The debate over ancient dinosaurs has gained new momentum following the results of a new study suggesting that miniature versions of the famous Tyrannosaurus rex may actually be a distinct species.
Researchers from the University of Bath and the University of Chicago have taken a new look at young T. rexes fossils and concluded that what were previously thought to be young versions of well-known dinosaurs are likely to be similar but separate species.
The study, published in the journal Fossil Studies, looked at the growth rings of tiny T. rex fossils, found evidence that bone growth rates were slowing, and suggested that Nanotyrannus versions of the famous dinosaur were likely almost full size.
“If these T. rex creatures were small, they should grow like crazy, gaining hundreds of kilograms a year, but we don't see that,” said Dr. Nick Longrich, co-author of the study, in a report published in the journal. New Atlas. “We tried modeling the data in many different ways and kept getting low growth rates.”
The findings contradict a 2020 study by researchers at Oklahoma State University, which concluded that at the time of death, the young T. rex was likely only 13 to 15 years old and had not yet reached its full developmental potential.
However, the new study modeled the likely growth rate of smaller T. rex bones, estimating that they would have grown to a maximum of between 1,984 and 3,307 pounds, only about 15% of the size of an adult T. rex.
The researchers also found that Nanotyranus fossils had more than 150 different features from their dinosaur counterparts, including a narrow snout and longer arms.
“The arms are actually longer than those of a T. rex,” Longrich said. “Even the largest Tyrannosaurus had shorter arms and smaller claws than those of the tiny Nanotyrannosaurus. This was an animal where the arms were actually very formidable weapons. It's really just a completely different animal – small, fast and agile. Tyrannosaurus rex relied on size and strength, But this animal relied on speed.”
The researchers also stress that there has been a lack of fossil discoveries that share features from both Nanotyrannus and Tyrannosaurus, which should begin to blend features as the younger version of the famous dinosaur ages if it is the same species.
Instead, researchers claim that the ancient fossil once thought to be Nanotyrannus was found to be that of a young tyrannosaur after re-examination of its skull measurements, while it also had features similar to those of larger species.
However, the new research has not convinced all scientists that the smaller fossils belong to a different species.
“I have no problem with Nanotyrannus being a real thing if science shows it is,” Holly Woodward, author of the 2020 Oklahoma State study, said in an interview with New Scientist. “I am not convinced that their interpretation is more accurate than ours.”
However, others welcomed the new perspective, describing themselves as scholars at the College of Charleston “Dinosaur Obsessed” Scott Persons Telling New Scientist about the findings should broaden the debate.
“This new paper won't resolve the controversy, but I'm optimistic that this paper will shake things up,” Pearsons said.
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