CONICET | Buscador de Institutos y Recursos Humanos

The vertebrate ichnofauna from the Neogene R o Negro Formation isrepresented by mammal and avian footprints reported from di!erentlocalities of the coast of northern Patagonia and Pampean region. Anew track-bearing locality in the unit was recently found close to PozoSalado, on the tide-dominated Atlantic shoreline of the Punta Mejill narea (R o Negro province, Argentina). The trackmakers were crossing anemergent, "ne- to medium-grained, sandy #at of a peri-marine wetland.Some tracks present folds in the surface related with microbially inducedsedimentary structures, playing a signi"cant role in track preservation.As suggested by extramorphological track features, the surface andsubsurface remained compliant to producers of di!erent size-classes,probably during a relatively long time of exposure and trampling.The tracksite presents abundant footprints but relatively low ichnodiversity.Avian tracks are the most common, although caviomorph andmegatherian tracks have also been identi"ed. Few footprints displayclear morphology and were classi"ed as Gruipeda cf. maxima andcf. Porcellusignum isp., two ichnotaxa classically related to gruiform/ciconiiform birds and hydrochoerid rodents, respectively. Shorebird andwaterbird tracks are a component of the shorebird ichnosubfacies withinthe Scoyenia ichnofacies, classically accompanying a prominent suiteof invertebrate traces like Taenidium, Skolithos and Helmintoidichnites,apparently lacking in the studied ichnoassociation. The new "ndingenriches the vertebrate track record from the Atlantic coast of theR o Negro province and invites to further discuss the reliability andsigni"cance of this type of tracks in re"ne palaeoenvironmental,palaeoecological and ichnofacial reconstructions.