Date: September 29, 2016
Source: Yale University
Newly recovered fossils confirm
that Drepanosaurus, a prehistoric cross between a chameleon and an anteater,
was a small reptile with a fearsome finger. The second digit of its forelimb
sported a massive claw.
Scientists analyzed
212-million-year-old Drepanosaurus arm fossils that were discovered at the
Hayden Quarry in Ghost Ranch, New Mexico. The researchers describe their
findings in a paper in the Sept. 29 edition of the journal Current Biology.
Drepanosaurus is neither a
dinosaur nor a lizard. It is a one- to two-foot long reptile from an extinct
group of animals called drepanosaurs, and shares a common ancestry with
lizards, crocodiles, and dinosaurs. The only other known Drepanosaurus fossil
was a badly crushed skeleton found in northern Italy more than 30 years ago.
"This animal stretches the
bounds of what we think can evolve in the limbs of four-footed animals,"
said Adam Pritchard, a postdoctoral researcher at Yale and first author of the
study. "Ecologically, Drepanosaurus seems to be a sort of
chameleon-anteater hybrid, which is really bizarre for the time. It possesses a
totally unique forelimb."
Four-limbed animals with a
backbone are called tetrapods. In nearly all tetrapods, the forearm is made up
of two, elongate and parallel bones -- the radius and the ulna. These bones
connect to a series of much shorter, wrist bones at the base of the hand.
Drepanosaurus, however, has
radius and ulna bones that are not parallel. Instead, the ulna is a flat,
crescent-shaped bone. Also, the two wrist bones that meet the end of the ulna
are long rather than short. They are longer than the radius, in fact.
"The bone contacts suggest
that the enlarged claw of Drepanosaurus could have been hooked into insect
nests," Pritchard said. "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."
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