Dinosaur Found - in Museum

South African scientists have discovered the oldest known example of a sauropod - one of the giant plant-eaters of the Jurassic era - in a museum.

Antetonitrus ingenipes, two metres high at the hip and probably weighing two tonnes, stalked the planet 215m years ago.

The fossil remains, unearthed in 1981, were originally wrongly classified.

Adam Yates of the University of Witwaterstrand reports in the Proceedings of the Royal Society that in fact the creature belonged to a species entirely new to science, and was so far the earliest known ancestor of the dinosaurs known to all schoolchildren: Diplodocus and Brachiosaurus.

He noticed the forgotten fossil when he was a research student at the museum and saw what he thought were sauropod characteristics in its backbone. "I was so lucky that no one had moved on this specimen before," he said.

Antetonitrus was small for a sauropod. One of its descendants was Argentinosaurus, probably the heaviest land animal of all time, weighing 100 tonnes.

Until the discovery, the earliest candidate for sauropod ancestry was Isanosaurus, which roamed the forests of what is now Thailand 210m years ago.

The latest find walked on four legs but, unlike later sauropods, had a grasping hand.

Dr Yates added: "Antetonitrus is not a giant but it gives us some clues as to the evolution of gigantism."