Dipping in. The skull of Thalassodromeus suggests it skimmed for fish, while its crest kept it cool.

Cool-Headed Pterosaurs Go Fishing

The crests that swoop backward from the skulls of pterosaurs have long intrigued paleontologists. Now a specimen described in the 19 July issue of Science suggests that the crests helped the large fliers keep cool. It also reveals how the creature hunted. "This is really a spectacular animal," says Dave Unwin, a pterosaur specialist at the Museum of Natural History of Humboldt University in Berlin.

Functions proposed for pterosaur crests include sexual display and help in steering during flight. The new evidence for temperature regulation comes from a 1.4-meter-long skull discovered in the Santana Formation of Northeastern Brazil, a layer of rocks that has yielded many pterosaurs. When they examined the fossil, paleontologists Alexander Kellner of the Federal University of Rio de Janeiro and Diogenes de Almeida Campos of the National Department of Mineral Production in Rio de Janeiro discovered imprints of blood vessels on the crest. Blood coursing though these vessels could have released heat, they argue. "For the first time we have direct evidence that some pterosaurs could have used their crest to control their body temperature," says Kellner.

The skull also has clues to the eating habits of the pterosaur, named Thalassodromeus for "sea runner." The lower jaw tapers to a long blade, and the back half of the upper jaw sports a sharp blade too. The only other known animal with a similar scissorslike arrangement is a seabird called Rynchops, which skims over water and plucks out fish with its lower jaw.

The massive crest impresses pterosaur expert Peter Wellnhofer of the Bavarian State Museum for Paleontology in Munich. But he wonders whether such a large pterosaur would have been able to skim. "Flapping its wings just above the water surface when skimming could have been a problem." And although Wellnhofer is convinced by the argument that the crest was used for heat exchange, Unwin thinks the fact that the blood vessels run toward the top of the crest--rather than forming a netlike pattern--suggest they might have supplied blood to a flesh at the top of the crest. He also points out that in any case, the crest was probably not critical, because not all pterosaurs have them.

Related sites
Introduction to the Pterosauria
Alexander Kellner's site (in Portuguese)
Dave Unwin's site

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