Guanlong, a distant ancestor of Tyrannosaurus rex from China, lived during the Jurassic period. Unlike its famous descendant, Guanlong was not an apex predator and was modest in size. This dinosaur reached 3-3.5 meters in length, 1-1.2 meters in height, and weighed 75-125 kg. The crest on its head was useless in combat or hunting, so it was used only for display during mating season, like the tail of a peacock