Exceptionally Preserved Late Jurassic Gastropod Egg Capsules

Abstract

Exceptionally preserved, phosphatized gastropod egg capsules from the uppermost Jurassic (upper Volgian) in Central Russia are reported. The egg capsules were attached to the inner side of the shell wall of empty body chambers of two ammonites. Due to phosphatization, the egg capsules retained their original morphology preserving both the lower attachment base and upper hemispherical cover. Comparison with recent and fossil gastropod egg capsules indicates that these were not produced by neritimorphs, the egg capsules of which are known from the Lower Jurassic and Upper Cretaceous. Since these fossil egg capsules share many similarities with those produced by some recent rissoids and muricid neogastropods, it is evident that they were produced by some representatives of Caenogastropoda. The abundant filamentous microbial structures, as well as micron-sized apatite globules, preserved inside the egg capsules suggest that phosphatization processes were mediated by microbial consortia under anaerobic and low-pH conditions.

A possible terrestrial egg cluster in driftwood from the Lower Jurassic (Late Pliensbachian) of Buttenheim (Franconia, Germany)

“…Beside the below mentioned findings in the clay pit south of Buttenheim, fossil record of gastropod egg capsules is "extremely poor due to their low fossilization potential" (Zatoń and Mironenko 2015b, p. 1). The known findings include imprints on bivalve shells, on gastropod shells or on ammonite body chambers from the Lower Jurassic (Kaiser and Voigt 1977;Kaiser and Voigt 1983), the Upper Jurassic (Zatoń and Mironenko 2015b) or the Cretaceous (Zatoń et al 2013;Zatoń et al 2017) as well as one three-dimensional record in mid-Cretaceous amber (Xing et al 2021). To our knowledge, there are only two examples of pyritized gastropod eggs on driftwood (Riegraf and Schubert 1991;Schubert et al 2008).…”