Reconstruction of Tyrannosaurus macraiensis.Credit: Sergei Krasinski, editor
A re-study of fossils collected in New Mexico has unearthed important clues about the origins of Tyrannosaurus rex in North America.
New research published in scientific report Reshaping our understanding of how the most famous dinosaurs of all time roamed the Earth. tyrannosaurus rex – First reached North America by introducing its first known relative to the continent.
This study identified a newly discovered Tyrannosaurus subspecies. Tyrannosaurus macraiensis. The newly discovered predator is older and more primitive than its better-known cousin, but it’s about the same size, about the size of a double-decker bus.
Discoveries from New Mexico
The study is based on a partial skull collected in western New Mexico several years ago and now on display at the New Mexico Museum of Natural History and Science (NMMNHS), which indicates that Tyrannosaurus rex was the first dinosaur paleontologists ever thought possible. This indicates that they existed in North America millions of years ago.
Contributors to the study include researchers from the University of Bath (UK), NMMNHS, University of Utah, George Washington University, Harrisburg University, Lehigh Valley University of Pennsylvania, and the University of Alberta.
“New Mexicans always knew our state was special, but now we know New Mexico has been a special place for tens of millions of years,” said NMMNHS Executive Director. Dr. Fiorillo said. “This research fulfills the museum’s mission by providing a science-based exploration of the history of life on Earth.”
![Teeth of Tyrannosaurus macraiensis](https://scitechdaily.com/images/Tyrannosaurus-mcraeensis-Teeth-768x1024.jpg)
Teeth of Tyrannosaurus macraiensis.Credit: Nick Longrich
Rethinking the evolutionary journey of Tyrannosaurus
Perhaps the largest and most dangerous land predator of all time, Tyrannosaurus rex suddenly appeared in North America about 66 million years ago. However, there are no closely related species in North America, and how it arrived on the continent and evolved remains a mystery.
When then-student Sébastien Dalman began re-studying horned dinosaurs from the same fauna, it forced a broader rethinking of the dinosaurs of western New Mexico.
“I started working on this project with co-author Steve Jasinski in 2013, and soon began to suspect that we were embarking on something new,” Dallman said.
reveal subtle differences
A team of scientists from Bath (UK), the United States and Canada were assembled to study this animal, examining the skeleton bone by bone. In each case, they found subtle differences between the specimen and dozens of specimens. tyrannosaurus Human bones previously discovered.
because tyrannosaurus is so well known that it became possible to show that the New Mexico Tyrannosaurus rex was something new.
“The differences are subtle, but they usually are for closely related things.” seed. “Evolution slowly accumulates mutations over millions of years, causing subtle changes in the appearance of species over time,” said co-author Dr Nick Longlich from the Milner Center for Evolution at the University of Bath.
![Tyrannosaurus macraiensis jaw](https://scitechdaily.com/images/Tyrannosaurus-mcraeensis-Jaw-777x518.jpg)
The jaw of Tyrannosaurus macraiensis at the New Mexico Museum of Natural History and Science. Notice the large scar behind his chin. The authors speculate that this may have resulted from a battle with another tyrannosaur.Credit: Nick Longrich
Tyrannosaurus macraiensis: New species
newly discovered Tyrannosaurus macraiensis It was almost the same size as tyrannosaurus, measured up to 40 feet (12 meters) long and 12 feet (3.6 meters) high. Like a famous relative, Tyrannosaurus macraiensis I ate meat. New discoveries have been made for a long time, but tyrannosaurusThe paper notes that subtle differences in the jawbone make it unlikely to be a direct ancestor.
This raises the possibility that new discoveries of Tyrannosaurus will continue in the future.
“The scope and scientific importance of New Mexico’s dinosaur fossils is once again evident. Many new dinosaur species remain to be discovered in New Mexico, both in rocks and in museum drawers.” Dr. Spencer Lucas, curator of paleontology at NMMNHS, said:
Expand your understanding of Tyrannosaurus
This new discovery expands our understanding of Tyrannosaurus in several ways. First, they suggest that apex predators lived in what is now the southern United States at least 72 million years ago, long before the first fossils were discovered. tyrannosaurus Found in the same area.
Tyrannosaurus rex probably originated in southern North America and later spread to much of the western part of the continent.
These new fossils, collected on land managed by the U.S. Bureau of Reclamation, were larger, more massive, and more advanced than the small, primitive tyrannosaurs that lived in Montana and Canada. This suggests that a similar species evolved in the southern United States. .
![Kettletop Butte in southeastern New Mexico](https://scitechdaily.com/images/Kettle-Top-Butte-in-Southeastern-New-Mexico-777x583.jpg)
Kettle Top Butte in southeastern New Mexico. This fossilized jaw of Tyrannosaurus macraensis was discovered near the base of a butte. Credit: Dr. Spencer Lucas, New Mexico Museum of Natural History and Science.Credit NM Cultural Affairs Bureau
Conclusion: Unraveling the evolution of dinosaurs
For reasons not yet understood, dinosaurs may have evolved larger sizes in the south, with body size patterns that are the opposite of those seen in modern mammals.
And towards the end, Cretaceous period Then, for reasons unknown, giant tyrannosaurs suddenly spread north, alongside giant horned dinosaurs like Triceratops and Torosaurus. The northward spread of giant-horned dinosaurs may have created a food source that could feed giant tyrannosaurs.
It’s been over a century since Tyrannosaurus was first discovered, but there’s still a lot we don’t know.
Reference: “Giant tyrannosaurs of the Campanian-Maastrichtian of southern North America and the evolution of gigantism in tyrannosaurids” Sebastian G. Dalman, Mark A. Loewen, R. Alexander Pyron, Stephen E. Jasinski , D. Edward Marinczak, Spencer G. Lucas, Anthony R. Fiorillo, Philip J. Currie, Nicholas R. Longrich, January 11, 2024, scientific report.
DOI: 10.1038/s41598-023-47011-0