Fossils two dinosaurs locked in battle have unleashed new drama by suggesting that diminutive specimens thought to be juvenile Tyrannosaurus rex may instead be a separate, smaller species.
The “fighting dinosaurs” fossil, depicting a Triceratops fighting a medium-sized Tyrannosaurus rex, was discovered in Montana by commercial fossil hunters in 2006 and dates to just before the asteroid impact that ended the reign of the dinosaurs 66 million years ago.
It became available for scientific research only after it was purchased North Carolina Museum of Natural Sciences (NCMNS) in recent years.
Now researchers say a detailed analysis of the fighting T. rex shows that it is not a juvenile T. rex, as many thought, but an adult member of a different species. Nanotyranus lanceolata
“Our specimen represents an adult Nanotyrant weighing just 1,500 pounds after two decades of growth,” said Dr. Lindsay Zanno, co-author of the study from North Carolina State University and director of paleontology at NCMNS.
“Anatomy Nanotyrant“Due to more teeth, enlarged arms, a shorter tail, a unique pattern of cranial nerves and sinuses, and a smaller adult body size, it is inconsistent with the hypothesis that this skeleton is an adolescent T. rex,” Zanno said.
Name Nanotyranus lanceolata was previously given to a small skull reported from the Hell Creek Formation of Montana in 1946. However, experts later argued that the specimen, known as the Cleveland skull, was actually a juvenile Tyrannosaurus rex..
Now a study by Zanno and his colleagues, published in the journal Naturereveals Nanotyranus lanceolata really was an independent species that lived simultaneously and lived in the same ecosystems as the Tyrannosaurus rex.
Moreover, the team claims that the skeleton of a juvenile dinosaur named Jane, found in the Hell Creek Formation in 2001, is also not a juvenile T. rex, but a new species. Nanotyrant.
“Our research shows that some specimens previously thought to represent juvenile Tyrannosaurus rex. instead Nanotyrant– said Zanno.
She said the results have important implications. “For decades, paleontologists have unknowingly used Nanotyrant specimens as a model for a juvenile Tyrannosaurus rex to understand the biology of Earth's most famous dinosaur – studying its movement, growth, feeding and life history. These studies require a second look,” she said.
Professor Steve Brusatte of the University of Edinburgh, who was not involved in the work, said that for many years in his research on tyrannosaurs he had considered a collection of smaller skeletons found in the same rocks as the tyrannosaur fossils to be juvenile tyrannosaurs.
“I think new data from this exquisite new specimen at the North Carolina Museum of Natural Science shows that I was wrong—at least in part,” he said, adding that the analysis of the fighting T. rex provided “strong evidence.” Nanotyrant was real.
But Brusatte said he's not sure there are multiple species Nanotyrantalthough he also noted that the number of fossilized adults of Tyrannosaurus that have been excavated suggests that fossilized juveniles must also exist.
“So I'm not yet ready to announce every smaller Tyrannosaurus rex skeleton Nanotyrant” he said. “Some of them must be young Treksiks, and I think it will eventually be very difficult to distinguish the adults from the almost adults.” Nanotyrant from teenage tyrannosaurus.»
