Fossils likely a different dino species, study says
Dinosaurs haven’t roamed the Earth for millions of years, but the nature of their reign has sparked no shortage of controversial debates among paleontologists that remain unresolved today.
Last week, researchers breathed new life into one longstanding sticking point: Are a set of smaller fossils recovered long ago those of a juvenile Tyrannosaurus-Rex – or evidence of another species altogether?
Authors of a new study published Wednesday in the journal Fossil Studies claim the fossils belong to a species known as a Nanotyrannus lancensis.
“I was very skeptical about Nanotyrannus myself until about six years ago when I took a close look at the fossils and was surprised to realize we’d gotten it wrong all these years,” said lead author Nicholas Longrich, a paleontologist and senior lecturer at the University of Bath in the U.K.
“When I saw these results I was pretty blown away.”
Anyone who has seen “Jurassic Park” is familiar with the size and ferocity of the popular T-Rex, one of the world’s most famous and widely studied dinosaurs. But was TyrannosaurusRex the only large carnivore ruling over North America during the Late Cretaceous period?
Longrich and Evan Saitta, a paleontologist at the University of Chicago and research associate at Chicago’s Field Museum of Natural History, teamed up to take another look at the fossils in question. Their findings suggest that the growth patterns and anatomy are inconsistent with those of a TRex and instead constitute its distant relative.
By measuring growth rings on the fossils, the researchers found that they were closely clustered toward the outside of the bone. The discovery, they claimed, could be an indication that the dinosaur had reached close to its full size and was not an adolescent when it died.
Based on the researchers’ measurements, the animals would have reached a maximum size that was only about 15% that of the giant T-Rex, weighing no more than 3,300 pounds and standing 16 feet tall. In comparison, an adult T-Rex could weigh up to 17,600 pounds and towered 30 feet above the ground.
And the two species may not have just differed in size. The researchers reconstructed the dinosaur’s anatomy and posited that the smaller animal tended to have a narrower snout, smoother teeth, longer legs and larger arms.
The newest piece of evidence Longrich unearthed was a fossil frontal bone gathering dust at the University of California Museum of Paleontology. After examining it closer, the researchers identified it as a juvenile T-Rex because of critical differences between it and the hypothesized Nanotyrannus fossils.
“In the same way that kittens look like cats and puppies look like dogs, the juveniles of different tyrannosaurs are distinctive,” Longrich said. “And Nanotyrannus just doesn’t look anything like a T-Rex.”
The researchers’ conclusions are unlikely to end the debate over the disputed existence of the Nanotyrannus.