“nobody, not even the rain, has such small hands” wrote e.e. cummings. Not about the Tyrannosaurus Rex’s diminutive appendages, but nobody can be too sure. The T. Rex inhabits every childhood dream on dinosaurs—the massive and scaly creatures that roamed this earth 100 million years ago¹. If asked “what the most dangerous and powerful dinosaur was?” any sensible kid would respond “aye, the T. Rex.” With it’s oversized body, ground-shaking tail, and cavernous maw filled with row upon row of glistening teeth, how could it be anything but awe-inspiring. But its one oft-overlooked fault is its seemingly useless arms and hands—really, what could a creature do with arms like that?

For a long while, paleontologists just assumed its hands were for nothing. Many creatures has vestigial structures that once had a use, but then go out of style and mostly sit around in the gene pool slowly deteriorating over time. Two good examples in humans are the appendix and wisdom teeth.

Sara Burch, a researcher at Stony Brook University, in New York has spent a considerable amount of time contemplating the purpose of T. Rex arms and recently presented her findings at the annual meeting for the Society of Vertebrate Palaeontology, in Raleigh, North Carolina. Burch concludes that T. Rex arms were used for something, she just doesn’t know what yet.

Her reasoning is as follows: looking at muscle attachments points historically over the known T. Rex ancestry, if the record shows signs of atrophying over time then they could accurately be labeled vestigial. The record didn’t show it though. Instead it traced seemingly random patterns of strengthening and weakening but not a downward trend.

At around 70 million years ago, right before the T. Rex emerged, there was a noticeable change in the way the muscles functioned. As The Economist reports:

The animals’ forearms, for example, increased their ability to flex in the way that a human flexes his biceps. Their ability to pull their arms close in towards their torsos was reduced. Their ability to draw their arms out away from their bodies, however, went up.
 

The only thing left to do is wonder what those hands could be used for. Airspace theories include: patty-cake, conga drumming, cross stitch, playing the piano, sign language, spirit fingers, gesturing to emphasize a point in discussion, push ups, magic tricks, hand jive, and carrying baskets.

^{1The T. Rex lived closer in time to humans (60 million year difference) than it did to early dinosaurs (150 million year difference)}

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Attribution

The Economist