Niviventer fengi, Ge & Feijó & Abramov & Wen & Liu & Cheng & Xia & Lu & Yang, 2021

Ge, Deyan, Feijó, Anderson, Abramov, Alexei V., Wen, Zhixin, Liu, Zhengjia, Cheng, Jilong, Xia, Lin, Lu, Liang & Yang, Qisen, 2021, Molecular phylogeny and morphological diversity of the Niviventer fulvescens species complex with emphasis on species from China, Zoological Journal of the Linnean Society 191 : -

NIVIVENTER FENGI GE, FEIJÓ AND YANG SP. NOV.

( FIGS 5A, 6)

Jilong soft-furred niviventer, Tibetan white-bellied rat. lsid: zoobank.org:pub: A0C63287-87B3-42E0-BC0E- CACDE62A8137

Holotype: IOZCASJL17111, an adult male preserved as dry skin, skull and frozen tissue deposited at the Institute of Zoology, Chinese Academy of Sciences , Beijing. The holotype was collected by Drs Zhixin Wen and Yuanbao Du on 16 October 2017. The Cytb, COI, D-loop and Rbp3 sequences of the holotype are archived in GenBank with accession numbers MN 814475 – MN 814491 , MN 814581 – MN 814584 , MN 814634 – MN 814637 and MN 814696 – MN 814698 , respectively. EMs are as follows: BM = 47 g, HBL = 122, TL = 145, HFL = 25 and EL = 21. CMs are as follows: TLC = 31.72, NL = 10.44, GWS = 5.49, SDO = 5.14, ZB = 14.4, GMB = 12.79, PL = 15.34, IFL = 5.36, WIF = 2.23, GPB = 6.39, LTB = 4.66, ULMM = 5.25, ULMD = 7.8, ML = 15.46, LLMM = 5.25 and LLMD = 4.23.

BM, EMs and CMs of molecular vouchers and museum specimens: BM = 53.67 ± 14.03 (41–80, N = 15). EMs of 15 adult specimens: HBL = 126.47 ± 14.03, TL = 146.07 ± 14.19, HFL = 24.93 ± 1.49 and EL = 19.53 ± 1.46. CMs from nine intact adult specimens: TLC = 32.44 ± 1.98, NL = 11.49 ± 1.24, GWS = 5.36 ± 0.49, SDO = 5.17 ± 0.28, ZB = 14.84 ± 0.60, GMB = 12.79 ± 0.45 , PL = 16.05 ± 0.92, IFL = 5.77 ± 0.67, WIF = 2.48 ± 0.26, GPB = 6.42 ± 0.25, LTB = 5.32 ± 0.52, ULMM = 5.33 ± 0.22, ULMD = 8.30 ± 0.81, ML = 15.28 ± 0.52, LLMM = 5.21 ± 0.21 and LLMD = 4.28 ± 0.46.

Type locality: Jilong Valley, Jilong County, Shigatse, Tibet, China (N 28.48493, E 85.22434; 3295 m). This region is characterized by alpine coniferous forest dominated by cypresses and an understorey of Cremanthodium sp. , Himalaiella nivea (DC.) Raab-Straube (both Asteraceae ) and Rhodiola rosea L. ( Crassulaceae ).

Paratype: IOZCASJL17059 ( Fig. 5A 3–4), an adult male preserved as dry skin, skull and frozen tissue collected on 15 October 2017 at 2900 m in Jilong Valley , Tibet, China (N 28.48099, E 85.22477; 2900 m). BM = 78 g, HBL = 146, TL = 180, HFL = 26, and EL = 20. CMs are as follows: TLC = 34.68, NL = 13.82, GWS = 5.77, SDO = 5.08, ZB = 15.97, GMB = 13.16, PL = 17.25, IFL = 6.87, WIF = 2.99, GPB = 6.57, LTB = 5.91, ULMM = 5.49, ULMD = 9.63, ML = 16.01, LLMM = 5.27 and LLMD = 4.44.

Additional specimens: Skins of IOZCASJL17051, IOZCASJL17201 and IOZCASJL17210 collected together with the type specimens. Skulls of IOZCASJL17062, IOZCASJL17071, IOZCASJL17075, IOZCASJL17079, IOZCASJL17107, IOZCASJL17201 and IOZCASJL17210 are intact and preserved with the skin specimens.

Sequenced molecular voucher specimens: Fifteen males, including IOZCASJL17051, IOZCASJL17059, IOZCASJL17062, IOZCASJL17063, IOZCASJL17070, IOZCASJL17071, IOZCASJL17075, IOZCASJL17076, IOZCASJL17078, IOZCASJL17079, IOZCASJL17082, IOZCASJL 17202, IOZCASJL 17111 and IOZCASJL17201; one female, IOZCASJL17107; and one specimen of unknown sex (badly damaged), IOZCASJL17100, which was collected at the same locality as the holotype and paratypes by Drs Zhixin Wen and Yuanbao Du .

Description: Smallest species in the NFSC, with dense and soft fur and without spines. HBL ranges from 110 to 140 mm and TL from approximately 118% to 127% of the HBL. Dorsal coloration brownish and finely sprinkled with yellowish. Individual dorsal hairs are mostly dark grey with yellowish tips. Guard hairs long and scattered on the dorsum, mainly in the posterior region; some show a bicolour pattern: black in the posterior half and white in the anterior half. Ventral colour uniformly white, contrasting sharply with the upper parts. Ears short, black and without evident hairs. Mystacial vibrissae long, with some extending beyond the posterior margin of the ear, black in the basal portion and paler distally. Forefeet covered with short, whitish hairs. Feet with a marked grey brownish patch in the medial portion of the metatarsal region, and the digits with whitish hairs. Tail hairy, with hairs spanning up to two scales, and at its tip forming a short, usually black tuft of approximately 15 mm. Tail bicoloured, with the upper part darker and covered by black hairs and the venter part pale and covered by white hairs. Tail scales arranged in an annular pattern approximately 0.8 mm in length. Skull with a relatively short rostrum and rounded braincase. Its general dorsal profile nearly flat, particularly in the frontal region, where there is a shallow medial depression. Dorsolateral margins of the interorbital well defined by supraorbital ridges that extend to the lateral braincase. Zygomatic arches slightly expanded laterally, with their maxillary root lying anterior to the tooth row. Incisive foramina narrow and extending to the anterior margin of the tooth row. Intraparietal wide and short in the anterior-posterior plane. Palatal short and extending slightly beyond the posterior margin of the third molar. Auditory bullae small.

Diagnosis: Niviventer fengi is easily distinguished from all other species of the NFSC by its overall darker colour, the absence of spines, a brownish patch in the metatarsal region of the hindfoot and its hairier tail ( Fig. 6A 1, A 2). All other species of the NFSC have a generally bright ochraceous or reddish brown colour and spines on the dorsum ( Fig. 6A 1; Musser, 1973, 1981). Niviventer fengi is also differentiated from its conspecifics by its smaller size, especially the proportionally smaller size of the tail, hindfoot, total length of the skull, length of maxillary diastema, interorbital breadth, PL and ML (see Tables 2, 3; Fig. 4).

Distribution: This species is known from Jilong Valley, Rikaze, Tibet Province, China, near the Nepalese border.

Etymology: We named this new species in honour of Prof. Zuojian Feng from IOZCAS for the great contribution to the study of mammals in China.

Comments: The general morphology of N. fengi is similar to that of N. excelsior , including its soft fur, but this species is significantly smaller than N. excelsior (BM = 67 ± 13.64, HBL = 133.14 ± 9.788, TL = 205.57 ± 12.98, HFL = 30.71 ± 2.05 and EL = 22.71 ± 0.95), which is endemic to the southwestern mountainous area of China ( Ge et al., 2017).

Sympatric species: Niviventer fengi is sympatric with N. fulvescens and N. eha , but they are distinct in external morphology.