Didelphodon

A Didelphodon is a small marsupial from the Late Cretaceous Period.

This primitive, badger-sized mammal had to live in the world that was dominated by the dinosaurs. It was about a meter in length and like most mammals of the Mesozoic it was an omnivore. Among other things, this meant that when food was scarce (as it was before the K/T mass extinction), all mammals had to do is scavenge meals from the dinosaurs such as Tyrannosaurus and Dromaeosaurus.

Eventually Didelphodon helped pave the way for the Cainozoic mammals to eventually conquer the world. Unfortunately, Didelphodon itself became extinct about the same time as the dinosaurs.

In Walking with Dinosaurs
Several Didelphodon appeared in the last episode of this series: one of them was eaten by a Tyrannosaurus, and several others fought over the abandoned Tyrannosaurus nest later in the episode.