Paleontologists have unearthed only a few juvenile tyrannosaurs, and a new analysis suggests why: Unlike many other creatures both modern and ancient, a large percentage of those meat-eating dinosaurs survived into adulthood.
Many dinosaur bones, including those of Tyrannosaurus rex and its relatives, show growth rings, just as trees do, says Gregory M. Erickson, a paleobiologist at Florida State University in Tallahassee. Now, he and his colleagues have counted growth rings in leg bones to determine the age distributions of four tyrannosaur species.
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