Common Mylomys

discussion

REMARKS The MNHN-ZM-MO- 1998 - 1013 specimen was karyotyped and its chromosome formula is 2 N = 42, NF = 52 (Gautun et al. 1986) like other representatives of Côte d’Ivoire (Matthey 1970). Morphologically this specimen agrees well with the type specimen but it corresponds to a juvenile individual (Table 7). The pelage is dorsally bicolored (speckled) with a brown general dominant coloration and the bicolored tail is dark above and light below. Contrary to Arvicanthis Lesson, 1842 it has three digits on the hindfoot and four on the forefoot, as well as a white belly. The juvenile Nimba specimen was in alcohol and is poorly preserved. The skull is robust, the rostrum wide with a sharp occipital, there is a long and wide infraorbital foramen. The molars are large and characterised by a selenedont pattern of the cusps (UTR: 8 mm; Upper M 1 / Width: 1,7 mm). The cusps are high and are not fused in laminae. This is also visible on much worn molars of other specimens of the species. The central cusps are high and prominent (t 2, t 5 et t 8) in the upper molars.

Annotated checklist of rodents from a biodiversity hotspot, Mount Nimba (West Africa)

discussion

Discussion: Hatt (1940 a) noted that the cotypes of dybowskii are examples of Mylomys, not Pelomys under which the name had been listed (Ellerman, 1941), and selected a lectotype. The identity was verified by F. Petter (1962 b), who also thought there were two species in the genus, M. dybowskii and the West African M. lowei, named by Hayman (1935) as a subspecies of M. cuninghamei. Rosevear (1969) followed F. Petter in recognizing M. lowei and in turn was followed by Grubb et al. (1998). Hayman (1935: 934), however, regarded all forms to be part of a single species: " In considering what value to place on this Ashanti form [lowei] it has seemed best to regard all the known Mylomys as a subspecies of the original cuninghamei Thos. From that small and rather dark form, through the middle-sized lutescens and christyi to the large brightly-coloured races roosevelti, alberti, and the present form, the differences lie chiefly in comparative size and intensity of colouring. In my opinion the characters of lowei are not sufficient to justify full specific differentiation. " Significance of geographic variation in chromatic and morphological traits has yet to be assessed by critical systema

Order Rodentia - Family Muridae

distribution

Distribution: Guinea (Mt Nimba), Côte d’Ivoire, Ghana (Grubb et al., 1998), S Cameroon, Republic of Congo, Central African Republic, W, N and E Dem. Rep. Congo, Rwanda, Tanzania (Swynnerton and Hayman, 1951), Kenya (Hollister, 1919), Uganda (Delany, 1975), and S Sudan (Setzer, 1958); abstracted from Rosevear (1969), Misonne (1974), many faunal reports, and specimens examined in AMNH, BMNH, FMNH, and USNM.

Order Rodentia - Family Muridae

discussion

COMMENTS: Hatt (1940 a) noted that the cotypes of dybowskii are examples of Mylomys and not Pelomys, under which the name had been listed (Ellerman, 1941), and selected a lectotype. The identity was verified by F. Petter (1962 b). Significance of geographic variation in chromatic and morphological traits has yet to be assessed by critical systematic revision; whether the genus is monotypic or contains more than one species is unresolved. Chromosomal data for sample from Central African Republic reported by Matthey (1970), and those from Mt Nimba (Guinea) provided by Gautun et al. (1986). The taxon rex, represented only by the holotype, a skin without skull from Kaffa in C Ethiopia, was described by Thomas (1906 a) as a species of Arvicanthis, but later " provisionally considered as a giant member of Desmomys " (Thomas, 1916 a: 68). Dieterlen (1974) challenged the validity of rex, but Yalden et al. (1976) pointed out the features distinguishing the holotype from samples of D. harringtoni, and treated rex as another distinctive species endemic to Ethiopia. Our study of the holotype skin reveals it to be a large and probably old adult of Mylomys that is not as brightly pigmented as mo

Order Rodentia - Family Muridae