Fig. 1

Harriotta raleighana (Rhinochimeridae; Holocephali; Chondrichthyes). Morphology and microstructure of adult dental plate in lower jaw. a adult, vertical section, left labial and right lingual. c juvenile, b, d adult, μCT renders of paired plates, dorsal view. a rostralmost section through ovoids only (no tritor), incident reflected illumination reveals different tissues relative to their degree of mineralization complimentary with the density differences in μCT images (b–d). Grey, translucent, most mineralized HD of in set of five ovoids (ov1), with one projecting at oral surface, white is less well mineralized in aboral dental plate, including more aboral second set (ov2). Outer dentine (labial and lingual, od) shows developing degrees of mineralization, grey translucent oral, white aboral. Cartilage is also white with low degree of mineralization in both outer layers (ca; jaw tissue in b, c). Lingual, oral tissue is well mineralized as sclerotic osteodentine (sod), to a depth that reflects the worn surface (white arrow, deep sclerodentine forming front; fields of Fig. 2b; see Fig. 18a for interpretive drawing). b adult, worn oral surface with relief from harder dentine of ovoids (ov) and tritors (tri), slender support from mineralized cartilage (ca). c juvenile, worn oral surface reveals similar distribution of harder dentine, but as rods (rod; see Fig. 16) and lingually a differently shaped tritor (tri). d adult, density dissected μCT render, showing hypermineralized dentine of ovoids and tritors (ov, tri). Scale bars A ,= 0 .5cm, B, D = 0 .5cm. C = 0.25 cm