Boomsong's Stream Snake

biology_ecology

Biology. This species has been recorded from 700 m up to 1,780 m a. s. l. Specimens mentioned by Cox (1995) were taken from a mountain stream. Recognition of Isanophis requires a redefinition of Parahelicops, which is currently monotypic:

On the taxonomic status of the Thai endemic freshwater snake Parahelicops boonsongi, with the erection of a new genus (Squamata: Natricidae)

description

Description. Body cylindrical, thick and stout; head elongate, well distinct from the neck, flattened; snout elongate, flat, broadly rounded, approximately 24 % of HL, or 1.1 – 1.4 times as long as the horizontal diameter of eye; nostrils placed dorsolaterally on the snout and directed obliquely upwards; eye diameter 1.5 times as large as the distance between its lower margin and the margin of the lip, with a round pupil; tail long and tapering. The maximal total length known is 990 mm (SVL 750 mm; TaL 240 mm; specimen depicted in Cox et al. 1998, 2012). Ratio TaL / TL: 0.242 in the only specimen with a complete tail (same specimen as above; sex unrecorded). Dentition. 29 – 30 maxillary teeth, the last three distinctly enlarged, without diastema. Body scalation. DSR: 19 – 19 – 17; scales notched posteriorly, strongly keeled throughout, with a thick keel; 1 st DSR weakly keeled anteriorly, distinctly keeled posteriorly. Scale row reductions (holotype): 19 → 17 DSR at VEN 78 (left) & 84 (right). VEN: 136 – 140 (plus 1 preventral); SC: 60 in the only specimen with a complete tail, all paired; anal plate divided. Ratio VEN / SC 2.33 (in the only specimen with complete tail). Position o

On the taxonomic status of the Thai endemic freshwater snake Parahelicops boonsongi, with the erection of a new genus (Squamata: Natricidae)

diagnosis

Diagnosis. See above the generic characters plus: (1) large size, up to at least 990 mm; (2) 19 – 19 – 17 DSR, all strongly keeled; (3) 29 maxillary teeth in the holotype, the last three distinctly enlarged; (4) a long tail, with a ratio TaL / TL reaching at least 0.24; (5) 136 – 140 VEN, 60 SC in the holotype; (6) 8 – 9 SL; (7) 2 anterior temporals; (8) body uniformly dark ochre-brown (dark chestnut brown in life), somewhat paler and more beige on the lower part of the sides (dark reddish-brown); and (9) venter uniformly pale ochre-brown (pale yellowish-brown in life).

On the taxonomic status of the Thai endemic freshwater snake Parahelicops boonsongi, with the erection of a new genus (Squamata: Natricidae)

distribution

Distribution. Thailand. Isanophis boonsongi is known only from Dan Sai District and Phu Ruea [or Phu Rua] District, Loei Province. Based on the distributions of other species (e. g., Paratapinophis praemaxillaris Angel, 1929), we think it is likely to occur in north-western Laos.

On the taxonomic status of the Thai endemic freshwater snake Parahelicops boonsongi, with the erection of a new genus (Squamata: Natricidae)