Although a Nesomyidae per se had been earlier recognized by Tullberg (1899), Weber (1904), and later Chaline et al. (1977), theirs was essentially a grouping of the indigenous Malagasy rodents as already identified by Major (1897; Chaline et al. also included the otomyines, a clade clearly allied with murids—see those accounts). Although differing in contents, the family composition observed here owes its conceptual roots to Lavocat (1973, 1978), who identified a number of small but morphologically well-defined groups as relicts of a middle Tertiary (late Oligocene-early Miocene?) cricetodontine presence in Africa and expanded the definition of Nesomyidae to embrace their diverse descendants (also see Carleton and Musser, 1984:344). The results of DNA hybridization and mitochondrial and nuclear gene-sequence studies, although not wholly concordant, have supplied some empirical basis for Lavocat’s view of Nesomyidae, associating Cricetomyinae, Dendromurinae, Mystromyinae, and Nesomyinae in a monophyletic lineage basal to other muroid taxa representing Cricetidae and Muridae (DuBois et al., 1996; Jansa et al., 1999; Michaux and Catzeflis, 2000; Michaux et al., 2001b).

Fossil representatives of Nesomyidae, as construed here, date from the early Miocene of Africa (see individual subfamily comments), with extinct taxa such as Notocricetodon and Protarsomys (Afrocricetodontinae sensu Lavocat, 1973, 1978) variously implicated in the origin of several of the living genera and-or subfamilies. The paleontological argument for such phyletic links remains sketchy and the hard evidence from critical middle Tertiary beds is scanty. Such Tertiary discoveries nonetheless continue to emerge from Africa and will help much to illuminate the validity of a family Nesomyidae upon their critical study. The alternative possibility obviously demands attention: do the subfamilies associated here form a polyphyletic wastebasket for the remnants of early evolutionary branches within other major radiations of Muroidea, by implication Cricetidae or Muridae? This is the considered view of Tong and Jaeger (1993:56) regarding Lavocat’s expansive concept of Nesomyidae. Mustering evidence to tease apart these hypotheses will require denser taxonomic sampling in molecular studies and broader appeal to organ systems other than the dentition in morphological investigations.