Fig. 7

Harriotta raleighana (Rhinochimeridae; Holocephali; Chondrichthyes). Discontinuity of tritor in aboral region, caudally, optical microscopy in reflected surface illumination. a–e at increasing magnifications × 6.5 –× 16. a whole section of dental plate in mineralized labial cartilage (ca), outer dentine in contact at the oral margin, shows separation of upper, highly mineralized (grey) tritoral region (tri), with smooth worn surface joining with sclerotic dentine (sod), from lower mineralizing aboral tritoral tissue. Lower mineralized, aboral region, is separated by a mineral-absent line (dis, arrow) from the oral tritor, this disjunct region in field of C. b at higher magnification of tritor and sclerotic osteodentine from field in A. c high magnification (field in A), disjunct region separates old, more oral tritor from new, more aboral, all beneath a translucent layer of outer dentine (od). d Field in A, of upper tritoral tissue, above the disjunction, linear mineralization of hypermineralized dentine of intervascular matrix, with less dense mineralized dentine around vascular canal (perivascular), holes for entry of tubules (black arrows) and nutrient supply from vascular outer dentine (asterisk). In contrast E (field in A), is part of the new tritor region below the disjunction, with granular mineralization and vascular canal without circumvascular dentine, reflecting the incident light (intense white). Scale bar A = 0.5 mm