Fig. 2 in A review of gastrolith function with implications for fossil vertebrates and a revised classification

Fig. 2. Examples for in situ gastroliths in vertebrates. A. Cut−open gizzard of an extant capercaillie (Tetrao) from Russia during dissection (gastroliths: IPB R574). Strong muscles surround the gizzard which contains the gastroliths and plant matter which has been ground. B. Gastrolith cluster in the Oligocene galliform bird Palaeortyx from Enspel/Germany (PW 2005/5023a−LS). C. Cluster of gastroliths with variable grain sizes in the aquatic tangasaurid Hovasaurus from the Upper Permian Sakamena Formation of southern Madagascar (NHMS WP1499). D. Field photo of an undescribed plesiosaur skeleton with gastroliths from the Upper Cretaceous Tropic Shale of Glen Canyon National Recreation Area, Utah/USA (MNA V10046). E. Cluster of ±112 gastroliths in the ceratopsian dinosaur Psittacosaurus from the Lower Cretaceous Ondai Sair Formation of Ussuk/Mongolia (AMNH 6253). F. Gastrolith cluster in the fossil alligatoroid Diplocynodon from the Eocene of Messel/Germany (HLMD Me 7493).