Fossiler Schneckenlaich in Ammonitenwohnkammern

Abstract

Three kinds of gastropod eggs are described from the Middle Liassic (Pliensbachian) of northern Germany. Circular, netlike or honeycomb patterns on the innerside of the living chambers of the ammonite Pleuroceras spinatum (Brugière) and two Lytoceratids are compared with spat of Recent Gastropoda (Neritaceac and Columbellidae [?]). Other interpretations, such as ooids, conelles, faecal pellets, or eggs of ammonites are excluded. The striking likeness between spat of Recent Columbellidae and incrusting cheilostomatous membranimorph bryozoans (Conopeum) is pointed out. On the muddy sea floor, open lamellibranch shells and living chambers of ammonites offered a suitable hard and sheltered substrate for gastropod spawn.Gastropoda, Neritacea, eggs, ammonite living chambers, Cheilustomata, faecal pellets, Jurassic, Pliensbachian, NW Germany. Aus dem norddeutschcn Lias γ‐δ (Pliensbachium) werden drei Katcgorien von Gastropodenlaich be‐schrieben. Es handelt sich teils um isolierte kreisrunde oder wabenbis hetzartige Strukturen auf der Innenwand von Ammonitenwohnkammern, bcsonders von Pleuroceras spinatum (Brugière) und zwei Lytoceratiden. Die Deutung als Gastropodenlaich gründet sich auf den Vergleich mil rezenten Eiablagen von Gastropoden (Neriten und Columbellidae [?]). Andere Deutungsmöglichkeiten (Ooide, Conellcn, Kotpillcn, Ammoniteneier) werden ausgeschlossen. Auf die verblüffende Áhnlichkeit zwischen rezentem Columbellidae‐Laich und inkrustierenden cheilostomcn membranimorphen Bryozoen (Conopeum) wird hingewiesen. Die Innenráume von Molluskenschalen (Ammonitenwohnkammern, klaffende Schalen von Lamellibranchiaten) boten auf schlammigen Weichböden Substratlaichern unter den Gastropoden offcnbar günsttge Laichgelegenheiten.

Gastropod egg capsules preserved on an Early Cretaceous ammonite from Daghestan, Russia

“…They are also very similar with respect to shape and arrangement to other fossil egg capsules interpreted as originated from neritimorph gastropods ( Fig. 3DeE; see also Kaiser and Voigt 1983;Zato n et al, 2009Zato n et al, , 2013. The main difference, however, is the very small size of the Early Cretaceous capsules in comparisons with other fossil and Recent examples (Fig.…”

“…This is not an isolated case, as in the past Kaiser and Voigt (1983) also noted gastropod egg capsules, including those produced by neritimorphs, preserved on the mould of Early Jurassic (Pliensbachian) ammonites from Germany. Gastropod egg capsules have also been found within bivalve (Kaiser and Voigt, 1977 However, due to their large size and stability on the sea-floor, the ammonite shells seemed to be very good spawning grounds.…”

The operculum of Otostoma Retzii (Nilsson, 1827) (Gastropoda, Neritidae; Late Cretaceous) and its phylogenetic significance

“…The original deposition of the egg capsules by neritid gastro− pods within the empty shell is reminiscent of other fossil exam− ples in which egg capsules were laid down in vacant body cham− bers of ammonites (Kaiser and Voigt 1983), or the interiors of bivalve shells (Kaiser and Voigt 1977;Zatoń et al 2009). These cryptic locations would have provided protection for the eggs and the newly hatched gastropods.…”

“…Today, egg capsules are produced by various caenogastropods and neritimorphs. Those produced by the latter group are tough, flattened capsules that are oval or spher− ical in shape, composed of conchiolin as well as chitin (e.g., Adegoke et al 1969;Bandel 1982;Kaiser and Voigt 1983;Soliman 1987;Kano and Fukumori 2010). Egg capsules may be reinforced by either aragonite or calcite crystals (e.g., Bandel 1982; Kano and Fukumori 2010), increasing the likelihood of fos− silisation (see Voigt 1977, 1983;Zatoń et al 2009).…”

Exceptionally Preserved Late Jurassic Gastropod Egg Capsules

“…Among aquatic gastropods, only representatives of Neritimorpha (Neritidae) produce tough, leathery egg capsules which, although composed of conchiolin and chitin (e.g., Adegoke et al 1969;Bandel 1982;Kaiser and Voigt 1983;Soliman 1987;Kano and Fukumori 2010;Wysokowski et al 2014), are additionally reinforced by calcium carbonate (aragonitic or calcitic) crystals (e.g., Bandel 1982;Kano and Fukumori 2010;Fukumori et al 2013), which may increase their fossilization potential. The egg capsules of neogastropods are also tough; however, they are composed chiefly of proteins and carbohydrates (e.g., Tamarin and Carriker 1967;Soliman 1987;Hawkins and Hutchinson 1988;Rawlings 1999 and literature cited therein), so their potential to be fossilized is significantly lower.…”