Fig. 8

Model of tooth development (compiled and modified after [45,46,47,48,49]). a lateral view of a tooth of Paracentrotus lividus, b enlargement of plumula region, c cone-like tooth elements, sticking alternately one within the other, d-f growth of individual tooth element from initial growth phase (d) to late stage (f). Abbreviations: E - epidermis, Pp - primary plate, L - lamellae, N - needles, P - prism, Sp - secondary plate, H - pillar bridges, M - median plane, Hf - main fold of pp., U - umbo, zA - central part of pp., mA - middle part of pp., sA - side part of pp.