Ptychozoon nicobarensis, Das, Indraneil, 2009

Das, Indraneil, 2009, New species of Ptychozoon (Sauria: Gekkonidae) from the Nicobar Archipelago, Indian Ocean, Zootaxa 2095, pp. 8-20 : 10-16

Ptychozoon nicobarensis sp. nov.

( Figs. 1–4 )

Ptychozoon kuhli: Tiwari. 1961 . J. Bombay Nat. Hist. Soc. 58: 523.

Ptychozoon kuhli: Biswas & Sanyal. 1977 . Rec. Zool. Surv. India 72: 121. Ptychozoon kuhli: Biswas & Sanyal. 1980 . Rec. Zool. Surv. India 77: 259; 260. Ptychozoon kuhli: Biswas. 1985 . J. Bombay Nat. Hist. Soc. 81: 477. Ptychozoon kuhli: Das. 1994 a. J. Andaman Sci. Assoc. 10 (1 & 2): 46. Ptychozoon kuhli: Das. 1994 b. Hamadryad 19: 21.

Ptychozoon kuhli: Das. 1996 . Biogeogr. reptiles south Asia: 42.

Ptychozoon kuhli: Das. 1997 . Hamadryad 22(1): 35.

Ptychozoon kuhli: Das. 1999 . In: Trop. island herpetofauna: 58; 67.

Ptychozoon kuhli: Das. 2001 . In: Overview threatened herpetofauna south Asia: 22. Ptychozoon kuhli: Pawar & Biswas. 2001 . Asiatic Herpetol. Res. 9: 101. (in part.)

Holotype: ZSI 2603, adult male, from "Nicobars" (= islands of the Nicobar Archipelago, Bay of Bengal, India), Major A. R. Anderson, Indian Medical Service, date of collection unknown, and collection was made presumably in the late 1800s.

Paratypes: ZSI 29885–86, both adult males, Malacca Village, Car Nicobar, 09º10’N; 92º47’E, Bay of Bengal, India; Krishna Kant Tiwari, 28 March 1959 and 2 April 1959, respectively; ZSI 25796–98, three females, Kapanga, Katchall Island, 08º00’N; 93º24’E, Bay of Bengal, India, S. P. Vijayakumar, 15 February 2003, 19 March 2003 and 9 March 2003, respectively; ZSI 25789, male, Deyenshyashe, 08º00’N; 93º29’E, Camorta Island, Bay of Bengal, India, collector as above, 2 January 2003; ZSI 25790, female, Kakana, 08º10’N; 93º31’E, Camorta Island, Bay of Bengal, India, collector as above, 4 January 2003; ZSI 25793, male, Mathai'tha'karu, 08º29’N; 93º37’E, Tillanchong Island, Bay of Bengal, India, collector as above, 1 February 2003; ZSI 25794, female, Chowra Island, 08º27’N; 93º03’E, Bay of Bengal, India, collector as above, 9 March 2003; ZSI 25798, female, Chowra Island, 08º27’N; 93º03’E, Bay of Bengal, India, collector as above, 9 March 2003; ZSI 25796, female, Kapanga, Katchall Island, 08º00’N; 93º24’E, Bay of Bengal, India, collector as above, 15 February 2003; ZSI 25800, female, Mus, 07º56’N; 93º34’E, Nancowry Island, Bay of Bengal, India, collector as above, 14 December 2002; ZSI 25795, male, Forest, 08º00’N; 93º32’E, Nancowry Island, Bay of Bengal, India, collector as above, 7 December 2002; ZSI 25801, female, Bengla, 08º18’N; 93º07’E, Teressa Island, Bay of Bengal, India, collector as above, 30 March 2003; ZSI 25793, male, Mathai'tha'karu, 08º29’N; 93º37’E, Tillanchong Island, Bay of Bengal, India, collector as above, 1 February 2003; ZSI 25791–92, two females, Trinkat, 08º04’N; 93º34’E, Trinkat Island, Bay of Bengal, India, collector as above, 15 January 2003; ZSI 25802, female, Arong, 09º10’N; 92º43’E, Car Nicobar, Bay of Bengal, India, collector as above, 20 September 2003. The type locality is indicated in Fig. 5 .

Diagnosis: A large species of Ptychozoon (reaching SVL 100.3 mm), diagnosable from congeneric species in showing the following combination of characters: dorsum with a tan vertebral stripe, lacking dark transverse bars; supranasals in contact; cutaneous expansions on sides of head; absence of predigital notch in preantebrachial cutaneous expansion; imbricate parachute support scales; four irregular rows of low, rounded enlarged scales on dorsum; 20–29 scales across widest portion of tail terminus; three indistinct chevrons on dorsum; 7–11 pairs of preanal pores; femoral pores absent; tail with an expanded terminal flap and weak lobe fusion at proximal border of tail terminus.

Description of holotype: A large species of Ptychozoon (SVL 87.3 mm); snout short (HL/SVL ratio 0.19), fairly wide (HW/SVL ratio 0.18), depressed (HD/HL ratio 0.63); snout tip tapered; head distinct from neck; lores sloping; interorbital region flat; 16 scales in interorbital region; snout slightly less than twice eye diameter (ED/E-S ratio 0.61); scales on snout and forehead small, rounded, smooth; scales on snout larger than those on occipital region; no keeled, enlarged scales on forehead, except for a few enlarged supraauricular tubercles; eyes large (ED/HL ratio 0.40); orbits of eyes lacking ‘extra-brillar fringes’ (of Underwood, 1954); canthus rostralis prominent; pupil vertically elliptical, with crenelated edges; supraciliaries elongated, lacking spines on anterior of top half of orbit; auditory canal deep; auricular opening oval, with major axis vertically (EL/E-S ratio 0.15), lacking enlarged lobules; eye to ear distance greater than diameter of eyes (E-E/ED ratio 1.13); no ridge of tubercles along mandible; a few scattered tubercles anterior to tympanum; rostral rectangular, partially divided dorsally by an inverted Y-shaped fissure along the short axis of rostral (= rostral groove), which fails to meet anterior of snout (rostral groove running for ca. 25% of rostral depth); rostral less than half as deep as wide (rostral width = 3.7 mm, rostral depth = 2.1 mm; width/ depth ratio 1.76); contacted posteriorly by nostrils and two trapezoidal supranasals in narrow contact ventroposteriorly with supralabial I; nostrils oval, situated within nasals, oriented laterally; nasal in contact with supralabial I; three postnasals bound nasal; two scale rows separate orbit from supralabials; supralabials 11; supralabial IX in midorbital position; infralabials 8, followed by two small scales; mental subtriangular, almost as deep as wide; postmentals paired, rectangular, longer than mental and in contact; posteriorly, each postmental is bounded by one smooth, rounded, juxtaposed scale, postmentals ca. eight times larger than adjacent throat scales; tongue elongate, with a shallow median cleft; enlarged endolymphatic sacs extracranially present on nape.

Body dorsoventrally flattened, relatively stout, somewhat elongate (A-G/SVL ratio 0.43); distinct axillagroin dermal expansion ("flap" or "patagium"), measuring 7.7 mm at midpoint of body, with enlarged, imbricate, rectangular support scales; tubercles on dorsum low, rounded, in four irregular rows; dermal flap on cheek region, measuring 3.5 mm; vertebral scales smallest; smooth, imbricate ventrals in 28 transverse rows; scale size subequal from chin to gular, pectoral and abdominal regions; dorsal scales at midbody much smaller than ventral scales; 28 midventral scale rows, reduced in size laterally in the same row; scales on manus and pes smooth, rounded; scales on inner and outer surfaces of fore- and hind limbs smooth; preanal depression or groove absent; seven pairs of preanal pores in an angular series, lacking diastema; pore-bearing scales enlarged relative to adjacent scales; femoral scales undifferentiated in size, lacking pores.

Forelimbs moderately short, stout; forearm short; hind limbs relatively short; tibia short (TBL/SVL ratio 0.20); predigital notch in preantebrachial cutaneous expansion absent; digits relatively short, laterally compressed, all clawed, except the inner digit; each digit with leaf-like lamellae at tip; a small retractable recurved claw inside digital tip; distal phalanges not elevated; subdigital scansors subrectangular, entire, unnotched; basal subdigital lamellae broad; lamellae numbering on manus I (13); II (15); III (15); IV (15) and V (13) and on pes I (10); II (12); III (12); IV (13) and V (11); interdigital webbing present; relative length of digits (finger): III> II> IV> V> I; (toe): III> IV> V> II> I; limbs covered with uniform, smooth scales; fringe of skin on anterior and posterior edges of fore limbs and posterior of hind limbs and on head, extend from posterior of the angle of jaws to the nape.

Tail (detached) regenerated, flattened, shorter than snout-vent length (TL/SVL ratio 0.16); terminal tail flap broad, measuring 22.5 x 9.7 mm in width; 13 lobules on each side of tail; tail lobes not fused to proximal edge; caudal lobe angling extreme; tail terminus not expanded laterally; postanal hemipeneal bulge distinct; tail distinctly segmented, with 5–8 transverse rows of scales in each tail segment; caudal tubercles do not extend to tail terminus; paired postcloacal spurs, comprising a single rounded, flattened scales; tail lacking distinct lateral furrows; median subcaudal series not transversely enlarged, smooth; scales on postanal region and at proximal part of tail base smaller than on rest of tail.

Colouration: The preserved specimens comprising the type series are dark brown dorsally, with a pale vertebral stripe; paler ventrally. Live specimens are Hair Brown (# 119A) dorsally, with a True Cinnamon (# 139) saddle, which is changeable to Cream Color (# 54) under stress; three indistinct dark chevron-like markings on dorsum, between nuchal and caudal constriction; broad median stripe, from forehead, across body, to beyond base of tail; patagium and dorsal surface of limbs and tail with Hair Brown variegations on a paler background, forming wavy band-like patterns on limbs and digits; a thin Buff (# 124) stripe from posteroventral corner of eyes to angle of jaws; iris showing in photographic images (presumably depending on angle of photography, illumination, and level of stress) from golden yellow to Antique Brown (# 37); tail dark brown, tip of terminus of original tail as well as connection of tail body to tail terminus, covering 2–2.5 cream lobules. Venter cream, undersurfaces of cutaneous expansions Buff Yellow (# 53).

Variation: Details of pholidosis and measurements are in Tables 1 and 2 , respectively. Male SVL ranged between 26.7–89.0 (mean 75.7 ± SE 9.86), female SVL between 79.9–100.3 (mean 92.5 ± SE 1.58). Adult females were significantly larger than adult males (Mann-Whitney U = 6.0, p <0.05), and adult males show both hemipeneal bulge and 7–11 pairs of preanal pores, that were absent in females. Biswas and Sanyal (1980) mentioned that the regenerated tail of a specimen they examined lacked ornamentation.

Etymology: Latin implying an inhabitant of the Nicobar Islands.

Natural history notes: The new species of Ptychozoon was observed and collected from the island of Car Nicobar and the islands of central Nicobars, including Camorta, Nancowry, Tillanchong, Katchall, Trinkat, Tarassa, Chowra and Bompoka. Biswas and Sanyal (1980) reported a specimen from Nancowry Island, but this specimen is at present untraced in the ZSI collection. The data on distribution suggest that the species is restricted to the above nine islands, while absent from the southern group of Nicobar Islands, including Great Nicobar. In the southern group of islands, the species is replaced by its ecological equivalent, Gekko smithii . The occurrence of Ptychozoon nicobarensis sp. nov. exclusively on the central portion of the great chain of Andaman and Nicobar islands that stretch on the eastern portion of the Bay of Bengal, from Achin Head of Myanmar to north of Aceh Province, Sumatra, is enigmatic. On the north of its distributional range, in the Andaman Islands, the species is apparently replaced by Gekko verreauxi . Can the presence of the two Gekko species, one each on the north and south of the distributional range of Ptychozoon nicobarensis sp. nov. account for its idiosyncratic distribution pattern observed? Tiwari (1961), who assigned the Nicobar population to P. kuhli , speculated a waif dispersal to explain its occurrence on the Bay Islands, involving drifting vegetation carrying its eggs from the south-east Asian mainland. Tiwari (1961) provided data on reproduction in this species. Two eggs, measuring 11 x 15 mm, are produced at a time, attached to barks of trees, 45–60 cm above the ground. During the field study, eggs were observed on many occasions, typically laid as pairs (egg-shells fused to each other), attached to the tree trunks. The species appears to show sitefidelity, or perhaps communal nesting, as evidenced by multiple egg-shell scars indicating hatched eggs at the same site on many occasions on various substrates (tree trunks, broken vessel in an abandoned forest hut, concrete walls and abandoned World War II Japanese bunkers).

Data on micro- and meso- habitat use of individuals from nine islands in the Nicobar indicates that the species is essentially nocturnal (82%, n = 45) and arboreal (100%, n = 45). Most (93%, n = 45) individuals were first sighted on tree trunks with an average height of 254.57 cm (± SD = 190.47). Individuals were observed 9–800 cm above substratum. On two occasions, during diurnal searches, individuals were observed roosting under exfoliating tree bark. On Tillanchong Island, an individual was observed on concrete wall inside a human habitation situated amidst primary forest. The circumference of trees on which the individuals were observed varied between 10–370 cm, with a mean of 94.61cm (± SD = 86.83, n = 18). Data on body weight measured from individuals in the field suggest a mean body mass of 13.56 g (± SD = 1.91, n = 16). Individuals were observed in lowland evergreen forests, hill slope evergreen forests, plantations (areca nut, Areca catechu and coconut, Cocos nucifera ), human habitations (huts, Japanese bunkers from the World War II period), disturbed lowland forests. The species' ability to thrive in disturbed habitats suggests its tolerance for anthropogenic structures, as also known for P. horsfieldii , P. kuhli , and P. lionotum (fide Flower, 1896; Pawar and Biswas, 2001; Das, 2004).

Comparisons: The new species from the Nicobars is compared with the six congeneric species, now considered valid (see Rősler, 2000; Kluge, 2001). The absence of a pale vertebral stripe differentiates the new species from all congeners. Additional characters that separate the Nicobarese species are listed below, in the comparison that enumerates only the differential characters.

Ptychozoon horsfieldii Gray, 1827 ( Myanmar, Thailand, Peninsular Malaysia and islands of Sundaland): sharply tapered tail; non-expanded terminal tail flap; femoral pores 8–11; dorsal tubercles absent and smaller maximum body size (SVL range 56.8–73.9 mm); Ptychozoon intermedium Taylor, 1915 (Mindanao and associated islands in the Philippines): 12–19 enlarged femoral scales (vs. absent); 23/23 (vs. 18/18) scalloped tail lobes; 14–18 (vs. 20–29) scales across widest portion of tail terminus; short, non-expanded terminal flap on tail and smaller maximum body size (SVL range 68.6–98.8 mm); Ptychozoon kuhli Stejneger, 1902 (southern Thailand, Peninsular Malaysia and the islands of the Grater Sundas): dorsum typically with dark transverse bands; 42–51 (vs. 20–29) scales across widest portion of tail terminus; dorsal tubercles in straight (vs. irregular) rows; caudal tubercles continue to tail terminus (vs. separate); tail ornamentation enters (vs. fails to enter) tail terminus and caudal lobe angling slight (vs. extreme); Ptychozoon lionotum Annandale, 1905 ( Myanmar, Thailand, Cambodia and Peninsular Malaysia): tail flap partially denticulate; lobe fusion at proximal border; convex tubercles on dorsum absent; predigital notch in preantebrachial expansion present (vs. absent) and supranasals not in contact; Ptychozoon rhacophorus Boulenger, 1899 (Gunung Kinabalu, in Sabah, East Malaysia; Borneo): a small species (SVL to 64.5 mm); sharp tapering tail; terminal tail-flap absent; spinose tubercles on dorsum; dorsum lacking dark bands; supranasals not in contact; absence of cutaneous expansion on sides of head and smaller maximum body size (SVL range 58.8–64.5 mm) and Ptychozoon trinotaterra Brown, 1999 (southern Thailand and central Vietnam): single paravertebral series of dorsal tubercles (sometimes absent); dorsal tubercles, when present, flattened and smaller maximum body size (SVL range 70.5–71.3 mm).

Figures

FIGURE 1. Dorsal view of holotype of Ptychozoon nicobarensis sp. nov. (ZSI 2603).

FIGURE 2. Holotype of Ptychozoon nicobarensis sp. nov. (ZSI 2603), showing head in lateral (A), dorsal (B) and ventral (C) views.

FIGURE 3. Dorsal view of tail of holotype of Ptychozoon nicobarensis sp. nov. (ZSI 2603).

FIGURE 4. A live paratype of Ptychozoon nicobarensis sp. nov. (ZSI 25800), from Nancowry Island, Nicobar Archipelago, India, showing colouration.

FIGURE 5. Maps of (bottom left) the landmasses north of the Indian Ocean, indicating location of the archipelago system of the Nicobars, to the north-east, and (top right), the type localities of Ptychozoon nicobarensis sp. nov.

Tables

TABLE 1. Meristic data (squamation and pores) on type series of Ptychozoon nicobarensis sp. nov. Abbreviations: + = present; - = absent; M = male; SL = supralabial; IL = infralabial; IO = interorbital; T 4 = lamellae under Toe IV of pes; MV = midventral; PP = preanal pores; and TSF = transverse scales along original caudal flap (L / R).

	ZSI 2603	ZSI 20885	ZSI 29886	ZSI 25789	ZSI 25790	ZSI 25791	ZSI 25792	ZSI 25793	ZSI 25794
sex SL (MO)	male 11	male 11	male 11	male 12	female 12	female 12	female 11	male 11	female 12
IL	9	11	11	10	12	9	11	9	11
IO T4	16 21	16 18	14 20	10 13	9 15	9 15	- 13	8 14	11 15
MV	28	30	31	31	28	-	26	30	25
PP TSF	7/7 -	9/11 -	10/11 -	9/8 20/23	- 22/26	- 24/23	- -	9/8 -	- -

TABLE 2. Mensural data (in mm) of type series of Ptychozoon nicobarensis sp. nov. Abbreviations: SVL = snout-vent length; TL = original tail length; FA = forearm length; TBL = tibia length; A-G = axilla to groin distance; HL = head length; HW = head width; HD = head depth; ED = eye diameter; E-E = eye to ear distance; E-S = eye to snout distance; E-N = eye to nostril distance; IO = interorbital distance; EL = ear length; and IN = internarial distance. In addition, - = missing data (detached or unpreserved tails); and * = regenerated tails.

	ZSI 2603 ZSI 20885	ZSI 29886	ZSI 25789	ZSI 25790	ZSI 25791	ZSI 25792	ZSI 25793	ZSI 25794
sex	male male	male	male	female	female	female	male	female
SVL	87.3 83.7	26.7	86.6	90.7	89.0	96.8	89.0	100.3
TL	14.0* -	-	78.0	82.0	85.4	81.0	53.8*	54.0*
TL/SVL%	16.1 -	-	90.1	90.4	95.9	83.7	60.4	53.8
TW	10.1 11.3	9.4	10.8	7.8	8.1	10.2	10.1	8.8
BW	13.7 18.1	16.3	15.5	13.2	16.2	14.2	17.6	17.3
FA	9.6 10.0	13.4	10.5	10.7	11.3	10.9	11.1	11.2
TBL	17.5 15.4	16.3	14.0	13.0	13.3	13.6	13.8	14.4
A-G	37.6 38.8	39.3	40.1	42.2	42.0	46.3	40.0	47.1
HL	17.0 16.7	16.0	15.2	16.9	15.3	17.2	15.5	18.1
HW	15.8 16.1	15.6	16.6	17.3	17.1	18.0	17.9	20.3
HD	10.7 9.2	10.5	10.2	10.6	10.1	10.6	11.0	11.6
ED	6.8 5.2	5.9	5.3	7.1	6.3	6.6	6.1	6.9
E-E	7.7 6.9	8.3	7.4	7.3	7.3	7.6	7.6	8.4
E-S	11.2 12.0	10.6	11.1	10.8	10.8	11.9	10.6	12.1
E-N	7.2 9.0	7.8	8.3	8.4	8.3	8.4	8.0	8.8
IO	9.8 9.0	8.6	10.6	8.8	8.4	10.1	10.4	10.1
EL	1.3 1.3	1.4	2.5	2.1	2.5	2.3	2.9	3.0
IN	2.5 3.7	3.5	3.3	3.7	3.5	3.5	3.8	4.0