Hans-Dieter Sues, chair of the Department of Paleobiology at the Smithsonian's National Museum of Natural History, holds a vertebra fossil from a new dinosaur, Timurlengia euotica, during a news conference in Washington, Monday, March 14, 2016. The image in the background is of the braincase of the Timurlengia euotica. (AP Photo/Susan Walsh)
Where did T. rex come from? Fossil provides a clue
March 18, 2016
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How did evolution produce a monstrous killer like T. rex? A fossil find in Central Asia is giving scientists a glimpse of the process.
T. rex and other tyrannosaurs were huge and dominant predators. But they evolved from much smaller ancestors. The new discovery is from Uzbekistan. It shows that this supersizing happened quickly. It was only after the appearance of some anatomical features. They may have helped the monster tyrannosaurs hunt so effectively.
The finding was reported by Hans-Dieter Sues of the Smithsonian's National Museum of Natural History in Washington. Stephen Brusatte of the University of Edinburgh in Scotland and others worked on the study as well. They wrote a paper that was released by the Proceedings of the National Academy of Sciences.
They report finding bones of a previously unknown member of the evolutionary branch that led to the huge tyrannosaurs. This earlier dinosaur lived about 90 million years ago. It lived south of what is now the Aral Sea. It looked roughly like a T. rex. But it was only about 10 to 12 feet long. It weighed only about 600 pounds at most, Sues said. T. rex grew about four times as long and weighed more than 20 times as much.
The discovery helps fill in a frustrating gap in the tyrannosaur fossil record. Before that gap, which began some 100 million years ago, the ancestral creatures were only about as big as a horse. Right after the gap, at about 80 million years ago, tyrannosaurs were multi-ton behemoths like T. rex. The new finding shows the forerunners were still fairly small even just 90 million years ago. So the size boom happened pretty quickly.
The inner ears of the newfound beast already had tyrannosaur features. Those were associated with good agility. They could hear low-pitched sounds. The features might have helped it detect prey or other animals at a distance. But the creature lacked massive, bone-snapping teeth and large sinuses. Those were found in T. rex.
The creature was dubbed Timurlengia euotica. The name is pronounced TEE-mer-len-GEE-uh yoo-OH-tih-kuh. The name honors the ancient Central Asian ruler Tamerlane and the large inner ears of the beast. The fossils include a braincase. In addition, there are bones from the neck, back, tail, feet and hands. The creature wasn't a direct ancestor of T. rex. But it indicates what such ancestors looked like, Brusatte said.
The discovery helps scientists. They can better understand how "the (anatomical) parts got put together ... on the path to T-rex-hood." This is according to Thomas R. Holtz, Jr. He is with the University of Maryland's Department of Geology. Holtz didn't participate in the study. He said the study suggests where to dig for more fossils to investigate the transition.
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CRITICAL THINKING QUESTION
Why did huge dinosaurs evolve from smaller ancestors?
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