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| Dendrelaphis thasuni (A) Dorsal aspect of D. thasuni sp. nov. female holotype; (B) dorsal aspect of uncollected D. caudolineolatus female. Atthanagoda, Silva, Vogel, Udayanga, Bandara, Madawala, Grismer & Karunarathna, 2025 Thasun’s Bronzeback || https://amphibian-reptile-conservation.org/issues.php |
Abstract
We describe a new species of Dendrelaphis that is morphologically close to D. caudolineolatus, however the new species is readily distinguished from it by having an undivided anal plate, as well as other characters. This species is only known from a single female collected from Maragala Mountain in Monaragala District, Uva Province of Sri Lanka. The new species is likely adapted to an arboreal lifestyle and its color is similar to that of the tree branches it inhabits. Currently, eight species of Dendrelaphis inhabit Sri Lanka (including the new species), six of which are endemic, and most of them are threatened. The Maragala Mountain is a biodiversity rich area in Sri Lanka because of its habitat heterogeneity and favorable climatic conditions. Currently, 67 species of reptiles (30 endemics), and 18 amphibians (five endemics) are known to inhabit this mountain. Various habitats on Maragala Mountain have been heavily influenced and modified by humans. Therefore, urgent conservation measures are needed to conserve this isolated forest and its resident species.
Keywords. Asia, Isolated hill forest, reptile hotspot, snake diversity, speciation, systematics
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| Holotype of Dendrelaphis thasuni sp. nov. in life (above) and uncollected D. caudolineolatus (below) together to compare scalation, color pattern, and eye size. |
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Morphological characters of Dendrelaphis thasuni sp. nov. female holotype. (A) Dorsal aspect of head, (B) ventral aspect of head, (C) lateral aspect of head on left side with narrow temporal stripe, (D)lateral aspect of head on right side, (E) dorsal aspect of trunk with slightly enlarged vertebral scales, (F) dorsal aspect of tail base with large scales, (G) ventral side of trunk with narrow ventral scales, (H)ventral side of tail base with undivided anal plate, (I) lateral aspect of trunk with narrow blackish transverse dorsolateral bars, (J) lateral aspect of tail base with dorsolateral black line. Morphological characters of an uncollected Dendrelaphis caudolineolatus female. (A) Dorsal aspect of head, (B) ventral aspect of head, (C) lateral aspect of head on left side with broad temporal stripe, (D) lateral aspect of head on right side, (E) dorsal aspect of trunk with enlarged vertebral scales, (F) dorsal aspect of tail base with extra-large scales, (G) ventral side of trunk with broad ventral scales, (H) ventral side of tail base with divided anal plate, (I) lateral aspect of trunk with broad blackish transverse dorsolateral bars, (J) lateral aspect of tail base with dorsolateral black line. |
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(A) Dorsal aspect of Dendrelaphis thasuni sp. nov. female holotype in life with narrow blackish transverse dorsolateral bars, (B) dorsal aspect of uncollected D. caudolineolatus female with broad blackish transverse dorsolateral bars. (A) Ventral aspect of Dendrelaphis thasuni sp. nov. female holotype in life with narrow ventrals, (B) ventral aspect of uncollected D. caudolineolatus female with broad ventrals. |
Dendrelaphis thasuni sp. nov.
Thasun’s Bronzeback
Diagnosis. The head is distinct from the slender body; two internasals, snout broad and flat, equal to eye diameter; large eye with round pupil; one preocular and one loreal; two postoculars; 1+2 temporal scales bearing a very narrow black stripe (Figs. 4 and 5); V-shaped blackish transverse dorsolateral bars on anterior half of body; distance between transverse bars in forebody is equal to the eye diameter, with 2–3 lateral scales between two transverse dorsolateral bars; 151 enlarged vertebral scales and no vertebral stripe; dorsal scale rows one head length behind neck (~20 mm) 13, at midbody 13, one head length anterior to vent (~20 mm) 9; apical pits 1–3 on dorsal scales; 153 ventral scales, very narrow between lateral keels of both sides compared to D. caudolineolatus; anal plate undivided, large; tail long with 117 or 118 divided subcaudals; a thin blackish line between subcaudals; subcaudals with strong lateral keels. Dendrelaphis thasuni sp. nov. is most similar to D. caudolineolatus in Sri Lanka, which is its presumed closest relative. It can be easily distinguished from all species of Sri Lankan Dendrelaphis by having an undivided anal plate (Fig. 6).
Etymology. The specific epithet is a Latinized eponym in the masculine genitive singular, honoring Dr. Amarasinghe Achchige Thasun Amarasinghe—a renowned systematic biologist, ecologist, and conservationist—for his remarkable contributions to the field of taxonomy and systematic herpetology in Asia, especially in Sri Lanka, Indonesia, and India, and for his friendship. He has also helped to popularize wildlife conservation and management in Sri Lanka through science-based education awareness programs.
Anusha Atthanagoda, Anslem de Silva, Gernot Vogel, Sithara Udayanga, Champika Bandara, Majintha Madawala, L. Lee Grismer and Suranjan Karunarathna. 2025. A New Species of Dendrelaphis Boulenger, 1890 (Reptilia: Colubridae) from an isolated misty mountain in the South Eastern intermediate zone of Sri Lanka. Amphibian & Reptile Conservation. 19(1): 28–47 (e340). April 2025