Oligosoma eludens, Knox & Chapple & Bell, 2024

Knox, Carey, Chapple, David G. & Bell, Trent, 2024, Oligosoma eludens sp. nov. (Reptilia: Scincidae) from the Hawkdun, Ida, and Saint Bathans Ranges of North Otago, Aotearoa / New Zealand, Zootaxa 5437 (4), pp. 480-494 : 483-484

Oligosoma eludens sp. nov.

Figures 1 (distribution), 2 (morphological variation) and 3 (habitat).

Holotype: NMNZ RE.008616, western slope of Peak 1658, south-eastern end of Hawkdun Range, Otago, New Zealand (-44.892481, 170.059696; 1,500 m ASL), 16 January 2020, coll: Tony Jewell.

Other material examined: Four live specimens captured (three adults, one juvenile) and three adults photographed only, at the type locality; one adult photographed in the Hawkdun Range two kilometres NW of the type locality (-44.878603˚S, 170.031174˚E; 1,300 m ASL); one live adult captured in the Ida Range near the head of Blue Duck Creek (-44.942777˚S, 170.172221˚E; 1,450 m ASL). Further individuals (est. nine in total) were observed at each site and their similarity in size, habitat, behaviour and colour pattern noted, but eluded attempts at capture or photography. In addition, several individuals were observed in January 2020 near the type locality, at -44.884581˚S, 170.059807˚ E. In November 2020, another population was discovered in the northern Saint Bathans Range in scattered boulderfield and talus at 1,600 m ASL. Three individuals were captured, examined, and photographed on site ( Knox et al. 2021b).

Etymology. L. eludens = eluding, i.e. elusive; as the species is difficult to capture. Vernacular name ‘rockhopper skink’ refers to the species habit of hopping between rocks when foraging or disturbed.

Diagnosis. A small Oligosoma (SVL 60–65 mm) with a smooth tail of moderate length (1.1–1.2 x SVL). Iris pale grey to light brown. Ear opening small (1.5 x diameter of nostril) with two small scales protruding from anterior margin. Four supraocular scales in each series. Fourth (longest) toe of hind foot with 24–27 subdigital lamellae. Coloured mid- to dark brown above with thin, smooth longitudinal stripes along back and sides, and lacking any prominent spots, flecks, or mottling. Mid-dorsal stripe is wide and present on the body of adults but often dull or indistinct and absent from the tail, and absent or indistinct on neonates. Throat pale grey or pale yellow with sparse dark specks, merging gradually into a uniform bright yellow belly. Soles of feet dark yellow-brown. The species can be separated from the below related species of which O. toka ( Chapple et al. 2011) and O. maccanni ( Hardy 1977) are in sympatry:

• Oligosoma stenotis (Patterson & Daugherty 1994) : distinguished from O. eludens sp. nov species by the presence of a keeled tail, smaller ear-opening, and a prominent mid-dorsal stripe versus a dull, indistinct, and wide mid-dorsal stripe in O. eludens sp. nov.

• Oligosoma burganae ( Chapple et al. 2011) : usually three, but sometimes four supraocular scales; body stocky; eye dark brown versus pale grey to light brown in O. eludens sp. nov.; ventral pale brown; 18–23 lamellae versus always four subraoculars; eye grey or light brown; ventral yellow; 22–27 subdigital lamellae in O. eludens sp. nov. Oligsoma eludens sp. nov. has thinner, smoother, and brighter (or whiter) dorso-lateral and mid-lateral stripes along the sides compared with O. burganae .

• Oligosoma repens ( Chapple et al. 2011) : three supraocular scales; lamellae 19–23 versus four supraoculars, 22–27 lamellae in O. eludens sp. nov. Oligosoma eludens sp. nov. has thinner, smoother, and brighter (or whiter) dorso-lateral and mid-lateral stripes along the sides compared with O. repens .

• Oligosoma toka : three supraoculars; 17–23 lamellae versus 22–27; soles cream or brown versus four supraocular scales; soles black in O. eludens sp. nov. Oligosoma eludens sp. nov. has thinner, smoother, and brighter (or whiter) dorso-lateral and mid-lateral stripes along the sides compared with O. toka .

• Oligosoma grande (Gray 1845) : much larger size <115 mm SVL versus <65 mm SVL in O. eludens sp. nov.; dorsal black or dark brown with cream of yellow flecks or striations; O. eludens sp. nov. has thinner, smoother, and brighter (or whiter) dorso-lateral and mid-lateral stripes along the sides compared with O. grande .

• Oligosoma maccanni : dorsal grey or grey-brown; if dorsal stripes present, mid-dorsal stripe bright and not usually smooth; ventral grey or muddy yellow; soles white or cream versus dorsal brown base colour; dull, indistinct, and wide mid-dorsal stripe in O. eludens sp. nov. Oligosoma eludens sp. nov. has thinner, smoother, and brighter (or whiter) dorso-lateral and mid-lateral stripes along the sides compared with O. maccanni .

Figures

FIGURE 1. Map showing distribution of four related Oligosoma species, including O. burganae (orange), O. repens (green) and O. toka (blue) and O. eludens sp. nov. (yellow).