Tiny, Toothy Dino Was No Vegetarian

Oct. 24, 2008 -- The world's second smallest known dinosaur skull belonged to a toothy heterodontosaur whose appetite probably far exceeded the size of its head, suggests a new study that proposes the dino consumed both plants and meat.

Although scientists suspect the dinosaur was mostly vegetarian, its theorized "occasional omnivory" could mean it represents a transitional phase between carnivorous dinosaurs and herbivores.

A tiny skull, which co-author Laura Porro stumbled upon in the archives of Cape Town's Iziko South African Museum, narrowly missed becoming the world's smallest known dinosaur head. It measures less than 2 inches in length and belonged to a juvenile weighing less than two sticks of butter.

"The skull of a baby dinosaur called Mussasaurus, or mouse lizard, from Argentina is smaller, at only 3 centimeters, (and is) probably the world's smallest complete dinosaur skull," Porro told Discovery News.

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Heterodontosaurus lived during the Early Jurassic period around 190 million years ago. Adults grew to about the size of a modern-day turkey, reaching just over 3 feet in length and weighing five to six pounds.

Porro, a University of Chicago paleontologist, and her colleagues studied the juvenile's skull and determined the individual was probably buried alive in a sandstorm, a mode of death that left its remains in "relatively good condition."

The researchers focused on the dinosaur's "bizarre suite of teeth."

"Heterodontosaurus is unusual among dinosaurs -- and all reptiles -- in that its teeth dramatically change shape along the jaw," Porro said.

The front of the jaw is lined with large, fang-like canine teeth exist. These are normally associated with carnivores. But this species also has heavily worn, molar-like grinding teeth at the back. These are more characteristic of plant eaters.