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A 24-tonne dinosaur appears to have stood on its tip toes. A fossil analysis reveals how its bone structure meant it couldn鈥檛 have flattened its feet on the ground, and instead may have stood on its toes with fleshy pads for balance.

Rhoetosaurus brownei聽lived around 170 million years ago and was a type of sauropod dinosaur. Sauropods walked on all fours and had long necks and tails. They were the largest land animals ever known to exist and the group includes Diplodocus.

Andr茅as Jannel at the University of Queensland in Australia and his colleagues analysed a foot fossil of R. brownei聽to see how it could have supported itself.

They found its bone structure meant its heels couldn鈥檛 touch the ground without breaking its ankles. This means that despite being so enormous, R. brownei聽may have walked on its tiptoes.

Footprints of sauropods that lived a few million years later have suggested these giants had feet that resemble modern elephants. Elephants stand on their toes and have a thick layer of soft tissue that touches the ground.

R. brownei聽was five times the size of an elephant, so may have needed similar soft padding to support its humongous body and give it balance, says Jannel.

However, there is no direct fossil evidence of such a heel pad on R. brownei聽or other sauropods because soft tissue is rarely preserved.

Sauropods underwent rapid body growth from their ancestors. As a result, not all parts of their bodies were prepared for such an expansion, says Denver Fowler at the Dickinson Museum Center in North Dakota.

To adapt, sauropods had to evolve new weight support systems, and heel pads would have been very useful, he says.