A ocorrência de trilobitas Phacopida da Formação Pimenteira em João Costa, Piauí, Brasil

The marine macroinvertebrate fossils from the Devonian of the Parnaíba Basin are among the most diverse of Paleozoic of Brazil. In recent years, most revisions on these fossils involved trilobites from the Pimenteira and Cabeças formations, in the region of Picos and Pimenteiras cities, in the Piauí State. This survey reports the occurrence of Devonian trilobites from the Pimenteira Formation cropping out at João Costa city, in the region of Serra da Capivara National Park, southeastern Piauí State, where two species were recognized: Burmeisteria notica Clarke, 1913 and Metacryphaeus cf. australis Clarke, 1913. The wide occurrence of these genera in the Malvinokaffric Realm shows that transgressive events during part of the Devonian favored the faunal communication between the Andean, Brazilian and South African provinces through the reduction of geographical barriers. Finally, although the still preliminary character of the studies on Pimenteira Formation trilobites, this unit is already providing new paleontological data that contribute to the understanding of these fossil assemblages.Os fósseis de macroinvertebrados marinhos do Devoniano da Bacia do Parnaíba estão entre os mais diversos do Paleozoico do Brasil. Nos últimos anos, a maioria das revisões sobre esses fósseis envolveu trilobitas das formações Pimenteira e Cabeças, na região das cidades de Picos e Pimenteiras, no Estado do Piauí. Esta pesquisa relata a ocorrência de trilobitas devonianos da Formação Pimenteira, aflorante na cidade de João Costa, na região do Parque Nacional da Serra da Capivara, no sudeste do Piauí, onde duas espécies foram reconhecidas: Burmeisteria notica Clarke, 1913 e Metacryphaeus cf. australis Clarke, 1913. A ampla ocorrência destes gêneros no Domínio Malvinocáfrico mostra que eventos transgressivos durante parte do Devoniano favoreceu a comunicação entre as faunas das províncias Andina, Brasileira e Sul-africana, através da redução das barreiras geográficas. Finalmente, apesar do caráter ainda preliminar dos estudos sobre trilobitas da Formação Pimenteira, esta unidade continua fornecendo novos dados paleontológicos que contribuem para o entendimento destas assembleias fósseis

A new genus of Protasteridae (Ophiuridea) from the Lower Devonian Bokkeveld Group of South Africa

Gamiroaster tempestatis, a new genus and species of Palaeozoic ophiuroid, is described from four specimens identified in the Lower DevonianVoorstehoek Formation (Ceres Subgroup, Bokkeveld Group) of SouthAfrica. This ophiuroid belongs the family Protaseridae, a Middle–Late Ordovician taxon that continued into the late Palaeozoic. This new ophiuroid forms part of a much wider fauna of the Malvinokaffric Realm, a biogeographical termused to denote the cool- to cold-water, high-latitude endemic, benthic marine, Devonian faunas of southwestern Gondwana, which also includes the invertebrate fossil assemblages of the Argentine Precordillera and the Fox Bay Formation of the Falkland Islands. The specimens were collected from an obrution deposit excavated on Karbonaatjies farm, ~145 km northeast of Cape Town in theWestern Cape. The excavated rock samples contain >700 articulated specimens of Gamiroaster tempestatis that are closely associated with two types of less common mitrate stylophorans. Silicone casts and high-resolution three-dimensional digital models obtained via micro-CT scanning of these mould fossils provided detailed morphological proxies for this taxonomic description.DST-NRF Centre of Excellence, Palaeosciences (CoE-Pal)JNC201

Alguns restos de peixes fósseis do Devoniano Médio (Eifeliano-Givetiano) da Formação Pimenteira da Bacia do Parnaíba, Nordeste do Brasil

Some Middle Devonian (late Eifelian-early Givetian) fossil fish remains are described from an outcrop of the Pimenteira Formation on the eastern border of the Parnaíba Basin (Picos area, State of Piauí, northeast Brazil). These remains include a fin spine with ribbed ornament, a bicuspid shark tooth similar to those of xenacanths and omalodontids, a badly-preserved Machaeracanthus spine, and small indeterminate scales and fragments of what may be prismatically calcified cartilage. The bicuspid tooth is the first record of its kind from the Devonian of Brazil and the first unequivocal Devonian record from South America. Its principal cusps have widely spaced cristae, like teeth of the Gondwanan Devonian elasmobranch Antarctilamna, but small intermediate cusps are absent (as in Leonodus). The fin spine has comparable ornament to those of Ctenacanthus, Antarctilamna, and Doliodus, but is too poorly preserved for accurate determination. Machaeracanthus is the most widespread Devonian vertebrate in the Malvinokaffric Realm, and its spines are also known from the Old World and Eastern Americas realms, although scales referred to the genus are reported from outside these three regions. The occurrences of Machaeracanthus spines in the Parnaíba and Amazon basins lends support to an earlier proposal based on the distribution of invertebrate fossils that these basins provided maritime connections existed between the Malvinokaffric and the Old World/Eastern Americas realms during the late Eifelian - early Givetian.Restos de peixes fósseis do Devoniano Médio (Neo-eifeliano - Eogivetiano) são descritos da Formação Pimenteira, em sua faixa aflorante na margem oriental da Bacia do Parnaíba (região de Picos, PI, nordeste do Brasil). Os fósseis incluem um espinho de nadadeira ornamentado com costelas, um dente bicúspide de tubarão similar aos dos xenacantos e omalodôntidas, e um espinho mal preservado de Machaeracanthus. Além disso, registram-se pequenas escamas indeterminadas e possíveis fragmentos de cartilagem com calcificação prismática. O dente bicúspide constitui o primeiro achado dessa natureza no Devoniano do Brasil, sendo também o primeiro com registro inequívoco no Devoniano da América do Sul. Suas cúspides principais possuem cristas bem espaçadas entre si (tal como se verifica nos dentes de Antarctilamna, um elasmobrânquio devoniano do Gondwana), porém inexistem pequenas cúspides intermediárias (como em Leonodus). O espinho da nadadeira possui ornamentação comparável à de Ctenacanthus, Antarctilamna e Doliodus, porém a sua má preservacão não permite uma determinação segura. Machaeracanthus é o vertebrado devoniano com a mais ampla distribuição no Reino Malvinocáfrico, e seus espinhos são também conhecidos nos reinos do Velho Mundo e América Oriental, embora escamas referidas ao gênero tenham sido assinaladas fora dessas três regiões. A ocorrência de espinhos de Machaeracanthus nas bacias do Parnaíba e Amazonas reforça uma proposta anterior (baseada na distribuição de certos invertebrados fósseis) de conexões marinhas entre essas duas bacias e os reinos Malvinocáfrico, do Velho Mundo e da América Oriental durante o Neo-eifeliano - Eogivetiano

THE NATURE OF EVOLUTIONARY RADIATIONS WITH A SPECIAL FOCUS ON DEVONIAN CALMONIID TRILOBITES

Trilobites were a diverse group of arthropods that left an extensive fossil record which are today used today to study macroevolutionary patterns and processes. A new species and form of olenelloidea trilobites (Nevadella keelensis n. sp. and Esmeraldina rowei) are described from the lower Cambrian Sekwi Formation, Canada. One particular clade of trilobites, the Devonian calmoniid trilobites of the Malvinokaffric Realm, was hailed as a classic paleontological example of an adaptive radiation. Three aspects of the radiation were examined in detail: diversification rates, biogeography, and morphological change. The rates of speciation calculated from stratigraphy were highest when sea level was lowest suggesting causal effect of abiotic factors in speciation. A phylogenetic biogeographic analysis indicated a geographically complex area, and this geographic complexity created various opportunities for speciation via allopatry through sea level changes. The geometric morphometric analysis of morphological change during the radiation did not show a signal of ecological filling. Ultimately, adaptive radiations--including some classic cases--may be caused primarily by abiotic factors of speciation

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

Discinoids of the Malvinokaffric Realm: Stratigraphic, Paleogeographical Distribution and Systematic Review

The main theme of this paper is the systematic review of discinoids the Lower to Middle Devonian of the Ponta Grossa (latest Pragian to early Emsian) and São Domingos formations (late Emsian to Frasnian), Paraná Basin, Paraná state, Brazil. Five discinoid species were recorded: Orbiculoidea bainii, O. bodenbenderi, O. excentrica, Gigadiscina collis, and Rugadiscina stagona. It was adopted the reallocation in Gigadiscina collis, instead of Orbiculoidea collis, the maintenance of other species, as well as new description data are accepted. Description of Rugadiscina stagona, a new species of discinoid for the Devonian of the Paraná Basin is made

Comments on the ophiuroid family Protasteridae and description of a new genus from the Lower Devonian of the Fox Bay Formation, Falkland Islands

Asterozoan fossils are comparatively rare in Gondwana compared with Laurentia, especially in the Devonian. We examined the only fossil ophiuroid yet known from the Falkland Islands and assess its significance for the evolution of the clade. This ophiuroid, herein distinguished as a new genus and species, Darwinaster coleenbiggsae, belongs to the same suprageneric group as Protaster, which was established on a series of Middle–Upper Ordovician taxa and persisted into the late Palaeozoic remarkably little changed in morphology. This single example is part of a much wider fauna that includes fossils from the Bokkeveld Group, South Africa and the Precordillera of Argentina. Existing palaeobiogeographic reconstructions confirm that these faunas once existed on contiguous terranes and characterized a distinct suite of similar palaeoenvironments within the Malvinokaffric Realm. This study reviews the existing record of Devonian asterozoans and revises Protasteridae

The rise and fall of the Malvinoxhosan (Malvinokaffric) bioregion in South Africa: Evidence for Early-Middle Devonian biocrises at the South Pole

Global reconstructions, inclusive of environments and ecosystems, and biodiversity counts for the Devonian Period are often done so at the expense of high latitude regions given a historical lack of data presented from these areas. This has bearing on the recognition of biocrises (events marked by extinctions and faunal turnovers) at high latitudes as well as their controls and potential correlation with global, regional, and local tempos. The appearance and disappearance of high-latitude endemic Malvinoxhosan (synonymous with the “Malvinokaffric Realm” which it supersedes) marine invertebrate faunas from West Gondwana are often overlooked, in part owing to difficulties in correlating fossil-bearing strata with global frameworks given the absence and rarity of several key index taxa as well as detailed biostratigraphic appraisals in which to draw regional interbasinal correlations and comparisons. The Early to Middle Devonian Series of South Africa (upper Table Mountain, Bokkeveld and lower Witteberg groups) are a classic Malvinoxhosan-bearing section recording the rise of these endemic faunas, as well as their decline and replacement by cosmopolitan faunas. A detailed biostratigraphy of this interval was created following an assessment of fossil material curated at the Council for Geoscience and Iziko South African Museum, Cape Town as well as from literature. These data suggest that the Malvinoxhosan bioregion persisted as a cohesive unit during Rietvlei-Baviaanskloof to Waboomberg deposition (Pragian/Emsian-early Givetian) given that many representative taxa are found in these strata, however showing a trend of decreasing diversity with little origination through time. Above this interval, few representative taxa are known to continue into the upper Bokkeveld and Witteberg groups, disappearing entirely by the deposition of the Blinkberg Formation. The few fossils that are known in these strata and those succeeding it (e.g., the Swartruggens Formation) are entirely cosmopolitan in identity. Using novel multivariate statistical methods (non-metric multidimensional scaling and cluster analysis) in conjunction with network analysis (NA), the data were interrogated to indicate potential groupings of strata according to their fossil content as well as to track faunal changes through time. These analyses suggest the presence of at least seven to eight interval assemblage biozones housed within at least three larger faunal complexes (Eo-Malvinoxhosan, Malvinoxhosan and Post-Malvinoxhosan) based on their constituent faunal makeup. A closer inspection of these faunal complexes and interval assemblage biozones show a stepped decline in biodiversity with little to no origination and recovery through time that may be correlated with local base-level change at varying orders of magnitude. Declines in biodiversity show selectivity for taxa with epifaunal and semi-infaunal habits with respect to infaunal, deep infaunal and nektonic taxa. Environmental conditions associated with the collapse of the Malvinoxhosan bioregion are thought to have been catastrophic as few new (often short-ranging) immigrants are registered in Post-Malvinoxhosan strata. Further to this, those faunas that are prevalent in Post-Malvinoxhosan strata (e.g., Tropidoleptus) those with known high environmental tolerance and were already present in the region prior to the collapse of the Malvinoxhosan bioregion. Lastly, the observed biodiversity changes in South Africa with respect to local base-level show remarkable similarities with several time equivalent locales in South America suggesting that the decline and extinction of the Malvinoxhosan biota was regional and that the biostratigraphy presented herein has regional application. Here, it is thought regional tectonic controls are suggested to have brought on sea-level changes and entrained warmer waters into higher latitudes against the backdrop of overall rising temperatures from the late Givetian onwards. Whilst the decline of the Malvinoxhosan bioregion might associated with global Middle Devonian biocrises (e.g., Kačák; Taghanic) insufficient age constraints for these strata are available at present to make direct comparisons. Furthermore, an adequate driver for global sea-level change during the Devonian Period, needs to be established to tease out global and local signals in constructed local sea-level curves to establish if these changes (and their effects in changes in biodiversity) are truly global in extent