Gehyra electrum, Zozaya & Fenker & Macdonald, 2019

Zozaya, Stephen M., Fenker, Jéssica & Macdonald, Stewart L., 2019, A new species of rock-dwelling gecko (Gekkonidae: Gehyra) from the Mt Surprise region of northern Queensland, Australia, Zootaxa 4688 (4), pp. 503-518 : 508-513

Gehyra electrum sp. nov.

Amber rock dtella

Figs. 1 , 4–7 , 10

Holotype ( Fig. 4 ). QM J96403 ( SMZ0970 ), adult male collected from Springfield Station , Queensland (17.89°S, 144.41°E, 490 m elevation) on 23 September 2017 by S.M. Zozaya, J.W. de Jong, and A.L. Fenner.

Paratypes. Talaroo Station, Queensland (18.02°S, 143.79°E): QM J96402 (male), QM J96408 (female) . Springfield Station, Queensland (17.89°S, 144.41°E): QM J96404 (female) . Amber Station , Queensland (17.74°S, 144.32°E): QM J70090 (male)

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Diagnosis. A medium-sized (46–50 mm SVL) species of Gehyra ; no webbing of skin between toes III and IV; no skin-fold along posterior of hindlimb; subcaudal scales transversely widened; rostral scale gabled dorsally with a deep medial groove on the dorsal half of the scale; single internarial scale usually present; 2 postnasals of similar size, or with lower postnasal slightly larger; mental scale wedge-shaped posteriorly; 2–3 pairs of postmental scales (chin shields), with inner pair largest and separated from each other by the mental scale along 40% or more of their length; 7–9 supralabials; 7–8 infralabials; snout moderately convex in lateral view; 7–8 undivided subdigital lamellae on the expanded portion of the fourth toe, excluding the apical wedge; subdigital lamellae often with deep medial notch but never fully divided; no granules separating proximal lamellae; adult males with 12–13 pre-cloacal pores arranged in a shallow wedge that points anteriorly; background colouration orange-brown to pinkish-orange; dorsal pattern variable but typically consists of white spots, sometimes arranged in transverse rows, with dark spots that sometimes merge into irregular blotches or dark transverse bands.

Etymology. From the Latin noun electrum , meaning ‘amber’, in reference to the orange-brown background colouration typical of the species, and alluding to Amber Station, where the earliest confirmed specimen of this species was collected (paratype QM J70090 ). The name is treated as a noun in apposition.

We recommend the common name ‘Amber rock dtella’ for this species. Recent taxonomic revisions of Gehyra have moved away from recommending ‘dtella’ in common names, instead favouring ‘Gehyra’ ( Doughty 2018a; Kealley 2018) or simply ‘gecko’ ( Oliver et al. 2016; Doughty 2018b). Kealley et al. (2018) provide justification for this: “We prefer to use ‘Gehyra’ as the common name over ‘dtella’ as the generic name is already available and just as easy or difficult to remember than an additional name fabricated for use as a common name.” The name ‘dtella’, however, is not fabricated but appears to be the indigenous name for Gehyra from the Chillagoe region of northeastern Queensland ( Broom 1897). This is the same general region that G. electrum sp. nov. is found, and because of this, we prefer to use the name ‘dtella’ for this species.

Description of type series (N = 5). Data presented as range followed by mean in brackets. Measurements (mm). SVL 46.9–49.8 (48.2); TailL 37.5–52.0 (45.13); TrunkL 21.6–25.1 (23.2); HeadL 10.5–11.2 (10.8); HeadW 9.1–10.3 (9.6); HeadD 4.1–4.9 (4.5); SnEye 4.4–4.7 (4.5); EyeEar 3.1–3.4 (3.2); OrbitL 2.4–4.7 (4.6); IntOrbDist 5.1–5.8 (5.5); IntNarDist 1.2–1.8 (1.5); HindL 5.9–6.4 (6.2); ArmL 5.1–5.5 (5.3).

Head. Moderately depressed (HeadD/HeadL = 0.4) and moderately wide (HeadW/HeadL = 0.9), snout short (SnEye/HeadL = 0.4) and moderately convex when viewed laterally, with a shallow depression between the convexly curved canthal ridges; eyes large (OrbL/HeadL = 0.2–0.3); neck wide, being only slightly narrower than head or wider in females with enlarged endolymphatic sacs; head covered in small granular scales that are largest on the dorsal and lateral surfaces of the snout; interorbital counts 30–33 (31.2); rostral scale approximately twice as wide as deep, gabled dorsally, and deeply grooved medially on the dorsal half; nostrils rounded and contacted by rostral, supranasal, two postnasals, and first supralabial; postnasals similarly sized, or lower postnasal slightly larger than upper; supranasals usually separated medially by a single small internarial scale along the dorsal edge of rostral (4 of 5 specimens; QM J96404 without internarial); supralabials 7–9 (8.2); infralabials 7–8 (7.6); mental scale protrudes in a wedge-shape posteriorly, separating the inner-postmentals from each other along 40–50% of their length; 2–3 pairs of enlarged postmentals, with inner pair largest; inner-postmentals in contact with mental and first infralabials, sometimes narrowly contacting the second infralabials on one side; second pair of postmentals usually in contact with first and second infralabials, or sometimes excluded from first supralabial on one side; third pair of postmentals, when present, do not contact infralabials; ear opening moderately large and rounded or vertically elongate. Scales on gular region small, flat, and slightly overlapping, gradually increasing in size and becoming more granular near the postmentals, infralabials, and parinfralabials.

Body. Moderately robust (TrunkL/SVL = 0.5) and dorsoventrally flattened; dorsum covered in non-overlapping granular scales; scales on ventral surfaces flat, often overlapping, and approximately 2–6 times larger than those on dorsum; 2–3 enlarged cloacal spurs behind the lower posterior margin of the thigh in both sexes, but more welldefined in males; 12–13 (12.3) pre-cloacal pores in males that form a shallow chevron anterior to the cloaca, with central pores anteriormost; pre-cloacal pores absent in females.

Limbs. Limbs of moderate length (ArmL/SVL = 0.1; HindL/SVL = 0.1); digits short, dorsoventrally compressed, and expanded distally; claw protrudes dorsally from the expanded portion of all except the first digit (anteriormost) of manus and pes; 7–8 (7.6) enlarged subdigital lamellae on the expanded portion of the fourth toe, excluding the apical wedge; 6–7 (6.4) enlarged subdigital lamellae on the fourth finger, excluding the apical wedge; subdigital lamellae often with deep medial notch, particularly on proximal lamellae, but never fully divided. Scales on ventral and anterior surfaces of thigh large, flat, and slightly overlapping; scales on dorsal and posterior surfaces of limbs small, granular, and non-overlapping.

Tail. Original tail long (TL/SVL = 1.0–1.1; N = 2, includes QM J96404 with regrown tail-tip), slender, slightly dorsoventrally compressed, and tapering to a pointed tip; fully regenerated tail shorter (TL/SVL = 0.8–0.9; N = 2) and more strongly tapered. Medial scales on ventral surfaces of tail much wider than long and slightly overlapping, bordered laterally by a row of moderately enlarged overlapping scales, with scales on dorsal and lateral surfaces of tail smaller, granular, and arranged in regular rows; in regenerated tails lateral and dorsal scales are flatter and in irregular rows.

Colouration in life ( Figs. 4B , 6A–D , 7A , 10 ). Background colouration varies from a pale pinkish-orange to a darker orange-brown. Patterning consists of scattered whitish spots and darker (black to purple-brown) blotches or bars; whitish spots and darker blotches are often arranged in alternating transverse rows along the dorsum—in such cases, the darker blotches are often fused to become irregular transverse bars or blotches ( Fig. 6A & 6D ). In other individuals the whitish and darker blotches are more distinct and scattered in a seemingly haphazard fashion ( Figs. 4 & 7A ). Ventral surfaces whitish and largely unpatterned, often with fine dark stippling laterally and on the ventral surfaces of the limbs. Pattern on dorsum of original tails consist of alternating pale blotches and dark blotches or narrow transverse bars; regenerated tails with short, irregular, black to purple-brown longitudinal lines.

Colouration in spirit. Colour pattern in preservative is largely similar to the description in life except that the orange and/or pinkish background colouration is faded to shades of cream and brown (except paratype QM J70090 , which is a rich rusty orange), making the whitish spots and darker blotches indistinct and appear almost entirely absent in paler individuals.

Comparison with sympatric congeners. Gehyra electrum sp. nov. is sympatric with G. dubia ( Fig. 6 E–F) and G. einasleighensis ( Fig. 7B ). Gehyra electrum sp. nov. can be distinguished from G. dubia by the former’s smaller adult size (SVL 46–50 mm versus 49–64 mm in G. dubia ), orange-brown to pinkish-orange background colouration (versus ranging from whitish-grey to dark grey), and most reliably by the mental scale that forms a deep wedge between the inner-postmentals (versus a very shallow wedge; Fig 5 ). Gehyra electrum sp. nov. can be distinguished from G. einasleighensis by the former’s undivided subdigital lamellae (versus divided), a higher number of subdigital lamellae on the fourth toe (7–8 versus 6 or fewer), its larger adult size (SVL 46–50 mm versus 31–41 mm), and the presence of irregular large dark blotches or bars (versus relatively small, discrete dark spots). Gehyra electrum sp. nov. does not co-occur with the closely related G. catenata (nearest records ~ 330 km south) but can be distinguished from this species by its orange-brown to pinkish-orange background colouration with a pattern of whitish spots and black or purple-brown blotches or bars (versus light brown or grey background colouration with a darker chain-like dorsal pattern in G. catenata ; Fig. 7C ).

Distribution. Currently known from four sites in the Einasleigh Uplands of north-eastern Queensland: Talaroo Station, Springfield Station, Amber Station, and a photographic record from Hanging Rock ~ 30 km south-southeast of Almaden (17.59°S, 144.59°E; M. Anthony pers. comm.; Fig. 8 ). Targeted searches failed to find G. electrum sp. nov. in granite habitats closer to Almaden (17.400°S, 144.646°E) and Georgetown (18.504°S, 143.523°E). Nevertheless, suitable boulder habitat between known localities and the surrounding region is extensive and further survey effort will likely find this species elsewhere in the region.

Habitat and ecology. Gehyra electrum sp. nov. is associated with large granite boulders in savannah woodland ( Fig. 9 ). Most individuals have been found at night on vertical rock faces and overhangs, and occasionally on adjacent vegetation where they have been observed feeding on tree sap (J.M. Wright pers. obs.; Fig. 10 ). This species appears to prefer larger granite outcrops, where it can be found alongside G. dubia ; although the latter is much more common on trees at sites where G. electrum sp. nov. occurs. The sympatric G. einasleighensis is more commonly found on smaller rocks and rubble—similar to other small, spotted members of the genus—and is rarely found on large vertical rock faces ( Bourke et al. 2017; S.M. Zozaya pers. obs.).

Conservation status. With an extent of occurrence (the minimum convex polygon that encompasses all known occurrence points) of 976 km 2 and an area of occupancy (the total area of 4-km 2 grid cells the species is known from) of 20 km 2, Gehyra electrum sp. nov. appears to have the smallest known distribution of any eastern Australian Gehyra ; however, the species is extremely abundant where it occurs and suitable habitat at and between the known localities is extensive. While the species is not currently known from any national parks, the site at Talaroo Station is within the Talaroo Nature Refuge, which is managed for conservation by the Ewamian Aboriginal Corporation. While having a small geographic range or small population size is grounds for listing under IUCN Red List Criteria B–D ( IUCN 2012), there is no evidence of plausible threat or decline. Populations of G. electrum sp. nov. are therefore likely to be secure and we recommend that the species be classified as Least Concern. Nevertheless, more searches at new localities will be valuable to better understand the distribution, ecology, and conservation status of this species.

Figures

FIGURE 1. Ventral photo of the left hind foot of a Gehyra electrum sp. nov. illustrating how subdigital lamellae were counted. Note that this differs from the counts of King (1983), who included the apical wedge, unlike recent Gehyra descriptions.

FIGURE 4. Holotype of Gehyra electrum sp. nov. (QM J96403) from Springfield Station, Queensland. (A) Dorsal and ventral views of preserved holotype and (B) photo in life. Photos: Stephen Zozaya.

FIGURE 5. Condition of the mental (M) and inner-postmentals (IPM) in Gehyra electrum sp. nov. and G. dubia. Photos: Stephen Zozaya.

FIGURE 6. Colour pattern variation in Gehyra electrum sp. nov. from Springfield Station (A, QM J96404) and Talaroo Station (B, unsampled subadult; C, QM J96408; D, QM J96402), and comparison with sympatric G. dubia (E, Springfield Station; F, Talaroo Station). Photos: Stephen Zozaya (A, C–F); Scott Macor (B).

FIGURE 7. Comparison of (A) Gehyra electrum sp. nov. (SMZ0974), (B) G. einasleighensis (uncollected), and (C) G. catenata (uncollected). Photos: Stephen Zozaya.

FIGURE 8. Map of inland north-eastern Queensland showing the known localities of Gehyra electrum sp. nov. and sites at which it has not been found despite targeted searches. Also shown are nearby towns (white squares) and major roads. Background colour shows elevation.

FIGURE 9. Granite boulder habitats of Gehyra electrum sp. nov. at (A) Talaroo Station and (B) Amber Station. Photos: Stephen Zozaya (A); Justin Wright (B).

FIGURE 10. An adult male Gehyra electrum sp. nov. from Amber Station consuming sap from an unidentified Acacia. This individual has a fully regenerated tail. Photo: Justin Wright.