New fossil bird remains from the Chichinales Formation (Early Miocene) of northern Patagonia, Argentina.

Here we describe isolated avian remains coming from the Chichinales Formation, at the Paso Córdoba locality, Río Negro province, Patagonia, Argentina. Present report constitutes the first analysis of an Early Miocene bird association in South America outside the Santa Cruz and Chubut provinces, and one of the scarce reports of avian remains for the Colhuehuapian SALMA. The remains represent a new genus and species of phorusrhacid ( Patagorhacos terrificus gen. et sp. nov.), a new species of rheid ( Opisthodactylus horacioperezi sp. nov.), and an indeterminate charadriiform. Although different in composition, the presence and relative abundance of rheids and phorusrhacids is a pattern that is also present in other Early Miocene Patagonian assemblages, especially those from the Santacrucian SALMA. In spite of such similarities, the description of new taxa indicates that the Chichinales faunas were different to some degree from other Early Miocene bird assemblages. [ABSTRACT FROM AUTHOR]