Acontias albigularis, Conradie & Busschau & Edwards, 2018

Conradie, Werner, Busschau, Theo & Edwards, Shelley, 2018, Two new species of Acontias (Acontinae, Scincidae) from the Mpumalanga Highveld escarpment of South Africa, Zootaxa 4429 (1), pp. 89-106 : 95-98

Acontias albigularis sp. nov.

Suggested common name: White-throated Legless Skink

Fig. 5A , 6A , 7A

Synonym. Acontias breviceps— FitzSimons (1943); Broadley & Greer 1969 (part); Branch 1988, 1994, 1998 (part); Bates et al. 2014 (part).

Holotype. PEM R20655 , Mauchsberg, Long Tom Pass , Mpumalanga, South Africa (- 25.14113 S 30.60522 E, 2530BA, 2149 m above sea level ~ asl) collected by Werner Conradie, Theo Busschau and Adriaan Jordaan on 9 December 2013. Mid ventral incision, otherwise in good condition.

Paratypes (12). PEM R20650-2, 20661, Top of Long Tom Pass, Mpumalanga, South Africa (-25,149109 S 30.61938 E, 2530BA, 2206 m asl); PEM R20653-4, 20656-60, 20662, Mauchsberg, Long Tom Pass, Mpumalanga, South Africa (-25.14113 S 30.60522 E, 2530BA, 2149 m asl). All voucher specimens collected by Werner Conradie, Theo Busschau and Adriaan Jordaan on 9 December 2013. All material are adults except for PEM R20651-3 being juveniles. All voucher specimens with mid-ventral incisions and in otherwise good condition.

Additional material examined (9). The following additional material was used to expand the description of variation within the species: TM 56267, 61770, 61200 (Farm De Kuilen); TM 56289 (Mauchesberg); PEM R5139 (Sabie); PEM R16668, 16674, 20937-8 (Long Tom Pass).

Diagnosis. A medium sized legless skink assigned to the genus Acontias (part) based on the body being moderately attenuate, snout not strongly acutely angled, movable eyelids present, lower eyelid immovable, and overall genetic placement ( Lamb et al. 2010; this study). Distinguished from A. jappi (Broadley) , A. kgalagadi (Lamb, Biswas & Bauer) , A. lineatus Peters (previously included in Typhlosaurus ), and A. schmitzi Wagner, Broadley & Bauer in possessing moveable eyelids. It can be distinguished from other congeners possessing moveable eyelids by: ventral pigmentation concentrated at posterior scale margins giving a checkered appearance (all species except A. breviceps and A. sp. 2) compared to dorsally and ventrally uniform ( A. plumbeus , A. occidentalis (part)) or no ventral pigmentation ( A. gracilicauda , A. meleagris complex, A. lineicauda , A. occidentalis (part), A. namaquensis , and A. percivali Loveridge ). It can be distinguished from typical A. breviceps and A. sp. 2 by the lack of pigmentation in the region around the throat and the cloaca, and lower average number of scales around the midbody (14 scales vs 16 in both A. breviceps and A. sp. 2). It differs from A. breviceps in that the second upper label is touching the eye 17 out of 19 (90%) times (vs 1 out of 39 ~5%). In the phylogenetic analysis, it is sister to A. gracilicauda , from which it differs by 2.2 ± 0.6 % (16S mtDNA) and 3.5 ± 0.7 % (Cytb mtDNA) sequence divergence. It further differs 5.3 ± 1.2 % (16S) and 7.0 ± 0.9 % (Cytb) from A. breviceps , and 2.1 ± 0.8 % (16S) and 3.6 ± 0.7 % (Cytb) from. A. sp. 2.

Description of Holotype. A medium sized Acontias species with a total length of 197.1 mm (166 mm SVL; 31.1 mm TL). Body cylindrical, slightly flattened dorsally (probably an artefact of preservation). Head short (13% SVL) and narrow (HW 7.0 mm). Snout rounded and very short. Large rostral with the nostril pierced in the anterior part, connected with the border of the rostral by a straight, narrow suture. Three supraoculars present, first much larger than other. Four supracilliars, 1 st largest and 3rd smallest. Ocular exposed. Four upper labials present, the second upper labial narrowly excluded from the ocular, the third and fourth well excluded from ocular by three suboculars. Three lower labials. Loreal large, in contact with the first upper labial ventrally, the rostral dorsally and preocular anteriorly. Dorsally, the rostral is followed by two enlarged head scales (prefrontal and frontal). Prefrontal large and subrectangular in shape, frontal more or less pentagonal, larger than the prefrontal and posteriorly bordered by two large parietal scales separated by an interparietal. The two parietal scales in contact anteriorly and running more or less parallel on their sides. Two narrow longitudinal scales bordering the two parietal scales. The pineal eye is pierced in the posterior part of the interparietal scale. Mental large, bordered by three chin shields and one lower labial on each side of the head. Body scales homogeneous (except in size and shape—see below) and smooth in 14 rows around midbody (16 front, 14 middle, 12 anterior), 153 longitudinal scale rows (from chin shield to precloacal scale), and 34 subcaudal scales. The vertebral row of scales on the nape is equal in size, but posteriorly becoming noticeably broader. The median row of ventral subcaudals is strongly broadened. The first 6 subcaudal scales are split, after which the broadened scale runs all the way to the tail tip. The mid tail scale row count is seven. The vertebral count is 71 + 22 (trunk + tail) ( Fig. 7A ).

Colouration in life. Dorsally olive to olive brown in colour, with the terminal ends of the scales spotted with dark brown to black. Ventrally lighter olive-yellow, with scales spotted, throat region and around cloaca free of any pigmentation.

Variation: SVL range from 70-195 mm; TL varies from 15-40 mm; HL varies from 5.7-14.9 mm; HW varies from 3.7-7.7 mm; midbody scale rows vary from 14-16 (mostly 14), ventrals vary from 146-159; subcaudals vary from 33-39; vertebrae (body) = 68-73; vertebrae (tail) = 21-28. Table 1 further summarises the measurements and scalation. In juvenile specimens (PEM R20651-3), the ventral pigmentation is not as prominent as in adults. Different degrees of ventral pigmentation exist among adults, but mostly the ventral third of the body and around the cloaca are unpigmented. Dorsally all scales are punctuated anteriorly.

Etymology. The name albigularis is derived from the Latin words: albi (white) and gula (throat), and alludes to the unpigmented gular or throat region of the species, giving it a white throat.

Habitat. Found in montane grassland under large flat rocks on the Mpumalanga escarpment at an altitude above 2000 m asl.

Breeding. Currently unknown. A juvenile measuring 85 mm total length was collected from Long Tom Pass in December 2013, which indicates that they were born earlier that same season. This suggests that breeding likely takes place in the summer months from September onwards.

Distribution and conservation. Currently only known from the Mpumalanga escarpment. We assign the following historical records to A. albigularis sp. nov.: Farm De Kuilen (TM56267, TM61770, TM61200); Farm Paardeplaats (TM61771); Long Tom Pass (PEM R16668, PEM R16674); Mauchsberg (TM56289); Sabie (PEM R5139); Mauchsberg, Mt. Anderson, Tafelkop 26HT ( Jacobsen 1989).

Figures

FIGURE 5. Four species of Acontias in life. (A) Acontias albigularis sp. nov. (PEM R20662) from Long Tom Pass, Mpumalanga Province. (B) Acontias breviceps (PEM R19010) from Hogsback, Eastern Cape Province. (C) Acontias gracilicauda (PEM R20170) from Groendal, Eastern Cape Province. (D) Acontias wakkerstroomensis sp. nov. (holotype - PEM R22788) from near Wakkerstroom, Mpumalanga Province.

FIGURE 6. Dorsal and ventral photos of the holotypes/lectotypes of the four species of Acontias discussed in this study. (A) Acontias albigularis sp. nov. PEM R20655 from Long Tom Pass, Mpumalanga Province. (B) Acontias breviceps PEM R5570 from Hogsback, Eastern Cape Province. (C) Acontias gracilicauda PEM R5131 from Grahamstown, Eastern Cape Province. (D) Acontias wakkerstroomensis sp. nov. PEM R22788 from near Wakkerstroom, Mpumalanga Province. Scale bar = one centimeter.

FIGURE 7. X-rays of the five species of Acontias discussed in this study. (A) Acontias albigularis sp. nov. PEM R20658. (B) Acontias breviceps PEM R18912. (C) Acontias gracilicauda PEM R20214. (D) Acontias wakkerstroomensis sp. nov. PEM R22788. (E) Acontias meleagris PEM R2507.