October 6, 2010

Fossil Find Suggests Cat-Sized Dinosaur Ancestors

Footprints described by scientists in a new report suggest that the earliest species of dinosaurs are not only older than previously believed, but much smaller as well.

Researchers have dated the fossilized tracks back to approximately 250 million years ago, or at least five million years earlier than any previously discovered dinosaur remains had indicated. Furthermore, they have tied the footprints to a creature that walked on all four legs and about the size of a common house cat, according to a paper printed this week in the journal Proceedings of the Royal Society B.

The footprints were discovered at three sites in central Poland's Holy Cross Mountains by a team of investigators led by Grzegorz NiedÃ…ºwiedzki of the University of Warsaw and the Polish Academy of Sciences.

The smaller dinosaurs, which were described by AFP as "the forerunners of triceratops and brontosaurus," likely only became the dominant species because of their ability to survive the Permian-Triassic extinction, dubbed "the worst mass extinction in the history of the planet" by BBC News Science Correspondent Paleb Ghosh.

"We see the closest dinosaur cousins immediately after the worst mass extinction. The biggest crisis in the history of life also created one of the greatest opportunities in the history of life by emptying the landscape and making it possible for dinosaurs to evolve," Stephen Brusatte, a paleontologist from the American Museum of Natural History and a participant in the project, said in a statement Tuesday.

"For the first 20 million years of dinosaur history, dinosaurs and their closest relatives were living in the shadow of their much more diverse, successful, and abundant crocodile-like cousins," Bursatte, the lead author of the paper, added. Furthermore, he also told BBC News that his team's findings would lead to "a very radical re-interpretation of the early history of dinosaurs."


Image 1: This is a reconstruction of cat-sized stem dinosaur Prorotodactylus isp. found in Stryczowice, Poland that was a quadruped with a dinosaur-like gait and orientation of the toes. Credit: Grzegorz NiedÃ…ºwiedzki

Image 2: The 246 million year old footprints of Sphingopus isp. from the Early Anisian of Baran³w, Poland are associated with a trackway that is even more dinosaur-like in that the gait was bipedal. These tracks are the oldest record of a large-bodied (track length 15 cm) and bipedal member of the dinosaur lineage. Credit: Grzegorz NiedÃ…ºwiedzki


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