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GEOREF RECORD

Gastropod egg capsules preserved on bivalve shells from the Lower Jurassic (Hettangian) of Poland

Michal Zaton, Grzegorz Niedzwiedzki and Grzegorz Pienkowski
Gastropod egg capsules preserved on bivalve shells from the Lower Jurassic (Hettangian) of Poland
Palaios (September 2009) 24 (9): 568-577

Abstract

Fossil gastropod egg capsules have rarely been reported from the fossil record. This paper describes gastropod egg capsules preserved exclusively on cardiniid bivalves from Lower Jurassic (Hettangian) deltaic deposits of the Holy Cross Mountains area, central Poland. In most instances, only the bases of the egg capsules are preserved as dark outer rings with hollow cavities inside. Some specimens, however, are preserved as dark circular spots or even shallow depressions on the bivalve molds. The general occurrence, morphology, size and composition of the egg capsules as revealed by Energy Dispersive Spectroscopy (EDS) analyses and elemental mapping point to neritimorphs as the most probable producers. The egg capsules are composed primarily of organic matter with some calcium. Recent neritid gastropods possess aragonitic spherules within the egg capsule walls composed of conchiolin or chitin, which strengthen them and increase their chance of fossilization compared to egg capsules of other gastropods. Recent neritids lay their egg capsules on mollusk shells as well. The occurrence of Early Jurassic egg capsules only on redeposited cardiniid bivalve shells may suggest that the shells were the best medium for egg-capsule deposition. The occurrence of egg capsule bases together with dark circular spots, interpreted as compressed unhatched capsules, suggests that these egg capsules either hatched or were deposited at different times in the same place. The Early Jurassic egg capsules were preserved due to the strengthening role of the carbonate phase within the wall and rapid burial coupled with limited bioturbation in deltaic settings. The prodelta-delta front depositional environment, with high rates of sedimentation by rivers and sediment redistribution by wave and current action, was favorable for preserving these fossils.


ISSN: 0883-1351
Serial Title: Palaios
Serial Volume: 24
Serial Issue: 9
Title: Gastropod egg capsules preserved on bivalve shells from the Lower Jurassic (Hettangian) of Poland
Affiliation: University of Silesia, Department of Stratigraphy and Paleontology, Sosnowiec, Poland
Pages: 568-577
Published: 20090901
Text Language: English
Publisher: Society for Sedimentary Geology, Tulsa, OK, United States
References: 57
Accession Number: 2009-088701
Categories: Invertebrate paleontology
Document Type: Serial
Bibliographic Level: Analytic
Annotation: IGCP Project No. 506
Illustration Description: illus. incl. 2 tables, strat. col., geol. sketch map
N50°52'60" - N50°52'60", E21°21'00" - E21°21'00"
Secondary Affiliation: Warsaw University, POL, PolandPolish Geological Institute, POL, Poland
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by SEPM (Society for Sedimentary Geology), Tulsa, OK, United States
Update Code: 200948
Program Name: IGCPInternational Geological Correlation Programme
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