Flatfoot in Jurassic Park

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Flatfoot in Jurassic Park
Flatfoot in Jurassic Park
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Flatfoot in Jurassic Park

Pterosaurs, long thought to be nimble "flying lizards", may have had flat feet and walked upright. This thesis paints a picture of an unterrifying predator that, when not taking to the skies, could only loiter clumsily. Pterosaurs soared into the Mesozoic skies until about 65 million years ago, around the time, according to popular theory, a meteorite impact wiped out the dinosaurs. Scientists have long debated how the lizards moved once they landed on the ground. Some say they ran erect on two toes like birds. Others argue that they crawled on all fours, like bats. But the pterosaur skeletons - flattened by the weight of the overlying rocks - never provided the information needed to end this debate.

One bone found at a prolific fossil site in the mountains of Tamaulipas, Mexico, may provide clues. In 1985, Rene Hernández of the Universidad Nacional Autónoma de México in Mexico City found the remains of a pterosaur buried under a mudslide 185 million years ago. This preserved the three-dimensional structure of much of the skeleton, including the right foot. The fossil was recovered three years later by Hernández, James Clark, a paleontologist at George Washington University in Washington, D. C., and other researchers.

When Clark and his colleagues examined the find, he noticed that the toe bone lacked the rounded joint needed for flexing-that is, the pterosaur could not lift its heels and stand on its toes (Nature, ed from 26. February 1998). The joint, Clark says, is designed to "not move." He thinks the pterosaur could walk upright, but it should have walked on the soles of its feet, much like a human. Or these animals would have sauntered along leisurely on all fours, as some putative pterosaur footprints seem to suggest.

But not all experts agree: "A joint rarely tells the whole story," says Kevin Padian, a paleontologist at the University of California, Berkeley. He explains that fossil footprints show that dinosaurs walked on their toes, although the fossil evidence indicates that their bone structure did not necessarily make them suitable as ballerinas.

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