Soriculus medogensis 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 : 545

Soriculus medogensis Chen & Jiang , sp. nov.

[ Fig. 6 ; Table 1 ; Supporting Information, Fig. S2 (= Soriculus sp. 2 )] ZooBank registration: LSIDurn:lsid:zoobank. org:act: E9425BFD-BD17-41FE-8570-D3220534DCE0.

Suggested common name: Medog large-clawed shrew, DZükm ẽē.

Holotype: MT201811181, adult female, collected on 29 October 2018 by Jing Luo. Dried skin, cleaned skull, and muscle tissue are deposited in the KIZ.

Type locality: Damu Town , Medog, southeastern Tibet, China (29.702° N, 95.526° E, 2560 m a.s.l.).

Paratypes: Six specimens ( MT 201811195 , -221, -230, -260, -276, -285) collected from the type locality at Medog on 29–31 October 2018 at elevations from 2560 m to 2620 m a.s.l.

Etymology: The specific Latin name medogensis named for Medog, with the Latin adjectival suffix -ensis means ‘belonging to’.

Diagnosis: Size similar to S. nivatus and S. nigrescens , and much larger than S. minor ; tail averages 60% of the head and body length (mostly ≥ 50 mm), similar to S. nivatus , but relatively longer than that of S. nigrescens and S. minor . The teeth are more robust and the maximum width across the upper second molars (M 2 M 2) is greater than in S. nivatus . The sagittal crest is much more pronounced than in other Soriculus species. The ramus region is the broadest and the coronoid process is the highest in the genus ( HCP > 6.6 mm; HCP <6.1 mm in other species). Pigmentation of the teeth is heavier than in S. minor .

Description: External morphology and size similar to S. nivatus ( Table 1 ), but the pelage is slightly darker (Supporting Information, Fig. S2 ). The dorsal pelage is dense and soft, about 8 mm long in winter (we have not collected this species in summer, but we suspect that its dorsal pelage should be shorter in summer, similar to S. nivatus ). The tail is not sharply bicolored. In six of the seven specimens examined, the tail length is more than 50 mm, averaging 60% of the head and body length. The foreclaws are enlarged, similar to those of other Soriculus species.

The skull is robust, bony, and more angular than that of S. nivatus ( Fig. 6 ). Braincase is low and relatively flattened, and the posterior of the skull is angular rather than rounded. The lambdoidal and sagittal crest are well developed and pronounced. The basioccipital and basisphenoid are fused and underdeveloped, contracted into a line in the central region. The mandible is more developed than in other species in the genus. The coronoid process is spatula shaped, rising straight upwards. Compared with the other Soriculus , S. nivatus has a relatively larger ramus region, and a higher and broader coronoid process.

The dental formula is the same as for other members of the genus Soriculus : I 3/2, C 1/0, P 2/1, M 3/3 (×2) = 30. The teeth are more robust than those of S. nivatus ( Fig. 6 ). The first upper incisor is bifid; the principal (anterior) cusp is short, dagger like, and extends anteriorly; the posterior cusp is lower than U 1. Four upper unicuspid teeth are present; U 2 is slightly larger than U 1, U 3 is about half the height of U 2; U 4 is minute but larger than that in S. nivatus . The shape of P 4 and molars are similar to those in S. nivatus , but slightly larger. M 1 and M 2 are similar, whereas M 3 is reduced. The lower incisor (I 1) is long with only a low cusp. The lower unicuspid (U 1) and P 4 are crowded. M 1 slightly larger than M 2, and M 3 is reduced. The tips of the teeth are pigmented only lightly with orange.

Comparison: Soriculus medogensis can be distinguished from other Soriculus species by many unique characters: the posterior of the braincase is angular (rounded in other species); the sagittal crest is well developed and pronounced (indistinct in other species); a more developed mandible, with a larger ramus region and the highest coronoid process of all members of the genus; and a shorter and anteriorly leaning first upper incisor.

It can further be distinguished from its sister species S. nivatus by its more robust and lighter pigmented teeth. The measurements of MB, M 2 M 2, HCP, HCV, HAC, and PPD of S. medogensis are greater than those in S. nivatus , with no overlap.

Compared with S. nigrescens , the tail of S. medogensis is proportionately longer (TL/HB = 60% in S. medogensis vs. TL/HB = 52% in S. nigrescens ). In six of the seven specimens examined, tail length is ≥ 50 mm, whereas nine of 11 S. nigrescens specimens have a tail length ≤ 50 mm. Most individuals of S. nigrescens are much heavier (10 of 11 ≥ 15.5 g) than S. medogensis (W = 13.3 ± 0.7 g, range 12.0– 14.1 g). Rostrum of S. medogensis is relatively narrower than in S. nigrescens . Soriculus medogensis has greater measurements of UTL, LTR, and HCP, but smaller DIF than S. nigrescens .

Soriculus medogensis can be further distinguished from S. minor by its much larger size and relatively longer tail. In addition, the teeth in S. medogensis are also more heavily pigmented than those in S. nigrescens .

Distribution: Soriculus medogensis is known only from the type locality in Medog, Tibet, China, at elevations from 2100 m to 2830 m a.s.l., and it is sympatric with S. nivatus .

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 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).