Deltatheridium is a small mammal that lives in trees. They resemble mice so they may have eaten insects, small reptiles and scavenge from carrion and come out at night. It is the ancestor of all Marsupials, it has a pouche where there child grows and leaves when it is capable of feeding for there self, but would return to there pouch when danger comes. They live in the Mongolian Desert during the late Cretaceous.