FIG. 3 in False teeth: conodont-vertebrate phylogenetic relationships revisited

FIG. 3. — Morphogenesis of euconodont elements: A, hypothetical euconodont morphogenesis of apparatus, based on Clydagnathus cavusformis Rhodes, Austin & Druce, 1969, Stage 1 – "shards" (cf. Reif 2006) of apparatus. There is no dental lamina, dental papilla, or tooth bud structure present (cf. Reif 1984); a pulp is absent; the tissues are not living but laid down like layers of inorganic crystals; repair is done by living tissue surrounding the element; B, Stage 2, continuous centrifugal growth with outer layers forming multicusps; whole apparatuses must form in one contemporaneous session to work, unlike vertebrate rotational dentitions (even in the most advanced mammals there are three separate cycles possible: milk, adult and wisdom teeth); C, Stage 3, the working complex in dorsal view, anterior to top; oesophagus to bottom: reconstructed seximembrate apparatus of Polygnathus linguiformis linguiformis Hinde, 1879 (assembled by PB, and see Sweet 1998: 99) based on elements from sample BT 18, S Morocco, Tafilalt, Lower Givetian Bou Tchrafine section (see Bultynck 1987). The location of the elements is based on the most generally accepted scheme. The elements are shown in such way that their outline and ornamentation can be clearly recognized; their orientation does not correspond to the original natural orientation in the apparatus. So, the M and S elements (except the Sa) and the Pb element should be turned upward over an angle of 45°. The anterior and posterior processes of the Pb element meet at an angle of about 130°, similar to the deflection of the posterior tongue of the Pa element. The orientation of the P elements is a matter of discussion. The elements of the apparatus are deposited at the Institut royal des Sciences naturelles de Belgique, Brussels, under catalogue number I.R.Sc.N.B. no. b5177. Scale bar: 500 μm.