Lankascincus fallax ( Peters, 1860 )

Kanishka, A. Suneth, Danushka, A. Dineth, Hallermann, Jakob, Campbell, Patrick D., Mata, Joshua & Amarasinghe, A. A. Thasun, 2024, Systematics and distribution of Lankascincus fallax (Peters, 1860) (Reptilia, Scincidae), an endemic litter-skink from Sri Lanka, Zootaxa 5424 (1), pp. 99-115 : 104-110

Lankascincus fallax ( Peters, 1860)

( Figs. 3–6 , 8 ; Table 4)

Lygosoma fallax Peters, 1860

Lygosoma megalops Annandale, 1906

Sphenomorphus rufogulus Taylor, 1950

Lankascincus deraniyagalae Greer, 1991

Lankascincus deraniyagalae — Somaweera & Somaweera 2009

Lankascincus fallax — Greer 1991, Somaweera & Somaweera 2009, Batuwita 2019, Kanishka et al. 2020 Lankascincus megalops — Batuwita 2019 [partim], Kanishka et al. 2020 [partim]

‘ Lankascincus megalops ’— Amarasinghe et al. 2022a [partim]

Syntypes (n =2). An adult male, ZMB 3762 (SVL 38.1 mm) and A juvenile, ZMB 64361 (SVL not measured) collected from Trinkomalie (= Trincomalee , Eastern Province) and Ratnapura (Sabaragamuwa Province) by Prof. L.K. Schmarda, date unknown .

Description of the syntype, ZMB 3762. Male, SVL 38.1 mm. Head moderately large (HL 14.7% of SVL), wide (HW 98.2% of HL), indistinct from neck; snout short (ES 44.6% of HL, ES 44.6% of HW), shorter than orbit diameter (ES 96.1% of ED), slightly convex in lateral profile.

Rostral shield large, posterior margin convex in contact with frontonasal caudally; nasal non-fused, nostril large, no supranasal or postnasal scale; frontonasal larger than prefrontals, in contact laterally with anterior loreal; prefrontals separate from each other by connection of frontonasal with frontal, in contact with anterior and posterior loreals laterally, 1 st supraciliary, 1 st supraocular and frontal posteriorly; frontal longer than frontonasal and prefrontal combined, shorter than fused (single) frontoparietal and interparietal length combined; supraoculars four, 1 st longer than width in longitudinal axis, 2 nd wider than length in longitudinal axis, first two supraoculars in contact with frontal, 3 rd in contact with frontoparietal, 4 th in contact with frontoparietal, parietal, upper pretemporal and last supraciliaries; frontoparietals fused, larger than interparietal, in contact with 2 nd –4 th supraoculars; parietals large, touching each other behind interparietal, in contact with 4 th supraocular and upper pretemporal anteriorly, upper secondary temporal and body scales laterally; loreals two, anterior loreal touching prefrontal, frontonasal, nasal, 1 st and 2 nd supralabial, and posterior loreal; posterior loreal larger than anterior loreal, touching prefrontal, anterior loreal, 2 nd supralabials, two preoculars, and 1 st supraciliary; preoculars two, lower preocular larger, touching upper preocular, posterior loreal, 3 rd supralabial and palpebral scales; eye large, orbit diameter smaller as tympanumeye length, ED 74.2% of TYE, pupil rounded; interorbital distance broad, IO 66.0% of HW; supraciliaries eight (nine on right side), placed between supraocular and upper palpebrals; upper palpebrals 15, placed between eye and supraciliary row; lower palpebrals 16, placed between eye and subocular row; suboculars eight, smaller than supralabials, touching 3 rd –6 th supralabials ventrally, lower postoculars, primary temporals, and lower pretemporal scale posteriorly; last subocular touching lower and upper primary temporal, lower pretemporal, lower anterior and posterior postoculars; anterior postoculars two, upper one larger than lower; posterior postoculars two, subequal to anterior postoculars in size, touching pretemporals; pretemporals two, lower pretemporal larger than upper, touching parietals, upper primary temporal and upper secondary temporals; primary temporals two, upper one larger and in contact with secondary temporals; lower primary temporal touching 7 th –8 th suboculars, 6 th and 7 th supralabials; upper primary temporal touching last upper-supralabial, and upper and lower secondary temporals; secondary temporals two, upper one larger than the lower, upper one touching parietal and upper tertiary temporal; tertiary temporals three, equal in size, touching lower secondary temporal and upper posterior supralabial.

Supralabials 7, the last supralabial split on the left side (not split on right, a rare aberrant phenomenon), 5 th at mid-orbit point; post-supralabials one; mental wider than postmental in transverse axis, shorter in longitudinal axis, touching 1 st infralabial only; infralabials five, single post-infralabial; chinshields three pairs, first pair meeting in midline, first chinshield touching 1 st and 2 nd infralabials, second pair touching 2 nd and 3 rd infralabials; gular scales cycloid, imbricate.

Body moderately elongate, dorsal scales smooth, cycloid; paravertebrals 46; 28 transverse scale rows at midbody; ventrals 51, smooth, imbricate; median precloacals enlarged; forelimbs short, hind limbs relatively long, LAL 66.6% of TBL; thigh short and 78.5% of shank length; fourth finger with eight smooth lamellae; fourth toe with 14 smooth lamellae; relative length for fingers and toes both 4>3>5>2>1, scales of palm and sole elevated.

Tail autotomized and detached, complete, shorter than body (TL 88.4% of SVL), round in cross-section.

Coloration of syntype ZMB 3762. In preservative, the dorsal surface of the head, body, limbs, and tail is uniformly dark brown, with several indistinct darker longitudinal lines on the dorsum, anterior dorsal head darker; lower parts of the lateral head, temporal region, and throat light brown; neck color same as other ventral surfaces; light brown.

Variation. See Table 4. Body scalation in most examined specimens is as described above for the syntype, but the separation of prefrontals from each other by contact of frontal with frontonasal differs in comparative material. Among the materials at ZMH (n =15), the prefrontals are completely separated from each other (n =1), slightly in contact (n =4), and broadly in contact (n =10).

Comparison. See Tables 4 and 5 in Kanishka et al. (2020).

Coloration in life. Based on live individuals (not collected), males have dorsum iridescent brown, laterally iridescent light brown; hind limbs bronze brown with light markings; dorsal head dark brown, anteriorly black; the color of lower parts of the lateral head, temporal region, and throat highly variable ( Fig. 5 ), but mostly dark greyish brown, in some populations it can be yellowish orange, scarlet orange, or red; neck color same as the throat; white flecks present on labials, lower temporal region, throat, and neck spread up to the shoulders; venter cream or light brown in most of the females and non-breeding males, in most of the breeding males the venter is bright yellowish. Juveniles are lighter in color, mostly yellowish; the anterior throat is yellow, and posteriorly dark greyish brown, including the neck ( Fig. 6 ).

Distribution and natural history. This species is distributed throughout the island including all the bioclimatic zones from sea level to 1,200 m a.s.l. ( Karunarathna &Amarasinghe 2010, 2012; Karunarathna et al. 2013; Batuwita 2019). See the map ( Fig. 7 ) for confirmed locality data based on museum specimens and personal observations.

TABLE 4. Selected morphometric (in mm) and meristic characters of syntypes, synonym types, and other specimens of L. fallax ( Peters, 1860) ; “––” not evaluated; “+” distal part of the tail broken.

A diurnal skink occurring in every terrestrial habitat, except forests. They mostly occur on forest edges, in home gardens, agricultural lands, and occasionally, even within highly disturbed human habitation. However, this species is associated with understory vegetation, including grasses, fallen leaves, rocks, fallen logs or debris, and decaying leaf litter. It shelters at night among roots, tree buttresses, tree trunks, and tussocks ( Somaweera & Somaweera 2009). It prefers less shady habitats but with open canopy areas. This species is not sympatric with any other Lankascincus , as the rest of the species are mostly forest dwellers, sometimes found in well-shaded home gardens.

Conservation status. The updated distribution data shows that L. fallax is the most common species of the genus, and is widely distributed. It is abundant outside forests, and never found inside them. With an area of occupancy (AOO) of 1,375 km 2 (we recorded this species from 70 sites; Fig. 7 ) within a 40,784 km 2 extent of occurrence (EOO), we did not determine any severely fragmented locations as we observed the species from home gardens even in urban habitats, and we haven’t noticed any continuing population decline in EOO, AOO, area, extent or quality of habitat, number of locations/subpopulations, or even number of mature individuals. Therefore, the application of the IUCN Red List criteria (IUCN Standards and Petitions Subcommittee 2019), L. fallax can be considered as a “Least Concern” (LC) species.

Figures

FIGURE 3. Lankascincus fallax, syntype male (ZMB 3762), (A) full body; head in (B) dorsal view, (C) ventral view, (D) lateral view; not to scale. Photo F. Tillack.

FIGURE 4. Lankascincus fallax, males in breeding coloration (not collected) from (A) Galle (lowland wet zone), and (B) Ampara (lowland dry zone).

FIGURE 5. Color variation of males Lankascincus fallax in lowland populations (not collected, identified using photographs) from (A) dry zone and (B) wet zone.

FIGURE 6. Lateral view of head and neck of a juvenile Lankascincus fallax (not collected) from a home garden at Piliyandala, Western Province (lowland wet zone).

FIGURE 7. Current distribution map (based on museum specimens and personal observations) of Lankascincus fallax (circles), the two syntype localities of L. fallax are marked with squares; the holotype locality of L. deraniyagalae (synonym of L. fallax) is marked with a triangle.

FIGURE 8. Two Lankascincus fallax males from one population in Ampara, lowland dry zone (not collected), with arrows indicating (A) paired frontoparietal and a wide contact in prefrontals (B) fused frontoparietal and separated prefrontals separated.

Tables

TABLE 4. Selected morphometric (in mm) and meristic characters of syntypes, synonym types, and other specimens of L. fallax (Peters, 1860); “––” not evaluated; “+” distal part of the tail broken. Lankascincus fallax Sphenomorphus Lygosoma fallax Lankascincus deraniyagalae Lankascincus fallax rufogulus Peters, 1860 Greer, 1991 (Peters, 1860) Character Taylor, 1950 Syntype Holotype Holotype Paratypes males females ZMB 3762 FMNH NHMUK NHMUK NHMUK NHMUK (n=15) (n=3) male 120229 95.7.23.28C 95.7.23.28B 95.7.23.28D 95.7.23.28E snout-vent length 38.1 40.4 40.9 40.3 38.0 39.9 35.1–43.5 38.4–40.2 head length 5.7 7.1 10.0 8.8 8.1 11.1 6.7–8.9 7.0–7.4 head width 5.6 6.0 6.6 5.8 6.3 6.5 3.3–6.3 4.7–5.6 head depth 4.3 4.6 5.0 5.0 4.7 4.8 3.2–5.6 3.4–4.2 brachium length 2.9 3.1 3.1 3.3 3.7 3.5 2.4–3.6 2.5–2.9 antebrachium length 2.8 3.4 3.2 3.9 3.2 3.2 1.8–3.8 2.6–3.0 palm length 2.9 2.6 1.0 3.8 2.3 2.6 1.3–2.9 1.4–1.9 thigh length 3.3 4.6 4.2 5.0 3.9 3.5 3.1–4.9 4.0–4.9 shank length 4.2 4.1 4.1 5.1 4.0 3.4 3.2–9.7 5.3–5.9 foot length 5.0 5.9 5.2 5.97 4.8 5.6 3.8–5.1 4.1–4.5 body width 5.9 7.4 9.2 7.5 7.4 8.2 4.5–8.3 6.0–7.5 body depth 5.8 5.7 5.1 4.8 6.2 5.1 4.2–6.9 4.4–6.4 axilla–groin length 20.4 23.3 23.8 24.8 19.5 20.1 19.6–24.1 20.9–23.3 tail base width 3.7 4.4 3.6 4.4 4.8 5.2 3.5–4.9 3.6–4.3 tail length 33.7+ 40.1+ 36.5+ 9.6+ 3.1+ 38.4 32.5–72.5 38.0–47.0 supralabials 7 7 7 7 7 7 7 7 infralabials 5 5 5 5 5 5 5 5 suboculars 8 7 5 8 5 5 7–9 8 paravertebrals 46 47 46 48 51 49 46–53 48–52 midbody scale rows 28 28 28 26 26 25 24–28 24–28 ventrals 51 51 58 51 58 57 48–58 49–51 lamellae finger IV 8 10 11 11 12 damaged 8–12 10 lamellae toe IV 14 16 18 16 17 9 13–17 14, 15 Locality Trincomalee (dry zone: lowland) Pundaluoya (wet zone: highlands) throughout the island

Lankascincus fallax
Sphenomorphus Lygosoma fallax Lankascincus deraniyagalae rufogulus Peters, 1860 Greer, 1991 Character Taylor, 1950							Lankascincus fallax ( Peters, 1860)
	Syntype ZMB 3762 male	Holotype Holotype Paratypes males FMNH NHMUK NHMUK NHMUK NHMUK (n =15) 120229 95.7.23.28C 95.7.23.28B 95.7.23.28D 95.7.23.28E						females (n =3)
snout-vent length	38.1	40.4	40.9	40.3	38.0	39.9	35.1–43.5 38.4–40.2
head length	5.7	7.1	10.0	8.8	8.1	11.1	6.7–8.9	7.0–7.4
head width	5.6	6.0	6.6	5.8	6.3	6.5	3.3–6.3	4.7–5.6
head depth	4.3	4.6	5.0	5.0	4.7	4.8	3.2–5.6	3.4–4.2
brachium length	2.9	3.1	3.1	3.3	3.7	3.5	2.4–3.6	2.5–2.9
antebrachium length	2.8	3.4	3.2	3.9	3.2	3.2	1.8–3.8	2.6–3.0
palm length	2.9	2.6	1.0	3.8	2.3	2.6	1.3–2.9	1.4–1.9
thigh length	3.3	4.6	4.2	5.0	3.9	3.5	3.1–4.9	4.0–4.9
shank length	4.2	4.1	4.1	5.1	4.0	3.4	3.2–9.7	5.3–5.9
foot length	5.0	5.9	5.2	5.97	4.8	5.6	3.8–5.1	4.1–4.5
body width	5.9	7.4	9.2	7.5	7.4	8.2	4.5–8.3	6.0–7.5
body depth	5.8	5.7	5.1	4.8	6.2	5.1	4.2–6.9	4.4–6.4
axilla–groin length	20.4	23.3	23.8	24.8	19.5	20.1	19.6–24.1 20.9–23.3
tail base width	3.7	4.4	3.6	4.4	4.8	5.2	3.5–4.9	3.6–4.3
tail length	33.7+	40.1+	36.5+	9.6+	3.1+	38.4	32.5–72.5 38.0–47.0
supralabials	7	7	7	7	7	7	7	7
infralabials	5	5	5	5	5	5	5	5
suboculars	8	7	5	8	5	5	7–9	8
paravertebrals	46	47	46	48	51	49	46–53	48–52
midbody scale rows	28	28	28	26	26	25	24–28	24–28
ventrals	51	51	58	51	58	57	48–58	49–51
lamellae finger IV	8	10	11	11	12	damaged	8–12	10
lamellae toe IV	14	16	18	16	17	9	13–17	14, 15
Locality Trincomalee (dry zone: lowland)			Pundaluoya (wet zone: highlands) throughout the island