Palinología de los géneros de Cactaceae Maihuenia (Maihuenioideae) y Pereskia (Pereskioideae) de Argentina

Pollen grains of five species from two genera of the subfamilies Maihuenioideae andPereskioideae (Cactaceae) are described with the optical and scanning microscopes.Maihuenia (F.A.C.Weber) K.Schum.: M. patagonica (Phil.) Britton & Rose and M. poeppigii(Otto ex Pfeiff.) F.A.C. Weber ex K. Schum. (Maihuenioideae) and Pereskia Mill.: P. aculeataMill., P. nemorosa Rojas Acosta and P. sacharosa Griseb. (Pereskioideae). The studied pollengrains of genera Maihuenia are prolate or spheroidal, medium or large sized, and Pereskia areall spheroidal and large sized. The apertures show variation in number: three to fourteen,colpate, with different pattern distribution and length of the colpus: Maihuenia has tricolpategrains and Pereskia 6-14 pantocolpate, some of them form syncolpos. The sculpture does notshow marked differences between the species, which is microechinate and nanoechinate withperforations surrounded by a thickening. A key to determine the species of each genus ispresentedFueron estudiados y descriptos con microscopio óptico y microscopio electrónico de barrido,los granos de polen de cinco especies argentinas de dos géneros, Maihuenia (F.C.C.Weber)K. Schum. y Pereskia Mill., pertenecientes a las subfamilias Maihuenioideae y Pereskioideae(Cactaceae). Maihuenia patagonica (Phil.) Britton & Rose, M. poeppigii (Otto ex Pfeiff.) F.A.C.Weber ex K. Schum., (Maihuenioideae), Pereskia aculeata Mill., P. nemorosa Rojas Acosta yP. sacharosa Griseb. (Pereskioideae). Los granos de polen de Maihuenia son prolatos oesferoidales, medianos o grandes y los de Pereskia son todos esferoidales y grandes. Lasaperturas muestran variación en número, tres a catorce, pero todas son colpadas y tienendiferente modelo de ubicación: Maihuenia tiene granos tricolpados y Pereskia 6-14pantocolpados, algunos de éstos forman sincolpos. La escultura no muestra marcadas diferencias entre las especies, ella es microequinada y nanoequinada con perforaciones rodeadas de un engrosamiento. Se presenta una clave para diferenciar las especies de cadagénero

Primeros registros paleontológicos de la localidad de Cerro Pampa (Formación Chiquimil, Mioceno Tardío), Provincia de Catamarca, Argentina

The taphoflora and the mollusk content identified in a lacustrine interval from the El Áspero Member, Chiquimil Formation, at Cerro Pampa (Department of Belén, province of Catamarca, Argentina) is presented herein. In the floral assemblage the Fabaceae is the dominant component, represented by the subfamilies Caesalpinoideae (Chamaecrista flexuosa (L.) Greene, Sena obtusifolia (L.) Irwin y Barneby y Sena bicapsularis (L.) Rouxbourgh), Papilionoideae (Desmodium cf. D. adscendens (Swart) De Candolle y Tipuana tipu (Benth.) Kuntze and Mimosoideae (Mimosa cf. M. flagellaris Bentham y Prosopis sp.). They are accompanied by leaf remains related to Malvaceae (Malvaciphyllum quenquiadensis Anzótegui y Cristalli), Anacardiaceae (Schinopsis lorentzii (Griseb.) Engler, and Cyperaceae (Scirpites sp.1 and others Incertae sedis). The paleofauna is represented by bivalves (Neocorbicula anzoteguiae Morton, Neocorbicula herbsti Morton and Neocorbicula stelzneri (P) Morton) and gastropods (Chilina totoralensis Morton and Biomphalaria sp.). Some paleoenvironmental considerations inferred from the biota of this Mio-Pliocene unit are made. The floristic and faunal fossil assemblage indicates a close relationship between the Chiquimil Formation and the Playa del Zorro Aloformation, exposed at Valle del Cajón, both units being part of the deposits of the Santa María-Hualfín Basin.Key words: Angiosperms, Mollusca, palaeoenvironment, Late Miocene, Catamarca, Argentina.En la localidad de Cerro Pampa (Departamento de Belén) en la provincia de Catamarca, (Argentina) afloran sedimentos de un depósito lacustre correspondientes al Miembro El Áspero, de la Formación Chiquimil. Se presenta parte de la paleoflora hallada compuesta por Fabaceae, Caesalpinoideae (Chamaecrista flexuosa (L.) Greene, Sena obtusifolia (L.) Irwin y Barneby y Sena bicapsularis (L.) Rouxbourgh; Fabaceae, Papilionoideae (Desmodium cf. ascendens (Swart) de Candolle y Tipuana tipu (Benth.) Kuntze; Fabaceae, Mimosoideae (Mimosa cf. flagellaris Bentham y Prosopis sp.; Malvaceae (Malvaciphyllun quenquiadensis Anzótegui y Cristalli; Anacardiaceae (Schinopsis lorentzii (Griseb.) Engler; Cyperaceae (Scirpites sp.1) y otras Cyperaceae Insertae sedis. La paleofauna de moluscos dulceacuícolas (Neocorbicula anzoteguiae Morton, Neocorbicula herbsti Morton y Neocorbicula stelzneri (P) Morton; gastrópodos, (Chilina totoralensis Morton y Biomphalaria sp.) y sus consideraciones paleoambientales inferidas en la localidad, estudiada a partir de los registros paleontológicos y geológicos durante el Mio-Plioceno. Se observa una mayor relación entre la Formación Chiquimil y la Aloformación Playa del Zorro a partir de sus componentes florísticos y faunísticos.Palabras clave: Angiospermas, Mollusca, paleoambiente, Mioceno superior, Catamarca, Argentina

Palynology of the genera of Cactaceae Maihuenia (Maihuenioideae) and Pereskia (Pereskioideae) from Argentina

Pollen grains of five species from two genera of the subfamilies Maihuenioideae andPereskioideae (Cactaceae) are described with the optical and scanning microscopes.Maihuenia (F.A.C.Weber) K.Schum.: M. patagonica (Phil.) Britton &amp; Rose and M. poeppigii(Otto ex Pfeiff.) F.A.C. Weber ex K. Schum. (Maihuenioideae) and Pereskia Mill.: P. aculeataMill., P. nemorosa Rojas Acosta and P. sacharosa Griseb. (Pereskioideae). The studied pollengrains of genera Maihuenia are prolate or spheroidal, medium or large sized, and Pereskia areall spheroidal and large sized. The apertures show variation in number: three to fourteen,colpate, with different pattern distribution and length of the colpus: Maihuenia has tricolpategrains and Pereskia 6-14 pantocolpate, some of them form syncolpos. The sculpture does notshow marked differences between the species, which is microechinate and nanoechinate withperforations surrounded by a thickening. A key to determine the species of each genus ispresented</div

Paleoenvironmental interpretation of the Holocene of Corrientes province, Argentina

The objective of the present paper is to recognize and reconstruct, from the analysis of pollen recovered from sedimentary cores, the predominant plant communities and their variations during the Holocene in Corrientes Argentina, in order to infer changes in climatic conditions, vegetation and paleoenvironmental evolution in the northeast of Argentina. For this study, lakes located in the central region of Corrientes province were selected, comprising part of the western margin of the Iberá Wetland. The palynological analysis of the paleocommunities shows, in a first stage of the mid Holocene, the predominance of marsh grasslands and hygrophilous communities that indicates humid to sub-humid environmental conditions. In a later stage of the mid Holocene, the paleocommunities show a characteristic association of wetlands, which together with the presence of Typha sp., would indicate sub-humid to humid conditions and waterlogged or flooded soils with slow-moving water. For the late Holocene, the paleocommunities show, initially, the presence of a grass-dominated herbaceous steppe, indicating environmental disturbances, which in the fossil record could reflect the combination of intense wind action under a dry climate. In a later stage, the frequency and variety of species characteristic of humid environments increase, dominated by marshy-herbaceous species, in addition to the development of the hygrophilous forest. Consequently, since the mid Holocene, the main climate factors responsible for the observed changes in wetland conditions were the location and intensity of the Atlantic and Pacific anticyclones in addition to changes in sea level. These forces mainly affected the distribution of precipitation, causing significant changes in the vegetation communities.Fil: Fernandez Pacella, Lionel Edgar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; ArgentinaFil: Lara, Maria Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentin