Ancient reptile featured a crazy forelimb claw, study finds

A prehistoric reptile described as a cross between an anteater and a chameleon sported an odd, enlarged claw on its forelimb that likely helped it break into insect nests for food, according to new research published in the September 29 edition of the journal Current Biology.

The over 200-million-year-old creature known as Drepanosaurus featured the massive claw on the second digit of its forelimb, Adam Pritchard of the Yale University Department of Geology & Geophysics in New Haven, Connecticut and his colleagues explained in their new study.

“This animal stretches the bounds of what we think can evolve in the limbs of four-footed animals,” Pritchard, a postdoctoral researcher, said in a statement. “Ecologically, Drepanosaurus seems to be a sort of chameleon-anteater hybrid, which is really bizarre for the time. It possesses a totally unique forelimb.”

This unusual adaptation was confirmed following detailed analysis of Drepanosaurus arm fossils discovered at Hayden Quarry in Ghost Ranch, New Mexico, the authors noted. These new fossils are just the second known set of Drepanosaurus remains ever discovered, with the only other set described as a “badly crushed skeleton” found in northern Italy three decades ago.

Bone structure of creature’s arm completely different than relatives

Drepanosaurus, which is officially considered neither a dinosaur nor a lizard, shares a common ancestry with dinosaurs, lizards and crocodiles. It was between 1-2 feet long and was a member of the four-limbed, backboned creatures called tetrapods – but it wasn’t like other tetrapods.

As Pritchard and his colleagues explained, most tetrapods have a forearm comprised of a pair of bones, the radius and the ulna, which are elongated, run parallel to each other, and are connected to a series of shorter bones in the wrist. Drepanosaurus, however, has radius and ulna bones that are not parallel to one another and wrist bones that are actually longer than the radius.

“The bone contacts suggest that the enlarged claw of Drepanosaurus could have been hooked into insect nests,” the Yale researcher explained in a statement. “The entire arm could then have been powerfully retracted to tear open the nest. This motion is very similar to the hook-and-pull digging of living anteaters, which also eat insects.”

In addition, the reptile was said to have grasping feet and a claw-like structure located at the tip of its tail. According to the study authors, the discovery suggests that tetrapods had developed a series of specialized ecological roles dating as far back as the Triassic period roughly 200 million years ago.

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Image credit: Victor Leshyk

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