Some herbivorous dinosaurs did not chew at all, but merely swallowed whole the vegetation they pulled off a tree or bush. They had larger (and probably more rugged) digestive tracts than carnivorous dinosaurs in order to digest the tough, fibrous plants they ate. Some herbivores, such as the Ankylosaurus, even had fermentation chambers along their digestive tract in which tough fibers would be broken down by bacteria. In addition, some herbivores had gastroliths, or “gizzard stones,” in their digestive tract, which would grind up the fibrous plants, helping to digest the material. (It is interesting to note that this method is similar to how birds swallow stones to grind up ingested matter in their digestive tracts.) These stones were deliberately swallowed, and are often found with fossils of herbivores. Both of these actions prepared the vegetation for digestion.

Other herbivorous dinosaurs, like the duck-billed hadrosaurs, had special teeth that would grind up the food before swallowing. Ceratopsians like the Triceratops had sharp teeth and powerful jaws that enabled them cut through tough plants. Still other herbivores had cheek pouches, apparently used to store food for later ingestion. They probably concentrated their meals on certain plants, especially the ancestors of the conifers, flowering plants, horsetails, ferns, and cycads that grow today.