Photos Fast-Grower
Aug. 6, 2008 -- Unlike many dinosaurs that had natural armor, body spikes, huge teeth and other means of defense, the duck-billed hadrosaur was a seemingly vulnerable, soft-bodied plant eater. But it did evolve one very effective way of beating predators: It outgrew them. The hadrosaur Hypacrosaurus, which lived 67 to 80 million years ago, grew three to five times faster than any of its predators, including Tyrannosaurus rex, according to a study published in this week's Proceedings of the Royal Society of London B: Biological Sciences. Adults of the duck-billed giant measured around 9 feet at the tips, grew to over 30 feet in length and could weigh as much as 4.4 tons. Lead author Lisa Cooper admitted that such big game is often desirable, "but hunting requires a lot of energy and is dangerous." "By reaching its full body size quickly, Hypacrosaurus probably obtained a size refuge, or a body size that made it more difficult to be hunted, compared to smaller dinosaurs," said Cooper, who is a doctoral student at Kent State University and a researcher with the Northeastern Ohio Universities College of Medicine. Cooper and colleagues Andrew Lee, Mark Taper and John Horner obtained growth rate data from a Museum of the Rockies' Hypacrosaurus, which means "near the highest lizard," in reference to the dinosaur's impressive height. To collect the data, Cooper explained that she and her team looked at cross sections of the dino's limb bones by "grinding them down until we could see light through them." The scientists found that, during the fossilization process, the shape of bone cells and, "more importantly, growth rings" are preserved. Similar to calculating the age of a tree, the researchers then counted the growth rings to determine the dinosaur's growth rate. They next compared that rate to those of three duck-billed predators: T. rex, Albertosaurus and Troodon, a small, Velociraptor-like dinosaur that possessed sharp, serrated teeth. |
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