Crenadactylus occidentalis, Doughty, Paul, Ellis, Ryan J. & Oliver, Paul M., 2016

Doughty, Paul, Ellis, Ryan J. & Oliver, Paul M., 2016, Many things come in small packages: Revision of the clawless geckos (Crenadactylus: Diplodactylidae) of Australia, Zootaxa 4168 (2), pp. 239-278 : 253-256

Crenadactylus occidentalis sp. nov.

Western clawless geckos

Figs. 4 C, 10, 11

[‘Carnarvon Basin’ of Oliver et al. (2010)]

Holotype. WAM R113683, adult male, Dirk Hartog Homestead , Dirk Hartog Island, WA (26°00'S, 113°12'E), collected by B. Maryan and R. Browne-Cooper, 19 April 1992. Fixed in 10% formalin, stored in 70% ethanol at WAM.

Paratypes (6). WAM R57525, 40 km north-east of Yuna, WA (28°06'S, 115°15'E); WAM R96676, 10 km north-west of Wandina Homestead, WA (27°56'S, 115°33'E); WAM R 120779, Nerren Nerren Station , WA (27°03'24"S, 114°35'21"E) ; WAM R124891, 38 km west south-west Hamelin Homestead, WA (26°35'34"S, 113°53'22"E); WAM R131376, 70 km south of Exmouth , WA (22°34'47"S, 114°07'00"E) ; WAM R135497, False Entrance Well, WA (26°23'S, 113°19'E).

Diagnosis. A medium-sized (to 32.6 mm SVL) species of Crenadactylus with wide (HW/HL 0.50–0.60) head. Rostral in full contact with nostril, internasal (if present) not extending beyond supranasal, 2 (occasionally 3) small postmentals, dorsal scales homogeneous and weakly keeled, 3–4 pre-cloacal pores, innermost pore-bearing scales separated by an intervening scale, no enlarged tubercles on original tails. Ground colour tan and light brown; dorsal pattern consists of well-defined pale and dark longitudinal stripes, small pale white to orange spots comprised of 2– 3 scales may be present, lateral zones pale to dark grey with at most faint uniform stippling (not forming lines); ventrum pale off-white with stippling absent to moderate.

Description of holotype. WAM R113683, a small adult male with the following meristics: SVL 28.0 mm; tail absent, remaining portion ~ 3.1 mm; HeadL 8.1 mm; HeadW 4.6 mm; HeadD 2.7 mm; SnL 2.5 mm; ILL 12.6 mm; SupLab 9 (left), 8 (right); InfLab 9, 8; internasals 0; PCP 4.

A slender, elongate, small-bodied gecko; body oblong in cross section, ~2.0–2.5 times wider than deep; head narrow (HeadW/HeadL 0.57), elongate (HeadL/SVL 0.29), moderately depressed (HeadD/HeadL 0.33); in dorsal view, widest at ear opening, as wide as widest portion of body; head not distinct from neck, neck weakly constricted; loreal region weakly convex, concave around nasal region; snout elongate (SnL 2.5; SnL/HeadL 0.31), rounded tip; eye moderately large; rostral ~3.0 times wider than high, in broad contact with nostril, dorsal edge concave to accommodate first supranasal, slightly notched by median internasal, rostral groove originates from dorsal edge of scale, ~40% of rostral height; internasals absent; supranasals 2 per side, first oblong, transverselyoriented, ~2.5 times wider than high, in broad contact with nostril; second supranasal small, rounded, ~half the size of first supranasal; nostril small, slightly smaller than second supranasal, directed dorsolaterally, in contact with rostral, first and second supranasals, three postnasals and first supralabial; postnasals 3; supralabials 9 (left), 8 (right), antero-dorso edge of first supralabial in contact with nostril; second supralabial square, narrower than first; supralabials 3–4 square, equal in size, 5–9 rectangular, gradually decreasing in size, all wider than high; scales on crown small and granular, increasing in size anteriorly onto snout; scales on snout flat, enlarged; supraocular scales enlarged; two enlarged conical scales at postero-dorso edge of eye; mental trapezoid-shaped, widest anteriorly, narrowing slightly to posterior edge, posterior edge not extending beyond ventral edge of first infralabials; postmentals 2, round in shape, equal to size of scales posterior to postmentals; gulars rounded, gradually decreasing in size posteriorly to granular scales; infralabials 8 on each side, 1–3 largest, equal in size, square-shaped, slightly higher than wide, 4–8 rectangular, wider than high, gradually decreasing in size posteriorly.

Limbs short, distance between limbs nearly half of SVL (ILL/SVL 0.45); scales on dorsal surface of forelimbs imbricate, rounded and slightly raised, becoming flatter distally; scales on ventral surface of forelimbs smaller; scales on dorsal surface of hind limbs imbricate, rounded and slightly raised, becoming flatter distally; scales on ventral surface of hind limbs similar to scales on dorsal surface of hind limbs, becoming granular distally; fingers 5 (fifth finger missing from left forelimb); toes 5; claws absent from all digits, digits moderately long; fourth finger lamellae in 8 rows; fourth toe lamellae in 10 rows; in dorsal view, enlarged scale between apical plates ~2 times the size of adjacent lateral scales, apical plates much wider than digit; two pairs of dorsal apical plates; one pair of ventral apical plates, ovate.

Scales on dorsum small and homogeneous, round to oblong, juxtaposed; scales weakly keeled, highest point at posterior edge of scale, widest at midpoint of scale, becoming flatter and imbricate laterally; scales on ventrum homogeneous, flat, imbricate, ~2–3 times the size of dorsal scales in area, widest at midpoint, rounded posteriorly.

Tail detached, remaining portion ~ 3.1 mm, tapers gradually from widest point posterior to vent; round in crosssection; scales similar to scales on dorsum, rounded and slightly raised, imbricate; ventral tail scales flattened and imbricate, ~1.5–2.0 times the size of scales on dorsal surface of tail; single enlarged raised post-cloacal spur on both sides of cloaca, ~10 times the size of surrounding scales; pre-cloacal pores 4, 2 innermost pore-bearing scales separated by a single intervening poreless scale, pore in notch on posterior edge of scale.

Colouration and pattern. In preservative, dorsum with longitudinal series of stripes, yellowish-brown ground colour; vertebral stripe silvery-grey, 3 scales wide; 2 dark brown paravertebral stripes, 3 scales wide; pale wide dorsal stripes, light yellow-brown with scattered dark scales, 4 scales wide, terminates at postero-dorsal edge of eye; brown latero-dorsal stripes 2–3 scales wide, originates at posterior edge of eye, over ear and above limbs, continuing to base of tail.

Variation. Most specimens were similar to the holotype in body size and proportions and scalation. Variation in the snout tip area usually took the form of from 3–6 scales in contact with first supranasals, including presence or absence of a small internasal between the first supranasals ( Fig. 3 C). Pre-cloacal pores were 4 with the exception of WAM R 120789 with 3. Males possessed enlarged cloacal spurs whereas in females, the spurs are smaller and protrude away from body less. Original tails with large scales (~4–6 times the size of dorsal scales), scales rectangular with rounded posterior edge, slightly imbricate, arranged in regular rows; subcaudal scales ~1.5 times larger than dorsal tail scales, flattened, imbricate; regenerated tails with smaller, flatter scales compared to original scales; hemipenes bifid.

Colouration and pattern. Highly contrasting dark brown and pale yellowish-brown longitudinal stripes; ground colour a dull tan or light yellow-brown; vertebral stripe pale silvery-grey, 3 scales wide, extending to crown; vertebral stripe enclosed by dark brown paravertebral stripes, 3 scales wide, that meet between hindlimbs and base of tail, extending anteriorly to crown, becoming intermixed with pale scales on crown; wide pale tan to light yellow-brown dorsolateral stripe, 4 scales wide, extends from upper part of eye to tail, extending forwards through eye to form pale canthal stripe, edged with dark brown in some individuals; above canthal stripes a dark brown triangular patch on snout; rostral and labial scales pale, darkly stippled to varying degrees, posterior edge of orbit with dark brown mark; dark brown dorsolateral stripes, 2–3 scales wide, emanate from posterior edge of eye and continue to tail, extending forwards through eye to form dark brown loreal stripe; pale dorsolateral zone occasionally flecked with small orange clusters of scales; dark paravertebral and dorsolateral stripes peppered with fine clusters or single pale scales in some individuals; lateral zone pale silvery-white, almost continuous to ventrum, thin weakly-defined brown lateral stripe usually present, below lateral stripe, scattered dark flecks may be present. Ventrum ranges from an almost immaculate, pale silvery-grey, to lightly stippled with black, occasionally forming short streaks. Limbs variably marked, a mixture of pale, light brown and dark brown scales with scattered clusters or ocelli of 3–8 pale scales, darker scales forming irregular dark variegations. Original tails have a continuation of the dorsal pattern, with dark brown paravertebral stripes on dorsum merging to form single dark vertebral stripe; regenerated tails have a mixture of dark and pale scales, not forming a regular pattern.

Distribution. Occurs on the Carnarvon coast of Western Australia from areas inland of Geraldton in the south, extending north through Kalbarri, Shark Bay and to the southern part of the North West Cape at Yardie Creek (where it is narrowly sympatric with C. tuberculatus sp. nov.) ( Fig. 2 ). Also collected from Bernier and Dorre islands in Shark Bay and off Carnarvon. Furthest inland occurrences near Wandana Nature Reserve at the southern part of its distribution (~ 100 km inland) and Nerren Nerren further north (~ 70 km inland) (both with genotyped specimens), otherwise most records occur within 50 km of the coastline.

Habitat. Collection records indicate a preference for spinifex and coastal dune vegetation such as shrubs, Acacia and Banksia . Occasionally collected from under tin and limestone slabs.

Etymology. The specific name occidentalis (Latin) refers to the western distribution of this species.

Remarks. This species’ distribution is closely associated with the western coast and its furthest inland extent is also the most southern, possibly indicating a low tolerance for extremely dry conditions. This area receives variable rainfall during the winter months (May–August), with decreasing rain furthest north where C. occidentalis is only found in a narrow band along the coast.

The sister species of C. occidentalis is C. tuberculatus sp. nov., with an estimate of divergence around 5 mya ( Oliver et al. 2010). Unlike the rather typical Crenadactylus morphology possessed by C. occidentalis , however, C. tuberculatus sp. nov. has a highly derived morphology and pattern and is entirely restricted to the rugged limestone hills and gorges of the Cape Range. The two species come into contact at the northern edge of the distribution of C. occidentalis , including sympatry where the two species meet at Yardie Creek.

Figures

FIGURE 2. Distribution of the Crenadactylus ocellatus species-group including new species described in this paper. Darker shades denote areas of high topographic complexity, lighter shades lower complexity. Colours for taxa match those in Fig. 1. Questionable type location of Ebenavia horni holotype indicated by ‘? ’.

FIGURE 3. Morphological variation within the Crenadactylus ocellatus species group (left to right, top to bottom): A) typical homogeneous dorsal scalation of Crenadactylus species (except C. tuberculatus), B) heterogeneous dorsal scalation of C. tuberculatus sp. nov. with enlarged tubercles, C) typical internasal configuration of Crenadactylus species (except C. horni) showing small internasal when present (upper left) or supranasals in contact (lower right), D) internasal configuration of C. horni showing enlarged internasal extending beyond posterior edge of supranasals, E) typical postmental configuration of Crenadactylus species (except C. pilbarensis) showing granular gular scales, F) postmental configuration of C. pilbarensis sp. nov. showing enlarged postmental, G) typical snout scalation in lateral view (exception C. rostralis, C. naso [part]) showing rostral-nostril contact, H) snout scalation in lateral view of C. rostralis (and C. naso [part]) showing excluded rostral contact with nostril. (Drawings: A, B – K. Aplin; C – F, R. J. Ellis; G, H – R. E. Johnstone.)

FIGURE 4. Photographs of Crenadactylus ocellatus species-group members in life (left to right, top to bottom): A) C. ocellatus, Koolyanobbing, WA (photo—R. J. Ellis), B) C. horni, Trephina Gorge, NT (photo—G. M. Shea), C) occidentalis sp. nov., 70 km S Exmouth, WA (photo—G. Gaikhorst), D) C. tuberculatus sp. nov., Cape Range National Park, WA (photo—R. J. Ellis), E) C. pilbarensis sp. nov., Burrup Peninsula, WA (photo—B. Maryan), F) C. rostralis, Geikie Gorge National Park, WA (photo—P. M. Oliver), G) C. naso, Koolan Island, WA (photo—G. Gaikhorst), H) C. naso, Mitchell Plateau, WA (Photo— G. M. Shea).