A stem falconid bird from the Lower Eocene of Antarctica and the early southern radiation of the falcons

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

INTERNATIONAL JOURNAL OF ORNITHOLOGY

Springer

Lugar: Berlin; Año: 2016 vol. 157

1519-888X

Antarctoboenus carlinii gen. et sp. nov. is a large-sized falconiform bird coming from sediments of La Meseta Formation (Lower Eocene) at Seymour (Marambio) Island, West Antarctica. The holotypical tarsometatarsus was originally assigned to Falconidae and its affinities were pointed out with Polyborinae. Detailed osteological and comparative analyses of the Antarctic specimen allowed recognizing the new taxon as a member of the stem group Falconidae, i.e., it is supposed to belong to the early radiation of the falconiform lineage. Antarctoboenus carlinii gen. et sp. nov. distinguishes from members of the crown group Falconidae by having a very shallow sulcus extensorius, a large foramen vasculare distale, an undistinguishable tendinal attachment of the m. adductor digiti II, and short trochleae metatarsi II et IV, among its main diagnostic characters. Purported phylogenetic relationships between A. carlinii and Polyborinae are based on plesiomorphic characters retained in the tarsometatarsus of the latter clade. Our conclusions reinforce the hypothesis about the Neotropical or Austral origin of Falconidae supported by previous molecular phylogenies.