Presence of plicidentine in the oral teeth of the coelacanth Latimeria chalumnae Smith 1939 (Sarcopterygii; Actinistia) F.J. Meunier a , J. Mondéjar-Fernández b,⇑ , F. Goussard b , G. Clément b , M. Herbin c a UMR 7208 (CNRS-IRD-MNHN-UPMC), BOREA, Département des Milieux et Peuplements Aquatiques, Muséum national d’Histoire naturelle, C.P. 026, 43 rue Cuvier, 75231 Paris cedex 05, France b UMR Centre de Recherche sur la Paléobiodiversité et les Paléoenvironnements (UMR CR2P), Sorbonne Universités, Muséum national d’Histoire naturelle, Centre National de la Recherche Scientifique, Université Pierre et Marie Curie Paris6, C.P. 38, 57 rue Cuvier, 75231 Paris cedex 05, France c UMR 7179 – (CNRS-MNHN), Mécanismes adaptatifs des organismes aux communautés, Département Écologie et Gestion de la Biodiversité, Muséum national d’Histoire naturelle, C.P. 055, 57 rue Cuvier, 75231 Paris cedex 05, France article info Article history: Received 15 October 2014 Received in revised form 10 February 2015 Accepted 15 February 2015 Available online xxxx Keywords: Latimeria Tooth Histology Plicidentine Evolution abstract 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. Ó 2015 Published by Elsevier Inc. 1. Introduction First described by Owen (1841 in Tomes, 1878) ‘‘plicidentine is a tissue with true dentinal tubes, which is derived from the calci- fication of a pulp, the odontoblast-carrying surface of which has been rendered complicated by infoldings of its surface’’ (Tomes, 1878). In vertebrates, plicidentine is well known in sarcopterygian fishes and in numerous fossil and extant amniotes (e.g., Bystrow, 1938, 1939, 1942; Lison, 1954; Peyer, 1968; Schultze, 1969, 1970; Kearney and Rieppel, 2006; Maxwell et al., 2011a,b; MacDougall et al., 2014); however it seems to be much scarce in actinopterygians. In his treatise, ‘‘Comparative Odontology’’, Peyer stated: ‘‘Plicidentine ... is well developed in Lepisosteus and some other ganoid fishes, but occurs only rarely and then only in very modest development in teleosts’’ (Peyer, 1968, p100); but he did not give any teleostean taxa as examples. Therefore, plici- dentine has been generally considered as an apomorphy of the Sarcopterygii (Janvier, 1996; Zhu et al., 1999) with a convergent, function-related, occurrence in certain large predatory actinopterygians like garpikes (Peyer, 1968). The extant coelacanth Latimeria is a predatory fish with well- developed teeth on its jaws. In the lower jaw, the teeth are located on a series of relatively small plates that overlain the dentary and on five more developed coronoids (Millot and Anthony, 1958; Forey, 1998). The tooth plates bear a shagreen of tiny teeth where- as the coronoids support both fang-like and smaller teeth with the exception of the fifth coronoid that bears only small denticles (Forey, 1998). In the upper jaw, teeth can be found on the premax- illaries, the palatopterygoids and the vomers (Millot and Anthony, 1958, Fig. 2). Teeth of upper and lower jaws can be gathered among three morphotypes, according to their size and morphology: [1] high, sharp cone-shaped teeth (or fangs), [2] mid-sized, sharp cone-shaped teeth, and [3] rounded small teeth (Millot and Anthony, 1958). These last small teeth also lie on the parasphenoid dental plate (Millot and Anthony, 1958, Fig. 2). The teeth of Latimeria chalumnae, one of the only extant representatives of the sarcopterygian fishes, were generally con- sidered as deprived of plicidentine (Millot and Anthony, 1958; Schultze, 1970, 2004; Millot et al., 1978). Yet, Castanet et al. (1975) noticed in their histological study of Latimeria’s teeth that ‘‘la région basale des dents présente sur les coupes transversales http://dx.doi.org/10.1016/j.jsb.2015.02.005 1047-8477/Ó 2015 Published by Elsevier Inc. ⇑ Corresponding author. E-mail addresses: meunier@mnhn.fr (F.J. Meunier), mondejar@mnhn.fr (J. Mondéjar-Fernández), goussard@mnhn.fr (F. Goussard), gclement@mnhn.fr (G. Clément), herbin@mnhn.fr (M. Herbin). Journal of Structural Biology xxx (2015) xxx–xxx Contents lists available at ScienceDirect Journal of Structural Biology journal homepage: www.elsevier.com/locate/yjsbi Please cite this article in press as: Meunier, F.J., et al. Presence of plicidentine in the oral teeth of the coelacanth Latimeria chalumnae Smith 1939 (Sar- copterygii; Actinistia). J. Struct. Biol. (2015), http://dx.doi.org/10.1016/j.jsb.2015.02.005