The Cylindrophiidae are a monotypic family[2] of secretive, semifossorial, non-venomous snakes containing the genus Cylindrophis found in southeastern Asia. These are burrowing snakes and most have a banded pattern on the belly.[3] Currently, 13 species are recognized, all with no subspecies.[2] Common names include Asian pipe snakes or Asian cylinder snakes.
Cylindrophis are found in southeastern Asia from Myanmar, Laos, Vietnam, Cambodia, Thailand, and the Malay Archipelago, including Singapore, both peninsular Malaysia and Sarawak, and Indonesia, including the Greater Sunda Islands (Borneo [including Sarawak and Brunei]), Sumatra, and Java, as well as some of their offshore islands), Sulawesi, the Lesser Sunda Islands (Lombok, Komodo, Flores, Sumbawa, Timor [including Timor-Leste]), and east to the Maluku Islands (Halmahera, Wetar, Damar, Babar, and into the Tanimbar Archipelago). The eastern distributional limit, sometimes given as the Aru Islands off the southwestern coast of New Guinea, is questionable.[4][5] They are also found in Sri Lanka (but not India[6]) and in southeastern China (Fujian, Hong Kong, and on Hainan Island).[2][7][3][4]
All members of the genus Cylindrophis share the following five characteristics: 1) a relatively blunt head, not distinct from the neck, with minute eyes and a mental groove; 2) the absence of well-developed ventral scales, with ventral scales only slightly larger than or equal in size to the dorsal scales; (3) the presence of a pair of pelvic spurs in both sexes; (4) a very short tail, often with conspicuous ventral coloration; and (5) contrasting light and dark ventral blotching.[4]
The body is cylindrical, with a near-uniform diameter, which leads to the name "pipe snakes". All species are small- to medium-sized, with total lengths ranging from 12.5 cm (5 inches) to 85.7 cm (34 inches).[4]
The teeth are moderate and subequal, with 10–12 in each maxilla and none in the premaxilla. There are no fangs and no evidence of venom. The eyes have round or vertically subelliptic pupils. The head has large symmetrical shields, with the nostrils in a single nasal, which forms a suture with its fellow behind the rostral. Loreal scale is present, a small postocular scale is present. The dorsal scales are smooth, in 17, 19, 21, or 23 rows depending on the species.[3][4][8]
When threatened, Cylindrophis flatten the posterior portion of their body and arch it above the ground to display their conspicuous ventral pattern, while the head remains concealed among the body coils.[4] Only one species, C. yamdena, lacks a bold ventral pattern in most individuals, having instead an orange-pink belly without bands or spots.[9]