The Smithsonian's National Museum of Natural History revealed a newly discovered dinosaur species Monday — one that shows how the Tyrannosaurus rex evolved to become a top predator.
The new species, Timurlengia euotica, lived 90 million years ago and was about the size of a horse, scientists said Monday. Weighing up to 600 pounds, the Timurlengia is a member of the tyrannosaur family, but not an ancestor of the T. rex, scientists said.
"It had long legs and was likely a fast runner," said a release from the Smithsonian on Monday.
"Timurlengia was a nimble pursuit hunter with slender, blade-like teeth suitable for slicing through meat," said Hans Sues, chair of the Department of Paleobiology at the Smithsonian's National Museum of Natural History, in a news release.
But at that size, there's still a big difference between the Timurlengia and the T. rex, which could have weighed up to 7 tons.
Fossils of the species were discovered in Uzbekistan between 1997 and 2006. Only once scientists began studying the remains did they realize they had an entirely new species on their hands.
The remains fill in a major gap in the evolution of tyrannosaurs, the family of dinosaurs to which the T. rex belongs. The fossils show how tyrannosaurs evolved from smaller-bodied creatures into massive predators, according to a new study published in the Proceedings of the National Academy of Sciences.
"The ancestors of T. rex would have looked a whole lot like Timurlengia, a horse-sized hunter with a big brain and keen hearing that would put us to shame," said paleontologist Steve Brusatte in the Smithsonian's release. "Only after these ancestral tyrannosaurs evolved their clever brains and sharp senses did they grow into the colossal sizes of T. rex. Tyrannosaurs had to get smart before they got big."
Paleontologists have long known that this transition took place over about 70 million years — but the new fossils suggest that most of it occurred suddenly, toward the end of that period.
The study also shows that before even before tyrannosaurs grew larger, they'd already developed "keen senses and cognitive abilities, including the ability to hear low-frequency sounds," according to a release from the museum.
Sues said they probably preyed on large plant-eaters, especially early duck-billed dinosaurs.
"Clues from the life of Timurlengia allow us to fill in gaps and better understand the life and evolution of other related dinosaurs, like T. rex," he said.
The fossils at the center of the study were collected by Sues and Alexander Averianov, a senior scientist at the Russian Academy of Sciences, in the Kyzylkum Desert.
As they were studying the fossils, Sues and a team of paleontologists led by Steve Brusatte at the University of Edinburgh discovered they were from a previously unknown species. The team later reconstructed the Timurlengia's brain using CT scans of its brain case. While its skull was much smaller than the T. rex's, scientists say key features of the skull show the Timurlengia's brain and senses were already highly developed.