Eothenomys meiguensis, 2019

EOTHENOMYS MEIGUENSIS SHAOYING , SP. NOV.

MEIGU CHINESE VOLE

Holotype. An adult male, field number MGLL75150101 (museum number: SAF07004), collected by Yang Liu on 16 May 2007. The specimen was preserved at the Sichuan Academy of Forestry as a skin, cleaned skull, penis and tissue. The external and cranial measurements (in millimetres) are as follows

(abbreviations in Material and Methods): HBL 91.0 mm; TL 45.0 mm; HFL 17.0 mm; EL 13.0 mm; SGL 23.36 mm; SBL 22.00 mm; CBL 23.30 mm; ZB 13.34 mm; IOW 4.32 mm; MB 10.60 mm; SH 8.66 mm; ABL 6.22 mm; LMxT 5.20 mm; LMbT 5.08 mm; LM M-M: 4.54 mm and OLLI: 7.46 mm. Body mass was 24 g. The skull, dentition and mandible are shown in Figure 7B 1–B 6, B 8, and pictures of the holotype are shown in the Supporting Information ( Fig. 4B).

Type locality: Lanlong region of Dafengding National Nature Reserve, Meigu county, Liangshan Canton, southwestern Sichuan, 28.62169°N, 102.9119°E; elevation 3020 m. This specimen was trapped with large steel trap (made by JMDF) in a 30-year-old spruce and fir plantation .

Paratypes: Forty specimens (18 males and 22 females). Fifteen intact adults (eight males and seven females), including four male and five female paratopotypes: MGLL75130101 ♂, MGLL75130102 ♀, MGLL75140102 ♀, MGLL7520014 ♀, MGLL 107♀, MGLL 802♂, MGLL 1005 ♀, MGLL 1006 ♂ and MGLL1106 ♂ (28.61904 – 28.62168 °N, 102.9075– 102.9149°E). Four males (BBS16002, BBS16010, BBS16014 and BBS16022) and two females (BBS16003 and BBS16011) from the Bibo Mountain ( Biboshan ; 28.505777 – 28.49971 °N, 102.360457– 102.37748°E, elevation 3300–3850 m) GoogleMaps in Yuexi county , Sichuan . Twenty-one adults with skulls broken and four juveniles (ten males and 15 females), of which 13 specimens are topotypes (MGLLI002, MGLL106, MGLL208, juvenile, MGLL209, MGLL611, MGLL612, MGLL1103, MGLL 1104, juvenile, MGLL1105, MGLLBA0505, MGLLBA1001, MGLLBA1003, MGLLBA1004, seven males and six females, 28.61932 – 28.62488 °N, 102.9075– 102.9278°E; 2840–3090 m), one specimen (MB004 ♀, juvenile) from Mabian county on the eastern side of the Dafengding Mountain peak (28.70722°N, 103.3253°E; 2560 m) GoogleMaps , and two specimens (MGDW4003 ♂, MGDW4004 ♀, juvenile) from Meigu county, western side of the Dafengding Mountain peak (28.9661°N, 103.2750°E; 2910 m) GoogleMaps . Eight specimens (BBS16012, BBS16013, BBS16015, BBS16016, BBS16017, BBS16023, BBS16028 and BBS16029, two males and six females) from the Biboshan Mountains, Yuexi county , Sichuan .

Distribution: Lannong region of Dafengding National Nature Reserve and areas surrounding the Dafengding Mountain peak, including Mabian and Meigu counties. The new species also occurs in Bibo Mountain bordering Mianning, Yuexi, Shimian and Ganluo counties, and on the mountain ridges among Yuexi, Ganluo, Ebian and Zhaojue counties.

Etymology: The new species is named for Meigu county, where the type locality, Dafengding National Nature Reserve, is located. Meigu county has the highest biodiversity in Sichuan. Dafengding National Natural Reserve also has giant panda, takin and golden monkeys, and it is the type locality of P. liangshanensis . The species epithet highlights the high value of the region.

Diagnosis: Body and head medium, usually <110 mm in length (averaging 98 mm); hindfeet <19 mm (average 17 mm). Ears relatively short, averaging <13 mm. Tail length (averaging 47 mm, less than half of HBL) equal to or slightly longer than the half length of body and head. Abrupt transition in colour between dorsal and ventral pelage; back brown. The third upper molar usually has five inner and four outer angles, or five inner and five outer angles. The third upper molar is very complex and variable; a small number of specimens have six inner or outer angles ( Fig. 7B).

Description: Pelage from neck to hip uniform brown; entire back covered with fine, long velvet hair, approximately 8–10 mm in length; proximal part of the fur black-grey and distal part yellow-brown; inner fur with small black guard hairs longer than fur. Venter grey-white and much lighter in colour than dorsum. Darker dorsal and lighter ventral pelage transitions. Margin of lip grey-black and more fuscous than laryngeal, ~18–20 mystacial vibrissae on both sides; shortest vibrissa ~ 6 mm long and longest ~ 24 mm. Base of most mystacial vibrissae black and tips white, with some either entirely black or white.

Ears as long as pelage; margin of front part covered with dense back fur, and back of ears with thinner, shorter greyish fur. Tail greyish above and grey-white below, but some with uniform colour; hair of tail tip slightly longer. Hair on dorsal surface of forefoot grey-black or grey-white; hair on ventral surface of forefeet grey and longer than on dorsal surface. Hair on dorsal surface of hindfeet grey-white and lustrous, and on ventral surface grey-black. Claws white. Five palmar and six plantar pads. Females with one pair of inguinal and one pair of pectoral mammae.

Skull slender ( Fig. 7B), straight dorsal profile, with flattened brain case. Nasals broad anteriorly, narrowing posteriorly. Posterior margin of nasals cuspate, protruding in front of maxilla. Posterior and anterior parts of frontal bone broad, median slightly narrower. Interparietal bone broad, anterior part triangle shaped and posterior margin arc shaped ( Fig. 7B). Interorbital ridge absent. Distinct temporal ridges present. Zygomatic arches medium, and middle part slightly broader. Auditory bullae moderately sized. Incisory foramen 1.5 mm wide and 4.5 mm long. Posterior palate typical of Eothenomys , ending as a thin transverse shelf without a median bony bridge ( Fig. 7B). Mandibles medium in size ( Fig. 7B). Upper incisors medium and orange. Molars rootless. The first upper molar ( Fig. 7B) with four closed triangles after the anterior transverse space, and two inner and two outer closed triangles; with three outer and three inner angles. The second upper molar with three closed triangles after the anterior transverse space and one inner and two outer closed triangles, forming two inner and three outer angles. The third upper molar (of holotype) with six triangles after anterior transverse space and an inward ‘C-shaped’ loop, only three triangles and interior transverse space closed; five inner and five outer angles, but the pattern of the third upper molar varies; of 37 specimens (excluding two adults and two juveniles with skulls broken that could not be classified), 32.4% with five inner and five outer angles, 56.8% with five inner and four outer angles, 5.4% with five inner and six outer angles, and 5.4% with six inner and five outer angles ( Fig. 7B 6, B 7).

The OLLI is 7.07 (6.86–7.60) mm. Lower incisors relatively long at 14.07 (14.34–15.28) mm, 87.7% of mandible length, and exceeding the concavity of the mandibular condyle and coronoid process. The first lower molar ( Fig. 7B 8) with a transverse posterior space, with two pairs of triangles open and confluent to each other in front of it; anteriormost with a trefoil. This tooth usually with five inner and four outer angles, but some specimens with six inner and four outer angles. The second lower molar with a transverse posterior space and two opposite pairs of triangles widely open and confluent at their bases; with three outer and three inner angles. The third lower molar with three transverse superimposed spaces and three inner and three outer angles.

The glans penis ( Fig. 8B) pole-like, slender, with a ventral groove ( Table 6). The LG averages 4.24 mm, and DG averages 2.05 mm ( Table 6). Outer crater with five unobvious papillae on all sides ( Fig. 8B). Urethral lappet has two patterns: ~50% of specimens with three forks, middle fork very short; the other 50% with two forks. Dorsal papilla large, with two fore-and-aft tips. Proximal baculum bony and bowl shaped, with slightly concave base. The TLB averages 3.84 mm and PBL averages 2.42 mm ( Table 6). Distal baculum bony and stick shaped, with proximal part obviously widened; lateral bacula processes stick shaped. The DBL averages 1.30 mm and LBL averages 0.94 mm ( Table 6).

Reproduction: Begins to reproduce in late May and typically gives birth to two offspring. Pregnancy ratio of adult females is ~44% at the end of May. In adult males, 60% individuals have orchidoptosis in May.

Habitat: Type locality is a 30-year-old planted fir and spruce forest, previously consisting of bamboo with abundant humus and bryophytes. Dafengding peak, Bibo Mountain and the other mountain ridges usually have original fir or spruce forest. All habitats occur at> 3000 m elevation in moist and abundant humus with rhododendron and bamboos.