Brontosaurus, Triceratops, raptor … these dinosaurs have their fans, but none is as iconic as the fearsome Tyrannosaurus rex. So when a new ancestor of the apex predator is discovered, it’s big news for the dino community, but it’s even bigger news when it solves a long-standing mystery about how the king got his crown.

A new set of fossilized bones unearthed in Uzbekistan add one more piece to the puzzle of T. Rex’s lineage, and it’s an interesting one, showing us that the “tyrant king” (that’s the Latin roots of Tyrannosaurus rex) wasn’t always the dominating giant that made our hearts race in films like "Jurassic Park." The name tyrannosaur might make us think of a 40-feet long, 13-feet tall, 8-ton colossus, but in fact tyrannosaurids spent tens of millions of years as much smaller beasts not much bigger than humans.

Some of the smaller tyrannosauroids compared to a human.Some of the smaller Tyrannosauroids compared to a human. (Photo: Conty/Wikipedia)

A 20-million-year gap in the fossil record has so far left us in the dark about how the smaller predators turned into the giant carnivore that rose to the top of the food chain during the late Cretaceous period. But the Uzbekistan discovery, particularly a piece of skull, has helped paleontologists reconstruct a tyrannosaur that is an ancestor to the T. Rex, naming it Timurlengia euotica after the historical figure Timur, a 14th-century Turco-Mongol conqueror, who created a dynasty in Central Asia.

The skeleton of Timurlengia euotica along with the bones that were discovered.The skeleton of Timurlengia euotica along with the bones that were discovered. (Photo: Todd Marshall and Steve Brusatte/PNAS)

The bones, described in a paper published by Hans-Dieter Sues and his colleagues in the Proceedings of the National Academy of Sciences, were found in 90-million-year-old rocks in the Kyzylkum desert in Central Asia. The skull fragment, which is a bit bigger than a baseball, was the key to establishing Timurlengia as a new species of tyrannosaur. It was about the size of a horse, so much smaller than T. Rex, which dominated about 70 million years ago.

This is the skull of a Tyrannosaurus rex. Doesn't he look like a "tyrant king"?This is the skull of a Tyrannosaurus rex. Doesn't he look like a 'tyrant king'? (Photo: David Monniaux/Wikipedia)

While Timurlengia was smaller and more slender than T. Rex — weighing around 550 pounds and measuring 9-10 feet long — its skull indicates that it already had some of the well-developed senses that made its larger descendent such an effective predator, such as excellent hearing and sharp eyesight. Its teeth were narrower and better shaped to slice flesh than to puncture bone.

Of particular interest to the paleontologists is the new dinosaur’s long cochlea (the snail-shaped part of the inner ear), which is almost identical to the T. Rex’s but smaller. This would have given Timurlengia the ability to detect low-frequency sounds, allowing it to better detect its prey from far away or in situations when the prey made little noise. This super-sensitive hearing likely gave it a leg up over other predators and, over time, helped it become the king of dinosaurs.

Michael Graham Richard ( @Michael_GR ) Michael writes for MNN and TreeHugger about science, space and technology and more.