A New Type of T Rex

A remarkably complete tyrannosaur specimen was unearthed in the middle of Montana. It may finally settle one of the most contentious arguments in paleontology. While it’s at it, it might also upend our understanding of Tyrannosaurus rex, one of the most famous extinct animals on Earth.

The new fossil, along with others that had been assumed to be teenaged T. rex, are actually part of a distinct group called Nanotyrannus. Researchers had discovered differences in the bones, as well as evidence that the new fossil was a mature adult that had stopped growing, not an immature T. rex. The study also creates a more diverse picture of predators of the late Cretaceous by making the case that there were two species of nanotyrannus.

Originally, nanotyrannus were first identified as a separate species in the mid-1940s, but many came to believe they had been misclassified. They said the smaller versions were simply T. rex teenagers.

But if these were not teenagers, other questions arose: Did these different species interact? Did they hunt different prey? What did T. rex adolescence look like?

This paper states that Nanotyrannus is a distinct tyrannosaur species. Which indicates a reassessment of tyrannosaur classification is needed. Which is how science works.

For decades, nanotyrannus proponents had been marginalized by scientific consensus that they were young tyrannosaurs.

In a paper published in 1946, Smithsonian paleontologist Charles Gilmore described a new carnivorous dinosaur whose skull was found in Montana. At the time, he described it as a Gorgosaurus, a slightly smaller species of tyrannosaur. Four decades later, the skull was reanalyzed and a new paper proclaimed it a nanotyrannus.

Nanotyrannus lancensis was less than half the length of T. rex, although it was a relatively long-limbed animal. It is thought it would have been more graceful, not like the stocky, stomping brute of a T. rex.

Thomas Carr suggested in 1999 that nanotyrannus were simply youthful T. rex, and that explanation took hold.

In 2021, a North Carolina Museum acquired a 30,000 pound slug of bone and rock. They thought it contained a juvenile T. rex and a triceratops that had been buried together in Montana. Soon, they realized it was not a juvenile because its hand was really big. Far bigger than the hand of a fully grown T. rex.

A detailed analysis of the fossil found distinctive differences, such as the way cranial nerves threaded through the skull and the patterns of sinuses in the skull. Then, they cut into a limb bones, where the growth rings showed it to be about 20 years old, and it was a mature individual that had stopped growing… at less than half the length of a full-grown T. rex.

So they reexamined 120 existing fossils. One (called Jane) was assumed to be a young T. rex. She was a nanotyrannosaur, but a different species than the others they were studying.

So, kids can still have a favorite dinosaur, even a favorite tyrannosaur. It just might not be the well-known tyrannosaurus rex.

 

https://www.msn.com/en-us/news/world/one-of-science-s-biggest-dinosaur-debates-may-finally-be-settled/ar-AA1PvttY?ocid=hpmsn&cvid=6904de58713a4fa5aca269a56dd9bb74&ei=71