Didelphodon

Throughout the history of life on earth, marsupials have been mostly confined to two continents: Australia (where the vast majority of pouched mammals live today) and Cenozoic South America. However, one family of marsupials--the pint-sized opossums--have prospered in North America for tens of millions of years, and are represented today by dozens of species. Didelphodon (Greek for "opossum tooth"), which lived in late Cretaceous North America alongside the last of the dinosaurs, is one of the earliest opossum ancestors yet known; as far as we can tell, this Mesozoic mammal wasn't significantly different from its modern descendants, burrowing underground during the day and hunting for insects, snails and possibly the hatchlings of prehistoric turtles at night. 
One of the odd things about Didelphodon is that it was apparently suited to a semi-aquatic lifestyle: the recently discovered skeleton of a nearly intact specimen, recovered near a Triceratops individual, reveals a sleek, otter-like body equipped with a Tasmanian Devil-like head and strong jaws, which may have been used to feast on mollusks in lakes and rivers, as well as insects, plants, and pretty much anything that moved. However, one shouldn't take Didelphodon's guest appearances on animated TV documentaries too literally: in one episode of Walking with Dinosaurs, this tiny mammal is depicted unsuccessfully raiding a clutch of Tyrannosaurus Rex eggs, and an installment of Prehistoric Planet shows Didelphodon scavenging the carcass of a juvenile Torosaurus!
Category:Mammals
Category:Marsupials
Category:Mesozoic Animals
Category:Montana Animals
Category:Cretaceous Animals