Fea's Viper

Neither species grows to 1 m in length. According to Liem et al. (1971), the maximum length is 77 cm, while Orlov (1997) described a male and a female measuring 72 cm and 78 cm, respectively. It is considered to be the most primitive of all viperids for several reasons. It has a reasonably sturdy body and a short tail, but the dorsal scales are smooth rather than keeled like those of most vipers. The head, which is slightly flattened and more elliptical in shape than triangular, is not covered with numerous small scales like most other vipers, but with large shields like the colubrids and the elapids. Also, the skull is built differently. It does, however, have a pair of hollow, rotating fangs, although these are short. The fangs have a ridge at the tip lateral to the discharge orifice, as well as a blade-like structure on the ventral surface otherwise seen only in some opistoglyphous and atractaspid snakes. The venom glands are relatively small. Unlike most vipers, Fea's viper is oviparous and hibernates during the winter. The color pattern of Fea's viper is striking; dorsally, its basic body color is a shiny, deep blue-gray to black, marked by several widely spaced, thin (one or two scales), white-orange crossbands. The head is orange to slightly yellow with a distinct cross-pattern outlined in gray. The eyes are yellowish with vertical pupils. …

These snakes range from northern Vietnam through southern China (Fujian, Guangxi, Jiangxi, Guizhou, Sichuan, Yunnan, Zhejiang), southeast Myanmar and southeast Tibet. The type locality is listed as "Kakhien Hills" (Kachin Hills), Myanmar. The two species are separated by the Red River, with A. kharini to the east and A. feae to the west.

This snake has a characteristic threat display. When disturbed, it flattens its body to make itself look wider, and its jaws flare outwards posteriorly, giving the normally ovoid head a triangular shape. Sometimes, it vibrates its tail. Ultimately, it will strike, during which it may or may not use its fangs. As opposed to Orlov (1997), who stated this species is nocturnal, Zhao et al. (1981) reported it to be crepuscular, active from early March into late November.