Oligosoma roimata, Patterson, Geoff B., Hitchmough, Rod A. & Chapple, David G., 2013

Patterson, Geoff B., Hitchmough, Rod A. & Chapple, David G., 2013, Taxonomic revision of the ornate skink (Oligosoma ornatum; Reptilia: Scincidae) species complex from northern New Zealand, Zootaxa 3736 (1) : -

Oligosoma roimata sp. nov.

Figure 3

Sphenomorphus pseudornatus: McCann 1955 (in part): 76-7, 110-11, 125. Cyclodina ornata: Hardy 1977 (in part): 261-64.

Cyclodina sp. 3: Jewell 2008: 112.

Oligosoma ornatum: Chapple et al. 2009 (in part): 472, 485.

Holotype. Aorangi Island, Poor Knights (35º 28’S, 174º 44’E), NMNZ RE001626#32 (adult male) (coll. G.S. Hardy, November 1973). ( Figure 3 ).

Paratypes (4 specimens). Aorangi Island, Poor Knights (35º 28’S, 174º 44’E), NMNZ RE003723 (S78) (male) (coll. Coll. A.H. Whitaker, December 1964); Aorangi Island, Poor Knights (35º 28’S, 174º 44’E), NMNZ RE001626#29 (female), NMNZ RE001626#30 (male), NMNZ RE001626#31 (male) (coll. G.S. Hardy, November 1973).

Diagnosis. Oligosoma roimata sp. nov. can be distinguished from other Oligosoma species through a combination of characters. The clearly visible orange iris separates the species from all other Oligosoma except O. aeneum , O. levidensum , O. hardyi , O. townsi , O. oliveri , O. macgregori , O. whitakeri , O. striatum , O. homalonotum , and O. ornatum . The unbroken subocular scale row separates O. roimata sp. nov. from O. striatum , O. homalonotum .and O. hardyi . Oligosoma roimata sp. nov. has a prominent teardrop marking under the eye, and a moderately large ear opening, which separates it from O. aeneum , O. levidensum and O. hardyi which lack this marking and have small ear openings. Oligosoma townsi midbody scale count of ≥38 does not overlap with O. roimata sp. nov..

The maximum SVL of 62 mm (Whitaker 1968) is much less than that of O. oliveri (105.6 mm), the ear opening is smaller than in O. oliveri and most O. oliveri specimens have two primary temporals (Chapple et al. 2008a), whereas O. roimata sp. nov. always has one. There is minimal overlap between O. roimata sp. nov. and O. whitakeri in midbody and no overlap in ventral scale counts with O. whitakeri having a higher range for both indices (Hardy 1977). Oligosoma roimata sp. nov. lacks the yellow and orange colouration of many O. whitakeri specimens (Hardy 1977). Oligosoma whitakeri generally has dark blotches on the ventral surface, whereas it is unmarked or lightly marked in O. roimata sp. nov.. Colour pattern distinguishes O. roimata sp. nov. from O. macgregori and there is no overlap in midbody or ventral scale counts between these two species. The ear opening is slightly smaller than in O. ornatum and the maximum SVL is much less than O. ornatum (84.0 mm).

Description of Holotype. Body elongate, squarish in cross-section; limbs moderately well-developed, pentadactyl. Lower eyelid with a large, sometimes divided opaque central scale, bordered anteriorly and posteriorly by relatively large scales. Snout moderately blunt. Nostril centred just below middle of nasal, not touching bottom edge of nasal. 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, the second largest. Preoculars 2, the upper one larger. Frontoparietals distinct, larger than interparietal. A pair of parietals meeting behind interparietal and bordered posteriorly by a pair each of nuchals and temporals, also in contact with interparietal, frontoparietal, fourth supraocular and 2 postoculars. Loreals 2, similar size; anterior loreal in contact with first and second supralabial, posterior loreal, prefrontal, frontonasal and nasal; posterior loreal in contact with second and third supralabial, first subocular, upper and lower preocular, prefrontal and anterior loreal. Supralabials 7, the sixth largest. Infralabials 6, several of them equal in size; fifth supralabial below centre of eye. Mental broader but shallower than rostral. Suboculars series continuous. Postmental larger than mental. Chinshields 3 pairs. One primary temporal. Dorsal scales largest, weakly striate. Ventral scales smooth. Subdigital lamellae smooth.

Ear opening round, moderately large, with no projecting granules. Forelimbs shorter than hindlimbs. Adpressed limbs almost meeting in adult. Digits short, sub-cylindrical. Third front digit shorter than the fourth.

Measurements (in Millimeters; Holotype with the Variation Shown in the Type Series in Parentheses): SVL 57.0 (mean 57.0, range 48.5–63.6), HL 8.3 (mean 8.7, range 8.1–9.2), HW 6.1 (mean 6.1, range 6.4–6.5), AG 31.0 (mean 28.3, range 21.7–33.2), SF 23.9 (mean 23.0, range 21–24.8), S-E 11.7 (mean 11.3, range 9.6–12), EF 12.9 (mean 12.1, range 10.5–13.5), and TL incomplete (no specimens with intact tails).

Scalation (Holotype with the Variation Shown in the Type Series in Parentheses): Upper ciliaries 7 (mean 6, range 6-7); lower ciliaries 11 (mean 10, range 10–11); nuchals 1 pair (mean 1 pair, range 1-1 pairs); midbody scale rows 34 (mean 33, range 32–34); ventral scale rows 68 (mean 69, range 65–72); subdigital lamellae 24 (mean 22, range 21–24); supraciliaries 7 (mean 7, range 7-7); suboculars 9 (mean 9, range 8–9). Frontonasal never separated from frontal by prefrontals meeting in midline. Anterior loreal in contact with first and second supralabial. Posterior loreal in contact with second and third supralabial. Supralabials 7, the sixth largest. Infralabials 6. One primary temporal. Third front digit usually shorter than the fourth. Maximum SVL 63.6 mm. Ratios for morphological measurements (± SD): AG/SF 1.23 ± 0.14; SE/EF 0.94 ± 0.05; HL/HW 1.41 ± 0.05.

Colouration. Dorsal surface light brown to very dark brown, with irregular dark and light flecks or blotches, shading into white ventral surface ( Figure 4 ). A white, black-edged “tear-drop” under eye, although this may be indistinct in some animals. Well marked pale dorsolateral stripe from near tip of snout to near midpoint of body, thereafter broken up by brown patches. Throat, chin and belly lightly speckled. There do not appear to be sexually dimorphic colour patterns. Juvenile colouration is unknown.

Etymology. From the Maori “ roimata ” = “tears”, referring to the teardrop marking under the eyes. The suggested common name is the Aorangi skink.

Habitat and life history. Oligosoma roimata sp. nov. is known only from the Poor Knights Islands, which are an island chain just over 20 km NE of the northern North Island. They consist of two large islands (larger than 1 km 2) and several smaller islands and rock stacks. In total, the group is approximately 2.8 km 2 in area. The Poor Knights Islands are administered by the Department of Conservation as a Nature Reserve.

The islands are unique in that they have never been invaded by introduced mammalian predators. The exception is Aorangi Island, onto which Maori introduced feral pigs from stock obtained from European ships toward the end of the eighteenth century. The pigs were extirpated in 1936. Consequently, the Poor Knights Islands support a diverse range of reptile species, which can attain extremely high densities compared to mainland populations. The islands are now known to have three endemic lizard species; Oligosoma roimata sp. nov., the Poor Knights gecko ( Dactylocnemis sp.) and Hardy’s skink ( O. hardyi ). They also support populations of marbled skink ( O. oliveri ) which have a highly distinctive morphology, egg-laying skink ( O. suteri (Boulenger, 1906)) , moko skink ( O. moco (Dumeril & Bibron, 1839)) , shore skink ( O. smithi (Gray, 1845)) and Duvaucel’s gecko ( Hoplodactylus duvaucelii (Dumeril & Bibron, 1836)) .

Oligosoma roimata sp. nov. is most abundant in flax and scrub on the fringes of the islands. It appears to favour dense ground cover. It is most active at dawn and dusk and appears to be mainly insectivorous (Whitaker 1968). The species is currently listed in the New Zealand Threat Classification System as Naturally Uncommon (Hitchmough et al. 2013); however, since population densities appear to be sparse and several recent surveys have failed to detect any animals (Trent Bell, pers. comm.; R. Parrish, pers. comm.), the species may warrant an enhanced conservation status.

Figures

FIGURE 3. Aorangi skink (O. roimata sp. nov.) holotype (RE 001626 # 32).

FIGURE 4. Aorangi skink (O. roimata sp. nov.) in habitat. Photograph: Colin Miskelly.