. W. K. Gregory, of the American ^Museum of Natural History, who found the type-
422
MEMOIRS OF THE CARNEGIE MUSEUM.
Measurements of D. annectens.
Length of skull from inion to broken points of nasals
Occipital condyles to and including P'
Occipital condjdes to M^
Greatest transverse diameter of skull at posterior angle of zygomatic
arches
Transverse diameter of occipital plate. (Measurement taken
superiorly)
Antero-posterior diameter of P', - and '
Length of upper dentition
Length of premolars
Length of molars
Antero-posterior diameter of P'
Transverse
Antero-posterior
Transverse
Antero-posterior
Transverse
Antero-posterior
Transverse
Antero-posterior
Transverse
Antero-posterior
Transverse
Antero-posterior
Transverse
Length from P, to and including the lateral incisor . .
Length of P2 and P3
Length of P2
Length of P3
Antero-posterior diameter of crown of median incisor.
Transverse diameter of same
P'..
P^.
P^.
P'..
P-'..
P^..
P^..
Ml.
Ml.
M^
M2.
M3.
M'.
Type, Y.M.
No. 10001.
95 mm.
21 mm.
17 mm.
23 mm.
27 mm.
27 mm.
34 mm.
29 mm.
38 mm.
Neotype,
Y. M.
No. 10004.
*19 mm.
*1S mm.
*23 mm.
*2S mm.
110 mm.
48 mm.
23 mm.
26 mm.
8 mm.
6 mm.
Neotype,
A.M.
No. 7324.
410 mm.
368 mm.
185 mm.
235 mm.
83 mm.
63 mm.
185 mm.
93 mm.
98 mm.
19 mm.
17 mm.
24 mm.
*28 mm.
28 mm.
35 mm.
30 mm.
39 mm.
35 mm.
41 mm.
40 mm.
41 mm.
33 mm.
38 mm.
* Approximate measurements.
com'pared with the John Day species, D. annectens. Paroccipital and postglenoid
processes in close proximity to one another as in D. niobrarense. Border of anterior
nares extending further back than in the latter species. Animal considerably larger
than tJie tapir.
General Description.
The tj^pe specimen was discovered by Dr. W. K. Gregory of the American Mu-
seum party of 1906. The skull is somewhat depressed by crushing, which fact
has been taken into due consideration. That the cranium may probably be that
of a female should also be noted. The animal was of advanced age, as the den-
tition is greatly worn down and of no practical service for specific determination.
There is no true contact between the broken end of the premaxillary and the
maxillary bone in the type at present, but Dr. W. D. Matthew assured me that it
was complete when discovered, and that the length of the premaxilla is not far
from correct as restored. (See PL LIX). Whether or not there was a lateral
incisor, as in Ccenopus tridactylus from the Protoceras beds, cannot positively be
PETERSON: THE AMERICAN DICERATHERES. 423
determined from the type. It is, however, most probable that this tooth is wanting,
especially when we consider the proportionally small development of the premaxil-
lary in the type, which is apparently much lighter and is no doubt shorter than,
for instance, in Coenopus tridadylus of the upper Oligocene. The later geological
formation in which this new species was found is also to be considered. The
Fig. 12. Dicer atherium gregorii. No. 12933, Coll. Amer. Museum. Top of cranium. X i
nasals were apparently of considerable length in front of the very slight swelling
on the anterior portion of the nasals. The crushing of the anterior region of the
skull gives to the anterior nares an unusually low position, low even when proper
allowance is made for the distortion which has occurred. This may, or may not,
be a valid character. The postorbital ridges of the frontals converge very grad-
ually, somewhat as in the John Day form {D. annedens), but the brain-case is
somewhat larger in proportion. The sagittal crest is low, but well-defined, and
the inion is intermediate between the John Day form and D. niobrarense of the
Nebraska Miocene, that is to say, the rise from the sagittal crest proper to the
top of the inion is very much more gradual than in D. niobrarense, even when the
difference of sex and the crushing sustained by the specimen is taken into account,
thus more like what is seen in D. annedens, but the slight emargination on the
posterior face of the inion is more as it is in D. niobrarense. The inion itself is
less rugose and the lambdoidal crests are thinner than in D. annedens, which may
be a sexual character. The top of the skull when in perfect condition was on the
whole less saddle-shaped; the zygomatic arches lighter, less prominent posteriorly,
and united with the sides of the squamosals more obliquely than in D. cooki. The
postglenoid and paroccipital processes are in touch with one another, but are
not so completely fused as in the latter species. The external ear is large and in
shape more nearly as in Z). niobrarense.
The incisor present in the premaxilla is of unusually small size in comparison
with the cheek-teeth and the size of the skull. P^ has about the same relative
424 MEMOIRS OF THE CARNEGIE MUSEUM.
size as in D. niohrarense. As stated above, the clieelv-teeth are much worn. The
last molar does not indicate any crochet or crista as in the last named species; the
cingiilum is, however, equally prominent. M^ on the right side has a small cone in
the median valley.
It is very Hkely that the above specific characters may be modified, or added
to, when more material representing both sexes of this species is obtained.
Measurements.
Greatest length of skull from inion to the end of the premaxillaries approximately 510 mm.
From occipital condyles to anterior end of maxillary, approximately 490 "
Occipital condyles to P' 362 "
Occipital condyles to M' 230 "
From incisor to orbit 197 "
From orbit to occipital condyles 310 "
Incisor to and including M' 266 "
Greatest transverse diameter of skull at posterior portion of zygomatic arches 258 "
Greatest transverse diameter of frontals 191 "
Greatest transverse diameter at constriction back of the enlarged portions of the nasals 97 "
Length of molar-premolar series 217 "
Length of premolar series 102 "
Length of molar series 119 "
Antero-posterior diameter of P' (greatest diameter) 21 "
Transverse " " P^ " " 20 "
Antero-posterior " " P^ " " 26 "
Transverse " " P^ " " 32 "
Antero-posterior " " P' " " 31 "
Transverse " " P^ " " 44 "
Antero-posterior " " P^ " " 34 "
Transverse " " P^^ " " 48 "
Antero-posterior " " M^ " " 38 "
Transverse " " M' " " 45 "
Antero-posterior " " M^ " " 45 "
Transverse " " M^ " " 47 "
Antero-posterior " " M^ " " 38 "
Transverse " " M' " " 44 "
Antero-posterior " " crown of incisor 19 "
Transverse " " " " " 9 "
9. Diceratherium niobrarense Peterson.-" (Plate LX, Fig. 2; PL LXI, Fig. 2;
PL LXII, Fig. 2, and text-figure 13.)
Synonym. — M. {Aceratherium) egrerius}^
» Science (N.S.), Vol. XXIV, 1906, p. 28; Ann. Car. Mus., Vol. IV, 1906, p. 46, Pis. XIII-XIV;
Loomis, F. B., Amer. Jour. Sci., Vol. XXVI, 1908, p. 56.
^' Loomis, F. B., ibid., p. 61 [Aceratherium egrerius]; Cook, Harold J., Amer. Naturalist, Vol. XLII,
1908, p. 543, 2 figs [Aceratherium egregius]; [Metacoenopus egregius]; Neb. Geol. Surv., Vol. Ill, 1908,
p. 245, PI. I.; Vol. VII, 1912, p. 41.
PETERSON: THE AMERICAN DICERATHERES. 425
Type— QkuW of young male. C. M., No. 1,271.
Horizon. — Miocene.
Locality. — Agate Spring Fossil Quarries (Quarry A.) Sioux County, Nebraska.
Paratype. — Posterior portion of skull from same quarry as the type. Ver-
tebrae and limb-bones referred to same species.
Specific Characters. — Premaxillary somewhat reduced in length. Grinding
surface of cheek-teeth comparatively simple. Nasals long in front of the horn cores
especially in females. Muzzle long. Border of anterior nares comparatively little
extended backward. Skull quite saddle-shaped, especially in males, due to the develop-
ment of the horn-cores and the high inion. Postorbital ridges less oblique than in the
John Day forms due to the enlargement of the brain-case. A sagittal crest present;
this is proportionally long, but not especially strong. Zygomatic arches somewhat
more expanded posteriorly and the basi-cranium shorter than in earlier John Day
forms. Par occipital and postglenoid processes sometimes touching one another at
their bases so as to enclose the external auditory meatus. Lower jaws heavy and the
angle little or not at all everted. Animal smaller than D. armatum of the John Day
formation.
General Description.
Since the earlier descriptions of this species the type has been restudied.
Illustrations, which in some respects are more accurate than those which appeared
earlier, are also herewith presented. I, furthermore, add data recently obtained,
and have corrected certain errors, which occurred in earlier publications.
In Science (I.e.) it was stated that the nasals were found in the talus below the
point where the skull was taken out. The nasals were separated from the skull at
the fronto-nasal suture, but agree with the skull found in situ, with the correspond-
ing parts missing. I at once associated the different parts as those of one indi-
vidual, and have not since found any reason for changing my mind. Confirming
my view, a good skull of this species in Dr. Loomis ' collection at Amherst has the
fronto-nasal suture quite open, as in the type. Dr. Loomis assures me that the
nasals belong with the skull of his specimen, which is of approximately the same
age as the type. (See Fig. 13.)
In the original description it was said that the brain-case is large, while Loomis
states that the brain-case is comparatively small, a statement which only holds
good so far as the present species and D. cooki are concerned. From the earlier
John Day forms D. niobrarense may be distinguished by its having the brain-
cavity of larger size. I stated that there is a well-formed sagittal crest, but I did
not especially emphasize the fact that the crest is strong. From the Amherst
426 MEMOIRS OF THE CARNEGIE MUSEUM.
material it appears that there is some variation in this respect, judging from the
statements of Dr. Loomis. The statement made by the latter author that the
nasals project considerably beyond the horn-cores is characteristic of this species,
while in D. cooki the points of the nasals are much abbreviated in fully adult or
old males.
The muzzle of the skull in D. niobrarense is apparently not shorter than in the
John Day forms, while the constrictions back of the horn-cores and in front of
the orbits are longer and gentler, due to the relative narrowness of the nasals
across the horn-cores and the narrower frontals. The location of the infra-orbital
foramen is similar to that in D. armatum, located well back from the border of
Fig. 13. Diceratherium niobrarense Peterson, No. 1022, Coll. Amherst Museum. X h After an
outline drawing by Dr. F. B. Loomis.
the anterior nares due to the slight backward excavation of the latter. The
occiput is, however, not overhanging, as in the John Day forms, while the external
ear is sometimes enclosed below.
As has been shown by Loomis and Peterson the molar-premolar dentition of
D. niobrarense is more primitive than in D. cooki, and more nearly like that of
D. armatum. In the latter species, which is clearly an older and rather primitive
type, we find that P' is somewhat larger, the ectoloph of the grinders is thinner,
the different valleys wider, and the cingulum perhaps somewhat more prominent.
To judge from the scanty remains of D. armatum which we possess, it certainly
is indicated that the crista is practically wanting, while the crochet is in a very
much more rudimentary stage of development on the teeth of the latter species
than in D. niobrarense.
In comparing the descriptions and figures of Aceratherium egrerius, later
called Metaccenopus (I.e.) by Mr. Harold J. Cook, it is very evident that the remains
of an adult female of Diceratherium niobrarense has been used as the type. Cook
admits that there is a "thickening of the nasals at the point where a horn usually
occurs in the Rhinocerotidse, which may indicate a rudimentary horn." Indeed
one should expect to find this thickened condition, and we usually do find it in
petkrson: the American diceratheres. 427
the young males and in female skulls of D. cooki of more adult stages. It appears
that in males of D. niobrarense the nasal horn-cores are located more laterally and
point more outward,-- while in D. cooki they are nearer the median line and point
more directly upward. (See PL LXII.)
With the exception of the longer nasals in front of the thickening portion or
the incipient horn-cores (undoubtedly a sexual character), Mr. Cook's description
agrees quite well with the type of D. niobrarense.
The premaxillaries are complete in this splendidly preserved specimen in
Mr. Cook's collection, and show some reduction in length from those in the older
John Day forms.
There is a considerable portion of the left mandible in Mr. Cook's specimen,
which was found in an articulated position on the skull. Cook states that this
mandible is "heavier and lacks the outward turn or flange commonly found in
the Diceratheres." A splendid pair of lower jaws in the Loomis collection at
Amherst (see Fig. 14) referred to D. niobrarense also agrees with the characteri-
FiG. 14. Diceratherium niobrarense Peterson, No. 1022, Coll. Amherst Museum. Internal view of
ramus. X i- After an outline drawing by Dr. F. B. Loomis.
zation in Cook's paper, and plainly indicates that the masseteric muscle was
much less developed in this species. Unfortunately the outline drawing kindly
furnished by Professor Loomis from the Amherst specimen does not indicate the
external view of the mandible.
The atlas and axis of Mr. Cook's specimen were found attached to the occipital
condyle and are so illustrated in his paper. No description in detail of these
vertebrae is, however, furnished.
A series of cervicals (atlas, 3d, 4th, and 6th), an anterior dorsal (?5) and three
lumbar vertebrae were found isolated in the same quarry (quarry A) in which
the type of D. niobrarense and the Amherst material was found. These bones,
No. 1910, are here provisionally referred to D. niobrarense, inasmuch as the size
^^ Figures on Plate I of Cook's illustrations show admirably well these lateral eminences although of
an incipient stage most likely due to sex. Cook states that there is no double-horn tendency in his type.
428
MEMOIRS OF THE CARNEGIE MUSEUM.
corresponds very well to the type. All these vertebrae, except the atlas, are more
or less mutilated, but enough is preserved to show that they are very similar to
those bones in D. cooki, size excepted. In its proportions the atlas referred to is
not unlike that of the smaller form {D. cooki), save that the transverse process
is less extended forward and is somewhat heavier, especially along the terminal
border. A second marked difference of this bone in the two species is the presence
Fig. 15. Diceratherium niobrarense Peterson, No. 1910, Coll. Carnegie Museum. Anterior and ventral
views of atlas. X i-
in D. niobrarense of a round venal foramen, (remnant of the inferior exit of the
vertebraterial canal) on the ventral face at the base of the transverse process, and
a strong antero-posteriorly directed ridge immediately internal to the foramen.
While there is in D. cooki a groove and occasionally a minute foramen, located
in the same position as the foramen described on the atlas of D. niobrarense, there
is found no evidence of the ridge in D. cooki. If the heavy terminal border of the
transverse process and the venal canal are constant in D. niobrarense, this may be
regarded as an additional specific character. (See Fig. 15.) The third cervical
PETERSON: THE AMERICAN DICERATHERES. 429
has the ventral keel of the same proportions as in the smaller species, and the same
faintly indicated neural spine, and the strong transverse process similarly expanded
laterally. Cervical four has the neural spine as prominent, but the back part of
its transverse process is perhaps somewhat heavier than in D. cooki. Cervical six
again has the same downwardly directed inferior lamella of the transverse process,
which is, however, proportionally less developed fore-and-aft than in D. cooki.
The dorsal vertebra referred to presents the same characters as the corresponding
bone in the latter species, including the mammillary process on the upper anterior
surface of the transverse process. With the exception of a somewhat more de-
cided ventral keel and possibly a lighter spine, the lumbar series associated are of
approximately the same relative size and detailed structure as in the smaller form,
D. cooki.
The remains of the limb-bones (No. 1910) which were found in this same
quarry, and are provisionally associated with the type of D. niobrarense, show that
the scapula is proportionally shorter than in the smaller species, and possibly also
somewhat broader; the coraco-scapular notch shorter and shallower; the bicipital
groove of the humerus smaller; and the shaft of the ulna straighter. The propor-
tionate length of the femur cannot positively be ascertained from the material at
hand, but the tibia is decidedly shorter. The remains of the foot-bones asso-
ciated bear no marked differences from those of D. cooki, except their larger size.
The type (No. 1040) of " Metacoenopus" (Aceratherium) stigeri in the Amherst
College Museum is described by Dr. Loomis, and the right upper molar-premolar
series is illustrated. Dr. Loomis says: "The small skull is elongated, light in
build and rather narrow. The orbit is large and the zygomatic arch light. The
premolar teeth are crowded, there being neither an anterior nor posterior cingulum,
though one is developed along the inner face around the protocone, running out
on the hypocone. Crista and crochet are wanting on these teeth of a rather old
individual, except that on the fourth premolar there is a faint trace of a crista,
and on the third premolar a small antecrochet is developed. On the molars the
cingulum is reduced as in the premolars, and both crochet and crista are wanting.
The protocone, however, is swollen, making a considerable fold as in European
Diceratheres. A. stigeri is closely related to A. egrerius but is smaller, and has
the cingulum on the premolars and the crochet on the molars less developed."
In the description of this complete skull the greatest stress is laid on the
configuration of the grinding surface of the teeth, principally for the purpose of
comparison. The illustration indicates an animal of old age, as Loomis states.
The crista, if there was one, has consequently disappeared by wear. The crochet
430 MEMOIRS OF THE CARNEGIE MUSEUM.
most likely has likewise disappeared, or rather united with the ectoloph, while
the cmgiilum may be lighter or even wanting. The cingulum has united (by the
wear of the tooth) with the internal border of the grinding face, especially on the
posterior portion. It is very e^^dent, from the enclosed post-fossette that the
dentition illustrated by Loomis is very much more worn than that of the type of
D. niobrarense. Finally through the courtesy of Professor Loomis. I had the
opportunity of restudying his type and find that the Amherst specimen as well
as the description agree quite well with the average old female skulls of D. cooki
in the Carnegie Museum.
Measurements of the Type of D. niobrarense.
Greatest length of :<kull, approximately 450 mm.
Length of skull from occipital condyle to and including P^ 370
Length of skuU from occipital condyle to 'SP 190
Greatest transverse diameter of skull 235
Greatest transverse diameter of brain-case 130
Greatest transverse diameter of frontals 150
Greatest transverse diameter of occipital condyles 103
Greatest transverse diameter of palate 68
Vertical diameter of the orbit 60
Length of 2d, 3d and 4th premolars and the molar series 185
Antero-posterior diameter of P- 26
Transverse diameter of P" 29
Antero-posterior diameter of P* 32
Transverse diameter of P^ 36
Antero-posterior diameter of !NP 39
Transverse diameter of !NP 37
Antero-posterior diameter of M' 35
Transverse chameter of ^P 39
Scapula, appro.ximate height 280
Humerus, length 340
Tibia, length (Xo. 1910) 335
Tibia, length (Xo. 1910a) 310
Tarsus, height tuber of calcaneum not included, approximately 85
Tarsus, length of tuberosity of calcaneum 58
Metatarsal II. length 130
Metatarsal III, length 145
The occurrence of the material of the above described species in the Agate
Spring Fossil Quarries is of considerable interest. Diceratherium luobrarense
has only been found in Quarry A. The remains of this species may be said to be
practically absent in the representative fauna of the quarries in the Carnegie or
the University Hills (See ^Mem. Car. ]Mus. Vol. IV, Fig. 1, p. 205), while similar
PETERSON: THE AMERICAN DICERATHERES. 431
remains representing D. cooki of these latter quarries are quite as abundantly
mingled with the remains of D. niohrarense in Quarry A. The latter quarry is
only a very short distance (300 yards) to the north of the main quarries and may
possibly represent a somewhat earlier time; or, more probably, the sediments
accumulated at this spot represent a different stream, which had its origin in, and
flowed through a locality more favorable to this species.
10. Diceratherium cooki Peterson.^^ (Plates LX, LXI, LXII, fig. 1, LXVI,
figs. 2, 4).
Synonyms. — Diceratherium arrikarense Barbour; D. schiffi Loomis; Acera-
therium stigeri Loomis; Diceratherium aberrans Loomis; D. loomisi H. J. Cook.^*
Type.— 8k\x\l of old male. CM. No. 1572.
Paratypes. — Eight skulls, a number of lower jaws, and other skeletal material
C. M. Nos. 1573, 1575, 1581, 1841, 1848, 1853, 1855, 1888, 2408, 2443, 2799.
Specific Characters. — Skull, especially of males, short and broad in its proportions.
Median lower incisor small. Crowns of the upper cheek-teeth complicated. Crochet
often uniting with ectoloph in much worn teeth. Muzzle short. Horn-cores of males
prominent, but nasals not broad across the horns, and ends of nasals abbreviated.
Females varying from those with no horns to those with incipient horns. Postorbital
ridges seldom entirely meeting to form a sharp sagittal crest. Brain-case large. Occi-
put quite broad, of moderate height, and not overhanging. Premaxillaries short.
Margin of anterior nares much excavated, extending well back of the horn-cores and the
infra-orbital foramen situated close to the border. Posterior point of zygomatic arch
greatly expanded laterally and covered with heavy rugosities in fully adult or old males.
Basicranium short. Post-glenoid and paroccipital processes united to enclose the
external auditory meatus. Animal considerably smaller than D. niobrarense.
General Description.
Skull.
As stated in the original description, this species rests on a number of skulls,
lower jaws, and other skeletal material from which a male skull No. 1572 was
originally selected as the type. In the first description it was stated that "the
occiput is rather low, . . . the temporal ridges quite prominent, not uniting
23 Science (N.S.), Vol. XXIV, Aug. 31, 1906, p. 282-283; Annals Car. Mus., Vol. IV, 1906, p. 47,
PL XV, text-figs. 12-13; Vol. VII, 1910, p. 274-279, PI. LXV; Loomis, F. B., Amer. Jour. Science, Vol.
XXVI, July, 1908, p. 58.
^*D. arrikarense Barbour, Science (N.S.), Vol. XXIV, Dec. 14, 1906, pp. 780-781, figs. 1, 2; Acera-
therium stigeri Loomis, Amer. Journal Sci., XXVI, July, 1908, p. 60; Diceratherium schiffi Loomis, I.e.,
p. 57; D. aberrans Loomis, I.e., p. 59; D. loomisi Cook, Harold J., Neb. Geol. Surv., VII, p. 48-32, figs. 2-3.
432 MEMOIRS OF THE CARNEGIE MUSEUM.
to form a sagittal crest, but continuing separate to the inion where they join the
lambdoidal crest." Loomis on the other hand states that the skull is relatively
short, and high, with high occipital crest and a moderate sagittal crest, formed by
the confluence of the two ridges from over the orbits. This mistake is undoubtedly
due in part to the illustration (Ann. Carn. ]\Ius., Vol. IV, 1906, p. 48, Fig. 12)
which does not accurately represent the top of the skull. This is remedied in the
illustration given with this paper, PL LXII, Fig. 1.
Loomis further states that "on the premolars, the cingulum is greatly reduced,
while the strong crochet is united with the feeble crista, thus isolating the median
fossette. In like manner on the molars the cingulum is reduced to traces on the
front, inner side, and rear of the teeth." While this description was undoubtedly
based on the material in the Amherst Museum and answers some indi\dduals of this
species in the Carnegie Museum, the type specimen does not agree with his de-
scription. In the first place the internal faces of the premolars, except P^ are
incomplete. The said premolar has a prominent cingulum on the anterior and
internal faces of the protocone, which is confluent by wear with the grinding
face of the metacone. On the antero-intemal angle of P^ a prominent cingulum
is indicated, the inner face of the tooth is otherwise, as stated, broken off as is
also P^ on the anterior inner angle (See PI. LX, Fig. 1.) ISl^ and M- are also dam-
aged in this same region, but enough is preserved to indicate that the cingulum
is as prominent as is the case in other skuUs, which are more complete in this
respect. P- and P^ have the crochet united with the ectoloph through wear;
no crista is shoviTi, while the post-fossette is entirely isolated on P^ P^ has only a
trace left of the crochet, but no crista; post-fossette nearly enclosed. M^ has
crochet united with the ectoloph by wear, and post-fossette enclosed. INI^ has a
strong crochet and the cro^^^l is injured in the region of the crista. M^ has a
strong crochet and a fairly prominent crista. The entire dentition is much worn,
plainly indicating an old individual. The distinguishing characters of Acera-
therium stigeri and Diceratherium schiffi given by Dr. Loomis now appear to rest
entirely on sexual characters and individual variation, the type of his proposed
species being female skulls of D. cooki, while his species D. aberrans is established
on D. P.- of the left side as has already been pointed out."
From Professor Barbour's description and figures of his proposed species
D. arrikarense in Science, N.S., Vol. XXIV, 1906, p. 780, it is clear that he has
described a male skull of D. cooki minus the dentition, while Mr. Cook's proposed
" Peterson, 0. A., " Recently Proposed Species of the Genus Diceratherium," Science (N.S.), Vol.
XXXVI, 1912, p. 801.
PETERSON: THE AMERICAN DICERATHERES.
433
species, D. loomisi, is also established on a maxilla of D. cooki with deciduous
teeth. (Neb. Geol. Surv., VII, 1912, p. 29.)
In comparing the crania of the abundant material of D. cooki with the earlier
John Day forms, or even with D. niobrarense found in the same beds in which
D. cooki is found in Nebraska, it is at once clear that D. cooki is a comparatively
more specialized and modified type of the Diceratherince. We find in the male
skull (1) a pair of prominent horn-cores set closely together on the nasals; the
nasals themselves not nearly as heavy as in the earlier John Day forms; and the
ends of the nasals much abbreviated as in more specialized or modified forms of
the Titanotheridce; (2) muzzle, premaxillaries, and the front of the lower jaws
shortened and the lateral margin of the anterior nares extended further back of
the horn-cores; (3) brain-case enlarged; occiput broadening and not overhanging;
basicranium short, analogous to Teleoceras from the middle Miocene and the recent
Rhinoceroses {R. bicornis) ; (4) zygomatic arches much expanded with heavy rugo-
sities on the posterior angle, and the angle of the lower jaws heavy and very much
Fig. 16. Diceratherium cooki Peterson. No. 1853, Coll. Carnegie Museum. Skull of an old female. X J.
everted to support heavy masseteric muscles; (5) the grinding surface of the cheek-
teeth further complicated with a tendency on the part of the crochet to become
united with the ectoloph, especially in teeth having received some wear.
As has already been stated in the introductory paragraphs of this paper, a
greater range of variability must be allowed in dealing with female crania of this
species. They range from those without horns in very young and immature
females to those with incipient horns in fully adult and old individuals. The
top of the skull is consequently comparatively little concave antero-posteriorly
and the supratemporal ridges vary so much in their course to the inion that this
region of the cranium may be said to range from a broad surface to a completely
formed sagittal crest (this variation of the supratemporal and sagittal ridges
holds good even in males, though to a somewhat less extent). Another feature
of the female skull, no less noticeable, is seen in the longer pointed nasals, the
434 MEMOIRS OF THE CARNEGIE MUSEUM.
lighter zygomatic arches without the heavy rugosities on the posterior angle, and
the less everted angle of the lower jaws. In connection with these characters
the skeletal frame is lighter and the pelvic cavity proportionally somewhat larger,
judging from the material at hand.
Mandible.
(PL LXVI, Figs. 2 and 4.)
As stated elsewhere-'' the lower jaws are hea\'y% especially those of the males.
The depth of the ramus, however, is not great, and the diastema between the lateral
incisor and P2 is rather short. The symphysis, though short, is very heavy, and
the median suture is entirely obliterated in old individuals. The angle is very
greatly everted; in males the border of this everted area is very rugose, while in
females and young the angle is less everted and is also less rugose, but still furnishes
an imusual heavy surface for the masseteric muscles. The glenoid condyle is quite
broad transversely and the coronoid process is strongly directed forward.
Dentition. — In proportion the median incisor is extremely small; it has a
rounded enamel-covered crowTi, and is implanted in the symphysis by a thick
short root; in many specimens this rudimentary tooth has dropped out. The
lateral, or cutting incisor, is, as usual, comparatively large, but varying in different
individuals. The canine is generally absent, even in the young. Occasionally
this tooth is present in young individuals, and sometimes there is found on the
alveolar border of the diastema a shallow gToove, or scar, in which a minute canine
is found in a very procumbent position. Pi is absent. In young individuals a
small milk-tooth is often found immediately in front of Po which persists in the
alveolar border until aU the cheek-teeth are erupted. On PL LXVI, Figs. 2 and 4
the characters of the cheek-teeth are well sho-rni, and require no detailed de-
scription.
Only a very few hyoid bones are found mixed with the general mass of ma-
terial in the quarries, there evidently having been during deposition too much
disturbance for the preservation of these delicate parts.
In this connection it is interesting to tiu'n to the work of Professor Henry
F. Osborn, "The Extinct Rhinoceroses" Mem. Amer. ^Museum Natural History,
Vol. I, 1898, pp. 136-140. In this publication, Osborn characterizes Coenopus
{Aceratherium) 7nitis from the lower Oligocene as foUows (p. 139): "Cr", P3, ^Ms,
Diastema short. Canine"" alveoli semi-procumbent. Premolar-molar series
=' Peterson, O. A., Ann. C.ir. Mus., Vol. VII, 1910, p. 275.
" [= Lateral incisor.]
PETERSON: THE AMERICAN DICERATHERES. 435
142 mm. Mandibular symphysis very short. Locality Colorado. Amer. Mus.,
Cope Collection, No. 6325."
This type specimen is accompanied by an upper maxillary with teeth and
other skeletal material, but, as there seems to be some doubt as to their association,
they will not here be considered.
A second specimen in the American Museum Collection from the upper
Oligocene (Protoceras Beds) illustrated on page 139 of Osborn's work is especially
interesting. This lower jaw (No. 1110) is doubtfully referred to Ccenopus {Acera-
therium) mitis Cope, and exhibits just such characters as one might expect to find
in an ancestral form of D. cooki: the short symphysis; the short diastema between
incisor and cheek-teeth; the curving of the lower border of the ramus; and the angle
everted as in D. cooki. The ramus itself is, however, deeper, the vertical ramus
having a greater antero-posterior diameter, and the coronoid process a more nearly
vertical position than in D. cooki, as indicated by the illustration. The measure-
ments (p. 140) do not appear to agree completely with the illustrations.
This lower jaw undoubtedly represents a distinct species, judging from the
great vertical depth of the sediments lying between the Titanotherium beds in
which Coenopus mitis (Cope) was found, and the Protoceras sand-stones, together
with the general change in the fauna of these two geological horizons. This
lower jaw from the Protoceras beds may here be provisionally regarded as the type
of Ccenopus dakotensis sp. nov. and also provisionally placed in the line more or
or less directly leading to D. cooki found in the lower Harrison beds of Nebraska
as indicated in the table found in the introduction to this paper.
Vertebral Column.
The vertebral formula is provisionally given as follows: Cervicals, 7; Dorsals,
19 (?); Lumbars, 5; Sacrals, 4-5; Caudals, 26.
Cervical Vertebrce (Figs. 17-21). In a fully adult animal the width of the
atlas is almost double that of the length. The anterior projection of the trans-
verse process extends well forward. The neural canal is of moderately large size,
while the arterial canal on the ventral face of the transverse process is generally lack-
ing. The median area of the neural arch varies in different individuals in robustness
and rugosity. The transverse process and the median tubercle of the lower pos-
terior face of the body also vary in robustness and size.
The odontoid process and body of the axis are heavy; the neural spine is
generally heavy and overhanging, while the transverse process projects rather
strongly backward. The latter process is subject to much variation in size, as is
436
MEMOIRS OF THE CARNEGIE MUSEUM.
also the ventral keel. The arterial canal is indicated by a deep groove on the
anterior border of the pedicel, which is often found completely bridged over bj' a
Fig. 17. Diceratherhim cooki Peterson. No. 1S5.3, Coll. 'Carnegie Museum. Ventral and anterior views
of atlas. X J.
thin splint of bone. Additional features of this bone are well shown in the illus-
trations. (See Fig. 18.)
The third, fourth, and fifth cervicals are, as usual, very uniform in their details
Fig. 18. Diceratherium cooki Peterson. No. 1853, CoU. Carnegie Museum. Lateral and posterior
views of axis. X |.
of structure. There is, however, no neural spine on the third; the fourth has a spine
more or less clearly indicated ; the fifth a spine of considerable size varj-ing in length
in different individuals.
The sixth cer\'ical is characterized by the broad, thin, hatchet-shaped, inferior
lamella of the transverse process, which sometimes terminates in a rounded process
PETERSON: THE AMERICAN DICERATHERES.
437
behind. The superior, or transverse process proper, is located well up on the
centrum; it is trihedral in cross-section, rather short, and projects strongly back-
wards. The neural spine of this vertebra is quite high, attenuated, of great antero-
posterior diameter, and terminates rather abruptly.
Fig. 19. Diceratherium cooki Peterson. No. 2499, Coll. Carnegie Museum.
of fourth cervical. X |.
Lateral and posterior views
The neural spine of the seventh cervical is quite high and generally terminates
in a sharp point. The transverse process is abruptly reduced and there is no
vertebrarterial canal.
Fig. 20. Diceratherium cooki Peterson. No. 2499, Coll. Carnegie Museum.
of sixth cervical. X i.
Lateral and posterior views
Dorsal Vertebrce (Figs. 22-24). We are not yet in a position to positively
state the number of vertebrae in the dorsal series. In the skeletons articulated
and those assembled for articulation and sent to other institutions by the Carnegie
Museum there have been inserted nineteen. This number is thought to be ap-
438
MEMOIRS OF THE CARNEGIE MUSEUM.
proximately correct, as it corresponds with those in Coenopus tridactylus Osborn
which was found, articulated, in the upper Oligocene of South Dakota.^^
The first dorsal vertebra is characterized by the proportionally large and high
Fig. 21. Fig. 22.
Fig. 21. Dicerathermm cooki Peterson. No. 2499, Coll. Carnegie Museum. Lateral and posterior views
of seventh cervical. X i-
Firi. 22. Diceratherium cooki Peterson. No. 2499?, Coll. Carnegie Museum. Lateral and posterior
views of first dorsal. X |.
neural spine and the depressed centrum; the prezygapophyses are also much ex-
panded laterally to receive the postzygapophj'ses of the last cervical. The articu-
lations for the ribs are located very low on the side of the centrum and the pedicel
is broad and heavy.
With the exception of the skull, there is probably no other part of the skeleton
in this species which is subject to greater variation than the neural spines of the
dorsal vertebrae. In specimens undoubtedly referable to adult and old males
28 Osborn, H. F., Bull. Amer. Mus. Nat. Hist., Vol. V, 1893, p. 85.
PETERSON: THE AMERICAN DICERATHERES.
439
the first dorsal spine is high, broad, and rugose, as shown in Fig. 22, while in
many specimens, fully adult and old, this spine is 50 mm. shorter, and sometimes
even more. In the anterior dorsals the curvature of the neural spine also varies
from a comparatively straight spine to one with a gentle sigmoid curve. The
latter are generally those with the longer and heavier spines. The neural spine of
the second dorsal is suddenly reduced in size, but back of the second the reduction
is more gradual. The anterior dorsals have short, broad, and depressed centra,
while further back they are higher, narrower, and terminate ventrally in better
defined keels. The intervertebral notch is deep and in the posterior upper side
of the centrum it continues downward in a broad and well-defined groove, princi-
pally due to the greatly elevated border of the capitular facet on the centrum.
Fig. 23. Fie, 24.
Fig. 23. Diceratherium cooki Peterson. No. 2499, Coll. Carnegie Museum. Lateral and posterior
views of tenth dorsal. X j.
Fig. 24. Diceratherium cooki Peterson. No. 2470a, Coll. Carnegie Museum. Lateral and posterior
views of eighteenth dorsal. X h
In the neighborhood of the eighth, ninth, and tenth dorsals there is usually a fora-
men formed at this notch, which is characteristic of all posterior dorsals except
the last. (See Figs. 23-24.) The fourteenth and fifteenth dorsals have the neural
spines broader and more lumbar-like; the mammillary processes, so characteristic
of the transverse processes of the dorsals are also longer and project forward in
these vertebrae to a greater extent. The inferior aspect of the centra vary from a
gently rounded to a more decided ventral keel, possibly due to sex.
Lumbar VertebrcB. Figs. 25-27. There are five lumbar vertebra?. This
causes this part of the spinal column to be rather short. In general outline the
440
MEMOIRS OF THE CARNEGIE MUSEUM.
centrum of the first lumbar is not unlike that of the posterior dorsals, while further
back the lumbar vertebrae are more depressed and gradually broadened. The
last is broader than long. The last lumbar vertebra is otherwise conspicuous on
Fig. 25. Diceratherium cooki Peterson. No. 2470a, Coll. Carnegie Museum. Posterior view of second
lumbar. X i.
account of its suddenly reduced neural spine. This reduction is principally in the
fore-and-aft direction so that there are broad vacuities between the spines in front
and behind.
The more noticeable variations in the lumbar series result from the presence
or the absence of an articulating buttress between the fourth and fifth lumbars.
Fig. 26. Diceratherium cooki Peterson. No. 2-170a, Coll. Carnegie Museum.
views of lumbar four. X \.
Lateral and posterior
This articulation is located on the transverse process (posterior face) of the fourth,
and meets a corresponding surface on the anterior face of the process on the fifth
lumbar. (See figs. 26 and 27.) The first lumbar is sometimes found to possess
an unusually long transverse process, which tapers rapidly and is rib-like.
PETERSON: THE AMERICAN DICERATHERES.
441
Sacrum. Fig. 28. There are four and often five coossified centra of the
sacrum. The two first vertebrae support the iUum, while those in the rear have
sharp lateral edges and gradually taper toward the caudals. The neural spine of
Fig. 27. Diceratherium cooki Peterson. No. 2470a, Coll. Carnegie Museum. 1, lateral view of fifth
lumbar; 2, anterior view of same; 3, posterior view of same. X J.
the first sacral is generally quite slender, but further back the spines are more
robust. The sacral foramina are of large size and the coosification between the
Fig. 28. Diceratherium cooki Peterson. No. 2797, Coll. Carnegie Museum. Lateral and ventral views
of sacrum. X h
442
MEMOIRS OF THE CARNEGIE MUSEUM.
centra is complete, especially in fully adult or old individuals, there being little
or no trace of a suture.
Caudal Vertebrce. Twenty-six vertebrae have been attributed to the tail.
This is thought to be approximately correct, inasmuch as seventeen were found in
consecutive order from the first to and including the seventeenth. The seventh
caudal is the last with a complete neural arch, and the eighth is the last with
traces of a transverse process. The tail as a whole is moderately long and tapers
to a fine point as indicated by many very small vertebrae found in the collection.
Ribs. — The ribs, even the posterior, are rather long. In the anterior region
they are flat, though not broad, while further back their cross-sections have a
tendency to be more trihedral. There are well-defined tubercular facets throughout
the entire series. Altogether the thorax forms a rather solid cylinder.
Fig. 29. Diceraiherium cooki Petereon. No. 2S17, Coll. Carnegie Museum. 1, Dorsal view of sternum;
2, ventral view of same; 3, lateral view of same. X i-
Sternum. Fig. 29. The sternum was described in part as follows:-^ 'The
manubrium is an elongated, laterally compressed, and vertically deep plate of
bone. Anterior to the contact for the first pair of ribs there is a long heavy process,
extending forward, and constituting the greater half of the entire length of the
presternum. Posteriorly the bone is slightly expanded transversely and has a
rough surface for the attachment of the mesosternum. The first two segments
of the latter are somewhat deeper than wide. The posterior end of the fourth
sternebra is nearly square in outline, while the fifth and sixth are broader than deep.'
2' Peterson, 0. A., Ann. Car. Mus., Vol. VII, 1911, p. 277.
PETERSON: THE AMERICAN DICERATHERES.
443
Fore Limb.
Scapula. The scapula is long, narrow, and recurved. It is perhaps some-
what narrower than in earlier types (C. tridadylus, Osb.) and nearer the propor-
tions found in more recent forms (R. pachygnathus or R. bicornis Wagn.) In
general the outlines are very similar to those of these species. The coracoid is
prominent, the supra-scapular notch quite deep. The spine, which nearly equally
divides the supra- and infra-spinous fossae, terminates in a very heavy and retro-
verted process. There is a third fossa at the coracoid border immediately above
the suprascapular notch, which is separated from the supraspinous fossa by a
Fig. 30.
Diceratherium cooki Peterson. No. 2473, Coll. Carnegie Museum. External views of scapula.
X 4.
somewhat prominent vertical ridge. The fossa itself, however, is rather shallow
and of relatively small size. (See Fig. 30). There is very little variation in the
details of the scapula in fully adult animals, robustness and size excepted.
Humerus. The humerus is short and heavy. The tuberosities of the proximal
end, though not as heavy in proportion as in some of the recent Rhinoceroses
{R. bicornis), are nevertheless, very prominent and the bicipital groove has a
tendency to become double, i.e., separated by a broad, but very low ridge, approach-
ing the condition in the recent Rhinoceros where the bicipital tubercle is more
prominent. Distally the bone has furthermore a great transverse diameter due to
444
MEMOIRS OF THE CARNEGIE MUSEUM.
the large entepicondyle and prominent supinator ridge. The anconeal fossa is
very deep and of considerable height (See Fig. 31.)
The proportionate length of the radius and ulna is approximately like that of
Rhinoceros bicornis. In the fossil form the shafts of both radius and ulna are, how-
FiG. 31. Diceratherium cooki Peterson. No. 2473, Coll. Carnegie Museum. Posterior and anterior
views of humerus. X h
ever, flatter than in the African species. In fully adult and old individuals this is
chiefly due to the rugose and prominent ridges, which actually come in contact with
each other throughout the whole length of the bones, while in the recent form the
median region of the shafts is rounded and the two bones are separated by a consider-
able space. The shaft of the radius is quite straight, while the ulna as a whole is much
bent backward, especially the upper half, a characteristic seen in the recent form.
The carpal articulations differ from those in the African form to a marked degree.
Thus the lunar articulates exclusively with the radius in Diceratherium, while
in R. bicornis it encroaches to a considerable extent on the distal face of the ulna.
On the other hand it is observed in a number of cases in Diceratherium that the
cuneiform extends over upon the radius, forming a minute facet on the extreme
ulnar border as well as on the palmar face. There is a considerable variation,
especially in length and robustness, of the fore-arm of D. cooki, which is undoubtedly
due to sexual and individual variation as well as age.
Manus. Pis. LXIII; LXIV. The height and breadth of the carpus are
petekson: the American diceratheres.
445
practically equal, the height being sometimes very slightly greater than the breadth,
while in the recent rhinoceros the breadth is a little greater than the height.
The proximal facets of the scaphoid and cuneiform are not unlike those in recent
forms, while the lunar lacks the facet for the ulna, so plainly shown in the African
species. The large facets and the heavy palmar hook of the lunar uniting the
lateral bones on the proximal row of the carpals in R. bicornis are conspicuously
absent in Dicer atherium. The second row of the carpals in the latter are higher than
Fig. 32. Fig. 33.
Fig. 32. Diceratherium cooki Peterson. No. 2473, Coll. Carnegie Museum. Radial and dorsal views of
ulna. X i-
Fig. 33. Diceratherium cooki Peterson. No. 2499, Coll. Carnegie Museum. Oblique ulnar view of
radius and ulna. X J.
those in R. bicornis; otherwise there are only minor details of difference between
the two forms. With regard to size, the trapezium and metacarpal V have ap-
proximately the same proportions as in the living species. The three functional
metacarpals in D. cooki are decidedly longer, slenderer, and the shafts of II and IV
are more curved. This curvature of the shafts of Mc II and IV is to conform to
446
MEMOIRS OF THE CARNEGIE MUSEUM.
the sides of Mc III to which bone they he rather close with comparatively little
divergence distally. All the phalanges are broad, short, and depressed. (See
PI. LXIII).
In Coenoptis tridactylus the metacarpals also are close to one another, but
the lateral metacarpals are heavier in proportion than in D. cooki. This is also
true of the bones in the hind foot. Another noticeable feature of the hind foot in
C. tridactylus is seen in the proportionally larger size of the entocuneiform, which is
not remarkable, when we consider the differences in size of the lateral metapodials
in the two genera here compared.
Hind Limb.
The pelvis is short and broad. The area for the gluteal muscle is broadly
expanded, but the supra-iliac border is emarginated as in Ccenopus of the Oli-
FiG. 34. Dicer atheriuin cooki Peterson. No. 2797, Coll. Carnegie Museum. Left half of pelvis, dorsal
view. X 3-
gocene. The ischium and pubis are relatively short when compared with Ccenopus
tridactylus, indicating quite an advance in the direction of the recent Rhinoceroses.
PETERSON: THE AMERICAN DICERATHERES.
447
The acetabulum is well rounded and deep ; the pit for the round ligament is quite
deep and the cotyloid notch broad. The obturator foramen is very large and
ovate in outline. The sciatic notch of the ischium is well-defined by the sudden
termination of the spine and the heavy and suddenly upward, or outward, turned
tuber ischii. The prominence of the latter tuberosity is subject to some variation
Fig. 35. Fiq. 36.
Fig. 35. Diceratherium cooki Peterson. No. 2460, Coll. Carnegie Museum. Posterior and anterior
views of femur. X i.
Fig. 36. Diceratherium cooki Peterson. No. 1840, Coll. Carnegie Museum, 1, anterior view of tibia
and fibula; 2, posterior view of same. X j.
in different individuals. In fact there is in this species a considerable degree of
variation in the robustness of the pelvis in the large collection before us. This,
in my judgment, is due to age and sex.
The femur is quite long. The shaft, when seen from the front, is quite straight,
but on a rear view appears curved, due to the prominence of the different trochanters
(See Fig. 35.) The third trochanter, though large, is not the long, forward, and
448 MEMOIRS OF THE CARNEGIE MUSEUM.
outward extending process seen in R. bicornis. Nor is the proximal end so much
expanded laterally as in the African species.
The tibial border of the rotular trochlea is greatly developed ; it has very nearly
reached the extreme modernized stage of development seen in the recent Rhinoceros
and the horse. The antero-posterior diameter of the distal end is therefore greater
than the transverse in approximately the same proportion as in R. bicornis.
The patella is triangular in general outline, due to the large development of
the internal process in order to cover the greatly develoj^ed internal border of the
rotular trochlea described above. The trochlear grooves of the patella are quite
uneven in size and the bone as a whole unlike that of the horse.
In fully adult and old individuals both ends of the tibia and fibula have a
strong tendency to become coossified. This is a direct indication of the progressive
development which has reached its culmination in the completely united tibia and
fibula of R. bicornis. Like the femur, the tibia and fibula are rather long and slender,
when compared with these bones in the recent species, and it also appears that
Fig. 37. Diceratherium cooki Peterson. Xo. 1840, Coll. Carnegie Museum. Posterior and anterior
views of patella. X J.
these bones in Ccenopus tridactylus (Osborn) are proportionally shorter and pos-
sibly also somewhat heavier than in D. cooki.
Pes. Pis. LXIII, LXIV. As is already known, the pes is strictly tridactyl.
It is on the whole narrow and quite high, especially when compared with R. bicornis.
It is also somewhat higher and slenderer than the pes in Ccenopus tridactylus.
The tuber of the calcaneum has about the same general proportions as the
European species D. (?) croizeti Pomel*, i.e., it is quite heavy and of medium length,
while the sustentacular facets are similar in detail. The broad and rather low
astragalus also agrees in detail with that of this European form. The cuboid is
quite high and has an extremely heavy process posteriorly. The metatarsals are
quite elongated, the lateral metatarsals with curved shafts somewhat similar to
those in the manus. The vmgual phalanges are shorter than in the manus.
The remains of Diceratherium cooki constitute by far the greatest percentage of
all the material found in the Agate Spring Fossil Quarries. Another significant
* Pomel referred the species to Accratherium. Professor Max Schlosser identifies it as Diceratheritun
in the case of material sent to us from the Royal Museum in Munich.
PETERSON: THE AMERICAN DICERATHERES. 449
Measurements of the Type op D. cooki.
Greatest length of skull 350 mm.
Length from occipital condyle to and including P^ 307
Length from occipital condyle to M' 150
Greatest transverse diameter of skull 215
Greatest transverse diameter of brain-case 107
Greatest transverse diameter of frontals 140
Transverse diameter of nasals back of horn-cores 65
Transverse diameter of nasals at the horn-cores 70
Transverse diameter of palate at M' 55
Vertical diameter of the orbit 30
Antero-posterior diameter of premolars two, three, and four 68
Antero-posterior diameter of the molar series 90
Antero-posterior diameter of P^ 22
Transverse diameter of P^ 23
Antero-posterior diameter of P* 28
Transverse diameter of P^ 29
Antero-posterior diameter of M' 34
Transverse diameter of M' 32
Antero-posterior diameter of M' 26
Transverse diameter of M^ 32
Measurements of Limb Bones of Skeleton.
Scapula, height 273 mm
Scapula, width at superior border 138
Humerus, length 250
Ulna, length 315
Radius, length 250
Carpus, height 59
Carpus, transverse diameter 60
Mc II, greatest length 70
Mc III, greatest length 138
Mc IV, greatest length 115
Phalanges, median digit , 70
Pelvis, total length 335
Pelvis, diameter across ilia 355
Pelvis, Diameter across acetabulum 220
Femur, length 323
Tibia, length 275
Tarsus, height of tuber of calcaneum not included 70
Tarsus, length of tuber of calcaneum 48
Tarsus, greatest transverse diameter 53
Mt. II, length 110
Mt. Ill, length 125
Mt. IV, length 110
Phalanges, third digit 30
450 MEMOIRS OP THE CARNEGIE MUSEUM.
fact is the great number of bones representing young animals and females in pro-
portion to those of males. This would appear to indicate (1) that the animals
were polygamous to a great degree and that the males were either struggling for
the possession of the herds after the manner of recent ungulates (Equus) , and were
few, or, that they were strong enough to extricate themselves when overtaken by
the calamities which destroyed the herds.
The articulated skeleton of Diceratherium cooki has been fully discussed in
the Annals of the Carnegie Museum, Volume VII, pp. 274-279.
Modes of Development op Certain Dental and Bony Structures of the
Cranium in Diceratherium.
(Plates LXV and LXVI.)
Important facts, in connection with the evolution of the dental formula and
other features of the cranium of the Rhinocerotidae, are obtained from the large
collection under study in the Carnegie Museum. Some studies bearing on the
evolution of the incisors and canines of Diceratherium were already presented before
the Paleontological Society at Pittsburgh in 1910. The following pages are given
to a further discussion of the appearance and shedding of the different deciduous
teeth, the appearance of the permanent series, and other changes of contour of
the head from the young to the fuUy adult form of Diceratherium cooki.
1. A skull of a young Diceratherium, No. 1848 (See PL LXV, Figs. 1, 2, 4)
which belongs to the original series from which the type of D. cooki was selected,
is especially complete and furnishes an excellent opportunity for study. In viewing
this skull from above, the most noticeable characters are the following: brain-case
proportionally broad; occiput short; f rentals broad; horn-cores little developed,
and nasals gradually pointed, more like that of adult females. Back of the horn-
cores on the lateral margin of the nasals there is also less constriction in skulls of
young individuals and adult females than is the case in males. The supra-orbital
ridges are so varied that one cannot attach great importance to them, though it
would appear that in female skulls they are generally less prominently developed
and in their backward progression to the occiput they possibly have a tendency to
be further separated from the median line. On either a direct side view or a palatal
view of the young skull the most noticeable feature is the great backward extent of
the alveolar border of the maxillary. The alveole for M^ is seen to be nearly oppo-
site the pterygoid, while in fully adult forms this tooth is well in advance of this
region. In very young individuals, the base and the supra-occipital of the skull
are often slipped off at the sutures, not an unusual feature of the mammalia.
In the skuU here described, the base is lost, but the supra-occipital is in position.
PETERSON: THE AMERICAN DICERATHERES. 451
Buried deep in the small round alveolus, the point of the upper permanent
incisor is found. Judging from the size of the alveole, the deciduous tooth was
rather small and had a root of more rounded outline than the permanent one,
and the crown was perhaps also of an entirely different shape. There is no canine
present and, if there were a deciduous canine in this individual, it dropped out
early and the alveole was closed, there being in this region a small groove which
extends for a short distance back of the maxillary-premaxillary suture. If there
was a deciduous first premolar in the Diceratheres, it was possibly shed very early
in life.^° P^ is somewhat worn, but not enough to lose the characters of the grinding
face. (See PL LXV, Fig. 2.) The ectoloph is, as usual, well developed, the
protoloph is less prominent than the metaloph, which gives to the tooth the char-
acteristic triangular outline. The post-fossette is sometimes constricted in such a
manner as to form an isolated fossette on the metaloph on further wear, while the
main post-fossette continues to the posterior edge of the tooth. This fossette is
not always present. D.P^ is considerably worn, but the detailed structure is yet
easily made out. The tooth is longer than the permanent tooth, the ectoloph is
heavy, the protoloph is well developed internally as is also the metaloph. The
crista is enormously developed, extending on an even internal line with the proto-
and metalophs. In a young or unworn tooth this ridge is often constricted so
as to form an internal tubercle, which on further wear unites with the true crista.
In the young of the John Day forms both the crista and this internal tubercle are
less developed and apparently entirely separated, judging from the material in
the American Museum. This is admirably illustrated on PI. LXV Fig. 3. The
crochet of D.P^ in D. cooki is quite distinct though much less developed than the
crista, and the cingulum is well developed on the internal face of the tooth. In
excavating the maxillary above D.P- it is seen that P^ is quite well advanced. See
PL LXV, Fig. 1. D.PMs well worn. The median valley is open, but the crochet is
evidently united with the ectoloph, while the post-fosette is isolated by wear of
the tooth. There is a small tubercle on the internal cingulum in the median
valley. D.P^ has the well developed crochet still separated from the ectoloph,
but the crista is rather poorly developed or wanting. The median valley is open
and, as in the preceding tooth, there is a small tubercle on the cingulum at the
exit of the valley. The post-fossette is broad and open. M^ is fully erupted and
has already received some wear. The ectoloph is yet quite thin, but in excavating
30 jf pi JQ Diceratherium did not succeed a milk-tooth in extremely early stages of the animal, this
tooth may be regarded as a persistent milk-tooth which would agree with the studies of Huxley (" Anatomy
of Vertebrate Animals," p. 362); Lydekker ("Notes on the Dentition of Rhinoceroses," Jour. Asiatic
Society of Bengal, Vol. 49, 1880, pp. 135-6).
452 MEMOIRS OF THE CARNEGIE MUSEUM.
the median and prefossettes, the walls of the internal face of the ectoloph and the
external face of the crochet are rapidly slanting toward one another, so that on
extreme wear the tooth would have the usual appearance seen in old individuals
of this species. The post-fossette is deep and broad. The cingulum is less de-
veloped internally than on the milk premolars. M^ is just appearing in its alveolus
and M^ is entirely buried in the maxillary.
2. In a somewhat younger individual (No. 2476) it is observed that the
roots of D.P- are longer and heavier and in excavating the maxillary, P-
is found in an extremely early stage of formation (often no evidence of it
is found). M^ in this individual is just cutting through the alveolar border,
while that in the specimen described above has received slight wear. There
can be only a comparatively small difference in age of these two individuals, and
it thus appears that the permanent teeth developed extremely rapidly after they
began to show the form of tooth in the maxillary bone. This rapid formation
and development of the permanent dentition in Diceratherium should not be
regarded as out of the ordinary when comparison is made with the shedding of the
deciduous and the appearance of the permanent teeth in man and other mammals.
3. In the collection of the Carnegie Museum are two left rami (Nos. 1820
and 1821) representing very young animals, most probably foetal. The total
length of the rami of each of these young specimens is approximately 180 mm.,
while the depth in the middle antero-posterior region is 28 mm. The most char-
acteristic features are as follows:
The lunate-shaped outline of the ramus due to the greatly downward curved
under border of the jaw in the fore-and-aft direction, the close proximity of the
cheek-teeth to the canine and the incisors, due to the absence of a diastema on
the alveolar border of the jaw, the very slight constriction in front of the cheek-
teeth and back of the incisors which is so very pronounced in adult and even in
quite yoimg specimens, the smaU transverse diameter of the symphysis, and the
deep groove on the external face of the jaw extending from the symphysis about
20 mm. back in a parallel line with the long axis of the ramus. The glenoid condyle
is not present in either one of the rami; the coronoid process on the other hand is
present in No. 1820. The latter is rather low, and terminates in an attenuated
process.
The second deciduous incisor is in place, while the alveolus for the first is
empty. The lateral incisor is not present and a small opening external to D.I2
of this individual may or may not have contained this tooth. The small alveolus
for the canine is immediately in front of that for D.Pi; the latter is a round opening
PETERSON: THE AMERICAN DICERATHERES. 453
of considerable size. The two succeeding round openings are for the roots of
D.P2. Back of this point the two succeeding cheek-teeth are partly erupted.
(See PI. LXVI, Figs. 3, 8 and 9.) The general pattern of these teeth is quite
similar to that of the permanent set, indeed it is not easy to distinguish one set
from the other. Portions of a fifth cheek-tooth (Mi) lie buried deep in the jaw
behind the two just described.
4. Two pairs of lower jaws (Nos. 2476, 2477) have been selected from the
collection to represent the next stage of evolution in the development of the ramus,
No. 2476 being represented on PL LXVI, Fig. 7. The total length of jaws Nos.
2476, 2477 is 250 and 270 mm. and their depth is 36 and 40 mm. respectively. At
this stage the jaw is easily recognizable, as all the characteristic generic features
are present. The jaw is less lunate-shaped, the characteristic diastema in front
of the cheek-teeth is quite well developed, including the constriction of the alveolar
border, which in the younger stage is represented only by the deep groove on the
external face of the ramus referred to above. In this stage of development the chin
is broader, due to the lodgment of the already well-advanced lateral incisor. The
temporal fossa is well developed, as are the condyle and the coronoid process.
The median incisors are just through the alveolar border and present the
same small and conical-shaped crowns met with in older forms. These teeth
are succeeded by a short diastema before the alveoh of D.I 2 is reached. The latter
is situated somewhat posterior to Ii and I3 in the alveolar border and is thus placed
in an irregular position. In the specimens of the Carnegie Museum under obser-
vation there is sometimes found a delicate septum separating the second and third
incisors. This bony bridge is often broken. D.I3 is frequently found in position
as is the case in the specimen here described, see PI. LXVI, Fig. 7. This tooth has
a long root, quite robust, on which sits a small enamel-covered crown very little
larger in circumference than the root itself. The two lateral incisors are succeeded
by a diastema ; the alveolar border here forms a heavy rounded edge with a notice-
able swelling on the external face. This swelling of the incisive alveolar border
is due entirely to the rapid development of the cutting incisor of the second set of
teeth which is yet buried underneath the deciduous dentition. The deciduous
canine is found in many individuals. This is a small tooth with a conical enamel-
covered crown and a rather short root. The canine is quite generally found in a
procumbent position, isolated by diastemata in front and behind, and drops out
very early. The diastema back of the canine constitute a long and sharp border
which has first a slight inward curvature and then suddenly takes an outward
direction to meet the cheek dentition. The first deciduous cheek-tooth is rather
454 MEMOIRS OF THE CARNEGIE MUSEUM.
small, simple-crowned, receives comparatively little wear, and is closely crowded
to the anterior faceof the succeeding tooth. D.P2 is proportionally longer and
narrower than P2. The configuration of the crown is otherwise quite similar in
the two. D.P3 has by far the greatest wear and is, if one may judge by the degree
of wear, the first cheek-tooth to appear in the young. D.P4 is less worn and cuts
the alveolar border simultaneously with or perhaps a little sooner than D.Po. Back
of D.P4 are seen the points of the crown of Mi and back of the last-mentioned tooth
the alveolar border is deeply marked to indicate the position of M2 which is still
entirely buried in the jaw.
5. The next stage of development in the succession of teeth from the deciduous
to the permanent series is interesting. Three individuals have been selected
which fairly well cover the main points in individual variation and irregularities of
development. Of these three individuals No. 1923a might be considered as the
most normal and will be first discussed. The small median incisor occupies the
usual position, while the permanent lateral incisor has broken through the alveolar
border (PI. LXVI, Fig. 5), uniting the alveoli for D.I 2 and D.I 3 into a large trans-
versely oblongate fissure for receiving the cutting and procumbent incisor.^^ In
this individual the alveolus for the canine of the right ramus is present, though very
small, while in the left there is no trace of an alveolus for the canine. D.Pi is in
place while D.P2 has been shed and the crown of P2 appears through the alveolar
border. D.P3 is still in place but P3 is well advanced and the deciduous tooth was
almost ready to drop off before the death of this individual. D.P4 is apparently
quite solid in the jaw and still served well for masticating purposes. Mi has
already received considerable wear, while M2 is almost entirely erupted. M3 is
quite undeveloped and is buried deep in the jaw.
6. The next specimen to be considered is No. 1841, a pair of lower jaws. This
specimen presents some irregularities worthy of note. From the illustration
(PL LXVI, Fig. 6) it is seen that the permanent lateral incisors of this specimen are
retarded, i.e., they have not yet appeared above the surface of the alveolar border;
the alveoli for the canines are quite large. D.Pi is still in place, but contrary
to the specimen just described both D.Po and D.P3 have disappeared and P2 and P3
have already received some wear, D.P4 is solidly inserted in the jaw. Mi has been in
use for some time and is considerably worn as in No. 1923a, while M2 has received
slight wear on the anterior portion. M3 on the other hand is apparently no further
developed than in the specimen previously described.
'' In the judgment of the writer this incisor is probably I, while I3 and the canine of the Diceratheres
are atrophied.
PETERSON: THE AMERICAN DICERATHERES. 455
7. In No. 1854 it is seen that the lateral incisor is no further advanced than in
No. 1841 just described. The alveole or deep groove'- for the deciduous canine is
still quite prominent while D.Pi is shed and all traces of its alveole entirely oblit-
erated. P2 and P3 have received slightly more wear than those teeth in the previous
specimen described, but D.P4is still well rooted in the alveolar border. Mi is quite
well worn and the anterior part of M2 is also more worn than that in No. 1841.
The deep fissure back of M2 indicates the position of M3. The latter is very little
fiirther developed than in the two preceding specimens and is yet buried in the
angle of the jaw. The three lower jaws just described are of approximately the
same age as the skull No. 1848, referred to in the opening paragraph of this dis-
cussion.
In connection with the probable manner in which the upper and lower incisors
of Diceratherium^^ developed in size, and modified into the shape in which we find
them, it is interesting to return to the foetal specimens Nos. 1820 and 1821 just
described (page 452). We have already found that the deciduous dentition of
these specimens forms practically a close series, without the constricted and thin
areas of the alveolar border between the cheek-teeth and the incisors of older ani-
mals, the alveolus for the canine is deep though small; in excavating the chin,
the continuation of the dental canal is found, but the germ for the permanent
incisor had not yet started, hence the small transverse diameter of the chin.
In the next stage represented by Nos. 2476 and 2477, the specimens are of
quite young animals. We observe here a sudden change. It is likely that the
characters so prominently developed in this young animal had already been
well advanced during the latter part of the intra-uterine stage. At all events
the jaw was still in a very plastic condition in order to have transformed so quickly
between the two stages represented in the illustrations (see PI. LXVI, Figs. 7 and
9) . In the specimens of this second stage we find a broad and heavy chin in order
to support the heavy and long-rooted permanent incisor. The alveolus for the
canine, which we originally found quite deep and placed close to the cheek-teeth,
is now shifted well forward and is transformed into a shallow groove, which in
^- In more matured individuals, the fissure in the alveolar border which lodged the canine cannot be
regarded as a true alveolus.
'^ Not only Diceratherium but the Rhinocerata in general (such forms as the Amynodonts excepted)
undoubtedly developed the cutting incisors along the same general line.
The result of the present study is contrary to the statement by Professor Marsh (Amer. Jour. Sci.,
Vol. XIV, 1877, p. 251). It may be said here that the presence of the canines in the Amynodonts does
not prove "that the large lower teeth, usually regarded as incisors in Aceratherium and many other
members of the Rhinoceros family, are really canines."
456 MEMOIRS OF THE CARNEGIE MUSEUM.
the majority of cases is empty, the small canine lodged therein having dropped
out, while back of the canine we find a long diastema which is very much constricted
forming externally a deep and rather broad groove for the lodgment of the inferior
labial muscles. t
Let us suppose that the foetal specimens referred to have the jaws more or
less like those of the early Tertiary forms. We must in any event expect that the
early progenitors of the family had, first a complete dental series, i.e., f ■ i' i' f
(abundantly proven by the genus Trigonias of the lower Oligocene) ; and secondly
quite likely the absence of a diastema back of the incisors.^'* It follows that
advancing influences effected gradual changes of the bony structure simultaneously^
with that of the teeth. If we have, for instance, a set of lower incisors of subequal
size and a normal canine in its natural position (we actually do find evidence of a
canine in young Diceratheres), we should expect the upper incisors to meet the
lower. When the atrophied and hypertrophied changes took place, which trans-
formed the original sub-equal teeth to those which obtained in later forms, it was
not the lower canine, but I2, which received the constant impact from the upper median
tooth. The diastemata between the incisors, canine, and cheek-teeth was most
likely an early development of the group. The modification of the cutting incisor
was cotemporaneous with the reduction of Ii the atrophy of I3, the broadening of
the chin, and the constriction of the ramus in the region of the canine which, in
turn probably, caused the reduction and final disappearance of the latter tooth.
After the present study of the Diceratherinoe, I cannot accept the designation
given to this tooth, as "canine," by some authors. Professors Marsh, Cope, and
Gaudry having been the first to promulgate this view.
Since the preceding paragraphs were submitted for publication. Professor
W. B. Scott of Princeton University has published his splendid work on the "His-
tory of Land Mammals in the Western Hemisphere." On consulting the history
of the Rhinocerotidse in Scott's volume, pp. 326-340, it is very evident that he
does not regard the large cutting incisor of the lower jaw in the early Rhinoceroses
as a canine. In fact since the genus Trigonias from the Lower Oligocene of America
was established by Mr. Lucas ^^ and more completely described by Mr. Hatcher''^
the morphology of the incisors and canines of the Rhinocerotidse rests on a firmer
foundation.
'* Even in Colonoceras agrestis Marsh, a genus which might be regarded as possibly near the ancestral
line of the Diceratheres, there is a well-established diastema back of the superior canines.
'" Proc. National Museum, Vol. XXIII, 1900, pp. 221-223.
2« Ann. Carnegie Museum, Vol. I, 1901, pp. 1.35-144.
458 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LVII.
Fig. 1. Diceratherium armatum, type. Side view of skull. Peabody Museum,
No. 1000.3.
Fig. 2. Diceratherium armatum, type. Palatal view of same specimen as Fig. L
All figures about f natural size.
460 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LVIII.
Fig. I. Dicer atherium nanum, (Marsh) type. Peabody Museum of Natural
History, No. 10004. Front of skull from the side.
Fig. 2. Diceratherium nanum, type. Front of jaws from the side.
Fig. 3. Diceratherium nanum, type. Alveolar border and dentition.
Fig. 4. Diceratherium cooki. Carnegie Museum, No. 1555.
All figures | natural size.
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462 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LIX.
Fig. L Diceratherium gregorii, type. Side view of skull. American IMuseum of
Natural History, No. 12933.
Fig. 2. Diceratherium gregorii, type. Palatal view of the same skull.
All figures § natural size.
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464 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LX.
Fig. L Diceratherium cooki type. Carnegie Museum, No. 1572.
Fig. 2. Diceratherium niobrarense type. Carnegie Museum, No. 1271
Fig. 1, I natural size; Fig. 2, | natural size.
Memoirs Carnegie Museum, Vol. VII,
Plate LX,
D. cooki Peterson and D. niobrarense Peterson.
466 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LXL
Fig. 1. Diceratherium cooki, type. Carnegie Museum, No. 1572.
Fig. 2. Diceratherium niobrarense, type. Carnegie Museum, No. 127L
Fig. 1, ^ natural size; Fig. 2, | natural size.
Memoirs Carnegie Museum, Vol, VII.
Plate LXI.
D. cooki Peterson and D. niobrarense Peterson.
468 MEMOIES OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LXII.
Fig. L Diceratherium cooki, type. Carnegie Museum, No. 1572.
Fig. 2. Diceratherium viobrarense, type. Carnegie Museum, No. 127L
Fig. 1, I natural size: Fig. 2, | natural size.
Memoirs Carnegie Museum, Vol. VII.
Plate LXII.
D. cooki Peterson \nd D. niohrarense Peterson.
470 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LXIII.
Fig. L Diceratherium cooki, ulnar view of manus, Carnegie Museum, No. 2473.
Fig. 2. Diceratherium cooki, palmar view of manus, Carnegie Museum, No. 2473.
Fig. 3. Diceratherium cooki, radial view of manus, Carnegie Museum, No. 2473.
Fig. 4. Diceratherium cooki, dorsal view of manus, Carnegie Museum, No. 2473.
Fig. 5. Diceratherium cooki, dorsal view of pes, Carnegie Museum, No. 1888.
Fig. 6. Diceratherium annectens hypotype, American Museum Natural History,
No. 7324, Cope Coll.
Fig. 7. Diceratherium cooki, plantar view of pes, Carnegie Museum, No. 1888.
All figures | natural size except Fig. 6, which is | natural size.
Memoirs Carnegie Museum, Vol, VII
Plate LXIII.
D. cooki Peterson and D. annectens (Marsh).
472
MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LXIV.
Diceratherium cooki.
Carnegie Museum, No. 1888.
Fig. 1. Calcaneum, dorsal view.
Fig. 2. Calcaneum, distal view.
Fig. 3. Calcaneum, plantar view.
Fig. 4. Calcaneum, tibial view.
Fig. 5. Calcaneum, fibular view.
Fig. 6. Astragalus, tibial view.
Fig. 7. Ectocuneiform, proximal view.
Fig. 8. Ectocuneiform, distal view.
Fig. 9. Ectocuneiform, tibial view.
Fig. 10. Astragalus, fibular view.
Fig. 11. Astragalus, plantar view.
Fig. 12. Astragalus, dorsal view.
Fig. 13. Cuboid, proximal view.
Fig. 14. Cuboid, tibial view.
Fig. 15. Entocuneiform, fibular view.
Fig. 16. Entocuneiform, distal view.
Fig. 17. Navicular, distal view.
Fig. 18. Navicular, posterior view.
Fig. 19. Navicular, fibular view.
Fig. 20. Navicular, proximal view.
Fig. 21. Cuboid, distal view.
Fig. 22. Mesocuneiform, distal view.
Fig. 23. Mesocuneiform, fibular view.
Fig. 24. Mesocuneiform, tibial view.
Fig. 25. Mesocuneiform, proximal view.
Fig. 26. Metatarsal III, dorsal view.
Fig. 27. Metatarsal III, fibular view.
Fig. 28. Metatarsal II, fibular view.
Fig. 29. Metatarsal II, tibial view.
Fig. 30. Metatarsal IV, tibial view.
Fig. 31. Metatarsal III, tibial view.
Fig. 32. Metatarsal III, plantar view.
Carnegie Museum, No. 2453.
Fig. 33. Scaphoid, proximal view.
Fig. 34. Scaphoid, distal view.
Fig. 35. Scaphoid, ulnar view.
Carnegie Museum, No. 2453.
Fig. 36. Lunar, proximal view.
Fig. 37. Lunar, radial view.
Fig. 38. Lunar, distal view.
Fig. 39. Lunar, ulnar view.
Fig. 40. Cuneiform, radial view.
Fig. 41. Cuneiform, distal view.
Fig. 42. Cuneiform, ulnar view.
Carnegie Museum, No. 1853,
Fig. 43. Pisiform, radial view.
Fig. 44. Trapezium, ulnar view.
Fig. 45. Trapezoid, radial view.
Carnegie Museum, No. 2453.
Fig. 46. Trapezoid, ulnar view.
Fig. 47. Trapezoid, distal view.
Fig. 48. Trapezoid, proximal view.
Fig. 49. Magnum, distal view.
Fig. 50. Magnum, ulnar view.
Fig. 51. Magnum, radial view.
Fig. 52. Magnum, proximal view.
Fig. 53. Unciform, radial view
Fig. 54. Unciform, proximal view.
Fig. 55. Unciform, ulnar view.
Fig. 56. Metacarpal II, radial view.
Fig. 57. Metacarpal II, ulnar view.
Fig. 58. Metacarpal III, radial view.
Fig. 59. Metacarpal III, ulnar view.
Fig. 60. Metacarpal IV, radial view.
Fig. 61. Metacarpal IV, ulnar view.
Fig. 62. Metacarpal V, radial view.
Fig. 63. Metacarpal V, palmar view.
All figures are | natural size.
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474 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LXV.
Fig. L Diceratherium cooki, young male, side view of skull. Carnegie Museum,
No. 1848.
Fig. 2. Diceratherium cooki, Palatal view same as Fig. L
Fig. 3. Diceratherium? annectens, deciduous upper teeth, American Museum
collection.
Fig. 4. Diceratherium cooki, top view of skull, same as Figs. 1 and 2.
All figures | natural size.
Memoirs Carnegie Museum, Vol, VII.
Plate LXV.
Hi dz as (J4,
Mil Jin z inB
D. cooki Peterson and D. anncctens (Marsh).
476 MEMOIRS OF THE CARNEGIE MUSEUM.
EXPLANATION OF PLATE LXVI.
Fig. I. Dicer atherium annectens,hypotype , Side view of skull, American Museum,
No. 7324, Cope Coll.
Fig. 2. Diceratherium cooki, upper contour of lower jaws and crown view of den-
tition. Carnegie Museum, No. 2499.
Fig. 3. Diceratherium cooki, outer view of mandible in very young stage of develop-
ment. Carnegie Museum, No. 1820.
Fig. 4. Diceratherium cooki, outer view of mandible of fully adult male. Carnegie
Museum, No. 2499.
Fig. 5. Diceratherium cooki, alveolar border of lower jaw and crown view of den-
tition. Carnegie Museum, No. 1923a.
Fig. 6. Diceratherium cooki, alveolar border of lower jaw and crown view of den-
tition. Carnegie Museum, No. 1841.
Fig. 7. Diceratherium cooki, alveolar border and crown view of dentition. Carnegie
Museum, No. 2476.
Fig. 8. Diceratherium cooki, inner view of mandible, very young stage of develop-
ment, Carnegie Museum, No. 1820.
Fig. 9. Diceratherium cooki, upper contour of lower jaw and crown view of den-
tition, same as Nos. 3 and 8.
Fig. 1 is J natural size; Figs. 2 and 4 are \ natural size; Figs. 3, 5, 6, 7, 8, and 9 are
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