Scientists were wrong about this strange mammal for nearly 40 years

A remarkably complete fossil discovered in Mongolia's Gobi Desert is changing how scientists view mammal evolution during the age of dinosaurs. The newly identified species, described in the journal Nature by researchers from the American Museum of Natural History, Stony Brook University, University of Arizona, and Arcadia University, provides new evidence about an extinct group of mammals called zhelestids.

For decades, many scientists thought zhelestids were closely related to modern placental mammals. The new fossil suggests otherwise. Instead, zhelestids appear to have belonged to a very different branch of early mammals, overturning an interpretation that was based largely on fossil teeth.