Historical reference: Do not rely on this information. It is very old. About this collection
Artiodactyla, a section of Ungulata (q.v.), containing those in which the number of toes is even - two or four - and the third digit on each limb forms a symmetrical pair with the fourth. The two-toed Artiodactyla comprise the ruminants and the pigs; the only living four-toed members of the section are the hippopotami.