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How dinosaurs lived

Plant-eating dinosaurs (Barosaurus and Dryosaurus) and a meat-eating dinosaur (Allosaurus) of Jurassic North America. Dinosaurs can be divided into plant-eaters or meat-eaters, although some may have been omnivores: they ate both animals and plants. The shape of a dinosaur’s jaws or teeth is often the first clue that reveals to which group it belonged and how it obtained its food. We know from the fossil record what food was available at a certain time. In some fossils, the stomach contents have also been preserved, providing vital clues about diet. We can also work out how dinosaurs fed simply by studying modern animals’ eating habits.



Gastroliths found in the belly area of the fossil remains of Psittacosaurus

Gastroliths

The sauropods’ sheer size meant they would have needed immense amounts of food in the form of plant matter to nourish them. Yet their teeth were small, few in number and incapable of chewing. How could they digest their colossal meals?
The presence of pebbles in some fossil remains provides the answer. Known as gastroliths, these polished, rounded pebbles were a vital part of the digestive system.
From studying how birds—the dinosaurs’ modern relatives—eat, we know that they swallow grit or small stones to fill their gizzard, a part of their stomach. Muscular movements inside the gizzard cause the stones to grind the food into a paste, which can then be digested in the intestines. Sauropods such as Apatosaurus could digest their vast daily intake of unchewed vegetation with the help of gastroliths in the same way.A large herd of Apatosaurus lumber through a Jurassic forest, stripping enormous amounts of leaves from the trees as they go.
Palaeontologists can discover a lot about a dinosaur's feeding habits from studying dinosaurs' jaws and teeth as in, for example,...Read More >>Palaeontologists can discover a lot about a dinosaur's feeding habits from studying dinosaurs' jaws and teeth as in, for example, Saurolophus, whose fossil skull is pictured here.

Plant-eaters

One unusual group of dinosaurs, the heterodontosaurs, had teeth for eating both plants and flesh in their jaws. Their cheek teeth were good for grinding tough plant material, while the pointed fangs at the front of their jaws, along with the sharp, curved claws on their arms, suggest they were predators, too.

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