Caspian-like relict molluscan fauna in the South American Permian. Bulletin of the AMNH ; v. 146, article 1

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New York : [American Museum of Natural History]
"Fossiliferous sediments of Permian age occupy an area in the Paraná Basin of Brazil, Uruguay, Paraguay, and Argentina equivalent to about one and one-half times the size of the Gulf of Mexico. The Estrada Nova Formation, ranging from 100 to 1000 meters thick near the middle of the Permian section, contains a widely distributed and diverse fauna of bivalve molluscs made known by J. Camargo Mendes and others. Many of these are silicified and very well preserved. The fauna is remarkable in being wholly confined, so far as is known, to the Paraná Basin. A critical review of the bivalves undertaken in the present paper shows that their family affinities are with marine Gondwana forms found in underlying strata (Tubarão Group) and in other Gondwana continents. The remarkable endemicity of the Estrada Nova fauna and carbon isotope paleosalinities suggest intrabasinal evolutionary radiation under conditions of brackish water and extreme isolation. The history of this relict sea compares favorably with the well-documented, extraordinary history of the Pontian Sea of southeastern Europe of late Cenozoic times and is reminiscent of 'sympatric' evolution of the fishes of east African lakes. The taxonomy of 24 generic and 57 specific names employed for the Permian bivalves is revised and their biologic and ecologic significance is analyzed"--P. 5.
66 p. : ill., maps ; 27 cm.
Includes bibliographical references (p. 62-66).