In this life restoration, the adult is shown as a mother, protecting her baby from a predator by using those powerful thigh muscles to deliver a devastating kick.
Credit: Francisco Gascó
SYDNEY: Fossils have been found of a new dinosaur that not only had unusually large hip bones, but was likely to have had the largest leg muscles of any known member of the sauropod family, new research suggests.
Named Brontomerus mcintoshi, or ‘thunder-thighs’ after its enormously powerful thigh muscles, the dinosaur is, “part of a flood of new sauropod dinosaurs coming out of the Early Cretaceous of North America – a period that was originally thought to be devoid of sauropods”, said co-author Mathew Wedel, assistant professor of anatomy at Western University of Health Sciences in California.
“What it points out is that sauropods were globally successful for almost the entire Age of Dinosaurs,” said Wedel. “Very early in their evolution they committed to being big, and that just never stopped working for them.”
Used for kicking the raptors away
During the Early Cretaceous Period 110 million years ago, Brontomerus - a member of the long-necked sauropod group which includes Diplodocus and Brachiosaurus - probably had to contend with fierce ‘raptors’ such as Deinonychus and Utahraptor, so may have used its powerful thighs as a weapon to kick predators, or to help travel over rough, hilly terrain.
“When we recognised the weird shape of the hip, we wondered what its significance might be, but we concluded that kicking was the most likely,” said first author Mike Taylor, a researcher in the Department of Earth Sciences at University College London.
“The kick would probably have been used when two males fought over a female, but given that the mechanics were all in place it would be bizarre if it wasn't also used in predator defense.”
Specimens found of mother and offspring
The fossilised bones of two specimens of Brontomerus mcintoshi – an adult and a juvenile – were rescued from a previously looted and damaged quarry in eastern Utah by researchers from the Sam Noble Museum in Oklahoma.
The team suggest that the larger specimen could be the mother of the younger and would have weighed around 6 tonnes - about the size of a large elephant - and measured 14 m in length, the team naming it in honour of John ‘Jack’ McIntosh, a retired physicist at Wesleyan University, Connecticut, and lifelong avocational palaeontologist.
At a third of the size, the smaller specimen would have weighed about 200 kg - the size of a pony - and been 4.5 m long, according to the paper recently published in the journal Acta Palaeontologica Polonica.
