Luckily, PBS has a series that is perfect for dino-lovers of all ages and minimal attention spans. Eons, hosted by Hank Green, Kallie Moore, and Blake de Pastino, takes a look at the long evolution of ancient creatures every Tuesday on their YouTube channel. And one of the most recent episodes deals with a mystery that has plagued paleontologists and children for years: Just why does the Tyrannosaurus Rex have such ridiculously tiny arms? In the video above, first shared by Laughing Squid, Green covers the salient points with humor and speed. Take a few minutes out of your day to learn new trivia to impress your friends with over-grilled hot dogs and fireworks this weekend.
No time to watch? Here are the highlights:
– T. rex evolved from a Triassic Prosauropod called Riojasaurus, which walked on all fours. But as the millennia passed, the Riojasaurus gave rise to the likes of Plateosaurus and Jingshanosaurus, which walked on their hind limbs.
– By the time the genus Tyrannosauridae came into existence, the forelimbs had evolved into spiky death claws. Over time, the carnivores’ tails became used for balance while their skulls became larger and more powerful. As such, their forelimbs were no longer needed for hunting or balance and began to recede.
– However, T. rex arms still had musculature, so they weren’t vestigial. Theories as to their use include holding the dinosaur steady during mating, or holding prey still while eating. They could also have been on their way to evolving completely out of the species, but the mass extinction put a kibosh on that evolutionary plan.
Got any “alternative” theories on T. rex arms? Let us know!
Images: PBS EONS/Walt Disney Pictures