PHYLOGENY AND TAXONOMY OF THE PATAGONIAN MIOCENE FALCON THEGORNIS MUSCULOSUS AMEGHINO, 1895 (AVES: FALCONIDAE)

NORIEGA JI; ARETA JI; VIZCAÍNO S; BARGO S

JOURNAL OF PALEONTOLOGY

PALEONTOLOGICAL SOC INC

Año: 2011 vol. 85 p. 1089 - 1104

0022-3360

The fossil record of the family Falconidae is poor and fragmentary. Extinct representatives from SouthAmerica include the early-middle Miocene (Santacrucian) Thegornis musculosus and Thegornis debilis. Both specieswere originally described as Falconidae and afterwards moved to Accipitridae Circinae or Buteoninae. The analysisof a very well preserved and complete specimen of T. musculosus with similar stratigraphic and geographicprovenances of the type material (lower levels of Santa Cruz Formation, coast of Patagonia, Argentina)corroborates the validity of the genus and its falconid affinities. The skull and postcranial morphology exhibit strongresemblances with the open-savannah inhabiting Herpetotheres and the forest-dwelling Micrastur (Herpetotherinae)but differ substantially from Falconinae (Falconini plus Caracarini). Detailed comparisons with a broad arrange offalconiform taxa in a cladistic framework, confirm its phylogenetic placement within the Herpetotherinae and sisterto H. cachinnans. The ecotonal margins produced by the vanishing of humid forests that developed during changesin Patagonian plant communities throughout early Neogene times are hypothesized as a plausible scenario tounderstand the evolution of this basal clade of falcons.