Pachydermata
Pachydermata (pak`i*dẽr"mȧ*tȧ) , noun, plural
[New Latin, from Greek pachy`dermos thick-skinned; pachy`s thick + de`rma skin.]
(Zoology) 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.