Eutropis bibronii (Gray, 1838)

Thasun, A. A., Campbell, Patrick D., Chandramouli, S. R., Deuti, Kaushik, Raha, Sujoy, Suranjan Karunarathna, D. M. S. & Ineich, Ivan, 2016, Taxonomy of two endemic Indian skinks, Eutropis bibronii (Gray, 1838) and E. nagarjunensis (Sharma, 1969) (Reptilia: Scincidae), including redescriptions of their types, Zootaxa 4154 (2), pp. 155-168 : 157-158

Eutropis bibronii (Gray, 1838)

( Figs. 1–4 ; Tables 1–3 )

Rachite de Bibron Cocteau, 1837 (nomen nudum) Tiliqua bibronii Gray, 1838

Gongylus (Eumeces) bibronii A.M.C. Duméril & Bibron, 1839 Euprepis trilineatus Gray, 1846

Syntypes (two specimens). Adult male (hemipenes partially everted), MNHN-RA 2940, SVL 50.0 mm; Adult female, MNHN-RA 7076, SVL 48.5 mm; “ South Africa ” (in error), collector and date unknown; here we suggest the type locality as Madras, South India based on the type locality of the syntypes for Euprepis trilineatus , a confirmed synonym of E. bibronii .

Diagnosis. The following combination of characters distinguishes Eutropis bibronii from all other Indian congeners: two dark paravertebral stripes separated by a pale median stripe on the back, undivided lower-eyelid disc, single postnasal, 28–30 midbody scale rows, 37–41 paravertebral scale rows, 46–52 ventrals, 5 keels on dorsal scales, 15–19 subdigital lamellae under fourth toe, two long pre-auricular lobules on each anterior tympanum, prefrontals slightly or broadly separated, two pairs of large nuchals (rarely three).

Redescription of the syntypes. Characters of the male syntype (MNHN-RA 2940) are followed, where appropriate, by those of the female syntype (MNHN-RA 7076) in brackets. Male, SVL 50.0 mm, tail length 76.0 mm (female, SVL 48.5 mm, tail length 59 mm); head moderately large, head length 22.6% of SVL (21.8%), head length 45.7% of axilla-groin distance (44.7%), narrow, head width 60.2% of head length (55.7%), head width 13.6% of SVL (12.2%), indistinct from neck; snout short, snout length 42.5% of head length (37.7%), snout length 70.6% of head width (67.8%), slightly concave in lateral profile; rostral shield large, hemispherical, distinctly visible from above, posterior margin of midpoint curved towards the frontonasal; frontonasal slightly separated from rostral by slightly separated supranasals; frontonasal narrow, lateral border touching first loreal; prefrontals broadly (slightly) separated, and the frontal and the frontonasal in contact, distance along the longitudinal axis of frontonasal equals the prefrontals in length, lower border touching both loreal scales, the posterior border touching the first supraocular, and frontal; frontal large, elongate, subtriangular, rounded posteriorly, equal in length of combined frontoparietals and interparietal; two frontoparietals in contact, distinct, larger than interparietal; parietals large and completely separated by interparietal, touching temporals laterally; two pairs of keeled nuchals, overlapping middorsally behind interparietal; interparietal with faint grey coloured parietal eye (pineal eye). Nostril large and situated posteriorly on a single nasal plate; single postnasal; loreals two, anterior loreal touching supranasal, frontonasal and prefrontal; posterior loreal longer than the anterior loreal in the longitudinal axis, touching prefrontal and first supraciliary; presuboculars two; eye large, orbit diameter 23.9% of head length (20.7%), orbit diameter smaller than tympanum-eye length, pupil rounded; interorbital distance broad; postoculars two; four wide supraoculars, second is the longest in the longitudinal axis and the widest in the transverse axis and fully contacts the frontal; first supraocular in contact with prefrontal; third and fourth supraoculars in contact with frontoparietals; fourth supraocular in contact with frontoparietal, parietal, and supraciliaries; two pretemporals; supraciliaries six; moveable eyelid covered with an undivided transparent disc. Supralabials six, fifth largest at mid orbit position; primary temporals three, secondary temporals three; infralabials six; ear opening deep, small, near spherical and approximately one quarter of eye diameter; two long pre-auricular lobules on each anterior tympanum, upper one longest. Mental large; a single large postmental followed by two chin shield pairs, the first chin shield in contact with 2nd and 3rd infralabial scales, the second pair in contact with 3rd and 4th infralabials.

Parietals and nuchals multicarinate, all body scales with five keels per scale; all scales imbricate and lacking apical pits; body slender, elongate, axilla-groin distance 49.4% of SVL (48.9%); midbody scale rows 28; paravertebral scale rows 41; ventrals 49 (damaged); five enlarged preanal scales.

Fore-limbs short, hind limbs relatively long, thigh length 15.0% of SVL (14.6%), shank length 15.2% of SVL (13.2%); thigh short and 98.7% of shank length (thigh long, 110.9%); scales on the dorsal surface of fore-limbs, thigh, and shank strongly carinate; subdigital lamellae on toe IV 16 (19); relative length of fingers: IV> III> II> V> I; those of toes: IV> III> V> II> I.

Tail complete, original (regenerated), median scale row of subcaudals similar to body scales while the median row of the regenerated tail is enlarged, wider than long.

Colouration. After more than 178 years in preservative fluid, dorsal head, body and limbs dark brown. Two dark vertebral stripes on the back separated by a median pale stripe, two additional dark stripes situated laterally and commencing from posterior eye to posterior member level approximately; the vertebral stripes extend up to mid body point and then fading away; the lateral stripes extend to flank over tympanum and end on the hind limbs. The medio-dorsal band covers a distance of approximately half to one scale width, whereas the lateral band is larger and covers a distance of 1 to 1.5 scale width – the second band is also much more visible anteriorly and fades away posteriorly. Lateral body and belly creamy white including subcaudals.

Comparison. Related congeners from India and Sri Lanka have suites of characters that distinguish them from Eutropis bibronii . Eutropis bibronii is most similar to E. nagarjunensis (characters in brackets), but it can be distinguished from the latter by having narrow vertebral stripes (broad); 28–30 midbody scale rows (33–35); 15–19 subdigital lamellae under fourth toe (21–24).

Unlike E. bibronii , E. andamanensis ( Smith, 1935) [ Andaman Islands ]; E. beddomei [ Sri Lanka and India]; E. carinata (Schneider, 1801) [ Sri Lanka and India]; E. clivicola (Inger, Shaffer, Koshy & Bakde, 1984) [Western Ghats, Peninsular India]; E. floweri (Taylor, 1950) [ Sri Lanka]; E. gansi (Das, 1991) [Western Ghats, Peninsular India]; E. macularia (Blyth, 1853) [ Sri Lanka and India]; E. madaraszi (Méhely, 1897) [ Sri Lanka]; E. multifasciata (Kuhl, 1820) [Northeast India and Sundaland]; E. quadricarinata Boulenger, 1887 [Northeast India]; E. rugifera (Stoliczka, 1870) [ Nicobar Islands and Sundaland]; E. tammanna Das, de Silva & Austin, 2008 [ Sri Lanka]; E. tytleri (Theobald, 1868) [Andaman Islands]; and E. trivittata (Hardwicke & Gray, 1827) [ India] has a scaly lower-eyelid disc (vs. undivided and transparent eyelid disc). E. dissimilis (Hallowell, 1857) [North India] has 47–52 paravertebrals (vs. 37–41). E. innotata (Blanford, 1870) [ India] has a single pair of nuchals (vs. two or three pairs). E. novemcarinata (Anderson, 1871) [Northeast India and Burma] has nine keels on dorsal scales (vs. five).

Figures

FIGURE 1. Dorsal view of the head of (A) Eutropis bibronii syntype (MNHN-RA 7076, SVL 48.5 mm), (B) E. nagarjunensis holotype (ZSI 21170, SVL 47.5 mm); lateral view of the head of (C) E. bibronii syntype (MNHN-RA 7076), and (D) E. nagarjunensis holotype, (ZSI 21170) (scale = 2 mm).

FIGURE 2. Illustration showing the comparison of dorsal head scales of (A) Eutropis bibronii syntype (MNHN-RA 7076), (B) E. nagarjunensis holotype (ZSI 21170); and E. beddomei holotype (BMNH 1946.8.19.17).

FIGURE 3. (A) A live male of Eutropis bibronii (not collected) from Hosur, Eastern Ghats, India (photo: S. R. Chandramouli); (B) A live male of E. nagarjunensis (not collected) from the type locality, Nagarjunsagar, Andhra Pradesh, India (photo: D. Adimallaiah).

FIGURE 4. Plot of (a) PC 1 vs. PC 2 and (b) PC 1 vs. PC 3 showing morphometric similarity between the taxa Eutropis bibronii and E. nagarjunensis, and their distinction from E. beddomei. Eutropis bibronii (dark blue), syntypes of Euprepis trilineatus in light blue; Eutropis nagarjunensis (green); and Eutropis beddomei (red), the circle with dot in the middle represents the examined Sri Lankan specimens.