T-rex's tiny ancestor could hold clue to predator's dominance, scientists say

The horse-sized primitive tyrannosaur Timurlengia euotica from the middle Cretaceous (ca. 90-92 million years ago) of Uzbekistan.

The fossils of a newly discovered, smaller ancestor of the Tyrannosaurus rex may hold clues as to why the iconic dinosaur rose to the top of the food chain, scientists say.

The comparatively tiny Timurlengia euotica — yet to receive the notoriety and catchy nickname of its larger descendant — was similar in size to a horse as opposed to the elephant-sized T-rex.
But it had already developed the large brain needed to track and devour prey.

Researchers said the previously unknown relative was just one in a long lineage of animals, but should help illustrate how small tyrannosaurids evolved to become smarter and larger over time, and eventually the undisputed top predator at the of the food chain.

"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," Steve Brusatte from the University of Edinburgh's School of GeoSciences said.

"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."

New discovery part of a missing link
The first tyrannosaurs appeared about 170 million years ago and was about the size of a human.
Until now, researchers had little evidence of how the iconic predator grew to become one of the largest carnivores to ever roam the Earth before dinosaurs became extinct 65 million years ago.

The bones of the Timurlengia euotica were uncovered in Uzbekistan, where it lived about 90 million years ago.

By the Late Cretaceous Period, between 66 and 80 million years ago, the Tyrannosaurus rex was the king of the big lizards, weighing up to seven tonnes.

But a study published in the Proceedings of the National Academy of Sciences said little had been known about how the T-rex got so big, "largely because of a frustrating 20-plus-million-year gap in the mid-Cretaceous fossil record, when tyrannosauruses transitioned from small-bodied hunters to gigantic apex predators but from which no diagnostic specimens are known."

The new discovery is "the first distinct tyrannosauroid species from this gap".

The specimen was discovered between 1997 and 2006 by a team of palaeontologists, led by researchers at the University of Edinburgh, working in the Kyzylkum Desert in northern Uzbekistan.
"The early evolution of many groups like tyrannosaurs took place in the coastal plains of central Asia in the mid-Cretaceous," Professor Alexander Averianov of Saint Petersburg State University said.

Timurlengia's skull was much smaller than that of the T-rex, suggesting it didn't grow as large, but its skull shape reveals "that its brain and senses were already highly developed," the report said.

"Timurlengia was a nimble pursuit hunter with slender, blade-like teeth suitable for slicing through meat," said professor Hans Sues of the National Museum of Natural History in Washington.

"It probably preyed on the various large plant-eaters, especially early duck-billed dinosaurs, which shared its world."