Most occupy Central and South America, but one species, Didelphis virginiana , occurs through most of the continental United States. Living didelphimorphs are small to medium in size. Their canines are large.
Molars are tritubercular with well developed talonids .
The tail is prehensile and usually long and scaly. Opossums have relatively long rostrums , a small braincase , and often, a prominent sagittal crest . Many opossums have a well-developed pouch, but some lack this structure. Their stomachs are simple. Most members of this group are omnivorous or carnivorous.