A surprisingly smart tyrannosaur has been uncovered — and this dinosaur may have hunted smarter, not harder, evidence suggests. Once thought to have grown large while acquiring intelligence, this new specimen suggests something new: tyrannosaurs didn't have to be big to be smart.
The new tyrannosaur is named Timurlengia euotica. It was about the size of a horse and weighed up to 550 lbs, according to a study published today in Proceedings of the National Academy of Sciences. But being smaller than a Tyrannosaurus rex, for instance, did not prevent it from having a big brain and great hearing, researchers say. That's important because it means that smarts, rather than size, may have first helped tyrannosaurs rise to the top of the food chain. The Timurlengia's bones also indicate that it lived about 90 million years ago. If that's right, this is the first species that could be used to explain how tyrannosaurs evolved during a 20-million-year gap in their fossil record.
"Tyrannosaurs got smart before they got big."
Before this discovery, "the prevailing idea was that the sophisticated senses and large body sizes evolved together, part of the same package deal" says Stephen Brusatte, an paleontologist at the University of Edinburgh who co-authored the study. But the Timurlengia's anatomy "tells us that tyrannosaurs got smart before they got big."
The first tyrannosaurs weren't impressive. When they appeared around 170 million years ago, they were human-sized. Fast forward 100 million years, and the T. rex is a top predator. Exactly how that jump happened — from human-sized carnivore to top dog — hasn't been clear. So far, scientists have identified about 20 species of tyrannosaurs, but none of those species fit into the middle part of the Cretaceous, the part of the fossil record that spans from 100 million years ago to 80 million years ago. That's why today's dinosaur discovery is so exciting; this is the first time that scientists have been given a glimpse of the evolutionary changes that occurred in the period before the T. rex made its debut.
"We realized it was a new species pretty quickly after looking at it."
The remains of a Timurlengia were discovered in the Kyzylkum Desert in northern Uzbekistan between 1997 and 2006. Scientists knew early on that they had something special on their hands. "We realized it was a new species pretty quickly after looking at it," Brusatte says. Even though the dinosaurs' bones were clearly tyrannosaur-like, certain features were unusual. For instance, the dinosaur's skull was a lot smaller than the T. rex, but its inner ear was larger and more robust than that of all the other dinosaurs at the time, Brusatte says. Because the inner ear plays a role in maintaining balance, it's possible Timurlengia was more agile than its prey and competitors.
The Timurlengia probably also had great hearing, with an increased sensitivity for lower-frequency sounds, researchers say. (Because of this, the researchers named it "euotica," which means "well-eared" in Latin.) Combined with the tyrannosaur's blade-shaped teeth, sharp senses would have helped it hunt the many duck-billed, plant-eating dinosaurs that lived in the same environment, Brusatte says. "Timurlengia would have been a smart, agile, fast-running hunter."
(Steve Brusatte, Todd Marshall)
"A time where tyrannosaur remains are virtually unknown."
"This is a very exciting report that provides a rare insight into the interval of time where tyrannosaur remains are virtually unknown," says Rich Crea, a curator at the Peace Region Palaeontology Research Centre in British Columbia who didn't work on the study. "It gives an important perspective on the evolution of tyrannosaurs before they adapted into the large, apex predators of the Late Cretaceous, culminating in the best known tyrannosaur — that is to say Tyrannosaurus rex."
Being able to fill the 20 million year gap with a first species is "very exciting," Brusatte says. But given how big that gap is, the dinosaur's discovery really only represents one data point. That's why Brusatte hopes to find more tyrannosaur fossils that can fit into that period. He would also like to study other tyrannosaurs to learn about how their brains and sense organs changed throughout evolution. "We're working on CT scans of another tyrannosaur in my lab right now," he says.
Still, the Timurlengia's discovery is an important first step, and that's something worth celebrating, Brusatte says. "Like a detective investigating a murder scene, one clue is better than no clues."
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