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U. CHICAGO (US)—A new species of parrot-beaked dinosaur offers the first solid evidence of nut-eating in any dinosaur based on an analysis of its skull characteristics and gizzard stones.

Discovered in the Gobi Desert of Inner Mongolia in 2001, the nut-cracking dinosaur is approximately 110 million years old, dating to the mid-Cretaceous period.

The skull of Psittacosaurus gobiensis closely resembles the skull of modern-day parrots, says Paul Sereno, a paleontologist at the University of Chicago and National Geographic Explorer-in-Residence.

“The parallels in the skull to that in parrots, the descendants of dinosaurs most famous for their nut-cracking habits, is remarkable,” Sereno says. The discovery from Sereno and two colleagues from the People’s Republic of China appears June 17 in the Proceedings of the Royal Society B.

“The psittacosaur at hand has a huge pile of stomach stones, more than 50, to grind away at whatever it eats, and this is totally out of proportion to its three-foot body length,” Sereno explains. In birds, the quantity and size of gizzard stones correlates with dietary preference—the larger the stone, the harder the diet.

The way the dinosaur chewed its food is also significant, Sereno explains, because it displays a whole new way of chewing, which Sereno and coauthors have dubbed “inclined-angle” chewing.

“The jaws are drawn backward and upward instead of just closing or moving fore and aft,” Sereno says. “It remains to be seen whether some other plant-eating dinosaurs or other reptiles had the same mechanism.”

The unusual chewing style has solved a major mystery regarding the wear patterns on psittacosaur teeth. Psittacosaurs sported rigid skulls, but their teeth show the same sliding wear patterns as plant-eating dinosaurs with flexible skulls.

The research is supported by the National Geographic Society, David and Lucile Packard Foundation, Biological Sciences Division of the University of Chicago, and Long Hao Institute of Stratigraphic Paleontology.

University of Chicago news: http://news.uchicago.edu