Fig. 10

Harriotta raleighana (Rhinochimeridae; Holocephali; Chondrichthyes). Progressive mineralization of tritor tissue, microstructure and ultrastructure lower plate, low to high magnification. a Nomarsky optics at forming front of tritoral dentine (see Fig. 6a), where multiple wide, and narrow tubules run into dense mass of saccules, and granular crystals (tu, gr). b most highly mineralized (translucent) dentine at worn tritural surface (tri, see Fig. 7a, b). c–h (electron micrographs at progressive, consistent magnifications × 250, × 500, × 1000). C mineralized tritor (tri), with many cell body spaces (cbs), tubules running from these into HD, differential mineralization (lighter indicates higher mineralization), same level as circumvascular dentine and trabecular dentine, fields of D, E shown. d saccules (sac) in low mineral density region. e chaotically arranged tubules (tu) in less mineralized part of tritor, saccules within these (sac). f, g more aboral, stage earlier in process of mineralization than in C, D. f mineralization is highest in the middle of the tritor, between two vascular canals, field of G is shown, beneath outer dentine (od, in F) including vascular canals (vas) that supply the hypermineralized dentine. g extensive volumes of disorganized dentine tubules (tu), with saccules (sac), many saccules are empty with white edges, shown in relief (edge artefact of BSE). h region of tritor dominated by complex network of tubules in large numbers, many as expanded saccules, field of I shown. i transmitted light, Nomarsky with closeup of saccules (see also Fig. 9f, g, h). Scale bar A, C–H = 100 μm; B = 300 μm; I field width is 150 μm