Alticola yarlungia Tang, Qiu, Peng & Liu, 2025

Tang, Ming Kun, Qiu, Hong, Peng, Bu Qing, Liao, Rui, Murphy, Robert W., Wang, Xu Ming, Pan, Xuan, Wang, Xin & Liu, Shao Ying, 2025, A new species of Alticola (Mammalia, Rodentia, Arvicolinae) from southern Tibet, China, Zoosystematics and Evolution 101 (4), pp. 2387-2403 : 2387-2403

Alticola yarlungia Tang, Qiu, Peng & Liu, 2025 sp. nov.

Holotype.

Adult male, SAF 230697 , collected by Rui Liao et al. on 27 August 2023 (field number XZ 23458, summer pelage) using a snap trap. Collected in shrub habitat near Naijiaxiongqu (stream), Xibaxiaqu River, a right tributary of Yarlung Zangbo River . Specimen prepared as a skin with cleaned skull, baculum, and muscle tissue deposited at the Sichuan Academy of Forestry.

Measurements of holotype.

Weight 29 g; HBL 104 mm; TL 24 mm; HFL 18 mm; EL 12 mm; SGL 24.77 mm; CBL 22.76 mm; ZB 13.35 mm; IOB 3.84 mm; NL 7.49 mm; HB 9.06 mm; M – M 4.81 mm; LMxT 14.44 mm; LUMR 5.12 mm; LLMR 5.29 mm; MGL 17.35 mm; ML 14.52 mm.

Type locality.

San’anqulin Township , Longzi County, Lhoka City, Tibet Autonomous Region, China ( 28.59838°N, 92.92745°E; 4,022 m elev).

Paratypes.

Six specimens ( 3 male, 3 female), skins with skulls, and male specimens with glans penis. Two topotype adult specimens collected on 27 August 2023: SAF 230699 (Field number XZ 23460, male) and SAF 230700 (Field number XZ 23461, female). Two adult specimens collected by Rui Liao et al. from Jindong Township, Lang County on 30 August 2023: SAF 230750 (Field number XZ 23511, male) and SAF 230751 (Field number XZ 23512, female), 28.94895°N, 93.38686°E, 3,228 m elev. One adult specimen collected by Rui Liao et al. from Jindong Township, Lang County on 30 August 2023: SAF 230743 (Field number XZ 23504, male), 28.95136°N, 93.38714°E, 3,238 m elev. One adult specimen collected by Rui Liao and Ning Xing from Jindong Township, Lang County on 20 August 2008: SAF 081053 (Field number GB 828002, female), 28.93505N, 93.39156E, 3,279 m elev. All six paratypes are deposited in the collections of the Sichuan Academy of Forestry.

Measurements of paratypes. Weight 20–40 g; HBL 92–107 mm; TL 23–28 mm; HFL 17–18 mm; EL 14–15 mm; SGL 23.43–26.2 mm; CBL 21.23–24.02 mm; ZB 11.71–14.2 mm; IOB 3.94–4.33 mm; NL 7.05–8.23 mm; HB 8.66–9.62 mm; M – M 5.03–5.26 mm; LMxT 13.83–15.54 mm; LUMR 5.32–5.85 mm; LLMR 5.43–5.77 mm; MGL 16–18.54 mm; ML 13.07–16.33 mm.

Geographic distribution.

The species is known only from Longzi County, Lhoka City, and Lang County, Nyingchi City, Tibet, China.

Etymology.

The specific epithet yarlung is a toponym derived from the Yarlung Zangbo River, the type locality of the new species (Longzi and Lang County), which drains this river basin, with the Latin suffix - ia denoting ‘ pertaining to’ or ‘ from the region of’. The Yarlung Zangbo River is the largest river in Tibet, known for a very high diversity of elevations, habitats and species. We propose the English name “ Yarlung Zangbo Mountain Vole ” and the Chinese name “ 雅鲁藏布高山䶄 (Yǎlǔ Zàngbù Gāoshān Píng) ” for this new species.

Diagnosis.

A medium-sized species of Alticola characterized by the following combination of characters: HBL of adult 92–110 mm and TL comprises nearly one fourth of the HBL. Body back with obvious dark brown tinge, belly dirty white; tail slender and indistinctly bicolored, covered with short hairs that are brownish above and gray white below; shortened upper molar row, M 3 usually with two lingual reentrants, three lingual angles, two labial reentrants and three labial angles, with a shortened posterior lobe typically contacting to the third labial angle; M 3 with three loops, the middle loop being divided into two in approximately half of the specimens. Alticola yarlungia is geographically proximate to A. stoliczkanus and similar in general body coloration and tooth patterns. However, it differs in having a distinctly narrower second labial reentrant on M 3 and a more stable and pronounced second lingual reentrant. The new species is larger than A. stoliczkanus in several measurements, including HBL (102 ± 5.89 mm vs. 91.91 ± 3.91 mm), HFL (17.78 ± 0.67 mm vs. 16.91 ± 0.83 mm), and EL (14.44 ± 1.24 mm vs. 12.82 ± 0.4 mm). The tail is longer and more slender with shorter hairs and a shorter tufted tip ( TL = 25.22 ± 1.79 mm, 24.8 % of HBL; vs. 20.09 ± 1.87 mm, 21.9 % of HBL in A. stoliczkanus ).

Description.

The general pelage color of holotype is brown, with the dorsal fur approximately 9 mm long. Proximal part of back fur black-gray, while distal parts brown. Ventral fur gray-white with a black-gray base, uniform color from throat to belly and anus, with a distinct color boundary between the dorsal and ventral fur. Pelage of paratypes same as that of the holotype. Mystacial vibrissae mostly white, but some are black, with approximately 26 mm on each side. Shortest vibrissa approximately 8 mm, and longest approximately 30 mm. Ears projected slightly above pelage. Pinnal rim entirely brown, with dense brown fur. Tail slender, covered with short hairs that extend for about 7 mm beyond tail-tip, color on top brown, lighter than dorsal fur, underside consistently gray whitish. Hairs on the tip of tail slightly longer. Foot covered with gray-white hairs; claws blackish-gray, with long, stiff hair, thumb vestigial and clawless. Palms with five, soles with six pads, black-brown. Females with two pectoral and two inguinal pairs of mammae (Fig. 5 A ).

Skull small and rounded in dorsal profile, nasal bones broad anteriorly and narrow posteriorly, tapering to appear elongated, and braincase approximately orbicular. Posterior and anterior frontal bones broad but narrow in interorbital region. Interparietal bone antero-posteriorly narrow, subtriangular. Post-orbital squamosal crests slightly weaker. Two ridges behind temporal joint above auditory bulla. Zygomatic arches sturdy. Auditory bullae medium-sized and globular. Posterior palate typical of Arvicolinae ; structure of palate terminates in a square-edged, thin bony shelf, lacking upward-sloping bony bridge connecting median point with inner borders of both lateral pits. Palatine and pterygoid with numerous small foramina. Mandibles sturdy. Upper incisors straight with anterior faces light orange. M 1 with four closed triangles after anterior transverse space, forming three inner and three outer angles. M 2 with three closed triangles after anterior transverse space, forming two inner and three outer angles. M 3 comprises three main loops, forming three outer and three inner angles; the first transverse loop includes a shallow outer reentrant between two outer angles (former slightly exceeding latter) and salient inner angle; the second small loop with second inner angle, back to second outer deep reentrant; the third loop usually an anterior outer angle, middle inner angle and near circular terminal of substantially shortened posterior lobe, sometimes the posterior lobe moderately extending and the middle inner angle becoming weaker or absent. Lower incisors relatively long, and lip-side light orange. M 1 with four staggered triangles anterior to posterior transverse space; anterior space shorter and anomalistic, forming one inner and one outer angle, totally with four inner and four outer angles. M 2 bearing four closed loops and three inner and three outer angles. M 3 possesses three closed loops (sometimes the middle loop divided into two closed loops), forming three inner and three outer angles (Fig. 9 ).

Glans penis generally same size as other congeners (Fig. 7 A ). Four to five outer crater papillae on each side (Fig. 7 A 1, b ), base of proximal baculum semicircular (Fig. 7 A 2, m ), distal, lateral bacula slender (Fig. 7 A 2, a, k ), and lateral bacula with a sharp tip (Fig. 7 A 2, k ). Urethral lappet forked into two long branch forks with deep bifurcation (Fig. 7 A 3 ). Dorsal papillae with a distalis digitation (Fig. 7 A 4 ).

Habitat.

This new species is expected to occur in primary or secondary forest with low cover, shrubs along the bank of valley. Elevation of the collected specimens ranges from 3,228 m to 4,022 m, lower than that of A. stoliczkanus . Nine specimens collected in sunny, riparian habitat near stream. Vegetation of the type locality consists of shrubs, averaging 2.0 m high, with 40 % coverage along with grasses, about 0.3 m high, at 25 % of coverage. Thickness of the humus layer is no more than 5 cm.

Figures

Figure 5. Pelage comparison of Alticola. A. yarlungia sp. nov. (A. Voucher XZ 23458), A. stoliczkanus (B. XZ 16120), A. macrotis (C. XJ 24041), A. albicauda (D. XJ 23002), A. argentatus (E. XJ 21175), A. barakshin (F. SWUN 93141), A. semicanus (G. NMG 22012), and A. strelzowi (H. XJ 21008). Images show dorsal (1), ventral (2), and lateral (3) views.

Figure 7. Comparison of the glans penis and baculum between Alticola yarlungia sp. nov. (A), A. stoliczkanus (B) and A. macrotis (C). Numerals indicate: 1, penis; 2, midventral cut view of glans; 3, urethral papilla; 4, dorsal papilla. Lowercase letters indicate: a, distal baculum; b, outer crater papillae; c, outer crater; d, urethral papilla; e, ventral groove; f, glans; g, prepuce; h, body of penis; i, tip of distal baculum; j, site of dorsal papilla; k, lateral baculum; l, proximal baculum; m, base of proximal baculum.

Figure 9. Craniodental morphology of the holotype of Alticola yarlungia sp. nov (voucher number: XZ 23458). A 1. Dorsal view; A 2. Ventral view; A 3. Lateral view; A 4, A 5. Mandible; B 1. Right upper molar row (lingual side on right); B 2. Right lower molar row (lingual side on left).