Scientists say they've discovered the oldest, most primitive member
of a family of flying reptiles that ruled the Cretaceous skies. The find
has raised controversy, but even critics agree it could help shed light
on how these beasts became the kings of the air.
The species
dates back 163 million years, making it the earliest known
representative of the most important lineage of pterosaurs, winged
creatures often referred to as dinosaurs though they aren't actually.
Many of the pterosaurs that came later were enormous, flamboyant or
both. The new pterosaur was, at best guess, a plain fellow of modest
proportions.
"His wings were only about 4½ feet wide, so he had a
smaller wingspan than I do," says University of South Florida
paleontologist Brian Andres, leader of the team reporting the find.
"From what we can tell, he was a small, unimposing guy. But out of small
things, big things sometimes come."
The fossil of the animal was
discovered in northwestern China in a remote region near the Gobi Desert
where summer temperatures reach 125 degrees and snow is liable to fall
in September. The scenery was a backdrop for the movie Crouching Tiger, Hidden Dragon,
prompting the scientists to sneak a film reference into the new
animal's scientific name, Kryptodrakon progenitor. "Kryptodrakon" means
"hidden serpent," and "progenitor" means "ancestral" or "firstborn." In
Kryptodrakon's day, rivers, ferns and trees dotted the now-barren area,
and Andres speculates the animal dined on insects or fish.
Kryptodrakon
may not have been the most impressive reptile on the block, but its age
and place in the pterosaur family tree make up for its lack of flash.
Pterosaurs had been around for 60 million years when a new type of
pterosaur elbowed its way onto the Jurassic scene. These newcomers,
known as the pterodactyloids, were a radical departure from their
predecessors. They had longer skulls and shorter tails than the
primitive, old-school pterosaurs; even their brains were different. The
geezer pterosaurs soon went extinct. The Johnny-come-lately
pterodactyloids prospered, evolving into about 150 wildly diverse
species. The biggest pterodactyloids rivaled small airplanes in size,
while the fanciest bore crests that resembled towering mohawks and
unfurled sails.
"They take over the skies and they become the
largest flying organisms we know of," Andres says. "They were large, and
they were in charge."
Scientists haven't known much about the
origins of the pterodactyloids, and Kryptodrakon may help. It's the
earliest known pterodactyloid, Andres and his colleagues say in this
week's issue of Current Biology, predating the next oldest of its
kind by about 5 million years. The scientists say Kryptodrakon's body
plan shows that one of the clan's secrets to success was an extra-long
bone attached to the "wing finger," which served as the scaffolding for
the animal's wing membrane. That longer bone allowed the pterodactyloids
to try out a wide variety of wing shapes for navigating different
habitats. The scientists concluded, based on an analysis of the entire
pterosaur family tree, that pterodactyloids arose in inland habitats, in
contrast to more primitive species, which were mostly creatures of the
sea and the coast.
Outside opinion is mixed. Paleontologist David
Hone of Queen Mary University of London says he has no doubt that
Kryptodrakon is a new species from a crucial time period, and the new
study makes a "convincing case" that pterodactyloids arose away from the
sea.
David Unwin of Britain's University of Leicester worries
that the "fossil" may actually be a mix of bones from more than one
animal. He says that even if the fossil is all of a piece, it may not be
a pterodactyloid at all but a more primitive pterosaur. Andres responds
that the fossil is definitely a pterodactyloid and definitely belongs
to only one animal.
"It's going to be a very contentious fossil,"
predicts Unwin, author of a book on the pterosaurs. "But it will still
be very interesting in terms of our understanding of pterosaurs. … It's a
good thing we have the fossil."
No comments:
Post a Comment