Sphenomorphus yersini, Nguyen & Nguyen & Nguyen & Orlov & Murphy, 2018

Nguyen, Sang Ngoc, Nguyen, Luan Thanh, Nguyen, Vu Dang Hoang, Orlov, Nikolai L. & Murphy, Robert W., 2018, A new skink of the genus Sphenomorphus Fitzinger, 1843 (Squamata: Scincidae) from Hon Ba Nature Reserve, southern Vietnam, Zootaxa 4438 (2), pp. 313-326 : 315-323

Sphenomorphus yersini sp. nov.

( Figs. 1–4 )

Holotype. ITBCZ 5685 , adult male, collected from Hon Ba NR., Khanh Hoa Province, Vietnam; coordinates 12°8’13”N, 108°57’39”E; elevation 1162 m a.s.l. by L.T. Nguyen, V.D.H. Nguyen, and S.N. Nguyen on 16 October 2016 ( Fig. 1 ).

Paratypes. Two specimens, also collected from Hon Ba NR by L.T. Nguyen, V.D.H. Nguyen, and S.N. Nguyen: ITBCZ 5686, adult female ( Fig. 2C&D ), and ITBCZ 5684, adult male ( Figs. 2A&B and 3 ), collected on 14 October 2016, coordinates 12°8’22”N, 108°58’06”E; elevation 932 m a.s.l.

Referred specimen. HBA 44 (released, Fig. 4 ), adult female, collected on 19 October 2016, coordinates 12°8’22”N, 108°58’06”E; elevation 932 m a.s.l.

Diagnosis. Sphenomorphus yersini sp. nov. is distinguished from all of its congeners by a combination of the following morphological characters: size in adults (SVL) up to 56 mm; TaL/SVL ratio 1.81; toes reach to fingers when limbs adpressed; 32–34 smooth midbody scale rows; 61–69 paravertebral scales; 58–67 ventral scale rows; 112 subcaudal scales; four, rarely five, supraoculars; prefrontals in broad contact with one another; two loreal scales; tympanum deeply sunk; smooth lamellae beneath Finger IV and Toe IV 10–12 and 18 –20, respectively; two enlarged precloacal scales; hemipenis smooth, deeply forked, asymmetrical with a long lobe and another short; black and interruptive dorsolateral line; lateral side and lower part of head, neck, and tail orange to red in male.

Description of holotype. Adult male; head small and elongate (HW/HL = 0.7); SVL 54 mm; tail long (TaL/ SVL = 1.81), 98 mm in length; lower eyelid scaly; tympanum deeply sunk with a prominent oblique edge; limbs pentadactyl, toes reach to fingers when limbs adpressed.

Head scalation smooth; rostral convex, distinctly visible from above, in broad contact with frontonasal, which is broader than long; no supranasals; prefrontals in broad contact with one another; 5 supraoculars on left side and 4 on right side; a pair of frontoparietals, shorter than frontal; frontal narrowing posteriorly, longer than wide, bordered laterally by first two supraoculars, anteriorly by prefrontals, and posteriorly by frontoparietals; frontoparietals in contact with the second to fifth supraoculars on left side and the second to fourth supraoculars on right side; parietals in contact posteriorly, behind the interparietal; no nuchal; 7 supralabials on both sides, the fifth and sixth below the eye; 2 loreals, posterior loreal larger than anterior; nostril in center of nasal, which is in contact with the first supralabial, rostral, anterior loreal, and frontonasal; 8 supraciliaries, first largest; 1 anterior temporal, in contact with sixth and seventh supralabials; 2 secondary temporals, lower temporal overlapping upper one and in contact with seventh supralabial, upper temporal larger, in contact with parietal; lower eyelid scaly, 2 scales in center larger than scales in posterior and anterior areas; 6 infralabials, first pair medially in contact with each other; 1 anterior and 2 postmentals.

Dorsal scales smooth, not larger than lateral and ventral scales; 34 midbody scale rows; 61 paravertebral scales; ventral scales smooth, in 60 rows; 112 subcaudal scales, slightly enlarged posteriorly; 11 and 20 smooth lamellae beneath finger IV and toe IV, respectively; 2 enlarged precloacal scales.

Hemipenes. Each hemipenis deeply forked and asymmetrical with two smooth lobes. In fully everted position, the inner lobe is shorter and the outer lobe is much longer. Clear sulcus spermaticus starts from the base, divides into two branches at the fork and extends to the tips of the two lobes; body of the long lobe forming regular transversal shallow grooves and ending with terminal papillae. Short lobe obtuse, not forming regular transversal shallow grooves ( Fig. 1F ).

Coloration. In life, overall dorsal coloration black (Hex #000000) to dark brown (Hex #654321) with two interrupted copper (Hex #B87333) dorsal lines in margins of dorsum extending from neck to base of tail; black and interrupted lateral lines under the copper ones; dorsum with irregular black spots; lateral side and lower part of head, neck, and tail orange (Hex #FF6600) to red (Hex #FE2712); venter from chest to tail base yellow (Hex #FFD300) to cream (Hex #FFFDD0); upper side of limbs black with bright dots. Lateral margins of supralabials and infralabials with black blotches. Free margin of upper eyelid orange and the margin of lower eyelid yellow (Hex #FFD300). Eyes black. In preservation, color fades; orange and yellow disappear; overall dorsal coloration black with two interrupted brighter lines in margins of dorsum extending from neck to base of tail; venter zebra white (Hex #F5F5F5).

Variation. Table 2 summarizes variation in size and scalation of the holotype, paratypes, and referred specimen. Supraoculars four in all specimens except for the left side of the holotype which bears 5 scales. Midbody scale rows vary from 32 to 34. Paravertebral and ventral scale rows range from 61 to 69 and from 58 to 67, respectively. Hemipenes of the second paratype ITBCZ 5684 ( Fig. 3 ) similar to those of the holotype in being deeply forked and asymmetrical.

Natural history. All specimens were collected at night and under rotting leaf layer in evergreen forest ( Fig. 5 ), elevations 932 m and 1162 m a.s.l., between 19:00–23:30. However, the species was observed being active in the daytime and it may be diurnal. Sphenomorphus yersini sp. nov. was observed to be sympatric with other congener, S. indicus .

Sexual dimorphism. Males are larger than females (SVL 56 mm vs. 52 mm, n=4) and have orange (Hex #FF6600) or red (Hex #FE2712) color on lateral sides and lower part of head, neck, and tail. The color on the lateral side in females faded to yellow (Hex #FFD300) or brown (Hex #964B00) with bright spots; lower part of head, limbs, and tail white (Hex #FFFFFF) to zebra white (Hex #F5F5F5); venter from neck to vent yellow (Hex #FCE883).

Distribution. The new species is currently known only from Hon Ba NR, Khanh Hoa Province, southern Vietnam ( Fig. 5 ).

Etymology. We name this new species in honor of the famous physician and bacteriologist, Alexandre Yersin (1863–1943), who discovered the bacterium responsible for bubonic plague. Hon Ba NR associates with the name of Alexandre Yersin who built a research station on the top of the mountain and worked there. Currently, the research station has been reconstructed and opened to visitors. We recommend Yersin’s Forest Skink as the common name of this new species.

Comparisons. Sphenomorphus yersini sp. nov. differs from its congeners in Indochina ( Vietnam, Laos, Cambodia, Thailand, Myanmar, Peninsular Malaysia, and southern China [Yunnan]) as follows: from S. anomalopus (Boulenger) by having a smaller size (SVL 50–56 mm vs. 70 mm), fewer midbody scale rows (32–34 vs. 38) and more lamellae beneath toe IV (18–20 vs. 14); from S. bacboensis by having one (vs. two) anterior temporal, more midbody scale rows (32–34 vs. 30–32), and more supralabials (7 vs. 6); from S. cameronicus Smith by having a smaller size (SVL 50–56 mm vs. 70 mm) and fewer midbody scale rows (32–34 vs. 38); from S. cophias Boulenger by having a larger size (SVL 50–56 mm vs. 37 mm), more midbody scale rows (32–34 vs. 24), more lamellae under fourth toe (18–20 vs. 9) and prefrontals in broad contact (vs. separated); from S. cryptotis by having a smaller size (SVL 50–56 mm vs. 58–79 mm), fewer midbody scale rows (32–34 vs. 36–39) and tympanum deeply sunk (vs. superficial); from S. grandisonae Taylor by having a larger size (SVL 50–56 mm vs. 30 mm), one (vs. two) anterior temporal, more supralabials (7 vs. 6) and lamellae under toe IV (18–20 vs. 12), and adpressed limbs overlapping (vs. failing to touch); from S. helenae Cochran by having more midbody scale rows (32–34 vs. 30), prefrontals in broad contact (vs. separated), and presence of an interrupted (vs. uninterrupted) lateral stripe; from S. incognitus by having a smaller size (SVL 50–56 mm vs. 80–103 mm), fewer midbody scale rows (32–34 vs. 36–40), and one (vs. two) anterior temporal; from S. indicus by having a smaller size (SVL 50–56 mm vs. 90 mm), prefrontals in broad contact (vs. separated), and asymmetrical and deeply forked hemipenis (vs. symmetrical); from S. lineopunctulatus Taylor by having a smaller size (SVL 50–56 mm vs. 84 mm), fewer midbody scale rows (32–34 vs. 38), fewer paravertebral scale rows (61–69 vs. 76), and prefrontals in broad contact (vs. separated); from S. maculatus by having a smaller size (SVL 50–56 mm vs. 62 mm), fewer midbody scale rows (32–34 vs. 38–42), and prefrontals in broad contact (vs. separated); from S. malayanum by having fewer ventral scales (32–34 vs. 74), fewer paravertebral scales (61–69 vs. 76–80), more lamellae under fourth toe (18–20 vs. 15), and deeply sunk (vs. shallow) tympanum; from S. mimicus by having a larger size (SVL 50–56 mm vs. 36 mm), more midbody scale rows (32–34 vs. 30) and more lamellae under fourth toe (18–20 vs. 16); from S. orientale (Shreve) by having more midbody scale rows (32–34 vs. 24–26) and fewer paravertebral scale rows (61– 69 vs. 69–71); and from S. praesignis (Boulenger) by having a smaller size (SVL 50–56 mm vs. 109 mm) and more midbody scale rows (32–34 vs. 28). Sphenomorphus yersini sp. nov. differs from S. sanctus (Duméril & Bibron) by having a larger size (SVL 50–56 mm vs. 40–45 mm), fewer paravertebral scales (61–69 vs. 71), fewer supraoculars (4[5] vs. 5), and fewer lamellae under toe IV (18–20 vs. 26–27); from S. scotophilus (Boulenger) by having more midbody scale rows (32–34 vs. 28–31), fewer supraoculars (4 vs. 5), and fewer lamellae under fourth toe (18–20 vs. 22–23); from S. senja Grismer & Quah by having a smaller size (SVL 50–56 mm vs. 60–65 mm), fewer paravertebral scales (61–69 vs. 72–73), fewer ventral scale rows (60–67 vs. 68), one (vs. two) anterior temporal, more lamellae under toe IV (18–20 vs. 13–17) and prefrontals in broad contact with each other (vs. narrow in contact or slightly separated); from S. sheai by having a larger size (SVL 50–56 mm vs. 35 mm), more midbody scale rows (32–34 vs. 20), more paravertebral scales (61–69 vs. 53), more supralabials (7 vs. 6), more lamellae under fourth toe (18–20 vs. 6), and adpressed limbs overlapping (vs. separated); from S. shelfordi ( Boulenger 1900) by having a smaller size (SVL 50–56 mm vs. 67 mm), fewer lamellae under toe IV (18–20 vs. 28–29) and the absence of nuchals (vs. presence of a single pair of nuchals); from S. stellatus by having a smaller size (SVL 50–56 mm vs. 80 mm), more midbody scale rows (32–34 vs. 24) and absence (vs. presence) of two enlarged, broader than long, vertebral scale rows; from S. sungaicolus Sumarli, Grismer, Wood, Ahmad , Rizal, Ismail, Izam, Ahmad & Linkem by having a smaller size (SVL 50–56 mm vs. 67–90 mm), fewer midbody scale rows (32–34 vs. 39–44), fewer paravertebral scales (61–69 vs. 72–81) and fewer ventral scale rows (32–34 vs. 74–86); from S. tarsus (Smith) by having a smaller size (SVL 50–56 mm vs. 90–92 mm) and two loreals (vs. three); from S. tetradactylus by having more midbody scale rows (32–34 vs. 20), absence (vs. presence) of external ear opening, and forelimb with five digits (vs. four digits); from S. tonkinensis by having a larger size (SVL 50–56 mm vs. 36–49 mm), TaL/ SVL ratio 1.80 (vs. 1.32), and one (vs. two) anterior temporal; from S. tridigitus by having a larger size (SVL 50– 56 vs. 35), more midbody scale rows (32–34 vs. 20), absence (vs. presence) of external ear opening and forelimb with five digits (vs. three digits); and from S. tritaeniatus by having a larger size (SVL 50–56 vs. 47), fewer midbody scale rows (32–34 vs. 38) and paravertebral scales (61–69 vs. 81), more lamellae under toe IV (18–20 vs. 15) and one anterior temporal (vs. two).

Sphenomorphus yersini sp. nov. is similar to S. buenloicus in many aspects (size, midbody scale rows, number of anterior temporals, lamellae under fourth toe, etc.). However, the new species can be distinguished from S. buenloicus by having a relatively longer tail (TaL/SVL ratio 1.8 vs. 1.2), usually more ventral scale rows (58–67 vs. 55–58) and deeply forked hemipenis with two asymmetrical lobes and the outer lobe is much longer than the inner one (vs. hemipenis forked at the middle point of its length with two developing lobes and the outer lobe is slightly longer than the inner one [ Figs. 6 & 7 ]).

Figures

FIGURE 1. Holotype of Sphenomorphus yersini sp. nov., ITBCZ 5685. A, dorsolateral view; B, ventral view; C&D, dorsal and lateral views of head; E, lower eyelid scaly; F, two asymmetrical hemipenes in preservation.

FIGURE 2. Paratypes of Sphenomorphus yersini sp. nov. A&B, ITBCZ 5684, male; C&D, ITBCZ 5686, female. Scales in lower eyelid can be observed in figures B and D.

FIGURE 3. Hemipenes of paratype ITBCZ 5684 of Sphenomorphus yersini sp. nov. A&B, sulcate and asulcate views of the right hemipenis, respectively (fresh); B&C, asulcate and sulcate views of left hemipenis, respectively (fresh); E&F, the two hemipenes in preservation.

FIGURE 4. Released referred specimen HBA 44 of Sphenomorphus yersini sp. nov. A–C, living specimen; D–H, midbody scale rows illustrated and checked via detail photos. Photographs detail five parts. Red spots are marks on midbody; blue dots illustrate counting of 33 longitudinal scale rows.

FIGURE 5. Map (left) showing the type locality (red dot) of Sphenomorphus yersini sp. nov. in southern Vietnam and habitat (right) of the new species in Hon Ba Nature Reserve.

FIGURE 6. Examined specimens of Sphenomorphus buenloicus. A–C, holotype, ZISP 19795, hemipenes in C showing forked points near the tips of the organs; D, ITBCZ 5060 (upper) and ITBCZ 4357 (lower); E&F, lateral views of ITBCZ 5060 and ITBCZ 4357, respectively.

FIGURE 7. Additional specimen (ITBCZ 6027) of Sphenomorphus buenloicus from Tram Lap Forest, Gia Lai Prov. showing the fully everted hemipenes. A, living specimen; B, hemipenes under not in fully everted condition (note that this is similar to the condition of the holotype’s hemipenes in figure 6C); C&D, sulcate and asulcate views of the right hemipenis, respectively.