Tytthoscincus monticolus, Grismer & Wood Jr & Ahmad & Baizul-Hafsyam & Afiq-Shuhaimi & Rizal & Quah, 2018

Grismer, L. Lee, Wood Jr, Perry L., Ahmad, Amirrudin B., Baizul-Hafsyam, B. S., Afiq-Shuhaimi, M., Rizal, Syed A. & Quah, Evan S. H., 2018, Two new Tytthoscincus Linkem, Diesmos, & Brown (Squamata; Scincidae) from Peninsular Malaysia and another case of microsyntopy between ecologically specialized, unrelated, leaf-litter species, Zootaxa 4425 (1), pp. 87-107 : 98-100

Tytthoscincus monticolus sp. nov.

Suggetsed common names: Sungai Bubu Forest Skink and Mengkarung Hutan Sungai Bubu

( Fig. 6 )

Holotype. Adult male ( LSUHC 13858 ) collected from a hilly area near Sungai Bubu, Sekayu, Hulu Terengganu, Terengganu State, Peninsular Malaysia (4.9710° N, 102.9531° E; 174 m in elevation) by M. Afiq-Shuhaimi and Baizul-Hafsyam B. S. on 5 August 2017.

Diagnosis Tytthoscincus monticolus sp. nov. can be differentiated from all other species of Tytthoscincus in the upland clade by having the combination of 8`1, superciliaries; a deeply set, unpigmented tympanum; enlarged pectoral scales; 31 midbody scale rows; 69 paravertebral scales; 68 ventral scales; keeled, subdigital lamellae; seven subdigital lamellae on the third finger; 12 subdigital lamellae on the fourth toe; EO/HL = 0.16; HL/SVL = 0.17; AXG/SVL = 0.55; FL/SVL = 0.22; HDL/SVL = 0.33; and a maximum SVL of 36.6 mm (Tables 5,6). All characters are scored across all other Tytthoscincus and species of Sphenomorphus suspected of being Tytthoscincus in Grismer et al. (2016a:237) and Karin et al. (2016:416).

Description of holotype. Adult male, SVL 36.6 mm; regenerated tail length 29.4 mm; axilla-groin length 20.0 mm; head length 6.4 mm; head width 3.8 mm; rostral wider than long, in broad contact with frontonasal; frontonasal wider than long; prefrontals large, in broad contact on midline; frontal elongate, triangular, in contact with first two supraoculars; four supraoculars; frontoparietals in contact posterior to frontal, contacting second, third, and fourth supraoculars anterolaterally and parietals and interparietal posteriorly; interparietal diamondshaped, large, slightly projecting posteriorly, eyespot in posterior projection; parietals large, in medial contact posterior to interparietal, contacting fourth supraocular anteriorly; six nuchal scales; nasals small, widely separated, trapezoidal, contacting rostral anteriorly, frontonasal dorsally, loreal posteriorly, first supralabial ventrally; nostril in center of nasal; supranasals absent; loreal single; upper and lower preocular present; lower preocular followed by a series of seven suboculars; eight superciliaries, posterior superciliary elongate and projecting dorsomedially; two postoculars; one postsuperciliary; six supralabials, third, fourth, and fifth below eye; two postsupralabials; two primary temporals; four secondary temporals, uppermost contacting parietal; lower eyelid transparent, scaly, no enlarged central window; mental twice as wide as long; single, large postmental, contacting first infralabial on each side; two enlarged pairs of chin shields posterior to postmental, anterior pair contacting medially, posterior pair widely separated posteriorly by a single scale; anterior and posterior chinshield pairs contacting first, second, and third infralabials; five infralabials; external ear opening 1.0 mm, circular, lacking anterior lobules; and tympanum deeply set, non-pigmented.

Body scales smooth, cycloid, imbricate; ventral scales slightly larger than dorsal scales; 31 longitudinal scale rows around midbody; 69 paravertebral scale rows; 68 ventral scale rows; slightly enlarged median precloacal scales overlapping outer precloacal scales; tail slightly compressed laterally; subcaudals slightly larger than dorsal caudals; limbs relatively robust, short (FL/SVL = 0.22; HDL/SVL = 0.33), widely separated when adpressed; scales of dorsal surfaces slightly larger than those of ventral and posterior surfaces; palmar and plantar scales raised; and digits moderate in length, scales on dorsal surfaces in single row, subdigital lamellae keeled, seven on third finger, 12 on fourth toe.

Coloration in life ( Fig. 6 ). Overall dorsal ground color of head, body, limbs, and tail dark-brown; hind limbs darker than forelimbs, both limbs mottled; top of head and body speckled with light-colored markings, those above the shoulder tending to coalesce to form a diffuse dull-orange stripe; supralabials and infralabials alternately banded with light and dark bars; dorsal portion of flanks dark, highlighting the light-colored dorsal spots; all ventral surfaces dull-yellow to beige, generally immaculate; distal portions of forelimbs and palmer surfaces dark; planter surface dark; and subcaudal region stippled with dark-brown.

Distribution. Tytthoscincus monticolus sp. nov. is known only from the type locality near the Sungai Bubu, Terengganu, Peninsular Malaysia ( Fig. 2 ), however, it is likely to range throughout the entire lowland system of the Sekayu region.

Natural history. The holotype of Tytthoscincus monticolus sp. nov. (LSUHC 13858) is a leaf-litter species inhabiting hilly areas along riparian systems in lowland dipterocarp forest ( Fig. 7 ) and was captured in a pitfall trap.

Etymology. The specific epithet monticolus , comes from the Latin monti meaning mountain and colus meaning dweller of or within and refers to this species inhabiting hilly areas.

Comparisons. Tytthoscincus monticolus sp. nov. is most closely related to T. perhentianensis ( Fig. 4 ) and differs from it by an uncorrected pairwise sequence divergence of 3.5%. It is differentiated from T. perhentianensis morphologically by having one vs. two loreal scales; 69 vs. 65 or 66 paravertebral scales; 68 vs. 61 or 62 ventral scales; seven vs. six subdigital lamellae on the third finger; and 12 vs. 10 subdigital lamellae on the fourth toe. It differs further by having a larger ear opening (0.16 vs 0.13–0.14 EO/HL); a shorter head (0.17 vs. 0.22–0.23 HL/ SVL); longer hind limbs (0.33 vs. 0.29–0.30 HDL/SVL); and a larger maximum SVL (36.2 mm vs. 30.0 mm: Table 6). It differs from T. keciktuek (see description below) with which it is likely syntopic by an uncorrected pairwise sequence divergence of 9.8% and having one vs. two loreals; 68 vs 60 ventral scale rows; a larger ear opening (0.16 vs 0.12 EO/HL); a shorter head (0.17 vs. 0.21 HL/SVL); shorter forelimbs (0.22 vs. 0.25 FL/SVL); shorter hind limbs (0.33 vs. 0.37 HDL/SVL); and a dorsal pattern bearing white speckling vs. being nearly unicolor ( Table 5; Fig. 6 ). Differences between T. monticolus sp. nov. and all other species of the upland clade are presented in Table 6.

Figures

FIGURE 2. Type localities for Tytthoscincus keciktuek sp. nov. and T. monticolus sp. nov. and their closest relatives T. perhentianensis and Tytthoscincus sp. nov., respectively, in Peninsular Malaysia.

FIGURE 4. Maximum Likelihood phylogram depicting the relationships of species within the montane clade of Tytthoscincus and the delimitation of the semi-fossorial and leaf-litter generalist lineages. Black circles denote nodal Bayesian support ± 0.95 and ultrafast bootstrap support ±95, grey circle denotes nodal Bayesian support ± 0.95 only, and the white circle denotes poor Bayesian and ultrafast bootstrap support.

FIGURE 6. Upper: type specimen (LSUHC 13858) of Tytthoscincus monticolus sp. nov. collected from a hilly area near Sungai Bubu, Sekayu, Hulu Terengganu, Terengganu State, Peninsular Malaysia. Photograph by A. B. Ahmad. Middle: type specimen (LSUHC 13859) of Tytthoscincus keciktuek sp. nov. collected along a small tributary of the Sungai Peres, Sekayu, Hulu Terengganu, Terengganu State, Peninsular Malaysia. Photograph by A. B. Ahmad. Lower: Tytthoscincus butleri (LUSHC 13860) from a new lowland locality at Bukit Mertajam, Penang, Peninsular Malaysia. Photograph by E.S.H. Quah.

FIGURE 7. Left: General habitat of Tytthoscincus monticolus sp. nov. and T. keciktuek sp. nov. from the Sekayu region of Hulu Terengganu. Photograph by L. L. Grismer. Upper right: microhabitat at the type locality of T. monticolus sp. nov. near Sungai Bubu, Sekayu, Hulu Terengganu, Terengganu State, Peninsular Malaysia. Photograph by M. Afiq-Shuhaimi. Lower right: microhabitat at the type locality of T. keciktuek sp. nov. from Sungai Peres, Sekayu, Hulu Terengganu, Terengganu State, Peninsular Malaysia. Photograph by M. Aqmal-Naser.