Pachydermata /(păk`ĭ*dẽr"mȧ*tȧ)/

Pach·y·der·ma·ta

Pachydermata

n. pl.
  1. A group of hoofed mammals distinguished for the thickness of their skins, including the elephant, hippopotamus, rhinoceros, tapir, horse, and hog; the pachyderms. It is now considered an artificial group. (Zool.)