The record of birds from the Santa Cruz Formation (Early?Middle Miocene) at the Río Chalía valley, Patagonia, Argentina

NORIEGA, JORGE I.; CENIZO, MARCOS; VIZCAÍNO, S.; BARGO, S.; DIEDERLE, JUAN M.

Mendoza

Congreso; 34ºJornadas Argentinas de Paleontología de Vertebrados; 2021

IANIGLA

The Santa Cruz Formation (early?middle Miocene, Patagonia) is relevant for its abundant fossil record and relative richness of bird taxa. It crops out in several areas of the Santa Cruz Province (Argentina), being largely exposed in the central region along the valleys of the Santa Cruz and Chalía (= Sehuén) Rivers. The avian record from Chalía (c. 18 and 15.2 Ma) is poorly known. New collections made during 2017?2019 (belonging to the Museo Regional Provincial Padre M. J. Molina, Río Gallegos) allow us to identify a Rheidae (Opisthodactylus patagonicus), a Tinamidae (gen. et sp. indet.), four Phorusrhacidae (Phorusrhacos longissimus, Patagornis marshi, Psilopterus lemoinei, and P. bachmanni), two Anatidae, an Anhingidae (cf. Macranhinga sp.), and a charadriiform. The Tinamidae belongs to a clade previously recognized phylogenetically as intermediate between Tinaminae and Nothurinae. One anatid is very similar to Dendrocygna. The other cannot be compared with other Santacrucian (or Deseadan) anatids because they are based on non-homologous fragmentary elements. The morphology of its humerus is more primitive than that of modern Anatini, considering the shape and location of the tuberosities and the development of the capital shaft ridge. The Anhingidae cannot be compared either with any of the Miocene Patagonian species. The charadriiform is preliminarily identified only at ordinal level. So far, the taxonomic richness and diversity is reduced in comparison with the overall avian record of the Santa Cruz Formation (at least 17 species included in 15 genera and nine families).