Avian and mammal footprints from a Neogene peri-marine wetland (Pozo Salado, Rio Negro province, Argentina)

PAOLO CITTON; CARATELLI MARTINA; ROMINA MONTES; SILVIA DE VALAIS; CARLOS CONSOLE-GONELLA; ARCHUBY FERNANDO; DÍAZ-MARTÍNEZ IGNACIO

Virtual

Congreso; 3rd Palaeontological Virtual Congress; 2021

3rd Palaeontological Virtual Congress

The vertebrate ichnofauna from the Neogene Río Negro Formation is represented by mammal and avian footprints reported from different localities of the coast of northern Patagonia and Pampean region. A new track-bearing locality in the unit was recently found close to Pozo Salado, on the tide-dominated Atlantic shoreline of the Punta Mejillón area (Río Negro province, Argentina). The trackmakers were crossing an emergent, fine- to medium-grained, sandy flat of a peri-marine wetland. Some tracks present folds in the surface related with microbially induced sedimentary structures, playing a significant role in track preservation. As suggested by extramorphological track features, the surface and subsurface remained compliant to producers of different size-classes, probably during a relatively long time of exposure and trampling. The tracksite presents abundant footprints but relatively low ichno-diversity. Avian tracks are the most common, although caviomorph and megatherian tracks have also been identified. Few footprints display clear morphology and were classified as Gruipeda cf. maxima and cf. Porcellusignum isp., two ichnotaxa classically related to gruiform/ciconiiform birds and hydrochoerid rodents, respectively. Shorebird and waterbird tracks are a component of the shorebird ichnosubfacies within the Scoyenia ichnofacies, classically accompanying a prominent suite of invertebrate traces like Taenidium, Skolithos and Helmintoidichnites, apparently lacking in the studied ichnoassociation. The new finding enriches the vertebrate track record from the Atlantic coast of the Río Negro province and invites to further discuss the reliability and significance of this type of tracks in refine palaeoenvironmental, palaeoecological and ichnofacial reconstructions.