Jack's Water Snake

description

Description of the Holotype. A female, total length 457 mm, tail 112 mm. Rostral broader than tall, slightly visible from above, protrudes over mental scale; nasals very large, semi-divided; internasal divided; prefrontals large, make broad contact with loreal; frontal slightly fragmented, equal in length to parietals; large occipital present on right side only. Supraoculars quadrangular, wider than the frontal; preoculars 1 / 1; suboculars 3 / 4; postoculars 2 / 2; temporal formula 1 + 2 / 2 + 2; upper labials 12 / 12, 1 – 4 contact loreal; first horizontally divided upper labial number 7 (Fig. 8). Lower labials 17 / 19, first 3 contact first pair of chin shields, first divided labial is 10. Dorsal scales keeled, striated, and in 42 – 44 – 33 rows; 170 ventrals; 94 divided subcaudals, a few fused. Dorsal pattern of 24 pale colored bands bordered in black, about 1.5 to 2 scale rows wide, separated by dark brown blotches 4 to 5 scale rows wide; the bands go completely across the vertebral line at midbody first three dorsal rows lack the dorsal pattern, and are uniform yellow. Ventral surface of body uniform yellow-cream with dark lateral spot on outer edge of some ventrals; ventral

The masked water snakes of the genus Homalopsis Kuhl & van Hasselt, 1822 (Squamata, Serpentes, Homalopsidae), with the description of a new species

diagnosis

Diagnosis. Homalopsis mereljcoxi has a single loreal contacting upper labials 1 – 4; 40 – 47 scale rows at midbody, reduced to 30 or more posteriorly; two postocular scales plus a postsubocular; 13 (12 – 14) upper labials; and ventral counts that are usually greater than 165. Homalopsis buccata has 33 – 40 dorsal scale rows at midbody, reduced to less than 30 posteriorly; one postocular scale plus a postsubocular scale; and a ventral count that is less than 166. Homalopsis hardwickii has a divided loreal contacting upper labials 1 – 4; 39 scale rows at midbody reduced to 28 posteriorly; one postocular scale and no presubocular scale; 159 ventrals. Homalopsis nigroventralis has upper labials 1 – 3 contacting the loreal; 35 – 39 dorsal scale rows at midbody, reduced to less than 30 posteriorly; 10 – 12 upper labials; 159 – 167 ventrals; and a reverse color pattern on the venter (dark olive-gray with white spots). Homalopsis semizonata has a divided or fragmented loreal contacting upper labials 1 – 4 or 1 – 5; three prefrontals; one postocular and one postsubocular.

The masked water snakes of the genus Homalopsis Kuhl & van Hasselt, 1822 (Squamata, Serpentes, Homalopsidae), with the description of a new species

discussion

Comment. Photographs of this snake can be found in: Cox (1991: 223, pl 61), Cox et al. (1998: 42), Lim & Lee (1988: 70), Manthey & Grossmann (1997: 356), and Murphy (2007: 194). Field and laboratory studies and observations that relate directly to this species include the following: Brooks et al. (2007, 2008, 2009, 2010), Karns et al. (2005, 2010), Murphy et al. (1999), St. Girons (1972), and Saint Girons & Pfeffer (1971, 1972).

The masked water snakes of the genus Homalopsis Kuhl & van Hasselt, 1822 (Squamata, Serpentes, Homalopsidae), with the description of a new species

distribution

Distribution. Homalopsis mereljcoxi is known from lowland localities in Thailand, Cambodia, and Vietnam. On the western edge of its known range it is found as far north as Bung Cho, Uttaradit Province, Phichai District (~ 12 ° N, 104 ° E), Thailand and as far south as Lake Songkhla (~ 7 ° N, 100 ° E), Thailand. In Vietnam it is found at least as far east as Can Tho Province (~ 10 ° N, 105 ° E) and as far south as Vinh Thuan District Town in Kien Giang Province (~ 9 ° N, 105 ° E). It is present in Cambodia’s Tonle Sap, and it most likely occurs throughout the lower elevations of the Chao Phraya and Mekong drainages. It is possible, but unclear, if this species inhabits Myanmar. Gyi (1970) reports Myanmar Homalopsis with 39 – 43 middorsal scale rows, Homalopsis semizonata Blyth, 1855 inhabits the area on both side of the Gulf of Martaban and the Ayeyarwady delta and it has 38 - 43 scale rows which overlap the range of scale rows for H. mereljcoxi. Natural history. Many authors have discussed the natural history of this species (Saint Girons 1972; Brooks et al. 2007, 2010; Karns et al. 2005, 2010) under the name Homalopsis buccata. The morphology of this species agrees well with the C

The masked water snakes of the genus Homalopsis Kuhl & van Hasselt, 1822 (Squamata, Serpentes, Homalopsidae), with the description of a new species