tyrannosaurus rex After all, it may not have been the only large carnivore that ruled North America during the Late Cretaceous. Reinterpretation of some fossils of small dinosaurs sometimes classified as young dinosaurs tyrannosaurus This adds weight to the controversial idea that it is a separate small species called . Nanotyrannus lansensislived with the dinosaur king.

“This is the most famous fossil animal in the world,” he says Nicholas Longrich At the University of Bath, UK. “A lot of people are watching. And we can't agree.”

This debate has divided paleontologists for decades. A paper from the 1960s revealed that a skull excavated 20 years earlier in the Hell Creek Formation in Montana was tyrannosaurus that died before reaching full maturity. However, in the 1980s, others argued that the differences between the skull and known skulls were: tyrannosaurus The specimen showed that this fossil was actually an adult of another species, and they named it Nanotyrannus lansensis.

Recent studies based on additional fossils dispute this, arguing that the differences between miniature and full-sized fossils are: tyrannosaurus The fossils were not of different species, but of different times. This discussion has implications for understanding the ecology and diversity of dinosaurs in the period just before their extinction.

Now, with Longrich Evan Saitta Researchers at the University of Chicago have compiled six pieces of evidence that support identifying the smaller fossils as: Nanotyrannus. This includes cataloging more than 150 individual features that differ between the fossil in question and the known fossils. tyrannosaurus Fossils include things like a narrower snout and smoother teeth. They argue that all this cannot change between boys and adults. tyrannosaurus.

The researchers also analyzed the patterns of bone growth rings, which form when bones stop growing each year. As the animal grows slower, the distance between the growth rings decreases. Researchers say they found these rings to be tightened, suggesting that the smaller fossils represent young adults. Nanotyrannus Rather than a boy tyrannosaurus They rate these adults Nanotyrannus Their weight would be between 1,000 kg and 2,000 kg, equivalent to a quarter of an adult. tyrannosaurus 8000 kg. “No matter how you graph the data, you can’t turn it into an animal. tyrannosaurus” Longrich says.

The latest evidence is a fossilized frontal bone (located between the eye and skull) that Longrich unearthed from the archives of the University of California Museum of Paleontology, which researchers interpret as a juvenile fossil. tyrannosaurus Because it is definitely different from the hypothesis, Nanotyrannus fossil. “It's an animal smaller than a human.” Nanotyrannus But it is tyrannosaurus Morphology,” Longrich says.

Some outside researchers say they remain unsure that the tiny fossil is actually a separate species. “No problem Nanotyrannus If science proves it, it’s real.” holly woodward At Oklahoma State University written Juvenile species were identified in a tree ring survey conducted in 2020. tyrannosaurus explanation. “We’re not convinced that their interpretation is any more accurate than ours,” she said, adding that the fully grown animal specimens were “unusual.” Nanotyrannus It will be necessary to resolve different interpretations.

thomas carr A professor at Carthage College in Wisconsin has long argued that the fossil is a juvenile. tyrannosaurus, adding that the front bone found at Berkeley was too incomplete to sway him. “I don’t take this seriously at all,” he says.

scott parsons Professors at the College of Charleston in South Carolina are more welcoming of what he says is a new perspective on a long-stalled rift among paleontologists. “This new paper doesn’t settle this debate, but I’m optimistic that it will be a game-changer,” he says.