Diplodon cf. colhuapiensis (Bivalvia, Hyriidae) in the Santa Cruz Formation (Early–Middle Miocene) at the Río Santa Cruz, Patagonia, Argentina

PÉREZ, L. M.; CUITIÑO, J. I.; VARELA, A. N.; MUÑOZ, N. A.

La Plata

Congreso; Reunión de comunicaciones de la Asociación Paleontológica Argentina; 2019

Asociación Paleontológica Argentina

The Santa Cruz Formation (early–middle Miocene) is one of the most widespread sedimentary units of Argentine Patagonia. This unit contains an abundant and taxonomically diverse fauna of fossil vertebrate, especially mammals. Thus, the paleoecological and paleoenvironmental information the unit has derived mainly from the analysis of the vertebrate assemblages it contains, as well as from ichnological and paleobotanical evidence. The record of freshwater bivalves assigned to Diplodon cf. colhuapiensis Ihering, 1903 from the Santa Cruz Formation collected at Barrancas Blancas (Estancia Santa Lucía) on the Río Santa Cruz suggests a unique paleoenvironmental setting during the deposition of the bearing levels. Considering this record, we propose that Diplodon cf. colhuapiensis originally assigned to the Late Cretaceous/Paleogene could have come from the early–middle Miocene of Santa Cruz Formation. In this sense, the specimens referred to Diplodon cf. colhuapiensis suggest the existence of an established community of Hyriidae mollusks at the upper-middle levels of the Santa Cruz Formation. The presence of freshwater bivalves suggests that the depositional environment of this unit included the existence of water courses. The identification of the genus in the Santa Cruz Formation extends its southernmost range down to the latitude of the Río Santa Cruz (~ 50º S).