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Reprinted from the PRocEEDINGS oF THE NaTIONAL ACADEMY OF SCIENCES,
Vol. 5, pp. 250-252, July, 1919

SEVENTEEN SKELETONS OF MOROPUS; PROBABLE HABITS OF
THIS ANIMAL

By Henry FAIRFIELD OSBORN
AMERICAN Museum OF NATURAL History, NEw York CIty

Read before the Academy, April 29, 1919

Moropus is an aberrant perissodactyl, closely related to the family of the
Titanotheres and more remotely to that of the Horses. It occurs in the
Lower Miocene age in France and North America, and its ancestors have been

PALEONTOLOGY: H. F. OSBORN 251

traced back to the Upper Eocene in both countries; it is thus of Holarctic
distribution, and while very rare, it must have been perfectly adapted to its
environment, because it survived the majority of perissodactyls and occurs in
the Pliocene of Europe and England and will not improbably be found in
the North American Pliocene.

The habits and habitat of the animal have always presented a very difficult
problem. The skeleton presents the most noteworthy exception to Cuvier’s
law of correlation. All the foot bones which were discovered since Cuvier’s

FIG. 1

Mounted skeleton of Moropus cookei in The American Museum of Natural History. One
of the seventeen. Drawing one twenty-sixth natural size.

time consisted of large deeply-cleft terminal phalanges and were grouped
with the edentates, especially the plantigrade sloths. All the teeth which
were discovered, on the other hand, were grouped with the perissodacty]
ungulates. It was not until H. Filhol discovered the nearly complete skeleton
of Macrotherium that he was enabled to prove that the chalicotheres were of
composite adaptive structure, with the teeth of perissodactyls and the claws
of edentates. Macroiherium is very similar to the American Moropus.

Great light was thrown upon the structure of Moropus through the explora-
tions of the Carnegie Museum by Holland and Peterson, described in 1914,
from materials collected in the famous Agate Spring Quarry, Sioux County,

252 PALEONTOLOGY: H. F. OSBORN

Nebraska, discovered by James H. Cook in 1897. After the lapse of the
Carnegie researches and explorations, the American Museum entered this
quarry and through five years of continuous exploration (1911-1916) an
irregular area within a square of about 36 feet yielded nearly complete skulls of
ten individuals and skeletal parts of seventeen individuals all together. From
this wonderful material it has been possible to supplement the descriptions of
Holland and Peterson and to present for the first time the proportions and
pose, by which we may estimate the habits of this animal. We reach the
conclusion that the Moropus type was not plains living, but forest living;
that it was the seclusion of the forests which protected this type and which
accounts for its great rarity in fossil deposits, for it is characteristic of forest-
living forms that they are not readily entombed. We form an entirely dif-
ferent conception of the habits of the animal when we observe the extremely
long fore limbs, which are not of the digging or fossorial type, and which
thus belie the apparently fossorial or digging structure of the terminal pha-
langes. It appears more probable that these terminal claws were used partly
for purposes of offense and defense, but largely for the pulling down of the
branches of the trees. The animal was probably forest living like the African
okapi, with which in its general body and head proportions it has many anal-
ogies. Like the okapiit survived through retreat to the recesses of the forests.

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