Christine McGourty reports on the new findings

But scientists who have modelled their movements with computers say the animals would have had difficulty lifting their heads and must have grazed along the ground for food instead.

It is thought that it would have been difficult to pump sufficient blood up a long near-vertical neck to the dinosaur's head if it was browsing from tree tops.

Now scientists have made computer models of the neck postures of two dinosaurs - the brontosaurus and the diplodocus.

When they put the virtual dinosaurs through their paces they found the most relaxed posture for the neck was pointing slightly downward and the head was close to the ground.