Fig. 13 in The Changhsingian (Late Permian) ammonoids from Baghuk Mountain (Central Iran)

Fig. 13. Cross section of a specimen of Paratirolites sp. from Baghuk Mountain, MB.C.22215; note the different states of preservation of shell walls and septa: a = recrystallized but rather well-preserved shell wall and septa preferably in the mid-dorsal portion of the ammonoid conch; b = dissolved shell wall but sharp demarcation of the ammonoid's internal mould from the sediment at the lower side of the ammonoid conch; c = dissolved shell wall and nearly continuous transition from the ammonoid's internal mould towards the sediment on the upper side of the ammonoid conch (from Leda et al. 2014).