Über den Kieferapparat der Lytoceratacea (Ammonoidea)

Ammonoid Buccal Mass and Jaw Apparatus

“…10.5d; Phyllopachyceras: Tanabe and Landman 2002;Tanabe et al 2013) and Lytoceratina ( Tetragonites, Gaudryceras, Aanagaudryceras; F ig. 10.5e, 10.7a, b; Table 10.1; Tanabe et al 1980aTanabe et al , 2012Lehmann et al 1980;Kanie 1982;Tanabe and Landman 2002). In the two phylloceratids, the lower jaw is slightly larger than the upper jaw (Table 10.2).…”

“…10.9 and 10.12). The rhynchaptychus-type jaw apparatuses are known from the Late Cretaceous Phylloceratina (Tanabe and Landman 2002;Tanabe et al 2013) and Lytoceratina (Tanabe et al 1980aKanie 1982;Lehmann et al 1980;Tanabe and Landman 2002). In addition, wholly chitinous lower jaws of the Early Jurassic Phylloceras and Lytoceras were described as anaptychi (Schmidt 1928;Hauff 1953;Lehmann 1990).…”

Ammonoid Habitats and Life History

“…Westermann (1996) noted that besides the micro and mesophagy documented by crop/stomach contents, macrophagy and even duraphag ous strategies might have also been present in ammonoids (Schindewolf 1958;Lehmann et al 1980;Tanabe 1983;Nesis 1986;Tanabe and Fukuda 1987;Lehmann and Kulicki 1990;Hewitt 1993;Seilacher 1993;Keupp 2007). Westermann (1996) suggested that most ammonoids belonged to the pelagic food-web.…”

“…Nonetheless, the implosion depth of a Nautilus shell does not represent an actual depth limit of living animals. Direct observations using a remote camera and capture records using baited traps have demonstrated that the optimal habitat depth of Nautilus ranges from 150 to 300 m in Palau and from 300 to 500 m in Fiji (Saunders 1984;Hayasaka et al 1987), whereas the shell implosion depth of Nautilus is about 800 m (Kanie et al 1980). Although these analyses in functional morphology provided valuable suggestions and limitations for considering ammonoid ecology, reasonable and unanswered questions remain for future discussion.…”

Ammonoid Life and Habitat

“…Many problems of dietary and feeding habits for the diversely shaped buccal organs remain essentially unsolved, even for most extant cephalopods (Nesis, 1986(Nesis, , 1987Lehmann, 1988). Of particular interest are the aptychus-type mandibles (including anaptychi) present in many but by no means all Mesozoic ammonoids, and the rhynchaptychus-type mandibles of the Lytoceratina (Lehmann et al, 1980). A consensus appears to be that, among the former, the uncalcified anaptychi functioned mainly as feeding organs, i.e., as lower mandibles or, perhaps, an elastic "pump" during suction feeding (Seilacher, 1993); the thickly calcified aptychi (Lamellaptychus, Laevaptychus, Punctaptychus) functioned primarily as opercula (Schindewolf, 1958; Lehmann and Kulicki, 1990;Seilacher, 1993).…”