Opisthotropis hungtai

Hung-Ta Chang's mountain keelback is a slender, cylindrical snake with a total length of 393.2–511 cm (155–201 in) in females and 464.3–501.2 cm (182.8–197.3 in) in males. The snout–vent length varies from 318–401.6 cm (125–158 in) in males and 312–413 cm (123–163 in) in females, while the tail length is 111.1–180.5 cm (43.74–71.06 in) in males and 81.2–99.6 cm (32.0–39.2 in) in females. The holotype male specimen had glossy dark brown scales with scattered yellow flecking on the upperside of the head, yellow chin shields with brownish black mottling at the margins, and black eyes. The body and tail are glossy dark brown with a single yellow spot on each scale, the spots getting larger towards the sides of the body. The ventral scales are yellow with brownish black lateral margins and a few scattered brown flecks, while the subcaudal scales are yellow with brownish black margins towards the front and sides. The scales on the body and tail are generally smooth, but are keeled on the underside of the tail. Other specimens of the species were very similar-looking to the holotype, but had more maxillary teeth, ventral scales, and subcaudal scales, and a relatively longer tail. When preserved in 70% ethanol, the upper side of the head and body surface are dark brown and the underside is yellowish-beige. …

Hung-Ta Chang's mountain keelback is endemic to mountainous regions in China, where it has been collected from Heishiding Nature Reserve and Dawuling Forestry Station in western Guangdong and Mount Wuhuang in southeastern Guangxi. Like other mountain keelbacks, Hung-Ta Chang's mountain keelback inhabits rocky streams; specimens have been collected in pelitic streams and gutterways next to dirt paths in Guangdong and in streams in Guangxi. The habitat near these spots consisted of dense deciduous forest. Many species of mountain keelback, including Hung-Ta Chang's mountain keelback, are threatened by the illegal wildlife trade due to their attractive coloration. Additionally, surveys in southern China are needed to better understand the species' population size and distribution.

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