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

A new fossil from Mongolia’s Gobi Desert has reshaped mammalian evolutionary understanding. This 70-million-year-old Tamirkhan balcarceli fossil belonged to zhelestids, which were previously misunderstood. The complete skeleton shows zhelestids were not early placental mammals as once thought. Instead, they were part of the extinct zalambdalestoid lineage, which evolved similar teeth independently. This discovery alters interpretations of mammalian diversity during the Late Cretaceous period.