What Did Dinosaurs Eat?

Dinosaurs ate almost everything. Over 160 million years, they occupied essentially every feeding niche available to large land animals — apex predators, bulk herbivores, insect-hunters, fish specialists, seed-eaters, and at least some that were willing to consume almost anything they could get hold of. The diversity of dinosaur diets mirrors the diversity of the group itself.

Understanding what individual species ate is one of the more tractable questions in palaeontology, because diet leaves direct evidence in the fossil record — in the teeth, the jaw mechanics, the gut contents when preserved, the coprolites, and the bite marks left on prey bones.

Carnivores: The Predators

The largest and most famous dinosaurs were carnivores — theropods with serrated teeth, binocular vision, and predatory anatomy. But “carnivore” covers a wide range of hunting strategies.

T-Rex was a bone-crusher. Its thick, conical, heavily reinforced teeth weren’t designed to slice flesh the way a shark’s teeth are; they were designed to penetrate and crush, allowing T-Rex to eat everything including the bones of its prey. Bite marks from T-Rex have been found on Triceratops frills and Edmontosaurus tail vertebrae — both showing that T-Rex was hunting live animals, not just scavenging. T-Rex almost certainly did both.

Allosaurus from the Jurassic had a different approach: its jaw mechanics suggest it used its upper jaw like a hatchet, slamming it down into prey with its mouth wide open rather than simply biting. Spinosaurus appears to have specialised heavily in fish — its conical, interlocking teeth and probable semi-aquatic lifestyle mirror the anatomy of modern gharials and other fish-specialists. Velociraptor and the other dromaeosaurids likely used their sickle claws to pin prey and their jaws to deliver killing bites to vulnerable areas.

Smaller carnivores like Compsognathus ate lizards, small mammals, and insects. Their fossils have been found with identifiable gut contents — one specimen preserved the remains of a small lizard.

Herbivores: The Bulk Eaters

Herbivorous dinosaurs faced a challenging physics problem. Plant material — particularly the conifer needles, cycad fronds, and ferns that dominated Mesozoic vegetation — is relatively low in nutrition and requires extensive processing to extract energy. Grass didn’t exist for most of the dinosaur era; it evolved only near the end of the Cretaceous. The Mesozoic was a world of tougher, harder plants than modern grasslands.

Sauropods like Brachiosaurus and Diplodocus solved this with bulk. They didn’t chew their food — their teeth were simple rakes or pegs used to strip vegetation, and they swallowed it whole. Fermentation in enormous gut chambers did the digestive work. Many species also swallowed gastroliths — smooth stones found in their stomach regions that helped grind down plant material mechanically. A large sauropod needed hundreds of kilograms of vegetation per day, which is why they had to keep moving almost continuously and why their long necks allowed them to sweep a large area without repositioning their massive bodies.

Hadrosaurs took a different approach: they had dental batteries, rows of hundreds of teeth continuously replacing themselves, that could grind plant material more efficiently than almost anything else alive at the time. A hadrosaur jaw could process tough vegetation that most herbivores couldn’t manage.

Triceratops and related ceratopsians had parrot-like beaks for cropping tough vegetation, combined with shearing cheek teeth. Stegosaurus, despite its intimidating appearance, had weak jaws suited only to soft, low-growing ferns and perhaps fruit.

The Omnivores and Specialists

Several dinosaur groups defied easy categorisation. The ornithomimids — Gallimimus, Ornithomimus — had toothless beaks and appear to have been genuine omnivores, eating whatever was available: seeds, fruits, insects, small animals. Modern ostriches, which they strongly resemble anatomically, have a similarly catholic diet.

Oviraptor was long assumed from its name to eat eggs — “egg thief” — but the evidence for this is weak, and the animal was almost certainly an omnivore capable of cracking hard food items with its powerful beak. Therizinosaurus, despite its alarming 70 cm claws, was a herbivore, using those claws to pull down branches rather than to hunt.

How We Know What They Ate

The most direct evidence is gut content. Several specimens have been found with identifiable material in the stomach region — plant matter, fish bones, small animals. This is rare but unambiguous.

Coprolites (fossilised dung) can be assigned to specific animals when found in close association, and their contents directly reveal diet. Bone fragments in coprolites from the Morrison Formation have been attributed to large carnivores and give information about feeding behaviour — including bone consumption rates.

Bite marks on bones are extremely informative. Tooth marks on prey bones can be matched to the tooth shapes of specific predators, and patterns of bone damage reveal whether the animal was crushing bone (as T-Rex did) or making more superficial cuts (as slashing predators did). Healed bite marks on prey animals confirm that predators were hunting live animals that sometimes escaped.

Tooth morphology is the most widely available evidence. The relationship between tooth shape and diet is well-established across many animal groups: serrated, blade-like teeth for slicing flesh; conical, interlocking teeth for grabbing fish; peg-like or columnar teeth for raking vegetation; batteries of grinding teeth for processing tough plant material. These patterns are consistent enough that tooth shape alone provides a strong dietary inference.

Jaw mechanics — the angles, leverage arms, and muscle attachment points of the jaw — tell us about bite force and feeding technique, which often correlate with specific prey types. And isotopic analysis of tooth enamel can distinguish browsers from grazers, and marine from terrestrial diets, by comparing carbon and nitrogen isotope ratios preserved in the fossil material.

The picture that emerges is of an ecosystem as complex and diverse as any alive today, with specialised feeders occupying every available niche. The Mesozoic food web was not simpler than what we see now; if anything, the sheer size range of dinosaurs — from 30 g feathered insect-hunters to 70-tonne sauropods — created feeding relationships with no modern parallel.