a team of hoofed mammals distinguished the depth of the skins, like the elephant, hippopotamus, rhinoceros, tapir, horse, and hog; the pachyderms. It is currently considered an artificial group.
others:
The non-ruminant ungulate mammals, or hoofed quadrupeds that do not chew the cud; in Cuvier's classification, the 7th purchase of Mammalia, divided into Proboscidea, Ordinaria, and Solidungula.
How would you define pachydermata?