Placental mammals had long been thought to have come well after the extinction of the dinosaurs, but fossils of Kulbeckia, a long snouted animal from 85 million years ago, shows signs of being an ancestor of modern rabbits and rodents. Including the possibility of having developed its young in its uterus instead of a pouch or eggs.

This is a great change in the more commonly accepted timeline of mammalian development, and means that the most developed form of mammalian reproduction was going on well before the death of the dinosuars, instead of developing in the wake of the extinction as previously thought.