Fig. 15

Harriotta raleighana (Rhinochimeridae; Holocephali; Chondrichthyes). Magnesium (Mg), Calcium (Ca) and Phosphorus (P) elemental plots of adult upper rostral dental plate of selected areas. a SEM of polished surface through labial ovoids close to worn surface of sclerotic dentine (sod); note the increasing degree of mineralization in the ovoids (ov) towards the oral surface (pov, partially mineralized ovoid, fov, forming ovoids). b line plot through the barely mineralized, forming ovoids, with distributions of Mg, Ca and P ions changing relative to tissue mineralization, note d increase in levels of Mg as well as Ca and P in the partially mineralized ovoid (the elemental plots are not to the same scale). c line plot through the hypermineralized ovoids within sclerodentine (sod), with e much higher values for all mineral ions of ovoids but Mg relatively less in the sclerotic osteodentine, i.e. distributions of Mg, Ca and P ions changing relative to tissue mineralization. f plot of MgO/P₂O₅ against total MgO + P₂O₅ + CaO for hypermineralized dentine, incorporating data from both ovoids and tritors of lower and upper tooth plates of the same individual; n = 110 square area analyses. Pure whitlockite (red arrow) would be expected to have a MgO/P₂O₅ ratio of approximately 0.081