It was a big day today for dinosaur news! First we found out that the T-Rex was even bigger than we thought. And now we've learned that the two-horned Carnotaurus was way faster than scientists realized.

It's thanks to his ginormous tail muscle. Scott Persons, a post-doc at University of Alberta in Canada, found that the Carnotaurus doesn't use the muscle just to swing the tail around. The caudofemoralis muscle had a tendon that attached to its upper leg bones. That pulled the legs backwards with each step, allowing it to run with unimaginable velocity.

Persons' made his observation, which he published in the October 14 issue of PLOS ONE, after noticing rib-like, interlocking bones along the tail. He re-created the tail muscles using 3-D computer models to determine the tendon's function. One drawback: the tail was rigid, making quick sideways moves were difficult. So the Carnotaurus may not have been nimble, but it more than made up for that by coming at its prey with a quickness. And a bit of trivia: for its size, it had the largest caudofemoralis muscle of any known animal, living or extinct.

Persons is on a roll; he found the same phenomenon with T-Rex last year. Before he published that work, many researchers thought the giant T-Rex tail was mainly a counter-balance for its huge head. Dinosaur world is looking scarier than ever. [PLOS ONE]


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