Lamellorthoceratid cephalopods in the cold waters of Southwestern Gondwana: Evidences from the Lower Devonian of Argentina

Based on three specimens assigned to Arthrophyllum sp., the family Lamellorthoceratidae is reported from the Lower Devonian Talacasto Formation in the Precordillera Basin, central western Argentina. These Devonian cephalopods have been known only from low to mid palaeolatitudes and its presence in the cold water settings of southwestern Gondwana is notable. A nektonic mode of life, not strictly demersal but eventually pelagic, with a horizontal orientation of the conch is proposed for adults lamellorthoceratids, whereas a planktonic habit is suggested for juvenile individuals. These features would had allow their arrival to this southern basin, explaining their unusual presence in the Malvinokaffric Realm, and reinforcing the need of re-evaluate the distribution pattern of several groups of cephalopods.Fil: Cichowolski, Marcela. 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: 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; Argentin

The first hirnantian (Uppermost Ordovician) Odontopleurid trilobite from western Gondwana (Argentina)

An odontopleurid trilobite remain is described for the fi rst time from Hirnantian (uppermost Ordovician) rocks of Western Gondwana. Very rare material, represented by a single left librigena, comes from a new fossil locality of the Don Braulio Formation in the Eastern Argentine Precordillera. Based on an updated systematic discussion, the fossil is tentatively referred to Eoleonaspis Sheng. Environmental and paleogeographical settings of this fi nding suggest that the genus would be eurytopic, having a cosmopolitan geographical distribution during the Ordovician-Silurian interval. In addition, the new evidence reinforces that scarce odontopleurids, often represented by Eoleonaspis, characterize a trilobite association together with Mucronaspis Destombes, strengthening it as a worldwide Hirnantian biostratigraphic indicator.É descrito pela primeira vez resto de trilobita odontopleurídeo de rochas do Gondwana Ocidental (Hirnantiano, porção mais superior do Ordoviciano). O material é muito raro, representado por uma única librigena esquerda proveniente de uma nova localidade da Formação Don Braulio na Precordilheira Oriental Argentina. Com base em uma discussão sistemática atualizada, o fóssil é tentativamente referido como Eoleonaspis Sheng. Confi gurações ambientais e paleogeográfi cas deste achado sugerem que o gênero seria euritópico, tendo uma distribuição geográfi ca cosmopolita durante o intervalo Ordoviciano-Siluriano. Além disso, a nova evidência reforça que odontopleurídeos escassos, muitas vezes representados por Eoleonaspis, caracterizam uma associação trilobita juntamente com Mucronaspis Destombes, fortalecendo-o como um indicador bioestratigráfi co mundial do Hirnantiano.Fil: Halpern, Karen. 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; ArgentinaFil: Meroi Arcerito, Facundo René. 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

Glaciomarine sequence stratigraphy in the Mississippian Río Blanco Basin, Argentina, southwestern Gondwana: Basin analysis and palaeoclimatic implications for the Late Paleozoic Ice Age during the Tournaisian

The Late Paleozoic Ice Age (LPIA) has been well recorded in the uppermost Mississippian?Pennsylvanian of Gondwana. Nevertheless, little is known about the temporal and geographic dynamics, particularly during the early Mississippian. We report on exceptional Tournaisian glaciomarine stratigraphic sections from central Argentina (Río Blanco Basin). Encompassing c. 1400 m, these successions contain conspicuous glacigenic strata with age constraints provided bypalaeontological data and U/Pb detrital zircon age spectra. A variety of marine, glaciomarine and fan-deltaic environments indicate relative sea-level variations mainly associated with tectonism and repetitive cycles of glacial activity. Provenance analysis indicates a source from the Sierras Pampeanas basement located to the east. Fifteen sequences were grouped into threedepositional models: (1) Transgressive Systems Tracts (TST) to Highstand Systems Tracts (HST) sequences unaffected by glacial ice; (2) Lowstand Systems Tracts (LST) to TST and then to HST with glacial influence; and (3) non-glacial Falling-Stage Systems Tracts (FSST) to TST and HST. The glacial evidence indicates that the oldest Mississippian glacial stage of the LPIA in southwestern Gondwana is constrained to the middle Tournaisian. In contrast with previous descriptions of Gondwanan coeval glacial records, our sequence analysis confirms complex hierarchical climate variability, rather than a single episode of ice advance and retreat.Fil: Ezpeleta, Miguel. 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: 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: Balseiro, Diego. 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: Davila, Federico Miguel. 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: Dahlquist, Juan Andrés. 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: Vaccari, Norberto Emilio. 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: Sterren, Andrea Fabiana. 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: Prestianni, Cyrille. Royal Belgian Institute of Natural Sciences; BélgicaFil: Cisterna, Gabriela Adriana. 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: Basei, Miguel. Universidade de Sao Paulo; Brasi

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

First report of Devonian bactritids (Cephalopoda) from South America: Paleobiogeographic and biostratigraphic implications

Devonian bactritids are described for the first time from South America. They come from siliciclastic rocks of the Talacasto Formation in the Precordillera Basin, west-central Argentina. The host strata span the Lochkovian - Emsian and contain other non-ammonoid cephalopods as well, thus refuting the alleged virtual absence of cephalopods in circumpolar Devonian basins from southwestern Gondwana (the Malvinokaffric Realm). We report Bactrites gracilis and Devonobactrites? sp., whose wide distribution contrasts with the endemic paleobiogeographic signature of some other taxonomic groups in these basins. Furthermore, new Lochkovian and Pragian records of Bactrites sp. provide new insights into the earliest bactritid records worldwide.Fil: Cichowolski, Marcela. 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: 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; Argentin

The phacopid trilobite Echidnops taphomimus n. sp. from the Lower Devonian of Argentina: Insights into infaunal molting, eye architecture and geographic distribution

Some Silurian-Devonian Argentinian trilobites characterized by infaunal behavior during molting are considered. After a taxonomic reappraisal, a species previously referred to a lineage of the phacopid Paciphacops is proposed as Echidnops taphomimus new species, from the Lower Devonian (probably late Lochkovian) of the Talacasto Formation, Argentine Precordillera. The visual surface of E. taphomimus indicates that a irregular pattern of lens arrangement, typical of early phacopids such as the Ordovician Ormathops, can also be recognized in more derived Devonian relatives, providing new insights on some evolutionary aspects of visual development. Echidnops is recognized in Australia and Argentina, recording an unusual distribution pattern in trilobites from the Lower Devonian of southern South America, otherwise mostly linked to faunas of related Gondwanan, austral circum-polar Devonian basins of the Malvinokaffric Realm. In accordance with proposed increasing predation pressure in the context of the Mid Paleozoic Marine Revolution, evidence indicates that the infaunal molting behavior, as defensive strategy, arose in several trilobite groups during Silurian-Devonian times, rather than in a single endemic lineage of Paciphacops species.Fil: 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; ArgentinaFil: Balseiro, Diego. 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

A revision of the Devonian Malvinokaffric dalmanitid trilobite Dalmanitoides Delo, 1935, on the basis of new data from Argentina

In light of new information on holotypes and additional material from the Lower Devonian type areas from Argentina, the dalmanitid trilobite Dalmanitoides Delo, 1935,is rediagnosed and considered a dalmanitine rather than a synphoriine. Comparison ssuggest that Gamonedaspis Braniša and Vaněk, 1973, is a junior synonym of Dalman-itoides, so that this Early-Middle Devonian genus includes at least five species: fourformally named from South America, D. drevermanni (Delo, 1935), D. boehmi (Knod,1908), D. scutata (Braniša and Vaněk, 1973), and D. accola (Clarke, 1913), together with a species from South Africa here in treated in open nomenclature (D. sp. A).Although the number of Dalmanitoides species suggests a diversification of cosmopol-itan dalmanitines already present in Malvinokaffric basins, a close relationship with the boreal and slightly older Roncellia Lespérance and Bourque, 1971, would suggest migration from the Eastern Americas Paleobiogeographical Realm during the EarlyDevonian as origin of the clade, which is in accordance with paleobiogeographic pat-terns recognized on the basis of evidence from synphoriine distributions.Fil: 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; ArgentinaFil: Vaccari, Norberto Emilio. 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

The new genus Talacastospongia: insights on the first record of a Devonian sponge from South America

The Lower Devonian (Lochkovian) hexactinellid sponge Talacastospongia minima n. gen. n. sp., is reported from the lower beds of the Talacasto Formation in the Argentine Precordillera. It represents the first Devonian sponge from South America and the best record in the paleobiogeographic context of the Malvinokaffric Realm, otherwise virtually devoid of spiculate sponges. This discovery provides some tentative insights on the age and oldest record of the Family Pileolitidae. The paleogeographical context for this new finding shows a high latitude settings with a notable scarcity of hexactinellid sponges recorded to date in Devonian Malvinokaffric basins, and the absence of calcareous spiculate sponges (heteractinids) and hypercalcified sponges (stromatoporoids, sphinctozoans).Fil: Carrera, Marcelo Gabriel. 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; Argentin

The aulacopleurid trilobite Maurotarion Alberti, 1969, in the silurian-devonian of Argentina: Systematic, Phylogenetic and Paleobiogeography significance

Five new species of Maurotarion Alberti, 1969 from the Silurian Lipeo´n Formation and Lower Devonian Talacasto Formation of Argentina are recognized. The comparisons with Bolivian and South African species support a Malvinokaffric clade based on librigenal synapomorphies, here erected as Maurotarion (Malvinotarion) new subgenus. TheMalvinokaffric origin of the family would not be a migration from lower paleolatitudes but an Early Silurian stock of rare cosmopolitan ancestors which underwent a great Devonian radiation. Two lineages can be recognized within Malvinokaffric Maurotarion. The Silurian-Pragian dereimsi lineage is a plesiomorphic one resembling Silurian representatives and involves M. (Malvinotarion) dereimsi, M. (Malvinotarion) talacastoense new species, M. (Malvinotarion?) new species A, M. (Malvinotarion?) new species B, M. (Malvinotarion) sp., and eventually M. (Malvinotarion?) cf. dereimsi. The isaacsoni lineage ranges from the Lower Pragian to Eifelian exhibiting a defined morphologic trend in the librigena. This lineage comprisesM. (Malvinotarion) isaacsoni, M. (Malvinotarion) sp. A from South Africa, M. (Malvinotarion) gaucho new species, M. (Malvinotarion) haudei new species and M. (Malvinotarion) legrandi. A Lochkovian diversification probably took place yet an adequate assessment remains difficult. In contrast, a great evolutionary burst is recognized during the Emsian and is related to Pragian-Emsian global relative sea level curves which are coincident with those proposed from Bolivian and Argentinian basins.Fil: 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; ArgentinaFil: Vaccari, Norberto Emilio. 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

The trilobite Maurotarion megacephalum sp. nov. (Aulacopleuridae) in the Lower Devonian of Argentina: phylogenetic and paleobiogeographic remarks

Maurotarion megacephalum sp. nov., from the Pragian (Lower Devonian) of the Talacasto Formation, Precordillera basin, central-west Argentina, is described and interpreted as the first Malvinokaffric species of the genus outside the endemic subgenus M. (Malvinotarion). Based mainly on librigenal characters, the coeval M. periergum, from the Wenban Limestone, Nevada, U. S. A., is considered the closest allied taxon. Both species are interpreted as those most closely related to M. (Malvinotarion). Evidence suggests faunal exchange between low and high paleolatitudes for the Pragian, a hypothesis previously discarded in light of low sea level conditions interpreted during this time, and linked to a pattern of vicariance and radiation previously recognized from Malvinokaffric Maurotarion species.Maurotarion megacephalum sp. nov., del Pragiano (Devónico Inferior) de la Formación Talacasto, cuenca de Precordillera, centro-oeste de Argentina, es descrito e interpretado como la primera especie malvinocáfrica del género, no perteneciente al subgénero endémico M. (Malvinotarion). Con base en caracteres librigenales, principalmente, M. periergum, de la Caliza Wenban, Nevada, E.U.A., de edad similar, es considerado el taxón más cercanamente relacionado. Ambas especies son interpretadas como las más cercanas al subgénero M. (Malvinotarion). Las evidencias sugieren intercambio faunístico entre paleolatitudes bajas y altas para el Pragiano, una hipótesis previamente descartada en atención a las condiciones de nivel bajo del mar interpretadas para este intervalo, y ligadas a patrones de vicarianza y radiación con base en datos de Maurotarion malvinocáfricos