Dinosaurs that eat plants rather than meat were called herbivores. These were mostly the long-necked sauropods, such as the Brachiosaurus, Diplodocus and Stegosaurus.
These dinosaurs ate leaves, stems and twigs. Their fossils have even shown them swallowing gastroliths (gizzard stones) that helped them digest their food better.
The herbivores also had flat teeth with ridges, and did not chew their food like most mammalian animals. A well-preserved Nodosaurus fossil discovered in 2017 shows skin, armor and possible food remnants inside.
Herbivore dinosaurs used their teeth to bite off and chew plant materials such as leaves, ferns and fruits. They didn’t need to use their teeth to break down meat or other tough foods. Instead, long-necked herbivores like the Brachiosaurus could swallow plant foods whole and then let stomach acid churn them into smaller pieces, as they did with gastroliths (stones that stayed in their digestive tract to help grind food).
The large horned dinosaurs Ceratopsians had small teeth arranged in rows on their jawbones. These teeth were shaped like spoons, with a curved area and a hollow center. They were probably used for scooping or even holding food in the absence of cheeks, but they also had a low angled shape that may have helped to shear or chop up tough plant material.
Other herbivores had larger, chisel-like teeth that could be used to chop up more solid plants. The ornithischian herbivores had teeth that slid past each other like a pair of scissors, making them ideal for cutting up chunks of plants into sizes they could swallow.
Herbivores had to replace their teeth frequently due to the amount of stress placed on them as they bit into tough types of vegetation. In fact, according to a 2019 article in Smithsonian Magazine, some herbivores had sets of replacement teeth that were ready to grow in as soon as their old ones were worn out.
Some herbivores also had claws that they could use to grip and tear chunks of plants from the ground or trees. Some had to defend themselves from carnivores. For example, a cool fossil of a Triceratops shows that it has tooth marks from being attacked by a Tyrannosaurus.
While herbivores didn’t all evolve to bite, swallow and chew in the same way, there was a lot of convergent evolution. A new study finds that the skull shapes and teeth of different herbivorous dinosaurs tended to move in similar functional directions. Some of those functional optima resembled advanced mammalian herbivory while others more closely mimicked sauropodomorph or theropod herbivory.
Some herbivore dinosaurs had sharp beaks for snipping leaves or other plant material to swallow whole. They may have needed to eat large amounts of plants in order to get enough energy to grow and survive. Having a good beak was important for this kind of diet because the plant matter is harder to chew than meat.
In fact, one study has argued that beaks could even help herbivores avoid the need to chew altogether. That’s because the plant-eating dinosaurs could simply use their beaks to cut the toughest part of a leaf. This would save time and energy for the digestive system.
A beak could also be used to help herbivores hold and carry the plant materials they were eating, a helpful feature in some environments where it might not be easy to find a place to set down and eat a meal. A beak might also serve to protect herbivores from ferocious carnivores, such as the Tyrannosaurus rex. In fact, a cool fossil shows a Protoceratops fighting with a Tyrannosaurus and biting into its neck.
Most modern animals have evolved beaks for a variety of purposes, such as hunting or picking nuts and fruits. The same kinds of evolutionary changes might have taken place in herbivore dinosaurs, according to a recent study published in the Proceedings of the National Academy of Sciences. The researchers looked at a number of fossils including the herbivorous sauropod, Barosaurus.
The research team found that over time, the dinosaurs’ teeth became better suited for chopping or raking, and the beaks became better suited for snipping. The scientists concluded that this was a shift toward herbivory, and that the dinosaurs were relying less on mastication and more on cutting and squeezing.
Other evidence for the switch to herbivory included modifications in the skulls of the dinosaurs, which became more adapted to processing plants than meat. The Gigantoraptor, for example, had an enlarged beak to help process the larger pieces of food it ate. This specialized shape was not seen in other theropods and suggested that this dinosaur had become strictly herbivorous.
Unlike carnivore dinosaurs who had sharp claws for hunting and powerful teeth for chewing, herbivores had long tails that were used to help them balance and support their bodies as they ate. They also had spikes, clubs, and armor that helped them defend themselves against predators.
Herbivore dinosaurs also had specialized mouths that were designed for eating plant foods. For example, a dinosaur named Edmontosaurus had hundreds of tough, sharp teeth packed together in its upper and lower jaws. These teeth worked like a pair of coarse files, grinding leaves, fruits, and seeds to make them easier for the dinosaur to swallow and digest.
Another type of herbivore dinosaur was the long-necked Brachiosaurus. This dinosaur had a special row of rake-like teeth that it used to pull plants off tall trees and eat them whole. It also swallowed stones called gastroliths to help break down the plants in its stomach.
In addition to having special teeth and tails, some herbivore dinosaurs had horns on their heads. These horns may have been used to display their strength, attract a mate, or warn other herbivores of potential danger.
A few herbivore dinosaurs had spiky spines on their body. This included the Stegosaurus and the armored dinosaur Ankylosaurus. The spines on the Stegosaurus grew out of its neck, while the ones on Ankylosaurus grew from its shoulders.
Some herbivore dinosaurs had bone-formed clubs at the end of their tails. This was a defense mechanism that they used to strike possible predators, such as the fearsome Tyrannosaurus.
Other types of herbivore dinosaurs had beaks instead of tails. For example, the Triceratops had a beak that it could use to defend itself against the Tyrannosaurus. A fossil of a Triceratops showing bite marks made by a Tyrannosaurus has been found.
Scientists can tell if a dinosaur was a herbivore or carnivore by looking at its skull and digestive tract. Carnivores needed a wide mouth for catching and devouring large prey items, while herbivores needed a narrow mouth to process smaller foods quickly and efficiently.
Dinosaurs that ate plants instead of meat had to adapt their digestive system, as well. They needed to break down the cellulose found in plants into simpler molecules that could be absorbed by their bodies. To do this, herbivore dinosaurs developed bacteria in their stomachs to help digest the plants and made their intestines longer and more complex.
Herbivore dinosaurs also needed special teeth that were better suited for chewing plants. The long-necked sauropods, such as Brachiosaurus and Argentinosaurus, could reach the leaves of high trees by using their long necks to bend down, like a giraffe. They ate the ferns, cycads, conifers, and angiosperms that grew on their home turf. The shorter-limbed herbivores, including the Ankylosaurus and Triceratops, ate mosses, fallen leaves, and twigs.
Paleontologists rely on several different types of fossil clues to interpret the eating habits of extinct animals, including dinosaurs. One of the most important are the shapes and sizes of a dinosaur’s teeth. Herbivore dinosaurs had wide, flat teeth with ridges that were good for masticating tough plant materials. They also ate stones, called gastroliths, to help grind up the plant material in their stomachs. Today’s bird species, such as chickens and pigeons, swallow grit to help them digest their food as well.
Another important clue is a dinosaur’s posture. All carnivores were bipedal and walked on two feet, but herbivores were quadrupedal and spent most of their time on four legs. A third factor is whether a dinosaur had armor, such as bony skull frills, plates, or tail/thumb spikes. Carnivores sported these weapons to protect themselves from predators, while herbivores did not.
A fossil of a Diplodocus dinosaur may look familiar to you. It’s the dinosaur skeleton that has appeared in museums around the world since its discovery in 1903. Diplodocus was an herbivore, which means it ate plants. The Diplodocus had a front leg that was longer than its back leg. This caused the dinosaur to have a giraffe-like posture. The skeleton also shows that Diplodocus had a full set of teeth and a long, tapered nose. Its large eyes suggest that it may have been good at spotting prey from a distance.