Bats (Chiroptera) are generally considered to be monophyletic based on morphological and molecular data (Simmons, 1998; Gunnell and Simmons, 2005; Teeling et al., 2005), but the relationships among the families, especially extinct families, are not well resolved (Simmons and Geisler, 1998; Gunnell and Simmons, 2005). Recent molecular phylogenetic work suggests that one group of bats, the Noctilionoidea, consists of a monophyletic clade including at least the families Mystacinidae, Mormoopidae, Noctilionidae and Phyllostomidae (Pierson et al., 1986; Kirsch et al., 1998; Kennedy et al., 1999; Van Den Bussche and Hoofer, 2000; Teeling et al., 2003; Hutcheon and Kirsch, 2004), and probably also the families Thyropteridae, Furipteridae and Myzopodidae (Hoofer et al., 2003; Van Den Bussche and Hoofer, 2004; Teeling et al., 2005; Miller-Butterworth et al., 2007), although Hoofer et al. (2003) explicitly excluded Myzopodidae. Gunnell and Simmons (2005) found morphological data supporting a more restricted Noctilionoidea composed of the first four families, Mystacinidae, Noctilionidae, Phyllostomidae and Mormoopidae, but which is sister to a clade composed of Myzopodidae, Thyropteridae, Furipteridae and Natalidae. Early fossils of noctilionoid bats are scarce; reviewed below are some pre-Pleistocene records of noctilionoids and putative noctilionoids as fossils.
The oldest Paleogene bat fossils known from South America are two isolated teeth from the Early Eocene of Chubut, Argentina, that could potentially represent a noctilionoid (Tejedor et al., 2005, 2009), but the specimens are actually insufficient to realize the phylogenetic affinities of the taxon they exemplify. A possible ?bat represented by a single broken tooth of uncertain but possibly Eocene age from Santa Rosa, Peru, has a dental character rather similar to one that is unique to noctilionids, but this specimen, too, is unsubstantial (Czaplewski and Campbell, 2004).