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Fossil Hints at How Pterosaur Hunted

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SCIENCE
The remains of a previously undescribed species of pterosaur are yielding fresh clues to how these distinctive animals hunted for food. According to findings published in the current issue of the journal Science, the fossil represents a beast that may have captured its prey by skimming the surfaces of lakes and oceans. The flying reptile would have been hard to miss, given the huge, bony crest that adorned its head.

Like their dinosaur kin, pterosaurs are now extinct. But scientists have fewer clues to how these animals lived because their bones are very fragile and rarely survive as fossils. Alexander W. A. Kellner of the National Museum and Federal University of Rio de Janeiro and Diogenes de Almeida Campos of the Museum de Ciencias da Terra describe a specimen from the Santana Formation in northeastern Brazil that was collected in 1983 but remained undescribed until now (see image). Christened Thalassodromeus sethi, meaning "sea runner," the creature is estimated to have had a wingspan of nearly 4.5 meters. Its cranial crest, which is proportionally the second-largest known in any vertebrate fossil, probably interfered with the animal's aerodynamics, but it may have helped lure mates. The team also discovered an assemblage of channels of varying sizes on the external surfaces of the crest, which they interpret to be impressions of blood vessels. Such a system could have helped the animal regulate its body temperature by dissipating heat.

The remains of T. sethi's jaw also provide insight into how it hunted. The two halves locked together much like scissors do. This configuration is unique among pterosaurs but is similar to that of birds belonging to the genus Rynchops, commonly called skimmers. A skimmer flies just above lakes and oceans, dragging its lower jaw through the water. When it encounters fish, the upper jaw snaps shut and the head moves down and back, sometimes dipping beneath the surface in the process. Kellner and Campos suggest that T. sethi used a similar strategy for hunting but that it would have had slightly less mobility in its neck and that its crest would have prevented it from fully submerging its head in search of prey.

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