Stenocephalemys albipes (Rüppell 1842)

[Stenocephalemys] albipes (Rüppell 1842), Mus . Senckenberg., 3: 107.

Type Locality: Ethiopia, Massawa.

Vernacular Names: White-footed Stenocephalemys.

Synonyms: Stenocephalemys alettensis (Frick 1914); Stenocephalemys ankoberensis (Frick 1914); Stenocephalemys leucopus (Fitzinger 1867); Stenocephalemys minor (Heuglin 1877) .

Distribution: Ethiopia; endemic to Ethiopian Plateau between 800-3300 m (Van der Straeten and Dieterlen, 1983; Yalden and Largen, 1992; Yalden et al., 1976, 1996).

Conservation: IUCN – Lower Risk (nt) as Myomys albipes .

Discussion: Usually listed as either a species of Myomys (G. M. Allen, 1939), Myomyscus (Davis, 1965), or Praomys (Yalden et al., 1976, 1996). Morphometric traits related albipes closely to species of Stenocephalemys and what was described as Praomys ruppi (Van der Straeten and Dieterlen, 1983) . Furthermore, qualitative external, cranial (see Rupp, 1980: Fig. 5), and molar (see illustrations in Misonne, 1969) features of albipes are more similar to species of Stenocephalemys than to other species in Myomys (= Myomyscus). Musser and Carleton (1993) noted that "The phylogenetic significance of this morphologically annectant relationship of M. albipes between other Myomys and Stenocephalemys needs to be assessed by taxonomic revision of both groups." Analyses of chromosomal data (Corti et al., 1995, 1999; Lavrenchenko et al., 1999), allozymic information (Lavrenchenko et al., 1999, 2000), partial 16S rRNA mitochondrial gene sequences (Fadda et al., 2001 a), and complete DNA mitochondrial cytochrome b sequences (Lecompte et al., 2002 b) clustered S. albipes, S. albocaudata, and S. griseicauda in a monophyletic group that excluded species of Praomys and Myomyscus (reported as Myomys) sampled, either P. daltoni or M. brockmani (reported as fumatus). The molecular data also suggested that S. griseicauda is more closely related to S. albipes than to S. albocaudata . To explain differences in size and shape of S. albipes, S. ruppi, S. albocaudata, and S. griseicauda, Fadda and Corti (2000) studied three-dimensional geometric morphometrics of these species, contrasted them with Myomyscus brockmani (reported as fumatus), and demonstrated a positive correlation between altitude and size and shape of skull. Shape differences clustered S. albipes and M. brockmani in a separate group from S. albocaudata and S. griseicauda, which is discordant with the monophyly indicated by chromosomal and molecular data. Fadda and Corti suggested that the strong correlation with altitude and associated environmental changes may be the causal factor for the shape changes. Both S. albocaudata and S. griseicauda inhabit treeless Afro-alpine moorland. Rodents with extremely narrow interorbits, expansive zygomatic arches, and other shape changes in the orbital region allowing a more dorsal position of eyes (stenocephaly) are adapted to survive in open country where they can scan the sky more efficiently for raptors, their primary predators (F. Petter, 1972 d). The cranial similarity between S. albocaudata and S. griseicauda may reflect adaptations to similar habitats rather than phylogenetic relationship. The Myomyscus like cranium of S. albipes is probably a convergent adaptation to forested habitats. The distribution of S. albipes in relation to forest blocks documented by Bekele and Corti (1997:287): "The species prefers the dense forests that are progressively shrinking, so perhaps it can be used as a reliable indicator of forest block reduction on an historical basis."

The holotype of ankoberensis (which we examined) did not fit comfortably in any principal component cluster of holotypes associated with Praomys, Mastomys, Hylomyscus, Myomys, and Myomyscus reported by Van der Straeten and Robbins (1997) because it is an example of S. albipes, which was not included in their analysis. The two Sudanese specimens reported by Setzer (1956) as P. albipes fuscirostris are not albipes but may be associated with Mastomys as either a species or synonym (see account of Mastomys erythroleucus). Pertinent reports cover allozyme variation within geographic samples of S. albipes (Milishnikov et al., 1992), postnatal development and reproduction in captive-bred S. albipes (Bekele, 1995), and distribution in the isolated Harenna Forest of S Ethiopia (Lavrenchenko, 2000).