THE THREE FACES OF Tyrannosaurus rex?

All species of creatures contain variation. But when does variation bleed into differentiation and separate identifiable species? Within the science of paleontology, this question has led to “lumpers” versus “splitters.” Lumpers say that plants and animals come in varied forms, but all those varied forms might simply represent variations within a single species. Splitters beg to di er. Rather than one encompassing species, they might split into separate species or subspecies. Such esoteric debates have now engulfed one iconic dinosaur species, Tyrannosaurus rex.

A group of paleontologists led by freelance researcher Gregory Paul has examined over three dozen specimens of T. rex residing in collections worldwide. In an article in the journal Evolutionary Biology, they say they’ve spotted what they believe to be enough variation over time to justify dividing this dino into three separate species: T. rex, T. imperator and T. regina.

Will these “splitters” prevail? Says paleontologist Steve Brusatte (University of Edinburgh, Scotland), “Ultimately, to me, this variation is very minor and not indicative of meaningful biological separation of distinct species.”