Plagiopholis pluvialis Cai, Xu, & Ma, 2025

Plagiopholis pluvialis Cai, Xu, & Ma sp. nov.

Synonym.

Trirhinopholis styani – (part: population from Sichuan) Stejneger (1925);

Plagiopholis styani – (part: population from Sichuan) Ding and Zheng (1974).

Holotype.

CIB 119370 View Materials (field number EMS 202021 ), adult male, collected by the team of Bo Cai on 10 August 2020, from Longdong Village , Huangwan Town, Emeishan City, Sichuan Province, China ( 29.5798°N, 103.2937°E, 1324 m a. s. l.). GoogleMaps

Paratypes.

Males (n = 14): CIB 10176 (field number 562244), CIB 10177 (field number 55494), CIB 10180 (field number 505119), CIB 10181 (field number 561771), CIB 10184 (field number 561773), CIB 10186 (field number 562156), CIB 10189 (field number 562153), CIB 10192 (field number 562171), CIB 10193 (field number 12014) were collected from Mt. Emei in Emeishan City, Sichuan Province, China ; CIB 10188 (field number 715013) was collected from Hongya County. Meishan City, Sichuan Province, China ; QHU 2024006 from Mt. Qingcheng , Dujiangyan City, Sichuan Province, China ; CIB XMG 2023001 , Dujiangyan Panda Valley , Chengdu Research Base of Giant Panda Breeding, Chengdu City, Sichuan Province, China ; QHU 2024007 was collected from Anziping Village , Wenchuan County, Aba Tibetan and Qiang Autonomous Prefecture, Sichuan Province, China . Females (n = 9): CIB 10178 (field number 562182), CIB 10179 (field number 562180), CIB 10182 (field number 562266), CIB 10185 (field number 561772), CIB 10187 (field number 561775), CIB 10191 (field number 562297), FMAEM were collected from Mt. Emei in Emeishan City, Sichuan Province, China ; CIB CB 25 DY 01 , a roadkilled male, was collected from Dayi County in the Chengdu Section of Giant Panda National Park , Sichuan Province, China ; SYS r 002035 was collected from Baima Mountain Forest Farm , Bijie City, Guizhou Province . Juveniles (N = 2): CIB CB 2024 EMS 001 was collected from Mt. Emei in Emeishan City, Sichuan Province, China ; CIB 10183 (field number 595027) was collected from Hongya County, Meishan City, Sichuan Province, China .

Diagnosis.

Plagiopholis pluvialis sp. nov. can be diagnosed from other Plagiopholis species by the following unique combination of characters: (1) no loreal (rarely 1), posterior nasal forming a suture with the single preocular; (2) two postoculars; (3) temporals 2 + 2 (rarely 2 + 1); (4) 6 supralabials, the 3 rd and 4 th entering the eye; (5) 6 infralabials; (6) maxillary teeth 18 in males; (7) dorsal scale smooth and rows 15-15 - 15; (8) ventral scales 102–110 in males and 114–122 in females; (9) anal entire; (10) subcaudal scales 26–31 in males and 16–26 in females; (11) longer tail length 40–59 mm (mean 49 mm) in males, and shorter tail length 34–47 mm (mean 40 mm) in females; (12) larger TAL / SVL ratio of 0.14–0.21 (mean 0.18) in males and lower TAL / SVL ratio of 0.12–0.15 (mean 0.14) in females; (13) hemipenis half divided, bilaterally symmetrical, the truncus spinulate throughout; (14) a relatively narrow, black-brown blotch is present on the neck, often inverted “ V ” shaped, across 2–3 dorsal scale rows; (15) dorsal surface of the body is olive, with some dorsal scale edges yellow and black, forming a reticulated pattern.

Description of the holotype.

Measurements and scalation. An adult male with TL 322 mm ( SVL 282 mm and TAL 40 mm); tail relatively short, TAL / TL ratio of 0.12, and TAL / SVL ratio of 0.14; body slender and small; head slightly distinct from the neck, HL 11.5 mm, HW 7.6 mm, HH 5.7 mm; eye moderate, ED 2.3 mm; rostrum triangular, wider than high, slightly visible from above; snout relatively short, ESD 4.1 mm; internasals and prefrontals paired; frontal hexagonal, longer than wide, a little shorter than the parietals; PRO 1 / 1, PO 2 / 2; loreal absent; TEMP 4, arranged in two rows (2 + 2 / 2 + 2); SL 6 / 6, the 3 rd and 4 th entering the eye, the 6 th largest; chin shields in 2 pairs, the anterior pair longer than posterior one and in contact with the mental; IL 6 / 6, the 1 st to 3 rd touching the first pair of chin shields. DSR 15-15 - 15, all smooth, including the outermost row on both sides; VS 108, SC 27, CP entire.

Dentition. Maxillary teeth 18, without diastema; except for the first 3 being smaller, the rest are nearly equal in size.

Coloration in life. In life, dorsal surface of the head is olive, with small black-brown spots scattered along the sides; the supralabials are wheat with broad black edges on both sides. Ventral surface of head wheat, partial scales have irregular black-brown patches. A relatively narrow, black-brown collar is present on the neck, inverted “ V ” shaped, across 2–3 dorsal scale rows. Dorsal surface of the body is olive, with some dorsal scale edges gold and black, forming a faint reticulated pattern. The ventral and subcaudal scales uniform wheat. (Fig. 12 View Figure 12 ).

Coloration in preservation. In preservation, the coloration still resembles the specimen in life (Figs 13 View Figure 13 , 14 View Figure 14 ).

Variation.

The main morphological characters of Plagiopholis pluvialis sp. nov. are listed in Table 6 View Table 6 . All known specimens exhibit a similar morphological pattern to the holotype, but there is pronounced sexual dimorphism: compared to females, the examined males have a significantly long tail, TAL / TL ratio of 0.12–0.18 and TAL / SVL ratio of 0.14–0.21 (vs. TAL / TL ratio of 0.11–0.13 and TAL / SVL ratio of 0.12–0.15 in females), fewer ventrals (102–110 vs. 114–122 in females), more subcaudals (26–31 vs. 16–26). Most specimens have temporals 2 + 2 on each side, but the left of CIB 10182 (field number 562266) is 2 + 1. Most specimens loreal absence but the female specimen USNM 65505 in Stejneger (1925) has one loreal on each side.

Hemipenis. Description based on the everted left organ of the male paratypes QHU 2024006 and QHU 2024007 (Fig. 15 View Figure 15 ). When fully everted, the hemipenis is Y-shaped, bilaterally symmetrical, extends to SC 7 in QHU 2024007 and SC 8 in QHU 2024006 , bifurcates at about lower 5 / 9. Both sulcate and asulcate surfaces densely ornamented with spinules, spines, or calyxes. Truncus spinulate throughout, branches divided into spine and calyx areas; a well-developed, calcareous basal hook is present on the asulcate surface of each branch.

Spine area characterized by medium-sized, dense spines, gradually decrease in size distally, reaching nearly half of the branches, then merging into thorny calyces. The calyx area extends to the distal end of each branch. The sulcus spermaticus is divided, extending centrifugally to the tip of each branch, and the sulcus lips are visible and slightly raised.

Etymology.

The Latin specific epithet pluvialis means ‘related to rain’ or ‘rainy,’ indicating that the species inhabits particularly moist environments, especially within the West China Rain Zone in China. It is suggested that the English name for this species be “Western China Mountain Snake” and the Chinese name be “ 华西颈斑蛇 (hua ́ xi ̄ ji ̌ ng ba ̄ n she ́) ”.

Distribution and natural history.

This species is known to be distributed in mountainous areas at altitudes of 744–1900 m at several localities, including Wenchuan County in Aba Tibetan and Qiang Autonomous Prefecture; Anzhou District in Mianyang City; Dayi County and Dujiangyan City in Chengdu City; Hongya County in Meishan City; and Emeishan City in Leshan City, all in Sichuan Province, China; as well as Qixingguan District in Bijie City and Mt. Fanjing in Tongren City, both in Guizhou Province, China ( Stejneger 1925; Pope 1929, 1935; Zhao et al. 1998; Zhao 2006; Zhong et al. 2015; Liu et al. 2025, and this study). The distribution areas fall within the mid-subtropical monsoon climate zone characterized by mixed evergreen and deciduous broad-leaved forests, where four distinct seasons are observed, with hot and rainy summers and mild, less rainy winters ( Zheng et al. 2013). Particularly the snake’s main distribution area lies within the West China Rain Zone in Sichuan, a unique geographical region known for its significant rainfall due to the convergence of various climatic fronts, making it one of the wettest places in China.

Pope (1929, 1935) documented that the stomachs of two specimens from Mt. Emei had eaten an earthworm apiece and found 5, 6, and 11 eggs, respectively, in three Mt. Emei females. One of the eggs in the clutch of 5 measured 19 × 11 mm and contained a very small embryo, while the female with 11 eggs was collected in July. This new species is also certainly oviparous.

Comparisons.

Plagiopholis pluvialis sp. nov. differs from P. styani and P. acuta sp. nov. by having the following combined characteristics: (1) a relatively narrow, black-brown blotch is present on the neck, often inverted “ V ” shaped, across 2–3 dorsal scale rows (vs. a wide, black-brown blotch is present on the neck, often pentagonal or irregularly semiring-shaped, across 4 to 6 dorsal scale rows in P. styani and P. acuta sp. nov.); (2) the truncus of the hemipenis spinulate throughout (vs. smooth in P. styani ); (3) maxillary teeth 18 in males (vs. 20–21 in P. styani in males); (4) fewer ventral scales 102–110 in males (vs. 114–115 in P. acuta sp. nov. and 114–121 in P. styani in males); (5) the dorsal surface of the body is olive, with some dorsal scale edges gold and black (vs. brick-red, with some dorsal scale edges black in P. styani and P. acuta sp. nov.); (Fig. 16 View Figure 16 ). A detailed comparison between the new species and its congeners is summarized in Table 5 View Table 5 .

Plagiopholis pluvialis sp. nov. can be easily separated from P. blakewayi , P. nuchalis , and P. delacouri by having TEMP 2 + 2 (vs. 0 / 1 + 1 in P. blakewayi , 1 + 2 in P. nuchalis and P. delacouri ) and significantly different body coloration. Moreover, it can also be separated from P. blakewayi due to the more supralabials (6 vs. 5).