Tyrannosaurus rex

Tyrannosaurus rex was an Earth dinosaur.

An USS Enterprise landing party encountered a tyrannosaur during a mission to prehistoric Earth. 

Both the Gorn and Neon's species  resembled tyrannosaurs.

Ruth Rigel once described a tigrex as being as big as a Tyrannosaurus rex and twice as mean. Le-matyas were also described as being the size of Tyrannosaurus rex. 

James T. Kirk, while observing a V'asumi match between Spock and Savaj, in which both used their full Vulcan strength, thought that ordering them to stop would be like ordering Tyrannosauri rex to cease hostilities. 

Kirk once called Vaal a "goddamned tyrannosaur head with the horn on top".