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fact file



Name means: Oak Reptile


Species: altus

Range: Late Jurassic (Tithonian, 150-145 MYA) from Utah, Wyoming, Colorado

Size estimate: 8-14 ft length, 170-200 lbs

Discovery: Othniel Charles Marsh, 1894

Classification: dinosauria, ornithischia, ornithopoda, iguanodontia, dryosauridae


This swift plant-eating dinosaur may have used its speed to evade predators, but it had more advantages than quickness. The leaf-like shape of its teeth kept them sharp as they wore down. Its narrow beak allowed it to select the most nutrient-rich foods. Such efficiency in processing food gave Dryosaurus the fuel it needed to stay fast as well. Though it lacked the strange defensive measures of other dinosaurs, its close relatives gave rise to a group of dinosaurs that thrived through the end of the Mesozoic era. These duck-billed hadrosaurs also featured efficient food-processing designs. They became one of the main groups of plant-eaters during the Cretaceous period.


Contrary to popular belief, the name "Dryosaurus" has nothing to do with the shape of its teeth. It refers to the forests it likely lived in. Dryosaurus fossils come from the Morrison Formation. This geological feature spans from Arizona to North Dakota—13 states in all. Fossils from these rocks show that the climate at that time was not that different from today's. And like the modern climate, various animals and plants likely occurred in distant parts of the formation. Dryosaurus and other animals may have lived in both forests and plains. In its ecology, Dryosaurus probably filled a role like the one modern deer now occupy. It shared its environment with giant sauropods like Camarasaurus and Diplodocus, and other bird-hipped dinosaurs like Stegosaurus, Camptosaurus, and Gargoyleosaurus. Its predators may have included Allosaurus, Ceratosaurus, and Torvosaurus.


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