Physiology of dinosaurs and that this was a feature they shared with birds. In 2007 Oliver Wings reviewed references to gastroliths in scientific literature and found considerable confusion, starting with the lack of an agreed and objective definition of "gastrolith". He found that swallowed hard stones or grit can assist digestion in birds that mainly feed on grain but may not be essential—and that birds that eat insects in summer and grain in winter usually get rid of the stones and grit in summer. Gastroliths have often been described as important for sauropod dinosaurs, whose diet of vegetation required very thorough digestion, but
Intracellular digestion digested by the lysosome's enzymes. Intracellular digestion can also refer to the process in which animals that "lack" a digestive tract bring food items into the cell for the purposes of digestion for nutritional needs. This kind of intracellular digestion occurs in many unicellular protozoans, in Pycnogonida, in some molluscs, Cnidaria and Porifera. There is another type of digestion, called extracellular digestion. In amphioxus, digestion is both extracellular and intracellular. Intracellular digestion is divided into heterophagic digestion and autophagic digestion. These two types take place in the lysosome and they both have very specific functions. Heterophagic intracellular digestion has an