Ammonite taphonomy and stratigraphy of the Bajocian at Maizet, south of Caen (Calvados, NW France)

Mollistephaninae and Frebolditinae, new subfamilies of Middle Jurassic stephanoceratid Ammonoidea

“…The specimens were whitened with magnesium oxide prior to photography. a, b MGPT-PU112493, oral and right side views of resedimented, neomorphic shell and internal mold, from bed 7 of the Maizet section (Calvados, NW France; Pavia et al 2013), whose condensed fossil assemblage of the ''Oolithe ferrugineuse de Bayeux'' unit mixes ammonites from the Humphriesianum to Niortense transition; the fossil is placed within the upper Banksi Subzone. c, d Ventral and left side views of a plaster cast of a resedimented, neomorphic shell and internal mold; original specimen stored in the collection of Lionel Maerten, Ver-sur-Mer, Calvados; the fossil comes from an undefined bed of the condensed É vrecy succession (Calvados, NW France, Pavia et al 2013) where the section is similar to the one of Maizet.…”

“…Two specimens, collected from the condensed fossil assemblages of the ''Oolithe ferrugineuse de Bayeux'' unit and referred to the Banksi Subzone of the Maizet and É vrecy sections (Calvados, NW France; Pavia et al 2013) have been identified as belonging to a new unnamed species of Patrulia (Fig. 8).…”

“…The integration of data from these two very different stratigraphical situations is possible because the latter authors have demonstrated that a detailed taphonomic analysis could provide biochronological information from fossils in condensed sections. In particular, for the section of Maizet, Pavia et al (2013;Fig. 2) distinguished between resedimented specimens (i.e., taphonomic elements displaced after accumulation on the sea floor and prior to burial, therefore contemporaneous with the sedimentary matrix) and reelaborated specimens (i.e., exhumed and displaced before final burial; therefore, older than the sedimentary matrix).…”

“…In particular, the studied specimens come from the Feston, Les Dourbes and Chaudon sections (Digne area: Pavia 1973Pavia , 1983aPavia , 2012Pavia and Zunino 2012) and from the Bretteville and Maizet sections (Calvados: Pavia and Martire 2010;Pavia et al 2013). Further Bajocian specimens, crucial to the identification of Sub-Mediterranean taxa, come from the Iberian Range, namely from the La Olmeda (Cuenca) and Masada Toyuela (Albarracin, Teruel) sections (Fernandez-Lopez 1985, 2014.…”

“…Class Cephalopoda Cuvier, 1798 Subclass Ammonoidea von Zittel, 1884 c resedimented ammonite, d reelaborated ammonite, e belemnite rostrum, f lithoclast or oncoid stained by Fe oxides, g phosphatized intraclast, h ferruginous ooids and i marly sedimentary matrix (based on data from Pavia et al 2013). Note the relative age of the beds containing condensed fossil assemblages can be determined taking into account the age of the most recent taxa identified with resedimented elements Order Ammonitida Fischer, 1882Superfamily Stephanoceratoidea Neumayr, 1875Family Stephanoceratidae Neumayr, 1875(Syn.…”