Achalinus jinggangensis (Zong & Ma, 1983)

Figs 4, 5, 6, 7, Tables 2, 4

Achalinopsis jinggangensis Zong & Ma (1983): 61–63.

Achalinus jinggangensis Tian & Jiang (1986): 110 (See remarks for details).

Common name. Zong’s Odd-scaled Snake / 井冈山脊蛇 (Ji ̌ ng Ga ̄ ng Sha ̄ n Ji ̌ She ́)

Type materials.

Holotype. • SMNH 82 X 188, adult female, collected on October 17, 1982 by Y. Zong and J. F. Ma from Dajing Village, Jinggangshan City, Ji’an City, Jiangxi Province, China (26.5599°N, 114.1290°E, 940 m asl.).

Paratype. • SMNH 82 X 004, adult male, collected on October 14, 1982 by Y. Zong and J. F. Ma, from the same locality as the holotype.

Other specimens examined

(N = 14). China. Fujian Province. • QHU R 2023011 (Field No. LFR 2023044; cited as QHU 2023011 in Xu et al. 2024 a), adult female, collected by the team of L. F. Peng on August 18, 2020 from Datian County, Sanming City (25.6589°N, 117.6924°E, 1021 m asl.); • QHU R 2024053, adult female, collected by Z. Q. Wang and Z. X. Qiu on September 11, 2019 from Datian County, Sanming City (25.6600°N, 117.6923°E, 1012 m asl.). Guangdong Province. • QHU R 2024057, adult male, collected by Z. C. Yang on October 28, 2019 from Yangshan County, Qingyuan City (24.8711°N, 112.9966°E, 1199 m asl.); • SYS r 002574, adult female, collected by the team of Y. Y. Wang on March 18, 2020 from Nanling National Forest Park, Ruyuan Yao Autonomous County, Shaoguan City (24.9137°N, 113.0506°E, 832 m asl.); • SYS r 002575, adult male, collected by the team of Y. Y. Wang on March 15, 2020 from Renhua County, Shaoguan City (25.1808°N, 113.6576°E, 195 m asl.); • SYS r 002579, juvenile female, collected by the team of Y. Y. Wang on April 12, 2019 from Mt. Fenghuang, Chaoan District, Chaozhou City (23.9479°N, 116.6556°E, 1188 m asl.), • SYS r 002703, adult female, collected by the team of Y. Y. Wang on May 19, 2018 from Yangshan County, Qingyuan City (24.9273°N, 112.9974°E, 1747 m asl.). Hunan Province. • SYS r 000715, adult female, collected on July 15, 2012; • SYS r 000829 and • SYS r 000830, two adult males, collected on May 21, 2013; all specimens were collected by the team of Y. Y. Wang from Taoyuandong NR., Yanling County, Zhuzhou City (approx. 26.503°N, 114.061°E); • SYS r 002439, adult female, collected by the team of Y. Y. Wang on July 13, 2020 from Mangshan, Yizhang County, Chenzhou City (24.9549°N, 112.9639°E, 1195 m asl.). Jiangxi Province. • QHU R 2025050, juvenile male, collected by the team of L. F. Peng on May 17, 2020 from Ganxian District, Ganzhou City (26.1006°N, 114.8059°E, 218 m asl.); • SYS r 000311, and • SYS r 000313, two adult males, collected by the team of Y. Y. Wang from Suichuan County, Ji’an City (26.2801°N, 114.0715°E, 819 m asl.), exact collection dates unknown.

Expanded diagnosis.

Based on the specimens examined in this study: (1) size medium, with a maximum SVL of 278 mm in males and 360 mm in females; (2) tail relatively short, TAL / TL ratio 0.23–0.25 in males and 0.16–0.24 in females; (3) loreal scale absent; (4) length of suture between internasals substantially longer than that between prefrontals, LSBI / LSBP ratio 1.17–2.81; (5) dorsal scales in 23-23 - 23 rows, with the outermost row enlarged and smooth, and the remaining rows are strongly keeled; (6) infralabials 5–7, with the anterior three to five in contact with the first pair of chin shields; (7) 2 (rarely 3) pairs of chin shields; (8) maxillary teeth 28 / 29 based on the only counted female specimen; (8) ventral scales 147–155 in males and 152–168 in females; (9) subcaudals 63–72 in males and 45–52 in females, not paired; (10) in life, the dorsum is uniformly black with a metallic sheen, with some individuals exhibiting white spots on both sides of the neck; the venter is black or deep blackish brown, with the anterior portion slightly paler.

Redescription of the holotype

(Fig. 4). Morphology. An adult female in a relatively good state of preservation after more than 43 years in preservative. Body slender and cylindrical; SVL 360 mm (recorded as 380 mm in the original description), TAL 80 mm, TL 440 mm; tail relatively short, TAL / TL ratio 0.18. Head slightly distinct from the neck, HL 14.23 mm, HW 8.31 mm, HW / HL ratio 0.58. Length of the suture between the internasal substantially longer than that between prefrontal, LSBI 1.76 mm, LSBP 0.88 mm, LSBI / LSBP ratio 2.0. Eye small, ED 1.50 mm.

Head scalation. Rostrum small, triangular, slightly visible from above. Nasal subrectangular and divided, with the anterior portion slightly larger than the posterior portion; nostril oval, situated in the anterior portion of the nasal. Nasal bordered by the rostral, internasal, prefrontal, and first three supralabials. Internasals 2, subtrapezoidal, with the lateral margins distinctly shorter than the medial margins in contact with each other; each internasal in contact with the rostral anteriorly, the nasal laterally, and the prefrontal posteriorly. Prefrontals two, distinctly wider than high, each in contact with the internasal, nasal, frontal, third and fourth supralabials, and the orbit. Length of the suture between the internasal substantially longer than that between prefrontal. Loreal absent (fused with the prefrontal). Frontal single, pentagonal, pointing to the rear, slightly longer than wide; FW 2.42 mm, FL 2.67 mm, FW / FL ratio 0.91. Parietals paired, elongate, much longer than wide, in contact medially. Supraocular 1 / 1. Preocular and postocular absent. Temporals 2 + 2 + 3 / 2 + 2 + 3, with both anterior temporals entering the orbit. Supralabials 6 / 6, the 4 th – 5 th contact the eye, the last one much elongated. Infralabials 6 / 6; first pair in contact with each other posterior to the mental; first to fourth in contact with the anterior pair of chin shields. Chin shields 2 / 3.

Body scalation. Dorsal scales in 23-23 - 23 rows; all dorsal scale rows except the outermost are strongly keeled. The outermost row is completely smooth and significantly enlarged. Ventrals 161 (plus 2 preventrals); cloacal plate single; subcaudals 50, not paired.

Coloration in preservative. After more than four decades in formalin, the dorsal surface of the head appears brown, with the lateral sides noticeably paler than the central region. The dorsum of the body is uniformly brown. The anterior part of the ventral surface is light yellowish brown, gradually darkening posteriorly to deep brown. The anterior margin of each ventral scale is distinctly dark brown.

Variation.

The main morphological characters of A. jinggangensis are listed in Table 2. The longest known male specimen measures 363 mm in total length (SMNH 82 X 004, paratype; SVL 278 mm, TAL 85 mm); and the longest known female specimen exceeds 444 mm in total length (QHU R 2023011; SVL 391 mm, TAL 53 + mm); TAL / TL ratio 0.23–0.25 in males, and 0.16–0.24 in females.

Scalation (Fig. 5). INS 2, PF 2, length of the suture between the internasal substantially longer than that between prefrontal, LSBI / LSBP ratio 1.17–2.81; loreal absent; temporals 2 + 2 + 3 or 4, only specimen SYS r 002574 shows pronounced variation, with 1 + 1 + 3 on left side and 1 + 4 on the other; SL 6, the 4 th – 5 th contact the eye, the last one much elongated; IL 5–7, first three or four (rarely five) in contact with the first pair of chin shields; two pairs of chin shields; only two of the 16 examined specimens have three on one side (SMNH 82 X 004 and SMNH 82 X 188). DSR 23-23 - 23; all dorsal scale rows except the outermost are strongly keeled. The outermost row is completely smooth and significantly enlarged. The numbers of ventral and subcaudal scales show pronounced sexual dimorphism; VS 147–155 in males and 152–168 in females; SC 63–72 in males and 45–52 in females; VS + SC 210–225 in males and 203–218 in females.

Dentition (Fig. 6). Based on specimen QHU R 2023011. Maxillary teeth 28 / 29, without diastema, nearly equal in size. Zong and Ma (1983) reported approximately 22 maxillary teeth for this species; however, this count differs markedly from our results obtained through high-resolution scanning, with a discrepancy of six to seven teeth. We therefore consider the earlier count to be underestimated, likely due to methodological limitations and follow the tooth counts based on the results of the present study.

Coloration in life (Fig. 7). In life, the dorsal surface of the head black, with the lateral sides slightly paler than the central region. In some individuals, the margins of the upper and lower lips white, or the supralabials and infralabials bearing distinct white spots. On each side of the neck, an irregular milky white blotch is occasionally present; this blotch is unrelated to age or sex and occurs randomly among individuals. The dorsum of the body is uniformly black with a pronounced metallic sheen and lacks a longitudinal vertebral line. The ventral surface is predominantly uniform black or deep blackish brown, with the anterior part of the venter usually slightly paler.

Coloration in preservative. Except for the two type specimens, all other specimens were collected after 2013, and their coloration is generally similar to that in life; however, the eyes appear grayish black, the metallic sheen of the body is no longer evident, and the ventral surface appears paler.

Distribution and natural history.

At present, Achalinus jinggangensis is known to be distributed in China in Jinggangshan City and Suichuan County, Ji’an City, and Ganxian District, Ganzhou City, Jiangxi Province; Yanling County, Zhuzhou City, and Yizhang County, Chenzhou City, Hunan Province; Yangshan County, Qingyuan City, Ruyuan Yao Autonomous County and Renhua County, Shaoguan City, and Chao’an District, Chaozhou City, Guangdong Province; as well as Datian County, Sanming City, Fujian Province (Zong and Ma 1983; Wang et al. 2017; this study) (Fig. 2). The species exhibits a relatively broad altitudinal range, occurring from low to moderately high elevations at approximately 195–1747 m asl. (Zong and Ma 1983; Wang et al. 2017; this study). It inhabits well-preserved subtropical evergreen broad-leaved forests (Fig. 8).

Based on field observations and published records, this species is nocturnal and is more frequently encountered after rainfall and under humid conditions. During the daytime, individuals typically shelter beneath rocks, leaf litter, or debris (Zong and Ma 1983; Wang et al. 2017; this study). Wang et al. (2017) reported that this species is insectivorous and oviparous, but did not provide specific specimens or observational records.

Conservation status.

Achalinus jinggangensis was previously assessed as Least Concern (LC) on the IUCN Red List (Wang et al. 2024). Based on the revised results of the present study, GeoCAT analysis yielded an EOO of 80,970.0 km 2 and an AOO of 16,228.8 km 2. As the species does not meet the thresholds for a threatened category under criteria B or D, we recommend retaining its current assessment as LC.

Remarks.

Zong and Ma (1983) discussed the taxonomic validity of Achalinophis Steindachner, 1913, and considered the absence of the loreal scale to represent a generic-level distinction; therefore, they recognized Achalinophis as a valid genus. In the same study, they described two specimens collected from Dajing Village, Jinggangshan, Jiangxi Province, China, as a new species, Achalinophis jinggangensis. Soon after, Zhao (1983) organized and published an article based on his discussions with M. Toriba (Japan) concerning the taxonomy and nomenclature of Chinese snakes. In that paper, M. Toriba opposed the conclusions of Zong and Ma (1983), arguing that the absence of a loreal scale in Achalinophis represents interspecific variation within the genus Achalinus Peters, 1869, rather than a diagnostic character of the generic level. Moreover, Zhao (1983) noted that all other morphological characters of Achalinophis are consistent with those of Achalinus, and therefore rejected the validity of Achalinophis as a distinct genus. Subsequently, Tian and Jiang (1986) explicitly followed the conclusions of Zhao (1983) and were the first to adopt the name Achalinus jinggangensis in their study. All subsequent works have followed this taxonomic treatment. The morphological and phylogenetic results of the present study support the conclusions of Zhao (1983) and Tian and Jiang (1986). Achalinus jinggangensis is phylogenetically nested within the genus Achalinus, and the absence of a loreal scale represents a species-level character rather than a diagnostic feature of the generic level.