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. 

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 predator 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. 

The species' skull was much smaller than  smaller than that of T.rex. However, key features of Timurlengia's skull reveal that its brian and senses were already highly developed. Timurlengia was about the size of a horse and could weigh uo to 600 pounds. It had long legs and was likely a fast runner. 

The first tyrannosaurs lived during the Jurassic Period, around 170 million yeras 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 Commision The fieldwork was supported by the Natioanal Science Foundation and the National Geographic Society. The work was carried out in collaboration with researcheers at the University of Edinburgh, Russian Academy of Sciences and Saint Petersburg State University.