Presence of plicidentine in the oral teeth of the coelacanth Latimeria chalumnae Smith 1939 (Sarcopterygii; Actinistia).
The extant coelacanth Latimeria is a sarcopterygian predatory fish with caniniform teeth on its upper and lower jaws. The teeth are constituted of a cone of dentine with an apical cap of enamel, and they are fixed to the osseous component of the jaws by an attachment bone. Internal walls of the tooth base show folds that have been firstly interpreted in the past as radial vascular canals. Three-dimensional visualisation of these foldings using X-ray tomographic techniques and new histological interpretation lead to reconsider these structures as true plicidentine. The folds of the dentine do not invade the whole pulp cavity of the tooth contrary to the plicated condition of most fossil sarcopterygian fishes (e.g., Eusthenopteron, Porolepis, Megalichthys) certain fossil marine reptiles (ichthyosaurs) and extant varanids; in Latimeria they are limited to the lower third to the half of the pulp cavity. The presence of plicidentine in Latimeria's teeth is proposed to be a plesiomorphic character for sarcopterygians.