Gekko (Ptychozoon) nicobarensis ( Das and Vijayakumar, 2009 )

Chandramouli, S. R., Gokulakrishnan, G., Sivaperuman, C. & Grismer, L. Lee, 2021, A new species of the genus Gekko Laurenti, 1768 (Squamata: Gekkonidae) from the Nicobar Archipelago, with an overview of congeners from the Andaman and Nicobar Islands, Amphibian & Reptile Conservation (e 276) 15 (1), pp. 108-125 : 114-116

Gekko (Ptychozoon) nicobarensis ( Das and Vijayakumar, 2009) ( Figs. 5–6 )

Ptychozoon homalocephalum – Steindachner (1867)

Ptychozoon kuhli – Stoliczka (1870); Smith (1935); Biswas and Sanyal (1977); Das (1999) part

Holotype. ZSI 2603 , an adult male collected by A. R. Anderson from ‘Nicobars’ in the late 1800s.

Material studied. DOSMB05102 from Chuckchuka (9.2161ºN, 92.8109ºE, 14 m asl), Car Nicobar , ZSI / ANRC / T/5234 from Kalasi (8.2803°N, 93.1173°E), Teressa , and ZSI / ANRC / T/4235 from Chota Enaka (8.0657°N, 93.5428°E, 39 m asl), Camorta , Nicobar Islands .

Diagnosis. A medium to large-bodied ( SVL 78.2–95.8 mm) species of Gekko , characterized by: presence of extensive, membranous skin flaps along the sides of the head, trunk, and tail; tail tip with an oval shaped skin flap; presence of 10–13 supralabials; 10 or 11 infralabials; two relatively small, elongate inner pairs of postmentals in broad medial contact with each other; three smaller, separated outer pairs of postmentals; 20–21 precloacal pores in males, no femoral pores; two internasals in contact with or separated by one or two small azygous scales; no ventrolateral body folds; 29–32 transverse, juxtaposed rows of ventrals; four well-spaced, transverse rows of enlarged, rounded dorsal tubercles; one enlarged post-cloacal spur on each side of the vent; 13–21 undivided subdigital lamellae on toe IV; dorsal color pattern consisting of four or five legible, dark, W-shaped, transverse bands or a light-colored vertebral stripe bounded on either side by two darker stripes, and a creamy white to light-brown venter.

Description and variation. A medium to large-bodied species of Gekko belonging to the subgenus Ptychozoon measuring 78.42–95.86 mm SVL, head large (mean HL: SVL 0.28), much longer than broad (mean HL: HW 1.34) with a blunt, rounded snout tip. Eyes protruding, fairly large (mean ED:HL 0.25) with a vertically elliptical pupil; eye nearly half as long as the snout (mean ED: ES 0.53); nostrils situated closer to the snout tip than to the eyes (mean EN: ES 0.77). Trunk much shorter than one-half the length of the body (mean AG: SVL 0.47). Overall habitus depressed. Supralabials 10–13 and infralabials 10–11 on each side; two moderately enlarged postmentals in broad medial contact, followed by three pairs of scales that are nearly as large as the postmentals. Dorsum bearing four transverse rows of weakly enlarged, rather indistinct tubercles. Ventrals imbricate, in 29–32 transverse rows. Sides of the body bearing a membranous flap of skin, with enlarged, rhomboidal, imbricate scales. A pair of enlarged, rounded cloacal spurs present at the base of the vent. Subcaudals not elongated horizontally, the middle row slightly enlarged. Tail with serrated dermal membranes extending along the sides, forming an oval-shaped disc at the terminus. Tail tip regenerated. Upper arm shorter than lower arm (mean UAL: LAL 0.91); palm enlarged with five fingers; the first one with an indistinct claw; relative lengths of fingers IV> III > V >II>I. Sides of upper and lower arms with extensive skin flaps. Thighs short (mean FEL: SVL 0.18) robust; with a few tuberculated scales on the dorsal surface. Tibia shorter than thighs (mean TBL: SVL 0.16); toes with entire, undivided subdigital lamellae, 14–20 under toe IV; relative lengths of toes IV> III > V >II>I. Tibia bearing lateral flaps of skin. Fingers and toes extensively webbed with membranous skin flaps extending from the base to the tip. Males have a series of 20–21 precloacal pores and lack femoral pores.

Coloration in life. Dorsal coloration variable. Two distinct morphs recorded. One morph with a series of five or six darker brown ‘W’ shaped transverse bands on the body and five or six similar transverse bands on the tail. The other morph with a bright tan vertebral stripe bordered by darker flanks ( Fig. 5 ). Venter uniform brown and lacking any specific pattern. Eyes with vertically elliptical pupils, a greenish yellow iris and brown reticulations.

Distribution. Occurs on islands of the Northern and central group of the Nicobar Archipelago. Recorded from Car Nicobar, Camorta, Katchall, and Teressa Islands during this study. It has been reported from Chowra, Bompoka, Trinkat, and Nancowry Islands ( Das and Vijayakumar 2009) ( Fig. 10 ).

Natural history. Nocturnal in habit. The individuals recorded during this study were observed mostly at a height of approximately 2–2.5 m above the ground on the trunks of relatively short shrubs that were nearly 3–3.5 m tall, with a girth not exceeding 25 cm. Found in primary evergreen forests, also recorded from secondary forests, human habitations, and plantations. Calls of this species could not be heard during the sampling sessions in the field. Pairs of eggs stuck to each other and the tree bark substrate were seen in July.

Remarks. The holotype has 11 supralabials (10–13 in our material), 9 infralabials (10–11), four rows of dorsal tubercles at midbody (4), and 21 subdigital lamellae (14– 19) under toe IV.

Figures

Fig. 5. Gekko (Ptychozoon) nicobarensis in life from Car Nicobar (above: banded; middle: striped morphs).

Fig. 6. Dorsal, lateral, and ventral views of the head and ventral view of the feet of Gekko nicobarensis (DOSMB05102).

Fig. 10. Map of the Andaman and Nicobar Islands showing the distributions of Gekko verreauxi (red), Gekko nicobarensis (yellow), and Gekko stoliczkai sp. nov. (black).