This study explains why T. rex remains king of dinosaurs

According to a new study, the remains of a new species of horse-sized dinosaur have revealed that how Tyrannosaurus rex was one of Earth's top predators.

The university of Edinburgh researchers have found that the dinosaurs, known as tyrannosaurs, developed huge body sizes rapidly right at the end of the age of dinosaurs, and that their keen senses, which evolved earlier in much smaller species, enabled them to climb to the top of the prehistoric food chain.

Dr Steve Brusatte, of the University of Edinburgh's School of GeoSciences, who led the study, said that 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. 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."

A team of palaeontologists, led by researchers at the University of Edinburgh, studied a collection of tyrannosaur fossils found in the Kyzylkum Desert, northern Uzbekistan.

They found that the species' skull was much smaller than that of T. rex, indicating that it did not grow to the same enormous size. 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 250kg. It had long legs and a skull studded with sharp teeth, and was likely a fast runner, researchers say.

Professor Hans Sues, of the National Museum of Natural History, Smithsonian Institution, said that Timurlengia was a nimble pursuit hunter with slender, blade-like teeth suitable for slicing through meat. It probably preyed on the various large plant-eaters, especially early duck-billed dinosaurs, which shared its world.

The study is published in the journal of Proceedings of the National Academy of Sciences.