An order of nonruminant ungulate mammals; such as, the horse (with one toe), the tapir, or the rhinoceros (with three toes), that usually have an odd number of toes, molar teeth with transverse ridges on the grinding surface, and posterior premolars resembling true molars.

The middle digit bears the weight of the body. These herbivorous mammals typically have feet encased in a protective horny hoof, lips adapted for plucking, strong cropping incisor teeth, and molars and premolars adapted for chewing.

The stomach is simple and bacterial digestion of cellulose occurs in the cecum, a blind pouch at the junction of the ileum and the colon.

Such herbivores rely on the activity of millions of symbiotic bacteria living in the cecum. These produce enzymes capable of digesting cellulose and releasing simple soluble substances that can be absorbed into the bloodstream.