Papuascincus eldorado, Slavenko & Richards & Donnellan & Allison & Oliver, 2024

Slavenko, Alex, Richards, Stephen J., Donnellan, Stephen C., Allison, Allen & Oliver, Paul M., 2024, Gold in the mountains: Striking new species of Papuascincus (Sphenomorphini: Scincidae) from New Guinea, Vertebrate Zoology 74, pp. 133-149 : 133

Papuascincus eldorado sp. nov.

Figures 2 , 3 , 4

Papuascincus eldorado Golden Mountain Skink

Holotype.

QM J97880 (field number PMO 41; GenBank number OR837030), adult male, approximately 9 km east of Kiangibip Village, P’nyang Range, Western Province, Papua New Guinea (5.51°S, 141.57°E, 760 m a.s.l.), collected by P. M. Oliver, M. Sale and K. Aplin on 8 May 2013.

Paratypes (n = 16).

All Papua New Guinea. AMS R.115429-30, one adult female, one juvenile, Doido, Chimbu (Simbu) Province (6.550°S, 144.833°E, 1248 m a.s.l.), collected by S. Donnellan and K. Aplin in 1984; SAMA R.71758, adult female, Benaria, Hela Province (6.054°S, 142.978°E, 1330 m a.s.l) collected by S. Richards on 5 May 2005; BPBM 21668, adult male, Aseki: Piu village, Morobe Province (7.364°S, 146.216°E, 1130 m a.s.l.) collected by A. Allison on 10 August 1988; BPBM 21669-70, adult male, one juvenile, Komagowata: Wau-Aseki road, Morobe Province (7.265°S, 146.397°E 1100 m a.s.l.) collected by A. Allison on 10 August 1988; SAMA R.57406, adult male, Gobe: SE road above Ridge Camp, Southern Highlands Province (6.814°S, 143.774°E, 830 m a.s.l.) collected by S. Richards on 25 October 2001; field number PMO 8 (to be repatriated to PNGNM), adult male, same locality and collectors as holotype collected on 5 May 2013; NMV D76542-5, QM J97884 (GenBank number OR837031), J97885 and J97891, field number SJR14675 (to be repatriated to PNGNM), six adult males, two adult females, approximately 9 km east of Kaiangibip Village, Western Province: P’nyang Range (5.53°S, 141.56°E, 1075 m a.s.l.) collected by P. M. Oli-ver, M. Sale and K. Aplin between 20-26 April 2013.

Diagnosis.

A species of Papuascincus characterised by the unique combination of small size (maximum adult SVL 48.6 mm); 2-3 small rounded lobules on anterior edge of ear opening; supralabials seven; scale rows at midbody 24-28; postsuboculars typically two; paravertebral scales 43-50; lamellae under 4th toe 22-29; single supradigital scales on 4th toe 11-14; and dorsal colour pattern on body consisting of three greenish-gold dorsal stripes on a glossy black background; tail gold with scattered black flecks; limbs black with gold flecking.

Comparisons.

Papuascincus eldorado sp. nov. differs from all other species of Papuascincus in having a dorsal pattern consisting of three light stripes on black background versus two light dorsolateral stripes on light-brown background ( P. stanleyanus and P. buergersi ), two light dorsolateral stripes and two dark-brown medial stripes on light brown background ( P. morokanus ), or dark grey-brown blotches on light brown background ( Pap. phaeodes ). It additionally differs from P. stanleyanus (n = 1) and Pap. buergersi (n = 8) in having smaller adult size (maximum SVL 48.6 mm vs. 57.9 and 60.5, respectively) and a lower count of scale rows at midbody (24-27 vs. 31 and 28-31, respectively), from P. stanleyanus in having a lower count of paravertebral scales (43-50 vs. 64), from P. morokanus (n = 2) in having a higher count of single supradigital scales on 4th toe (11-14 vs. 6-7), and from Pap. phaeodes (n = 1) in having seven supralabials (vs. six), in having 2-3 small rounded lobules on anterior edge of ear opening (vs. 4-5 large, sharply pointed), and in having a much higher count of single supradigital scales on 4th toe (11-14 vs. 2).

In overall colour pattern Pap. eldorado sp. nov. is similar to Palaia pulchra , a species in a monotypic genus that is the sister lineage to the entire radiation of Papuascincus ( Slavenko et al. 2022), however it differs in its larger adult size (maximum SVL 48.6 mm vs. 40.8), in having sutured nasal scale (vs. unsutured; see Slavenko et al. 2022), tail gold in life (vs. orange), white lateral stripe absent (vs. present), and limbs overall black with gold mottling (vs. orange with black mottling).

Description of holotype.

Adult male, SVL 44.1 mm; tail regenerated, 60.6 mm total length, 30.4 mm regenerated section; FHD 20.5 mm; BW 8.2 mm; HL 10.6 mm; HW 6.7 mm; HD 5.1 mm; FLL 15.2 mm; HLL 21.0 mm.

Rostral broad and shallow, wider than deep, projecting slightly onto top of snout; nasals more or less rectangular, separated by rostral and frontonasal contact, projecting anterodorsally onto dorsum of snout; nostril circular, centred within nasal, with suture extending posteriorly from anterodorsal edge of nostril to edge of nasal scale; frontonasal large, with eight sides, extending laterally to slightly above level of nares, posteriorly in narrow contact with frontal; prefrontals large, separated by frontonasal and frontal contact, bordered lateroventrally by two loreals; supraoculars four, of which two contact the frontal and three contact the frontoparietal; frontal roughly kite shaped, widest anteriorly; frontoparietal single, anteriorly in narrow contact with frontal, posteriorly in contact with interparietal and parietals; interparietal smaller than fused frontoparietal, kite shaped, widest anteriorly; parietal eye spot absent; parietals in contact behind interparietal, in contact anteriorly with frontoparietal, posteriormost supraocular, and two pretemporals; nuchals in two pairs, transversely enlarged, wider than long, separated from secondary temporal by single intercalated scale.

Anterior loreal slightly smaller than posterior loreal, both higher than long; lower preocular roughly square; upper preocular much smaller than lower preocular, longer than high, separated from prefrontal by anteriormost supraciliary and posterior loreal contact; presubocular single, interdigitated between supralabials; postsuboculars two, lower interdigitated between subocular supralabial and penultimate supralabial; lower eyelid scaly, moveable, with clear palpebral disc roughly size of ear opening; supraciliaries eight, anteriormost not in contact with frontal, posteriormost projecting medially and interdigitated between posteriormost supraocular and upper pretemporal; primary temporal single, interdigitated between posterior two supralabials; secondary temporals two, upper larger and overlapping lower; supralabials seven, fifth in contact with small scales of lower eyelid; postsupralabials two; ear opening moderately large, with three small round lobules along anterior margin.

Mental single; postmental single, contacting two anteriormost infralabials; infralabials six; enlarged chin shields in three pairs, first pair in medial contact, second pair narrowly separated by single medial scale, third pair separated by three medial scales; posteriormost chin shield in contact with penultimate infralabial.

Body scales smooth, in 26 rows at midbody; paravertebral scales 46; medial precloacal scales enlarged, overlapping lateral precloacals.

Scales on dorsal surface of fourth toe in two rows proximally, single row distally beginning midway along proximal phalanx, 14 single scales; subdigital lamellae under fourth toe 27, smooth.

Colouration in preservative.

Base dorsal colouration glossy black, overlain with thin, slightly irregular but unbroken white vertebral stripe extending from snout-tip to base of tail, two thinner dorsolateral stripes with small number of narrow breaks, and small number of additional white flecks, especially in posterior half of body. Lateral surfaces of body largely black overlain with series of white mid-lateral flecks and further light ventrolateral mottling. Lateral surfaces of head white with prominent black patch in front of eye, and further extensive black flecking on lips. Ventral surfaces of body light buff, unpatterned. Limbs predominately black on dorsal and lateral surfaces with extensive white mottling, pale areas more extensive on hindlimbs than forelimbs. Ventral surfaces of limbs largely buff, but with scattered black flecks. Digits banded white and black on exposed surfaces, black on palmar and plantar surfaces. Original portions of tail faded yellow on exposed surfaces, buff ventrally, with fading series of black dorsal and lateral flecks extending from base to approximately 30 mm along tail. Regrown section of tail dirty yellow, unpatterned.

Variation in the type series.

Adult body size 37.8-48.6 mm SVL (mean = 43.0, SD = 3.2, n = 15). Males (mean = 43.7, range = 37.8-48.6, SD = 3.5, n = 11) reach larger size than females (mean = 41.7, range = 40.4-43.6, SD = 1.7, n = 4). FHD 16.4-22.4 mm (mean = 20.0, SD = 1.9, n = 15). BW 6.2-8.5 mm SVL (mean = 7.3, SD = 0.8, n = 15). Forelimbs 31.9-38.4% of SVL (mean = 33.9%, SD = 1.8, n = 15). Hindlimbs 42.1-49.5% of SVL (mean = 45.8%, SD = 2.2, n = 15). Scale rows at midbody 24-27 (mean = 25.5, SD = 0.9, n = 17); paravertebral scales 43-50 (mean = 45.6, SD = 1.8, n = 17). Lamellae under 4th toe 22-29 (mean = 24.2, SD = 1.9, n = 17); single supradigital scales on 4th toe 11-14 (mean = 12.5, SD = 1.2, n = 17). Mostly three pairs of nuchals, but QM J97890, PMO 8, and SJR 14675 have two, NMV D76545 has four, and NMV D765440 has three on left side and two on right side. Primary nuchals usually separated from secondary temporals by single smaller intercalated scale, but BPBM 21670 and SAMA R.57046 have two on left side and one on right side. Prefrontals either separated by frontonasal and frontal contact (n = 9) or in narrow medial contact (n = 8). Presuboculars usually one (n = 15), rarely two (n = 2). Supracilliaries typically eight (n = 14), rarely seven (n = 1) or nine (n = 2). Anteriormost supraciliary typically in narrow contact with frontal (n = 14), occasionally separated (n = 3). Postsuboculars typically two (n = 16), rarely one (BPBM 21668). Chin shields typically symmetrical (n = 16), rarely two on left size contacting one on right side (NMV D76544).

Overall colour pattern is consistent across all specimens, comprising three dorsal stripes on black background on head and body, limbs mottled black and white, and tail yellowish with series of black lateral and dorsal flecks. Some variation in continuity and form of dorsolateral stripes evident, these often broken into series of flecks or blotches or even mottling, especially towards posterior part of body. Considerable variation in how far black flecking extend from the base of the tail, extent ranging between 10-30 mm from the base. Venter typically light buff and unpatterned, occasionally with scattered black flecks under tail and along sides of body. Exposed surfaces of original and regrown tail always dirty yellow.

Colouration in life.

The following description of colour in life is based on photographs of specimens QM J97880, SAMA R.71758, SAMA R.57046, and BPBM 21669, plus additional photographs of uncollected specimens provided by Mark O’Shea and Nick Baker (Fig. 3 ). Base colouration of dorsum glossy black, light patterning on head and body typically transitions from glossy greenish-yellow on head and anterior body to more yellow or gold on posterior body and tail. Pattern otherwise as per description in preservative.

Genetic comparisons.

Based on analyses of a 708 bp region of the ND4 mitochondrial gene Pap. eldorado sp. nov. is most closely allied (mean p-distance 11.7%) to Papuascincus lineage IV, a slightly larger form (SVL typically between 50-60mm) that occurs at higher elevations in the Central Cordillera (1500-2500 m a.s.l.) ( Slavenko et al. 2020). The two sequences for Pap. eldorado sp. nov. were identical.

Etymology.

From the Spanish noun phrase meaning "the golden", in reference to the species’ distinct golden colouration.

Distribution.

This species is known from numerous sites spanning 500 km along the southern versant of New Guinea’s Central Cordillera, extending from Western Province, in the west through Southern Highlands, Hela and Chimbu Provinces, and as far east as the Bulolo area, Morobe Province. Given its wide range in PNG, it is possible that it also extends further west into Papua Province of Indonesian New Guinea.

Natural history.

All records of Pap. eldorado sp. nov. are from foothill and lower montane forest between 760 and 1600 m a.s.l. Records on the P’nyang Range (Fig. 4A ) are from between ~760 m a.s.l and 1075 m a.s.l. (the maximum elevation sampled), and the new species was not observed during extensive searches at 560 m a.s.l. in this same range. In the Moran area of Hela Province the species was encountered up to 1600 m a.s.l. (Mark O’Shea pers. comm.) but it was not observed at sites>2,000 m a.s.l. on Gigira Ridge to the northwest of Moran during extensive surveys there (S. Richards pers. obs.). On the Wau-Bulolo-Aseki road this species was only observed at around 1100 m a.s.l. despite extensive surveys at other elevations along the road during the 1980s. An observation on iNaturalist from along the Aseki road on the south side of the central divide (7.334°S, 146.314°E; https://www.inaturalist.org/observations/141932949) was at an elevation of around 1275 m a.s.l. (Mattias S Lanas pers. comm.). These data all suggest that Pap. eldorado sp. nov. is mostly restricted to a relatively narrow elevational band, but extends broadly along the southern edge of the Central Cordillera in Papua New Guinea. The only exception to the generally southern versant distribution are the specimens from Komagowatta, just north of the main range along the well-travelled road to Aseki.

At most localities in the west of its range this species was collected on karst basement. Due to the very thin soils and complex nature of these landscapes tree cover was in many areas relatively low and quite patchy, with few very large emergent trees (Fig. 4A ). Animals were typically observed basking in patches of sun on the forest floor or atop vegetative debris around campsites. Of the ten specimens in the series from P’nyang eight were males and two were females suggesting that at the time of this survey (April-May) males may be more active or more detectable than females. Other basking skinks collected in sympatry were Emoia physicina Brown & Parker, 1985 and E. physicae ( Duméril & Bibron, 1839) at 760 m a.s.l. and E. brongersmai Brown, 1991 at 1075 m a.s.l. Similarly, our specimens from the vicinity of Aseki, in the eastern part of the range, were from relatively open secondary growth areas amidst towering columns of karst. They were typically observed basking on the ground in patches of sun, where they co-occurred with at least two species of widely distributed mid-montane ground skinks, E. physicae and E. pallidiceps (De Vis, 1890). We also collected Lygisaurus cf. novaeguineae (Meyer, 1874) from the interior of patches of adjacent forest.

Lineages III and IV of Papuascincus ( Slavenko et al. 2020) occur in close proximity to Pap. eldorado sp. nov., but typically occur at higher elevations and differ greatly in colouration. Lineage IV, which is widely distributed in the Central Cordillera, is phylogenetically close to Pap. eldorado sp. nov. but is much larger (adult SVL 44.4-63.7 mm) and differs in colouration (it exhibits the “classic” Papuascincus dorsal pattern of two light dorsolateral stripes on light brown background) and elevational range (> 1800 m a.s.l.). Lineage III is similar in size to Pap. eldorado sp. nov. (36.3-54.4 mm), but also has the “classic” Papuascincus dorsal pattern and almost all Central Cordillera populations of this form sampled by Slavenko et al. (2020) occur at elevations above 1700 m a.s.l. At ~1075 m a.s.l. In the P’nyang area we photographed a single specimen of Papuascincus that we tentatively assign to lineage III based on colour pattern, providing evidence of sympatry. We are also aware of populations of lineage III on Mt. Missim, Morobe province at elevations of 1190-1300 m a.s.l., slightly above the known distribution of Pap. eldorado sp. nov. in Morobe Province (1100-1130 m a.s.l.). These data suggest that the elevational distributions of lineage III and Pap. eldorado sp. nov. abut, but do not extensively overlap where the species occur in close proximity. Three other potentially undescribed species of Papuascincus were collected on the Wau-Aseki road at higher elevations than BPBM 21668-70.

Suggested IUCN status.

The populations described herein represent an extent of occurrence of 19,986 km2 and an area of occupancy of 80 km2 (based on occupation of 4 km2 cells; both calculated using http://geocat.kew.org). The species occurs over a wide area, on multiple substrates, and at an elevational band that suggests a considerable scope for upslope retreat as global temperatures rise in coming decades. We therefore recommend assigning an IUCN red list conservation status of Least Concern for Pap. eldorado sp. nov. .

Figures

Figure 2. Papuascincus eldorado sp. nov. holotype (QM J 97880); A dorsal view, B ventral view, C lateral view of head, D dorsal view of head, and E ventral view of head. Images by Alex Slavenko.

Figure 3. Photos in life of Papuascincus eldorado sp. nov.: A holotype (QM J 97880) from P'nyang, Western Province; B paratype (BPBM 21669) from Aseki, Morobe Province; C paratype (SAMA R. 71758) from Benaria, Hela Province; D paratype (SAMA R. 57046) from Gobe, Southern Highlands Province; E - F uncollected specimen from Moran, Hela Province. Image A by Paul M. Oliver, image B by Allen Allison, images C and D by Stephen J. Richards, images E and F by Mark O'Shea.

Figure 4. Habitat photos of (A) P'nyang, type locality for Papuascincus eldorado sp. nov., and (B - C) summit of Mt. Menawa, type locality for Papuascincus borealis sp. nov. Image A by Paul M. Oliver, images B and C by Allen Allison.