- An ancient dental gene set governs development and continuous regeneration of teeth in sharks

Comparative phylogeny of tooth replacement modes in toothed vertebrate clades. A. the shark dentition (elasmobranchs) continuously regenerates throughout life (polyphyodont) with a many-for-one mechanism (many teeth made in advance of function for each functional tooth position in the jaw). B. Bony fishes offer a diverse range of tooth replacement mechanisms, with continuous replacement with a one-for-one system (e.g. cichlid fishes, in B (Fraser et al., 2013); one replacement tooth made in advance of function for each functional position), although a many-for-one system is observed in many bony fish species. C. Reptiles show a range of diverse mechanisms for tooth replacement with a continuous polyphyodont system in some species e.g. the snake, in C (with some species showing a more restricted dentition without replacement (monophyodont; e.g. chamealeon; Buchtová et al. 2013). D. The mammalian dentition also offers a range of diverse replacement or renewal phenotypes from monophyodont mammals e.g. mice, where the only regenerative potential is observed in the continuously growing incisor (Di), and molars are never replaced. In most mammals the dentition is diphyodont with two tooth generations e.g. humans (D). A phylogenetic reduction of tooth generations are generally observed toward more higher vertebrates i.e. mammals.