A new Limnocythere species in the Pampean region (Buenos Aires, Argentina)

Multiproxy paleolimnological research which includes the use of ostracods is in progress in several small lakes (lagunas) in the central plains of Buenos Aires province. Despite the great potential of ostracod-based reconstructions of past hydrological variations, such studies are still scarce. At least two syngamic species of Limnocythere have recently been recovered from Pampean Holocene lacustrine sedimentary cores. Correct identification of these species is of critical importance for the paleoenvironmental interpretation of the ostracod assemblages; however, the taxonomic status of the limocytherids reported from Holocene sediments in the area is far from clear. BERTELS & MARTÍNEZ (1990) mentioned two species of Limnocythere left in open nomenclature from Pampean sediments. CUSMINSKY & WHATLEY (1996) described some new species, including L. rionegroensis, from Patagonia and synonymized L. aff. L. bradburyi figured by BERTELS & MARTÍNEZ (1990) with this new species. FERRERO (1996) reported L. staplini from marginal marine deposits from Buenos Aires. BERTELS & MARTÍNEZ (1997) published a paper including the same two taxa of their previous work, without changes in their identification. CUSMINSKY et al. (2005) assigned L. aff. L. bradburyi of BERTELS & MARTÍNEZ (1990, 1997) to L. rionegroensis. LAPRIDA (2006) reported two extant limnocytherids, Limnocythere sp. and L. aff. L. staplini, and subsequently found them in sedimentary cores from Pampean lagunas (LAPRIDA & VALERO-GARCÉS, 2009). This account attests to the need of taxonomic revision of this genus in the area. In order to clarify its taxonomic status, we present the soft parts description of L. aff. L. staplini Laprida 2006 based on individuals newly collected from Arroyo Chico stream (37° 23´S- 57° 9´W). Lateral view: carapace fairly symmetrical; maximum length (ML) ~ 0.67 mm; maximum height (MH) ~ 0.28 ? 0.30 mm, occurring at ~1/3 ML. Dorsal view: anterior end beak shaped, posterior end rounded with left valve (LV) overlapping right valve (RV). Valve external ornamentation weak, presenting a light reticulate over the whole surface. A sulcus and two or three poorly developed tubercles occur slightly anteriorly of mid-length. Internal view: lophodont hinge of LV consisting of anterior and posterior teeth sockets flanking a central smooth bar; RV with corresponding smooth teeth and central groove. Marginal denticles absent. Marginal zone more developed anteriorly, with few straight, unbranched marginal pore canals. The four anteriormost appendages as for the genus; A2 lacks flagellated claws. Two setae on anterodistal edge of basal segment of the first walking leg (T1), one seta in the corresponding position of second and third walking legs (T2 and T3). Sexual dimorphism pronounced. Female: Dorsal margin rounded. Terminal claw of T1 about ¼ shorter than those of T2 and T3 (with T2 ≈ T3). Male: More elongated than female, carapace reniform, dorsal margin straight. T1 ≈ T2 in length, terminal claw of T3 ≈ 2.5 as long as terminal claws of T2 and T3. This species differs from L. staplini and L. bradburyi in the hinge (smooth vs crenulated elements); from both and L. rionegroensis in the slope of the dorsal margin of the female and shape of the male; and from L. staplini further in the sexual dimorphism in thoracopod size vs thoracopod size equal for both sexes (DELORME, 1970). The above combination of features is unique to this taxon, thus warranting the erection of a new species, Limnocythere sp. nov.Fil: Ramón Mercau, María Josefina. 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: Plastani, María Sofía. 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: Laprida, Cecilia. 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"; Argentina17th International Symposia on OstracodaRomaItaliaItalian Ostracodologists' GroupThe International Research Group on Ostracod

Paleobioindicadores del fin del mundo: ostrácodos y quironómidos del extremo sur de Sudamérica en ambientes lacustres cuaternarios

El objetivo de este trabajo es resumir el estado de las investigaciones paleolimnológicas basadas en bioindicadores pertenecientes al Phylum Arthropoda, en particular ostrácodos (Crustacea) y quironómidos (Diptera), en el ámbito de la República Argentina. Si bien la mayor parte de las investigaciones se han efectuado en el ámbito de la Patagonia, donde han permitido la reconstrucción paleolimnológica de registros desde el último Máximo Glacial y el Holoceno, estos estudios se fueron extendiendo progresivamente hacia las regiones pampeanas, Cuyo y el Noroeste, abarcando distintas ventanas temporales del Pleistoceno Superior y el Holoceno. Son cada vez más numerosas las investigaciones que integran datos actuales y fósiles de ostrácodos y quironómidos, lo que ha permitido, desarrollar funciones de transferencia dando lugar a reconstrucciones cuantitativas robustas y mejorar las interpretaciones cualitativas basadas en la presencia de especies indicadoras. Ambos tipos de reconstrucciones son cada vez más frecuentemente combinadas con otros proxies biológicos, químicos o físicos, brindando un marco multiproxy que permite reconstrucciones integrales de los ecosistemas lacustres cuaternarios. Los estudios de ostrácodos y quironómidos de registros lacustres han permitido no sólo reconocer las tendencias ambientales y climáticas de los últimos miles de años, sino también reconocer eventos climáticos de media y alta frecuencia de interés global, tales como el Younger Dryas, el Antarctic Cold Reversal, el Evento frio 4.2k, la Pequeña Edad de Hielo, y también los cambios climáticos e impactos antrópicos del siglo 20.Fil: Laprida, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Massaferro, Julieta. Administración de Parques Nacionales. Parque Nacional "nahuel Huapi"; ArgentinaFil: Ramón Mercau, María Josefina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Estudios Andinos; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Cusminsky, Gabriela Catalina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Patagonia Norte. Instituto de Investigación En Biodiversidad y Medioambiente; Argentin

Paleobioindicadores del fin del mundo: Ostrácodos y quironómidos del extremo sur de Sudamérica en ambientes lacustres Cuaternarios.

El objetivo de este trabajo es resumir el estado de las investigaciones paleo- limnológicas basadas en bioindicadores pertenecientes al Phylum Arthropoda, en parti- cular ostrácodos (Crustacea) y quironómidos (Diptera), en el ámbito de la República Argentina. Si bien la mayor parte de las investigaciones se han efectuado en el ámbito de la Patagonia, donde han permitido la reconstrucción paleolimnológica de registros desde el último Máximo Glacial y el Holoceno, estos estudios se fueron extendiendo progresivamente hacia las regiones pampeanas, Cuyo y el Noroeste, abarcando distintas ventanas temporales del Pleistoceno Tardío y el Holoceno. Son cada vez más numerosas las investigaciones que integran datos actuales y fósiles de ostrácodos y quironómidos, lo que ha permitido desarrollar funciones de transferencia dando lugar a reconstrucciones cuantitativas robustas y mejorar las interpretaciones cualitativas basadas en la presen- cia de especies indicadoras. Ambos tipos de reconstrucciones son cada vez más frecuen- temente combinadas con otros proxies biológicos, químicos o físicos, brindando un marco multiproxy que permite reconstrucciones integrales de los ecosistemas lacustres cuaternarios. Los estudios de ostrácodos y quironómidos de registros lacustres han permi- tido no sólo reconocer las tendencias ambientales y climáticas de los últimos miles de años, sino también reconocer eventos climáticos de media y alta frecuencia de interés global, tales como el Younger Dryas, el Antarctic Cold Reversal, el Evento Frío 4,2ka, y la Pequeña Edad de Hielo, así también como los cambios climáticos e impactos antrópicos del siglo 20

Modern foraminifera from coastal settings in northern Argentina: implications for the paleoenvironmental interpretation of Mid Holocene littoral deposits

En las costas de la provincia de Buenos Aires, los procesos sedimentarios fueron especialmente activos durante el Cuaternario, debido a las fluctuaciones eustáticas en el nivel del mar. Como resultado, durante las transgresiones del Cuaternario tardío se depositaron  en la planicie costera  sedimentos marinos y marino-marginales. Con el objetivo de interpretar estas secuencias litorales holocenas, se analizó la distribución, diversidad, composición específi ca  y características tafonómicas de las asociaciones totales de foraminíferos bentónicos en ambientes litorales actuales, desde el tope de la duna hasta la anteplaya, en dos transectas cercanas pero geomorfológicamente diferentes, ubicadas en las costas atlánticas del norte de la Provincia de Buenos Aires (Argentina, Sudamérica). Las asociaciones totales de ambientes submareales y supramareales son diferenciables en términos de composición específi ca, diversidad y características tafonómicas. En los ambientes de anteplaya superior, cara de playa, playa distal y duna, las asociaciones están dominadas por tres especies: Buccella peruviana, Ammonia beccarii y Elphidium discoidale (grupo BAE). Esta dominancia es el resultado de procesos tafonómicos que favorecen la preservación selectiva de dichas especies. Las características tafonómicas de las asociaciones modernas permiten una mejor discriminación de los subambientes que la composición taxonómica. Si bien las asociaciones holocenas no poseen homólogos estrictos entre las asociaciones totales de ambientes actuales, la composición taxonómica y los rasgos tafonómicos de las asociaciones permiten inferir que la sucesión holocena se depositó entre la parte superior de la anteplaya y la playa distal.In Buenos Aires coasts, sedimentary processes were particularly active during the Quaternary owing to eustatic fluctuations in sea level. As a result, during the late Quaternary transgressions, marine and marginal marine sediments were deposited in the coastal plain. In order to interpret these Holocene littoral sequences, we analyzed the distribution, diversity, species composition and taphonomic features of total benthic foraminifera assemblages from modern littoral settings, from the top of the dune to the lower shoreface, in two close but geomorphologically different transects located in the Atlantic coast of Northern Buenos Aires Province (Argentina, South America). Total benthic foraminiferal assemblages from subtidal and supratidal environments are distinguishable in terms of composition, diversity and taphonomic features. In upper shoreface, foreshore, backshore and foredune environments, assemblages are clearly dominated by three species: Buccella peruviana, Ammonia beccarii and Elphidium discoidale (the BAE group). This feature is the result of taphonomic processes that favor the selective preservation of such species. The study of taphonomic modifications of shells in modern assemblages allows a better discrimination between subenvironments than the analysis of taxonomic composition. Although Holocene assemblages have no strict counterparts between total modern assemblages, taxonomic composition and taphonomic modification of shells allow us to infer that the Holocene sequence was deposited between the upper shoreface and the backshore.Fil: Laprida, Cecilia. 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: Chandler, Damián Diego Enrique. Universidad de Buenos Aires; ArgentinaFil: Ramón Mercau, María Josefina. 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: López, Rubén Álvaro. Universidad de Buenos Aires; ArgentinaFil: Marcomini, Silvia Cristina. Universidad de Buenos Aires; Argentin

Environmental constraints on benthic foraminifera communities during Middle Pleistocene from the Southwest South Atlantic Ocean

El océano Atlántico Sur es clave en la distribución de masas de agua profunda hacia otros océanos. Dado el papel que juega la circulación termohalina en el clima, el reconocimiento de variaciones en su distribución durante los ciclos glaciales/interglaciales reviste gran interés. Los foraminíferos bentónicos son utilizados como herramientas de reconstrucción paleoceanográ- fica, y la existencia de especies asociadas a masas de agua fue utilizada para definir cambios en la circulación oceánica profunda. Sin embargo, la relación entre foraminíferos bentónicos y masas de agua es controversial. Con el objetivo de determinar si las asociaciones de foraminíferos bentónicos reflejan la distribución de las masas de agua profunda durante un evento glacial del Pleistoceno Medio, se analizó un testigo ubicado en el límite entre dos masas de agua profunda: la North Atlantic Deep Water y la Circumpolar Deep Water. En las asociaciones se hallaron especies consideradas indicadoras de ambas masas de agua, aunque algunas especies asociadas a la Circumpolar Deep Water presentan abundancias relativas mayores, siendo Uvigerina peregrina dominante en ciertos niveles. Sin embargo, la escasa abundancia de Globocassidulina subglobosa, asociada a la Circumpolar Deep Water, y la constancia en el porcentaje de especies consideradas indicadoras de la North Atlantic Deep Water impiden atribuir la dominancia de Uvigerina peregrina a una mayor influencia de la Circumpolar Deep Water. El hecho de que esta especie está asociada a flujos elevados de materia orgánica y que su mayor dominancia coincida con aumentos en la abundancia de Globigerina bulloides indica que la productividad superficial fue el factor determinante en la estructuración de las asociaciones de foraminíferos bentónicos en el talud norbonaerense durante el Pleistoceno Medio.The Southern South Atlantic is crucial in the distribution of deep water masses towards other ocean basins. Given the role of the thermohaline circulation in the climatic system, insights into its variations during glacial/interglacial cycles is of great interest. Benthic foraminifera are used in paleoceanographic reconstructions, tracking changes in deep oceanic circulation by means of the distribution of indicator species associated with certain water masses. However, the relationship between benthic foraminifera and water masses is controversial. A sediment core drilled at the North Atlantic Deep Water-Circumpolar Deep Water limit was surveyed for benthic foraminifera in order to determine whether assemblages reflect patterns of deep watermasses distribution during a Middle Pleistocene glaciation event. The assemblages recovered comprised species indicative of both water types, with Circumpolar Deep Water-indicator species being slightly more abundant due to Uvigerina peregrina dominance. In spite of this, the low abundance of other Circumpolar Deep Water-indicator species such as Globocassidulina subglobosa coupled with the evenness in the relative abundance of North Atlantic Deep Water indicator-species preclude the interpretation of Uvigerina peregrina’s dominance in terms of a greater influence of Circumpolar Deep Water at the expense of North Atlantic Deep Water. The latter species, also an indicator of high organic matter fluxes, increases its relative abundance jointly with those of Globigerina bulloides, which suggests that surface productivity influenced deep benthic foraminifera assemblages in the Buenos Aires talus during Middle Pleistocene glaciations.Fil: Laprida, Cecilia. 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 ; ArgentinaFil: García Chapori, Natalia Luz. 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 ; ArgentinaFil: Ramón Mercau, María Josefina. 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 ; ArgentinaFil: Watanabe, Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Totah, Violeta Ines. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Marcolini, Susana. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; ArgentinaFil: Violante, Roberto Antonio. Ministerio de Defensa. Armada Argentina. Servicio de Hidrografía Naval; Argentin

The role of Southern Hemispheric Westerlies for Holocene hydroclimatic changes in the steppe of Tierra del Fuego (Argentina)

The steppe of northern Tierra del Fuego is an important region for studying climate variability in the Southern Hemisphere, due to its position at the southern margin of the Southern Hemisphere Westerly Wind belt. Here we present a multiproxy analysis of a sedimentary sequence from Laguna Carmen (53°S, 68°W) which provides evidence of the progressive aridity and strengthening of the low-level Westerlies during the Late Holocene. We identified three prominent phases in the climatic record from Laguna Carmen: a cold and wet period between ~4000 cal. BP and ~2200 cal. BP, evidenced by a relative high lake level, periodic runoff into the lake, and oligohaline (mean: 2554 μS/cm) salinities; a step-change towards warmer and drier conditions after ~2200 cal. BP, reflected by limited runoff and oligo-mesohaline salinities (mean: 4799 μS/cm); and finally, the establishment of modern semi-arid conditions some time after ~1000 cal. BP, when the lake became a shallow lake that sometimes dried out during the summer. Our results coincide with paleoclimatic numerical models that suggest a progressive aridification of the southern Patagonian steppe since 6000 cal. BP due to stronger Westerlies and higher temperatures associated with changes in solar irradiance.Fil: Laprida, Cecilia. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Orgeira, María Julia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Fernández, Marilén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Tófalo, Rita. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; ArgentinaFil: Ramón Mercau, María Josefina. Universidad de Buenos Aires; Argentina. 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: Silvestri, Gabriel Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: Berman, Ana Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones del Mar y la Atmósfera. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones del Mar y la Atmósfera; ArgentinaFil: García Chapori, Natalia Luz. 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: Plastani, María Sofía. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Alonso, Susana. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Geociencias Básicas, Aplicadas y Ambientales de Buenos Aires; Argentin

Extant Ostracod biodiversity and its application in the development of transfer functions for Holocene paleoenvironmental reconstructions in Santa Cruz province (50-52° S)

El extremo austral de la región Patagónica es un área de gran interés para la reconstrucción paleoambiental del Holoceno por su situación geográfica y climática única dentro del Hemisferio Sur. El objetivo de la presente investigación fue estimar variaciones pasadas en parámetros ambientales climáticamente controlados durante el Holoceno Medio y Tardío mediante estudios paleolimnológicos basados en un bioproxy, los ostrácodos (Crustacea: Ostracoda). Se analizó la hidroquímica de más de 30 cuerpos de agua lénticos actuales del sur de Santa Cruz, con el objetivo de caracterizar el gradiente ambiental subyacente. A su vez, se evaluó la distribución de los ostrácodos patagónicos en función de la concentración y composición de solutos de sus aguas huésped. Los datos generados fueron utilizados para elaborar una función de transferencia para la reconstrucción cuantitativa de variaciones pasadas en la salinidad, la cual fue aplicada a testigos sedimentarios lacustres cuyo registro abarca los últimos miles de años. Asimismo, se realizaron inferencias semi-cuantitativas sobre la composición de solutos (tipo de agua) en dichos ambientes. Esta información, junto con datos obtenidos a partir de otros proxies - biológicos, sedimentológicos y/o magnéticos – fue utilizada para reconstruir variaciones pasadas en el balance hídrico de los cuerpos de agua estudiados, las cuales a su vez permitieron evaluar cambios en los regímenes de precipitaciones y patrones de circulación atmosférica sobre la Patagonia Astral durante la segunda mitad del Holoceno.The southermost part of the Patagonian region constitutes a key area for the paleoenvironmental reconstruction of the Holocene, due to its unique geographical setting and climatic characteristics within the Southern Hemisphere. The present investigation aimed to estimate past variations in climatically-driven environmental parameters during the Middle and Late Holocene by means of a paleolimnological approach, using ostracods (Crustacea: Ostracoda) as bioproxies. The hidrochemistry of over 30 lentic waterbodies located in southern Santa Cruz province was analyzed in order to characterize the underlying environmental gradient. In turn, Patagonian ostracods distribution was evaluated with respect to the solute concentration and composition of their host waters. This data was used to develop a transfer function for cuantitative reconstruction of past variations in salinity, which was applied to the ostracod record of several lacustrine sediment records spanning the last few milennia. Additionally, semi-quantitative inferences on past solute composition (water type) variations were drawn. This information, together with data inferred from other proxies – biological, sedimentological and/or magnetic – allowed the reconstruction of past variations in the hydrological balance of the waterbodies under study, which in turn provided insight into precipitation regimes and atmospheric circulation patterns shifts over Southern Patagonia during the second half of the Holocene.Fil:Ramón Mercau, María Josefina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

A review of the genus Limnocythere (Podocopida: Limnocytheridae) in the Pampean region (Argentina), with the description of a new species, Limnocythere cusminskyae sp. nov.

Occurrences of Quaternary and extant limnocytherids in the Pampean region of Argentina are reviewed, particularly in relation with their use as paleohydrological indicators in environmental reconstruction research. In spite of its spread occurrence, the systematic of the genus in the area is still little known, which results in most records being left in open nomenclature and paleoenvironmental inferences being made on the basis of general considerations of the genus. We describe a new species, Limnocythere cusminskyae sp. nov., which we consider to be the taxon featured in several of these works, and discuss its morphological and ecological differences with coexisting Limnocythere species, particularly the proposed indicator species L. rionegroensis Cusminsky & Whatley.Fil: Ramón Mercau, María Josefina. 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 ; ArgentinaFil: Plastani, María Sofía. 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 ; ArgentinaFil: Laprida, Cecilia. 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 ; Argentin

An ostracod-based calibration function for electrical conductivity reconstruction in lacustrine environments in Patagonia, Southern South America

In the Patagonian region (∼37–56°S) E of the Andes, the salinity and solute composition of lakes is strongly related to their location along the marked W-E decreasing precipitation gradient that is one of the main climatic features of the area. A calibration function (n = 34) based on 12 ostracod species (Ostracoda, Crustacea) was developed by WA-PLS to quantitatively reconstruct electrical conductivity (EC) values as a salinity proxy. The selected one component model had a r2 = 0.74 and RMSEP and maximum bias equal to 16% and 31% of the sampled range, respectively, comparable to other published ostracod-based calibration functions. This model was applied to the ostracod record of the closed lake Laguna Cháltel (49°58′S, 71°07′W), comprising seven species and dominated by two species of the genus Limnocythere. In order to evaluate the calibration function’s robustness, the obtained EC values were compared with qualitative lake level and salinity variations inferred through a multiproxy hydrological reconstruction of the lake. Both reconstructions show good overall agreement, with reconstructed EC values in the oligo-mesohaline range (average: 11 060 ± 680 μS/cm) between 4570 and 3190 cal BP, corresponding to the ephemeral and shallow lake phases, and a marked decrease in EC concurrent with a lake level rise, reaching an average EC of 1140 ± 90 μS/cm during the deep lake phase (1720 cal BP to present). The variability in the reconstructed EC values for the ephemeral lake phase showed some inconsistency with the expected trend, which was attributed to time-averaging effects; for its part, the pace of the decrease in EC during the medium-depth phase (3190–1720 cal BP) differed from the expected, which could be due to autigenic effects (redissolution of salts) at the onset of this phase. This comparison not only lends support to the adequacy of the calibration function, but also suggests that its application in the context of a multiproxy study can greatly contribute to distinguish between autigenic and climatic-related controls of paleosalinity in closed lakes, allowing performing more accurate paleoenvironmental inferences on the basis of paleohydrological reconstructions.Fil: Ramón Mercau, María Josefina. 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; ArgentinaFil: Laprida, Cecilia. 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; Argentin

Limnocythere cusminskyae Ramón-Mercau, Plastani & Laprida, 2014, sp. nov.

Limnocythere cusminskyae sp. nov. 1990. Limnocythere sp. n. Bertels & Martínez, Fig. 11 1996. Limnocythere staplini. Ferrero, Fig. 4, 1a– 1 d 1997. Limnocythere sp. Bertels & Martínez, Plate V, Fig. 2–3; Plate VI, Fig. 16–17 1998. Limnocythere sp. 1. Bertels-Psotka & Laprida, Fig. 1 1998. Limnocythere staplini. Laprida, Fig. 14 2006. L. aff. L. staplini. Laprida, Fig. 3, J–L. Limnocythere sp. Laprida, Fig. 3, H 2009. L. staplini. Ferrero, Fig. 10, 5– 6 Type material. Holotype: One dissected male from the Arroyo Chico creek; soft parts mounted in a permanent slide with Hydromatrix® mounting medium, valves stored dry in a micropaleontological slide. Collection number: LM– FCEN 3200. Paratypes: One dissected male (LM– FCEN 3201.1) and two dissected females (LM– FCEN 3201.2 and LM– FCEN 3201.3) from the same sample as the holotype; soft parts mounted in permanent slides with Hydromatrix® mounting medium, valves stored dry in a micropaleontological slide. Supplementary material: One male (LM– FCEN 3202.1) and one female (LM– FCEN 3202.2) from depth 0–1.5 cm of La Barrancosa core; one male (LM– FCEN 3202.3) and one female (LM– FCEN 3202.4) from depth 4–5 cm of La Barrancosa core; valves stored dry in a micropaleontological slide. Type Locality: Arroyo Chico creek, Municipalidad de Balcarce, Provincia de Buenos Aires, Argentina (37 ° 23 ' 01'' S – 57 ° 09' 48 '' W). Diagnosis. Small to medium-sized, elongated limnocytherid of approximately 600 µm in length. Males with straight dorsal margin and evident cardinal angles, females with variably arched dorsal margin, clearly discernible anterior cardinal angle and variably expressed posterior cardinal angle; ventral margin markedly concave at midlength; dorsal and ventral margin subparallel. Overall shape of carapace in lateral view reniform (in males) to subreniform (in females). A sulcus and two or three smooth, poorly developed tubercles occur slightly anteriorly of mid-length; valve external ornamentation is weak. The hinge is modified antimerodont, consisting of one anterior small, smooth tooth, a central groove and a small, crenulated posterior tooth in the RV; LV with central bar smooth. A 1 with subapically flagellated setae on the third and fourth segments. Strong sexual dimorphism in thoracopod length: in females, the apical claws of T 2 and T 3 are of similar length, with that of T 1 being approximately ¼ shorter; in males, the apical claws of T 1 and T 2 are subequal while the apical claw of T 3 is approximately 2.5 times longer than either. The hemipenis has a well-developed distal lobe. The upper ramus of the clasping organ is a tentacle-like processus. The x 2 segment of the labyrinth is characteristically elongated and Y-shaped, with the bifurcated extreme adjacent to the vesica ejaculatoria. Derivatio nominis. In honor to Dr. Gabriela Cusminsky, in acknowledgment of her contributions to the knowledge of Quaternary Patagonian ostracods. Description. External view. In lateral view, the carapace is elongated; the anterior and posterior margins are simetrically rounded, with the latter more acuminate. The carapace of the male is reniform, with the posterior end slightly higher than the anterior one; MH situated approximately at anterior 1 / 4 of ML. The dorsal margin is straight, with marked cardinal angles, and subparallel to the ventral margin (Fig. 2 a–b). The female carapace is more compressed, with overall subreniform shape; the dorsal margin is slightly to broadly arched and sloping, with a well-defined anterior cardinal angle and posterior cardinal angle evident to weakly discernible; the ventral margin is broadly sinuous. MH occurs approximately at anterior 1 / 3 of ML (Fig. 2 c–d). In dorsal view, the anterior end is beak-shaped and the posterior end is rounded, with the LV overlapping the RV. External valve ornamentation is weak, presenting a light primary reticulation of muri and secondarily pitted fossae. A sulcus and two or three smooth, poorly developed tubercles occur slightly anteriorly of mid-length. Two rows of minute, similarly sized and shaped denticles occur in the anterior and posterior margins of both valves (only visible through SEM); the first row is located just over the free margin (Fig. 2 h). The valve surface presents scattered sieve-type normal pores. Internal view. The dorsal margin is straight, with the anterior cardinal angle marked. Muscle scars as for the genus with a vertical row of four scars. The hinge is modified antimerodont, consisting of one anterior small, smooth tooth, a central groove and a small, crenulated posterior tooth in the RV (Fig. 2 e–f); LV central bar smooth. The marginal zone is more developed anteriorly, approximately twice as broad anteriorly compared with the posterior margin, with few straight, unbranched marginal pore canals. Soft parts. The four anteriormost appendages are identical for both sexes, except for the morphology of a single seta in A 2 (see below); the three thoracopods, for their part, present strong sexual dimorphism, both in relative size and the chaetotaxy of the basal segment. The antennule (A 1) is 5 -segmented, with subapically flagellated setae on the third and fourth segments (Fig. 3 a). The basal segment bears no setae; the second and third segments bear 1 seta each; the fourth segment presents 6 setae; the fifth segment has 3 setae, one of them proximally fused with an aesthetasc. The antenna (A 2) comprises 5 segments plus the exopod, which is a long, articulated seta (the spinneret seta) (Fig. 3 b). The first four segments present bunches of setulae. The first segment is devoid of setae; the second presents the spinneret seta. The third segment bears 1 seta, smooth in the female and plumose in the male: its lower part is smooth, while the upper part presents numerous long flagella. The fourth segment presents 7 setae; 3 are plumose and 1, located medially, is an aesthetasc. The fifth segment bears 3 apical, unequally long claw-like setae. The mandible (Md) presents a 4 -segmented palp (Fig. 3 c). The first segment bears a respiratory plate with 7 rays and 2 ventro-apically inserted setae; the second segment bears a long plumose seta dorsally, plus 5 smooth + 3 plumose + 2 smooth setae. The third segment presents 2 setae, while the fourth segment bears 4 setae apically. The maxillule (Mx) presents 3 masticatory endites and bears a 2 -segmented palp and a respiratory plate (Fig. 4 d). The second segment of the palp is subrectangular and bears 4 setae. Between Mx and the first walking leg is a so-called sternum, an elongated structure consisting of a central plate and lateral extensions, associated with the masticatory apparatus. The first thoracopod (T 1) is a 4 -segmented limb which bears 6 setae + 1 apical claw in the female (Fig. 3 e), and 5 setae + 1 apical claw in the male (Fig. 3 f); the second seta of the basal segment is plumose in the male. The second thoracopod (T 2) is 4 -segmented; the female presents 4 setae + 1 apical claw (Fig. 3 e), while the male presents 5 setae + 1 apical claw (Fig. 3 f), of which 2 are plumose. The apical claw is about a quarter longer than the apical claw of T 1 in the female and subequal with the apical claw of T 1 in the male. The third thoracopod (T 3) is 4 -segmented as well, bearing 4 setae + 1 apical claw in the female (Fig. 3 e) and 5 setae + 1 apical claw in the male (Fig. 3 f), including 2 plumose setae. While in the female the apical claw of T 3 is approximately as long as the apical claw of T 2, in the male the apical claw of T 3 is strikingly long (≈ 2.5 x length of apical claw of T 2), amounting to about half the total length of the appendage. Genital lobe of the female without special features. The hemipenis (Fig. 3 g) has a well-developed distal lobe. The upper ramus of the clasping organ is a tentacle-like processus. The x 2 segment of the labyrinth is characteristically elongated and Y-shaped, with the bifurcated extreme adjacent to the vesica ejaculatoria. Measurements. Holotype (male; LM– FCEN 3200): ML = 627 µm; MH = 273 µm Paratype (male; LM– FCEN 3201.1): ML = 635 µm; MH = 283 µm Paratype (female; LM– FCEN 3201.2): ML = 565 µm; MH = 295 µm Paratype (female; LM– FCEN 3201.3): ML = 625 µm; MH = 330 µm Distribution. The species has been recorded both living and fossil in Southeastern Pampa, mostly in locations close to the Atlantic coast (Fig. 1). As most of the research involving Quaternary microfossils that has been carried out in the Pampean area is related to past sea level fluctuations reconstruction, and therefore most of those studies included only seaside locations, the fact that Limnocythere cusminskyae sp. nov. has been found almost exclusively in the coastal area is quite probably a sampling bias artifact rather than a reliable indication of the species’ (past) distribution. Laprida (2006) found live specimens of L. cusminskyae sp. nov. mostly in the shallow lakes Chascomús, Salada Grande, Los Horcones, Laguna del Monte and in the Arroyo Grande creek. Bertels & Martínez (1990; 1997) recorded the species in Holocene sediments from an exposed section along the margin of the Napostá Grande stream, at 2.5 km from its outlet to the ocean. The sediments, corresponding to the Bahía Blanca Formation, consist of shallow marine and transitional littoral-estuarine deposits. Ferrero (1996) reported it from a Holocene outcrop on the northern margin of the Quequén Grande river and in Late Pleistocene sediments ascribed to the Canal 5 Formation (Ferrero 2009) drilled near the Mar Chiquita Lagoon. Laprida (1998) found the species in samples taken from an outcrop on the right margin of the Canal Nº 15 channel, corresponding to the early Holocene Destacamento Río Salado Formation, while Bertels-Psotka & Laprida (1998) recovered a single valve from Holocene sediments outcropping near that location (at the junction of Provincial Route Nº 11 and Canal Nº 15 channel), corresponding to the Cerro de la Gloria Member of Las Escobas Formation. Remarks. Several limnocytherids recorded in the Pampean region have been likened to the well-known Neartic species L. staplini and, in one case, L. bradburyi Forester. Cusminsky& Whatley (1996) and Cusminsky et al. (2005) considered the material described as L. aff. L. bradburyi by Bertels & Martínez (1990; 1997) to consist of juveniles of L. rionegroensis. This would be the northernmost record of the latter species, and the only one outside the Patagonian region. L. rionegroensis is known both after bisexual and parthenogenetic populations. The valve outline of the male of L. cusminskyae sp. nov. differs from that of L. rionegroensis in the straight (vs curved) dorsal margin and from that of L. bradburyi in the ventral margin (reniform vs slightly curved). When comparing L. staplini and L. cusminskyae sp. nov., both sexes are very similar in external morphology; perhaps the most important difference between them lies in the hinge, with the anterior tooth of the RV being crenulated in the former and smooth in the latter. Likewise, the valves of the females of L. cusminskyae sp. nov. and L. rionegroensis are very similar in external view. The hinge of L. rionegroensis is described as lophodont with a smooth bar; this would imply that the teeth are smooth, in contrast with the crenulated posterior hinge tooth of L. cusminskyae sp. nov. Lastly, L. cusminskyae sp. nov. differs from L. bradburyi in having a smooth hinge bar (vs crenulated in the latter species). This suggests that careful examination of hingement details might allow distinction between the valves of these similar taxa. With regards to soft parts morphology, presently it is only possible to compare L. cusminskyae sp. nov. with L. staplini, whose appendages were described by Delorme (1971). This author makes no mention whatsoever of sexual dimorphism in thoracopod length; therefore, both species can be easily distinguished on the basis of soft parts analysis. Lastly, it can be mentioned that Kihn & Pall (2013) report a limnocytherid left in open nomenclature, Limnocythere sp., from a small shallow lake in the inland Pampean region; while the line drawings of valves illustrating their work show a certain resemblance to L. cusminskyae sp. nov., their poor quality and lack of description of the material prevent further comparisons.Published as part of Ramón-Mercau, Josefina, Plastani, María Sofía & Laprida, Cecilia, 2014, A review of the genus Limnocythere (Podocopida: Limnocytheridae) in the Pampean region (Argentina), with the description of a new species, Limnocythere cusminskyae sp. nov. in Zootaxa 3821 (1), DOI: 10.11646/zootaxa.3821.1.2, http://zenodo.org/record/22964