A new genus and species of xenodermatid snake from Laos

The Asian family Xenodermatidae includes five genera: Xenodermus Reinhardt, 1836 (1 species), Achalinus, Fimbrios, Stoliczkaia, and Xylophis, and hold a total of 17 species. The Philippine genus Oxyrhabdium has been removed from the family based on molecular evidence, nevertheless, its phylogenetic position should be further investigated as it is now classified as Elapoidea incertae sedis. This family has long been considered to be a subfamily of the Colubridae. Recent phylogenetic studies suggest this well-defined assemblage deserved family status. These genera include species with more or less highly modified cephalic (labials with raised and everted edges, presence of ridges of skin between rostral and internasals, and a large loreal) and dorsal scalation (usually small scales, subequal or intermixed with large scales). The Neotropical genus Nothopsis Cope, 1871, previously also referred to the family Xenodermatidae, but was transferred to the family Dipsadidae and the members of Xenodermatidae are currently known only from Asia, ranging from India eastward to Japan and Taiwan, and southward to Borneo and Java, possibly also the Philippines.

Malcom Smith erected the monotypic snake genus Fimbrios for Fimbrios klossi, and described it from Da Lat, Langbian Plateau in southern Vietnam in 1921. This species was subsequently recorded from the Elephant Mountains, in southwestern Cambodia, and from central and southern Vietnam. Although it has been recorded close to the Laotian border, it was not recorded from the Laos until 2008, when a specimen was collected in the Paksong District, Champasak Province, in Boloven Highlands. Two additional specimens, found in 2007 and 2008 in the same locality of the Boloven Highlands between 1,320 and 1,340 m asl. Fimbrios smithi was described in 2008 on the basis of a specimen obtained in the karst forest of Phong Nha—Ke Bang National Park, Quang Binh Province, in central Vietnam.

In a new paper Teynié et al. describe a new genus and species of xenodermatid snake from Laos based upon a specimen collected during a trip in the northern part of Louangphabang Province, which presented several diagnostic characters of the genus Fimbrios. The male snake and a second specimen observed in Houaphan Province, North Laos, share morphological characters with the Asian genus Fimbrios including erected edges on the first supra and infralabial scales, but differ in having fewer dorsal scale rows (25–27 vs. 30–33), fewer maxillary teeth (27 vs. 30–35), posterior teeth progressively slightly enlarged, and especially the correspondence of two dorsal scale rows per ventral plate throughout the body (i.e. the first dorsal scale row made of a small scale above the fore part of a ventral, followed by a much larger scale above its hind part), a condition known only in Xenodermus Reinhardt, 1836.

As the Laotian specimens differ in morphological and molecular characters from other xenodermatids, Teynié et al placed these specimens in a new genus, Parafimbrios and describe them as Parafimbrios lao. Besides the characters mentioned above, the new species is diagnosed by a combination of the following ones: small, strongly keeled dorsal scales; rostral and first four supra- and infralabials with raised, erected edges; horizontal tissue ridges above the rostral; loreal single, large, elongate; ventral scales 177–189; subcaudals 55–56, undivided; dorsal color purplish-grey, neck with a broad, very pale grey collar reaching downwards the pale grey color of the venter. Parafimbrios laos is the 111th snake species recorded from Laos.

The holotype was discovered in a steep, rocky evergreen forest, with some trees of primary forest remaining, surrounding a rugged karst formation. The holotype was found lying motionless at night during the rainy season on a rocky outcrop among a large pile of rocks at the foot of a limestone cliff of the karst formation at an elevation of 360 m. The adjacent lowland is mainly covered with rice fields, patches of secondary forests and a few scrub and grasslands. The second specimen was observed near the city of Vieng Xai, where no large primary forest remain. This specimen was observed in the same general karstic environment as the holotype. Neither specimen displayed any reaction and remained perfectly motionless when they were photographed. When they were handled, they did not try to form a “ball”, a defensive posture frequent in Fimbrios klossi, nor did they display any other defensive action. Nothing else is known on the biology of Parafimbrios lao, stomachs of both specimens were empty.

Citation

Teynié, A., David, P., Lottier, A., Le, M. D., Vidal, N., & Nguyen, T. Q. (2015). A new genus and species of xenodermatid snake (Squamata: Caenophidia: Xenodermatidae) from northern Lao People’s Democratic Republic. Zootaxa, 3926(4), 523-540.