Though one of the most well-known dinosaurs, Tyrannosaurus rex is actually somewhat of a mystery, having suddenly emerged as a fearsome beast some 80 million years ago. As a 20-million-year gap in the fossil record preceded T. rex, paleontologists have known little about its evolutionary path—until now. The discovery of 90-million-year-old fossils belonging to a previously unknown relative shows T. rex likely developed brains before size, reports New Scientist. Discovered in Uzbekistan in 2012, Timurlengia euotica's large brain and ears used for balancing and hearing low-frequency sounds were "almost identical to T. rex," which also shared certain bone features, researcher Stephen Brusatte tells the BBC. Yet Timurlengia was only "the size of a horse" and weighed less than 500 pounds.
"Only after these ancestral tyrannosaurs evolved their clever brains and sharp senses did they grow into the colossal sizes of T. rex," weighing over five tons, Brusatte tells the Telegraph.Timurlengia was "evolving features that would eventually allow T. rex to become this super-dominant top-of-the-food-chain animal," he adds. "Tyrannosaurs had to get smart before they got big." Researchers still don't have a full picture of Timurlengia after uncovering 25 sections of its skeleton—they don't know the length of its arms, for example—but say the "nimble pursuit hunter" had long legs and was a fast runner. Timurlengia also had "slender, blade-like teeth suitable for slicing through meat" and "probably preyed on the various large plant-eaters, especially early duck-billed dinosaurs," an expert says. (One creature alive today has teeth like T. rex.)