Siberian Oyster Fossils - the Key to Reconstructing the Environment of the Ancient Seas

Igor Kosenko, Senior Lecturer, Novosibirsk State University Historical Geology – Paleontology Section at the Geology and Geophysical Department, Research Fellow, Trofimuk Institute of Oil and Gas Geology and Geophysics SB RAS, has conducted systematic research of the taxonomy, paleoecology and isotope-geochemical composition of Late Jurassic-Early Cretaceous oyster shells. These mollusks are valuable for paleontological research and of interest to the scientific community.

Igor Kosenko talked about his research:

On the one hand, oysters have very high mutability because when they are alive they are cemented to a solid substrate. This makes it difficult to systematically study both ancient and modern oysters, and makes them unsuitable for determining the age of the rocks. This is one of the main tasks in paleontology and stratigraphy. Oysters have powerful calcite shells that are resistant to post-sedimentation changes so they are interesting for isotope-geochemical research. You can determine the composition of the sea water in which these mollusks lived more than hundreds of millions of years ago by studying the distribution of elements and stable isotopes of carbon and oxygen in their shells.

The results from the Novosibirsk scientists research were presented at the Fifth Symposium on the IGCP 632 Program (International Program for the Global Correlation of UNESCO, Project 632), which took place in October at the Museum of Northern Arizona in America. Igor Kosenko’s report, "Upper Jurassic and Lower Cretaceous Oysters (Bivalvia, Ostreoidea) from Northwest Western Siberia and North of Eastern Siberia: Taxonomy, Paleoecology and Geographic Distribution”, presented the taxonomy problem in Jurassic and Cretaceous oysters and ways to solve this problem.

The scientist also talked about system improvements in Mesozoic oysters in Siberia and their palaeobiogeographic significance. This was established on the basis of results obtained from a revision of their system, and on new isotopic data that made it possible to reconstruct paleotemperatures. These paleotemperatures came from the most northern of the known Jurassic oyster shells and was registered at 18-20 degrees Celsius for Northern Siberia at the end of the Jurassic period. This indicates a very warm climate, taking into account the high paleolatitude of the location of the mollusks that were studied.

Igor Kosenko's article on systemization problems of Mesozoic oysters appeared on November 15 in the Acta Palaeontologica Polonica journal. The scientist reconsiders the existing classification of Late Jurassic-Early Cretaceous Siberian Oysters. For example, oysters with thick shells that were previously ascribed to the genus Liostrea, were classified as genus Pernostrea. A comparison of the morphology of the shells of the genera Deltoideum and Pernostrea shows that they are morphologically close to each other, but in many respects, differ from the genus Gryphaea. This makes it possible to introduce a new tribune of oysters, Pernostreini trib. nov. The updated classification will become the basis for further research and will clarify the existing paleobiogeographical reconstructions, as well as clarifying the specific evolutionary features of oysters in the Jurassic-Cretaceous period.

Details of the study: