New Dino Papers and News

[bh480@scn.org]

From: Ben Creisler bh480@scn.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-
388
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 
suggested. 

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 
Vertebrate Paleontology. 

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," 
he says. 

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 
this point." 

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 
summers. 

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 
on. 

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.