It turns out that T. rex wasn’t the only dinosaur with ridiculously tiny arms.
Another dinosaur, not closely related to T. rex, evolved a similar body form with the characteristic teensy arms.
Named Gualicho shinyae, this dinosaur is estimated to have been approximately the size of a polar bear, but with arms the size of a human child. Like T. rex, this dinosaur had just two “fingers” on each hand, possibly for grasping prey.
T. rex was much larger than Gualicho, however — about the size of a bus — and lived in North America while Gualicho is thought to have lived in Africa.
Scientists are still trying to determine why two completely different species may have evolved these inexplicably small arms. They could have been used for holding on to prey, for mating rituals, or perhaps the animals relied on their legs so much that their arms became obsolete.
The jury is still out.
Peter Majovicky of The Field Museum stated about this new discovery, “Gualicho is kind of a mosaic dinosaur, it has features that you normally see in different kinds of theropods.” He went on, “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.”
The fossil was first found in Patagonia in 2007 and is named after the Patagonian spirits of mischief and devilment, Shinya and Gualicho.