Founding Fathers Of Dino Age?

Fossils from two calf-sized animals that lived in a period before the Jurassic are thought to be the oldest dinosaur remains ever found and may be from a group that helped found the age of the dinosaurs, researchers say.

A team from four different institutions uncovered the fossils in an ancient riverbed in Madagascar and found that they were mixed with the remains of animals known by earlier studies to have lived 227 million years ago.

Andre Wyss of the University of California, Santa Barbara, cofounder of the research team, said the fossils are "probably the earliest dinosaurs known from anywhere in the world."

Dating of the fossils is based on the nearby discovery of bones from primitive forms of other animals, including a mammal-like reptile, that are known to have lived just before the age of dinosaurs. An earlier dinosaur find in Argentina included more advanced forms of these mammal-like reptiles and has been age-dated using radioisotopes at 227 million years, Wyss said.

"We know we are earlier than 227 million years, and these animals could be as much as five million years older," he said.

The new specimens consist of the upper and lower jawbones of two dinosaur species never before seen, said Wyss. Based on the teeth and the characteristics of the jaw, the researchers believe the animals are prosauropods, primitive plant-eaters with small heads and long necks. The apatosaurus, a 36-ton monster that was largest animal ever to walk the Earth, is thought to have descended over millions of years from the prosauropods.

"That was the animal that Fred Flintstone rode," Wyss joked.

Wyss said the fossils come from an immense collection that is still being analyzed or dug out of quarries in Madagascar. The researchers are not naming the new animal species until more is known about them, he said.

Neil Shubin, a dinosaur researcher at the University of Pennsylvania, said that experts might argue about the age of the new specimens because it has not been established by the accurate radioisotope method.

"Whether you want to call this the earliest dinosaur or one of the earliest dinosaurs depends upon your interpretation," he said.

But whatever the case, said Shubin, "this is really an important find" because it sheds new light on a critical stage in evolution when dinosaurs were dividing into the meat-eaters and the plant-eaters, divisions that were maintained for the 160-million-year reign of the dinosaur.

"This suggests that very early in the evolution of dinosaurs, these two major groups were already appearing," Shubin said.

A report on the fossil find appears Friday in the journal Science. In addition to Andre Wyss, the authors are John J. Flynn of the Field Museum in Chicago; J. Michael Parrish of Northern Illinois University; Berthe Rakotosamimanana of the Universite d'Antananarivo in Madagascar, and Robin L. Whatley of th University of California, Santa Barbara.