The morphology and systematics of the clam shrimp Platyestheria gen. nov. abaetensis (Cardoso) (Crustacea, Spinicaudata) from the Lower Cretaceous of the Sanfranciscana Basin, southeast Brazil

New specimens of the clam shrimp ‘Pseudestheria’ abaetensis Cardoso, 1971 (Spinicaudata) are described. The material was collected from the Quiricó Formation (Lower Cretaceous of the Sanfranciscana Basin), at the same locality as the type series of the species. The carapaces are very large, oval and elongated, with anteriorly located and slightly projected umbo, straight dorsal margin, with flattened growth bands and 15–20 serrated growth lines. Details of the microscopic structure of the carapace were analysed under scanning electron microscope for the first time, disclosing a unique reticular pattern of ornamentation. This species is similar to some Early Cretaceous taxa from South America, Africa and China. Yet, the peculiarities in the shape and ornamentation of the carapace support its reassignment to a new genus (Platyestheria gen. nov.), within the Superfamily Eosestherioidea. In addition, an energy-dispersive X-ray spectroscopy analysis of the multiple stacked growth bands revealed that the valves are enriched in calcium and phosphorus, similar to those of modern spinicaudatans. Minor amounts of silicon, iron and aluminium suggest that the carapaces were preserved partly through the input of ions from the environment during the diagenesis.Fil: Bittencourt Guimaraes, Ana Tereza. Universidade Federal de Minas Gerais; BrasilFil: Rohn, Rosemarie. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Gallego, Oscar Florencio. 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: Monferran, Mateo Daniel. 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: Uhlein, Alexandre. Universidade Federal de Minas Gerais; Brasi

Mesozoic sedimentary cover sequences of the Congo Basin in the Kasai region, Democratic Republic of Congo

The Congo Basin represents one of the largest and least studied continental sedimentary basins in the world. The stratigraphy of cover sequences across the basin is poorly resolved and a somewhat simple stratigraphy has generally been applied with gross subdivision of the Mesozoic-Cenozoic cover sequences into a number weakly correlated units. Although these subdivisions are useful for broad, regional-scale correlations, investigation of drill cores and outcrop in the shallow, southern Kasai part of the basin, from Tshikapa to Kabinda, reveals considerable facies, provenance and thickness variations, suggesting a more complex depositional and stratigraphic history than previously recognized. This study now permits the subdivision of the sedimentary cover in the Kasai portion of the Congo Basin into five distinct depositional sequences consisting of (1) P1: Permo-Carboniferous glacio-lacustrine deposits correlative to the Lukuga Group; (2) J1: Jurassic-age arid to semi-arid laminated shales and siltstones and aeolian sandstones, interpreted as ephemeral lake and sand dune sequences with interspersed loess deposits and rare fluvial channel sequences (considered part of the historic Lualaba-Lubilash Supergroup—the lacustrine facies likely correlates with the Stanleyville Group, DRC and the Continental Intercalar Group, Angola); (3) C1 & C2: Lower Cretaceous locally heavy mineral-rich fluvial sandstone deposits and variably present basal conglomerate (correlated to the Loia Group, DRC and the Calonda Formation, Angola); (4) C3 & C4: Upper Cretaceous conglomerates of alluvial fan origin that grade upward into laminated shales and siltstones or well-sorted and rounded, fined grained sandstones representative of a semi-arid to arid depositional setting dominated by ephemeral lakes and small aeolian dunes, (equated to the Kwango Group, DRC and Angola) and (5) T1: fluvial, aeolian and lacustrine sediments of Paleogene age (correlated with portions of the Kalahari Group). The results convincingly suggest that this part of the Congo Basin is more structurally complex than previously appreciated, with multiple fault-bounded basement highs and depocenters that strongly influenced regional sedimentation patterns. Prolonged and sporadic displacement appears to have taken place along these faults, leading to heavily bisected basin morphology with uneven thickness and depth distributions between sequences. The deposition of Cretaceous sequences was coeval with two episodes of kimberlite emplacement, the first at ~120–130 Ma in northern Angola, and the second at ~70–80 Ma in the DRC, with gravel horizons within the Cretaceous fluvial successions (C1 and C3) known for their alluvial diamond concentration. The models developed provide a regional context for evaluation of alluvial diamond source areas and prospectivity

La fauna de espinicaudados de la formación cerro de las cabras (Cuenca Guyana), provincia de Mendoza (Argentina): descripción de nuevas especies y revisión de registros previos

Se presenta el estudio sistemático de la fauna de Spinicaudata de la Formación Cerro de Las Cabras (Triásico Medio), norte del cerro Bayo, en la clásica localidad de Potrerillos, Precordillera de Mendoza, Cuenca cuyana, Argentina. Se describen dos nuevas especies: Estheriellites zavattieriae sp. nov. y Euestheria menendezi sp. nov., se enmienda la diagnosis del género y de la especie Challaolimnadiopsis mendozaensis Shen and Gallego, y se describe la especie Euestheria martinsnetoi Gallego et al., previamente citada para la Formación Río Mendoza y que ahora se considera perteneciente a los estratos de Cerro de Las Cabras. La sección estudiada consiste de finas areniscas tufáceas y pelitas interpretadas como depósitos de barreales, ríos y/ o arroyos efímeros de la planicie fluvial. Lagos efímeros o ambientes lacustres someros están caracterizados por una sucesión de limolitas interestratificadas con calizas nodulares-moteadas y estromatolíticas con exposición sub-aérea e incipiente desarrollo de suelos en áreas deprimidas y anegadas bajo condiciones de clima estacional semiárido. Los espinicaudados probablemente habitaron los ambientes de las costas de los lagos y los pequeños pantanos de la planicie fluvial. La profusa presencia de depósitos piroclásticos a lo largo de la secuencia indica una apreciable actividad volcánica explosiva, coetánea con la sedimentación. Sobre la base de consideraciones litoestratigráficas, paleontológicas y dataciones realizadas previamente en esta unidad, la edad de los depósitos estudiados fueron limitados al Triásico Medio (equivalente al Anisiano Tardío-Ladiniano Tardío de las secuencias marinas) y por lo tanto, la asociación faunística E. zavattieriae-E. martinsnetoi es considerada como indicadora para tal edad.This is a systematic study of the Spinicaudata fauna of the Cerro de Las Cabras Formation (Middle Triassic), north of Cerro Bayo, in the classical Potrerillos area, Precordillera of Mendoza, Cuyo Basin, Argentina. Two new species are described: Estheriellites zavattieriae sp. nov. and Euestheria menendezi sp. nov.. The diagnosis of the genus and species of Challaolimnadiopsis mendozaensis Shen and Gallego, is emended; and Euestheria martinsnetoi Gallego et al., previously described for the Río Mendoza Formation is now considered as coming from the Cerro de Las Cabras strata. The studied section consists mainly of fine-grained tuffaceous sandstones and interbedded mudstones interpreted as playa lake, ephemeral rivers and/or streams developed in the floodplain. Ephemeral to shallow lacustrine environments are characterized by interbedded siltstones, nodular-mottle and stromatolitic limestones with sub-aerial exposures and incipient soil development in depressed and flood-prone areas under seasonal semi-arid conditions. Spinicaudatans probably inhabited lacustrine shorelines and small ponds in the floodplain where plant remains (arthrophyte) and rare fish scales were also recorded. The profuse presence of pyroclastic deposits along the sequence indicates considerable explosive volcanic activity coeval with sedimentation. Based on previous lithostratigraphical, paleontological and chronological data, the age of the studied deposits was constrained to Middle Triassic (equivalent to Late Anisian—Late Ladinian of marine sequences) and therefore the E. zavattieriae-E. martinsnetoi Faunal Association is considered as a marker for such age range.Fil: Vaz Tassi, Lara. 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: Zavattieri, Ana Maria. 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: Gallego, Oscar Florencio. 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