Navegando por Assunto "Cyprideis"

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Composição isotópica de carbono e oxigênio em ostracodes de depósitos Neógenos da Formação Solimões, estado do Amazonas
(Universidade Federal do Pará, 2011-08-10) SILVA, Melissa do Socorro Fonsêca da; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; https://orcid.org/0000-0003-0276-0575
The Neogene period was marked by important global events such as subsidence, climate seasonality and changes in sea level. In South America, the uplift of the Andean Cordillera was the main event affecting the river system and, consequently, climate and biota of the Amazon during the Miocene. The knowledge of the depositional history contributes to the understanding of many environmental changes occurring in the Miocene. The question exists about possible marine incursions in the Miocene deposits of Western Amazonia, is a favorable scenario for the use of isotope analyze in the shells of ostracods from Solimões Formation. This work is a contribution for paleoenvironmental interpretations of data using the isotopic ratio of C and O in the ostracod shells from the Neogene Solimões Formation aiming to correlation with adjacent areas. The samples are from two cores (1-AS-31-AM e 1-AS-34-AM) and three outcrops (Morada Nova, Aquidabã e Torre da Lua) located in the southwestern state of Amazonas. Among the registered ostracofauna, it was observed that the most representative species for this study belong to the genus Cyprideis (Cyprideis pebasae and Cyprideis machadoi), given its occurrence both in outcrops and cores, as well as the preservation condition they were found. In general, the isotope analysis showed a distribution with only low values for 13C/12C and 18O/16O ratios. The lower depletion of δ18O the sample TL03 of Torre da Lua outcrop and the depth 138,20m of 1AS-31-AM core, reflecting increased evaporation. In these intervals cores increased evaporation occurred over the top where we found the less negative values. However the remaining samples from outcrops and cores presented greater depletion where the decrease of δ13C values possibly indicates humid environment and a reduction in the productivity of these species or organic matter preservation decay and the δ18O values registered lower evaporation.
Desconhecido
Estudo taxonômico do gênero Cyprideis, Formação Pebas, região de Iquitos, Peru
(Universidade Federal do Pará, 2020-12-16) SOUSA, Fabricia Silva de; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; 4546620118003936
The Genus Cyprideis belongs to the Cytherideidae Family and recognized for its ecophenotypic plasticity, influenced by several physical-chemical parameters (eg. Salinity, temperature, hydrochemistry, dissolved oxygen content and energy level) that considerably influence its morphological characteristics. In addition, the various adaptive radiation of the genus is recorded mainly in ancient lake systems, for example, on lake Tanganyika, lake Pannon, PaleoMediterraneo, Caribbean and ―lake Pebas" in the Western Amazon. Previous researches were mainly focused on taxonomic studies that contributed to the recognition of a wide variety of taxa; Cyprideis, however the high intraspecific variability of the genus makes it difficult to recognize some species, since the morphological characteristics between then are very similar, which makes it difficult to recognize the actual number of species that currently occur in the Neogene of Western Amazon. Thus, the present work aims the taxonomic study of the Genus Cyprideis of the Pebas Formation, region of Iquitos (Peru), located between the border west of the Marañon basin and the Iquitos arch. The studied samples come from nine outcrops located on the banks of the Amazon River and the Napo River, which provided recognition of eight genera (Cyprideis, Cypria, Penthesilenula, Heterocypris, Macrocypris, Pelocypris, Perissocytheridea and Skopaeocythere) and 22 species of ostracodes. Among these genera, Cyprideis corresponds to 92.5% of the ostracofauna, with 15 species identified, and three are new. Among these are the first record of Cyprideis anterospinosa, Cyprideis marginuspinosa, Cyprideis retrobispinosa and Cyprideis krsticae for the Pebas Formation, previously recorded only in the Solimões Formation. Additionally, the associations identified allowed to infer a predominantly lacustrine environment, which sazonal variations probably influenced in the salinity rate, without evidence of marine influence; besides inferring the age interval between the Middle Miocene and Late Miocene.
Desconhecido
Taxonomia do gênero Cyprideis (crustacea; ostracoda), Formação Solimões (Mioceno), Bacia do Solimões, estado do Amazonas, Brasil.
(Universidade Federal do Pará, 2023-11-26) FERREIRA, Renato Rafael Martins; RAMOS, Maria Inês Feijó; http://lattes.cnpq.br/4546620118003936; https://orcid.org/0000-0003-0276-0575
Studies of Neogene ostracods from the western Amazonia region, began in 1979, mainly dealing with taxonomic identification, recording a vast, diverse, and endemic fauna, predominantly represented by the Cyprideis genus. This genus is euryhaline and adaptable to the most diverse environmental conditions, such as water salinity level, temperature, and oxygenation, presenting high ecophenotypic plasticity. Thus, the rapid adaptive response of the genus to bioevents, during the deposition of the Pebas System, in the Neogene, in the western region of the Amazonia, led to the development of peculiar morphological characteristics and high intraspecific variation, making it difficult to differentiate species of the genus within this system. Although several authors have studied the Cyprideis genus from the Neogene of Western Amazonia, the number of species is still underestimated. In that context, the present study aimed to survey and taxonomic refinement of the species of this genus, from different boreholes (1AS-1-AM, 1AS-4-AM, 1AS-8-AM, 1AS-32- AM, 1AS-33-AM and 1AS-36-AM) drilled in the western Amazon, west of the state of Amazonas. A total of 9353 valves were counted, in which 30 species and 8 genera of ostracods were identified. Out of these, 22 species belong to the Cyprideis and 8 belong to other genera (Cypria aqualica, Cytheridella danielopoli, ?Paracypris sp., Pellucistoma curupira, Penthesilenula olivencai, Perissocytheridea acuminata, Perissocytheridea ornellasae and Rhadinocytherura amazonensis). The species Cyprideis goeldiensis and Cyprideis javariensis are new and Cyprideis sp. 1 remains in open nomenclature. A new variation of the species Cyprideis matorae was identified and the species Cyprideis santaelenae, originally described for the Pebas Formation, is recorded here for the first time for the strata of the Solimões Formation. The presence of index species allowed the identification of four ostracod zones in core 1AS-32-AM (Cyprideis caraionae Zone, Cyprideis minipunctata Zone, Cyprideis cyrtoma Zone and Cyprideis paralela Zone), compatible with the Grimsdalea palynozone, from the middle to upper Miocene. A new Ostracod Association Zone named Cyprideis cyrtoma Association Zone is here proposed, which has an inferred age in the Tortonian and records the peaks of abundance and diversity of species, especially of the genus Cyprideis, throughout the cores studied herein and in those from previous studies. The great predominance of species of the Cyprideis genus in the studied material, in addition to the associated occurrence of rare freshwater and marine genera, points to a lacustrine, semi-confined, brackish and mesohaline environment.