A new study published this week has challenged decades of assumptions about Tyrannosaurus rex, one of the most iconic dinosaur species. The research calls into question whether some T. rex fossils previously believed to be juveniles may actually belong to a smaller relative species named Nanotyrannus.
Key Findings Point to Existence of Distinct Nanotyrannus Species
The study, published in the journal Evolution, analyzed growth patterns in several T. rex and Nanotyrannus specimens. The analysis suggests that Nanotyrannus displays a very different growth trajectory and rate compared to juvenile T. rex fossils.
This implies that Nanotyrannus may be a distinct species in its own right, rather than simply younger versions of T. rex.
“The marked differences in bone tissue structure between the smallest and largest specimens attributed to T. rex make it very unlikely that they belong to the same species,” said lead researcher Dr. Holly Woodward of Oklahoma State University.
Key differences between Nanotyrannus and T. rex:
| Nanotyrannus | T. rex |
|---|---|
| Smaller size, estimated 12-15 feet long | Much larger size, up to 40 feet long |
| More slender build | More robust, heavyset build |
| Faster growth rate | Slower growth rate |
| Unique skull features | Distinctive broad and deep skull |
If confirmed, the findings could reshape scientific understanding of the tyrannosaur family tree. They would also cast doubt on the hypothesis that T. rex rapidly transformed in size and bulk as it matured.
Reaction from Experts: Vindication or Premature?
Other paleontologists have responded with a mixture of excitement and skepticism to the new findings.
“This analysis provides the best evidence yet for Nanotyrannus being a valid genus,” said Dr. Thomas Carr of Carthage College, who has argued for years that Nanotyrannus deserves its own classification.
“If these specimens were simply juvenile T. rex, we would expect to see a steady, gradual growth curve between the smallest and largest fossils attributed to T. rex. But we don’t see that at all,” Carr added.
However, some experts believe more proof is still needed before splitting Nanotyrannus off from T. rex.
“While an intriguing idea, these findings alone do not definitively prove Nanotyrannus was a separate animal,” cautioned Dr. Steve Brusatte of Edinburgh University. “We need more specimens and more analyses to determine if these differences hold.”
Findings Could Impact Museum Displays and Private Fossil Sales
If the distinction between T. rex and Nanotyrannus holds up, it could require natural history museums around the world to relabel some exhibits. Skeletons currently attributed to juvenile T. rex might need updated signage indicating they belong to the Nanotyrannus genus instead.
“We have a few ‘teenage’ T. rex specimens on display that may now need reclassifying,” said Dr. Emma Schachner, a curator at the American Museum of Natural History. “Pending further analysis, we may need to note these smaller tyrannosaurs are now considered Nanotyrannus.”
The findings could also impact the monetary value of any Nanotyrannus fossils sold at auction to private collectors. A nearly complete Nanotyrannus skeleton is currently up for sale for $20 million. If confirmed as a distinct genus, its market value could increase substantially.
“This new evidence for Nanotyrannus being its own animal is sure to generate more buzz and bidding interest,” said private fossil dealer Julius Csotonyi. “It essentially creates a new species for collectors to own.”
Unresolved Questions: Growth Rates and Evolutionary Impacts
While the current study advances the case for Nanotyrannus, many questions remain unsettled in the debate between the competing hypotheses.
One open area of research is mapping out complete growth curves for both purported species. Learning whether T. rex growth followed an ‘S’-shaped curve typical of most dinosaurs could shed more light.
“We need to discover more fully adult T. rex specimens to trace its full growth trajectory over a lifespan,” Woodward said. Her team is currently surveying museum collections for additional fossils to analyze.
Another uncertainty is explaining how Nanotyrannus fits on the tyrannosaur family evolutionary tree. Some researchers argue it may belong to an early North American branch, while others propose Asian origins.
There are also questions around whether Nanotyrannus’ existence impacted T. rex’s dominance. Could competition with its smaller cousin have driven T. rex to evolve into a specialized mega-predator? Or did T. rex only rise to dominance once Nanotyrannus died out?
Further findings in these areas may help determine whether the field finally accepts Nanotyrannus as a valid separate genus after decades of debate. For now, the only thing certain is that our understanding of the mighty T. rex continues to evolve.
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