FIGURE 2 Chimaera monstrosa Linnaeus, 1758, 49 in Holocephalan (Chondrichthyes) dental plates with hypermineralized dentine as a substitute for missing teeth through developmental plasticity

FIGURE 2 Chimaera monstrosa Linnaeus, 1758, 49 cm juvenile upper dentition, μCT-scans. (a) Oral view, including anterior dental plate with ridges on the lingual surface. (b) Upper dentition in oral view, with posterior dental plate cut away to show internal structure, and ridges on the anterior dental plate. The asterisk indicates the region shown in (d) and arrows indicate close correspondence between anterior and posterior dental plates. (c) Upper dental plates rendered (Avizo) showing rods of hypermineralized dentine (whitlockin) in both. (d) Close-up of the aboral anterior dental plate, showing newest, bulbous postero-lingual end of the ridge. The asterisk indicates newly developing trabecular dentine below the most aboral ridge. (e) Anterior dental plate, with posterior plate almost completely cut away to show lingual ridges relative to cartilage of the upper jaw. (f) Symphyseal view of anterior dental plate, with opposing plate almost completely cut away to show the ridges. The asterisk indicates bulbous aboral new ridge tissue. There are also three separate growth regions (arrows indicate direction of growth), anterior ridge or column, and posterior furrow on each side of the ridged zone (arrows 1 and 2). (g) and (h) Anterior dental plate, virtual section through developing rod, framework trabecular dentine, ridges in section with forming sclerotic dentine inside. (g) Arrows indicate correspondence between the ridge and developing rod. Abbreviations as in Figure 1. brc, cartilage of the braincase; f.td, forming trabecular dentine; rd, whitlockin rods; sod, sclerotic osteodentine, ujc, upper jaw cartilage. Scale bars, (a) 1.5 cm, (e) and (f) 1 mm