Contributions to Zoology, 77 (1) – 2008Johan van Rooijen; Gernot Vogel: An investigation into the taxonomy of Dendrelaphis tristis (Daudin, 1803): revalidation of Dipsas schokari (Kuhl, 1820) (Serpentes, Colubridae)
Taxonomy

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Dendrelaphis schokari (Kuhl, 1820) n. comb. (Figs. 5, 6, 7, 8)

Dipsas schokari Kuhl, 1820

Dendrophis helena Werner, 1893

Remarks. The synonymy-list is restricted to references in which data on numbers of ventral scales and subcaudal scales are given as these characters are diagnostic. Two currently recognized synonyms of D. tristis, Leptophis mankas (Bell, 1826) and Dendrophis maniar (Boie, 1827) can not be referred to either D. tristis or D. schokari and will be subjected to further research.

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Fig. 5. Dendrelaphis schokari, Sri Lanka, neotype RMNH 842.

Material examined. Sri Lanka: NMW 23669:2, NMW 24382:2, NMW 24382:3, NMW 24382:4, MNHN 1890.0065, NMW 23669:1, RMNH 842, RMNH 7066 (1), RMNH 7066 (2), BMNH 1933.12.6.12, BMNH 1969.2781; SMF 62076, SMF 62074, SMF 18672, MHNG 1198.52, MTKD D 10646, MTKD D 10440, MTKD D 15438, MHNG 1199.57, MHNG 1198.54, SMF 70286, MHNG 762.73, MHNG 1198.51, MHNG 1198.55, MHNG 1198.53, MHNG 1198.50, SMF 32366, SMF 70285; India (Malabar Coast): MNHN 244; India (Kottayam, Travancore): BMNH 1924.10.13.15, BMNH 1924.10.13.14; India (Punkanaad, Travancore): BMNH 1924.10.13.12, BMNH 1924.10.13.13; unknown locality: RMNH 7081 (1), RMNH 7081 (2), RMNH 7081 (3), RMNH 7081 (4), RMNH 7081 (5).

Neotype. RMNH 842; collector: Frank, 1853, locality: “Ceylon”, now Sri Lanka. (Figs. 5,6)

Type locality (by designation of a neotype). “Ceylon”, now Sri Lanka.

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Fig. 6. Dendrelaphis schokari, Sri Lanka, neotype RMNH 842, left side of the head.

Diagnosis. A species of Dendrelaphis, characterized by the combination of: (1) vertebral scales enlarged but smaller than the dorsals of the first row; (2) 155-177 ventrals; (3) 105-127 divided subcaudals; (4) 15 dorsal scale rows at midbody; (5) anal shield divided; (6) 1 loreal scale; (7) 2 supralabials touching the eye; (8) a short first sublabial that touches 2 infralabials; (9) 4 to 7 temporal scales; (10) 2 to 3 postoculars; (11) maximum total length 119.0 cm; (12) TAIL/TL 0.30-0.34; (13) an interparietal spot is absent (rarely rudimentarily present); (14) the presence of a light ventrolateral stripe; (15) the presence, in most specimens, of a vertebral stripe.

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Fig. 7. Dendrelaphis schokari, living specimen from Sri Lanka. Photograph by Ruchira Somaweera.

Description of the neotype. Adult female; SVL 51.0 cm; TAIL 22.5 cm; 161 ventrals (2 preventrals); 113 subcaudals, all divided; anal shield divided; 1 loreal scale (L+R); 9 infralabials (L+R); first infralabials touch at the mental groove; first sublabial touches infralabials 6 and 7 (L+R); 9 supralabials (L+R), supralabials 5 and 6 touch the eye (L+R); 2 postoculars (L+R); temporal formula: 2+2 (L+R); dorsal formula: 15-15-11; vertebral scales enlarged but smaller than the scales of the first dorsal row; width of the dorsal scale at the position of the middle ventral 2.1 mm; eye-diameter 4.9 mm (L+R); distance anterior border of eye to posterior border of nostril 4.5 mm (L+R); a dark postocular stripe starts behind the eye, covers only the lower quarter of the temporal region and ends at the edge of the jaw; a vertebral stripe, formed by yellow spots on the vertebral scales, starts behind the head and is no longer visible after the level of the 34th ventral scale; an interparietal spot is absent; a faint light ventrolateral line is present, not bordered by black lines; ground color brown, based on the color of unshed skin; supralabials and throat yellow; ventrals yellow anteriorly, yellowish-green posteriorly.

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Fig. 8. Dendrelaphis schokari, living specimen from Sri Lanka. Photograph by Ruchira Somaweera.

Variation and comparison with Dendrelaphis tristis (Daudin, 1803). Descriptive statistics with regard to D. tristis and D. schokari are provided in Table 3.

Sexual dimorphism. D. schokari exhibits sexual dimorphism in the number of dorsal scale rows one head-length before the anal shield (P < 0.00001, χ2 test). All male specimens have 9 dorsal scale rows at this position whereas 75% of the female specimens have 11 dorsal scale rows at this position.

Distribution. The examined specimens of D. schokari originated from Sri Lanka and the Western Ghats (South-West India), areas that have been shown to be biogeographically closely related (Das, 1995).