Bone histology ofclaudiosaurus germaini(reptilia, claudiosauridae) and the problem of pachyostosis in aquatic tetrapods

Histological study of the skeleton of Claudiosaurus germaini reveals extensive pachyostosis. This feature results from the filling of intra‐osseous cavities by centripetal, endosteal deposits and occurs in conjunction with an intense remodelling of the bones by resorption and re‐deposition. Epiphyseal calcified cartilages are rapidly and entirely resorbed. Extensive pachyostosis suggests that Claudiosaurus was an aquatic reptile. However, the pachyostotic condition in this genus appears histogenetically quite different from the common type of pachyostosis observed in other aquatic tetrapods. Hence, it probably had a distinct physiological significance.