Taxonomy and Nomenclature
The New World vultures comprise seven species in five genera. The genera are Coragyps, Cathartes, Gymnogyps, Sarcoramphus, and Vultur. Of these, only Cathartes is not monotypic. The family's scientific name, Cathartidae, comes from cathartes, Greek for "purifier". Although New World vultures have many resemblances to Old World vultures they are not very closely related. Rather, they resemble Old World vultures because of convergent evolution.
New World vultures were traditionally placed in a family of their own in the Falconiformes. However, in the late 20th century some ornithologists argued that they are more closely related to storks on the basis of karyotype, morphological, and behavioral data. Thus some authorities place them in the Ciconiiformes with the storks and herons; Sibley and Monroe (1990) even considered them a subfamily of the stork family. This has been criticized as an oversimplification, and an early DNA sequence study was based on erroneous data and subsequently retracted. Consequently, there is a recent trend to raise the New World vultures to the rank of an independent order Cathartiformes not closely associated with either birds of prey or storks or herons. In 2007 the American Ornithologists' Union's North American checklist moved Cathartidae back into the lead position in Falconiformes, but with an asterisk that indicates it is a taxon "that is probably misplaced in the current phylogenetic listing but for which data indicating proper placement are not yet available". The AOU's draft South American checklist places the Cathartidae in their own order, Cathartiformes. However, a recent multi-locus DNA study on the evolutionary relationships between bird groups indicates that New World vultures are related to the other birds of prey, excluding the Falconidae which are distantly related to other raptors. In this analysis, the New World vultures should be part of a new order Accipitriformes instead. In 2010, the family remains in the Ciconiiformes order in the AOU's North American check-list.
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