Dinosaurs left no menus behind. But they did leave something arguably more useful: millions of pieces of hard physical evidence, preserved across geological time, that allow scientists to reconstruct prehistoric diets with surprising precision. This is the forensic science of palaeodietology.
The Shape of a Tooth Tells Everything
The single most reliable indicator of diet is tooth morphology — the size, shape, and arrangement of teeth. Evolution is ruthlessly efficient: an animal's teeth are shaped almost entirely by what it eats.
Carnivorous dinosaurs like T. Rex and Allosaurus had laterally compressed, serrated teeth — essentially biological steak knives, designed to slice through flesh and sever tendons. The serrations, called denticles, functioned exactly like a bread knife: more cutting surface per millimetre, able to grip and tear rather than simply push.
Herbivores show the opposite pattern. Sauropods like Diplodocus had peg-like or pencil-shaped teeth used purely for raking leaves off branches — they didn't chew. Hadrosaurs (duck-billed dinosaurs) had dental batteries: hundreds of tightly packed teeth forming a continuous grinding surface, replaced from below as they wore down — one of evolution's most elegant solutions to a hard-plant diet.
Key fact: Triceratops had a beak-like rostral bone at the front for cropping, followed by dental batteries containing up to 800 individual teeth — all working together as a single shearing surface for tough Cretaceous vegetation.
Stomach Contents and Coprolites
Occasionally, fossils preserve something extraordinary: the last meal. Several spectacular specimens have been found with recognisable gut contents still in place. A Scipionyx fossil from Italy preserved intestinal tissue; Baryonyx specimens were found with fish scales and digested bones still inside the ribcage.
Equally informative are coprolites — fossilised faeces. These can reveal not just what an animal ate, but how it processed food. A large carnivore coprolite from Saskatchewan contained crushed bone fragments from a juvenile hadrosaur — direct evidence that T. Rex didn't just bite and swallow, but actively crushed bone to extract marrow, similar to modern hyenas.
Bite Marks on Bone
Fossilised bones frequently carry the signatures of their predators. Parallel scratch marks from serrated teeth, puncture holes from canine-like teeth, and distinctive spacing patterns can often be matched precisely to the tooth morphology of specific species. At sites like the Hell Creek Formation, bones show both T. Rex bite marks and evidence of smaller scavengers finishing what the apex predator left behind.
Isotope Analysis: A Chemical Fingerprint
Modern palaeodietology increasingly uses isotope chemistry. The ratios of stable isotopes — particularly carbon-13/carbon-12 and nitrogen-15/nitrogen-14 — in fossil bone collagen reflect what an animal ate over its lifetime. Nitrogen-15 concentrates up the food chain, so high N-15 ratios reliably indicate a meat-heavy or top-predator diet. Carbon isotopes distinguish between C3 plants (trees, ferns) and C4 plants (grasses), revealing what herbivores actually browsed.
This technique confirmed that Spinosaurus fed primarily on aquatic prey, and helped researchers understand the complex mixed diets of omnivorous species like Gallimimus.
The Bigger Picture
No single line of evidence tells the whole story. Modern palaeodietologists combine tooth morphology, skull biomechanics (how much stress the jaws could bear), gut contents when available, isotope chemistry, and ecological context — what other species lived in the same environment, what plants were available — to build a complete dietary portrait. The result is a picture of prehistoric food webs almost as nuanced as any modern ecosystem we might study today.