Scientists have long puzzled over how snakes, with
their slithery bodies and incredible jaws, evolved from lizards, but a
new finding of a giant, extinct reptile appears to explain the
evolutionary link.
Researchers have determined that mosasaurs, 45-foot marine lizards
that lived about 100 million years ago, had flexible lower jaws like
snakes and long, snake-like teeth to grip other critters. Findings are
presented in the current issue of the journal Nature.
According to the report, jaw movement studies on a mosasaur fossil
reveal that this huge Cretaceous reptile would get its dinner by
biting onto large marine prey, such as sea turtles and other species
of mosasaurs. Keeping a good tooth-hold, it would then manipulate its
lower jaw and teeth to shove the creature down its esophagus.
Today, snakes eat using a similar process, only they also have a
hinged, flexible upper jaw that allows them to wrap their entire skull
around large prey.
Mosasaurs likely developed this dining technique because, as marine
dwellers, they would have had a hard time dismembering prey in the
water, says Gorden Bell, paleontologist with the Museum of Geology at
the South Dakota School of Mines and Technology and one of the
report’s authors.
"Competitors also would try to steal food right out of their
mouths, so mosasaurs had to swallow it as soon as possible," he
adds.
Bell and his colleagues think that mosasaurs were the nearest
relatives of snakes, and that both reptiles shared a common ancestor,
which is unknown at this point. Their theory goes against the popular
belief that small burrowing lizards represented the intermediate stage
of snake evolution.
In addition to the jaw and teeth similarities, the vertebrae of
modern snakes resemble that of mosasaurs. Bell says the extinct giant
reptiles slithered along in the water just as snakes do today on land.
Eric Pianka, professor of zoology at the University of Texas at
Austin, thinks the report is "really interesting" and brings
up an important subject, snake evolution.
"Here we are, almost at the year 2,000, and we still don’t
know exactly where snakes come from," says Pianka. "This
report brings us a step further in attempting to reconstruct the snake
family tree.
Pianka hopes researchers in the future will be able to analyze
mosasaur DNA, possibly from a fossil tooth, to prove the snake
connection theory.
By Jennifer Viegas, Discovery News Brief
