THE FIRST EOCENE BIRD FROM NORTHWESTERN ARGENTINA

A new fossil bird is described from the Upper Lumbrera Formation of Northwestern Argentina. Lumbrerornis rougieri gen. et sp. nov. is represented by three-dimensionally preserved elements of the hindlimb of a single individual. Morphological comparative studies and particular characters of the tibiotarsus suggest that the new species might be related to the extinct clades Palaeotididae and Geranoididae of the Northern Hemisphere, which were recently hypothesized to be Paleogene palaeognathous birds. However, the fragmentary preservation of the new fossil prevents a confident systematic position. The Upper Lumbrera Formation is a widely recognized fossiliferous unit with a very rich fauna of mammals and other vertebrates (e.g., fishes, crocodilians, turtles, snakes). This is the first record of a three-dimensionally preserved fossil bird from the Eocene of northwestern Argentina and thus provides fresh evidence of the Eocene faunas from the area and improves our understanding of the poorly known early Paleogene avifaunas from South America.