Crenadactylus horni ( Lucas & Frost, 1895 )

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 : 250-253

Crenadactylus horni ( Lucas & Frost, 1895)

Central Uplands clawless geckos Figures 3 D, 4B, 8, 9

Ebenavia horni Lucas & Frost, 1895

[‘Central Ranges’ of Oliver et al. (2010)]

Holotype. NMV D7533, adult female, Camp 4 of the Horn Expedition, near Charlotte Waters, Northern Territory fide Dixon and Kluge (1964), donated to National Museum Victoria, Melbourne, Australia ( NMV) by W.B. Spencer, April 1897. Stored in 70% ethanol at NMV.

Diagnosis. A moderately large (to 34.8 mm SVL), robust species of Crenadactylus with wide (HW/HL 0.48– 0.63) and deep (HD/HL 0.28–0.42) head with a long snout (SnL/HL 0.34–0.42). Rostral in full contact with nostril, enlarged internasal extending beyond supranasal, 2 slightly enlarged postmentals, dorsal scales homogeneous, smooth or feebly keeled, 6 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, lateral zones pale tan with irregular dark brown stippling, occasionally forming 1 or 2 broken or weakly defined lateral lines; ventrum pale off-white with moderate to weak stippling.

Description. The holotype is in very poor condition (shrivelled, blackened, front limbs broken off; Fig. 8 ) so the following description is based on other specimens in good condition. A moderately built, small-bodied gecko (to 34.8 mm SVL); body elongate, oblong in cross-section; head slightly wide (HeadW/HeadL 0.48–0.63), moderately long (HeadL/SVL 0.27–0.32), slightly deep (HeadD/HeadL 0.28–0.42); in dorsal view, widest at ear openings; head distinct from neck with neck slightly constricted; canthal-loreal region slightly convex; snout moderately long (SnL/HeadL 0.34–0.43), tapering to rounded tip; eye moderately large; pupil vertical with four scallops; rostral ~3 times wider than tall, in broad to point contact with nostril, dorsal edge below supranasals concave to accommodate supranasals, rostral groove extends from posterior edge of rostral to ~50% of rostral height; supranasals oblong, ~1.5 times wider than long; single enlarged internasal circular, dorsal edge extends beyond dorsal edge of supranasals, occasionally a tiny additional internasal between enlarged supranasal and rostral; nostrils small, slightly smaller than loreals, directed laterally, in contact with rostral, supranasal, 3 postnasals and first supralabial; supralabials 7–9, antero-dorso edge of first supralabial in contact with nostril, postero-dorso edge notched by second postnasal and first loreal, other infralabials rectangular, wider than high, gradually decreasing in size, to corner of mouth; scales on crown small and rounded, ~one-half the size of dorsal scales, increasing in size anteriorly onto snout and supraocular regions; scales on snout flat and slightly enlarged, 2–3 times larger than scales on crown; 1 or 2 soft spines on posterior eyelid; mental triangular to trapezoidal in shape, widest anteriorly, not extending past ventral edge of first infralabial; 2–3 postmentals not slightly enlarged relative to other scales adjacent to infralabials; gulars small near infralabials, decreasing to granular, ~0.2 the size of scales on ventrum; infralabials 7–9, first largest and square-shaped, gradually decreasing in size posteriorly; ear opening small and round to elliptical in shape.

Limbs short, distance between limbs close to half of SVL (ILL/SVL 0.37–0.50); scales on anterior surfaces of forelimbs broad and rounded, slightly imbricate, ~2 times the size of scales elsewhere on forelimb; scales on dorsal surface of hind limbs rounded and slightly raised; scales on anterior surface of thigh flat and circular, slightly larger in area than scales on hindlimb and elsewhere; fingers 5; toes 5; digits short, terminating in 2 enlarged apical plates, claw absent; fourth finger lamellae in 6 rows; fourth toe lamellae in 8 rows; apical plates much wider than digit.

Scales on dorsum and lateral surfaces homogeneous and smooth and rounded (lacking defined keels) to feebly keeled, ovoid in cross-section, juxtaposed; scales slightly raised, highest point at posterior edge of scale, widest at midpoint of scale; scales on ventrum homogeneous, flat, imbricate, equal to 2 times the size of dorsal scales in area, widest at midpoint, with rounded posterior edge.

Tail moderately long, maximum width 1/4 to 1/3 along tail, gradually tapering to a fine point, round in crosssection; scales on dorsal surface of tail ~2–3 times size compared to dorsum, homogeneous, flattened, imbricate, square to oblong in shape, arranged in travnserse rows; subcaudal scales flattened, ~2–3 times the size of dorsal tail scales; post-cloacal scales 1.5 times larger than typical ventral scales; single enlarged cloacal spur per side, ~3–4 times the size of surrounding scales; no visible pre-cloacal pores (except on 2 males, with six pores).

Colouration and pattern. Ground colour tan to dark brown; a narrow silvery-grey vertebral stripe usually visible, 2–4 scales wide; vertebral stripe bordered by medium brown paravertebral stripes with darker brown margins; pale dorsolateral stripe 3–5 scales wide, narrowing on neck to ~6 smaller scales, continuing to posterodorsal edge of eye and through eye as pale canthal stripe; wide, dark dorso-lateral stripe up to 9 scales wide, medium brown with dark brown borders, on some individuals, dark borders are highly contrasting with central lighter zone giving the appearance of two separate stripes, continues anteriorly through eye as dark loreal stripe; pale lateral zone with poorly-defined brown lateral stripe; ventral edge of orbit dark brown; labials stippled with dark brown; ventrum pale with light to medium stippling. In one specimen (SAMA R22245), the dorsolateral stripe is narrow and poorly-defined.

Distribution. Apparently isolated populations in the ranges of central Australia, with most records from the Northern Territory near Alice Springs and West MacDonnell and Finke Gorge National Parks ( Fig. 2 ). As far north as Wilora (AMS R52216), and east to near the Dulcie Ranges National Park (NTM R14120). Also occurring in north-central South Australia near the Ngarutjara and Pukatja homelands. All recent and reliable records are confined to rocky areas, separated by less suitable habitat, indicating populations are confined to these areas. The presumed type locality of Charlotte Waters in the Northern Territory (indicated by a ‘?’ in Fig. 2 ) is to the southeast of all other records, and the habitat is unlike that of the rest of this species’ records. The collection location is likely to be approximate based on the available landmarks that the Horn Expedition visited.

Habitat. Collection records for several specimens mention they were taken from spinifex clumps or from under rocks near spinifex, with records also from a rocky gully, rock platforms or outcrops.

Etymology. Named for William A. Horn, financer and early participant of the Horn Scientific Expedition to central Australia in 1894.

Remarks. The subspecies C. ocellatus horni used to refer to the central ranges species plus Crenadactylus from the Pilbara, Cape Range and west coast owing to their strongly striped appearance relative to the type (sub)species, C. ocellatus . Along with C. ocellatus , C. horni is a more large-bodied species within Crendactylus. Individuals also possesses this species’ unique diagnostic character of an enlarged supranasal scale ( Fig. 3 D) and rounded (not keeled) dorsal scales, otherwise, it is very similar to other striped species in the genus.

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 8. Holotype of Ebenavia horni (NMV D 7533) (scale bar = 10 mm).