The arms of Tyrannosaurus rex have the become the stuff of legend. The butt of a million internet jokes about having short, useless arms the memes have become so prevalent that people are as likely to let out a laugh rather than a quiver of fear when they see one.
New research presented at the 2017 meeting of the Geological Society of America, however, wants to put pay to the mocking claiming that T. rex arms were actually well adapted for slashing at prey. Steven Stanley, of the University of Hawaii, argues that the arms were, in fact, highly adapted for this particular function. They were about a metre long and strong enough to survive the impact of slashing, he says, and the claws at the end were sickle shaped with a cutting edge that would be better for cutting than grasping. Further, the unusual reduction to two fingers from three would allow those claws to deliver more force and pressure than 3 more spindly ones.
Ancestors of the T. rex were known to be slashers, but as the size of the head increased and took over the grasping function then the arms became redundant and started to shrink. Stanley doesn’t dispute any of this, but why not get in a few good slashes once the fighting gets up close, he argues.
The work has not been universally accepted, however, the consensus still seems to be that their arms were just too diminutive to be effective at… well, anything. The jokes are not going to stop any time soon.