The discovery of a primitive, shrew-like mammal fossil in Mongolia has revived the view that its modern mammal cousins arrived just as the dinosaurs made their dramatic exit about 65 million years ago, U.S. researchers said on Wednesday.
Recent studies have placed the arrival of modern mammals at anywhere from 140 million to 80 million years ago, long before an asteroid crashed into Earth and wiped out the dinosaurs. "The fossil itself is the least interesting part of the story scientifically," said John Wible of the Carnegie Museum of Natural History in Pittsburgh, whose research appears in the journal Nature.
He said the discovery of a new shrew-like mammal in 1997 -- Maelestes gobiensis -- led to an exhaustive analysis of the fossil record that dates the emergence of modern mammals at the end of the Cretaceous period 65 million years ago.