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| Sorrentino,Leonor; Benedetto,Juan L; Carrera,Marcelo G. |
| Los niveles cuspidales de la Formación San Juan en el cordón del Cerro Viejo (NE de Jáchal) corresponden a depósitos de rampa carbonática media a distal. Este intervalo, del Darriwiliano inferior, muestra una tendencia general transgresiva variando desde packstones-wackestones microbioclásticos en la parte inferior hasta mudstones nodulares en la parte superior. La mayoría de las capas contienen una rica fauna de braquiópodos rinconelliformes. Las formas dominantes son los plectambonitoideos Ahtiella argentina, Leptella (Petroria) rugosa y Taffia (Chaloupskia) anomala y los ortoideos Paralenorthis vulgaris y Orthidium geniculatum. Otros taxones, tales como Productorthis, Martellia, Inversella (Reinversella) y Sanjuanella plicata, son menos abundantes y... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Diversidad; Morfotipos; Braquiópodos; Ordovícico; Precordillera Argentina. |
| Ano: 2009 |
URL: http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0002-70142009000300004 |
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| Carrera,Marcelo G; Ortega,Gladys. |
| A nearly complete specimen of a hexactinellid sponge has been recovered from Lower Ordovician siliciclastic rocks of the Argentine Precordillera. The material was collected in the upper member of the Los Azules Formation (Sandbian). A new species of the genus Cyathophycus Walcott, C. extendis, is erected. The taxonomic position of the genus is still controversial. Their recent assignment to the family Dictyospongiidae is discussed; Cyathophycus has been considered as a transitional form between protospongiids with simple regular skeletons and dictyospongiids with more complex skeletons. Previous studies have stated that hexactinellid evolution through the Cambrian-Ordovician interval, like other sponge groups at this time, appears to have been based on... |
| Tipo: Info:eu-repo/semantics/article |
Palavras-chave: Porifera; Hexactinellida; Ordovician; Argentina. |
| Ano: 2009 |
URL: http://www.scielo.org.ar/scielo.php?script=sci_arttext&pid=S0002-70142009000300001 |
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