[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Giant Dinosaur Fossil Forces Scientists to Question Theories



Giant Dinosaur Fossil Forces Scientists to Question Theories 

     Peter Spotts, Staff writer of The Christian Science Monitor 

     BOSTON -- The barren hills of northwestern Patagonia in Argentina 
have yielded fossil remains of the largest raptor-like dinosaur ever 
discovered.

     Nearly four times longer and eight times heavier than the voracious 
velociraptors of "Jurassic Park," the 90-million-year-old creature is 
challenging notions of how raptors may have behaved and how widely they 
were distributed. It also represents the latest in a string of South 
American fossil finds that are yielding clues to issues ranging from the 
evolution of birds to the splitting of continents.

     The discovery was announced Dec. 2 at Houston's Museum of Natural 
History, where Argentine paleontologist Fernando Novas unveiled a cast 
of the raptor's 13-inch toe claw. So far, the claw, a leg bone, and two 
arm bones have been unearthed. Dr. Novas named the creature Megaraptor 
namunhuaiquii, loosely translated as "large thief with lance feet."

     The moniker "thief" may be a bit tame. Megaraptor, Novas says, is a 
very distant relative of a group of meat-eating predators, including 
Tyrannosaurus rex. 

     Most raptors typically stood about as high as a human, says Peter 
Dodson, a professor of veterinary anatomy and geology at the University 
of Pennsylvania in Philadelphia. From tail to nose, they averaged 8 to 9 
feet long and tipped the scales at between 150 and 185 pounds, while at 
least one species, Utahraptor, reached lengths of 16 feet.

     Megaraptor, by contrast, is 25 to 30 feet long and probably stood 
13 feet tall.

     "We've tended to view raptors as small, swift, vicious, and cunning 
hunters rather than brutal and strong," Dr. Dodson says, "Now, our 
confidence in that picture is being shattered a bit."

     Megaraptor's home turf also comes as a surprise.

     "This is the first record from South America of this group of 
dinosaurs," says Hans-Dieter Sues, a paleontologist at the Royal Ontario 
Museum in Toronto. "Previously, we thought they only lived in the 
Northern Hemisphere."

     He explains that smaller raptors were widely distributed in 
Laurasia - what was to become North America and Asia. But Gondwanaland, 
which would later split into Africa and South America, was isolated from 
Laurasia.

     One possible explanation for raptors' appearance in South America, 
he says, is that a land bridge or archipelago could have existed at the 
time, allowing raptor-like creatures to migrate south. The Caribbean is 
so geologically active that any evidence of such a bridge is likely to 
have been destroyed.

     The more likely explanation, he says, holds that Megaraptors and 
their northern counterparts evolved separately from common ancestors 
that had a worldwide distribution. Once the earth's land mass began to 
break apart, dinosaurs evolved into what Dr. Sues terms "more 
provincial" species.

     Whatever the explanation, is it clear that South America represents 
a unique natural museum, and did even in the days of the dinosaurs 
themselves. 

     "Most South American dinosaur fauna are oversized forms," says 
Rodolfo Coria, another Argentine paleontologist who uncovered 
Giganotosaurus, the largest-ever flesh eater. "They represent primitive 
assemblages of dinosaurs that were widely distributed around the world 
during the Jurassic period, but survived another 50 million years into 
the Cretaceous period in South America. This was their last bastion 
before they became extinct."

     Dinosaurs such as Megaraptor and Giganotosaurus, which stood high 
above their northern counterparts, also may represent the limit on size 
for predators that walk on their hind legs. "Physiology is the limiting 
factor," says Dodson.  "There may be other discoveries in their size 
range, but not 50 percent larger."

     I got this of of Christian Science Monitor's website.  This is 
another article that describes Megaraptor.

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com