Artiodactyls tend to share a number of cranial and dental characteristics, but the group is so diverse that there are exceptions to each trait. Horns or antlers are often present, usually on the frontals , which are usually larger than the parietals . All artiodactyls have a postorbital bar or process. The number of teeth is variable, but in many species it is smaller than the number found in perissodactyls. A diastema usually separates anterior and posterior teeth, especially in the lower jaw.
Cheek teeth are bunodont in some forms, but more commonly selenodont .
The premolars tend to be relatively small and not fully molariform. Most artiodactyls have modified stomachs , the extreme case being that of groups such as antelope and deer, which have distinctive, four-chambered stomachs. This arrangement appears to be an adaptation that allows members of these groups to make use of microorganisms to decompose cellulose into digestible components. Cellulose is an important constituent of plant tissue that most mammals cannot digest. Artiodactyls are native to all continents except Australia and Antarctica.