Pterosaur Liftoffs

摘要

How did pterosaurs get off the ground? The giant flying reptiles had four legs, the front ones attached tp sail-like wings, and could weigh 70 kilograms or more-far more than any bird. "People have tried to fit pterosaur into a birdlike model," taking flight with two-legged leaps, says paleontologist David Unwin of the University of Leicester, U.K. But some scientists think pterosaurs must have pushed off with all four feet, as modern vampire bats do. Now paleontologist Michael Habib of Johns Hopkins University in Baltimore, Maryland, has done the math to show that a "quadrupedal launch" is indeed plausible. Habib ana- lyzed bone strength by comparing measurements from three pterosaur species with those from 20 bird species. In a paper in the journal Zitteliana, he reports that the leg bone (femur) becomes proportionately thicker than the wing bone (humerus) in heavier birds, which need more leg muscle to take off.