Otomys cheesmani, Taylor & Lavrenchenko & Carleton & Verheyen & Bennett & Oosthuizen & Maree, 2011

Taylor, Peter J., Lavrenchenko, Leonid A., Carleton, Michael D., Verheyen, Erik, Bennett, Nigel C., Oosthuizen, Carel J. & Maree, Sarita, 2011, Specific limits and emerging diversity patterns in East African populations of laminate-toothed rats, genus Otomys (Muridae: Murinae: Otomyini): Revision of the Otomys typus complex 3024, Zootaxa 3024 (1), pp. 1-66 : 43-44

publication ID	https://doi.org/ 10.11646/zootaxa.3024.1.1
DOI	https://doi.org/10.5281/zenodo.5285483
persistent identifier	https://treatment.plazi.org/id/3C3587DE-FF86-457D-7DCC-F9910B9B93B1
treatment provided by	Felipe
scientific name	Otomys cheesmani
status	sp. nov.

Treatment

Otomys cheesmani View in CoL new species

Figs 5 View FIGURE 5 , 6 View FIGURE 6 , 17 View FIGURE 17 ; Table 9

Cheesman’s Vlei Rat

Holotype. BMNH 1937.2.24.84; adult male, dry skin and skull, collector’s number 7400; collected by R. E. Cheesman, 20 October 1937.

Type locality. Ethiopia, vicinity of Dangila , 66 km S Lake Tana, 2100 m ; 11°16’N, 36°51’E.

Diagnosis. The largest representative of the Otomys typus species complex, differing from all other members by its distinctly larger and more robust skull with short and broad nasal bones, broad, angular and thickened zygomatic arches, very well developed supraorbital and parietal ridges and relatively very narrow interorbital region (referred to “Sp. C” above; see Figs 5 View FIGURE 5 , 6 View FIGURE 6 , 17 View FIGURE 17 and Tables 7, 9).

Paratypes. BMNH 28.1 .11.117 (adult female, dry skin and skull, collector’s number 6040) , BMNH 28.1 .11.174 (adult male; dry skin and skull, collector’s number 6078) , BMNH 28.1 .11.175 (subadult male, dry skin and skull) , BMNH 28.1 .11.176 (subadult male, dry skin and skull, collector’s number 6366) , BMNH 28.1 .11.177 (adult female; dry skin and skull, collector’s number 6040) , BMNH 28.1 .11.178 (adult female, dry skin and skull, collector’s number 6070) , BMNH 28.1 .11.179 (adult female, dry skin and skull, collector’s number 6165) , BMNH 1937.2 .24.82 (adult male, dry skin and skull, collector’s number 7383) , BMNH 1937.2 .24.83 (adult male, dry skin and skull, collector’s number 7387) , BMNH 1937.2 .24.85 (adult male, dry skin and skull, collector’s number 7404) , BMNH 1937.2 .24.86 (adult female, dry skin and skull)—all 11 from the type locality, collected by R.E. Cheesman between 1926 and 1937 ; BMNH 70.657 ( Ethiopia, Gojam , Debra Marcos, 2500 m; 10°20’N, 37°46’E; collected by Great Abbai Expedition, 19 August 1968) GoogleMaps .

Description. The dorsal pelage of O. cheesmani is bright brown with a reddish shade. Ventral pelage is pale yellowish-grey, the individual hairs yellow tipped and grey at the base. The ears are blackish, their inner surface covered with short rufous hairs. The dorsal surface of the forefeet and hindfeet is dark grey; the claws are grey. The tail is relatively short (49.3% of HB). The caudal hairs are blackish on the upper surface and pale yellowish on the lower surface; however, the tail does not appear distinctly bicoloured.

The robust skull of O. cheesmani ( Fig. 17 View FIGURE 17 ) is reflected in the large means recorded for most cranial dimensions, which exceed those of all other representatives of the O. typus complex except for interorbital width ( Table 9). Although the observed ranges of certain external and cranial variables overlap, four cranial variables do not overlap in size: GLS (43.3–48.2 mm versus 34.3–43.3 mm); MXTL (11.0–12.0 mm versus 8.1–10.5 mm); NAW (8.0–9.0 mm versus 5.8–8.0 mm); PL (23.6–26.2 mm versus 16.7–23.6 mm) ( Table 9). The anterior face of the lower incisor has two well defined and equally deep grooves. The upper third molar has 8 or 9 complete laminae (9 in the holotype) and the lower first molar 4 complete laminae.

Distribution. Known only from two localities in northwestern Ethiopia, 2100–2500 m (see above).

Ecology. The type locality currently represents a true agricultural landscape, presumably much transformed from the time when Cheesman collected the series. The holotype and paratypes of O. cheesmani were supposedly collected in an intrazonal wetland habitat. The specimen from Debra Marcos (BMNH 70.657) was captured in low Acacia scrub. Otomys cheesmani occupies lower elevations (2100–2500 m) than other Ethiopian Otomys (excluding the rainforest dweller O. fortior ). Nevertheless, habitat requirements of this new species remain unclear.

Etymology. We selected the specific epithet to recognize Robert E. Cheesman (1878–1962), who collected the holotype and topotypic series of this distinctive species of Otomys . Cheesman was a British military and diplomatic officer in the Middle East, Arabian Peninsula, and nearby Africa, and like many other professionals of this era, he developed broad interests in the geography and natural history of the lands where he worked. During his service as Consul in North-West Abyssinia, Cheesman not only explored the source of the Blue Nile and surveyed its course from Lake Tana to the Sudan border (Lake Tana and the Blue Nile: An Abyssinian Quest by R. E. Cheesman, 1936; Macmillan: London, 400 pp.), but also found time to collect bird and mammal specimens for the British Museum. The species name combines the surname Cheesman and genitive singular case-ending “i” indicative of masculine gender.