"Annularia mucronata Schenk, un taxón paleoecuatorial en la flora eopérmica de la Formación Río Genoa, Chubut, Argentina"

Abstract

"Well preserved whorled axes of Annularia rnucronaia Schenk are described. Morphological attributes as well as some epidermic/hypodermic features preserved as impressions, allow a complete assignation of the studied material to the amerosinian species. This record from the lowermost Permian of Patagonia is the earliest stratigraphical occurrence of the genus in the southern hemisphere. Based on the exclusive distribution of the taxon along the paleoecuatorial belt, a characteristic also shown by other plant taxa from the Río Genoa Formation, the record of this taxon might be the result of an ecotonal geographical location of Patagonia during la test Carboniferous-earliest Permian times. lt is also suggested that a radiation of this group of calamitalean sphenophytes was initiated from the Patagonian area, arriving later, by the late-Early Permian, to other western Gondwana areas such as Brazil and South Africa, also involving an speciation process."