Class Mammalia and Order Didelphimorphia

The order Didelphimorphia includes opossums, characterized by having five toes on each foot; tail more or less prehensile, in many species with less than the proximal half of the tail furred, the remainder is naked; hallux of hindfoot clawless, opposable to the other digits; a great number of species with a pouch, others present two folds of skin instead; five upper subequal and four lower incisors; snout long and pointed; preorbital region long and pointed and braincase small; zygomatic arches large; hard palate with fenestrae near the molars; upper molars tritubercular; lower molars tritubercular with well-developed trigonids; epipubic bones present. Distribution is restricted to America. The only family is Didelphidae.