Subfamily Leimacomyinae
groove-toothed forest mice

There is just one genus and species in this Old World murid subfamily: the groove-toothed forest mouse (Leimacomys büttneri). Little information is available on this subfamily, as it is only known from two specimens that were collected in 1890. (Musser and Carleton, 2005; Nowak, 1999)

The two specimens representing this group are from Togo, in western Africa. (Nowak, 1999)

The two known tylomyine specimens were found in tropical forest. (Nowak, 1999)

Thomas (1896) included Leimacomys in the subfamily Dendromurinae. Ellerman (1940) and Simpson (1945) placed the genus in the subfamily Murinae, but later authors returned it to Dendromurinae (Carleton and Musser 1984). However, as Musser and Carleton (2005) note, Leimacomys has little in common with dendromurines besides dental charactistics similar to those of Steatomys; specifically, the presence of an additional lingual cusp adjacent to the second row of cusps on the first upper molar and the first row of cusps on the second upper molar. A comprehensive phylogenetic analysis based on dental characteristics resulted in placement of Leimacomys in a clade with gerbillines, not dendromurines (Denys et al. 1995). However, Leimacomys possess a suite of cranial traits unlike those of gerbils so this unique genus is currently regarded as warranting in its own subfamily in the family Muridae (Musser and Carleton 2005). Phylogenetic analyses based on molecular traits will no doubt be neccessary to clarify its relationships to other muroid groups. (Carleton and Musser, 1984; Denys et al., 1995; Ellerman, 1940; Musser and Carleton, 2005; Simpson, 1945; Thomas, 1896)

Groove-toothed forest mice measure about 118 mm long, and the tail adds an extra 37 mm. They are dark brown or gray-brown above and pale gray below. The ears are small and furry. There are four well-developed digits on the forefeet, and five on the hind feet. They have long claws, especially on the hind feet, and naked, scaly tails.

The leimacomyine dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The proodont upper incisors bear shallow grooves, and the third molars are not reduced in size. The upper molar rows diverge anteriorly. Unlike dendromurines, the first crest of each first upper molar is not bicuspid. There is a small posterior cingulum on each first and second upper molar. The bony palate of leimacomyines extends posterior to the rear margins of the molar rows, and the incisive foramina are long and narrow. Groove-toothed forest mice have long, wide rostrums and a broad interorbital region with beaded edges. They have low temporal ridges and small auditory bullae. The zygomatic plates are relatively broad, and the anterior portion of each extends forward past the zygomatic arches in a conspicuous spine. The masseteric knob or tubercle is poorly developed. (Carleton and Musser, 1984; Nowak, 1999)

The lifespan of leimacomyines is unknown.

Nothing is known about the behavior of these rodents, except that they are probably terrestrial. (Carleton and Musser, 1984; Nowak, 1999)

Groove-toothed forest mice presumably sense visual, tactile, auditory, and chemical cues, as most mammals can, but the acuteness of these senses and the way in which they communicate with one another is unknown.

Groove-toothed forest mice are presumed to be at least partially insectivorous. (Nowak, 1999)

There are no reports of predation on leimacomyines.

If groove-toothed forest mice are indeed insectivorous, then they have a role as secondary consumers. They are most likely preyed upon by higher-level consumers as well.

There are no known negative effects of leimacomyines on humans.

There are no known positive effects of leimacomyines on humans.

Because so little is known about it, including whether or not it still exists, Leimacomys is listed as data deficient by the IUCN. No surveys of the area where the two known specimens were found have been undertaken to date. (Van der Straeten and Schlitter, 2004)