Aquila (bird)
Aquila is the genus of true eagles. The genus name is Latin for "eagle", possibly derived from "aquilus", "dark in colour". It is often united with the buteos, sea eagles, and other more heavyset Accipitridae, but more recently they appear to be less distinct from the more slender accipitrine hawks than previously believed. Eagles are not a natural group, but denote essentially any bird of prey large enough to hunt sizeable (about 50 cm long or more overall) vertebrate prey. Taxonomy and systematics. The genus "Aquila" was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with  the golden eagle ("Aquila chrysaetos") as the type species. "Aquila" belongs to a close-knit group of "typical" eagles including genera Hieraaetus, "Lophaetus", "Ictinaetus" "and Clanga." This group occurs as a clade within the larger group of "booted" eagles (tribe Aquilini or subfamily Aquilinae). The plumage of the more basal members of the booted-eagle group, such as "Spizaetus" and "Nisaetus", generally has barred underparts in adults, and is distinctly different in juveniles which have plain, pale underparts. In contrast, within the "Aquila–Hieraaetus–Lophaetus" clade, adults are generally dark, with juveniles more closely resembling the adults. "Hieraaetus" species have  both dark and light (or "pied") morphs, with the latter having light, unbarred under-parts. Research in molecular genetics found "Aquila" and "Hieraaetus" to be polyphyletic. Between 2005 and 2014, the British Ornithologists' Union included both Bonelli's and the booted eagle in "Aquila". Also, "Clements' Checklist" merged all "Hieraetus" species into "Aquila" from 2001 to 2009. The current approach is to keep "Hieraaetus" as a separate genus, with Bonelli's eagle and the African hawk-eagle moved into "Aquila" and Wahlberg's eagle moved into "Hieraaetus". The spotted eagles greater spotted eagle, lesser spotted eagle, and Indian spotted eagle  (previously "Aquila clanga", "A. pomarina", "A. (p.) hastata") are thought to be genetically closer to "Ictinaetus" and "Lophoaetus" than to other "Aquila" species, and may be placed into a separate genus, "Clanga". Members of "Aquila" (excluding those moved to "Clanga" and "Hieraaetus", but including "A. fasciata/spilogaster") share two deletions in the (nuclear) LDH gene, as well as similarities in mitochondrial cyt-B gene sequence, though one of these deletions is reverted in "A. chrysaetos". Species. The genus "Aquila" contains 11 species: Fossil record. Numerous fossil taxa of eagles have been described. Many have been moved to other genera, but  several appear to be correctly assigned to this genus: Whether ""Hieraaetus" edwardsi" (Middle -? Late Miocene of SW Europe) belongs into "Aquila" or the hawk-eagles (if the latter are indeed distinct) is unclear. Its initial name, ""Aquila" minuta" , is preoccupied by a junior synonym of the booted eagle, "A. minuta" . Not placed in "Aquila" anymore are: ""Aquila" danana" (Snake Creek Late Miocene/Early Pliocene of Loup Fork, USA), occasionally placed in "Geranoaetus" or "Buteo", was a bird of prey of unclear relationships.