The ungulates and their relatives are a puzzling group,
including animals as diverse as whales and hippos, elephants and
hyraxes, horses and tapirs, giraffes and sheep. What they have
in common is that many of them walk around on their toenails.
The phylogeny (family relationships) of the ungulates is a
constantly shifting terrain, but genetic analysis is beginning
to help sort out this enigmatic group of animals. At WhoZoo,
elephants, hippos and rhinos have been grouped for convenience
as "large herbivores," but this is an artifical grouping; these
animals actually represent three different branches of hooved
animals. The simplified family tree below is redrawn from the
cladograms and other information at the University of California
Museum of Paleontology Web Site and from an article on mammalian
phylogeny in Nature (1 February 2001). The three main branches
of the tree below are the Cetartiodactyla, the Perissodactyla
and a part of the recently defined Superorder Afrotheria, which
includes the Orders Probo