Pachydermata

The Pachydermata (meaning "thick skin") is an obsolete order of mammals described by Georges Cuvier and at one time recognized by many systematists. Because it is polyphyletic, the order Pachydermata is no longer in use, but it is important in the history of systematics. Although it is often described as an artificial grouping of unrelated mammals, it was recognised as a grade of hooved mammals to the exception of other Ungulates by zoologists such as Charles Darwin, and anatomical characters do support the affinities of "Pachyderm" mammals to each other and to other Ungulates.

Cuvier's Pachydermata included the mammals now placed within Perissodactyla, Hyracoidea, and Proboscidea, as well as the Suina within Artiodactyla. Therefore modern "Pachydermata" would be represented by the horse and their relatives, the tapir, the rhinoceros, the elephant, the hippopotamus, the peccary and the pig.

The term "pachyderm" is used informally, usually to describe Elephants and sometimes for Rhinoceros, and Hippopotamus.