Distribution of ostracods in west-central Argentina related to host-water chemistry and climate : Implications for paleolimnology

Ecological and biogeographical studies of Neotropical non-marine ostracods are rare, although such information is needed to develop reliable paleoecological and paleoclimatic reconstructions for the region. An extensive, yet little explored South American area of paleoclimatic interest, is the arid-semiarid ecotone (Arid Diagonal) that separates arid Patagonia from subtropical/tropical northern South America, and lies at the intersection of the Pacific and Atlantic atmospheric circulation systems. This study focused on the Laguna Llancanelo basin, Argentina, a Ramsar site located within the Arid Diagonal, and was designed to build a modern dataset using ostracods (diversity, spatial distribution, seasonality, habitat preferences) and water chemistry. Cluster and multivariate analysis of the data indicated that salinity is the most significant variable segregating two ostracod groups. Limnocythere aff. staplini is the only species that develops abundant populations in the saline ephemeral Laguna Llancanelo during almost all seasons, and is accompanied by scarce Cypridopsis vidua in summer. The latter species is abundant in freshwater lotic sites, where Ilyocypris ramirezi, Herpetocypris helenae, and Cyprididae indet. are also found in large numbers. Darwinula stevensoni, Penthesilenula incae, Heterocypris incongruens, Chlamydotheca arcuata, Chlamydotheca sp., Herpetocypris helenae, and Potamocypris smaragdina prefer freshwater lentic conditions (springs), with C. arcuata and Chlamydotheca sp. found only in the Carapacho warm spring, which has a year-round constant temperature of ~20 °C. Seasonal sampling was necessary because some taxa display a highly seasonal distribution. Species that were recorded have either subtropical or Patagonian affinities, although a few taxa are endemic or common to both regions. These data can serve as modern analogues for reconstructing the late Quaternary history of the area, and to investigate the extent and position of the arid/semiarid ecotone (Arid Diagonal) during past glacial/interglacial cycles.Instituto de Limnología "Dr. Raúl A. Ringuelet

New records of non-marine ostracoda (Crustacea, Ostracoda) in Western Patagonia, Chile

Los antecedentes de ostrácodos no-marinos de Chile son escasos y fueron desarrollados por naturalistas europeos que viajaron a América del Sur durante las primeras décadas del siglo pasado. No obstante, a la fecha son obsoletos e incompletos. Los trabajos de Vávra (1898), Daday (1902), Löffl er (1961a, b, 1966) contribuyen con los primeros listados bibliográfi cos y descripciones de ostrácodos en Chile. Martens & Behen (1994) realizaron un listado para Sudámerica que incluye un total de 28 especies para Chile. Todas las especies registradas allí pertenecen al orden Podocopida, las que se encuentran distribuidas entre las familias: Cyprididae, Darwinulidae, Limnocytheridae, Candonidae, Cytherideidae, Illyocyprididae y Notodromatidae. El objetivo de esta comunicación es la expansión del conocimiento de los ostrácodos no-marinos de la Patagonia Chilena y contribuir con nuevos antecedentes sobre su distribuciónFacultad de Ciencias Naturales y Muse

The genus Chlamydotheca Saussure (Crustacea: Ostracoda) in northeastern Argentina

The genus Chlamydotheca Saussure, 1858 is a typical representative of the Neotropical ostracod fauna that occupies lotic and lentic environments including temporary and permanent ponds. Up to the present, four species have been recorded in Argentina: C. iheringi (Sars), C. incisa (Claus) and C. leuckarti (Claus), and C. symmetrica (Vávra). Temporary and permanent ponds of this region were sampled for ostracods, using a fine mesh net. Three species belonging to the genus Chlamydotheca were collected of which C. arcuata (Sars) is recorded for first time for the Chacoan region. Limb morphology was studied under light microscope and line drawings were made using camera lucida. Valves were photographed under scanning electron microscope and redescriptions of C. arcuata and C. iheringi are provided and distributional aspects of the species sampled are discussed

The genus Chlamydotheca Saussure (Crustacea: Ostracoda) in northeastern Argentina

The genus Chlamydotheca Saussure, 1858 is a typical representative of the Neotropical ostracod fauna that occupies lotic and lentic environments including temporary and permanent ponds. Up to the present, four species have been recorded in Argentina: C. iheringi (Sars), C. incisa (Claus) and C. leuckarti (Claus), and C. symmetrica (Vávra). Temporary and permanent ponds of this region were sampled for ostracods, using a fine mesh net. Three species belonging to the genus Chlamydotheca were collected of which C. arcuata (Sars) is recorded for first time for the Chacoan region. Limb morphology was studied under light microscope and line drawings were made using camera lucida. Valves were photographed under scanning electron microscope and redescriptions of C. arcuata and C. iheringi are provided and distributional aspects of the species sampled are discussed

La modificación de normas legales por vía reglamentaria y la aclaración de errores reglamentarios diez años después de su presunta comisión: dos ejemplos de incorrecta técnica legislativa

Los antecedentes de ostrácodos no-marinos de Chile son escasos y fueron desarrollados por naturalistas europeos que viajaron a América del Sur durante las primeras décadas del siglo pasado. No obstante, a la fecha son obsoletos e incompletos. Los trabajos de Vávra (1898), Daday (1902), Löffl er (1961a, b, 1966) contribuyen con los primeros listados bibliográfi cos y descripciones de ostrácodos en Chile. Martens & Behen (1994) realizaron un listado para Sudámerica que incluye un total de 28 especies para Chile. Todas las especies registradas allí pertenecen al orden Podocopida, las que se encuentran distribuidas entre las familias: Cyprididae, Darwinulidae, Limnocytheridae, Candonidae, Cytherideidae, Illyocyprididae y Notodromatidae. El objetivo de esta comunicación es la expansión del conocimiento de los ostrácodos no-marinos de la Patagonia Chilena y contribuir con nuevos antecedentes sobre su distribuciónFacultad de Ciencias Naturales y Muse

New toxodontid (Notoungulata) from the Early Miocene of Mendoza, Argentina

We describe a new toxodontid species, Nesodon taweretus sp. nov., from the Aisol Formation in Mendoza Province, central-west Argentina. Nesodon is a frequently found Toxodontidae, member of the Notoungulata, an extinct endemic group of Cenozoic South American mammals that are ecologically similar to current hoofed ungulates. The holotype of N. taweretus sp. nov. is a skull, and we tentatively assign some mandibular fragments and postcranial bones. N. taweretus sp. nov. differs from the other Nesodon species in several cranial and dental features, and close comparisons were made with the Patagonian Nesodon imbricatus, common in the Santa Cruz Formation (Santacrucian Age, Early Miocene). The material is of a similar size to N. imbricatus, with a body mass estimation of about 550 kg. The phylogenetic analysis groups N. taweretus sp. nov. with other species of Nesodon. The absolute age of the Aisol Formation has been established at ca 19.480 ± 0.025 Ma (Burdigalian; Early Miocene) by means of U–Pb zircon dating. The vertebrate association is encompassed by the Santacrucian Age. Latitudinal separation between Mendoza and Patagonia in the south would have favored taxonomic differences, as reflected in the species of Nesodon. = Wir beschreiben eine neue Art der Toxodontiden, Nesodon taweretus sp. nov., aus der Aisol-Formation in der Provinz Mendoza, im Zentralwesten von Argentinien. Nesodon ist ein häufig vorkommendes Taxon der Toxodontidae, die zu den Notoungulaten, einer ausgestorbenen Gruppe von endemischen Säugetieren des Känozoikums in Südamerika, gehören und den rezenten gehuften Ungulata ökologisch ähnlich waren. Der Holotyp von N. taweretus sp. nov. ist ein Schädel, dem wir vorläufig einige Unterkieferfragmente und postkraniale Knochen zuweisen. N. taweretus sp. nov. unterscheidet sich von den anderen Nesodon-Arten in mehreren Merkmalen des Schädels und der Bezahnung. Enge Vergleiche wurden mit dem aus Patagonien stammenden und in der Santa-Cruz-Formation (Santacruzium, frühes Miozän) verbreiteten Nesodon imbricatus gemacht. Das Material ist von ähnlicher Grösse wie N. imbricatus, Schätzungen der Körpermasse ist etwa 550 kg. Die phylogenetische Analyse gruppiert N. taweretus sp. nov. mit anderen Arten von Nesodon. Das absolute Alter der Aisol-Formation wurde mittels der U–Pb Zirkondatierung auf etwa 19.480 ± 0.025 Ma (Burdigalium, Unteres Miozäns) gesetzt. Die Wirbeltiervergesellschaftung in das Santacruzium eingeschlossen worden. Latitudinale Trennung zwischen Mendoza und Patagonien im Süden hätte taxonomischen Unterschiede begünstigt, wie das anhand der Arten von Nesodon widergegeben ist