A "mini" Tyrannosaurus rex looking almost identical to the most famed of dinosaurs, but many times smaller (and with even weedier arms), has been unearthed in China.
The small predator, named Raptorex kriegsteini, measured 3 metres from head to toe and weighed about 10 stone, the same as an average human. It lived 125 million years ago, predating T-Rex by around 60 million years.
The two carnivores shared the same body plan, having a large skull, tiny forearms and athletic hind legs designed for running. But T-Rex measured 12.4 metres, stood 15 to 20 feet high, and weighed between five and seven tons.
The species discovery suggests that the T-Rex's specialised physical features did not evolve as meat-eating therapod dinosaurs grew in size – as most experts believe. Instead they seem to have been present throughout the Cretaceous period in which the tyrannosaurs, which included T-Rex, topped the food chain.
The almost complete Raptorex skeleton (skull, teeth, nose, spine, shoulders, forearms, pelvis and hind legs) was removed illicitly from an area of fossil-bearing rocks called the Yixian Formation in Inner Mongolia, north-eastern China. The bones were bought by a private collector, Henry Kliegstein, who turned them over to US scientists at the University of Chicago. Their importance was revealed when it became clear that this was an adult dinosaur bearing all the hallmarks of later giant tyrannosaurs but at a fraction of the size.
Stephen Brusatte, from the American Museum of Natural History in New York, who worked on the finds, said: "Much of what we thought we knew about tyrannosaur evolution turns out to be simplistic or out and out wrong."