why did tyrannosaurus have such short arms? did it evolve or was it always like this and why?
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answers:
JimZ say: Much of that arm may have been enclosed in the body so they may have been even shorter than commonly depicted. They are balanced like a seesaw. It takes very little power to push them up since their tail counteracts everything in front. I think of them as a giant road runner. They didn't need arms so they evolved into very small almost unusable appendages.
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Elaine M say: Did not need arms for holding down prey, they used their back feet for that.
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Ray say: For the same reason Emu's have short arms; they don't need em!
Only purpose may have been for sexual intercourse.
Cal King also brings up a great point; theropods all balance on their hip. T-rex powerful jaw is front heavy, large arms would weigh more, meaning it would have needed more caloric intake for a larger heavier tail.
This balance issue explains why birds, who lost their tail to become light for flight, have a zig zag stance, with their femur leg bone almost vertical when standing [to balance them out], even birds who lost flight suffer from this. It's all about balance.
T-rex was a 6-9 tonne behemoth, it needed column like legs stance, femur bones would not be able to handle the vertical pressures small theropod birds do to their femur in able to balance.
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John say: God made it that way to stop it masturbating
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Cal King say: They evolved to have short arms. The reason they evolved short arms has been a mystery, but the most likely explanation is that it is because T. rex has a big, heavy skull that is used for crushing bones. Since theropod dinosaurs walked on 2 legs and they are balanced at the hip joint, that means the weight in front of the hip joint should balance the weight behind the hip joint in order for the animal to be able to keep its balance when walking. If it is too front heavy, then it could easily fall forward. Reducing the size of the arm allows the skull to get bigger without upsetting its balance.
If T. rex is an active predator, it would probably benefit from having long arms to be able to help it catch active prey. Indeed, scientists have found several fossil animals that have healed bite marks that match the size and shape of T. rex's jaws. That suggests that T. rex bit those animals but they escaped and their wounds healed before they died later. That in turn suggests that if T. rex cannot kill an animal with a bite, it has very little chance of preventing the wounded prey from escaping, ostensibly because of its short arms.
The short arms, therefore, reduce T. rex's ability to hunt. Despite this, T. rex thrived, and it was able to catch enough to eat. One possibility is that T. rex was primarily a scavenger even though it still tried to hunt. Indeed, some researchers have calculated the force that T. rex can put on its bones if it tries to run and they found that T. rex can break its bones if it tries to run. These facts all add up to suggest that T. rex was primarily a scavenger since it is too heavy to run and hunt. By having massive jaws, T. rex can crush bones and eat the bone marrow inside. Its large size also allows it muscle smaller predators from their kill. It also has the largest olfactory bulb of any known dinosaur. The olfactory bulb is the part of the brain that processes smells. It means T. rex can detect blood and meat from a long distance away. Despite its slow speed, it can still get to enough carcasses on time to keep itself from starving.
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Sir Caustic say: Tyrannosaurus Rex had perfectly normal-sized arms. However, it had really huge legs, a too-large body and a head on the biggish side. Hope this helped.
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Marvin say: llnrxffr
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wnhei say: cmymqaoi
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