January 13, 2011. Copyright 2011, Graphic News. All rights reserved

Early ancestor of T-rex discovered in Argentina

LONDON, January 13, Graphic News: Researchers probing ancient ravines and ridges in Argentina’s arid Ischigualasto Park have discovered a previously unknown dinosaur, a find which challenges current theories of the opportunistic ascendancy of the species.

Eodramaeus murphi lived during the dawn of the dinosaur era, about 230 million years ago. Weighing only 4.5-6.8kg (10-15 pounds) and about 1.2 metres (4 feet) in length from snout to tail tip, pint-sized Eodromaeus, or “dawn runner”, is an early ancestor of the theropod dinosaurs, which included all meat-eating dinosaurs such as Tyrannosaurus rex.

Ricardo Martinez of Universidad Nacional de San Juan, Argentina, and his colleagues suggest that features in its skull -- such as an opening near the end of the snout called the promaxillary fenestra -- as well as the structure of its pelvic girdle and hind limbs, confirm the theropod lineage.

With a scaled face for protection, sabre-shaped upper teeth for snatching prey, and draped neck skin for swallowing large prey, Eodromaeus was a predator of small animals and the young of larger animals.

During the late Triassic era, the Pangaea super-continent was dominated by plant eaters. Around eight in 10 land animals were herbivores, including cynodonts (early proto-mammals), and rhynchosaurs, reptile-ancestors of today’s crocodiles, lizards, and snakes.

The research, published in the January 14 issue of Science, concludes that dinosaurs represented about 11 percent of all vertebrate animals during the late Triassic period -- many more than previously thought. This runs counter to the theory that the ascendancy of the dinosaurs was opportunistic, simply taking advantage of vacant ecological niches as other species became extinct.

The fossil record from Ischigualasto indicates that early dinosaurs were not only more common and diverse, but appeared in southern Pangaea (modern Argentina and Brazil) some 15 million years earlier than in northern Pangaea (western North America). This suggests that the ascendancy of the dinosaurs may have originated in southern Pangaea, and spread globally, before the component continents were separated into their current positions.
/ENDS