Otomys yaldeni, 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 : 52-53

publication ID	https://doi.org/ 10.11646/zootaxa.3024.1.1
persistent identifier	https://treatment.plazi.org/id/3C3587DE-FF9F-4562-7DCC-FE8A0FDA9466
treatment provided by	Felipe
scientific name	Otomys yaldeni
status	sp. nov.

Treatment

Otomys yaldeni View in CoL new species

Figs. 2b View FIGURE 2 , 5 View FIGURE 5 , 6 View FIGURE 6 , 17 View FIGURE 17 ; Table 9

Yalden’s Vei Rat

Otomys sp. A : Lavrenchenko et al. 1997: 222.

Otomys typus View in CoL A: Aniskin et al. 1998: 230.

Holotype. ZMMU 162594 View Materials ; adult male, dry skin and skull, collector’s number 132; collected by L.A. Lavrenchenko, 17 February 1995.

Type locality. Ethiopia, Bale Mountains , vicinity of Dinsho, 3170 m; 07°06'N, 39°47'E (interpolated from topographic map) GoogleMaps .

Diagnosis. The smallest representative of the Otomys typus complex (excluding O. jacksoni on Mt Elgon). Similar to O. simiensis , but considerably smaller in external and craniodental size, possessing a wider interorbital region, more pronounced supraorbital ridges, relatively smaller rostral region (clearly shortened nasal bones), more rounded and deeper braincase ( Fig. 17 View FIGURE 17 ), and distinct karyotype (2N=56, NF=56, NFa=54).

Paratypes. BMNH 76.114 ( Ethiopia, 70 km NW Kebre Mengist , 2650 m; 06°23'N, 38°35'E; adult male, dry skin and skull, collector’s number 121; collected by D.W. Yalden, P.A. Morris & M.J. Largen, 13 April 1975) GoogleMaps ; BMNH 76.115 ( Ethiopia, Bale Mountains , 17 km SE of Goba, 3800 m; 06°53'N, 40°03'E; adult female, dry skin and skull, collector’s number 201; collected by D.W. Yalden, P.A. Morris & M.J. Largen, 19 April 1975) GoogleMaps ; BMNH 76.116 ( Ethiopia, Bale Mountains , 10 km SE of Goba, 3300 m; 06°57'N, 40°03'E; adult female, dry skin and skull, collector’s number 175; collected by D.W. Yalden, P.A. Morris & M.J. Largen, 18 April 1975) GoogleMaps .

Description. A small-sized Otomys with a relatively short tail. The dorsal pelage is drab brown, the hairs are greyish at base and yellow-rufous in distal part. Among the guard hairs (11–12 mm), there are longer bristles (20 mm) that produce the effect of double-layered fur. Ventral pelage is pale grey, individual hairs grey at the base and tipped with pale whitish. The ears are blackish, their inner surface covered with short rufous hairs. The dorsal surface of the forefeet and hind feet is dark grey; the claws are grey. The tail is relatively short (49.9% of HB), with blackish caudal hairs on the upper surface and nearly white hairs on the lower; however, given its shortness, the bicoloration of the tail does not appear as well defined as in O. simiensis .

The small skull features a relatively wide interorbital region, markedly well-developed supraorbital ridges, very small rostral region with narrow nasals, short anterior palatal foramen, and small tympanic bullae ( Fig. 17 View FIGURE 17 ; Table 9). Anterior face of the lower incisor is scored by two well defined and equally deep grooves. The upper third molar possesses 6 or 7 complete laminae; the lower first molar possesses 4 complete laminae.

Otomys yaldeni averages smaller than all other species formerly obscured under O. typus except for O. jacksoni ( Table 9). However it can be easily distinguished from O. jacksoni on the basis of skull shape. Compared with O. yaldeni , the holotype of O. jacksoni displays a much narrower interorbital region, with weakly developed supraorbital ridges, and does not possess such conspicuously shortened nasal bones ( Fig. 17 View FIGURE 17 ). Otomys yaldeni differs from other Ethiopian Otomys (excluding O. simiensis ) by the lower number of laminae in the upper third molar (6–7 vs. 8–9) and by its double-layered dorsal fur.

The chromosomal set of O. yaldeni consists of 2 n = 56, NF=56, NFa=54, acrocentrics with an acrocentric X and Y ( Fig. 2b View FIGURE 2 ). Allozymic investigation of 18 enzymatic and non-enzymatic proteins (Adh, Alb, Gdc, Hbb, Got-1, Got-2, G-6-pd, Dia-1, Dia-2, Idh-1, Ldh-A, Ldh-B, Mdh-1, Mdh-2, Me-1, Sdh, Sod-1, Sod-2) revealed that non-overlapping allele spectra in four loci (G-6-pd, Dia-2, Alb and Got-2) discriminated O. yaldeni and O. helleri , which are partially sympatric in the Bale Mountains ( Lavrenchenko et al. 1997).

Distribution. Documented from the northern (Dinsho and Goba areas) and south-western (70 km NW Kebre Mengist) slopes of the Bale Massif, southeastern Ethiopia.

Ecology. All known specimens of O. yaldeni were collected in mosaic habitats of grassland and forest between 2650 and 3800 m. The holotype was captured at the edge of typical undifferentiated afromontane forest with Junipe- rus procera, Hypericum revolutum , Maytenus arbutifolia , Rosa abyssinica and open grassy patches with Euphorbia dumalis , Festuca abyssinica , Koeleria capensis , Poa schimperana , Exotheca abyssinica . The paratypes were captured in afromontane forest with Hagenia abyssinica and bamboo patches with Arundinaria alpine (BMNH 76.114), in moorland with Erica trimera and Helichrysum citrispinum (BMNH 76.115), in open woodland with Hypericum revolutum and Helichrysum citrispinum (BMNH 76.116).

Etymology. The species name acknowledges the substantial contributions of Derek W. Yalden to our understanding of Ethiopia’s indigenous mammals. His museum and field efforts, published over some 20 years in faunal reports and taxonomic catalogues (e.g., Yalden et al. 1976, 1996), meaningfully advanced specimen-based knowledge of species and their distributions, thereby underscoring the exceptional endemism that characterizes the mammal fauna of the Ethiopian highlands. Otomys yaldeni appropriately represents another of those endemics. The species name combines the surname Yalden and genitive singular case-ending “i” indicative of masculine gender.