Nanotyrannus: Dinosaur skeleton settles long debate over ‘tiny T. rex’ fossils

Dinosaur fossil, possibly a baby Tyrannosaurus rex it is actually an adult predator of a different species, according to researchers who believe they have finally put to rest a long-running and bitter debate in paleontology.

The controversy arose over a skull found in the Hell Creek Formation of Montana in the 1940s and originally classified as a skull. Gorgosaurusthen suggested being underage T. rex. In 1988, other researchers argued that the fossil was actually an adult of a smaller, related species, which they called Nanotyranus lanceolata.

Since then, a number of additional fossils have been identified. Nanotyrantbut many paleontologists I believe they are really underage T. rex samples.

Now researchers have analyzed a complete skeleton for the first time, which appears to show beyond any doubt that Nanotyrant this is a separate species.

The skeleton is one of a pair of fossil specimens dubbed the “Dueling Dinosaurs” that were discovered by commercial fossil hunters in 2006. Triceratops buried next to what was originally thought to be a minor T. rex about 67 million years ago.

This didn't exist until 2020when the fossil was acquired by the North Carolina Museum of Natural Sciences, paleontologists were able to study the remains in depth.

“When we purchased this example, we knew it was exceptional,” says Lindsay Zanno at the North Carolina Museum of Natural Science. “We had no idea that this would turn decades of research on the world's most famous dinosaur on its head.”

Zanno, who conducted the analysis with her colleague James Napoli at Stony Brook University in New York, says she was initially a supporter of youth T. rex theory, but evidence forced her to reconsider her opinion.

“Nanotyrant has a different arrangement of nerves and sinuses in the skull, more teeth, larger arms and a shorter tail,” she says. “We know that these traits do not change as animals grow from baby to adult.”

Detailed analysis of the dinosaur's limb bones confirms it was an adult about 20 years old, weighing about 700 kilograms and measuring about 5.5 meters long, Zanno and Napoli said. “This is about one-tenth the body weight and half the length of an adult. Tyrannosaur“, says Zanno.

Zanno and Napoli also reanalyzed 200 tyrannosaur fossils and concluded that another nearly complete skeleton from the Hell Creek Formation, known as Jane, which was thought T. rex teenager, was also misclassified. They say Jane is actually a new species in the genus. Nanotyrantwhich they call Nanotyrannus letaus.

“We only have one skeleton N. leteus“but its anatomy suggests it was a larger species,” says Zanno. “The pattern of the sinuses on the palate and the shape of the bone behind the eye are unique.”

Scott Persons The South Carolina State Museum says new research settles the debate about Nanotyrant being a separate genus and species.

“For my money, Nanotyrant was one of the most feared dinosaur predators,” says Persons. “This is the one I would least like to be followed.” It was extremely long-legged and armed with a vicious claw on its thumb.

“We can think about Nanotyrant And Tyrannosaur like analogues of modern cheetahs and lions. Yes, they have a generally similar body structure, but they specialized for different methods of hunting.”

Thomas Carr at Carthage College in Wisconsin, who spent a long time in juvenile detention T-Rex Camp, says the new evidence is “pretty compelling” that the dueling dinosaur specimen is “a near-adult species that is not T. rex“

AND Holly Ballard at Oklahoma State University, which topped the 2020 research refuting Nanotyrant claimssays she “agrees” with the team's conclusion that the fossil is approximately adult-sized.

But neither Ballard nor Carr is convinced that the other fossil, Jane, represents a new Nanotyrant variety. “Jane is still growing and is already bigger than N. lanceolateso to say that this is a new taxon, not a juvenile T. rex“,” says Ballard. “We're back to the same old debate.”

“Also, if every little tyrannosaurus from the Hell Creek Formation were Nanotyrantthen where are the minors? T. rex? says Carr. “This part of the picture doesn’t add up. As far as fossils go, we simply haven't collected enough Hell Creek Formation tyrannosaurs to truly understand what happened during the early stages of growth T. rex.»

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