Taxonomy and zoogeography of the mesozoic cytherurid ostracoda from West-Central Argentina

The status of thirty four species of the cytheroidean ostracod family Cytheruridae from the Neuquén Basin, west-central Argentina is reviewed. These species belong to the following nine genera: Eucytherura Müller, ranging in this study from Pliensbachian to Valanginian and represented by fourteen species; Kangarina Coryell and Fields, Aalenian-Bajocian, with a single species; Acrocythere Neale, Hauterivian, one species; Paranotacythere Bassiouni, Berriasian, two species; Procytherura Whatley, Pliensbachian to Hauterivian, twelve species; Cytheropteron Sars, Aalenian-Bajocian, one species: Eocytheropteron Alexander, Hauterivian, one species; Paradoxorhyncha Chapman, Aalenian-Bajocian, one species; and Paracytheridea Müller, Berriasian, one species. Of the three subfamilies of the Cytheruridae, the Cytherurinae, with thirty species are by far the most numerous and abundant throughout the study. The other two subfamilies, the Cytheropterinae are represented by three species and the Paracytherideinae by a single species of the nominative genus. Several of the species are very widely distributed geographically and have, for example, also been recorded from Europe; others indicate close links with South Africa and Australia. The stratigraphical ranges of certain genera have been extended as a result of this study. For example, Kangarina has not previously been recorded below the Cretaceous. The Cytheruridae are clearly the most diverse cytheroidean ostracodes in the Mesozoic of the Neuquén Basin and are more diverse than all other groups of ostracodes combined. Four new species, Eucytherura tessae, Eucytherura yunga, Procytherura amygdala and Eocytheropteron immodicus are described. Eucytherura guillaumeae nom. nov. for Eucytherura tuberculata Brenner and Oertli and Eucytherura paranuda nom. nov. for Eucytherura nuda (Brand) are proposed.Facultad de Ciencias Naturales y Muse

Taxonomy and zoogeography of the mesozoic cytherurid ostracoda from West-Central Argentina

The status of thirty four species of the cytheroidean ostracod family Cytheruridae from the Neuquén Basin, west-central Argentina is reviewed. These species belong to the following nine genera: Eucytherura Müller, ranging in this study from Pliensbachian to Valanginian and represented by fourteen species; Kangarina Coryell and Fields, Aalenian-Bajocian, with a single species; Acrocythere Neale, Hauterivian, one species; Paranotacythere Bassiouni, Berriasian, two species; Procytherura Whatley, Pliensbachian to Hauterivian, twelve species; Cytheropteron Sars, Aalenian-Bajocian, one species: Eocytheropteron Alexander, Hauterivian, one species; Paradoxorhyncha Chapman, Aalenian-Bajocian, one species; and Paracytheridea Müller, Berriasian, one species. Of the three subfamilies of the Cytheruridae, the Cytherurinae, with thirty species are by far the most numerous and abundant throughout the study. The other two subfamilies, the Cytheropterinae are represented by three species and the Paracytherideinae by a single species of the nominative genus. Several of the species are very widely distributed geographically and have, for example, also been recorded from Europe; others indicate close links with South Africa and Australia. The stratigraphical ranges of certain genera have been extended as a result of this study. For example, Kangarina has not previously been recorded below the Cretaceous. The Cytheruridae are clearly the most diverse cytheroidean ostracodes in the Mesozoic of the Neuquén Basin and are more diverse than all other groups of ostracodes combined. Four new species, Eucytherura tessae, Eucytherura yunga, Procytherura amygdala and Eocytheropteron immodicus are described. Eucytherura guillaumeae nom. nov. for Eucytherura tuberculata Brenner and Oertli and Eucytherura paranuda nom. nov. for Eucytherura nuda (Brand) are proposed.Facultad de Ciencias Naturales y Muse

Ostracoda

Los ostrácodos constituyen una clase de crustáceos de hábitos acuáticos y morfológicamente muy conservadores, fácilmente identificables por su pequeña talla y la presencia de un exoesqueleto o caparazón bivalvo, de naturaleza quitinoso-calcárea, que cubre completamente las partes blandas. El tamaño de un ostrácodo adulto oscila entre los 0,15 y los 2-3 mm, si bien algunas especies de agua dulce alcanzan los 8 mm; las de Gigantocypris miden hasta 32 mm y algunas paleozoicas del género Leperditia, llegaron a los 50 mm. El caparazón está compuesto por carbonato de calcio en forma de calcita con proporciones variables de magnesio, recubierto externamente por una capa de quitina. Lo integran piezas o valvas laterales, ubicadas a ambos lados del cuerpo y articuladas dorsalmente mediante una charnela. En caso de agresión o perturbación, el individuo se retrae completamente en el caparazón, el cual se cierra mediante la acción de músculos aductores.Facultad de Ciencias Naturales y Muse

Contribution to the taxonomy, distribution and paleoecology of the early representatives of Penthesilenula Rossetti & Martens, 1998 (Crustacea, Ostracoda, Darwinulidae) from Argentina, with the description of a new species

Early Mesozoic Argentinian darwinuloids, now re-assigned to the genus Penthesilenula (incae group), are described and illustrated. These records seem to constitute the oldest known for the genus. The close similarities between the studied species and those described from eastern Asia enlarge the geographical distribution of Penthesilenula (incae group), which, although restricted to the southern Hemisphere in Recent and Holocene times, may have had a wider distribution in the past. Additional information on the paleoecology, plus a preliminary account on the distribution of darwinulid species from Argentina are also offered. One new species is described: Penthesilenula loana sp. nov.Facultad de Ciencias Naturales y Muse

Taxonomy and zoogeography of the mesozoic cytherurid ostracoda from West-Central Argentina

The status of thirty four species of the cytheroidean ostracod family Cytheruridae from the Neuquén Basin, west-central Argentina is reviewed. These species belong to the following nine genera: Eucytherura Müller, ranging in this study from Pliensbachian to Valanginian and represented by fourteen species; Kangarina Coryell and Fields, Aalenian-Bajocian, with a single species; Acrocythere Neale, Hauterivian, one species; Paranotacythere Bassiouni, Berriasian, two species; Procytherura Whatley, Pliensbachian to Hauterivian, twelve species; Cytheropteron Sars, Aalenian-Bajocian, one species: Eocytheropteron Alexander, Hauterivian, one species; Paradoxorhyncha Chapman, Aalenian-Bajocian, one species; and Paracytheridea Müller, Berriasian, one species. Of the three subfamilies of the Cytheruridae, the Cytherurinae, with thirty species are by far the most numerous and abundant throughout the study. The other two subfamilies, the Cytheropterinae are represented by three species and the Paracytherideinae by a single species of the nominative genus. Several of the species are very widely distributed geographically and have, for example, also been recorded from Europe; others indicate close links with South Africa and Australia. The stratigraphical ranges of certain genera have been extended as a result of this study. For example, Kangarina has not previously been recorded below the Cretaceous. The Cytheruridae are clearly the most diverse cytheroidean ostracodes in the Mesozoic of the Neuquén Basin and are more diverse than all other groups of ostracodes combined. Four new species, Eucytherura tessae, Eucytherura yunga, Procytherura amygdala and Eocytheropteron immodicus are described. Eucytherura guillaumeae nom. nov. for Eucytherura tuberculata Brenner and Oertli and Eucytherura paranuda nom. nov. for Eucytherura nuda (Brand) are proposed.Facultad de Ciencias Naturales y Muse

Biostratigraphy and palaeoenvironment of the Agrio Formation (Lower Cretaceous), Mendoza Province, Neuquén Basin, Argentina

Se caracteriza bioestratigráfica y paleoambientalmente a la Formación Agrio en la sección Cuesta del Chihuido, en el sur de la Provincia de Mendoza (35º45'S/69º34'W), Argentina. Se han reconocido treinta y siete especies de nanofósiles, treinta y cuatro de foraminíferos y seis de ostrácodos. Los nanofósiles permiten asignar la edad al Valanginiano superior-Hauteriviano superior e incluir la asociación en las Zonas CC4A y CC4B. En la base de la sección, la asociación del foraminífero bentónico Epistomina loncochensis Ballent y radiolarios sugieren condiciones altamente eutróficas en la columna de agua con abundante desarrollo de microbiota y fondos deficitarios en oxígeno. Hacia la parte media, la diversidad de foraminíferos lagénidos y de nanofósiles señala condiciones marinas normales de plataforma, con aguas claras y bien oxigenadas. Abundantes polimorfínidos, spirillínidos e involutínidos hacia el techo de la sección indican una marcada tendencia a la somerización. Las intercalaciones calcáreas-pelítico arenosas que representan depósitos tempestíticos distales contienen una microfauna alóctona de foraminíferos adheridos y caparazones adultos de ostrácodos cytheroideos.A bioestratigraphical and palaeoenvironmental study of the Agrio Formation, at the Cuesta del Chihuido section, southern Mendoza Province (35º45'S/69º34'W), Argentina, is presented. Thirty seven species of nannofossils, thirty four of foraminifers and six of ostracods have been recognized. Nannofossils association corresponding to Zones CC4A y CC4B indicates an Upper Valanginian-Upper Hauterivian age. At the base of the section, the presence of the benthonic foraminifer Epistomina loncochensis Ballent and radiolaria suggests eutrophic conditions of surface waters and oxygen depressed sea-bottom conditions. In the middle part of the section, diversity of lagenid foraminifers and nannofossils indicates a shelf and nearshore environment with clear and well-oxygenated waters. Abundant polymorphinids, spirillinids and involitinids towards the top of the section corroborate a general regressive tendency. Mudstones and silty-sandstone intercalations containing allochthonous adherent foraminifers and adult carapaces of cytheroid ostracods represent distal storm deposits.Facultad de Ciencias Naturales y Muse

Biostratigraphy and palaeoenvironment of the Agrio Formation (Lower Cretaceous), Mendoza Province, Neuquén Basin, Argentina

Se caracteriza bioestratigráfica y paleoambientalmente a la Formación Agrio en la sección Cuesta del Chihuido, en el sur de la Provincia de Mendoza (35º45'S/69º34'W), Argentina. Se han reconocido treinta y siete especies de nanofósiles, treinta y cuatro de foraminíferos y seis de ostrácodos. Los nanofósiles permiten asignar la edad al Valanginiano superior-Hauteriviano superior e incluir la asociación en las Zonas CC4A y CC4B. En la base de la sección, la asociación del foraminífero bentónico Epistomina loncochensis Ballent y radiolarios sugieren condiciones altamente eutróficas en la columna de agua con abundante desarrollo de microbiota y fondos deficitarios en oxígeno. Hacia la parte media, la diversidad de foraminíferos lagénidos y de nanofósiles señala condiciones marinas normales de plataforma, con aguas claras y bien oxigenadas. Abundantes polimorfínidos, spirillínidos e involutínidos hacia el techo de la sección indican una marcada tendencia a la somerización. Las intercalaciones calcáreas-pelítico arenosas que representan depósitos tempestíticos distales contienen una microfauna alóctona de foraminíferos adheridos y caparazones adultos de ostrácodos cytheroideos.A bioestratigraphical and palaeoenvironmental study of the Agrio Formation, at the Cuesta del Chihuido section, southern Mendoza Province (35º45'S/69º34'W), Argentina, is presented. Thirty seven species of nannofossils, thirty four of foraminifers and six of ostracods have been recognized. Nannofossils association corresponding to Zones CC4A y CC4B indicates an Upper Valanginian-Upper Hauterivian age. At the base of the section, the presence of the benthonic foraminifer Epistomina loncochensis Ballent and radiolaria suggests eutrophic conditions of surface waters and oxygen depressed sea-bottom conditions. In the middle part of the section, diversity of lagenid foraminifers and nannofossils indicates a shelf and nearshore environment with clear and well-oxygenated waters. Abundant polymorphinids, spirillinids and involitinids towards the top of the section corroborate a general regressive tendency. Mudstones and silty-sandstone intercalations containing allochthonous adherent foraminifers and adult carapaces of cytheroid ostracods represent distal storm deposits.Fil: Ballent, Sara Cristina. Universidad Nacional de La Plata; ArgentinaFil: Concheyro, Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Sagasti, Guillermina. Repsol-YPF Madrid; Españ

Triassic age of the continental Pular Formation, Sierra de Almeida, Antofagasta, northern Chile

In this contribution, we present a reassessment of the Pular Formation age (Sierra de Almelda, Antofagasta) that in previous papers was attributed to either the Late Paleozoic or Triassic. At Quebrada del Medio, the Pular Formation includes a 379-meter-thick stratigraphic section formed from base to top by conglomerates, sandstones, black bituminous shales and limestones, tuffaceous sandstones and a poorly welded ignimbrite that , accumulated in fluvial and lacustrine environments. A multidisciplinary study of the flora and fauna was undertaken. The existence of diagnostic Gondwana microflora and macroflora allows attributing a Middle Triassic to early Late Triassic age to the Pular Formation.Facultad de Ciencias Naturales y Muse

Micropaleontology of the Agrio Formation (Lower Cretaceous) in different areas of the Neuquén Basin

Se analizan conjuntamente la nanoflora y microfauna de foraminíferos bentónicos y ostrácodos de la Formación Agrio, en tres sectores de la cuenca Neuquina, a fin de establecer las edades involucradas y considerar las variaciones paleoambientales. En el sector norte de la cuenca se reconocen las sedimentitas más antiguas de la Formación Agrio, asignadas con amonites al Valanginiano inferior y portadoras de una microfauna monoespecífica de Epistomina loncochensis Ballent que indica ambientes disóxicos. Suprayacen limolitas con una microfauna variada de foramíniferos de plataforma marina normal, las que son reemplazadas por microfaunas empobrecidas vinculadas a somerización. La edad de la secuencia definida con nanofósiles es valanginiana tardía - hauteriviana tardía. Para posiciones medias y sur de la cuenca, la edad que indica la nanoflora de la Formación Agrio nuevamente queda comprendida entre el Valanginiano superior y el Hauteriviano superior. La microfauna hallada sugiere frecuentes oscilaciones eustáticas entre ambientes de plataforma y costaneros. En el sector austral de la cuenca, una asociación poco diversa de foraminíferos y una alta relación ostrácodos/foraminíferos, indica ambiente marino marginal, escasa profundidad y condiciones de salinidad normal. La presencia de un nivel próximo a la base de la secuencia con abundantes foraminíferos adheridos, indicaría un aumento en la energía del medio. Asimismo la elevada diversidad de Platycopida sugiere aguas templado-cálidas a subtropicales.The nanoflora and microfauna from the Agrio Formation are analyzed in three different areas of the Neuquén Basin to establish its age and paleonvironmental variations. In the northern area of the basin, the oldest Agrio Fomation sedimentites are recognized and assigned to the Lower Valanginian through ammonites. A monospecific Epistomina loncochensis Ballent microfauna is recovered from these levels, which indicates disoxic environments. Up to the top of the section, siltstones contain a diverse foraminifera microfauna of normal shelves, which are replaced by an impoverished fauna related to shallowing processes. The age defined by calcareous nannofossils is Late Valanginian-Late Hauterivian. In the central and southern position of the Neuquén Basin, the nannofossil assemblages indicate the Upper Valanginian-Upper Hauterivian for the Agrio Formation. The benthic microfauna suggests frequent eustatic variations ranging from shelves to shallow marine environments. In the austral sector of the basin, a poorly diversified foraminiferal assemblage is recorded and a high ostracods/foraminifera ratio indicates a restricted marine environment, and normal salinity. The presence of a level with abundant attached foraminifera indicates high energy episodes. The high diversified Platycopida ostracods suggest warm-temperate to subtropical waters.Facultad de Ciencias Naturales y Muse

Micropaleontology of the Agrio Formation (Lower Cretaceous) in different areas of the Neuquén Basin

Se analizan conjuntamente la nanoflora y microfauna de foraminíferos bentónicos y ostrácodos de la Formación Agrio, en tres sectores de la cuenca Neuquina, a fin de establecer las edades involucradas y considerar las variaciones paleoambientales. En el sector norte de la cuenca se reconocen las sedimentitas más antiguas de la Formación Agrio, asignadas con amonites al Valanginiano inferior y portadoras de una microfauna monoespecífica de Epistomina loncochensis Ballent que indica ambientes disóxicos. Suprayacen limolitas con una microfauna variada de foramíniferos de plataforma marina normal, las que son reemplazadas por microfaunas empobrecidas vinculadas a somerización. La edad de la secuencia definida con nanofósiles es valanginiana tardía - hauteriviana tardía. Para posiciones medias y sur de la cuenca, la edad que indica la nanoflora de la Formación Agrio nuevamente queda comprendida entre el Valanginiano superior y el Hauteriviano superior. La microfauna hallada sugiere frecuentes oscilaciones eustáticas entre ambientes de plataforma y costaneros. En el sector austral de la cuenca, una asociación poco diversa de foraminíferos y una alta relación ostrácodos/foraminíferos, indica ambiente marino marginal, escasa profundidad y condiciones de salinidad normal. La presencia de un nivel próximo a la base de la secuencia con abundantes foraminíferos adheridos, indicaría un aumento en la energía del medio. Asimismo la elevada diversidad de Platycopida sugiere aguas templado-cálidas a subtropicales.The nanoflora and microfauna from the Agrio Formation are analyzed in three different areas of the Neuquén Basin to establish its age and paleonvironmental variations. In the northern area of the basin, the oldest Agrio Fomation sedimentites are recognized and assigned to the Lower Valanginian through ammonites. A monospecific Epistomina loncochensis Ballent microfauna is recovered from these levels, which indicates disoxic environments. Up to the top of the section, siltstones contain a diverse foraminifera microfauna of normal shelves, which are replaced by an impoverished fauna related to shallowing processes. The age defined by calcareous nannofossils is Late Valanginian-Late Hauterivian. In the central and southern position of the Neuquén Basin, the nannofossil assemblages indicate the Upper Valanginian-Upper Hauterivian for the Agrio Formation. The benthic microfauna suggests frequent eustatic variations ranging from shelves to shallow marine environments. In the austral sector of the basin, a poorly diversified foraminiferal assemblage is recorded and a high ostracods/foraminifera ratio indicates a restricted marine environment, and normal salinity. The presence of a level with abundant attached foraminifera indicates high energy episodes. The high diversified Platycopida ostracods suggest warm-temperate to subtropical waters.Fil: Concheyro, Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Lescano, Marina Aurora. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Carames, Andrea Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos "Don Pablo Groeber". Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Estudios Andinos "Don Pablo Groeber"; ArgentinaFil: Ballent, Sara Cristina. Universidad Nacional de La Plata. Facultad de Ciencias Naturales y Museo. Departamento de Paleontología Invertebrados; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentin