Newly discovered dinosaur reveals how T. rex became king of the Cretaceous
The fossilized remains of a new horse-sized dinosaur reveal how Tyrannosaurus rex and its close relatives became top predators, according to a new study published in the Proceedings of the National Academy of Sciences.
|Life reconstruction of the new tyrannosaur Timurlengia euotica in its environment 90 million years ago |
[Credit: Todd Marshall]
Until now, little was known about how tyrannosaurs became the giant, intelligent predators that dominated the landscape about 70 to 80 million years ago. The newly discovered species, named Timurlengia euotica, lived about 90 million years ago and fills a 20 million-year gap in the fossil record of tyrannosaurs. The new species is a tyrannosaur but not the ancestor of the T. rex.
|A tyrannosaur family tree [Credit: Steve Brusatte]|
Sues and Alexander Averianov, a senior scientist at the Russian Academy of Sciences, collected the fossils at the center of the study between 1997 and 2006 while co-leading international expeditions to the Kyzylkum Desert of Uzbekistan.
"Central Asia was the place where many of the familiar groups of Cretaceous dinosaurs had their roots," Sues said. "The discoveries from the Kyzylkum Desert of Uzbekistan are now helping us to trace the early history of these animals, many of which later flourished in our own backyard in North America."
|Illustration of a Timurlengia skeleton with bones [Credit: Todd Marshall & Steve Brusatte]|
"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," Brusatte 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."
The species' skull was much smaller than that of T. rex. However, key features of Timurlengia's skull reveal that its brain and senses were already highly developed, the team says.
Timurlengia was about the size of a horse and could weigh up to 600 pounds. It had long legs and was likely a fast runner.
The first tyrannosaurs lived during the Jurassic Period, around 170 million years ago, and were only slightly larger than a human. However, by the Late Cretaceous Period--around 100 million years later--tyrannosaurs had evolved into animals like T. rex, which could weigh up to 7 tons.
The new species' small size some 80 million years after tyrannosaurs first appeared in the fossil record indicates that its huge size developed only toward the end of the group's long evolutionary history.
Source: Smithsonian [March 14, 2016]