Oligosoma salmo, Melzer & Hitchmough & Bell & Chapple & Patterson, 2019

Melzer, Sabine, Hitchmough, Rod A., Bell, Trent, Chapple, David G. & Patterson, Geoff B., 2019, Lost and Found: Taxonomic revision of the speckled skink (Oligosoma infrapunctatum; Reptilia; Scincidae) species complex from New Zealand reveals a potential cryptic extinction, resurrection of two species, and description of three new species, Zootaxa 4623 (3), pp. 441-484 : 467-470

Oligosoma salmo sp. nov.

Figures 7a, b

Synonyms

Leiolopisma “ West Coast skink”

AVISS & LYALL 1995

Oligosoma infrapunctatum

GREAVES et al. 2008; CHAPPLE et al 2009

Oligosoma aff. infrapunctatum ‘Chesterfield’

HITCHMOUGH, R., BULL, L. & CROMARTY, P. 2007; HITCHMOUGH et al. 2010; HITCHMOUGH et al. 2013; BELL 2014; HITCHMOUGH et al. 2016a; HITCHMOUGH et al. 2016b; VAN WINKEL et al. 2018.

Holotype. Chesterfield (42º 37’S, 171º 05’E), NMNZ RE005444, male (coll. G. Patterson, 23 Mar 1994).

Paratypes (4 specimens). Chesterfield (42º 37’S, 171º 05’E), 2 specimens: NMNZ RE005445, male; NMNZ RE005446, male (coll. G. Patterson, 23 Mar 1994) ; Chesterfield (42º 37’S, 171º 05’E), 2 specimens: NMNZ RE005364, male; NMNZ RE005365, female (coll. R. van Mierlo, P. van Klink, 09 Jan 1998)

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Diagnosis. O. salmo can be distinguished from other species in the O. infrapunctatum species complex by a combination of characters ( Figure 4 a–j). There are statistical differences between O. newmani and O. salmo (S-Ear/ EF, VS, upper ciliaries). Compared with O. newmani MS is usually 33 or below whereas O. salmo is 33 or above. In O. robinsoni SVL/HW is usually 11 or below, whereas in O. salmo it is 11 or above. There are statistical differences between O. robinsoni and O. salmo (VS, subdigital lamellae). The VS count is 69 or below in O. salmo versus usually 69 or greater in O. robinsoni ; supraciliaries 5 only ( O. salmo ) versus usually> 5 in O. robinsoni ; ventral speckling much more pronounced in O. robinsoni than O. salmo . There are statistical differences between O. salmo and O. albornense sp. nov. (upper ciliaries, HL/HW, S-Ear/EF, VS). O. salmo has 5 supraciliaries only, versus 6 or more in O. albornense sp. nov. O. salmo has 3 or fewer nuchal scale pairs, while O. albornense sp. nov. has 3 or more nuchal scale pairs. There are statistical differences between O. salmo and O. auroraensis sp. nov. (VS). It differs from O. auroraensis sp. nov. i n having subdigital lamellae usually 21 or above ( O. auroraensis sp. nov.) versus usually 20 or below. It appears to have a shorter tail (1.25 TL/SVL versus mean TL/SVL of 1.38 in O. auroraensis sp. nov.).

Description of Holotype. Habit lacertiform, body elongate, oval in cross-section; limbs well developed, pentadactyl. Lower eyelid with a transparent palpebral disc, bordered on sides and below by small, oblong granules. Snout moderately blunt. Nostril centred in lower middle of nasal, not touching bottom edge of nasal, pointing up and back. Supranasals absent. Rostral broader than deep. Frontonasal broader than long, not separated from frontal by prefrontals meeting in midline. Frontal longer than broad, shorter than frontoparietal and interparietal together, in contact with 2 anteriormost supraoculars. Supraoculars 4, 2 nd largest. Preoculars, 2, upper one larger. Frontoparietals distinct, larger than the interparietal. A pair of parietals meeting behind interparietal and bordered posteriorly by a pair of nuchals and temporals, also in contact with interparietal, frontoparietal, 4 th supraocular, and 2 postoculars. Loreals 2, anterior one the larger; anterior loreal in contact with 1 st and 2 nd supralabial, posterior loreal, prefrontal, frontonasal, and nasal; posterior loreal in contact with 2 nd and 3 rd supralabial, 1 st subocular, upper and lower preocular, prefrontal, and anterior loreal. Supralabials 7, 6 th and 7 th largest. Infralabials 6, several equally largest. Fifth supralabial below centre of the eye. Temporals: 1 primary; 2 secondary. Ear opening round, moderately large (1.8% as percentage of SVL), with several small projecting granules on anterior margin. Suboculars 8, 3rd and 4 th separated by 5 th supralabial. Mental broader but shallower than rostral. Postmental similar size to mental. Chinshields 3 pairs. Dorsal scales largest, weakly striate. Ventral scales and subdigital lamellae smooth. Adpressed limbs not meeting. Digits moderately long, subcylindrical. Third front digit shorter than the 4 th.

Measurements (in mm; holotype with the variation shown in the specimens examined in parentheses). SVL 60.0 (mean 62.2, range 53.8–76.2), HL 8.5 (mean 9.6, range 8.1–12.5), HW 7.8 (mean 6.0, range 4.7–7.8), AG 29.6 (mean 32.4, range 28.1–39.9), SF 23.6 (mean 24.0, range 21.0–20.0), S-Ear 12.2 (mean 12.5, range 10.7– 14.7), EF 11.3 (mean 11.9, range 10.6–15.5), HLL 19.9 (mean 18.7, range 17.0–20.5), D-Ear 1.1 (mean 1.2, range 0.8–1.5).

Variation (holotype with the variation shown in the paratypes /specimens examined in parentheses). Upper ciliaries 8 (mean 7, range 5–8); lower ciliaries 10 (mean 9, range 8–10); nuchals 3 pair (mean 2 pairs, range 1–3 pairs); midbody scale rows 35 (mean 33, range 32–35); ventral scale rows 69 (mean 63, range 59–69); subdigital lamellae 19 (mean 19, range 17–22); supraciliaries 5 (mean 5, range 5–5); suboculars 6 (mean 6, range 6–6). Frontonasal usually not separated from frontal by prefrontals meeting in midline. Anterior loreal usually in contact with first and second supralabial, posterior loreal usually in contact with second and third supralabial. Supralabials 7, the sixth the largest. Infralabials 5 or 6 (usual). Projecting scales usually present in ear opening. Maximum SVL of preserved specimen 76.2 mm; largest measured in field study 83 mm. Only 1 of the specimens examined had an intact tail, tail length of intact specimen 75 mm. TL/ SVL = 1.25. Ratios for morphological measurements (+ SD): AG/SF 1.35 + 0.06; S-Ear/EF 1.06 + 0.1; HL/HW 1.66 + 0.34 (N=5).

Colouration. This is variable among specimens, but the most common colouration is as follows: Mid-dorsal stripe where present not continuous. Dorsal surface mid brown, usually with light and dark flecking, 6 scale rows wide, grading into pale dorsolateral stripe extending from behind ear to base of tail, often becoming indistinct along body. This pale stripe is bordered below by a ½ scale row wide dark brown band, below that a 2-scale wide lighter brown row, notched on upper and lower edges, running from behind nostril through eye towards base of tail and becoming indistinct towards tip of tail. This band may have lighter speckling. Then a darker brown band 1 half-scales wide. This lower dark brown band is bordered below by a pale stripe, 1 to 2 half-scale rows wide running from below the eye, through the ear, above the limbs to become indistinct after the hindlimbs. This band is notched above and below. Soles of feet black. Belly bright yellow, sometimes speckled with darker flecks. Throat pale, speckled. Outer surface of forelimbs brown, speckled with light and dark. Dorsal surface of head with few dark markings. Under surface of tail blotched with pink-orange and black scales on a grey background.

Etymology. The scientific name is derived from the Latin for “salmon”, referring to the distinctive colouration on the underside of the tail. The accepted vernacular name is “Chesterfield skink” ( Bell 2014).

Distribution. The species is recorded from the West Coast of the South Island, in one coastal location only at c. 0-40 m ASL in the 50.01 Hokitika Ecological District. This is a mild, flat to rolling coastal lowland region that was formerly extensively forested and experiences high rainfall. It is currently known to be restricted to exotic grasslands between coastal sand dunes and managed pasture, in which it lives amongst the vegetation and takes refuge underneath logs, driftwood and discarded inorganic material ( van Winkel et al. 2018). Historically, it may have occupied coastal forest.

Natural History. Diurnal, heliothermic but cryptic sun-basker, terrestrial, may also be arboreal. A mediumsized (up to 85 mm SVL, usually <75 mm; 10.5 g) species. Aviss & Lyall (1995) undertook some surveys for the Chesterfield skink on the West Coast, and R. Hitchmough, L. Moran and L. Adams have undertaken more recent intensive surveys and population studies on this species since c. 2015 (R. Hitchmough, unpub. data). This species is unique in the known New Zealand skink fauna in having a prehensile tail (R. Hitchmough & L. Moran, pers. comm.; Figure 8 ). The species has relatively slow growth, with first reproduction of females usually at 4 years old. Births have been reported in late summer (early February) ( van Winkel et al. 2018).

Figures

FIGURE 4. a–j. Notched boxplots comparing the morphological characteristics of the species in the Oligosoma infrapunctatum species group (O. albornense, n=4; O. auroraensis, n=6; O. newmani, n=50; O. robinsoni, n=14; O. salmo, n=5). a) snout-ear (SE)/ear-axilla (EF), b) midbody scales, c) ventral scales, d) upper ciliaries, e) supraciliaries, f) supralabials, g) snout-vent length (SVL)/ hindlimb length (HLL), h) subdigital lamellae, i) axilla-groin (AG)/snout-forelimb (SF), j) head-length (HL)/ head-width (HW). If there is no overlap between two medians, then the medians are significantly different at a 95% confidence interval.

FIGURE 7. a) O. salmo holotype, Chesterfield, West Coast of South Island (photo: Jean-Claude Stahl). b), c) Live specimen of O. salmo, Chesterfield, South Island (photo: Dylan van Winkel).

FIGURE 8. a) Tail prehensility in subadult Oligosoma salmo sp. nov. (61 mm snout-vent; 4.05 g) (photo: Sabine Bernert). This has been observed in many individuals of this species - all those with intact or largely intact tails which have been tested. The grip of the tail on the finger was felt as very firm. b) In this individual (subadult male; 67 mm snout-vent, 6.19 g) the strength of the muscle contraction is shown by the formation of longitudinal ridges in the dorsal scales of the tail, which are normally completely smooth (photo: Lynn Adams).