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Fossils unearthed in northern Uzbekistan's remote Kyzylkum Desert of a smaller, older cousin of Tyrannosaurus rex are showing that the modest forerunners of that famous brute had already acquired the sophisticated brain and senses that helped make it such a horrifying predator.
Researchers said on Monday the horse-sized Cretaceous Period dinosaur, named Timurlengia euotica, that roamed Central Asia 90 million years ago sheds new light on the lineage called tyrannosaurs that culminated with T. rex, which stalked North America more than 20 million years later.
The researchers used CT scans to look inside Timurlengia's braincase and digitally reconstruct its brain, sinuses, nerves, blood vessels and inner ear. The make-up of the inner ear indicated Timurlengia, like T. rex, excelled at hearing lower frequency sounds.
Timurlengia was relatively small but boasted the advanced brain and senses of the colossal apex predators like Tyrannosaurus rex that lived at the end of the dinosaur age, paleontologist Steve Brusatte of Scotland's University of Edinburgh said. "This tells us that tyrannosaurs got smart before they got big."
These traits came in handy when tyrannosaurs had the opportunity to rise to the top of the food chain and become very big after other large dinosaur predator groups disappeared.
Timurlengia, named for 14th century Central Asian conqueror Tamerlane, was 10-13 feet (3-4 meters) long and about 600 pounds (270 kg). T. rex reached about 42 feet (13 meters) and 7 tons.
Paleontologist Hans-Dieter Sues of the Smithsonian Institution's National Museum of Natural History in Washington said Timurlengia was a nimble, long-legged pursuit hunter and probably a better runner than T. rex.
"Timurlengia would be a frightening creature, in the same way that a lion is pretty frightening to us," Brusatte said. "But if you were somehow transported into an alternate dimension and had a choice between facing down a Timurlengia or a T. rex, you would go with Timurlengia anytime."
Tyrannosaurs appeared about 170 million years ago and initially were roughly a person's size.
Before Timurlengia's discovery, there had been a gap in the tyrannosaur fossil record between about 100 and 80 million years ago that had left questions about their evolution. The fact Timurlengia was still relatively small 80 million years after tyrannosaurs first appeared showed their immense size occurred suddenly, late in their evolutionary history.
"Tyrannosaurs only became really big about 80 million years ago," Sues said.
The research appears in the Proceedings of the National Academy of Sciences.