Two new fossil eagles from the late Pliocene (late Blancan) of Florida and Arizona and their biogeographic implications

Two new species of fossil eagles are described from the late Pliocene of Florida and Arizona, adding new information on the paleoecology of these regions. Aquila bivia, new species, is known from 33 skeletal elements from Inglis 1A, Citrus County, Florida, and from a partial skeleton from ill Ranch, Graham County, Arizona. It was a large eagle, approximately 10%-15% larger than females of modern A. chrysaetos (Linnaeus), and it is the first valid fossil species in this genus to be described from North America. Amplibuteo concordatus, new species, is known from 13 skeletal elements from Haile 7C, Alachua County, and Inglis IC, Citrus County, Florida, and from three specimens from Duncan, Greenlee County, Arizona. It is the third species of the genus to be described, and it represents the earliest occurrence of this genus. These two new taxa add to a growing list of vertebrates with fossil distributions in both the Florida peninsula and western North America, which reflects a corridor of common habitat that once united these regions. This corridor initially developed during glacial intervals in the late Pliocene, when numerous taxa of mammals, birds, reptiles, and plants first appear in the fossil record of Florida. The corridor probably was composed largely of dry thorn-scrub and savannah communities, but it also may have had a mosaic of lakes, wetlands, and hammocks that allowed dispersal of a variety of species that reflect these communities.