How fast did dinosaurs grow, and how long did they live?

Until recently, paleontologists could only guess the maturity rate and lifespan of dinosaurs. Recent research involving microscopic analyses of the cellular structure of dinosaur bone has revolutionized our answers to these mysteries. Dinosaur bones contain growth rings, somewhat like the rings in tree trunks, which reveal yearly periods of rapid and slow growth. These studies, done in conjunction with paleontologists at AMNH, document that that Tyrannosaurus, which attained a weight of more than 10,000 pounds as an adult, reached sexual maturity at about 20 years of age and lived for up to 28 years.