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Vol 51, No 13 (2017)
- Year: 2017
- Articles: 4
- URL: https://journals.rcsi.science/0031-0301/issue/view/10212
Article
On new Jurassic Rissooidea and Zygopleuroidea convergently similar to them (Gastropoda: Pectinibranchia)
Abstract
A new genus, Boreomica gen. nov., is established; it comprises small-sized gastropods widespread in the Jurassic of the Russian Plate, the taxonomic position of which was ambiguously treated by previous authors. The new genus is assigned to the family Rissoidae. The species composition and stratigraphical and geographical distribution of the genus and its species are discussed. From the Jurassic of the Russian Plate, Callovian Boreomica exigua (Gerasimov, 1992), the type species of the genus, and Kimmeridgian–Volgian Boreomica undulata (Tullberg, 1881), and members of the genus without species status from the Bathonian and Upper Oxfordian are described. Conchological polymorphism of species connected with their eurybiontic characteristics is discussed. Based on the study of samples of the species B. exigua from different types of facies, two subspecies are recognized, B. exigua exigua and B. exigua arenosa subsp. nov. Finds of gastropods morphologically similar to Boreomica are discussed: Katosira? sp. from Mitta et al., 2004, “Procerithium?” volgense Gerasimov, 1955, “Eulima” pusilla Tullberg, 1881, and “Hudlestonella” caleptra sensu Gerasimov, 1992 are considered. It is concluded that E. pusilla and H. caleptra are unknown zygopleurids, Katosira? sp. is likely a poorly preserved Katosira, and “Procerithium?” volgense is represented by a mixture of several species belonging to different genera: several zygopleurid species, the rissoids Boreomica undulata and Bralitzia. Shells of P. volgense in the P.A. Gerasimov’s collection from the Craspedites nodiger Zone are described as Laevipleura sp.
1375-1394
Mineralogical–geochemical characteristics of the bone detritus of Pleistocene mammals as a source of paleontological information
Abstract
A complex mineralogical geochemical study of the bone detritus of large Pleistocene mammals inhabiting the Pechora Fore-Urals, the northernmost European part of their geographical range, is performed for the first time. The chemical composition, microstructure, content of 50 chemical elements are analyzed. The taphonomy of bones, extent of preservation of their initial properties, character and extent of fossilization are considered. The ultraporosity in the nanometer range is examined for the first time; it is established that it can be a marker of epigenetic changes in bones, beginning from the earliest stage of their fossilization. Based on X-ray structure and spectroscopic data, bone bioapatite is referred to carbonate–apatite of the B type. The results of thermal, chromatographic, and spectroscopic studies of collagen extracted from the bones of Pleistocene animals are discussed for the first time. The general trend of chemical degradation of bone proteins during fossilization is determined. The amino acid composition of bone collagen, the isotope composition of C, O, and N in biomineral and organic components of bones in the course of two-stage mass-spectrometer analysis of a complex sample are analyzed for the first time. Based on isotope-geochemical data conclusions concerning the diet and paleoclimatic and paleolandscape conditions of Pleistocene mammals are made.
1395-1421
On the nature and origin of cellular complexity: The combinatorial–eukaryogenetic scenario
Abstract
The ideas on the nature and origin of the cell nucleus published by K.S. Merezhkowsky in his book The Theory of Two Plasms as the Basis of Symbiogenesis, a New Study on the Origins of Organisms (1909) are still relevant. In this book, Merezhkowsky (1909, p. 86) wrote, “Part of my theory related to the nucleus, its nature and origin will be the subject of a separate paper, which will present facts serving as the basis for the ideas, which are here only touched upon briefly.” For various reasons, he was not able to publish the paper intended. Therefore, I here attempt to interpret Merezhkowsky’s original concepts on the nature and origin of the cell nucleus in a modern context.
1422-1439
Halophilic-psychrotrophic bacteria of an Alaskan cryopeg—a model for astrobiology
Abstract
Cryopegs, lenses of hypersaline unfrozen soil or water within permafrost, are a model for astrobiology, since free water can only be present on cryogenic bodies and planets in the form of brine. In this paper the diversity of aerobic halophilic-psychrotrophic microorganisms from an Alaskan cryopeg (Barrow Cape) were studied and described for the first time. This cryopeg is characterized by a constant subzero temperature (–7°C), high salinity (total mineralization is about 120 g/L) and isolation from external influences for a geologically significant period of time. Our study has revealed a large number of microorganisms capable of growth at low temperature (4°C) in a wide range of salinities from 5 to 250 g/L of NaCl, the latter being 3 times higher than the natural salt concentration of the Alaskan cryopeg. The microorganisms identified are comprised of four major phyla: Actinobacteria (genera Brevibacterium, Citricoccus, Microbacterium), Firmicutes (genus Paenibacillus), Bacteroidetes (genus Sphingobacterium), and Proteobacteria (genus Ochrobactrum).
1440-1452