The Tyrannosaurus Rex, for all its fearsomeness, has always been ridiculed a little bit for its teeny tiny arms. But a scientist has recently made the extraordinary claim that in fact, those arms were “vicious weapons,” and not to be mocked.

While the arms may be small and short, they were strong and had large claws that would have allowed the T-rex to mount the back of its victim, slashing huge gashes three feet or longer and several centimeters deep in a matter of seconds, University of Hawaii paleontologist Steven Stanley claims. Initially, scientists thought that the arms were meant to hold its partner close during sex, but that may not be the case.

However, not everyone is convinced, with some scientists reportedly criticizing the claim as illogical. But it shows we have a lot to learn about this truly terrifying beast.

“For more than a century, many paleontologists have viewed the small arms of T. rex as having been vestigial. At ~1m long, these arms were not as tiny as often portrayed, and derived traits indicate that they were actually functional,” reads the statement from Stanley, as printed by the Geological Society of America. “The few previous suggestions of possible functions for the arms are all problematical. Six of the arms’ derived traits indicate that they were adapted for slashing at close quarters: (1) The shortness of the arms would actually have been advantageous for this activity.”