(cohort Ferungulata, superorder Protoungulata)
An extinct order of S. American ungulates that lived from the Eocene to the Pleistocene and are considered to be descendants of the Condylarthra. They were hoofed, and the central metapodials became elongated and the lateral ones reduced to leave three toes and, in Thoatherium, one. The incisors were reduced in some forms, but in most dentition was complete. One line developed remarkable ‘pseudo-horses’ (e.g. Diadiaphorus and Thoatherium) which strongly resembled their perissodactyl contemporaries. The other major lineage culminated in Macrauchenia, which strongly resembled the N. American camels, apart from the possible presence of a short, tapir-like trunk. From the presence of a nasal opening on the top of the skull, however, other authorities have inferred that Macrauchenia followed a life in water, rather than one that involved a trunk.
Subjects: Zoology and Animal Sciences.