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New Dino Papers and News
From: Ben Creisler firstname.lastname@example.org
New Dino Papers and News:
Here are few recent items I have come across that may not
have been mentioned here:
Galis, F. 2001. Digit identity and digit number: indirect
support for the descent of birds from theropod dinosaurs.
Trends in Ecology & Evolution. 16 (1): 16.
A short piece discussing another article and its
implications for resolving the digit problem in modern
birds. "In a new paper, Drossopoulou et al. now present
evidence for the developmental independence of the
determination of digit number and digit identity. In an
elegant experiment, they demonstrate that the important
gene Sonic hedgegoh (Shh) is initially involved in the
determination of the number of digits and later on in the
specification of digit identity via the induction of Bmp
genes...Although the evidence is far from complete, these
results indirectly support the hypothesis of Wagner and
Gauthier. They prove the underlying assumption that
homeotic changes in the identity of digits are possible
and can occur without change in digit number." The
original paper referred to is:
Drossopoulou, G. et al. (2000) A model for anteroposterior
patterning of the vertebrate limb based on sequential long-
and short-range Shh signalling and Bmp signalling.
Development 127: 1337-1348.
Wedel, MJ, Cifelli, RL & Sanders, RK. 2000. Osteology,
paleobiology, and relationships of the sauropod dinosaur
Sauroposeidon. ACTA PALAEONTOLOGICA POLONICA. 45 (4) : 343-
Sauroposeidon proteles is a large brachiosaurid sauropod
recently described from the Antlers Formation (Aptian-
Albian) of southeastern Oklahoma. Sauroposeidon represents
the culmination of brachiosaurid trends toward lengthening
and lightening the neck, and its cervical vertebrae are
characterized by extensive pneumatic structures. The
elaboration of vertebral air sacs during sauropod
evolution produced a variety of internal structure types.
We propose a new classification system for this array of
vertebral characters, using computed tomography (CT) of
pneumatic internal structures. Comparisons with birds
suggest that the vertebrae of sauropods were pneumatized
by a complex system of air sacs in the thorax and abdomen.
The presence of a thoraco-abdominal air sac system in
sauropods would dramatically affect current estimates of
mass, food intake, and respiratory requirements.
Sauroposeidon was one of the last sauropods in the Early
Cretaceous of North America; sauropods disappeared from
the continent by the early Cenomanian. The demise of
sauropods in the Early Cretaceous of North America
predates significant radiations of angiosperms, so the
decline and extinction of this dinosaur group cannot be
linked to changes in flora.
This Dec. 19 article was posted by the Dallas Morning News
( http://www.dallasnews.com/ )
Experts try to see whether dinosaur's big eyes provided an
advantage in low light of Arctic
By Alexandra Witze
DALLAS. A particular type of dinosaur thrived in northern
Alaska 70 million years ago because its huge eyes allowed
it to see in dim Arctic light, a Dallas paleontologist has
Alaska's North Slope is littered with fossilized teeth
from the dinosaur Troodon, says Anthony Fiorillo of the
Dallas Museum of Natural History. Elsewhere in North
America, Troodon fossils are extraordinarily rare. But at
certain places in the Arctic, they far outnumber fossils
of other dinosaur species.
So Troodon must have enjoyed some evolutionary advantage,
Fiorillo says. And the eyes had it, he proposes in a
paper, written with University of Alaska paleontologist
Roland Gangloff, in the current issue of the Journal of
According to their theory, Troodon evolved giant eyes
while living at lower latitudes _ all the better to see
prey during dusk or nighttime, perhaps. As the dinosaurs
spread across the continent, Fiorillo says, they became
naturally well-adapted to living in Arctic gloom.
"When they hit the high latitudes, this was an advantage,"
An average Troodon skull displays an eye socket 2 inches
across, compared with less than 1[ inches for the similar-
sized dinosaur Dromaeosaurus, he notes.
Other paleontologists called the idea intriguing, though
hard to prove.
"It's a reasonable hypothesis," says David Varricchio, a
Troodon expert at the Museum of the Rockies in Bozeman,
Mont. "Certainly there's nothing to say that it's wrong at
Troodon is "a kind of weird dinosaur," he adds. It
measured about as long as an adult man is tall, and its
brain case and eye sockets were unusually large for its
size. If brain size correlates with intelligence, as some
scientists believe, then Troodon could have been the
smartest known dinosaur.
It was also the coyote of its time, Varricchio says: a
shrewd, agile predator that ate small mammals and possibly
even plants, consuming whatever it could find.
Still, scientists know very little about Troodon because
so few fossils of it exist. Dig into dinosaur-rich rocks
in Montana and Alberta, and you might find one or two
Troodon teeth after checking 40 sites, says Varricchio.
But just one Alaska site, along the banks of the Colville
River, contains 42 Troodon teeth, says Fiorillo. The
fossils were uncovered during several University of Alaska-
led expeditions starting in the late 1980s; Fiorillo and
Gangloff have been working the sites for the past three
Paleontologist Michael Ryan has also found unusual numbers
of Troodon teeth at a site in south central Alberta. In a
recent paper in the journal GAIA, he suggests that Troodon
lived there in great numbers because there were also large
groups of young hadrosaur dinosaurs, which Troodon preyed
But Fiorillo doesn't think that explanation holds for
Arctic dinosaurs. Troodon might have enjoyed munching baby
hadrosaurs, but they weren't the mainstay of its diet.
Fiorillo suggests that Troodon lived on the North Slope
year-round, rather than migrating with the seasons as some
scientists have suggested. During summers, the light-
sensitive dinosaurs might have coped with the glare of the
midnight sun by living under the forest canopy.
Thomas Rich and Patricia Vickers-Rich, paleontologists in
Australia, also think that polar dinosaurs might have
special adaptations for living in low-light conditions.
Their work on Leaellynasaura amicagraphica, a small
Australian dinosaur that lived near the South Pole, shows
that it sported enlarged eyes as well as enlarged optic
lobes in its brain. The big optic lobes might have allowed
the dinosaur to better process weak nerve signals coming
from its eyes in dim lighting conditions, says Rich, of
the Museum Victoria.
Life in the Arctic would have been relatively pleasant 70
million years ago, Fiorillo says. At the time, the
Colville River area was a low-lying coastal plain, much
like the modern Gulf of Mexico coast; and temperatures
were notably warmer than they are today.
Nevertheless, he adds, "it's still not what you'd think of
as good reptile weather."
(c) 2000, The Dallas Morning News.