Macrocalamus lateralis, LATERALIS GUNTHER, 1864

Quah, Evan S H, Anuar, Shahrul, Grismer, Lee L, Wood, Perry L & Mohd Nor, Siti Azizah, 2020, Systematics and natural history of mountain reed snakes (genus Macrocalamus; Calamariinae), Zoological Journal of the Linnean Society 188 (4), pp. 1236-1236 : 1236-

MACROCALAMUS LATERALIS GÜNTHER, 1864

SIDE- BLOTCHED REED SNAKE

( FIG. 3 )

Macrocalamus lateralis Günther, 1864: 199 , pl. 18: fig. D.

Macrocalamus lateralis Vogel & David 1999: 309– 332 (in part); Das 2010: 285, pl. 48.

Holotype: BMNH 1946.1 .7.23. Type locality: ‘ The continent’, with no precise locality. Specified to the mainland part of the State of Penang by David & Pauwels (2004).

Diagnosis: Adults reach 262 mm SVL, 297 mm TL. Head relatively stocky, triangular and indistinct from neck; snout pointed; loreal fused with prefrontal; one preocular; one postocular; eight supralabials, fourth and fifth touching eye; seven infralabials; 1 + 2 temporals; 15 dorsal scale rows at midbody; dorsal scales smooth; ventrals 112–122 (males 112–114 and females 122); cloacal scale single; 14–24 subcaudals (males 21–24 and females 14); ( David & Pauwels, 2004; present study).

Coloration in life: The dorsum is ochre to brown in colour with a light cream, oblique streak on the neck that extends from the parietals and temporals to the venter posterior to the jaws. The snout is lighter in colour, with pale labial markings. No additional oblique streaks or markings occur on the neck or the anterior portion of the body. Elongate, cream–yellow ocelli edged posteriorly with dark brown located on the scales of the fifth and sixth dorsal scale rows and are evenly spaced along the length of the body and the dorsal surface of the tail. Double, parallel, dark brown lateral stripes run the length of the body, beginning on the first ventral scale and extending to the vent. The first stripe results from the brown edging along the ventral scale margins, and a thin cream stripe separates the two darker ones. The venter is cream– yellow, with dark brown speckling near the lateral margins of the ventrals. The underside of the tail is uniform cream–yellow ( Fig. 3 ; David & Pauwels, 2004).

Variation: In the specimens from Langkawi Island, the double, dark, ventrolateral stripes are not as clearly defined as in the Thai specimen ( David & Pauwels, 2004: figs 5, 6), because the upper stripe is faint and diffuse. The oblique, light-coloured streak on the nape and neck is also not as prominent in the Langkawi specimens in comparison to the Thai specimen. In the Langkawi specimens, the colour of the venter also ranges from yellow to orange, with varying degrees of speckling along the margins of the ventral scales. The subcaudal region has a series of dark spots along the midline, creating a faint median line.

Distribution: This species is found in northern Peninsular Malaysia in mainland Penang State and on Langkawi Island, Kedah, and in southern Thailand at Hala-Bala Wildlife Sanctuary, Narathiwat Province ( Fig. 2 ). The holotype of M. lateralis was collected by Major- General Thomas Hardwicke, but its collecting location is unknown, because the label indicates only that it came ‘From the continent’. However, Günther (1864) listed

1242 E. S. H. QUAH ET AL.

it as coming ‘From the mainland’. Major Hardwicke collected in Singapore and Penang Island, and David & Pauwels (2004) narrowed down the type locality of the species to the mainland part of the State of Penang.

Natural history: This is the only known lowland species of Macrocalamus . A specimen from Thailand was collected from hill rainforest at an elevation of ~ 400 m ( David & Pauwels, 2004). However, we now know that the species ranges up to 800 m in elevation at Gunung Raya, Langkawi Island. Specimen LSUHC 11590 was collected during mid-morning, at ~10.00 h, from beneath damp leaf litter along a road cut. Although the Thai specimen was reported to have been found active above the ground during the daytime ( David & Pauwels, 2004), observations of additional specimens on Gunung Raya, Langkawi indicate that this species is also active at night, with specimens having been observed crossing roads after sunset (Tom Charlton in litt., 2015). Nothing is known about the diet, reproductive biology or behaviour of this species. Relationships: Macrocalamus lateralis is most closely related to the new species, M. emas , from which it differs by an uncorrected pairwise sequence divergence of 15.0% (Table 3).

Material examined: Peninsular Malaysia, Kedah, Langkawi Island, Gunung Raya LSUHC 11590.

Figures

Figure 2. Distribution of Collorhabdium williamsoni and Macrocalamus species in the Malay Peninsula. The tree was extracted from the maximum likelihood phylogram in Figure 1. Branch lengths do not represent genetic distance.

Figure 3. Top and middle: dorsum and venter of Macrocalamus lateralis (LSUHC 11590) from Gunung Raya, Langkawi Island, Kedah. Photographs by Evan Quah. Lower left and right: dorsum and venter of Macrocalamus lateralis from Gunung Raya, Langkawi Island, Kedah. Photographs by Tom Charlton.