Curved claws hint at pterosaur habits

From Norman, Okla., at a meeting of the Society of Vertebrate Paleontology

A study of the claws of ancient flying reptiles known as pterosaurs suggests that some of the creatures may have walked like present-day herons and used claws on their wings to hold prey.

In modern birds, claw curvature is closely correlated with the animal’s behavior, says David A. Krauss, a paleobiologist at Boston College. Birds that cling to and climb the sides of trees, like woodpeckers and nuthatches, have strongly curved claws. Birds that walk on the ground, like shorebirds, have relatively straight claws. Perching birds have claw curvature that lies between that of walkers and climbers, Krauss notes.

Pterosaurs had claws both on their feet and on their wings. An analysis of more than 100 museum specimens shows that the curvature of claws on pterosaurs’ wing fingers was, on average, comparable to that of perching birds. Claws on the pterosaurs’ feet, however, were almost straight, like those of birds that walk on the ground. This combination hints that pterosaurs didn’t live in trees, says Krauss.

Scientists have long debated whether pterosaurs walked bipedally as people do or scrabbled along the ground on all fours as bats sometimes do. Krauss and his colleagues contend that pterosaurs walked upright but used their curved wing claws to hold prey steady while they consumed it. Such a technique would have helped prevent wriggling meals from snapping off the pterosaur’s delicate teeth.

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