American Museum of Natural History 📤 5 years ago 2012-07-10
Until recently, paleontologists could only guess about these questions. Because many extinct, non-avian dinosaurs, such as Tyrannosaurus and Apatosaurus, are so immense, it was generally assumed that they grew slowly and required 50-100 years to attain their great size.
But 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. By studying growth rings in Tyrannosaurus bones, scientists can estimate how fast the animal was growing at different times in its life and how old individual animals were when they died.
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. In order to obtain its immense size and weight, it could put on almost five pounds a day during its phase of maximum growth. As one might expect, these rates of relative growth are fairly similar to those found in birds, which are the closest living relatives of Tyrannosaurus.Microscopic studies of these growth rings in Apatosaurus bones suggest that this sauropod's period of fastest growth occurred between about 7 and 13 years of age, when the animal gained about 32 pounds a day - or about 6 tons a year! Although paleontologists used to think that gigantic dinosaurs lived a century or so, based on studies of living reptiles like giant tortoises, growth rings show that their life span was probably a lot shorter, perhaps only 30-40 years.
This video is part of a series, "Dinosaurs Explained," produced by the American Museum of Natural History. In the series, Museum paleontologists answer the most frequently asked questions about dinosaurs.
To watch the videos, go to amnh.org/explore/amnh-tv. Click on the "Dinosaurs Explained" Tab on the left side of the page. In the playlist, start with the first question and play each video consecutively for a mini-course in dinosaur fossils.
Episode 1: What Is and Is Not a Dinosaur?
Episode 2: Who Discovered the First Dinosaur Fossils?
Episode 3: How Do Dinosaurs Get Their Names?
Episode 4: Are Any Dinosaurs Still Alive Today?
Episode 5: How Many Kinds of Dinosaurs Are There?
Episode 6: Where in the World Did Dinosaurs Live?
Episode 7: What Is the Earliest-Known Dinosaur?
Episode 8: What Were the Biggest and Smallest Dinosaurs?
Episode 9: What Did Dinosaurs Eat?
Episode 10: How Fast Were Dinosaurs?
Episode 11: How Intelligent were Dinosaurs?
Episode 12: Did Dinosaurs Fight?
Episode 13: How Did Dinosaurs Reproduce?
Episode 14: Did Dinosaurs Travel in Herds or Packs?
Episode 15: What Was Dinosaur Skin Like?
Episode 16: How Fast Did Dinosaurs Grow, and How Long Did They Live?
Episode 17: What Color Were Extinct Dinosaurs?
Episode 18: Were Dinosaurs Warm-Blooded?
Episode 19: How Did All Dinosaurs Except Birds Go Extinct?
Episode 20: Can We Clone Extinct Dinosaurs From DNA Preserved in Their Fossils?
Episode 21: What Is a Fossil?
Episode 22: How Do We Know Where to Look for Dinosaur Fossils?
Episode 23: How Are Dinosaur Fossils Discovered and Collected?
Episode 24: How Are Dinosaur Fossils Prepared in the Laboratory?
Episode 25: How are skeletal mounts of dinosaurs in museum exhibits built?
Episode 26: Where are all the dinosaur fossils kept once they're prepared?
Episode 27: How Do We Know Which Kind of Dinosaurs Were Most Closely Related?
Episode 28: How do we know how long ago dinosaurs lived?
Episode 29: In what kind of environments did dinosaurs live?
Episode 30: How does studying dinosaurs benefit humanity?
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