Titanotheres are represented in our collection by the skeletons of the large, horned type which was the last of the race and destined to extinction by the middle of the Oligocene period. Smaller hornless varieties of Eocene time are illustrated by skulls. This family of ungulates had an unprogressive dental equipment, and a small brain in a flattened skull. The molar teeth readily distinguish the group from other ungulates and enable us to trace the relationship between earlier and later varieties. These teeth were of a type which is soon destroyed by wear, and it is evident that the animals survived only so long as their environment provided them with an abundance of soft vegetation.
Titanotheres of Oligocene Time
The name of these animals refers to the large size though they were greatly exceeded in bulk by the mastodons and mammoths of later periods. Ancestral titanotheres, dating back to the Eocene, were hornless animals of much smaller size. These splendid specimens were obtained in Weld County, Colorado.
The large assortment of rhinoceros material provides an idea of the great abundance and variety of forms in this family which was once prominent in North America but no longer among the inhabitants of that continent. Some of the mounted skeletons have been restored on one side to show how these animals appeared in the flesh.
Of the even-toed ungulates there are also several types illustrated by complete skeletons. Merycochoerus, the subject of one of our mounted groups, represents the oreodonts, a large family of mammals whose history begins with the Upper Eocene and ends in the Lower Pliocene. The oreodonts were small animals, rather pig-like in form and quite common in the western plains region shortly after the time of the titanotheres. Ancient swine are represented in our exhibits by two mounted skeletons which were obtained from northeastern Colorado, where the bones were found associated with rhinoceros and titanothere remains. Some of these animals were of very large proportions, and the entire family is commonly known as the “giant pigs.”
Camels and closely related forms were quite abundant in North America from early Oligocene to comparatively recent time. Numerous types were developed during the course of their history, some small and delicately formed, others tall and clumsy and much like the giraffe in structure. Parts of many of these creatures have been found but the only completely prepared skeletons in our collection are of the little gazelle-camel, Stenomylus, from Lower Miocene deposits in northwestern Nebraska. Pleistocene bisons are represented by several complete skeletons and numerous skulls and horncores, some of the species showing an extreme development in the length of horns. With two of the bison skeletons are shown prehistoric weapon points, found with the bones and indicating that these animals were hunted by primitive men at some time near the close of the Ice Age. The artifacts first discovered near Folsom, New Mexico, by field workers of our Museum, have become known to archeologists as Folsom points.
PREHISTORIC HORSES
The past history of horses is well known from an abundance of fossil material, ranging in age from the Eocene down to the present. Modern horses have only one toe in each foot, but there are remnants of two additional toes which may be seen only in the bony structure underlying the skin. Most of their ancestral relatives were three-toed as far back as the Oligocene period. During Eocene time, however, there was a stage which may be regarded as four-toed although it was evidently a temporary condition, linking known horses with more remote forms having five toes.
