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New species of ostracods from the Tremadocian in the northwest region of Argentina are described. These are among the earliest well−documented records of ostracods, which shed new light onto the early diversification of the group. The described fauna consists of seven species, five of which are new: Saltite uchuy sp. nov., Saltite kuraq sp. nov., Conchoprimitia? iglesiasi sp. nov., Orechina violetae sp. nov., and Orechina catalinae sp. nov. The fauna consists primarily of soanellids, a non−dimorphic family of palaeocopids, and of binodicopids. One factor leading to diversification of the group in this region may have been the complex configuration of the northwest basin, which had a restricted pattern of circulation. The distribution of the first ostracods is largely restricted to Gondwana and peri−Gondwana regions. Accordingly, it is possible to envision that the origin or at least an important radiation of the group was centred in this region. Both the Soanellidae and the genus Orechina would have originated in Gondwana and would have become widespread later during the Middle Ordovician. The Tremadocian fauna located in Argentina show significant affinities with fauna located in the warm−water setting of the east Gondwana, mainly in Australia and China.
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Ostracods from the Purbeckian of Central Poland

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The recent stratigraphical and paleontological research in the Jurassic/Cretaceous boundary sequence in central Poland confirmed a validity of the hitherto accepted local ostracod zonation. Six ostracod zones have been compared with the zones distinguished in England, France and Germany. From 51 ostracod species and subspecies recorded in the sequence of superposing marine-brackish and brackish-fresh-water sediments the author describes the following new species and subspecies: Limnocythere biverrucosa, Timiriasevia polonica, Cypridea aleksandrowiensis, C. wandae, C. binodosa polonica, C. dunkeri spinosa, C. granulosa polonica, C. lata polonica, C. obliqua polonica, C. prealta iuvencula and C. tumescens granulosa.
This paper includes a check-list of Recent Svalbard marine ostracods based on published sources and on diploma theses as well as some new studies. This is the first study of this group of crustaceans from Hornsund. A total of 41 species belonging to 12 families were collected at 55 sampling stations from dredged sediments. Seven species are reported for the first time from the Svalbard Archipelago. Polycope orbicularis Sars is the most abundant species in the present fauna. Species compositions of Hornsund and the Liefde- fjorden are seen to have the highest similarity (S = 50.6).
Ostracods from Admiralty Bay on King George Island (South Shetland Islands) represent 29 podocopid species, belonging to 19 genera, one cladocopid and six myodocopid species. They were recovered from Recent marine and/or glacio-marine sediment samples from water depths of up to 520 m. These ostracods constitute a variable assemblage, which is overall typical for the Antarctic environment. Shallow-water assemblages tend to be more variable in terms of frequencies and species richness than deep-water assemblages. The later are low in numbers and remain relatively high diversities. Overall, no linear relation between ostracod assemblage-composition and environmental features analyzed was recognized.
The ostracode Lavachilina evae gen. et sp. nov. is described from the Arenig of Western Russia. Its carapace possesses a unique discontinuous velum, developed at both ends as a narrow spinose ridge. The systematic position of L. evae is uncertain. Its character set shows mostly palaeocope affinities but also some features of leiocopes. L. evae is tentatively assigned to the palaeocope family Oepikellidae, possibly representing an early member of that family. Although L. evae existed contemporaneously with palaeocopes such as Laccochilina, it does not appear to be closely related to these early eurychilinoids.
In subsequent co-infections of Sobolevicanthus gracilis and Fimbriaria czaplinskii an elimination of the majority of specimens of the first species by the next one has been found at the early stage of development. This did not depend on the fact, which species was the first. In concurrent control co-infections of larvae of both species mentioned above developed simultaneously and correctly. It seems to testify the existence of interspecific competition expressed by a peculiar sensibility of larvae at their early stages of development (3rd to 5th day post infection). The longer the larvae of the first species develop the fewer of them become eliminated by the next one.
The study was carried out in the main branches of the Lower Oder River, differentiated in terms of sediments composition. The aim was performing a comparative studies on the differences in Ostracoda fauna inhabiting various types of sediments. Following bottom sediments were distinguished: hard, sapropel/hard, sapropel and Chironomidae mat. The packet of CANOCO v.4.5 programs was used to investigate the interdependence between the species composition and environmental parameters. Eighteen taxa were found of which 16 were identified to the species level. It was a comparatively high number considering the fact that the samples were collected exclusively from the benthic zone and solely from the main river bed, without floodplain. Physocypria kraepelini was an eudominant and Darwinula stevensoni and Cypria ophtalmica were dominants. The samples collected from the sapropel were characterised by the highest density. The case of hard sediments the status of domination was retained as above, but there appeared a new dominant, i.e. Potamocypris unicaudata . The most unique structure of domination was observed in the case of Chironomidae mat, with Limnocythere inopinata as an eudominant and Cypridopsis vidua and P. unicaudata as dominants. As for the species diversity, the hard sediments were characterised by the highest value of Shannon-Wiener Diversity Index, the sapropel/hard sediment was the lowest. The type of river bottom to a great extent affects the density and taxonomic composition of the Ostracoda in rivers. The waters of the Oder River, rich in oxygen, provide favourable conditions for the development of ostracods even on the surface of sapropel sediment.
Full detailed descriptions of the two species of Obtusoecia, one of two planktonic halocyprid ostracod genera that are bipolar, demonstrate that the taxonomic separation of these two forms formerly considered to be conspecific, is valid. The segregation of the genus from Porroecia is also validated. The value of characters of limbs other than the first and second antennae particularly in defining halocyprid genera is emphasised. Zoogeographical distributions of the two species based on comprehensive compilations of both published and unpublished data show that O. obtusata is confined to the North Atlantic, whereas O. antarctica has an Antarctic circumpolar distribution. Detailed bathymetric profiles show that O. obtusata is a shallow mesopelagic species that is overwhelmingly dominant at depths of 50-200 m in subpolar seas, and shows limited ability to submerge at lower depths, so that it is restricted to seas that have a marked seasonal cycle of turn-over and stratification. It is postulated that the bathymetric distributions of the two species are similar, also that O. antarctica is more likely to be ancestral to O. obtusata than vice versa.
Morphological variability in lacustrine ostracode Cytherissa lacustris (Sars) expressed as differences in carapace size and nodation pattern as well as the carapace preservation were investigated in five physiographically similar Polish lakes. Individuals of the populations investigated appeared to be considerably longer and less variable than individuals of the previously studied European, Arctic and North-American populations. Considerable variation of the carapace size was found but no visible influence of the selected environmental parameters such as the depth of a lake, grain size and organic matter of sediment could be established. The populations investigated were homogeneous in respect of nodation pattern but in respect of degree of carapace preservation there were recognized two significantly different homogeneous sets of populations.
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