Trimeresurus gracilis

Trimeresurus gracilis, commonly known as the Taiwan pit viper or Taiwan mountain pitviper, is a venomous pit viper species endemic to Taiwan. No subspecies are currently recognized. The species is known as kikushi habu in Japanese.

Description
Trimeresurus gracilis is a small snake with a total length up to 60 cm. Scalation includes 19 (or 21) rows of dorsal scales at midbody, 144–149 ventral scales, 43–53 subcaudal scales, and 7–8 supralabial scales.

Geographic range
It is found only in Taiwan, above 2,000 m above sea level. The type locality given is "Mt. Noko, Nanto". According to Zhao and Adler (1993), this would be "Mt. Nôkô, Nanto Co., central Formosa" (Mount Nengkaoshan, Nantou County, Taiwan). In a study were results that negated a commonly believed inference relating to the close affinity of T. monticola and T. okinawensis, and also suggested a sister relationship between T. okinawensis and T. gracilis. Phylogenetic relationships revealed in this study suggested that the genus Trimeresurus dispersed into the Ryukyu region at least three times, and that T. flavoviridis and T. tularensis from the central Ryukyus use to be more widespread and diverse in the past surrounding regions.