Didelphimorphia

Didelphimorphia is an order of marsupials that comprises the opossums, the most widespread American marsupials. It is one of the oldest lineages of marsupials, with a fossil record dating to the Paleocene. Today, living members belong to the family Didelphidae, the opossums; the order also includes extinct families known from fossils. Opossums occur from the southern United States to South America, occupying a variety of habitats from forests to urban areas.

Didelphids range from small to medium-sized, with long snouts and often a semi-prehensile tail used for grasping branches. They are generally nocturnal and omnivorous. Reproduction involves a short gestation followed by the birth of highly altricial young that complete development in the mother’s pouch or by clinging to teats on her abdomen. The pouch is present in many but not all species. Litters are frequently large, and young may remain with the mother for several weeks to months after birth.

Didelphids are opportunistic feeders, consuming fruit, insects, small vertebrates, eggs, and carrion. They play roles as scavengers and, in some ecosystems, as seed dispersers. Some species display thanatosis, or playing dead, when threatened. Opossums are often tolerant of human presence and can help control pests, though they can also fall prey to larger carnivores. Conservation status varies by species; most opossums are of least concern, but habitat loss and introduced predators threaten certain populations.