Hemidactylus vanam, Chaitanya & Lajmi & Giri, 2018

Chaitanya, R., Lajmi, Aparna & Giri, Varad B., 2018, A new cryptic, rupicolous species of Hemidactylus Oken, 1817 (Squamata: Gekkonidae) from Meghamalai, Tamil Nadu, India, Zootaxa 4374 (1), pp. 49-70 : 51-58

Hemidactylus vanam sp.nov.

Figs. 1–10

Hemidactylus maculatus Bhupathy & Sathishkumar 2012

Holotype. NCBS-AU158 , adult male; collected en-route to the High Wavy Mountains , Tamil Nadu, India (9.7808°N; 77.4427°E, 610 m asl) on 21 November 2016. Collected by R. Chaitanya, Akshay Khandekar and Vanasundara Pandian.

Paratypes. NCBS-AU159, sub-adult female, NCBS-AU160, NCBS-AU161, adult females; ESV106, ESV107, adult males, ESV108, adult female; BNHS 2328 sub-adult female, BNHS 2329 adult female; ZSI/ WGRC /IR/V.NO 2634, adult male, ZSI/ WGRC /IR/V.NO 2635, adult female. Collection data same as holotype. ZSI/ WGRC /IR/V.NO 2635, collected near Suruli falls, Theni district (9.6563° N; 77.3061° E, 430 m asl) .

Diagnosis. A large sized Hemidactylus , SVL averaging 88.24 ± 16 mm to a maximum of at least 112.2 mm (n=9). Dorsal pholidosis heterogeneous, composed of roughly circular, striated, granular scales intermixed with much enlarged, fairly regularly arranged longitudinal rows of 17–19 strongly keeled, striated tubercles that are heterogeneous in shape and size, extending from occipital region to tail ( Fig. 1 ); enlarged tubercles on the two most medial parasagittal rows are small, flat, strongly keeled and rounded gradually increasing in size and becoming conical towards flanks, last two to three rows on flanks are smaller and strongly conical. Two well-developed pairs of postmentals, inner pair much larger than the outer and in broad contact with each other behind the mental. Ventrolateral folds distinct. About 34–40 scale rows across the venter. All digits with enlarged scansors, lamellae in straight transverse series, all divided except the apical and a few basal that are undivided, 10–12 (manus and pes) lamellae beneath fourth digit and 9–10 (manus) and 8–9 (pes) beneath first digit. Femoral pores on each side 17– 22, separated by 10–11 poreless scales in males. Dorsal coloration pale-brown with transversely arranged saddleshaped markings running from the occiput to the sacrum that are of a darker shade.

The large size (up to 112.2 mm SVL) of Hemidactylus vanam sp. nov. can be used to easily diagnose it from most other congeners from the Indian subcontinent and Southeast Asia, including H. garnotii Duméril & Bibron , H. platyurus (Schneider) , H. aquilonius McMahan & Zug , H. scabriceps (Annandale) , H. imbricatus Bauer, Giri, Greenbaum, Jackman, Dharne & Shouche , H. gracilis Blanford , H. reticulatus Beddome , H. albofasciatus Grandison & Soman , H. sataraensis Giri & Bauer, H. brookii Gray , H. gujaratensis Giri, Bauer, Vyas & Patil , H. frenatus Schlegel , H. persicus Anderson , H. robustus Heyden , H. parvimaculatus Deraniyagala , H. treutleri Mahony , H. gleadowi Murray , H. kushmorensis Murray , H. murrayi Gleadow , H. chipkali Mirza & Raju , H. triedrus (Daudin) , H. subtriedrus Jerdon , H. lankae Deraniyagala , H. depressus Gray , H. pieresii Kelaart , H. leschenaultii Duméril & Bibron , and H. flaviviridis Rüppel all of which reach maximum sizes of up to 90 mm SVL.

Hemidactylus vanam sp. nov. shares its large adult size (adult SVL upto 112.2 mm) only with H. giganteus Stoliczka , H. aaronbaueri Giri , H. yajurvedi Murthy, Bauer, Agarwal, Lajmi & Giri , H. hemchandrai Dandge & Tiple , H. prashadi Smith, H. hunae Deraniyagala , H. graniticolus Agarwal, Giri & Bauer, H. maculatus Duméril & Bibron , H. acanthopholis , H. kangerensis Mirza, Bhosale & Patil and H. sushilduttai Giri, Bauer, Mohapatra, Srinivasulu & Agarwal. Hemidactylus giganteus differs from H. vanam sp. nov. in the complete absence of enlarged dorsal tubercles while H. aaronbaueri , H. yajurvedi and H. hemachandrai have slightly enlarged, rounded, weakly-keeled tubercles at midbody. Hemidactylus prashadi , H. hunae , H. graniticolus H. kangerensis and H. sushilduttai differ from the new species in dorsal pholidosis, number of femoral pores and the number of poreless scales separating them (differing character states indicated in parenthesis): Hemidactylus prashadi (weakly keeled, sub-trihedral, slightly enlarged dorsal tubercles arranged in 14–16 rows; 17–20 femoral pores separated by 3 poreless scales), H. hunae (keeled, sub-trihedral, slightly enlarged dorsal tubercles arranged in 16– 20 rows; 22–24 femoral pores separated by 3–6 poreless scales), H. graniticolus (keeled, sub-trihedral, slightly enlarged dorsal tubercles arranged in 16–18 rows; 23–28 femoral pores separated by 1–3 poreless scales), H. kangerensis (keeled, trihedral, enlarged dorsal tubercles arranged in 18–20 rows; 18–21 femoral pores separated by four poreless scales), H. sushilduttai (keeled, trihedral, enlarged dorsal tubercles arranged in 16–17 rows; 19–24 femoral pores separated by four poreless scales.

Based on size, dorsal pholidosis and general colouration, Hemidactylus vanam sp. nov. is most similar to H. maculatus and H. acanthopholis but can be diagnosed on the basis of the following combination of characters: dorsal pholidosis, femoral pores and the number of poreless scales separating them (differing character states indicated in parenthesis): H. maculatus (enlarged tubercles trihedral throughout, parasagittal rows slightly smaller; 16–19 femoral pores separated by 5–9 poreless scales), H. acanthopholis (enlarged tubercles trihedral, parasagittal rows slightly smaller, last few rows on flanks, slightly conical; 19–21 femoral pores separated by 13–14 poreless scales) ( Fig. 6 ). Additionally, H. vanam sp. nov. can be diagnosed from H. maculatus and H. acanthopholis by the presence of a dense aggregation of enlarged, strongly conical, striated tubercles on dorsal aspect of thigh (enlarged tubercles on dorsal aspect of thigh sparse in H. maculatus and H. acanthopholis ) ( Fig. 3 ).

Description. The holotype is in good condition except for loss of skin on a small triangular patch on the neck, body is dorsoventrally flattened, ventrolateral fold is more pronounced on the left, and second toe on right pes curved upwards—all artefacts of preservation. Tail is regenerated and slightly curved towards the left. Hemipenes everted, exposed and seen on both sides when viewed dorsally ( Fig. 1 ). Adult male, SVL 108.8 mm. Head short (HL/SVL ratio 0.27), slightly elongate (HW/HL ratio 0.76), not strongly depressed (HH/HL ratio 0.46), distinct from neck ( Fig. 4 ). Loreal region slightly inflated, canthus rostralis indistinct ( Fig. 4B ). Snout short (SE/HL ratio 0.40); longer than eye diameter (OD/SE ratio 0.61); scales on snout, canthus rostralis, forehead and inter-orbital region heterogenous, mostly granular and rounded; scales on the snout and canthus rostralis much larger than those on occipital, forehead and inter-orbital regions ( Fig. 4A ). Eye small (OD/HL ratio 0.24); pupil vertical with crenulated margins; supraciliaries small, mucronate, gradually increasing in size towards front of the orbit, those at the anterior end of orbit larger. Ear opening roughly elliptical (greatest diameter 3.2 mm); eye to ear distance slightly greater than diameter of eye (EE/OD ratio 1.8). Rostral wider than deep (RL/RW ratio 0.65), incompletely divided dorsally by a weakly developed rostral groove; two internasals, enlarged and separated by a single scale of similar size; one supranasal on each side, much smaller than internasals; three diminutive postnasals on each side; rostral in contact with nostril, supralabial I, internasals and the small scale separating the internasals; nostrils small (0.8 mm), oval shaped; nasal surrounded by supranasal, internasal, rostral, supralabial I and three postnasals on either side; 6–7 rows of scales separate orbit from supralabials. Mental triangular; two well-developed postmentals, the inner pair slightly shorter (4.2 mm) than the mental (4.3 mm), and in strong contact with each other (1.6 mm) behind mental, outer pair smaller (2.4 mm) than the inner pair and separated from each other by inner pair ( Fig. 4C ). Inner postmental bordered by mental, infralabial I and II, outer postmental and five small gular scales each; outer postmental bordered by infralabial II and III (barely touching), inner postmental, and 6 (right)—7(left) gular scales increasing in size laterally, outer-most of which is much enlarged and continues as a single row of enlarged scales below the infralabials. Infralabials bordered by a single row of enlarged scales; 2 to 3 rows of scales below infralabials IV to VIII are enlarged and weakly imbricate. Supralabials (to midorbital position) 8 (right)—9 (left); supralabials (to angle of jaw) 13 (right)—13 (left); infralabials (to angle of jaw) 10 (right)—10 (left).

Body relatively stout, not elongate (TRL/SVL ratio 0.41), ventrolateral folds indistinct. Dorsal pholidosis heterogeneous, composed of roughly circular, striated, granular scales intermixed with enlarged, fairly regularly arranged longitudinal rows of 17–18 strongly keeled, striated tubercles, extending from occipital region to tail that are heterogeneous in shape and size; enlarged tubercles on the two most medial parasagittal rows smaller, flatter and more rounded, increasing in size and becoming conical at the flanks; the last two rows on flanks slightly larger than the medial parasagittal rows and strongly conical; each enlarged tubercle surrounded by a rosette of 13–16 small granules with 1–5 granules between two longitudinally adjacent enlarged tubercles; enlarged tubercles on nape, shoulder, smaller and pointed, those on occipital, temporal region still smaller. Ventral scales larger than dorsal granular scales, smooth, imbricate, slightly larger on precloacal and femoral region than on chest and abdominal region; midbody scale rows across belly 36–39; gular region with much smaller, juxtaposed scales, anterior gular scales being slightly larger than the rest. Scales on palm and sole smooth; on palm sub-imbricate, rounded and those on sole imbricate and weakly pointed; scales on dorsal aspect of upper arm much larger than granules on dorsum, sub-imbricate and weakly keeled; dorsal aspect of forearm with smaller, striated, granular scales, intermixed with a few enlarged, striated, conical tubercles; scales on dorsal part of thigh and shank circular, striated, intermixed with enlarged, striated, conical tubercles, which are larger on thigh compared to shank; anterior aspect of thigh with flatter tubercles; posterior aspect with a congregation of enlarged, strongly conical, striated tubercles.

Fore and hind limbs relatively short, stout; forearm short (FL/SVL ratio 0.10); tibia short (CL/SVL ratio 0.20); digits moderately short, strongly clawed; all digits of manus and digits I–IV of pes indistinctly webbed; terminal phalanx of all digits curved, arising angularly from distal portion of expanded lamellar pad, half or more than half as long as associated toepad; scansors beneath each toe in a straight transverse series, divided except for distal and three to four basal scansors on digit I and one or two in other digits: 10-11-11-11-10 (left manus), 10-11-11-11-11 (right manus) ( Fig. 5A ), 9-11-11-11-10 (left pes), 9-11-11-12-12 (right pes) ( Fig. 5 B ). Relative length of digits (measurements in mm in parentheses): III (7.1)> IV (6.8) = V (6.8)> II (6.7)> I (5.8) (left manus); II (7.4)> III (7.3)> V (6.9)> IV (7.2)> I (5.8) (left pes).

Tail with first segment intact, rest regenerated, depressed, flat beneath, verticillate with a distinct median furrow; length of the partially regenerated tail less than snout-vent length (TL/SVL ratio 0.76); first segment of tail covered above with small granules that are heterogeneous in shape and size, juxtaposed, striated, interspersed with 11 enlarged, rounded, strongly keeled, striated, posteriorly pointed and flattened tubercles; subcaudal scales on first tail segment larger, imbricate, weakly pointed. Nineteen femoral pores on the left and 21on the right separated medially by a diastema of 10 poreless scales ( Fig. 6 ).

Colouration (in preservative). Dorsum uniformly grayish-brown interspersed with slightly darker blotches in the snout, forehead and mid-vertebral regions ( Fig. 1 ). Darker blotches on dorsal aspect of forelimb and hindlimb. Mid-vertebral tubercle rows mostly dark brown, those on flanks a lighter shade of brown. Crown of head with scattered vague dark-brown markings. Anterior supralabials dark-brown, getting paler towards the posterior.

Infralabials uniformly mid-brown. Limbs mid-brown, with vague irregular dark markings that are more distinct on the forelimbs than the hind limbs, alternating pale and dark interspaces distally, especially on metapodial segments. First segment of original tail grayish-brown, interspersed with vague darker markings on the tubercles. Regenerated portion of tail, a lighter shade of gray interspersed with inconsistent darker markings. Venter cream with scattered patches of diffusely pigmented scales on head. A darker patch of scales in the chest region which is brownish-red spreads onto the forearms; palms and soles grayish. Ventral surface of tail pale, with scattered midbrown speckling throughout.

Colouration (in life) (based on photographs of an uncollected topotype)

Dorsal markings are much more evident in life ( Fig. 7 ). Dorsum pale-brown with no distinct vertebral stripe. Head dorsum pale-brown with a mottling of white and darker-brown spots in the forehead region. Snout light brown, with a scattering of white blotches. A coffee coloured, roughly L-shaped stripe runs from the post orbital region to the forelimb insertion. Four saddle-shaped markings running from the occiput to the sacrum are a darker shade of brown. Interspaces between saddles are similar in colouration to the rest of the dorsum. Most tubercles on the saddle-shaped markings, of a much darker shade of brown than the rest of the body. Tail distinctly banded, with alternating light and dark bands similar to trunk dorsum; darker bands slightly wider than pale bands on tail. Mottled pattern on limb bases with distinct banding distally. Iris marbled, light olive-green, suffused with prominent rust-brown venation; pupil black with crenulated margins that are a lighter shade of olive-green.

Etymology. The specific epithet is a noun in apposition honouring Vanam (pronounced vʌnʌm), a nongovernmental organization based in Theni District, Tamil Nadu, India, for carrying out exemplary conservation work in the region. Their unwavering support has been vitally important to our work in the Meghamalai Wildlife Sanctuary.

Suggested Common Name. Meghamalai Rock Gecko

Variation and additional information from type series. Mensural data for the type series and additional material is given in Table 1. There are seven females and four males, ranging in size from 61.4 mm to at least 112.2 mm. Males have a series of 17–22 femoral pores separated medially by 10–11 poreless scales (ESV106—20/20 pores on left/right side separated by 11 poreless scales, ZSI/WGRC/IR/V.NO 2634—20/22 pores on left/right side separated by 11 poreless scales, ESV107—17/21 pores on left/right side separated by 11 poreless scales). All paratypes resemble the holotype in most of the morphological characters except as follows: Tail entire in paratypes ESV107 and NCBS-AU159, broken or regenerated in all other paratypes; enlarged dorsal tubercles in 17–19 rows; range of supralabials is from 11–15 (9–11 below eye) and infralabials from 10–14. The scales across belly range from 34–40 in paratypes.

Phylogenetic relationships. Hemidactylus vanam sp. nov. is nested within the H. prashadi group of the Indian radiation. It is sister to the recently described species H. acanthopholis ( Fig. 8 ) with a high posterior probability and bootstrap value. H. vanam sp. nov. is genetically distinct from H. acanthopholis and H. maculatus , its two closest congeners, with an uncorrected p-distance of 0.19 each from the cytb dataset.

Distribution and habitat. The following southern tropical forest types are identified in Meghamalai as per the working plan of the Tamil Nadu Forest Department: west coast semi-evergreen forests, moist mixed deciduous forests, secondary moist mixed deciduous forests, dry mixed deciduous forests, carnatic umbrella thorn forests and dry deciduous scrub forests (Bhupathy & Babu 2013). The type-series of Hemidactylus vanam sp. nov. was collected en route to the High Wavy Mountains ( Fig. 10 ) and from near Suruli falls both within the Meghamalai Wildlife Sanctuary, where the habitat chiefly constitutes southern tropical dry mixed deciduous forests with progressions of large charnockite rock formations abutting them (Palanivelu et al. 1998). These habitats are at an altitude of 400–600 m asl and receive an average annual rainfall of 1500 mm (Bhupathy et al. 2009). Similar habitats are seen in the Vellimalai range within the Meghamalai Wildlife Sanctuary and in many parts of the Srivilliputtur Grizzled Squirrel Wildlife Sanctuary, where these geckos could also possibly occur.

Natural history. Hemidactylus vanam sp. nov. appears to be predominantly rupicolous ( Fig. 9 ) and is occasionally found on the higher branches of trees that surround rocky boulders. These strictly nocturnal geckos are seen occupying rock crevices during the day when they are easily disturbed by human presence. They seem less perturbed during the night when they actively forage on rock boulders. Juveniles and adults are syntopic. Most individuals observed had a regenerated tail. They also seem to readily slough their scales when captured, a defence strategy employed by other geckos and an exaggerated version of which was more recently described in Geckolepis megalepis from northern Madagascar ( Scherz et al. 2017). Hemidactylus vanam sp. nov. is found in sympatry with Psammophilus cf. dorsalis , Cnemaspis sp. and Hemidactylus cf. triedrus .

Conservation concerns. The landscape at the type locality is highly affected by anthropogenic factors. In some parts, large portions of these rock faces, the preferred niche for these geckos, have been carved out in an effort to widen the approach road to the High Wavys hill station, which is a popular tourist destination. The first author (RC) observes that these geckos were commonly seen in their habitat in November 2014, and that sightings of the same population had reduced in November 2016.

Figures

FIGURE 1. Dorsal view of holotype (NCBS-AU158, adult male) of Hemidactylus vanam sp. nov. Scale bar = 10mm.

FIGURE2. Details of dorsalpholidosis showingarrangement ofenlarged tubercles.A) Hemidactylus vanamsp. nov. holotype (NCBS-AU158), B) H.acanthopholis holotype(BMNH 1946.8.23.77), C) H.maculatus (BNHS 1836).

FIGURE 3. Posterior aspect of thigh showing dense congregation of tubercles.A) Hemidactylus vanam sp. nov. holotype (NCBS-AU158), B) H.maculatus (BNHS 1836).

FIGURE 4. Head of Hemidactylus vanam sp. nov. holotype (NCBS-AU158). A) Dorsal view, B) Lateral view, C) Ventral view.Scale bar = 5 mm.

FIGURE 5. A) Ventral view of right manus of Hemidactylus vanam sp. nov. holotype (NCBS-AU158), B) Ventral view of right pes Hemidactylus vanam sp. nov. holotype (NCBS-AU158). Scale bar = 5 mm.

FIGURE 6. Precloacal region of adult male Hemidactylus vanam sp. nov. holotype (NCBS-AU158) showing a series of 19 femoral pores on left and 21 on right side separated mesially byten unpored/poreless scales.Scale bar = 10 mm.

FIGURE 7. Photo in life of Hemidactylus vanam sp. nov. paratype (NCBS-AU159).

FIGURE 8. Maximum likelihood phylogeny of South Asian Hemidactylus (Bauer et al. 2010) showing the position of Hemidactylus vanam sp. nov. within the Hemidactylus prashadi group. Other clades are collapsed, numbers at nodes represent support values (bootstrap/posterior probability).

FIGURE 9. Type locality of holotype of Hemidactylus vanam sp. nov. en route to the High Wavy Mountains, Meghmalai WildlifeSanctuary, Tamil Nadu, India.

FIGURE 10. Type localities of all large bodied Hemidactylus spp. from India and Srilanka including that of Hemidactylus vanam sp. nov. in the Meghmalai Wildlife Sanctuary.Star indicates type locality of Hemidactylus vanam sp. nov.