The ontogeny of the dentitions of some Urodela

Abstract

This work describes the morphology of the teeth of Triturus vulgaris and Salamandra salamandra. Tadpoles and adult animals were examined together with specimens of Amblystoma mexicanum. Hypogeophis alternans. Rana temporaria and Protopterus aethiopicus. The descriptions of the gross morphology and development confirms those of many previous workers.In addition the unique pulp structure is described as a specialisation associated with an extradental capillary network. The teeth of tadpoles and adults are fundamentally different; tadpoles possess many simple teeth with mesodermal enamel, comparable to those of many fish, but after metamorphosis there are fewer teeth which are bicuspid and have ectodermal enamel such as is found in all tetrapods. The arrangement of the teeth in fields associated with certain dermal bones is described. Throughout larval growth the skull shape changes imposing a corresponding modification in dentition; at metamorphosis gross reorganisation occurs, coronoid and palatine bones and teeth are lost and the remainingbones retain only single rows of bicuspid teeth. The organisation of the teeth in the Urodeles is unique, and shows during ontogeny the transition between aquatic and terrestrial tetrapods which must have occurred during vertebrate evolution. Urodele teeth are similar to those of the Anura and completely disimilar to those of the Dipnoa, and thus this study does not confirm the theories of Save-Soderburg and Holmgren, but suggests that the Amphibians are a natural group unrelated to the Dipnoans but possessing features in common with all other Tetrapods.