About a dozen T. rex skeletons have been found. T. rex dung has been found containing crushed bone - its teeth were capable of inflicting an enormous amount of damage on other creatures.
Diapsids are animals that have two extra holes in the sides of their skulls.
Other animals that are digitigrade include dogs, cat, and chickens. There is a pad of tissue on the back of the feet on these animals that acts like a shock absorber. Its legs were very strong and powerful. The upper part of the arm was imbedded in its body, rendering the arms almost useless and with a very limited range of motion. Just click on an animal's name to go to that information sheet.