- Kingdom Animalia
- Phylum Chordata
- Class Mammalia
- Order Artiodactyla
- Family Hippopotamidae
Hippos
http://users.tamuk.edu/kfjab02/Biology/Mammalogy/systematics/A7artiodactyla.htm
as of 2002-07-10
Hippopotamuses are the only extant artiodactyls which walk on four toes on each foot.