TYRANNOSAURUS REX. It may have been extinct for some 66 million years, yet Tyrannosaurus rex is by far the best known and most recognisable of all the dinosaurs. This could be due to the large number of tyrannosaurs fossils – among them several almost complete skeletons – discovered over the years, mostly in western North America. But it may also be because the T-Rex, as it is known colloquially, was one of the most terrifying animals to have ever walked the earth. It features in all its fearsome glory on the fifth coin in the Supersaurs series.