Fig. 11 in The dorsal shell wall structure of Mesozoic ammonoids

Fig. 11. Construction of the dorsal shell wall (median section, growth direction to the left, centrifugal). A. Puzosia saintoursi Collignon, 1963, BSPG MAo-1797, early Albian, Cretaceous, Ambatolafia, Mahajanga Basin, NW Madagascar; A1, the wrinkle layer forms an unusual cone-like thickening; the compensating thick dorsal inner prismatic layer forms nacreous inclusions; A2, close-up of A1; the organo-prismatic structure of the wrinkle layer thickening; A3, close-up of A1; the thickening of the dorsal inner prismatic layer shows nacreous inclusions. B. Perisphinctes (Kranaosphinctes) sp., BSPG MAn- 4756, late Oxfordian, Jurassic, Sakaraha, Morondava Basin, SW Madagascar; B1, the dorsal inner prismatic layer bridges the relief of two ribs forming a crescent hollow space; the ventral nacre layer of this shell portion is diagenetic altered; B2, close-up of B1. Abbreviations: dipl, dorsal inner prismatic layer; if, infilling; ncl, nacreous layer; opl, outer prismatic layer; wl, wrinkle layer.