World's earliest dinosaur found in 'valley of unknown species'

Remains of the oldest dinosaur in the world have been unearthed at a fossil site on Madagascar in a find that may explain the origin of the biggest creatures ever to walk the Earth.

Remains of the oldest dinosaur in the world have been unearthed at a fossil site on Madagascar in a find that may explain the origin of the biggest creatures ever to walk the Earth.

Palaeontologists were led by a Malagasy youth called Mena from a remote village on the island to the fossil collection, which the scientists describe as "spectacular" in research published today in the journal Science.

The fossils - named Mena, in honour of their discoverer - date from the middle to late Triassic period, between 225 and 230 million years ago. They are believed to be older than the 228 million years of the current record-holders, herrerasaurus and eoraptor.

The team's leader, John Flynn, a palaeontologist at the Field Museum, in Chicago, said many of the fossilised species found at the site were new to science. "They are exquisitely preserved. They show a level of detail far superior to everything else from that time," he said.

Andrew Wyss, a fellow investigator and associate professor of geology at the University of California, Santa Barbara, recounted the surprise find. "A boy said that his older brother had found some bones. So we waited around a half-day for the brother, Mena, and sure enough he showed us a hill with a mound of them."

The group has so far unearthed the jawbones of two dinosaurs, which have revealed that the creatures belonged to a group known as the prosauropods, herbivores with small heads and long necks that could walk on either two or four legs. The prosauropods are believed to have been the ancestors - or closely related to the ancestors - of the mighty sauropods such as apatosaurus and diplodocus, which evolved millions of years later.

The fossils also contain a rich collection of bones belonging to three members of a branch of vertebrate animals that includes modern-day reptiles and five members of a line that led to mammals.

The scientists have not yet carried out any radioisotope dating but they have two reasons to believe that the dinosaur is over 228 million years old. First, the anatomical details of two of the accompanying fossils suggest that they are older than creatures known to have existed 228 million years ago. Second, an armoured reptile called the aetosaur, abundant 228 million years ago, is conspicuously absent from the Mena fossils.

Dr Flynn said the find may even help to explain how the break-up of the ancient supercontinent Pangaea, which began in the Triassic period, affected the course of evolution.