1911 Encyclopædia Britannica/Palaeotherium
PALAEOTHERIUM (i.e. ancient animal), a name applied by Cuvier to the remains of ungulate mammals recalling tapirs in general appearance, from the Lower Oligocene gypsum quarries of Paris. These were the first indications of the occurrence in the fossil state of perissodactyle ungulates allied to the horse, although it was long before the relationship was recognized. The palaeotheres, which range in size from that of a pig to that of a small rhinoceros, are now regarded as representing a family, Palaeotheriidae, nearly related to the horse-tribe, and having, in fact, probably originated from the same ancestral stock, namely, Hyracotherium of the Lower Eocene (see Equidae). The connecting link with Hyracotherium was formed by Pachynolophus (Propalaeotherium), and the line apparently terminated in Paloplotherium, which is also Oligocene. Representatives of the family occur in many parts of Europe, but the typical genus is unknown in North America, where, however, other forms occur.
Although palaeotheres resemble tapirs in general appearance, they differ in having only three toes on the fore as well as on the hind foot. The dentition normally comprises the typical series of 44 teeth, although in some instances the first premolar is wanting. The cheek-teeth are short-crowned, generally with no cement, the upper molars having a W-shaped outer wall, from which proceed two oblique transverse crests, while the lower ones carry two crescents. Unlike the early horses, the later premolars are as complex as the molars; and although there is a well-marked gap between the canine and the premolars, there is only a very short one between the former and the incisors. The orbit is completely open behind. In other respects the palaeotheres resemble the ancestral horses. They were, however, essentially marsh-dwelling animals, and exhibit no tendency to the cursorial type of limb so characteristic of the horse-line. They were, in fact, essentially inadaptive creatures, and hence rapidly died out.
- (R. L.*)