Biometric conversion factors as a unifying platform for comparative assessment of invasive freshwater bivalves

Invasive bivalves continue to spread and negatively impact freshwater ecosystems worldwide. As different metrics for body size and biomass are frequently used within the literature to standardise bivalve-related ecological impacts (e.g. respiration and filtration rates), the lack of broadly applicable conversion equations currently hinders reliable comparison across bivalve populations. To facilitate improved comparative assessment among studies originating from disparate geographical locations, we report body size and biomass conversion equations for six invasive freshwater bivalves (or species complex members) worldwide: Corbicula fluminea, C. largillierti, Dreissena bugensis, D. polymorpha, Limnoperna fortunei and Sinanodonta woodiana, and tested the reliability (i.e. precision and accuracy) of these equations. Body size (length, width and height) and biomass metrics of living-weight (LW), wet-weight (WW), dry-weight (DW), dry shell-weight (SW), shell free dry-weight (SFDW) and ash-free dry-weight (AFDW) were collected from a total of 44 bivalve populations located in Asia, the Americas and Europe. Relationships between body size and individual biomass metrics, as well as proportional weight-to-weight conversion factors, were determined. For most species, although inherent variation existed between sampled populations, body size directional measurements were found to be good predictors of all biomass metrics (e.g. length to LW, WW, SW or DW: R2 = 0.82–0.96), with moderate to high accuracy for mean absolute error (MAE): ±9.14%–24.19%. Similarly, narrow 95% confidence limits and low MAE were observed for most proportional biomass relationships, indicating high reliability for the calculated conversion factors (e.g. LW to AFDW; CI range: 0.7–2.0, MAE: ±0.7%–2.0%). Synthesis and applications. Our derived biomass prediction equations can be used to rapidly estimate the biologically active biomass of the assessed species, based on simpler biomass or body size measurements for a wide range of situations globally. This allows for the calculation of approximate average indicators that, when combined with density data, can be used to estimate biomass per geographical unit-area and contribute to quantification of population-level effects. These general equations will support meta-analyses, and allow for comparative assessment of historic and contemporary data. Overall, these equations will enable conservation managers to better understand and predict ecological impacts of these bivalves. © 2021 The Authors. Journal of Applied Ecology published by John Wiley & Sons Ltd on behalf of British Ecological Societ

The true identity of the supposed giant fossil spider Megarachne

Megarachne servinei from the Permo-Carboniferous Bajo de Véliz Formation of San Luis Province, Argentina (32° 17′ S, 65° 25′ E), was described as a giant mygalomorph spider (‘tarantula’) and, with its body length of 339 mm, the largest known spider ever to have lived on Earth. Its identification as a spider was based on interpretations of the shape of the carapace, the position of the eye tubercle, the anterior protrusion of the carapace as a pair of chelicerae, and the posterior circular structure as the abdomen. X-radiography revealed possible morphology hidden in the matrix: cheliceral fangs, sternum, labium and coxae, and so a reconstruction of Megarachne as a giant spider was presented. Difficulties with the interpretation (unusual cuticular ornament, suture dividing the carapace and spade-like anterior border of the chelicera), together with non-preservation of synapomorphies of Araneae, provoked debate about its interpretation as a spider. Now, the holotype and a new specimen have become available for study. Megarachne is shown to be a bizarre eurypterid (‘sea-scorpion’), similar to rare forms known from Carboniferous rocks of Scotland and South Africa, and is the most complete eurypterid so far recorded from Carboniferous strata of South America

Una nueva megaflora (maderas y hojas fósiles) del Mioceno del suroeste de la Patagonia

A new megaflora composed of fossil woods and leaves is described. The bearing sediments overlie the Santa Cruz Formation (early Miocene), making it one of the youngest fossil megafloras described from southern Patagonia. The fossil woods is carbonized and found as clasts within a conglomerate. It includes a few specimens representing Araucariaceae (Agathoxylon sp.), Podocarpaceae (Phyllocladoxylon sp.), Cupressaceae (Cupressinoxylon sp.) and two indeterminable angiosperms with anatomical features consistent with Nothofagaceae. Most leaves are assigned to Nothofagaceae while a few specimens are related to Lauraceae, Typhaceae, Leguminosae, and a conifer. The recovered assemblage suggests a temperate climate similar to that of northern Patagonia today, inhabited by extant relatives of the fossils described herein.Una nueva megaflora compuesta por maderas y hojas fósiles es presentada. Los sedimentos portadores sobreyacen a la Formación Santa Cruz (Mioceno inferior), por lo tanto es una de las megafloras más jóvenes del sur patagónico descripta. Las maderas fósiles están carbonizadas y se encuentran como clastos de un conglomerado. Están representadas por unos pocos especímenes de Araucariaceae (Agathoxylon sp.), Podocarpaceae (Phyllocladoxylon sp.), Cupressaceae (Cupressinoxylon sp.) y dos angiospermas no determinadas que poseen una anatomía consistente con la de las Nothofagaceae. Las hojas son en su mayoría asignadas a las Nothofagaceae, acompañadas por Lauraceae, Typhaceae, Leguminosae y una conifera. El conjunto de fósiles sugiere un clima templado similar al actual de la Patagonia norte, donde viven parientes vivos de los fósiles descriptos.Fil: Pujana, Roberto Roman. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Panti, Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; ArgentinaFil: Cuitiño, José Ignacio. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: García Massini, Juan Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Regional de Investigaciones Cientificas y Transferencia Tecnológica de Anillaco; ArgentinaFil: Mirabelli, Sebastian Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales; Argentin

Angiosperm association from the Río Turbio Formation (Eocene–?Oligocene) Santa Cruz, Argentina: revision of Hünicken’s (1955) fossil leaves collection

The Río Turbio Formation (Eocene–?Oligocene) is of particular paleobotanical interest owing to its combination of high fossil plant diversity associated with the coexistence of warm-temperate and cool-temperate components. As the first suite of fossils related to a documented stratigraphic section, Hünicken’s fossil plant collection is one of the most important from the Paleogene of South America. A total of 34 angiosperm species from the collection were reviewed and taxonomically updated, with Nothofagus as the dominant genus. The taxa identified indicate a warm and humid climate with the development of some elements of a cool-temperate climate marked by a transitional climate change to cooler conditions. The comparison of angiosperms from different paleofloras from the southernmost of South America confirms that the assemblage of Río Turbio Formation was similar to that of the Río Pichileufú area, both from Patagonia, Argentina.Fil: Vento, Barbara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Pramparo, Mercedes Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; Argentin