A new dinosaur species has been discovered in Utah, America.
The beast has been named Brontomerus mcintoshi or "Thunder-Thighs" by scientists because of the huge thigh muscles it had, probably used for kicking during fights over a mate or to ward off predators, they believe.
It is thought that it was a member of the long-necked sauropod group of dinosaurs, which includes Diplodocus and Brachiosaurus which lived about 110 million years ago.
The fossilised bones of two specimens, an adult and a juvenile, were rescued from a previously looted and damaged quarry in eastern Utah by researchers.
The animal is thought to have had the largest leg muscles of any dinosaur in the sauropod family.
