Miscelánea 12
Relaciones Biogeográficas entre los Moluscos del Mioceno Tardío y Reciente del Atlántico Sudoccidental
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The present paper is an updated synthesis of the biogeographic aspects and circulation patterns of the “Entrerriense-Paranense”sea that flooded the Argentinean and Uruguayan littorals during Miocene times.
Based on its highly diverse and abundant molluscan fauna, Martínez and del Río (2002a, b) defined the Valdesian and Paranaian Bioprovinces, both units characterized by a surprisingly high number of Caribbean taxas. These Tertiary provinces did not give rise to the Recent Molluscan ones of the area (Argentinean and Magallanean Provinces) because these latter units lack of Caribbean elements, record only a low percentage of Miocene surviver genera (only 10%) and, in turn, because the Recent biogeographic units are characterized by the firts occurrence of post-Miocene Magallanic taxas. Compositional variation of faunal assemblages indicates an incipient latitudinal thermal gradient from Uruguay south to northern Patagonia during the Miocene.
