Micromys Dehne 1841

Micromys Dehne 1841, Micromys agilis, Ein Neues Saugetier der Fauna von Dresden: 1.

Type Species: Micromys agilis Dehne 1841

Species and subspecies: 1 species:

Species Micromys minutus (Pallas 1771)

Discussion: Micromys Division. Generic diagnosis based upon molar traits provided by Storch (1987). Molar morphology indicates a close relationship with members of Misonne’s (1969) Progonomys group (within a more inclusive Lenothrix-Parapodemus Division), and phylogenetic relationships assessed by microcomplement fixation of albumin (Watts and Baverstock, 1995 b) pointed to the Asian Vandeleuria (also a member of Misonne’s Progonomys cluster) as the closest living relative of Micromys, an alliance hinted at by Jüdes’s (1981) interpretation of chromosomal data, and explicitly indicated by Ellerman (1949:132) based upon morphology. Phylogenetic analyses of complete mtDNA cytochrome b sequences by Martin et al. (2000) could not resolve the phylogenetic position of Micromys relative to other murines and deomyines sampled ( Apodemus, Mus, Rattus, Acomys), nor could analyses of sequences from the nuclear LCAT (Robinson et al., 1997); neither of these studies included Vandeleuria . Micromys possesses a quality of the Lx family of long interspersed repeated DNA compared with other extant murines sampled ( Mus, Praomys, Rattus, Bandicota, Arvicanthis, Mastomys, Hylomyscus, Aethomys, Dasymys, and Apodemus) that indicates it to be the most divergent of those genera and an outgroup to them (Furano et al., 1994). Those authors speculated that Micromys diverged early from the core murine lineage, an observation consistent with scnDNA hybridization data (Catzeflis et al., 1992), analyses of sequences from nuclear IRBP gene, and mtDNA cytochrome b and 12S rRNA (Michaux et al., 2002 a), and the early presence of the genus and phylogenetic history in the Neogene. Micromys may have been the first lineage to have diverged from a common ancestral Progonomys like form approximately 12 million years ago (Furano et al., 1994). Based upon her cladistic analysis of molar traits, Chaimanee (1998) suggested the Indomalayan Vandeleuria, Lenothrix, and Pithecheir are also members of this primary divergent lineage.

The early evolutionary origin of Micromys is reflected in its phylogenetic history documented by fossils representing ten extinct species: one from the late Miocene of Nei Mongol (Storch, 1987), seven from the late Miocene, Pliocene, and Pleistocene of Europe, one of which occurs in Europe and Nei Mongol (Qiu and Storch, 2000; Weerd, 1979; see Storch and Dahlmann, 1995, who reviewed all the fossil species of Micromys), one from the early to late Pliocene of S China (Cai and Qiu, 1993; Wu and Flynn, 1992), and another from the early Pleistocene of S China (Zheng, 1993). "The fossil Micromys species do not represent a single lineage which finally leads to the living M. minutus .... the genus underwent radiations and shows a rather complex phylogenetic history" (Storch and Dahlmann, 1995:128). Only one living species is recognized by most workers, but whether extant samples represent one or more species has yet to be resolved by critical systematic revision.