Dr. Marcelo G Carrera PHD (paleontologist)Professor of Palebiology, National University of Cordoba, Argentina.Researcher National ResearchCouncil ArgentinaSpecial interest: Fossil Sponges, Bryozoans and reef-related organisms
Specimens of the trepostome bryozoans genus Nicholsonella Ulrich are described and figured. They ... more Specimens of the trepostome bryozoans genus Nicholsonella Ulrich are described and figured. They occur in Arenigian limestones of San Juan Formation. Precordillera basin. Argentina. More than fifteen colonies were collected from a single horizou included in a cyclic succession of intraclastic to. bioclasti c grainsto.ne and skeleral wackestone. The specimens of Nicholsonella encrust skeletal remains, even the interior of some shells, and the surrounding sediment. The encrusting colony as well as the associated coarse-grained sediment suggest high energy conditions. The Arenig paleobiogeographical distribution of Nicholsonella is discussed. The occurrence of this genus shows a world-wide distribution restricted to tropical and subtropical zones.
Although bryozoans have been mentioned in several papers, few systematic descriptions of this gro... more Although bryozoans have been mentioned in several papers, few systematic descriptions of this group are available from the late Paleozoic of western Gondwana, particularly from the Permian sequences. In South America, bryozoan faunas have been reported from the Permian of Venezuela (Laya and Tucker, 2012), Perú, and Bolivia (Sakagami, 1995 and references therein). In Argentina, the late Paleozoic bryozoan faunas have been described mainly from the Carboniferous deposits of the central-western Precordillera Basin (Sabattini, 1986 and references therein). Few Permian records were reported from northwestern Argentina (Arizaro Formation; Aceñolaza et al., 1972) and in the siliciclastic postglacial marine deposits from Patagonia (Sabattini, 2002; Pagani and Taboada, 2010). Permian bryozoan records were mentioned in two sections from northern Chile, with reports of scarce indeterminate forms (Rivano and Sepúlveda, 1985; Díaz Martínez et al., 2000). The aim of this contribution is to provide a new record of a bryozoan species from northernChile, based onmaterial collected from the Cerro El Árbol Formation in the Augusta Victoria area (Fig. 1). The faunal content and the lithological characteristics are analyzed in the context of the paleogeographic position of this area, along the western Gondwana margin.
... grew in a shallow subtidal environment below the fair-weather wave base and which was periodi... more ... grew in a shallow subtidal environment below the fair-weather wave base and which was periodically affected by the storm wave base ... las especies incluyó el conteo numérico de los ejemplares, los valores de biovolumen y la relación altura máxima sobre diámetro máximo (A/ ...
Five genera of anthaspidellid and streptosollenid demosponges are described from the Ordovician L... more Five genera of anthaspidellid and streptosollenid demosponges are described from the Ordovician Lenoir Limestone near Lenoir City, Loudon County, Tennessee, USA including:Rhopalocoelia regularisRaymond and Okulitch,Rugocoelia loudonensisn. sp.,Psarodictyumsp. (Anthaspidellidae),Allosacus pedunculatusn. sp., andZitelella variansRaymond and Okulitch (Streptosolenidae). These findings confirm the major paleobiogeographic picture for Laurentian sponges (i.e., the differential distribution of sponge faunas along both North American margins), because none of these eastern margin species has been reported from western margin faunas. Only one genus typical of the Great Basin fauna,RugocoeliaJohns, 1994, is reported from Tennessee, but as a new species. Possible explanations are discussed for this differential distribution, mainly related to climatic constraints or sedimentary differences, preventing the free distribution of sponge species between Laurentian continental margins.UUID:http://zoobank.org/2b990a4c-7bc8-4eb6-b8a9-fe4ecf7bdbf9
Monticulipora argentina was erected by Kayser to include a conical form composed by smalllongitud... more Monticulipora argentina was erected by Kayser to include a conical form composed by smalllongitudinal tubes, found in the Early Ordovician limestone of the San Juan Formation, Argentine Precordillera. For more than a hundred years M. argentina was regarded as a bryozoan species. Recently,M. argentina was excluded from the Phylum Bryozoa, erecting the new genus Fiscella of uncertain affinities. Two different forms were recognized: Fiscella argentina (Kayser) and Fiscella jlabelis Carrera. The possible relationship of these organisms with aseptate corals, calcareous algae or gastropod opercula was suggested. Newly discovered material and recentiY published papers allow the taxonomic assignment of these forms to gastropod opercula. Teiichispira argentina (Kayser) is a new combination for Fiscella argentina (Kayser), and the species is transferred to the gastropod genus Teiichispira Yochelson and Jones. Fiscella jlabelis Carrera is an operculum of a macluritacean gastropod. No gastropod shells of the appropriate size and shape which might correspond to the two opercula were found in the same beds. The paleobiogeographic distribution of Teiichispira is restricted to tropical areas as suggested by the paleogeographic position of the localities where this genus was recorded.
A detailed palaeoecological study with sponges and bryozoans was carried out in the Ordovician li... more A detailed palaeoecological study with sponges and bryozoans was carried out in the Ordovician limestones of the San Juan Formation outcropping in the Precordillera of western Argentina. Ten localities were selected for the study along the basin. The San Juan Formation can be subdivided into four intervals according to the major percentages of sponges and bryozoans. These intervals are partially equivalent to brachiopod and conodont zones. An autoecologic study of the sponges and bryozoans is carried out, considering for each taxon its mode of life and the response to the physical conditions of the environment. The interrelations among species of the same group and between this one and other dominant groups such as brachiopods were also analyzed. On the basis of the recognition of the biovolume of each taxon, their influence in the assemblage could be determined. These studies were done at every locality and in the different sections of the formation, and four associations alternatively considered as biofacies or as communities were recognized. Association 1 (community or biofacies of Archaeoscyphia- Calatiumi represents the community present in shallow bioherms of the intemal ramp in a Trernadoc-Early Arenigian sea level rise. Association II (biofacies of Nexospongia-Nicholsonellai represents the association present in the skeletallimestones and tempestites of the mid ramp. Association III (biofacies of stromatoporoids) is found in the reefal and biostromal areas in the inner and middle ramp respectively, during regressive stages. Association IV (biofacies of "elongated" sponges, biofacies of Patellispongia and biofacies of roots-tufts) is developed in shallow and deep reaches of the distal ramp, respectively.Their position in the basin, their environmental conditions, and their bathymetry, were determined. Altogether they indicate a marked stability during the Arenigian and a sea-level drop for the Late Arenigian. The Early Llanvimian (Association IV) is characterized by a relative sea-level rise, although differences in bathymetry were found among the different studied localities. A deeper area toward the north (cerro Viejo region), a shallower area toward the south (Talacasto) and a general deepening toward the west (Las Aguaditas y Las Tunas) were determined.
New linguliform microbrachiopods from the Middle Ordovician are described and illustrated. This f... more New linguliform microbrachiopods from the Middle Ordovician are described and illustrated. This fauna was recovered from the uppermost beds of the San Juan Formation in two sections of the Central Precordillera (Argentina), which are accurately dated to the Lenodus pseudoplanus Zone (middle Darriwilian). The fauna consists of the obolid Luthieria diminuta n. gen. n. sp., and the acrotretids Eoconulus tucunucoensis n. sp., Conotreta andina Lavié, Serra, and Feltes, Scaphelasma zharykensis Popov, and Numericoma rowelli Holmer et al. This low-diversity lingulate association displays close similarities with coeval faunas that inhabited the Laurentia, Baltica, and Kazakhstanian regions, in agreement with evidence from other linguliform and rhynchonelliform brachiopods.UUID: http//zoobank.org/fe9acbb0-6654-4462-ba4d-ea2386ae79f6
... Histórica de la Facultad de Cien-cias Exactas, Físicas y Naturales de la Universidad Nacional... more ... Histórica de la Facultad de Cien-cias Exactas, Físicas y Naturales de la Universidad Nacional de Córdoba. ... PROCEDENCIA: Niveles intermedios, Miembro Las Marías de la Formación Las Aguaditas, cordón de Los Blanquitos al sudoeste de ... Fiel-diana: Geology, 16: 361-376. ...
Specimens of the trepostome bryozoans genus Nicholsonella Ulrich are described and figured. They ... more Specimens of the trepostome bryozoans genus Nicholsonella Ulrich are described and figured. They occur in Arenigian limestones of San Juan Formation. Precordillera basin. Argentina. More than fifteen colonies were collected from a single horizou included in a cyclic succession of intraclastic to. bioclasti c grainsto.ne and skeleral wackestone. The specimens of Nicholsonella encrust skeletal remains, even the interior of some shells, and the surrounding sediment. The encrusting colony as well as the associated coarse-grained sediment suggest high energy conditions. The Arenig paleobiogeographical distribution of Nicholsonella is discussed. The occurrence of this genus shows a world-wide distribution restricted to tropical and subtropical zones.
Although bryozoans have been mentioned in several papers, few systematic descriptions of this gro... more Although bryozoans have been mentioned in several papers, few systematic descriptions of this group are available from the late Paleozoic of western Gondwana, particularly from the Permian sequences. In South America, bryozoan faunas have been reported from the Permian of Venezuela (Laya and Tucker, 2012), Perú, and Bolivia (Sakagami, 1995 and references therein). In Argentina, the late Paleozoic bryozoan faunas have been described mainly from the Carboniferous deposits of the central-western Precordillera Basin (Sabattini, 1986 and references therein). Few Permian records were reported from northwestern Argentina (Arizaro Formation; Aceñolaza et al., 1972) and in the siliciclastic postglacial marine deposits from Patagonia (Sabattini, 2002; Pagani and Taboada, 2010). Permian bryozoan records were mentioned in two sections from northern Chile, with reports of scarce indeterminate forms (Rivano and Sepúlveda, 1985; Díaz Martínez et al., 2000). The aim of this contribution is to provide a new record of a bryozoan species from northernChile, based onmaterial collected from the Cerro El Árbol Formation in the Augusta Victoria area (Fig. 1). The faunal content and the lithological characteristics are analyzed in the context of the paleogeographic position of this area, along the western Gondwana margin.
... grew in a shallow subtidal environment below the fair-weather wave base and which was periodi... more ... grew in a shallow subtidal environment below the fair-weather wave base and which was periodically affected by the storm wave base ... las especies incluyó el conteo numérico de los ejemplares, los valores de biovolumen y la relación altura máxima sobre diámetro máximo (A/ ...
Five genera of anthaspidellid and streptosollenid demosponges are described from the Ordovician L... more Five genera of anthaspidellid and streptosollenid demosponges are described from the Ordovician Lenoir Limestone near Lenoir City, Loudon County, Tennessee, USA including:Rhopalocoelia regularisRaymond and Okulitch,Rugocoelia loudonensisn. sp.,Psarodictyumsp. (Anthaspidellidae),Allosacus pedunculatusn. sp., andZitelella variansRaymond and Okulitch (Streptosolenidae). These findings confirm the major paleobiogeographic picture for Laurentian sponges (i.e., the differential distribution of sponge faunas along both North American margins), because none of these eastern margin species has been reported from western margin faunas. Only one genus typical of the Great Basin fauna,RugocoeliaJohns, 1994, is reported from Tennessee, but as a new species. Possible explanations are discussed for this differential distribution, mainly related to climatic constraints or sedimentary differences, preventing the free distribution of sponge species between Laurentian continental margins.UUID:http://zoobank.org/2b990a4c-7bc8-4eb6-b8a9-fe4ecf7bdbf9
Monticulipora argentina was erected by Kayser to include a conical form composed by smalllongitud... more Monticulipora argentina was erected by Kayser to include a conical form composed by smalllongitudinal tubes, found in the Early Ordovician limestone of the San Juan Formation, Argentine Precordillera. For more than a hundred years M. argentina was regarded as a bryozoan species. Recently,M. argentina was excluded from the Phylum Bryozoa, erecting the new genus Fiscella of uncertain affinities. Two different forms were recognized: Fiscella argentina (Kayser) and Fiscella jlabelis Carrera. The possible relationship of these organisms with aseptate corals, calcareous algae or gastropod opercula was suggested. Newly discovered material and recentiY published papers allow the taxonomic assignment of these forms to gastropod opercula. Teiichispira argentina (Kayser) is a new combination for Fiscella argentina (Kayser), and the species is transferred to the gastropod genus Teiichispira Yochelson and Jones. Fiscella jlabelis Carrera is an operculum of a macluritacean gastropod. No gastropod shells of the appropriate size and shape which might correspond to the two opercula were found in the same beds. The paleobiogeographic distribution of Teiichispira is restricted to tropical areas as suggested by the paleogeographic position of the localities where this genus was recorded.
A detailed palaeoecological study with sponges and bryozoans was carried out in the Ordovician li... more A detailed palaeoecological study with sponges and bryozoans was carried out in the Ordovician limestones of the San Juan Formation outcropping in the Precordillera of western Argentina. Ten localities were selected for the study along the basin. The San Juan Formation can be subdivided into four intervals according to the major percentages of sponges and bryozoans. These intervals are partially equivalent to brachiopod and conodont zones. An autoecologic study of the sponges and bryozoans is carried out, considering for each taxon its mode of life and the response to the physical conditions of the environment. The interrelations among species of the same group and between this one and other dominant groups such as brachiopods were also analyzed. On the basis of the recognition of the biovolume of each taxon, their influence in the assemblage could be determined. These studies were done at every locality and in the different sections of the formation, and four associations alternatively considered as biofacies or as communities were recognized. Association 1 (community or biofacies of Archaeoscyphia- Calatiumi represents the community present in shallow bioherms of the intemal ramp in a Trernadoc-Early Arenigian sea level rise. Association II (biofacies of Nexospongia-Nicholsonellai represents the association present in the skeletallimestones and tempestites of the mid ramp. Association III (biofacies of stromatoporoids) is found in the reefal and biostromal areas in the inner and middle ramp respectively, during regressive stages. Association IV (biofacies of "elongated" sponges, biofacies of Patellispongia and biofacies of roots-tufts) is developed in shallow and deep reaches of the distal ramp, respectively.Their position in the basin, their environmental conditions, and their bathymetry, were determined. Altogether they indicate a marked stability during the Arenigian and a sea-level drop for the Late Arenigian. The Early Llanvimian (Association IV) is characterized by a relative sea-level rise, although differences in bathymetry were found among the different studied localities. A deeper area toward the north (cerro Viejo region), a shallower area toward the south (Talacasto) and a general deepening toward the west (Las Aguaditas y Las Tunas) were determined.
New linguliform microbrachiopods from the Middle Ordovician are described and illustrated. This f... more New linguliform microbrachiopods from the Middle Ordovician are described and illustrated. This fauna was recovered from the uppermost beds of the San Juan Formation in two sections of the Central Precordillera (Argentina), which are accurately dated to the Lenodus pseudoplanus Zone (middle Darriwilian). The fauna consists of the obolid Luthieria diminuta n. gen. n. sp., and the acrotretids Eoconulus tucunucoensis n. sp., Conotreta andina Lavié, Serra, and Feltes, Scaphelasma zharykensis Popov, and Numericoma rowelli Holmer et al. This low-diversity lingulate association displays close similarities with coeval faunas that inhabited the Laurentia, Baltica, and Kazakhstanian regions, in agreement with evidence from other linguliform and rhynchonelliform brachiopods.UUID: http//zoobank.org/fe9acbb0-6654-4462-ba4d-ea2386ae79f6
... Histórica de la Facultad de Cien-cias Exactas, Físicas y Naturales de la Universidad Nacional... more ... Histórica de la Facultad de Cien-cias Exactas, Físicas y Naturales de la Universidad Nacional de Córdoba. ... PROCEDENCIA: Niveles intermedios, Miembro Las Marías de la Formación Las Aguaditas, cordón de Los Blanquitos al sudoeste de ... Fiel-diana: Geology, 16: 361-376. ...
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