Angel's Keelback

conservation

Conservation status. Currently, Rhabdophis angeli, as well as Rhabdophis guangdongensis syn. nov., are assessed as Data Deficient (DD) under the IUCN Red List categories (Stuart & Nguyen 2012; Qi et al. 2024). Rhabdophis angeli is reliably known from seven localities across Phu Tho Province, Vietnam, and Guangdong Province, China, including one national park. Although the species appears relatively widespread geographically, it remains rare throughout its known range, possibly due to a highly secretive way of life in humid areas. Notably, extensive field surveys conducted by T. V. Nguyen in 2022, 2023, and 2024 at Tam Dao NP failed to yield any additional specimens. The principal threat to this species is habitat loss and degradation, particularly in Tam Dao NP, where habitat destruction and large-scale tourism infrastructure development are ongoing and intensively (T. V. Nguyen pers. obs.). Although critical aspects of the species biology, including its full distributional extent, population dynamics, reproductive behaviour, ecology, and toxicology, remain poorly understood, we suggest that Rhabdophis angeli be classified as Near Threatened (NT) according to the criteria of the IU

Molecular and morphological evidences for considering Rhabdophis guangdongensis Zhu, Wang, Takeuchi & Zhao, 2014 a junior synonym of Rhabdophis angeli (Bourret, 1934) (Squamata: Natricidae)

description

Description of the holotype of Natrix (Rhabdophis) angeli Bourret (Fig. 1) Habitus. Body elongate and cylindrical; head distinct from neck; snout moderately long; eyes large with rounded pupils; tail of moderate length, slender, and gradually tapering. Body size. SVL 358 mm, TaL 75 mm, TL 433 mm, TaL / TL ratio 0.173. Body scalation. Dorsal scale rows 15 - 15 - 15; dorsal scale rows feebly keeled, the outer most are smooth; 123 ventral scales, laterally slightly angulate; 42 subcaudals, paired and laterally slightly angulate; cloacal plate divided. Head scalation. Rostral wider than high, triangular, hardly visible from above; posterior rostral scale suture bordering internasals and forming a straight angle in dorsal view; nasal vertically divided by a furrow below and above the nostril; nostril large and lateral, piercing in a completely divided nasal; nasal surrounded by the first two supralabials, rostral, internasal, prefrontal, and loreal; internasals paired, anterior sutures slightly concave in dorsal view, in contact anteriorly with the rostral, and laterally with the nasal, followed by the prefrontal; each internasal slightly wider than long; prefrontals paired, large, subr

Molecular and morphological evidences for considering Rhabdophis guangdongensis Zhu, Wang, Takeuchi & Zhao, 2014 a junior synonym of Rhabdophis angeli (Bourret, 1934) (Squamata: Natricidae)

diagnosis

Revised diagnosis. Rhabdophis angeli can be diagnosed by the combination of the following characters: (1) head well distinct from the neck; (2) maxillary teeth 20 – 23, the posterior-most two or three teeth abruptly enlarged, not grooved, and not separated by diastema from the rest of the series; (3) supralabials six (rarely five), the third and fourth touching the eye; (4) seven or eight infralabials, the first four in contact with anterior chin shields; (5) dorsal scales in 15 rows throughout, feebly keeled, the outer row smooth; (6) ventrals 118 – 127; (7) subcaudals 38 – 47; (8) top of head, occiput, and nape (anterior to the black collar) grey; (9) a broad black collar, posteriorly bordered by a reverse V-shaped orange mark on the nape; (10) dorsal surface of body and tail brownish-grey, bearing narrow black cross-bars; (11) body and tail each with two dorsolateral longitudinal brownish-red lines, each line accompanied by a series of white spots within the cross-bars; (12) lips bearing two conspicuous black oblique bands, one below the eye and one behind the eye; (13) ventral surface of head and neck cream-coloured with black spots, gradually becoming entirely black posteriorl

Molecular and morphological evidences for considering Rhabdophis guangdongensis Zhu, Wang, Takeuchi & Zhao, 2014 a junior synonym of Rhabdophis angeli (Bourret, 1934) (Squamata: Natricidae)

distribution

Distribution and natural history notes (Fig. 5). Rhabdophis angeli is currently known from Tam Dao NP, Phu Tho Province, Vietnam, as well as from several localities in Guangdong Province, China, including Aizhai Village (Renhua County), Mt. Wutong (Shenzhen City), Mt. Nankun (Huizhou City), Mt. Yinping (Dongguan City), and Mt. Tianjing (Shaoguan City). Given the species geographic range, it is likely that R. angeli also occurs in Guangxi Province, China, and possibly in other provinces of northeastern Vietnam. This species is terrestrial and primarily diurnal. It preys predominantly on earthworms and inhabits lowland evergreen forests and submontane forests at elevations ranging from 56 to 900 m asl (Zhu et al. 2014; present study).

Molecular and morphological evidences for considering Rhabdophis guangdongensis Zhu, Wang, Takeuchi & Zhao, 2014 a junior synonym of Rhabdophis angeli (Bourret, 1934) (Squamata: Natricidae)