So I can’t help but wonder, as so many have, why the mighty Jurassic monster chomper had such tiny little arms compared to its thick brutish bulk. Some consider it a vestigial feature but the Tyrannosaurus existed for millions of years, certainly long enough for these to vanish. There are speculative notions that it held onto wriggly prey or their mates during sex with them. Both of these seem like a stretch. You wanna try holding on to a love crazed 6 tons of passion with 3 foot tinker toy arms? How about a wriggly beast and trying to wrangle it into your massive meat crusher with fingers that can’t reach your Adam’s apple?
One thing we do now know about T-Rex is that they nested and cared for their small clutch of eggs and raised and guarded their young. Physical constraints on materials means that eggs can never be larger than a melon so that the baby T was teeny compared to its parents. How was such a beast supposed to corral such little wanderers, shift eggs about without breaking them, move suitable sized sticks and brush to hide and warm them? When a T-Rex bends flat its arms reach the ground nicely and, even though it cannot see them, they are small enough to exert small forces that might not immediately crush its young and perform such maternal tasks.
Interestingly, both males and females took part in this child care. Thus it makes sense that neither had arms more atrophied or less developed than the other. Sadly, fossils here are sparse. Small scratches on the eggs or nest materials that matched the three fingered claw of the adults might indicate this theory is true. Maybe instead of the comical “T-Rex Trying,” http://trextrying.tumblr.com/, we might have a loving ground fowl, wingless but with little hands to lift and launch its toothy pups into their first Jurassic mornings.
Physics Patch 