The world’s most iconic dinosaur is undergoing an identity crisis.
In February, a team of scientists posited that Tyrannosaurus rex was actually three distinct species. As a substitute of there being just one sovereign “tyrant lizard king,” their paper made the case for a royal family of supersized predators. Joining the king within the genus Tyrannosaurus can be the bulkier and older emperor, T. imperator, and the slimmer queen, T. regina.
The proposed T. rex reclassification struck the paleontology community like an asteroid, igniting passionate debates. On Monday, one other team of paleontologists published the primary peer-reviewed counterattack.
“The evidence was not convincing and needed to be responded to because T. rex research goes well beyond science and into the general public sphere,” said Thomas Carr, a paleontologist at Carthage College in Wisconsin and an creator of the brand new rebuttal. “It could have been unreasonable to depart the general public considering that the multiple species hypothesis was fact.”
The sooner team of researchers have anticipated the rebuttal, which was published within the journal Evolutionary Biology. Gregory Paul, one among the authors of the unique study, is working on one other paper and says lots of the rebuttal’s claims are outlandish.
“I don’t like flat-earthism since the evidence is against it,” said Mr. Paul, who’s an independent researcher and influential paleoartist. “It’s the identical here: the evidence indicates very strongly that there are multiple species.”
This king-size taxonomic debate seems destined to rage for epochs. Which is unsurprising considering how difficult it’s for researchers to distinguish prehistoric species. Without dino DNA, the lines between one fossil species and one other are messy. So paleontologists measure different traits, like the scale and shape of a specific bone. Nevertheless, the fossils could be misleading, as spending eons entombed underground can distort bone. And that is before considering how sexual differences, injuries, illness and natural variation sculpt bones throughout the animal’s lifetime.
In living populations, warped traits are balanced by large data sets. However the sample sizes of even well-known dinosaurs like T. rex are tiny in line with Philip Currie, a paleontologist on the University of Alberta who was not an creator on either study. “The elemental problem is that although the rough estimate of 100 known specimens of Tyrannosaurus may sound like lots, it just isn’t nearly enough,” Dr. Currie said.
With paleontologists forced to decipher these fragmented puzzles, the sphere is suffering from mistaken identities and defunct species names. And even the legends should not immune — T. rex’s fossil foe, Triceratops, experienced its own naming drama in 1996 when scientists split the three-horned herbivore into two species.
But perhaps no scientific name is as sacred as Tyrannosaurus rex. Because it was named in 1905, the world’s most-studied dinosaur has maintained its moniker. But Mr. Paul and colleagues’ recent study threatened to send shock waves through museum halls by rebranding their star attractions.
Several scientists immediately had their doubts. The initial study focused on the bulkiness of Tyrannosaurus femurs and the existence of two sets of incisor teeth poking out of the predator’s lower jaw.
Within the rebuttal study, Dr. Carr claims that neither trait is distinct to any of the purported Tyrannosaurus species. “The features that were claimed to be different between the three species were actually overlapping,” said Dr. Carr, who published a meticulous study examining traits in greater than 40 T. rex specimens in 2020. “There wasn’t any clean break between the various species — we have now to have a better standard than that.” He adds that several well-preserved Tyrannosaurus specimens fail to fall into any proposed species based on their teeth and the heftiness of their femurs.
Additionally they aim to puncture the statistical analyses utilized in the unique paper. Based on James Napoli, a paleontologist on the American Museum of Natural History in Recent York and a co-author on the rebuttal, the statistics used were misleading since the authors defined the variety of species they expected before running the tests. “It’s an ideal test should you’re attempting to predict which individuals belong to which group and what number of groups are in your data,” Dr. Napoli said. But using it to seek out distinct clusters is less useful because “it would all the time group the info into the variety of groups you tell it to.”
In the unique paper, the researchers compared the variation between individual Tyrannosaurus specimens with the variation found between several Allosaurus skeletons. Nevertheless, the rebuttal claims that comparing the apex predators is misleading since the Allosauruses hail from a single bone bed in Utah while the Tyrannosaurus fossils got here from a scattering of web sites over an extended time period. Due to this fact, they are saying, higher amounts of regional and temporal variation within the Tyrannosaurus data set needs to be expected.
The rebuttal team also considered the variability of T. rex’s living relatives — birds. After examining the femurs of 112 species of living birds, the team deduced that the differences between T. rex femurs were relatively unremarkable.
But Mr. Paul believes one other feature could make this variation more apparent. In an upcoming study, he posits that the sort of horns adorning Tyrannosaurus’s skull are distinct to every species, just like the contrasting crests differentiating cassowary species. He says that the horn-encrusted brow of T. imperator consisted of spindle-shaped lumps while T. rex’s horns were knobbier. “This could seal the deal,” Mr. Paul said.
Dr. Napoli just isn’t convinced. Just like the armor of contemporary crocodiles, these bony outgrowths were likely encased in keratin, protecting continually growing bone underneath. He thinks the form of a T. rex’s horns probably modified because the animal aged.
The one thing each sets of researchers agree on is the necessity for more Tyrannosaurus specimens. “When more skeletons are found, they’re added into the info set and eventually a method or one other, the statistical support goes to be so strong that reasonable scientists cannot disagree,” said W. Scott Individuals, a paleontologist on the College of Charleston and a co-author with Mr. Paul on the sooner paper.
While neither side is able to give up, Peter Makovicky, a paleontologist on the University of Minnesota who was not involved with either study, believes the continued back-and-forth surrounding Tyrannosaurus rex’s identity is nice for paleontology since it allows the general public to experience the minutiae that defines the discipline.
“This offers the layperson an insight into why we care a lot about differentiating latest species within the fossil record,” said Dr. Makovicky, who counts himself within the single-species camp. “It could be very difficult to persuade someone of that if it’s a brachiopod, but T. rex takes it to a different level.”