October 24, 2008

Dino Skull Has Both Meat And Plant Eating Traits

The skull of a young dinosaur that lived 190 million years ago is revealing new clues as to how some carnivorous dinosaurs evolved into plant eaters.

The tooth structure of the young Heterodontosaurus reveals both sharp fang-like canine teeth for biting and tearing, as well as flat molar-like teeth designed for grinding.

"This juvenile skull indicates that these dinosaurs were still in the midst of that transition," said Laura Porro, a post-doctoral student at the University of Chicago, who described the skull in the Journal of Vertebrate Paleontology.

Porro discovered the skull in a drawer in the Iziko South African Museum in Cape Town, South Africa. She was studying the eating habits of adults of this type of dinosaur at the time.

Porro said paleontologists had thought the canines were sexually dimorphic -- a characteristic present only in adults of one gender in a species like antlers in male deer.

However, the presence of long, serrated canines in the juvenile suggest they were common to both genders, Porro said.

"They have these really long canine teeth, which don't look like the teeth of a plant eater," said Porro, who worked with scientists from the Natural History Museum in London.

"They almost look like little saber-toothed tiger teeth."

During the time of Heterodontosaurus other plant-eating dinosaurs included the long-necked sauropods. But this creature was one of the earliest of the ornithischians that soon become very important in the Age of Dinosaurs.

While adult Heterodontosaurus were turkey-sized creatures that reached just over three feet (1 meter) in length and weighed about five pounds (2.5 kg), the juvenile likely weighed less than half a pound (200 grams) and would have been just about a foot and a half long.

Porro said the eyes in the juvenile skull are much bigger, and the nose is much shorter.

"It's the same things that makes puppies and kittens appealing," she said. "I think it's adorable."


Image Caption: Cast of the type specimen of Heterodontosaurus tucki from South Africa, as displayed in the Valley Life Sciences Building of the University of California, Berkeley.


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