Paleontologists at the North Carolina Museum of Natural Sciences have discovered a new species of dinosaur called nanotyrannus lancensis.
The discovery came after studying a fossil called "Dueling Dinosaurs" acquired by the museum in 2022. The fossil contains two dinosaurs preserved together in a potential predator-prey encounter: a triceratops and what was originally thought to be a juvenile tyrannosaurus rex.
New evidence shows that creature was not a young T. rex, but instead a speedy and agile creature called nanotyrannus. Compared to the T. rex, the nano had bigger arms, more teeth, and a shorter tail.
"Whereas (the) T. rex was this bulky, powerful predator with strong bite forces and banana sized teeth, (the) nanotyrannus was a very lean, swift pursuit predator of small size that could have run circles around (a T. rex)," said Lindsay Zanno, head of paleontology at the Museum of Natural Sciences and associate research professor at NC State University.
Zanno and James Napoli, anatomist at Stony Brook University, co-authored a study published Thursday in the scientific journal Nature.
This discovery settles a decades long debate. As NPR reports, paleontologists had previously debated whether small-bodied tyrannosaurs were teenage T. rexes or a different species altogether.
In an interview with WUNC, Zanno explained that she and her team tested to answer this question: how old was this tyrannosaur in the "Dueling Dinosaur" fossil when it died?
" To do that, we cut thin sections of its leg bones... and we looked inside at the growth rings that are laid down in dinosaur bones each year," said Zanno. "We counted those growth rings up, just like a tree. We were able to determine through some modeling that (a nanotyrannus) would've reached its adult size at around 20 years and it would've been about 10 times smaller than a T. rex."
Zanno said she's excited about this discovery, but there's still more research to do.
"Now we can begin to ask the question of - how did nanotyrannus and teenage T. rex live together in the same ecosystem without competing?," said Zanno. "It seems like these animals had completely different predatory ecologies. In other words, they were a different flavor of predator."
Another implication of this discovery: predator diversity was higher and more robust before the asteroid impact event than previously thought.
" There's another debate about whether dinosaurs were in decline or flourishing before the end-Cretaceous impact event," said Zanno. "Tthe last days of the dinosaurs were much more colorful than we have known (about) until today."
