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New Find: Pterosaur Had Strange Crest, Fishing Style

Lara Suziedelis Bogle
for National Geographic News
July 18, 2002
 
The 4.7-foot (1.42-meter) skull of a giant flying reptile that lived among dinosaurs suggests that it might have hunted for food like modern birds known as skimmers, using its scissors-like bill to snatch prey as it glided over water.

Thalassodromeus sethi, a previously undescribed pterosaur which lived in the Araripe Basin of northeastern Brazil 110 million years ago, had a wingspan of as much as 15 feet (4.5 meters), according to scientists Alexander W. A. Kellner and Diogenes de Almedia Campos at Museu Nacional/Universidade Federal do Rio de Janeiro and at Museu de Ciências da Terra in Rio de Janeiro.

The pterosaur also had a large but thin bony crest. With the exception of one other species, T. sethi "has the proportionally largest crest known in any vertebrate, fossil or recent," the researchers report in the July 19 issue of Science.



Although scientists have been studying pterosaurs for over 200 years, a comprehensive understanding of their diversity and biology has been elusive due to the fragile nature of pterosaur fossils. Brazil's Araripe Basin is one of the few deposits where pterosaurs are found in large numbers with good preservation.

The fossil described in Science is rare in that the skull, from the early Cretaceous period, is almost completely intact. This allowed the researchers to perform a thorough analysis, gaining a better insight into T. sethi's feeding behavior, and into the function of cranial crests in pterosaurs.

The researchers speculate that T. sethi's crest may have served several purposes.

Grooves in the crest's bone show that it was densely packed with blood vessels, evidence that its primary function was probably to regulate its blood temperature, the scientists said. T. sethi might have been able to cool itself by circulating blood through the crest, dissipating excess body heat through convection.

It may also be that the crests' distinctive shapes and color patterns enabled the pterosaur to recognize kin or differentiate between the sexes.

Finally, the large size of the crest may indicate that it played a part in aerodynamics.

Carefully modulated flight would have been critical to T. sethi's survival. By comparing it to modern birds of the genus Rynchops (commonly called skimmers), Kellner and Campos concluded that T. sethi also fed by skimming across bodies of water and dipping its blade-like lower jaw into the water to scoop up its prey.

Its distinctive elongated skull and specialized jaws are almost certain evidence that T. sethi caught its prey using this method, the researchers said.

Unlike skimmers and other modern birds, however, T. sethi's massive crest and less flexible neck would have prevented it from submerging its entire head when skimming, limiting its food supply to the animals at the very surface of the water.

But because of its large wingspan, T. sethi would have been able to glide over longer distances and flap its wings less frequently than modern birds, the scientists suggested. This would have allowed it to stay close to the surface of the water for longer periods of time.

Kellner and de Almedia Campos Campos are also at the American Museum of Natural History in New York.

Recent National Geographic News stories on dinosaurs:
Fossil of Dog-Size Horned Dinosaur Unearthed in China
Tyrannosaurus rex Was a Slowpoke
Researchers Rethink Dinosaur Die Off Scenario
Researchers Melt Polar Dinosaur Mysteries
Scientist's Finds Spur New Thinking on Dino Evolution
Dino-Era Vomit Fossil Found in England
Study Paints New Picture of Dinosaur's Nose
Skeleton of New Dinosaur "Titan" Found in Madagascar
"Tidal Giant" Roamed Coastal Swamps of Ancient Africa
"Feathered" Fossil Bolsters Changing Image of Dinosaurs
Oddly Angled Teeth Make Masiakasaurus Stick Out

Additional dinosaur resources from National Geographic:
Paul Sereno: National Geographic Explorer-in-Residence and Dinosaur Hunter
Dinorama
Wanted: Albertosaurus
Dinosaur Eggs
Destinations: Dinosaur National Monument
 

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