70-million-year-old mammal fossil discovered in Mongolia rewrites the story of early mammal evolution

The fossil record has a habit of reshaping ideas that once seemed settled. In the Late Cretaceous, long before the extinction of the dinosaurs, small mammals occupied a world dominated by much larger reptiles. Most left behind little more than isolated teeth and fragments of bone, making it difficult to understand how they were related to one another. A newly described specimen from Mongolia's Gobi Desert has changed that picture. About 6 inches (roughly 15 centimetres) long, the animal looked broadly rabbit-like in its proportions, yet its ancestry tells a different story. According to a new study published in Nature, titled “Cretaceous zhelestid mammals are zalambdalestoids”, the remarkably complete fossil suggests that this tiny mammal belonged to a separate branch of early mammalian evolution rather than being closely linked to the ancestors of modern placental mammals.70-million-year-old Tamirkhan balcarceli fossil solves the mystery of zhelestid mammalsThe new species, Tamirkhan balcarceli, is unusual because its skull, teeth and parts of its hind limbs all belong to the same individual. According to the study, that combination has never before been available for a member of ...