A group of researchers discovered the fossilized remains of a flying mammal that appears to have lived 130 million to 165 million years ago. Since the earliest flying birds are believed to have appeared about 150 million years ago, researchers concluded that birds and mammals began to fly at about the same time. This conclusion would be most weakened by evidence of which of the following? (SC.7.L.15.1) 100-million-year-old fossil of a flying bird 120-million-year-old fossil of a flying bird A 160-million-year-old fossil of a flying mammal A 200-million-year-old fossil of a flying mammal