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New tyrannosaur bridges gap from medium to monstrous

Horse-sized dinosaur had brain, ears like its bigger relative T. rex

3:00pm, March 14, 2016
 Timurlengia euotica

IN-BETWEENER  The horse-sized tyrannosaur Timurlengia euotica, which roamed what is now Uzbekistan 90 million years ago, already had the supersenses of the giant tyrannosaurs that appeared millions of years later.   

A fossil from a new species of dinosaur is helping to bridge a crucial 20-million-year gap in tyrannosaur evolution.

The key fossil is a 90-million-year-old, grapefruit-sized partial skull from Uzbekistan’s Bissekty Formation. This tyrannosaur braincase, the first well-preserved one found from the mid-Cretaceous period, shows that, although still small, tyrannosaurs of the time already had brain and ear features of later tyrannosaurs. Researchers have dubbed the in-betweener Timurlengia euotica, meaning “well-eared.” They describe the new species in a paper to appear in the Proceedings of the National Academy of Sciences.

The braincase sheds light on a long-standing mystery: how tyrannosaurs evolved in the gap from 100 million to 80 million years ago from an “average Joe” horse-sized predator in the Early Cretaceous to the huge apex predators they became in

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