Tyrannosaurus Rex Might Not Have Been Alone At the Top of the Food Chain

Tyrannosaurus rex, the most famous dinosaur in popular culture and long considered the apex predator of its era, was apparently not alone. Thigh bone and tooth variations in assembled T-rex skeletons have led a group of researchers to speculate that there are at least three different members of the tyrannosaurus genus. The tyrannosaurus rex was discovered in 1905 and has long been considered the only species within its genus, but Reuters reports that the speculation about more potential tyrannosaurs comes from dozens of skeletons from around the world. Since it is unusual to find a full dinosaur skeleton intact in one place, it is possible to make errors.

When a skeleton is missing pieces, This is accomplished in a variety of ways, including being replaced by fossil bones or casts from another individual dinosaur, provided they are the same species. The theory here is that some of the bones previously assumed to be T-rex bones are in fact one or more previously undiscovered tyrannosaurus species, which were lumped in the the rex erroneously over the years.

Three researchers, led by paleontologist and paleoartist Gregory Paul, made the claim on Monday. They believe their findings are sufficient to recognize two additional species, which they named T. imperator (meaning "tyrant lizard emperor") and T. regina ("tyrant lizard queen"). Tyrannosaurus rex means "tyrant lizard king."

"After over a century of all specimens being placed into one species without the issue being carefully examined, the first and only analysis finds that the variation in Tyrannosaurus is beyond the norms for dinosaurs, and is distributed over time in a manner that indicates that Darwinian speciation from one (species) to two new species had occurred before the final dinosaur extinction cut off further evolution," Reuters quotes Paul from his piece in Evolutionary Biology. "It is a concern that this will be controversial because of the charismatic status of T. rex, but on the other hand the study would not be getting so much attention otherwise."

"Ultimately, to me, this variation is very minor and not indicative of meaningful biological separation of distinct species that can be defined based on clear, explicit, consistent differences," University of Edinburgh paleontologist Steve Brusatte told Reuters. "It's hard to define a species, even for animals today, and these fossils have no genetic evidence that can test whether there were truly separate populations. Until I see much stronger evidence, these are all still T. rex to me, and that's what I'll be calling them."