News Releases

Newly Discovered Dinosaur Reveals How T. rex Became King of the Cretaceous

March 14, 2016

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.

Paleontologists have long known from the fossil record that the family of dinosaurs at the center of the study—tyrannosaurs—transitioned from small-bodied species to fearsome giants like the T. rex over the course of 70 million years. But now, newly discovered dinosaur fossils suggest that much of this transition and growth in size occurred suddenly, toward the end of this 70 million-year period. The study also shows that before the evolution of their massive size, tyrannosaurs had developed keen senses and cognitive abilities, including the ability to hear low-frequency sounds. This positioned them to take advantage of opportunities to reach the top of their food chain in the Late Cretaceous Period after other groups of large meat-eating dinosaurs had gone extinct about 80–90 million years ago.

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.

Timurlengia was a nimble pursuit hunter with slender, blade-like teeth suitable for slicing through meat,” said Hans Sues, chair of the Department of Paleobiology at the Smithsonian’s National Museum of Natural History. “It probably preyed on the various large plant-eaters, especially early duck-billed dinosaurs, which shared its world. Clues from the life of Timurlengia allow us to fill in gaps and better understand the life and evolution of other related dinosaurs, like T. rex.”

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.”

Sues and a team of paleontologists led by Steve Brusatte at the University of Edinburgh studied tyrannosaur fossils collected from the international expedition and discovered the new species. The team later reconstructed the brain of the dinosaur using CT scans of its brain case to glean insights into the new species’ advanced senses.

“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.

The new study was funded by the European Commission. The fieldwork was supported by the National Science Foundation and the National Geographic Society. The work was carried out in collaboration with researchers at the University of Edinburgh, Russian Academy of Sciences and Saint Petersburg State University.

# # #

SI-125-2016

Artists rendering of new dinosaur (detail)

Media only   
Ryan Lavery  
(202) 633-2950 
laveryr@si.edu

Randall Kremer  
(202) 633-2950 
kremerr@si.edu

Related photos: 

Dinosaur Discovery: Dzharakuduk

Map

Illustration adapted and modified from http://en.wikipedia.org/wiki/Uzbekistan

Position of Dzharakuduk (marked by red star) on a map of Uzbekistan where the fossilized remains of Timurlengia eutica were discovered.

Related photos: 

Dinosaur Discovery: Family Tree

diagram

© Proceedings of the National Academy Sciences

Family tree showing the interrelationships of most known species of tyrannosaurs. Geological stages and ages (in million years) at the bottom. The new tyrannosaur Timurlengia euotica is highlighted in red.

Related photos: 

Dinosaur Discovery: Field camp

Field camp seen from a distance

Igor Danilov

Field camp of the Uzbek-Russian-British-American-Canadian expedition at Dzharakuduk in the Kyzylkum Desert of Uzbekistan. The fossils of Timurlengia eutica were found about midway along the cliffs in the background.

Related photos: 

Dinosaur Discovery: Fossilized Tooth

Tooth

James Di Loreto / Smithsonian

A fossilized tooth of the new tyrannosaur Timurlengia euotica from the Late Cretaceous Period that was found in the Kyzylkum Desert, Uzbekistan.

Related photos: 

Dinosaur Discovery: Fossilized tooth

Fossil tooth

James Di Loreto / Smithsonian

A fossilized tooth of the new tyrannosaur Timurlengia euotica from the Late Cretaceous Period that was found in the Kyzylkum Desert, Uzbekistan.

Related photos: 

Dinosaur Discovery: Hans Sues

Hans Sues

Hans Sues / Smithsonian

Hans Sues, a scientist at the Smithsonian’s National Museum of Natural History, excavating a dinosaur fossil at Dzharakuduk in the Kyzylkum Desert of Uzbekistan, September 2006.

Related photos: 

Dinosaur Discovery: Hans Sues (vertical)

Hans Sues with dinosaur teeth

James Di Loreto / Smithsonian

Hans Sues, Chair, Department of Paleobiology, National Museum of Natural History, Smithsonian Institution holding a cast (right hand) of a Tyrannosaurus Rex tooth for comparison with an actual tooth of the new tyrannosaur Timurlengia euotica, from the Late Cretaceous Period that was

Related photos: 

Dinosaur Discovery: Timurlengia euotica

Painting of newly discovered dinosaur

Todd Marshall

Life reconstruction of the new tyrannosaur Timurlengia euotica in its environment 90 million years ago. It is accompanied by two flying reptiles (Azhdarcho longicollis).

Related photos: 

Dinosaur Discovery: Timurlengia euotica

Diagram of skeleton

© Proceedings of the National Academy of Sciences

Reconstructed skeleton of Timurlengia euotica with discovered fossilized bones, highlighted in red, and other bones remaining to be discovered inferred from other related species of tyrannosaurs in white. Individual scale bars for the pictured fossilized bones each equal 2 cm. The fossilized

Related photos: 

Dinosaur Discovery: Timurlengia euotica

Diagram of braincase

© Proceedings of the National Academy of Sciences

Top row: Partial braincase of Timurlengia euotica in tree views (L to R: from the back, from below, and from the right side). Bottom row: Composite images of the brain case from CT scanning. Reconstructed brain in dark blue, inner ear in pink, nerves in yellow, and blood vessel in red.



DCSIMG