Physiology of dinosaurs way as sauropods. The pachycephalosaurs had small heads and weak jaws and teeth, but their lack of large digestive systems suggests a different diet, possibly fruits, seeds, or young shoots, which would have been more nutritious to them than leaves. On the other hand, ornithopods such as "Hypsilophodon", "Iguanodon" and various hadrosaurs had horny beaks for snipping off vegetation and jaws and teeth that were well-adapted for chewing. The horned ceratopsians had similar mechanisms. It has often been suggested that at least some dinosaurs used swallowed stones, known as gastroliths, to aid digestion by grinding their food in muscular gizzards,
Bolus (digestion) Bolus (digestion) In digestion, a bolus (from Latin "bolus", "ball") is a ball-like mixture of food and saliva that forms in the mouth during the process of chewing (which is largely an adaptation for plant-eating mammals). It has the same color as the food being eaten, and the saliva gives it an alkaline pH. Under normal circumstances, the bolus is swallowed, and travels down the esophagus to the stomach for digestion. Once the bolus reaches the stomach, it mixes with gastric juices and becomes chyme, which then travels through the intestines for further digestion and absorption, and eventual discharge as