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| Diversity
in the “Age of Dinosaurs” The Mesozoic, or ”Age of Dinosaurs,” is often illustrated with a scene from the Late Jurassic Period with its dramatic sauropods. But this was not the picture throughout the Jurassic. In the Early Jurassic, many dinosaurs were very similar to their Triassic relatives. These included prosauropods, early theropods (Dilophosaurus), small ornithischians, and early armored forms (Scelidosaurus). Sauropods were present but uncommon. By the Late Jurassic, however, these long-necked, long-tailed herbivores ruled the land. Behemoths such as Diplodocus, Apatosaurus, and Brachiosaurus were among the largest animals to ever walk on land. Some of the largest Jurassic dinosaurs may have reached lengths of 120 feet (35 meters) and weights of 60 tons. Because of their size, the biology of sauropods is still subject to scientific debates. These revolve around whether sauropods could lift their heads high in the air or rear up on their hind legs, how they mated, and what foods they ate. By the Late Jurassic nearly every major kind of dinosaur had appeared, and they are found on every continent. Although prosauropods had gone extinct, the world was now home to armored stegosaurs (Stegosaurus) and ankylosaurs, herbivorous ornithopods of all sizes (Camptosaurus), and large (Allosaurus) and small (Ornitholestes) predatory theropods. Many of these dinosaurs were collected from the Morrison Formation, a thick formation of mud, silt and sand that was deposited in western North America about 150 million years ago by a large braided river system running across much of the central part of the continent. These Late Jurassic dinosaurs had close relatives in Africa and Europe, indicating that these areas were still connected. In the Cretaceous, however, these connections would finally be severed. |
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Overview | Jurassic Life | Diversity in the “Age of Dinosaurs”
Flight and the Origin of Birds | Jurassic Climate and Tectonic Activity
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