Gualicho shinyae was unveiled in Argentina, a new species of dinosaur whose stunted arms resemble those of the Tyrannosaurus rex, according to The Washington Post. Although the animal was as big as a polar bear, its arms were human child–sized. As the study in PLOS ONE details, the new species is of unique lineage—only a distant cousin of the T. rex. In fact, their last common ancestor had arms of proportionate size to its body. Because the two separate lineages evolved the same trait independent from one another—a phenomenon known as convergent evolution—there is evidence to suggest having tiny arms would have been considerably beneficial. Researchers propose that comically small arms would have allowed the dinosaurs to hunt with their jaws in a more accurate and energy-efficient way.