WEBVTT - BrainStuff Classics: Why Did the T. Rex Have Such Tiny Arms?

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<v Speaker 1>Welcome to brain Stuff production of iHeart Radio. Hey brain Stuff,

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<v Speaker 1>Lorenvolk bum here with a classic episode from our former host,

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<v Speaker 1>Christian Sagar. This one is near and dear to me.

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<v Speaker 1>Our topic for the day is why the Tyrannosaurus Rex

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<v Speaker 1>have such tiny arms? A brain Stuff it's Christian Sagar.

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<v Speaker 1>With a name that literally means tyrant lizard king, you'd

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<v Speaker 1>assume that Tyrannosaurus rex would get a bit more respect,

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<v Speaker 1>but the giant predators disproportionately small arms have been the

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<v Speaker 1>subject of ridicule for decades. They are also a scientific puzzle.

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<v Speaker 1>More than one hundred years after discovery of this species,

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<v Speaker 1>experts still don't know why a huge animal, one that

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<v Speaker 1>could reach links of forty feet or twelve meters or more,

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<v Speaker 1>had four limbs that weren't much longer than an adult humans.

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<v Speaker 1>If the arms were limp muscle free pegs, it'd easy

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<v Speaker 1>to assume that they serve no purpose. However, the evidence

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<v Speaker 1>hints at a more complicated story. A few studies have

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<v Speaker 1>argued that, judging by the muscle scars left behind on

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<v Speaker 1>t rex limb bones, a full grown dinosaur could curl

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<v Speaker 1>more than two hundred and twenty pounds or one hundred

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<v Speaker 1>rams with each one of their biceps. Then again, this

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<v Speaker 1>isn't as impressive as it sounds. Thomas ore Holtz, a

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<v Speaker 1>vertebrate paleontologist at the University of Maryland, tells us that

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<v Speaker 1>some people like to overrate tyrannosaurus is upper body strength.

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<v Speaker 1>That figure from before only translates to about one point

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<v Speaker 1>to five per cent of the dinosaurs total body weight,

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<v Speaker 1>which may have been in the ballpark of around eight

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<v Speaker 1>tons or eight thousand kilograms. Holtz says that's like a

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<v Speaker 1>two hundred pound or nine man being proud of the

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<v Speaker 1>ability to curl two point five pounds or one kilogram.

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<v Speaker 1>On these grounds, A few experts have concluded that Tyrannosaurus's

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<v Speaker 1>arms were either functionless or seldom used, but not all

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<v Speaker 1>paleontologists by this idea. For his money, Kenneth Carpenter of

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<v Speaker 1>Utah State University thinks the little limbs made great hunting tools.

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<v Speaker 1>In two thousand eight, he and fellow paleontologist Christine Lipkin

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<v Speaker 1>compared the five Tyrannosaurus rex wishbones or ferculars that were

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<v Speaker 1>known to science at the time. Shaped like a giant boomerang,

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<v Speaker 1>the fercular sits between the shoulder blades. Three of the

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<v Speaker 1>five wishbones that Carpenter and Lipkin studied show telltale signs

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<v Speaker 1>of injury. Among these were stress fractures, which must have

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<v Speaker 1>re healed in life. So what does this mean? While

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<v Speaker 1>according to Carpenter, the four limbs were subjected to a

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<v Speaker 1>great deal of repetitive stress, which was not uniform or steady. Instead,

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<v Speaker 1>there were moments of x e straordinarily great force applied

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<v Speaker 1>to the arms. The most likely explanation is that t

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<v Speaker 1>Rex used its four limbs to grab hold of large

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<v Speaker 1>struggling prey. A plus sized thrashing victim could easily fracture

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<v Speaker 1>the carnivores wishbone or at least tear a few arm

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<v Speaker 1>muscles loose. Other ideas about the purpose of t rex

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<v Speaker 1>arms have nothing to do with subduing victims. One school

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<v Speaker 1>of thought involves naptime. Perhaps after a good night's sleep,

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<v Speaker 1>Torannosaurus used those arms to push itself up off the ground,

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<v Speaker 1>or maybe they had a sexier function. Henry Fairfield Osborne,

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<v Speaker 1>the paleontologists who named this species back in nineteen o five,

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<v Speaker 1>believed that males used their four limbs to grab hold

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<v Speaker 1>of their mates as Holts and others have admitted there

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<v Speaker 1>simply isn't enough evidence at this time to conclusively refute

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<v Speaker 1>or verify any of these notions. Much is often the

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<v Speaker 1>nature of paleontology. Today's episode was written by Mark Fancini

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<v Speaker 1>and produced by Dylan Fagan and Tyler Clang. For more

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<v Speaker 1>in this and lots of other topics, visit how stuff

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<v Speaker 1>works dot com. Brain Stuff is a production of iHeart Radio.

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