When fossil hunters unearthed the remains of a dinosaur in the hills of eastern Montana five years ago, they had several key features of a Tyrannosaurus rex: a giant pair of legs for walking, a much smaller pair of arms for cutting off their prey and a long tail stretching behind him.
But unlike an adult T. rex, which would be about the size of a city bus, this dinosaur was more like the size of a pickup truck.
The specimen, now on sale for $20 million at a London art gallery, raises a question that has come to obsess paleontologists: is it simply a young T. rex that died before reaching maturity, Or does it represent a different, but related species of dinosaur known as Nanotyrannus?
The dispute has produced a wealth of scientific research and decades of debate, polarizing paleontologists along the way. With dinosaur fossils fetching increasingly exorbitant prices at auction, the once-esoteric dispute has begun to spread through auction houses and galleries, where some see the T. rex name as a valuable brand that can fetch high prices. more easily.
“Ultimately, this is a pretty complicated question about the taxonomy and classification of a very particular type of dinosaur,” said Steve Brusatte, a paleontologist at the University of Edinburgh. “However, this is a T. rex, and the debate always gets a little fiercer when it comes to the king of the dinosaurs.”
On the Internet, juvenile T. rex versus Nanotyrannus has become something of a meme, fueling jokes on specialized social media channels. (“I won’t believe in Nanotyrannus until it shows up on my doorstep and devours me,” a paleontology student with the pseudonym “TheDinoBuff” recently joked on social networking site X.)
The gallery selling the specimen discovered in Montana, known as Chomper, faced a choice. Call it a juvenile T. rex? Label it Nanotyrannus? Or accept the ambiguity of an unresolved scientific debate?
The David Aaron gallery in London chose to call it “rare juvenile Tyrannosaurus rex skeleton.” He cited an influential 2020 paper on the topic led by Holly N. Woodward, which used growth ring analysis within bone samples from two disputed specimens, estimated to have been similar in size to Chomper, to argue that They were juveniles about to grow up. jets.
Salomon Aaron, the gallery’s director, said paleontologists had advised him to classify the skeleton as a juvenile T. rex, and questioned whether either label was necessarily more lucrative.
“I don’t think it had any impact on the price because by any measure it is a magnificently complete, beautifully preserved and extremely rare specimen,” Aaron said.
But Pete Larson, a fossil expert known for his involvement in the excavation of two of the world’s most famous T. rex, Sue and Stan, said he believed Chomper was a Nanotyrannus. The specimen was featured in a 2020 episode of the Discovery Channel documentary series “Dino Hunters,” in which Larson pointed to the size of its hand bones and the apparent fusion of its nasal bones as evidence that it was not a T. juvenile rex.
“There’s a group of scientists who say it’s a juvenile T. rex and there’s a group of scientists who say it’s a Nanotyrannus,” Larson said, in an interview, of the choice facing the gallery. “So they will choose the one who makes the most money.”
Another specimen that is sure to shape the debate in the coming months is a paleontological marvel known as the Dueling Dinosaurs, a remarkably well-preserved Tyrannosaurus fossil that was discovered next to the remains of a Triceratops, giving the impression that the animals could have dead. while they fight each other.
The dueling dinosaur specimen, which was discovered by a team led by Clayton Phipps, the same fossil hunter who excavated Chomper, was out of reach of researchers for years, hidden during a court battle over who owned it. But once the legal issues were resolved, the North Carolina Museum of Natural Sciences acquired it in 2020. This spring, the museum plans to open an exhibit where the public will be able to visit the dueling dinosaurs at the same time as paleontologists. They are actively studying. he.
One of the questions they will study is how, exactly, the tyrannosaurus should be classified.
“We need to solve what, in my career, has been one of the most complex questions to address, because you have to distinguish so many variables,” said Lindsay Zanno, the museum’s director of paleontology, listing growth, sex and fossilization. process as examples. “That’s why it has perplexed the scientific community for years.”
The origins of the paleontological debate date back to 1942, when an expedition from the Cleveland Museum of Natural History unearthed a 22-inch dinosaur skull in Montana. It was originally identified as a Gorgosaurus, but in the 1960s new analysis argued that it belonged to a juvenile T. rex.
The debate has continued since then. Even to non-scientists, there are clear differences between that specimen’s skull and that of adult T. rex: the smaller skull has a thinner snout and thinner, blade-like teeth. In the late 1980s, research led by paleontologist Robert T. Bakker argued that these differences, among many others, indicated that the specimen was a new species. He named it Nanotyrannus lancensis.
But about a decade later, paleontologist Thomas Carr presented the most detailed argument yet that the 1942 specimen was actually a juvenile T. rex, and attributed the differences to its immaturity. “Every bone in the skeleton of these animals changes with growth,” said Carr, who has researched the question for more than 20 years.
Since the turn of the century, the debate has been fueled by the discovery of new specimens, including a 21-foot-long one named Jane. One of the specimens in Woodward’s study, it was unearthed in Montana in the early 2000s and is on display in Rockford, Illinois, at the Burpee Museum of Natural History.
In the latest foray into the debate, Nick Longrich, a paleontologist at the University of Bath, has defended Nanotyrannus as a distinct species, contradicting Woodward’s key conclusion about Jane and another specimen in a preprint of a paper that caused a stir among his colleagues. . at the October meeting of the Society of Vertebrate Paleontology.
“It’s almost become religious,” Longrich said of the passions stirred by the debate, describing it as “one of the ways group identity is signaled” in paleontology circles.
But science, of course, is based on evidence, and many paleontologists believe that to truly end this dispute more is required. That’s where some worry about the growing market for dinosaur fossils in auction houses and art galleries.
Academic paleontologists see the rise in dinosaur prices, following the sale of T. rex Stan in 2020 for $32 million, as a growing crisis in their field, fearing that important specimens could end up out of reach. researchers.
Aaron, from the London gallery, said he hoped Chomper would go to a museum where scientists could study it, but there is no guarantee.
“We need more specimens to solve the mystery,” said David Evans, a paleontologist at the Royal Ontario Museum. “And this is exactly the kind of sample scientists need.”
Kirsten Noyes contributed to the research.
