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How dinosaurs lived

How dinosaurs fed

Plant-eaters and meat-eaters of the JurassicPlant-eaters and meat-eaters of the Jurassic 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 fossil remainsGastroliths found in fossil remains

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 feedingA large herd of Apatosaurus feeding
Saurolophus skullSaurolophus skull

Plant-eaters

Saurolophus, a hadrosaur, had a flat beak and a hundreds of cheek teeth. Using its beak, it tore off vegetation which it then chewed up in its teeth. This ability allowed hadrosaurs to feed on the toughest plant material: bark, pine cones and conifer needles—food no other plant-eater could digest. 
 

Compsognathus fossil, containing lizard bonesCompsognathus fossil, containing lizard bones

Meat-eaters

For meat-eating dinosaurs, their food had to be found or caught. From the behaviour of modern lions and hyenas, we know that few large meat-eaters would turn down the opportunity to scavenge, or steal the kill of others. It is likely, however, that large theropods, with their powerful build, were primarily active hunters of other dinosaurs. We know from fossil evidence of stomach contents that some predators, especially smaller ones (much commoner in the fossil record than the giants) fed on smaller animals, such as fish, lizards, mammals and insects.


Baryonyx fishingBaryonyx fishing

Fish-eaters

Fish scales have been found inside the fossil remains of Baryonyx. Its skull was long and narrow like a crocodile’s, with jaws lined with narrow, pointed and finely serrated teeth. So we know Baryonyx ate fish—but it is likely that it hunted other prey as well. No large land animals today can survive on a diet of fish alone. Iguanodon bones have also been found inside Baryonyx’s body cavity, suggesting that it could have scavenged on its corpse.
 

Insect-eaters

Microraptor picks off a dragonfly in flight.Microraptor picks off a dragonfly in flight.As with birds, insects would have been a highly nutritional food for the tiniest dinosaurs, such as Microraptor, and easy to catch, too. Recent studies of Microraptor's fossil remains show its guts contained bones of a mammal and bird, along with fish scales. This proves it had a very wide-ranging diet.
 

ConsultantChris Jarvis
 

See also in Prehistoric

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.

The discovery of the fossil remains of two birds, called Confuciusornis, and a tiny winged dinosaur, Sinornithosaurus, inside the belly of the small Chinese Cretaceous predator, Sinocalliopteryx, has led some scientists to suggest that small, ground-dwelling hunters caught their prey by ambushing it, just as a cat creeps up on a bird.

From studies of the fossilized remains of Cedarosaurus, an Early Cretaceous sauropod, palaeontologists discovered a collection of gastroliths weighing 7 kg (more than 15 pounds)

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