New Anhingid (Aves, Suliformes) from the Middle Miocene of Río Negro Province, Patagonia, Argentina

AGNOLIN, FEDERICO; DIEDERLE, JUAN M.; NORIEGA, JORGE IGNACIO

Diamante

Congreso; 9th International Meeting of the Society of Avian Paleontology and Evolution (SAPE); 2016

CICYTTP-MLP-CICTERRA-MACN

Darters or snake birds are diving birds of the family Anhingidae that live in tropical and subtropical climate, mainly in freshwater habitats. In South America the giant diving anhingids are one of the most conspicuous faunistic elements of the Miocene avifaunas. However, the family record from Patagonia is still sparse, being composed by Anhinga hesterna (Ameghino 1895) and an indeterminate species of the genus Macranhinga, both coming from the late Early Miocene of Santa Cruz Province, Argentina, and Meganhinga chilensis Alvarenga 1995 from the late Early Miocene of Malleco Province, Chile. The aim of the present contribution is to describe a new species of Macranhinga coming from Colloncuran levels of an unnamed stratigraphic unit (Middle Miocene of southwestern Puesto Marileo, near Ingeniero Jacobacci city, Río Negro Province, north-central Patagonia. The new species is represented by an incomplete proximal end of tarsometatarsus, distal end of tibiotarsus, and distal end of humerus that differ from other species of the genus in a unique combination of characters. It is noteworthy that together with their very large size (more than 50% larger than species of Anhinga) and robustness, South American Neogene darters share a number of features that indicate they may belong to a monophyletic clade. An overview of the anhingid record suggests that the purported phororhacoid Pseudolarus eocaenus Ameghino 1895, coming from the Miocene of Santa Cruz Province, may also belong to Anhingidae. New and old records from the Miocene of Patagonia indicate that the family diversity was far more diverse that currently understood, being possibly comparable to that exhibited in northeastern Argentina and Brazil.