Sub-Order 3. Ancylopoda

The history of the discovery of the members of this order is very instructive as illustrating the dangers of laying too much classificatory importance upon detached fragments of animals. So long ago as 1825 terminal phalanges of a new creature were found in the Miocene of Eppelsheim, and sent to Cuvier. Cuvier named them "Pangolin gigantesque," deeming them, on account of their general form and cleft terminations, to pertain to the Edentata. In the same bed some seven years later were found certain teeth clearly of an Ungulate character, to which the generic name of Chalicotherium was applied. It was subsequently discovered that the teeth and the claws belonged to the same animal, and, later, further remains turned up which disclosed a creature having the anomalous composition of an Ungulate with decisively Ungulate teeth, but with the feet to a large extent like those of an unguiculate animal. The same confusion of characters occurs also, it will be remembered, in the distinctly Artiodactyle Agriochoerus (see p. ). Indeed the feet of the latter when first discovered were erroneously, as it now appears, referred to the present order of Ungulates under the name of Artionyx. It is probable that the genus Moropus of North America is a member of this group, and that it is probably congeneric with a somewhat different type of Ancylopod known as Macrotherium. It is also clear that Anisodon, Schizotherium, and Ancylotherium, if not congeneric with either of the two recognised genera, are at least very close to them.

Chalicotherium has a skull which recalls that of some of the earlier Ungulates; it has, however, no incisors at all, and no canines in the upper jaw; this feature has led to the belief that the animal is related to the Edentata, and that it is in fact a link between them and the Ungulata. The molars, like those of the Perissodactyla, are of the buno-selenodont type. It also agrees with that group (to which it has been approximated by several writers) in the. tridactyl manus and pes, and in the characters of the tarsus. But although tridactyl, the axis of the limb passes through the fourth digit. Chalicotherium is not mesaxonic, as are the Perissodactyles. Moreover, it has no third trochanter, and the unguiculate claws have already been referred to. As to the latter, which are short, it is not the end phalanx but the first which is retracted; thus Chalicotherium differs markedly from both Carnivorous and Edentate types; for in the former it is the last phalanx which is retracted, while in the Edentates the same phalanx is flexed downwards. The limbs of Chalicotherium are nearly of the same size, and the animal seems to have been stout and quadrupedal.

Macrotherium, like the last genus, seems to have been common to both New and Old Worlds. It is to be distinguished by a number of characters. It is supposed to have been "semi-arboreal and fossorial"; the fore-limbs are much longer than the hind, the relative proportions of the radius and tibia being 70 to 29. The ulna was distinct from the radius, whereas in Chalicotherium the two are coalesced, or nearly so. Young specimens appear to possess a full set of incisors; whether this is the case or not with Chalicotherium is not known.

Homalodontotherium is sometimes placed in the group.