Nature did not make a mistake by giving Tyrannosaurus rex an absurdly small pair of forelimbs, new research suggests.
The tiny two-fingered claws rather spoil the image of the most fearsome and famous predator ever to walk the earth, and have long been a puzzle to scientists.
Now the same odd body design has been discovered in another carnivorous dinosaur from South America that evolved completely independently of T. rex.
Gualicho shinyae, a medium sized two-legged theropod dinosaur weighing about 1,000lb (454kg), had forelimbs about the size of a human child’s.
And like T. rex, its hands had just two digits, a thumb and forefinger.
The similarity between the two dinosaurs is an example of convergent evolution – the development of identical traits in unrelated species due to natural selection.
It suggests that puny forelimbs on a savage meat-eating dinosaur were not a joke. Nature knew what she was doing – but scientists are still none the wiser.
“By learning more about how reduced forelimbs evolved, we may be able to figure out why they evolved,” said lead researcher Dr Peter Makovicky, from The Field Museum in Chicago, US.
An incomplete Gualicho skeleton was discovered in 2007 during an expedition to a fossil-rich site in northern Patagonia.
The dinosaur is described in the online journal Public Library of Science ONE.
Dr Makovicky said: “It’s really unusual – it’s different from the other carnivorous dinosaurs found in the same rock formation, and it doesn’t fit neatly into any category.”
Gualicho appears to be most closely related to Deltadromeus, a leggy carnivorous dinosaur with slender arms from Africa.