**FILE** Bill Simpson, collections manager of fossil vertebrates at Chicago's Field Museum, dusts the teeth of the Tyrannosaurus rex skeleton known as "Sue" on display at the museum on May 12, 2010. (Associated Press)
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**FILE** Bill Simpson, collections manager of fossil vertebrates at Chicago's Field Museum, dusts the teeth of the Tyrannosaurus rex skeleton known as "Sue" on display at the museum on May 12, 2010. (Associated Press)
