The southernmost records of Anhingidae and a new basal species of Anatidae (Aves) from the lower–middle Miocene of Patagonia, Argentina

CENIZO, MARCOS; AGNOLIN, FEDERICO

ALCHERINGA

TAYLOR & FRANCIS LTD

Lugar: Londres; Año: 2010 p. 1 - 22

0311-5518

New bird fossils from the Santa Cruz Formation (lower–middle Miocene), Santa Cruz Province, Patagonia,Argentina, are described. They represent an indeterminate species of the extinct anhingid Macranhinga and a newgenus and species of basal Anatidae Ankonetta larriestrai. The record of the giant darter Macranhinga constitutesthe southernmost record for the family, and expands the known stratigraphic range of the genus, previouslyrestricted to the upper Miocene. Based on an analysis of the fossil anhingid record from South America, wehypothesize that giant darters disappeared from South America in the early Pliocene due to climatic deterioration,regression of marine and freshwater environments, the arrival of placental carnivorous mammals, and alsoprobably by competition with phalacrocoracid cormorants. The new anatid Ankonetta is based on an incompletebut informative tarsometatarsus, with superficial similarities to extant Dendrocygna. A brief overview of severalfossil ducks from the Patagonian Cenozoic concludes that most pre-Pliocene examples belong to non-anatine taxa,indicating that plesiomorphic ducks were the dominant anseriforms in those times, a pattern also evident on othercontinents.