Tyrannosaurus Rex may have been the king of the dinosaurs with its reputation for being a killing machine, but it is also known for its itty-bitty forelimb. Scientists aren't quite sure why this massive carnivore had such tiny arms, but what they do know now is that it wasn't alone.
A newly discovered dinosaur from Argentina, the Gualicho shinyae, is also a member of the T.Rex's club for having puny-arms. It weighed around a thousand pounds and stood about six feet tall. Its arms were as small as a little kid's.
Though this two-legged creature is also carnivorous (theropods) like T.Rex, they are not directly related. New study suggests that the Gualicho shinyae evolved its stubby arms completely independently.
The new dinosaur belonged to a different type of theropods called the allosaurus, which usually had strong, proportionally sized arms. So far, it is the only member of the group to have feeble arms with two fingers.
Along with the tyrannosaurus, and a second dinosaur group known as the abelisaurus, Gualicho shinyae is one of the few theropods with tiny arms that palaeontologists have found.
According to Peter Makovicky, a paleontologist with the Field Museum in Chicago, the earliest ancestors of tyrannosaurs lived some 165 million years ago and had long arms with three digits. But by the time the creatures made it to the Late Cretaceous period, about 80 million years ago, they lost a finger and their arms became shorter.
Though Gualicho shinyae comes from a different line of dinosaurs, studying its wimpy arms may provide some insight into the evolutionary pressure that might cause a giant like T.Rex to end up with tiny forelimbs.
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