PREVOSTI Francisco Juan
congresos y reuniones científicas
NEW VERTEBRATE FOSIL LOCALITIES OF THE SANTA CRUZ FORMATION (EARLY-MIDLE MIOCENE) BETWEEN COYLE AND GALLEGO RIVERS (SANTA CRUZ PROVINCE, ARGENTINA
VIZCAÍNO, S. F., R. F. KAY, M. S. BARGO, J. M. G. PERRY, F. J. PREVOSTI, J. C. FERNICOLA, L. ACOSTA Y M. D. MALINZAK
Jornada; XXII Jornadas Argentinas de Paleontología de Vertebrados; 2006
Coastal exposures of the Santa Cruz Formation between the Coyle and Gallegos rivers have been fertile ground for recovery of late early-early middle Miocene fossil mammals for more than 100 years. In February 2006, we discovered two new localities, notable in their species diversity and completeness of the remains. Both localities, Anfiteatro and Campo Barranca, crop out in the intertidal zone at approximately 3.3 and 7.7 north of the beach entrance at Estancia La Costa respectively. Anfiteatro is equivalent to the lower stratigraphic levels previously reported, and Campo Barranca is approximately 20 meters lower than the lowest level reported. The fossiliferous unit at Anfiteatro is a water-deposited fine tuffaceous clay 1-2 meters thick. No cross-bedding is visible nor did we observe root casts. This unit appears to have been deposited rapidly; a number of fossils extend into the rock to a depth of 20 cm. Seventy-nine specimens were collected including Marsupialia, Xenarthra, Notoungulata, Litopterna, Astrapotheria, Rodentia and Primates. The fossiliferous unit at Campo Barranca is a greenish silty clay. In places the clay is finely laminated - some layers have ripple marks and others are carbon-rich. Elsewhere it is bioturbated, preserving root casts, and has poorly defined bedding. Thirty-nine specimens were collected, including Marsupialia, Xenarthra, Notoungulata, and Rodentia. The genera identified from both localities are consistent with the Santacrucian SALMA. These new localities provide the opportunity to fill an important gap in the evolution of mammals during the earliest part of the Santa Cruz Formation. Anfiteatro offers a window on the structure of a South American mammalian community because allows a temporally precise, taphonomically controlled and intensively sampled collection that documents as much of the skeleton as possible for many species. Thus, the extinct community can be reconstructed using an ecomorphological approach based on functional analysis in a phylogenetic framework.