Tyrannosaurus rex is a species of tyrannosaurian theropod dinosaur that went extinct at the end of the Cretaceous period, 65 million years ago. For some reason, they are sometimes seen on the battlefields in the 20th century.
T. rex appears in the following skirmish maps:
Circuit Board: Two T. rex appear alongside many other units and buildings that originally appeared only in the campaign of Yuri's Revenge. They can't attack and will run away in fear if fired on.
Irvine, California: T. rex appear among the many animals in this zoo-like map. Unlike in Circuit Board, these T. rex can fight, though they will only do so if attacked first.
In Mental Omega v2.0, the T-Rex can be built if a Tech Time Machine is captured.