The most famous dinosaur is tyrannosaurus rex. Its skeletons hold pride of place in museums around the world, and sell for millions of dollars at auction, making it the most thoroughly studied dinosaur in the world.
Three researchers argue in a new paper that the animal we currently call T. rex should be split into three separate species.
Gregory Paul said that the paper is likely to rock the paleo community and the public that is used to good old T. rex.
The experts of tyrannosaurs disagree. The evidence for multiple species is "vanishingly weak" according to Thomas Carr, a paleontologist at Carthage College. The curators at the museums with the tyrannosaurus rex say they are not going to change anything because of the proposal.
The premise put forward by Mr. Paul and his colleagues highlights an assortment of tensions in dinosaur paleontology. Each new species description is more of an argument than a declaration, and naming dinosaur species is a subjective process. Some researchers think that there is merit to the idea of multiple tyrannosaurus species, but they say that splitting apart a famous and well-studied tyrannosaurus rex requires a high standard of evidence.
If Mr. Paul is proved right, he wouldn't be the first researcher to change a consensus in the field, or the first to bite off more than he can chew.
The scientific names are divided into two categories. The tyrannosaurus is capable of holding multiple species. There is only one tyrannosaurus rex.
David Hone is a paleontologist at Queen Mary University of London. There is no universally consistent agreement on what constitutes a species. To separate them in living animals, scientists rely on a number of factors. Animals of the same species at different ends of a large geographic range can vary a lot from one another.
In the absence of prehistoric DNA, dinosaur paleontologists must rely on the details of the bones found at different stages of growth. Scientists assigning multiple names to the same animal can lead to headaches, like with the case of Brontosaurus, which was junked for more than a century before the name was revived in 2015.
The name tyrannosaurus rex has been around for a long time. The last and largest tyrannosaur that preceded it in the dinosaur era was discovered in 1901. Its fossils have been found in the Hell Creek Formation, a band of 66-million-year-old rocks that records the last million years of the dinosaurs.
Mr. Paul said that the rex was known from only two decent specimen. The T. rex skeletons trickled into museums in the 1990s as dinosaur fossil collecting boomed. Their proportions showed a remarkable amount of individual variation, and some researchers argued that they fell into two groups: the bulky form and the relatively svelte form. Others said that it was an unusual degree of individual variation. There was a third possibility that the dinosaur was more than one species.
Mr. Paul was one of those researchers. Mr. Paul has a long history in paleontology and has written or been a co-author of over 30 scientific papers. He has proposed new genera and species for other dinosaurs. He made an argument about the dinosaur. He made another one about Iguanodon. His work influenced Michael Crichton, the author of the novel "Jurassic Park", as well as the makers of the movie based on it.
The question of T. rex's identity was asked by Mr. Paul and others in 2010. The relative proportions of the femur and the presence of two sets of chisel-like front teeth in their lower jaws were assessed according to a pair of anatomical traits.
They compared the tyrannosaurus specimen collected from across North America to the Allosaurus specimen collected from the University of Utah. They said that the T. rexes had a larger variation in body proportions, suggesting they might belong to more than one species.
Some of the specimen were difficult to classify. Mr. Paul said that there were three types of 26: one robust form from early in the Hell Creek with two sets of incisors in its lower jaws, and a robust and gracile form from later with only one incisor set.
Mr. Paul and his colleagues concluded that the forms were probably different enough to warrant separate names. Over the course of one million to two million years, the name of the earliest, bulky tyrannosaurus rex to show up in the Hell Creek was called the Tyrannosaurus imperator.
Mr. Paul said that the evolutionary trajectory from one tank-like population to another relatively lithe one matches the one that existed earlier in the Cretaceous period. The long-legged hunters such as Gorgosaurus coexisted with bruisers like Daspletosaurus.
It is plausible, but it will need support from future finds.
It is a testable hypothesis, as any statement of species identity should be.
The case would be more convincing if the different species were organized in chronological order in the Hell Creek Formation. There was a general agreement that there was more than one species of triceratops. There is a chance that the hadrosaurs and dome-headed Pachycephalosaurus found at the top of the formation differ from the ones found at the bottom.
The same size classes of organisms are going through a succession.
Some people took a less positive stance.
A major problem with the study is that the femur proportions of all three proposed species overlap rather than showing clear separations. The proposed periods of time in which they existed are the same. It suggests a continuous spectrum of change, which is not the differences you would expect in three species.
The diagnoses provided for each species are very vague.
Dr. Carr of Carthage College said that the proposed species groupings don't necessarily match existing data. After reading the study, Dr. Carr compared its conclusions to an analysis he did in 2020. There was no correlation between the 2020 data and the types Mr. Paul's team described.
Dr. Carr said that four of the specimen have perfect skulls.
Philip Currie, a paleontologist at the University of Alberta, took his name off the project after concerns were raised about Mr. Paul's paper.
The paper shows that there were changes in the appearance of the dinosaur over the years.
The paper proposes an impact on museum collections. The Field Museum's nearly complete T. rex is now the holotype of the species. The Nation's T. rex has been anointed the holotype by the National Museum of Natural History.
Mr. Paul hoped museums would use the debate around his conclusions to educate the public about science. He promises to raise a fuss if they try to ignore it.
The Field Museum won't be changing the labels on Sue anytime soon.
Even if everyone agreed with the team's proposal, at least one of Mr. Paul's proposed names might be dead in the water. Some researchers think it's a separate group of tyrannosaurs. Most people think of it as a juvenile T-Rex.
It would take precedence over the tyrannosaurus imperator because the species name has been around longer.
Mr. Paul believes that the new species names are reasonable, and that many dinosaur species are named based on less evidence.
If his team had simply published an argument for splitting up the dinosaurs without naming them, someone else would have been able to swoop in and do so, which would have been very upsetting.
He said that they went ahead and named them because he wasn't going to let that happen.
Dr. Hone said that pointing out a few different characteristics and linking them with different rock layers could make a good case for naming a new species. It requires a higher standard to split up T. rex.
In Mr. Paul's 1998 book, "Predatory Dinosaurs of the World", he proposed unifying dinosaur Taxonomy. The suggestion didn't stick, except in the novel and subsequent films, which feature velociraptors.
It will be decades of public confusion and argument if you have got it wrong. It will be centered on T. rex, the most famous dinosaur.
It's not the kind of thing you should be doing because of the presence or absence of a tooth.
Mr. Paul and his team are taking advantage of the fact that species concepts in dinosaur paleontology are best summarized by a shrug, said Leonard Finkelman, who studies the philosophy of paleontology at Linfield University in Oregon. He says that until dinosaur paleontologists work out a consistent standard for the minimum anatomical differences it will be hard to name a new species.
Dr. Finkelman said that provocative proposals can have value. Sometimes an idea that is poorly supported can be supported in the future. When new ideas prompt researchers to revisit old work, that is one way science can progress.
Whether it makes a visible contribution now, forcing scientists to go back and look at their old data is always going to be a useful exercise.
That is what Mr. Paul wants.
He said that there could be a lot of people who aren't happy about it.
All Rights Reserved © 2024
