Achalinus mirabilis Xu, Hu, Qi, Zhang, Zhou, Xu, Wang & Peng 2026, sp. nov.

Achalinus mirabilis Xu, Hu, Qi, Zhang, Zhou, Xu, Wang & Peng sp. nov. Figs 9, 10, 11, 12, 13, Tables 3, 4 Type materials. Holotype. • QHU R 2025051 (Field No. LFR 2025277), adult female, collected on August 17, 2025 by J. H. Hu from Kuocang Mountain, Youxi Town, Linhai City, Taizhou City, Zhejiang Province, China (28.7149°N, 121.031°E, 202 m asl.). Paratypes (N = 4). • QHU R 2025053 (Field No. LFR 2025280), adult male, collected on October 17, 2025 by J. H. Hu from Kuocang Mountain, Kuocang Town, Linhai City, Taizhou City, Zhejiang Province, China (28.8151°N, 120.9497°E, 853 m asl.); • QHU R 2025054 (Field No. LFR 2025332), adult female, road-killed specimen, and • SMNH 20250126 (Field No. LFR 2025279), subadult male, both collected by J. H. Hu on September 26, 2025 from the Kuocang Mountain, Youxi Town, Linhai City, Taizhou City, Zhejiang Province, China (28.7299°N, 121.0467°E, 163 m asl.); • SYS r 003125 (Field No. LFR 2024187), adult female, road-killed specimen, collected by H. J. Chen and J. J. Zhou on October 18, 2024 from the Kuocang Mountain, Kuocang Town, Linhai City, Taizhou City, Zhejiang Province, China (28.7976°N, 120.9343°E, 879 m asl.). Additional specimen (N = 1). • QHU R 2025052 (Field No. LFR 2025278), adult female, a fragmented road-killed specimen, collected by J. H. Hu on August 24, 2025 from the Kuocang Mountain, Youxi Town, Linhai City, Taizhou City, Zhejiang Province, China (28.7103°N, 121.0338°E, 217 m asl.). Diagnosis. The new species Achalinus mirabilis sp. nov. is distinguished from all of its congeners by a combination of the following morphological characters: (1) size medium, with a maximum SVL of 270 mm in males and 332 mm in females; (2) tail relatively short, TAL / TL ratio 0.22 in males and 0.17–0.18 in females; (3) loreal scale absent; (4) length of suture between internasals substantially longer than that between prefrontals, LSBI / LSBP ratio 1.60–3.35; (5) dorsal scales strongly keeled, arranged in 23 rows throughout the body, with the outermost row also strongly keeled and substantially enlarged; (6) infralabials 6, with the anterior three or four in contact with the first pair of chin shields; (7) two pairs of chin shields; (8) maxillary teeth 27 based on the only counted female specimen; (8) ventral scales 163–166 in males and 174–178 in females; (9) subcaudals 64–68 in males and 53–56 in females, not paired; (10) in life, the dorsum is brown to dark brown with a slight metallic sheen, and the venter is uniformly light brown. Etymology. The specific epithet mirabilis represents a Latin adjective in nominative singular, meaning “ marvelous ” or “ remarkable ”, and is given in reference to the distinctive morphology of this species within the genus Achalinus. In addition, the discovery of a previously unrecorded new species in Taizhou City, Zhejiang Province, a highly urbanized and economically developed region, was also unexpected. Based on its known distribution, Kuocang Mountain (Kuocangshan) in Linhai City, Taizhou City, Zhejiang Province, China, we propose the Chinese common name “ 括苍山脊蛇 ” (Kuo ̀ Ca ̄ ng Sha ̄ n Ji ̌ She ́) and the English common name “ Kuocang Moutain odd-scaled snake ”. Description of the holotype (Fig. 9). Morphology. An adult female in a good state of preservation. Body slender and cylindrical; SVL 332 mm, TAL 72 mm, TL 404 mm; tail relatively short, TAL / TL ratio 0.18. Head slightly distinct from the neck, HL 12.32 mm, HW 5.19 mm, HW / HL ratio 0.42. Length of the suture between the internasal substantially longer than that between prefrontal, LSBI 1.65 mm, LSBP 0.99 mm, LSBI / LSBP ratio 1.67. Eye small, ED 1.03 mm; pupil vertically subelliptic. 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, wider than long; FW 2.58 mm, FL 1.96 mm, FW / FL ratio 1.32. 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. Two pairs of chin shields. Body scalation. Dorsal scales in 23-23 - 23 rows; all dorsal scale rows, including the outermost row, are strongly keeled, with the outermost row distinctly enlarged. Ventrals 177 (plus 2 preventrals); cloacal plate single; subcaudals 56, not paired. Dentition (Fig. 10). Maxillary teeth 27 / 27, small and slender, posteriorly curved, nearly equal in size, and without diastema. Coloration in life (Fig. 11). In life, the dorsal surface of the head is brown, with the median area slightly darker than the lateral regions. The dorsum of the body is uniformly brown with a slight metallic sheen and lacks a longitudinal vertebral line. The ventral surfaces of the head and body are uniformly light brown, with the posterior margins of the ventral scales pale creamy white. The eyes are completely black. Coloration in preservative (Fig. 9). After approximately four months of preservation in ethanol, the overall coloration remains similar to that in life, but the eyes have turned grayish black and the ventral surfaces have become noticeably paler. Variation. The main morphological characters of Achalinus mirabilis sp. nov. are listed in Table 3. The longest known male specimen is 347 mm long (QHU R 2025053, paratype; SVL 270 mm, TAL 77 mm); and the longest known female is the holotype (QHU R 2025051; measurements given above); TAL / TL ratio 0.22 in males, and 0.17–0.18 in females. Scalation (Fig. 12). INS 2, PF 2, length of the suture between the internasal substantially longer than that between prefrontal, LSBI / LSBP ratio 1.60–3.35; loreal absent; temporals 2 + 2 + 3 or 4; SL 6, the 4 th – 5 th contact the eye, the last one much elongated; IL 6, first three or four in contact with the first pair of chin shields; two pairs of chin shields. DSR 23-23 - 23; all dorsal scale rows, including the outermost row, are strongly keeled, with the outermost row distinctly enlarged. The numbers of ventral and subcaudal scales show pronounced sexual dimorphism; VS 163–166 in males and 174–178 in females; SC 64–68 in males and 53–56 in females; VS + SC 227–234 in males and 227–233 in females. Coloration. In life, the two known male specimens exhibit a distinctly darker dorsal coloration, being uniformly dark brown (Fig. 13 A, B), whereas the ventral surfaces are uniformly light brown. In contrast, the remaining females, observed as fresh road-killed specimens, are similar in coloration to the holotype (Fig. 13 C, D). In females, the dorsal surface of the head is brown, paler laterally than medially; the dorsum of the body is uniformly brown and lacks a longitudinal vertebral line; and the ventral surface is uniformly light brown or pale yellowish brown. Owing to the limited sample size, it remains unclear whether this color difference is related to body size or age, or reflects sexual dimorphism. In preservative, because all specimens have been preserved for a relatively short period (≤ 1 year), their overall condition and coloration remain similar to those in life, except that the eyes have turned grayish black and the ventral coloration has become paler. Distribution and natural history. Currently, Achalinus mirabilis sp. nov. is certainly known only from Youxi Town and Kuocang Town, Linhai City, Taizhou City, Zhejiang Province, China, both of which are located within the Kuocang Mountain range (Fig. 2). The species occurs across a relatively wide elevational range, from 163 to 879 m asl. All live individuals and freshly road-killed specimens were encountered at night under clear weather conditions, in habitats including mountain roads near villages, bamboo forests, and well-preserved subtropical broad-leaved forests (Fig. 14). Conservation status. At present, Achalinus mirabilis sp. nov. is known only from a few localities within a small area of Mt. Kuocang, Linhai City, Taizhou City, Zhejiang Province, China, with an EOO of approximately 33.1 km 2. Owing to insufficient field surveys, the species is currently assessed as Data Deficient (DD). Further targeted surveys in this area and surrounding regions are needed to clarify its true distribution range and to establish appropriate conservation and management measures. Comparisons. Based on both morphological and molecular evidence, Achalinus mirabilis sp. nov. is most similar to A. jinggangensis. However, it can be clearly distinguished from the latter by the following combination of characters: (1) a distinctly higher number of VS in both sexes (163–166 in males and 174–178 in females vs. 147–155 in males and 152–168 in females); (2) higher number of SC in females (53–56 vs. 45–52); (3) higher total number of VS + SC in both sexes (227–234 in males and 227–233 in females vs. 210–225 in males and 203–218 in females); (4) the first dorsal scale row strongly keeled (vs. completely smooth); (5) slightly fewer maxillary teeth (27 vs. 28–29); and (6) in life, the dorsal surface is brown to