In situ finds of aptychi in the Barremian of the Alpine Lower Cretaceous (Northern Calcareous Alps, Upper Austria)

Ammonoid Buccal Mass and Jaw Apparatus

“…Previous reconstructions of the ammonoid jaw apparatuses have been done on the basis of such well-preserved in situ material whose taxonomic relationships are known (e.g., Lehmann 1976Lehmann , 1981Lehmann , 1990Doguzhaeva et al 1997;Tanabe and Fukuda 1999;Tanabe and Landman 2002). Tanabe et al 1980a;Kanie 1982; this study (UMUT MM 19875) Tanabe and Mapes (1995) b Described as "anaptychus" by Zakharov (1974) Originally described as rhynchaptychus by Vašíček (2010) e The lower jaw is preserved near the shell aperture f Jaws were found individually, but their taxonomic relationships were assumed from their mode of occurrence g Mistakenly identified as Lamellaptychus by Lukeneder and Tanabe (2002) h Originally described as anaptychus by the listed authors, but reinterpreted here as the inner chitinous lamella of aptychus-type lower jaw …”

Ammonoid Habitats and Life History

“…The cephalopod/aptychi ratio provides a useful criterion to evaluate the postmortem transport of ammonoids (Olóriz et al 1996;Lukeneder and Tanabe 2002;Reboulet et al 2003;Doguzhaeva et al 2007;Schlögl et al 2011). Accumulated ammonoid shells can be affected by resedimentation processes generating fragmentation ( sensu Fernández-López 1991Fernández-López andMeléndez 1994, 1995;Olóriz et al 1996;Fernández-López et al 1999;Landman and Klofak 2012).…”

“…Lithological and geochemical analyses (e.g., dark laminated shales; CaCO 3 , TOC, S) were combined with investigations of trace fossils, microfossils and macrofossils. This led to the assumption of an invasion of an opportunistic Karsteniceras community (with sexual dimorphism, most probably applicable to the whole leptoceratoid group) during unfavorable conditions (Lukeneder 2003(Lukeneder , 2007Lukeneder and Tanabe 2002). The significant effect of autecological stress, caused either by changes in abiotic environmental factors (oxygen content, salinity, depth) or by synecological stress associated with biotic competitors occupying the same environment was shown by Lukeneder (2003Lukeneder ( , 2007.…”

“…In most cases, the water depth or primary habitat is unknown. A certain likelihood concerning the autochthonous deposition of ammonoid specimens, hence the primary depositional area, is warranted by the preservation of in situ buccal masses located in the body chamber (Schindewolf 1958;Bandel 1988;Frye and Feldman 1991;Summesberger et al 1996;Lukeneder and Tanabe 2002).…”

The jaw apparatus of the Late Cretaceous heteromorph ammonoidPravitoceras

“…In Cretaceous heteromorph ammonoids of the suborder Ancyloceratina, in situ jaws have been reported from 32 species representing 20 genera that are distributed in seven families within three superfamilies (Meek and Hayden, 1864; Kennedy and Cobban, 1976; Kanie et al, 1978; Tanabe et al, 1980b, 2002, 2015; Landman and Waage, 1993; Tanabe and Landman, 2002; Kennedy et al, 2002; Doguzhaeva and Mikhailova, 2002; Lukeneder and Tanabe, 2002; Engeser and Keupp, 2002; Frerichs, 2004; Kruta et al, 2009, 2010, 2011, 2013; Tanabe, 2011). These previous studies reveal that the lower jaws of the Cretaceous Ancyloceratina exhibit wide taxonomic variation in their relative size as compared to the upper jaws, overall morphology, and the degree of development of the outer calcitic covering (Tanabe and Landman, 2002; Tanabe et al, 2015).…”