Rumination syndrome the syndrome in mentally healthy patients appeared thereafter. At first, adult rumination was described and treated as a benign condition. It is now described as otherwise. While the base of patients to examine has gradually increased as more and more people come forward with their symptoms, awareness of the condition by the medical community and the general public is still limited. The chewing of cud by animals such as cows, goats, and giraffes is considered normal behavior. These animals are known as ruminants. Such behavior, though termed rumination, is not related to human rumination syndrome, but is ordinary. Involuntary rumination,
Chewing Ornithopods, a group of dinosaurs including the Hadrosaurids ("duck-bills"), developed teeth analogous to mammalian molars and incisors during the Cretaceous period; this advanced, cow-like dentition allowed the creatures to obtain more nutrients from the tough plant life. This may have given them the advantage needed to usurp the formidable sauropods, who depended on gastroliths for grinding food, from their ecological niches. They eventually became some of the most successful animals on the planet until the Cretaceous–Paleogene extinction event wiped them out. The process of chewing has, by analogy, been applied to machinery. The U.S. Forest Service uses a machine called