Cyrtodactylus siangensis Boruah, Narayanan, Aravind, Deepak & Das 2024, sp. nov.
Creators: name: Boruah, Bitupan
name: Narayanan, Surya
name: Aravind, Neelavar Ananthram
name: Lalronunga, Samuel
name: Deepak, V.
name: Das, Abhijit
Publisher: name: Zenodo
Year: 2024
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Squamata
Gekkonidae
Cyrtodactylus
Cyrtodactylus siangensis

description: Cyrtodactylus siangensis Boruah, Narayanan, Aravind, Deepak & Das sp. nov.
Figure 9; Tables 2, S 2
Holotype.
Adult female (WII-ADR 1177; Fig. 9 A, B, E – I), from Kalek stream (28.1711 ° N; 95.2420 ° E, elevation 210 m a. s. l.; Fig. 3 A); 1.8 km (aerial distance) northwest from Bodak village, East Siang District, Arunachal Pradesh, India collected by Bitupan Boruah on 23 October 2021.
Paratypes.
Two adult females (WII-ADR 1581 and WII-ADR 1582; Fig. 9 C, D) from a hill slope near Kalek stream, East Siang District, Arunachal Pradesh, India collected by Bitupan Boruah on 15 June 2022.
Diagnosis.
Medium-sized gecko (SVL 70.1–72.1 mm in females); males unknown; supralabials 8–12 and infralabials 9–12; tubercles on dorsum weakly keeled and bluntly conical, 26–32 paravertebral tubercles between the level of axilla and level of groin; 15 or 16 dorsal tubercle rows at mid body; 40–45 mid ventral scale rows; 8–10 small precloacal pores in a continuous series; 13–17 subdigital lamellae on finger IV and 14–19 subdigital lamellae on toe IV; six or seven irregular and broken dark-brown bands on dorsum between the level of axilla and level of groin, or irregular dark-brown reticulation on dorsum.
Description of the holotype.
Holotype well preserved except an incision below left axilla ventrolaterally. Snout-vent length 72.1 mm. Head moderately large (HL / SVL = 0.26), dorsoventrally depressed, longer than width (HW / HL = 0.72), distinct from neck, broader at occipital region; snout rounded in both dorsal and lateral view; loreal region convex; canthus rostralis rounded, indistinct; interorbital space flat, a longitudinal furrow on dorsal surface of the snout, snout short (SO / HL = 0.39), longer than orbit (OD / SO = 0.73); nostril nearly rounded, opening directed posterolaterally; ear opening oval and oblique; scales on head heterogeneous, largest on snout and loreal region, posteriorly smaller in upper eyelid, interorbital space and occipital region, granular juxtaposed; scales on upper eyelids heterogeneous; supraciliaries outwardly sharp giving serrated appearance in dorsal view, size anteriorly and posteriorly decreases, largest at approximately anterior one third of it; rostral wide, a short groove at the middle on top, rostral connected with nasals, supranasals, an internasal and first supralabials; a single scale between the supranasals, larger than the rest of the granular snout scales; granular scales at parietal region and occipital region intermixed with slightly large rounded granular tubercles, dense in occipital and temporal region and size increases towards nape; supralabial eight on right and 11 on left side, supralabials upto midorbit seven on right and eight on left side, size decreases towards angle of jaw; a series of scales nearly rounded, granular and slightly larger than the loreal scales present above the supralabials; mental as wide as rostral, triangular, connected with first infralabials, inner postmentals; 10 infralabials on right and nine on left side, size decreases towards angle of jaw, first infralabials connected with mental, second infralabial, inner and outer postmentals; inner pair of postmentals are larger than the outer postmentals, posterior margin of the inner postmentals bordered by eight granular scales of different size; one or two rows of enlarged scales along the infralabials starting below the outer postmentals, posteriorly size of those decreases, elongated and narrow; rest of the gular scales are small, granular juxtaposed, homogeneous, size increases towards throat where they become imbricate.
Habitus slender (BW / SVL = 0.18, TRL / SVL = 0.45), dorsoventrally depressed; dorsal scales granular, rounded, heterogeneous, intermixed with rounded, weakly keeled and bluntly conical tubercles irregularly arranged, starting from occipital region to fourth segment of the tail, size increases towards posterior body, pronounced at sacrum and base of the tail; 15 dorsal tubercles across mid dorsum; 26 paravertebral tubercles; ventrolateral fold weak; ventral scales larger than those of dorsal, flat, smooth, cycloid subimbricate to imbricate, largest on belly; 40 mid-ventral scales between ventrolateral fold; very small, 10 precloacal pores arranged in an inverted “ V ” shaped continuous series, followed by 7 unpored, large scales below it, largest at the apex.
Forelimbs and hindlimbs slender (FL / SVL = 0.14, CL / SVL = 0.17); digits strongly inflected at the joints, all bearing large recurved claw, enlarged subdigital lamellae, lamellae beneath digit IV of right and left manus (given as basal + distal) is 6 + 11 and 6 + 10 respectively, the second most lower lamellae of the basal series of digit IV of both sides are divided (not included in lamellar count); lamellae beneath digit IV of right and left pes (given as basal + distal) is 7 + 11 and 6 + 10 respectively; dorsal scales on forelimbs heterogeneous, granular juxtaposed, smooth and subimbricate at distal end of forearm; forearm intermixed with a few rounded, large tubercles; dorsal scales of hindlimbs granular intermixed with large, rounded, bluntly conical tubercles; scales on thigh towards knee smooth subimbricate; ventral scales of forelimbs granular, juxtaposed, mostly homogeneous; scales on palm heterogeneous, granular juxtaposed; scales on hindlimbs smaller than those of belly, smooth, cycloid and subimbricate; scales on the knee, above cloaca and on thigh below the level of precloacal pores are smaller and granular; scales on soles heterogeneous, granular, juxtaposed to subimbricate.
Tail complete, regenerated (TL = 80 mm), slender, gradually tapering, segments indistinct; dorsal scales small, granular, juxtaposed at the base, posteriorly size increases, flat, smooth, subimbricate, heterogeneous in shape and size; large feebly keeled scales up to fourth segment of the tail at the distal end of each segment, those on basal segment are pronounced; subcaudal scales smooth, subimbricate, wider than that of dorsal, heterogeneous in shape and size; below cloaca scales are granular, smaller than the rest of the tail scales; no enlarged plate like series of subcaudal scales; three bluntly conical spurs on each side of the tail base present.
Colouration in preservative.
Top of head, limbs and tail pale-brown; dorsum pale-greyish-brown; a slightly dark-brown stripe radiating from posterior orbital border to occipital region, medially “ W ” shaped; an another short dark-brown stripe at the middle of the head; a short, posteriorly diffused dark-brown stripe starting from posterior corner of the upper eyelids; a faint brown stripe on the loreal region; rostral and mental scale, labial scales dark-greyish-brown with white patch posteriorly; short and irregular shaped, longitudinal dark-brown stripe on dorsal side of neck; six irregular shaped, zig-zagged dark-brown bands on dorsum; irregular shaped, large dark-brown spots on sacrum and tail base; zig-zagged dark-brown bands on anterior part of the tail, posterior half of the tail (regenerated part) with brown speculation; indistinct brown reticulation on dorsal side of the limbs; ventrally head, body and limbs creamy-white with brown speculation; chin scales and scales below infralabials heavily speckled; lamellae, palm and feet heavily speckled with brown; indistinct brown patches on ventral side of the tail.
Morphological variation.
Detailed morphological variations among the collected individuals of Cyrtodactylus siangensis are provided in Table S 2. Dorsal dark brown markings in the two paratypes are variable in the form of irregular zig-zagged bands to reticulation; reticulation on limbs of the two paratypes distinct than the holotype; cross bands on tail of WII-ADR 1581 darker posteriorly (Fig. 9).
Comparison.
Morphologically Cyrtodactylus siangensis sp. nov. is close to C. cayuensis, however, phylogenetically it is distinct from the later (Fig. 2; Table S 3), also the type locality of the new species is separated by Siang River from the C. cayuensis localities recorded in this study (Fig. 3 B). Morphological differences with other members of khasiensis group is presented in Table 2.
Sequence divergence.
Cyrtodactylus siangensis sp. nov. has a high genetic divergence of 11.7–17.0 % from its closely related and the only other species in the clade, C. cayuensis.
Etymology.
The specific epithet is a toponym derived from the name of the river “ Siang ”. The type locality of this species lies in the Siang valley of Arunachal Pradesh.
Suggested common name.
Siang Valley bent-toed gecko.
Distribution and natural history.
Cyrtodactylus siangensis sp. nov. is currently only known from the type locality, Bodak, East Siang District. It appears to be uncommon, and likely a habitat generalist. The holotype was encountered on a shrub at the edge of Kalek stream (a tributary of Siang River) at a height of approximately one meter above the ground, at 18: 15 hrs. The stream at the time of survey was flowing at a moderately speed, was approximately 10 m in width and contained boulders (sedimentary rock) and fallen logs. The two paratypes were recorded on a small tree at a height of 2.0 m on the slope of a hill close to the collection site for the holotype. The type locality is ca. 300 m from Siang River and approximately 150 m from the road connecting Pasighat and Yinkiong.
description: Published as part of Boruah, Bitupan, Narayanan, Surya, Aravind, Neelavar Ananthram, Lalronunga, Samuel, Deepak, V. & Das, Abhijit, 2024, Description of six new species of Cyrtodactylus Gray (Squamata: Gekkonidae) from northeastern India, pp. 453-486 in Vertebrate Zoology 74 on pages 453-486, DOI: 10.3897/vz.74.e124752