Soriculus nivatus Chen & Jiang, 2024

Chen, Zhongzheng, Pei, Xiaoxin, Hu, Jiangxiao, Song, Wenyu, Khanal, Laxman, Li, Quan & Jiang, Xuelong, 2024, Multilocus phylogeny and morphological analyses illuminate overlooked diversity of Soriculus (Mammalia: Eulipotyphla: Soricidae), with descriptions of two new endemic species from the eastern Himalayas, Zoological Journal of the Linnean Society 201 (2), pp. 534-548 : 544-545

Soriculus nivatus Chen & Jiang , sp. nov.

[ Fig. 6 ; Table 1 ; Supporting Information, Fig. S2 (= Soriculus sp. 1 )] ZooBank registration: LSIDurn:lsid:zoobank. org:act: BF2CE06E-E666-4247-8DC7-7A30433EFA92.

Suggested common name: Snow Mountain large-clawed shrew; OiƜkmẽē.

Holotype: MT1904951, adult female, collected on 2 June 2019 by Zhechang Pu. Dried skin, cleaned skull, and muscle tissues are deposited in the KIZ.

Type locality: K81 of Motuo Highway (29.742° N, 95.683° E, 3619 m a.s.l.), Damu Town , Medog, south-east Tibet, China.

Paratypes: Five specimens ( MT 201904489 , -573, -574, -932, -1022) collected from Medog in April 2019 at the elevations from 3000 m to 3600 m a.s.l.

Etymology: The specific Latin name nivatus was derived from the Latin nivātus , means cool with snow. It refers to the habitat of the new species.

Diagnosis: Size similar to S. nigrescens , but rather larger than S.minor . Tail averages 63% of the head and body length (mostly greater than 50 mm), relatively longer than those of S.nigrescens and S.minor .The maxillary region is narrower than S. nigrescens . The teeth are slender and the most delicate in the genus; maximum width across the upper second molars (M 2 M 2) less than S. nigrescens . Pigmentation of the teeth much heavier than those in S. minor .

Description: Soriculus nivatus is a medium sized shrew (W = 11.7 ± 1.7 g, HB = 83 ± 4 mm; Table 1 ) in the genus. The dorsal pelage is uniformly dark brown ( Fig. 5 ) but slightly browner than S. nigrescens . The dorsal hairs are about 5 mm long in summer, and 8 mm in winter. Tail is ambiguously bicolored, dark brown above and pale below. The tail averages 63% of the head and body length, and 19 of 23 specimens examined have a tail length ≥ 50 mm. As with the genus, the foreclaws are enlarged, which are larger than the hind claws. The back of the hands and feet are covered by light brown to black hairs.

The skull is robust and bony, much heavier than in Chodsigoa and Episoriculus ( Fig. 6 ). Relative to other species of Soriculus , the rostrum and maxillary of S. nivatus are relatively narrower; the interorbital region is broad with slightly tapering edges. Braincase is domed but low, and the posterior of the skull is rounded. The lambdoidal crest is modestly developed, and the sagittal crest is indistinct. The basioccipital and basisphenoid are fused and narrowed markedly in the middle region, forming a thread-like structure. The coronoid process is robust with a spatulate tip, rising straight upwards. The condyloid process is heavy, forming an angle at roughly 45° with the coronoid process. The angular process is long, straight, and very thin.

The teeth of S. nivatus are slender and more delicate than in other species in the genus ( Fig. 6 ). The dental formula of the new species is the same as for the genus is: I 3/2, C1/0, P 2/1, M 3/3 (×2) = 30. The first upper incisor bifid; the principal (anterior) cusp moderately long, falciform, and the apex pointing straight downwards; the posterior cusp is small and lower than the following U 1. Four upper unicuspids (U 1 –U 4) are present; U 2 is largest in size, U 1 is slightly smaller, U 3 is about half as high as U 2, and U 4 is minute. P 4 is deeply excavated in the posterior borders. M 1 and M 2 are similar in size, whereas M 3 is reduced. The low incisor (I 1) is long, with a low cusp. The lower unicuspid (U 1) is small and procumbent between I 1 and P 4. M 3 is reduced. The tips of the cusps of all teeth are pigmented with orange.

Comparison: The new species is morphologically similar to S. nigrescens but is distinguishable from the latter by many characters. Most individuals of S. nigrescens (W = 17.6 ± 2.5 g, range 12.9–20.7g, with only one of 11 specimens weighing less than 15.5 g) are much heavier than S. nivatus (W = 11.7 ± 1.7 g, range 9.6–15.3 g), and S. nivatus appears much smaller than S. nigrescens in the field. The tail of S. nivatus is relatively longer (TL/HB = 63%) than S. nigrescens (TL/HB = 52%); most individuals of S. nivatus (19 of 23) have a tail length more than 50 mm, whereas most individuals of S. nigrescens (nine of 11) have a tail length less than 50 mm. In the skull, rostrum of S. nivatus is relatively narrower than S. nigrescens , and the range of measurements of MB (6.3–6.8 mm in S. nivatus vs. 6.9–7.4 mm in S. nigrescens ), M 2 M 2 (6.0– 6.6 mm in S. nivatus vs. 6.9–7.1 mm in S. nigrescens ), and DIF (3.6–3.9 mm in S. nivatus vs. 4.2–4.5 mm in S. nigrescens ) between the two species do not overlap ( Table 1 ). The maxillary region of S. nivatus is distinctly narrower than that of S. nigrescens . The teeth of S. nivatus are much more slender and delicate than those of S. nigrescens . The first upper incisor of S. nigrescens is slightly smaller and the apex is straight downwards, whereas the apex of the first upper incisor of S. nivatus is slightly curved upwards, forming a hook at the tip. The height of the coronoid valley of S. nivatus ( HCV = 3.2 ± 0.1 mm, range = 3.1–3.5 mm) is smaller than that of S. nigrescens ( HCV = 3.7 ± 0.1 mm, range = 3.5–3.8 mm).

Soriculus nivatus is easily distinguished from S. minor by its larger size, and the two species usually show little or no overlap in all measurements ( Table 1 ). It can further be distinguished from S. minor by its proportionately longer tail (TL/HB = 63% of S. nivatus ; TL/HB = 52% of S. minor ) and the more heavily pigmented teeth.

Distribution: Soriculus nivatus is currently known from 2560 m to 4200 m in the eastern Himalayas in Linzhi, Tibet, China. It is sympatric with S. nigrescens in Milin County at an elevation of 3000 m a.s.l., near the Yarlung Tsangpo River.

Figures

Figure 2. Results of the principal components (A) and discriminant function analysis (B) analysis of Soriculus based on the 18 log10- transformed craniomandibular variables.

Figure 5. Estimated divergence times of the genus Soriculus using BEAST.

Figure 6. Dorsal, ventral, and lateral views of the skull and lateral view of the mandible of (A) S. nigrescens (MT201904155), (B) S. nivatus (holotype, MT1904951), (C) S. medogensis (holotype, MT201811181), and (D) S. minor (TC-H-KIZ 2345).