Researchers Suggest , Tyrannosaurus Had 3 Separate Species, , Not Just Rex.br A group of researchers now believe that br Tyrannosaurus actually consisted of three br separate species and not just a single T. rex. .br Reuters reports that the T. rex has br long been recognized as the sole genus br of Tyrannosaurus since its discovery in 1905. .br Independent paleontologist and paleoartist br Gregory Paul and his team examined the remains br of about three dozen Tyrannosaurus fossils. .br Their research led to the recognition of two additional species: , T. imperator, meaning "tyrant lizard emperor," br and T. regina, meaning "tyrant lizard queen.".br After over a century of all specimens br being placed into one species without br the issue being carefully examined, br the first and only analysis finds that br the variation in Tyrannosaurus br is beyond the norms for dinosaurs, , Gregory Paul, Independent paleontologist br and paleoartist, via Reuters.br ... and is distributed over time br in a manner that indicates that br Darwinian speciation from one br (species) to two new species br had occurred before the br final dinosaur extinction br cut off further evolution, Gregory Paul, Independent paleontologist br and paleoartist, via Reuters.br Reuters reports that Tyrannosaurus br roamed western North America br until about 66 million years ago. .br According to Reuters, there remains some br disagreement among paleontologists. .br Critics of the study claim that the variations br are not enough evidence to clearly definebr a new species of Tyrannosaurus. .br It's hard to define a species, even for animals br today, and these fossils have no genetic br evidence that can test whether there were br truly separate populations. Until I see much br stronger evidence, these are all still T. rex br to me, and that's what I'll be calling them, Steve Brusatte, University of Edinburgh br paleontologist, via Reuters.br It's hard to define a species, even for animals br today, and these fossils have no genetic br evidence that can test whether there were br truly separate populations. Until I see much br stronger evidence, these are all still T.