A summary of the Brazilian Paraná Basin Ordovician

The study of the Ordovician of Paraná Basin culminated on the three-fold lithostratigraphic subdivision of the Rio Ivaí Group as follows: Alto Garças, Iapó and Vila Maria formations. The history of deposition of these rocks is linked to the transition from a marine fluvial environment into the glacial diamictites and shales with dropstones, overlain by post-glacial transgressive shales, siltstones and sandstones. The OrdovicianâSilurian transition is marked by a glacial and an extinction event that impacted the marine diversity of life and the permanence of the first land plants. At least three sections, designated as the sections 1, 2 and 3 below, had their sedimentary facies, taphonomy, organic carbon content and thermal maturation analysed as well as their macro- and microfossil assemblages recognized. All studied sections were productive for macro- and microfossils, although the section 1 has limited occurrence and lower preservation of palynomorphs. The greatest fossil diversity was recovered from the section 2. To date, the diversity recovered from the OrdovicianâSilurian of the Paraná Basin comprises 12 fossil groups, namely ostracods, brachiopods, bivalves, gastropods, cryptospores, fungi, acritarchs, chitinozoans, prasinophyte algae, scole­codonts, a possible graptolite and, more recently, a trilobite of the order Dalmanitidae. 51 species of palynomorphs of terrestrial and marine origin were recognized. This is the highest diversity reported from the glacialâpostglacial transition in the OrdovicianâSilurian boundary interval of Brazil. 18 species of cryptospores, acritarchs and fungi occur in the basal diamictites (the Iapó Formation) as well as the discinoid Kosoidea australis. In the upper part of these diamictites, the palynomorph assemblage comprises 26 taxa, most of which persist also in the postglacial shales. Still, in the shales with dropstones of the Iapó Formation, brachiopods (K. australis, infaunal lingulids, ?Palaeoglossa and rhynchonelliformeans), endemic ostracods such as Satiellina paranaensis and pyritized specimens of a widely common Hirnantian index species Harpabollia harparum occur together with indeterminable ostracod species. At least two different species of bivalve mollusks were also found as well as a gastropod species (Bucanellasp.). Observing the palynomorph assemblage, it was possible to record also chitinozoans restricted to the lowermost portion of the Vila Maria Formation. This part of the formation was observed in the outcrops 2 and 3 and contains postglacial chitinozoan assemblages that are not younger than the earliest Rhuddanian. Some centimeters above this interval but still in the lower part of the Vila Maria Formation, the occurrence of Spinachitina debbajae followed by Spinachitina silurica refer to the Silurian in the Paraná Basin. In the section 1, the recovery of a trilobite thorax configures the oldest record of this group in Brazil and shows that this ancient sea was also thriving with life even after the glaciation-related Hirnantian extinction event

A taxonomic revision of the Early Devonian dalmanitid trilobite Kasachstania Maksimova, 1972 from central Kazakhstan

The dalmanitid trilobite Kasachstania Maksimova, 1972, previously reported from the Lower Devonian of Kazakhstan and North America (USA) and the upper Silurian–Lower Devonian of South America (Bolivia and Argentina), is revised. Kasachstania kasachstanica (Balashova in Maksimova,1968) and K. septicostata (Maksimova, 1968) are regarded as junior synonyms of the type species K. saryarkensis (Maksimova, 1960), all from the Lower Devonian of the type locality in central Kazakhstan (northern Balkhash). On the basis of a new diagnosis, K. ulrichi ulrichi (Delo, 1940) from the Emsian of the United States, K. ulrichi asiatica (Maksimova, 1968), K. pristina (Maksimova, 1968), and K. alperovichi Pour et al., 2019, from the Lower Devonian of Kazakhstan, K. andii (Kozłowski, 1923) from the upper Silurian–Lower Devonian of Bolivia, and K. gerardoi Edgecombe and Ramsköld, 1994, from the upper Silurian–Lower Devonian of Bolivia and Argentina are excluded from Kasachstania. This genus, represented only by K. saryarkensis and K. kiikbaica (Maksimova, 1968), is restricted to the Lower Devonian of central Kazakhstan, corresponding to the Balkhash–Mongolo–Okhotsk province in the paleobiogeographic context of the Old World Realm, instead of being nearly cosmopolitan as previously considered. In addition, we provide some remarks about Saryarkella Maksimova, 1978b, a monospecific dalmanitid genus largely overlooked although valid from the Emsian of the same area in central Kazakhstan.Fil: Randolfe, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; ArgentinaFil: Rustán, Juan José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de La Rioja; ArgentinaFil: Bignon, Arnaud Marcel Jacques. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentin

Cambios en la diversidad de tortugas (Testudinata) en América del Sur desde el triásico tardío hasta el presente

Los avances recientes en el registro fósil, la anatomía y la historia evolutiva de las tortugas sudamericanas permiten un análisis exhaustivo de sus cambios en la diversidad y la identificación de eventos importantes de extinción. Con la ruptura de Pangea en el Jurásico Medio, las tortugas comienzan a diversificarse, dando lugar a los principales clados de tortugas sudamericanas, algunos de los cuales sobreviven hasta el presente. El primer pico de diversidad se observa en el Cretácico Temprano. Se reconoce un primer evento de extinción al final del Cretácico Temprano, que afecta principalmente a los Pelomedusoides en las latitudes bajas y que coincide con la separación final de América del Sur de África. La extinción del límite K–Pg afectó profundamente las tortugas en el continente al reducir su diversidad a la mitad. La reducción de la diversidad continuó después de la extinción K–Pg, aproximadamente hasta el Eoceno medio y el aislamiento final del continente de la Antártida. En este “nuevo” continente, las tortugas sobrevivientes continuaron disminuyendo en su diversidad, hasta que una inyección de biodiversidad desde África ayudó a recuperar los niveles de diversidad. El levantamiento de los Andes en el Oligoceno tardío–Mioceno temprano y los cambios climáticos y de hábitat asociados plantearon nuevos problemas para las tortugas. Nuevas inyecciones de biodiversidad ocurrieron al final del Neógeno con el Gran Intercambio Biótico Americano, cuando nuevos clados llegaron desde el Norte. La biodiversidad moderna de las tortugas sudamericanas tomó su forma final solo durante el último millón de años.Recent advances in the fossil record, anatomy, and evolutionary history of South American turtles allow a thorough analysis of their changes in diversity, and to identify several major extinction events. With the onset of the breakup of Pangea in the Middle Jurassic, turtles begin to diversify, giving rise to the main South American turtle clades some of which survive until present. The first peak of diversity was achieved in the Early Cretaceous. A first extinction event is recognized in the end of the Early Cretaceous, affecting mainly the pelomedusoids in northern latitudes and coinciding with the final separation of South America from Africa. The K–Pg boundary mass extinction affected deeply the thriving turtles in South America by reducing their diversity in half. Reduction of diversity continued on the aftermath of the K–Pg extinction, roughly until the middle Eocene and the final isolation of South America from Antarctica. In this “new” continent, the diversity of the surviving turtles continued to decrease, until an injection of biodiversity from Africa, with the arrival of tortoises, which helped to recover the diversity levels. The Andean uplift in Late Oligocene–Early Miocene and the associated climate and habitat changes posed new problems for the turtles of the continent. New injections of biodiversity took place at the end of the Neogene with the Great American Biotic Interchange, as novel clades reached South America from the North. The modern biodiversity of South American turtles took its final shape only during the last million years.Fil: Vlachos, Evangelos. Museo Paleontológico Egidio Feruglio; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Randolfe, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; ArgentinaFil: Sterli, Juliana. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Museo Paleontológico Egidio Feruglio; ArgentinaFil: Leardi, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentin