why did tyrannosaurus rex have such small fore limbs?

Answer 1

The truth his that no one knows the answer to this question - it's one of the unsolved mysteries of their biology.

I should add that while T. Rex has very small forelimbs, the musculature surrounding these arms is well-developed. They may have been small, but they were also strong. This means they were doing something with them.

Answer 2

There are many examples of animals living today that have 'vestigial' parts to their bodies. This means a body part that has, for example, diminished in size over thousands or millions of years of evolution because it has become redundant. An example would be the slow worm, a lizard that looks like a snake because it has no legs but which on close examination can be seen to have tiny nodes where its legs once were; these legs became redundant when the animal, for whatever reason, came to find itself capable of moving in the manner of a snake. The process, incidentally, can work both ways i.e. a slow worm that found itself needing its legs again to survive would evolve them again or a species of snake that might never have had legs could evolve them. The tyranosaurus' tiny forelegs were that way in the fossils we have found of them because that was the stage of evolution that they were at when they were wiped out. They clearly were surviving and breeding without longer forelimbs so having long forelimbs was not necessary to them; this means they must have been doing what they did (killing and eating other dinosaurs) in some manner that didn't use the forelimbs e.g. by waiting stealthily in shadows and then rushing out upon its prey upon its powerful hind legs (which were similar to those of an ostrich today) and catching the prey in its massive jaws. Would it need forelimbs to tear meat off the prey and put it into its mouth? Obviously not, since its forelegs were too short to reach; therefore it MUST have gotten its meat into its mouth some other way e.g. by standing on the meat, leaning forwards and biting into it, and then rising up to tear the meat from the carcass. Birds can be seen today tearing food morsels in this way. So in short, there WAS no purpose for those short forelimbs of the tyranosaurus.

Answer 3

They were not needed for locomotion, or for grabbing anything. His very large head had a very large mouth that was used for everything he wanted to grab (kill, eat). Longer forelimbs may just have gotten in the way of his mouth or his natural gait. Small raptors used claws on their legs to attack with, so they only used their forelimbs to help hold on to prey. T Rex probably didn't jump on prey because of their size, and probably couldn't sprint. T Rex may just have been primarily a scavenger.

Answer 4

Maybe he didn't need them for anything (like killing), since his mouth did enough damage by itself.

Or if you buy the theory that he was a scavenger, then he didn't need to kill anything (so no need for claws), he just needed to eat it.

Answer 5

believe it or not, the T-rex is related to the chicken.