Missing link ties older to newer dinosaurs

Thursday, April 14, 2011

The surprising discovery of a fossil of asharp-toothed beast that lurked in what is now the western U.S.more than 200 million years ago is filling a gap in dinosaurevolution.

The short snout and slanting front teeth of the find -Daemonosaurus chauliodus - had never before been seen in a Triassicera dinosaur, said Hans-Dieter Sues of the Smithsonian's NationalMuseum of Natural History. Sues and colleagues report the discoveryin Wednesday's edition of the British journal Proceedings of theRoyal Society B.

Sues, curator of vertebrate paleontology at the museum, said thediscovery helps fill the evolutionary gap between the dinosaursthat lived in what is now Argentina and Brazil about 230 millionyears ago and the later theropods like the famous Tyrannosaurusrex.

Features of the skull and neck of Daemonosaurus indicate it wasintermediate between the earliest known predatory dinosaurs fromSouth America and more advanced theropods," said Sues. "One suchfeature is the presence of cavities on some of the neck vertebraerelated to the structure of the respiratory system."

Daemonosaurus was discovered at Ghost Ranch, N.M., a well-knownfossil site famous for the thousands of fossilized skeletons foundthere, notably the small dinosaur Coelophysis. Ghost Ranch was morerecently the home of artist Georgia O'Keeffe, who was known tovisit the archaeological digs under way there, Sues noted.

Having found only the head and neck of sharp-toothedDaemonosaurus, the researchers aren't sure of its exact size butthey speculate it would have been near that of a tall dog. Its nameis from the Greek words "daimon" meaning evil spirit and"sauros" meaning lizard or reptile. Chauliodus is derived fromthe Greek word for "buck-toothed" and refers to the species' bigslanted front teeth.

"It looks to be a mean character," commented paleontologistPaul Sereno of the University of Chicago, who was not part of theresearch team. "I can't wait to see if they get any more of theskeleton."

This fits in quite nicely between the dinosaur groups, Serenosaid, even though its face is unlike anything that would have beenexpected in these early dinosaurs, which tended to have moreelongated snouts.

For more information related to dinosaurs, visit rareresource.com.


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