Didelphis

Didelphis is a genus of New World marsupials. The six species in the genus Didelphis, commonly known as Large American opossums, are members of the opossum order, Didelphimorphia. The genus Didelphis is composed of cat-sized omnivorous species, which can be recognized by their prehensile tails and their tendency to feign death when cornered. The largest species, the Virginia opossum (Didelphis virginiana), is the only marsupial to be found north of Mexico. The Virginia opossum has opposable toes on their two back feet. One of the synapomorphies of this genus is the hypertrophied spinous processes of the cervical vertebrae, which also interlock. As a result, this prevents any movement of the neck. The purpose of this is not yet fully understood.