New ideas in ungulate phylogeny and evolution.

Most of the ungulates (hoofed mammals) that survive today belong to the orders Artiodactyla (even-toed ungulates) or Perissodactyla (odd-toed ungulates), and are known for their herbivorous specializations (e.g. the ruminant type of stomach), for their large body size (e.g. hippos or rhinos) or for their fleetness of foot (e.g. antelope or horses). Yet these present-day examples represent the specialized end-points of a large Tertiary radiation of hoofed mammals. There was a bewildering variety of small generalized early Tertiary forms, even including some carnivorous taxa. In addition, some specialized island continent ungulate radiations are now either entirely extinct (the South American ungulates), or are represented by only a few living members (the African 'subungulates'). Recent fossil discoveries, and advances in phylogenetic systematics, have reopened a number of issues in ungulate classification, which have affected our views not only on ungulates themselves, but also on patterns of Tertiary biogeography and evolution.