A NEW SPECIES OF RHEA (AVES: RHEIDAE) FROM THE LATE MIOCENE OF THE MESOPOTAMIA IN ARGENTINA

A NEW SPECIES OF RHEA (AVES: RHEIDAE) FROM THE LATE MIOCENE OF THE MESOPOTAMIA IN ARGENTINA. A new species of rhea, Pterocnemia mesopotamica sp. nov. (Ayes: Rheidae), from the late Miocene of Mesopotamia in Argentina is described. Specimens come from the base of the Ituzaingo Formation (= "Conglomerado osifero" or "Mesopotamiense"), which crops out along the cliffs of the Parana river near the homonimous city in Entre Rios Province. Pterocnemia mesopotamica sp. nov. is a slender and small-bodied bird, similar in size to the lesser rhea or choique (P. pennata), and characterized by the marked divergence of the tarsometatarsal trochleae. Fragmentary remains of a femur and a humerus, identified as Rheidae indet., are also reported from the same locality and horizon. An isolated tarsometatarsus, coming from the Aisol Formation in Mendoza Province, is referred to Pterocnemia cf. P mesopotamica sp. nov. If this record is confirmed, the biochron of the new taxon would extend back from the late Miocene (Huayquerian Age) to the middle Miocene (Friasian Age).