Science News - November 6, 2010

11,680 kilometers

Longest recorded nonstop ;ight by a bird

3. 5 meters

Top wingspan of great albatross

10 meters

Estimated wingspan of Q. northropi

Snails shed shells
in one fell swoop

Common evolutionary step
among mollusks likely a leap
slugs. The internal bonelike structure
in cuttlefish and squid, for example, is
thought to be a pared-down version of an
ancestral outer molluscan shell.

Though the new study shows that shell loss in gastropods can happen in one fell swoop, it also suggests that another evolutionary transition might have required several steps to complete. Torsion is an anatomical hallmark of the gastropods that makes them look like their bottom halves were rotated 180 degrees relative to their top halves, putting their anuses over their heads. The term torsion also refers to the hypothetical evolutionary process that purportedly led to this awkward anatomy, says evolutionary

By Rachel Ehrenberg

Evolution doesn’t have to operate at a snail’s pace, even for snails. In recent experiments designed to simulate the evolutionary transition that produced slugs, researchers exposed baby snails to the metal platinum, causing the animals to develop without external shells.

The simple experiments illustrate how a big leap in the history of animal body plans might have occurred. The research also reopens a can of worms concerning the development and evolution of an entire class of shelled creatures.

Scientists reared common aquarium snails in petri dishes containing varying concentrations of platinum. At certain exposures, all of the roughly 80 percent of snails that survived were shell-less, Heinz Köhler of the University of Tübingen in Germany and his colleagues report in the September-October Evolution & Development. The researchers posit that the platinum is causing effects similar to the genetic mutation that turned off shell production in some ancient snails, paving the way for their slug descendants.

“This shows that you can get really dramatic changes that could be similar to the genetic mutations that drive evolution, without worrying about doing everything in small incremental steps,” says Roger Croll of Dalhousie University in Halifax, Nova Scotia.

Evidence suggests that transitions
from having a concrete outer shell to a
greatly reduced internal one have hap-
pened numerous times in evolution. Such
losses or gains occurred repeatedly within
the Mollusca, an enormous group that
includes clams, oysters, squid, octopuses
and of course the gastropods — snails and
biologist Louise Page of the University
of Victoria in British Columbia, Canada.

Wide-bodies flew Cretaceous air
Study suggests pterosaurs could soar halfway around globe

These supergiants “are big by ptero-
saur standards,” Habib said. “They are
truly gruesomely huge by bird and bat
standards.”
If current estimates for pterosaur body
masses and wing dimensions are realis-
tic, and if the pterosaurs could catch
thermals and glide the way a bird can, “it
would make them the longest single-trip–

distance fliers in the Earth’s history,”
Habib said. Birds such as Arctic terns can
migrate pole to pole, but not nonstop.
Habib’s calculations raise the possi-
bility that supergiant pterosaur fossils
found on separate continents can’t
automatically be considered differ-
ent species. “A pterosaur from Big
Bend [Texas] could be mating with
a pterosaur from Transylvania.”
The mating idea may be a
stretch, said researcher David
Unwin of the University of
Leicester in England, but
“we didn’t fall on the floor
laughing” at the notion
that pterosaurs could
have flown 10,000 miles
without stopping.

s
t
ent species. “A pterosaur from Big
Bend [Texas] could be mating with
a pterosaur from Transylvania.”
The mating idea may be a
stretch, said researcher David
Unwin of the University of
Leicester in England, but
“we didn’t fall on the floor
laughing” at the notion
without stopping.

By Susan Milius

PITTSBURGH — Predating jet travel by at least 65 million years didn’t stop the biggest pterosaurs from racking up miles. These prehistoric creatures may have been able to fly 10,000 miles or more nonstop, according to research presented October 10 at the annual meeting of the Society of Vertebrate Paleontology.

The original elite fliers included four species of what biomechanist Michael Appearing in the fossil record about 70 million years ago, they stood about as tall as a modern giraffe and soared through the air by spreading membrane wings to a span of roughly 10 meters.