精选优质文档-倾情为你奉上 Passage 4 (4/63)The fossil remains of the first flying vertebrates, the pterosaurs, have intrigued paleontologists for more than two centuries. How such large creatures, which weighed in some cases as much as a piloted hang-glider and had wingspans from 8 to 12 meters, solved the problems of powered flight, and exactly what these creatures werereptiles or birdsare among the questions scientists have puzzled over.Perhaps the least controve
