RESUMO
Eptesicus Rafinesque, 1820 is widely distributed in the Old and New World (26 species), and Histiotus Gervais, 1856 is a South American endemic (11 species). Molecular phylogenies have recovered Eptesicus (sensu lato) as polyphyletic, with New World Eptesicus and the sister genus Histiotus in a paraphyletic American clade sister to Old World Eptesicus. Based on these phylogenetic reconstructions, authors have treated Histiotus as either a subgenus of Eptesicus or restricted Eptesicus to the New World species, treating Histiotus as a full genus, and using the name Cnephaeus Kaup, 1829 at the generic rank to comprise Old World Eptesicus. Based on recently published molecular studies, and on novel qualitative and quantitative morphological comparisons of representatives of Histiotus and New and Old World Eptesicus, we provide evidence for restricting the name Eptesicus to the species E. fuscus (Palisot de Beauvois, 1796) and E. guadeloupensis Genoways & Baker, 1975, allocating the remaining New World species under a new genus, keeping Histiotus as a full genus, and raising Cnephaeus to generic rank to comprise all Old World taxa currently under Eptesicus. This arrangement resolves the paraphyly of New World Eptesicus, and promotes taxonomic stability for Histiotus, which is a well-established genus of easily recognizable Neotropical bats and treated separate from Eptesicus by most authorities.