A stem Falconiform bird from the Lower Eocene of Antarctica

CENIZO, MARCOS; NORIEGA, JORGE I.; REGUERO, MARCELO

Zapala/ El Chocón

Jornada; XVIII Jornadas Argentinas de Paleontología de Vertebrados; 2014

MOZ/MEB/FHN

The crown group Falconidae are small to medium-sized predatory birds present in all habitats around the world except Antarctica, with most of the extant diversity concentrated in the Neotropics. They are grouped in the subfamilies Falconinae (True falcons, Falconets, Kestrels, and Caracaras) and Herpetotherinae (Laughing and Forest falcons). The fossil record of falconids is poor and fragmentary, providing little evidence about the purported South American origin of the basic stocks that gave rise to their main clades.The specimen herein described is housed at the paleontological collections of the Museo de La Plata (MLP 95-I-10-8) and consists of the distal end of a left tarsometatarsus. The material comes from Cucullaea I Allomember of La Meseta Formation which outcrops at IAA 2/95 locality, Seymour Island (Marambio). Radiometric dates indicate an Early Eocene age (Ypresian) for the bearing fossil level, ranging between 49-51 Ma. The Antarctic fossil was originally referred to Polyborinae (Caracarini) based on its overall resemblance; however, reanalysis of morphological characters and detailed comparisons allow us to exclude MLP 95-I-10-8 specimen from the crown group, recognizing it as a new basal falconiform genus. The undoubted stem group position of this taxon, as well as the age and geographic provenance of the record, reinforce the hypothesis about a South American-Antarctic origin for the group.