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October 5, 2009

T. rex's Cousin

For paleontology right now, Asia is the place to be. A few days ago, I wrote about Raptorex, the miniature tyrannosaur. Now, not far away, in Mongolia, another tyrannosaur has been added to the family tree: Alioramus altai. Specimens of this creature that had been found previously were very poorly preserved, and it was difficult to tell if Alioramus was even a tyrannosaurid at all. The newest specimen is extremely well-preserved, shedding light on the nature of this dinosaur. It also throws another wrench into what we know about the tyrannosaurs.

Tyrannosaurus rex, and its close cousin Tabrosaurus, are known for enormous bulk. They look the part of the ferocious carnivore. Most striking are the gargantuan heads, with banana-sized, serrated teeth and a powerful bite. Alioramus has a very different body type. In fact, Stephen Bursette, a graduate student associated with the project, described it as being "like a ballerina," in comparison to other tyrannosaurs. It is half the size of Tabrosaurus, probably weighing only 810 pounds. Its skull is what truly sets it apart, however. Alioramus has a slender, gracile skull, with a long snout and eight horns. Horns have never been found on tyrannosaurs before, so this is a bizarre feature. Yet, looking at the brain case, Alioramus has all the hallmarks of a tyrannosaur: large air sacks, a great sense of smell, and a small inner ear.

One final feature that makes this discovery so interesting is that Alioramus was found in a quarry with a Tabrosaurus. Obviously, they must have shared some of their range. Perhaps Alioramus and Tabrosaurus had a similar relationship to that of lions and cheetahs today. Both are large cats, but they hunt in different ways and don't often interfere with each other.

The discovery of Alioramus completely changes what we know about tyrannosaurs. Between it and Raptorex, scientists are rethinking this branch of dinosaur entirely. T. rex and its relatives are interesting; there has been a lot of research done on them. Many paleontologists believed we even understood tyrannosaurs. These new discoveries go to show that nothing in science is absolutely determined; just when we think we know it all, something new pops up that makes us take another look.

Credit: Science Daily-Bizarre New Horned Tyrannosaur From Asia: Carnivorous But Smaller T. Rex Relative  'Like Ballerina'