Leptolalax (Lalax) lateralis ( Anderson, 1871 )

Humtsoe, Nzano, Bordoloi, Sabitry, Ohler, Annemarie & Dubois, Alain, 2008, Rediscovery of a long known species, Ixalus lateralis Anderson, 1871, Zootaxa 1921, pp. 24-34 : 28-32

Leptolalax (Lalax) lateralis ( Anderson, 1871)

Neotype IASST A.68, adult male, by present designation. – Type-locality: Nhyatsutchu stream, Wokha district, Nagaland, India (alt. 1315 m; near 26°06’N, 94°16’E).

Chresonymy. We cite here only the references which designate the biological taxon defined by our designation of onomatophore:

Ixalus lateralis Anderson, 1871: 29 . – Boulenger 1882: 103; Fea 1897: 90.

Leptolalax (Lalax) lateralis – Delorme, Dubois, Grosjean & Ohler 2006: 14.

Description of the neotype ( Fig. 1 ; Tab. 2 )

Size and general aspect. (1) Specimen of small size (SVL 28.0 mm); moderately stout.

Head. (2) Head wider than long (HW 9.1 mm, HL 8.7 mm, MN 7.3 mm, MFE 5.4 mm, MBE 2.45 mm), flat above. (3) Snout rounded, slightly protruding, its length (SL 4.1 mm) subequal to horizontal diameter of eye (EL 4.0 mm). (4) Canthus rostralis rounded, loreal region concave. (5) Interorbital space flat, less wide than upper eyelid (IUE 2.45 mm, UEW 3.1 mm), distance between upper eyelids wider than distance between nostrils (IN 2.5 mm). Distance between anterior borders of eyes (IFE 4.1 mm) 2/ 3 in distance between backs of eyes (IBE 7.7 mm). (6) Nostril rounded, without flap of skin, less close to tip of snout (NS 2.0 mm) than to eye (EN 1.85 mm). (7) Pupil vertical. (8) Tympanum distinct, rounded, its diameter half diameter of eye ( TYD 2.0 mm, TYE 1.1 mm). (9) Pineal ocellus absent. (10) Vomerine ridge absent. (11) Tongue large, spatulate, notched; median lingual process absent; tooth-like projection on maxilla absent.

Forelimbs. (12) Arm short (FLL 6.3 mm), shorter than hand (HAL 7.2 mm), forearm not enlarged. (13) Fingers thin, rather long (TFL 3.6 mm). (14) Relative length of fingers I<II<IV<III. (15) Tips of fingers rounded, thickened, without grooves. (16) Fingers without lateral dermal fringe; webbing absent. (17) Subarticular tubercles absent; longitudinal ridges under fingers present. (18) Palmar tubercles present, prominent; inner rounded, outer oval.

Hindlimbs.(19) Leg short, four times longer (TL 12.9 mm) than wide (TW 3.2 mm), tibia shorter than thigh (FL 12.4 mm) and than foot (FOL 12.0 mm). (20) Toes long (FTL 5.4 mm), less one third of length from heel to tip of toe IV (TFOL 17.4 mm). (21) Relative length of toes I<II<V<III<IV. (22) Tips of toes rounded, thickened, without grooves. (23) Webbing rudimentary, dermal fringes on toes poorly developed: I 2 - 2 1/ 2 II 2 - 3 III 2 2/3 - 4 IV 4 1/4 - 3 1/ 4 V (MTTF 4.45 mm, MTFF 4.55 mm, TFTF 6.3 mm, FFTF 6.55 mm). (24) Dermal fringe along toe V absent. (25) Subarticular tubercles absent; longitudinal ridges under toes. (26) Inner metatarsal tubercle distinct (IMT 1.6 mm), 1.25 times in length of first toe (ITL 2.0 mm). (27) Tarsal fold absent. (28) Outer metatarsal tubercle absent.

Skin. (29) Dorsal and lateral parts of head and body: snout between eyes and back roughly granular; side of head smooth; lower part of flank with large glandular warts. (30) Latero-dorsal folds absent; Fejervaryan line absent; supratympanic fold distinct, from back of eye, ending in a gland above shoulder (rictal gland). (31) Dorsal parts of limbs: forearms with glandular warts; hindlimbs with glandular warts and longitudinal folds. (32) Ventral parts of head, body and limbs smooth; thighs with large glandular zone near vent. (33) Macroglands: femoral, rictal and supra brachial glands present.

Coloration of preserved specimen. (34) Dorsal and lateral parts of head and body: dark brown with indistinct darker spots including a pair of spots between eyes and spots in shoulder region; loreal and tympanic region light brown with darker spots and bands; tympanum with dark brown spot; flanks light brown with blackish spots. (35) Dorsal and lateral parts of limbs: forearms light brown with bands; hind limbs brown with narrow dark brown bands; posterior part of thigh dark brown with whitish spots (corresponding to glands). (36) Ventral parts of head, body and limbs: creamy white, margin of throat light brown with a line of white glandular dots; belly creamy white with a brownish zone and a line of white dots on the margin; glands creamy white; webbing brown.

Male secondary sexual characters. (37) Nuptial spines absent. (38) Vocal sacs indistinct on throat; openings on both sides of mouth floor. (39) Other male secondary sexual characters absent.

Variation. The adult male specimens (IASST A.66-67) vary slightly in size ( Table 2 ). The only known adult female (IASST A.69) is quite larger in size. Colour pattern is similar.

Comparison. Most of the characters of the original description of Ixalus lateralis are consistent with the character states observed in the neotype: shape of the head, dorsal skin, tympanic fold, length of fingers and toes, webbing, coloration and size. The main difference is the tympanum size, as Anderson (1871) described the tympanum as 1/3 the width of eye, whereas in the neotype the tympanum diameter is half eye length. However relative size of structures is difficult to evaluate without morphometric analysis. The original type also had some minute scattered tubercles on sides and sacral regions whereas the neotype is roughly granular all over the dorsal parts of body. The observation of skin structures in a small specimen is particularly difficult without a good microscope. For the identity of the nomen Ixalus lateralis , the description of neotype is now stringent despite these differences which might be genuine or due to observation defaults.

Comparison of measurements of specimens of Leptolalax pelodytoides from Myanmar, Xenophrys major from all its range and topotypes of Leptolalax lateralis ( Table 2 ) show consistent differences with Xenophrys major . The latter species is much larger than any species of Leptolalax . It can be recognized by the presence of a very conspicuous white longitudinal line on the upper lip. The eyelids are distinctly pointed, the chest, breast and upper belly show a dark coloration, including a band near arm insertion. None of these obvious patterns and structures was mentioned in the description of Anderson (1871).

The original description mentioned the “white line” on the side of belly, which we interpret as referring to the lateroventral glandular ridge, a character present only in the subgenus Lalax of the genus Leptolalax . Obviously, the nomen lateralis refers to this striking character which is an apomorphy of the subgenus Lalax . Other characters are consistent with allocation of this nomen to a species of this group: e.g., presence of supratympanic fold, feebly dilated finger and toe tips, relative length of fingers and toes, small webbing and presence of a femoral gland.

The species as defined by the neotype designation above is distinct from all other taxa allocated to the subgenus Lalax . Leptolalax lateralis can be distinguished from L. nahangensis , L. ventripunctatus , L. pluvialis , L. melanoleucus , L. fuliginosus , L. tuberosus and L. solus by the absence of brownish spots, dots or pattern on belly. L. sungi , L. nahangensis and L. bourreti have larger sizes (adult males more than 35 mm). Most species of Leptolalax (Lalax) have a smooth dorsal skin; some show a few small tubercles. Only two species Leptolalax Leptolalax Xenophrys Leptolalax Leptolalax Xenophrys

lateralis pelodytoides major lateralis pelodytoides major

Males Males Males Females Females Females MTTF 4.1 ± 0.38 5.57 ± 0.83 11.74 ± 2.88 5.3 5.0–7.0 12.34 ± 1.87 3.7–4.45 5.0–6.0 7.0–17.0 8–16 share rough dorsal skin beside L. lateralis : L. tuberosus has many scattered small tubercles on back and L. oshanensis has irregular thin skin ridges. No such skin ridges are present in L. lateralis which has irregularly set glandular warts on back.

The distributional range of Leptolalax lateralis is very close to the western border of the range of L. pelodytoides . This latter species, as currently understood, has a very large range going east to China, but may cover several distinct species (Ohler et al. in prep.). Special attention was paid to comparison of these two species by studying the type specimens. Due to the low number of specimens available, no statistical methods could be used. Nevertheless data exploration shows several consistent differences, including a smaller head in L. lateralis than in L. pelodytoides ( Fig. 2 ). These species can also be distinguished by the webbing, which is quite distinct in L. pelodytoides but rudimentary in L. lateralis .

Figures

FIGURE 1. Leptolalax lateralis (Anderson, 1871). Neotype IASST N 68, adult male, SVL 28 mm. Dorsal, ventral and lateral view. Photo N. Humtsoe.

FIGURE 2. Morphometrical differentiation of adult males of Leptolalax lateralis, L. pelodytoides and Xenophrys major. Left: boxplot of relative head length (HL / SVL); right: boxplot of relative head width (HW / SVL).

Tables

TABLE 2. Morphometrical data on Leptolalax lateralis, Leptolalax pelodytoides from Myanmar and Xenophrys major (for list of specimens studied, see Appendix).

N=3	N=3	N=23	N=1	N=2	N=11
SVL 27.45 ± 0.71 26.90–28.25	29.37 ± 2.57 27.50–32.30	71.84 ± 5.33 63.70–87.00	36.55	36.50–37.80	81.12 ± 8.10 66.70–91.70
HW 8.9 ± 0.17 8.8–9.1	10.40 ± 0.72 9.8–11.2	26.53 ± 1.86 23.3–30.2	12.2	12.2–13.2	31.39 ± 3.32 25.8–35.9
HL 8.57 ± 0.21 8.4–8.8	11.2 ± 1.22 10.4–12.6	26.34 ± 2.20 23.0–31.3	11.2	13.0–14.0	30.56 ± 3.06 25.6–34.5
MN 6.43 ± 0.13 6.3–6.6	9.87 ± 1.34 8.9–11.4	21.75 ± 2.20 18.5–26.1	9.7	11.3–12.1	25.33 ± 2.69 21.3–28.5
MFE 4.52 ± 0.08 4.45–4.60	7.67 ± 1.07 7.00–8.90	18.46 ± 1.71 15.90–22.30	8.05	8.50–9.70	21.87 ± 2.40 18.50–25.00
MBE 1.90 ± 0.05 1.9–2.0	4.03 ± 0.59 3.6–4.7	11.43 ± 0.85 10.2–13.5	3.05	4.5–5.1	13.94 ± 1.54 11.5–16.0
IFE 4.72 ± 0.06 4.1–4.55	5.23 ± 0.45 4.8–5.7	13.55 ± 0.84 11.6–15.1	4.5	5.7–6.2	14.87 ± 1.47 12.4–16.8
IBE 7.85 ± 0.15 7.70–8.00	8.37 ± 0.74 7.80–9.20	19.70 ± 1.47 17.10–22.50	7.85	9.70–10.80	22.94 ± 2.25 19.00–26.30
IN 2.35 ± 0.05 2.30–2.40	3.00 ± 0.17 2.90–3.20	8.77 ± 0.74 7.70–10.20	3.05	3.20–3.40	9.75 ± 1.19 7.80–12.10
EN 2.07 ± 0.12 1.85–2.2	2.13 ± 0.23 2.0–2.4	3.76 ± 0.71 2.4–5.0	2.5	2.6–2.7	4.33 ± 0.64 3.1–5.1
EL 4.05 ± 0.00 4.00–4.05	4.13 ± 0.32 3.90–4.50	7.93 ± 1.017 6.22–10.00	4.45	4.30–4.90	9.11 ± 1.57 6.29–11.30
TYD 2.22 ± 0.03 2.20–2.25	2.03 ± 0.15 1.90–2.20	4.49 ± 0.64 3.50–6.18	2.75	2.10–2.30	4.69 ± 0.66 3.50–5.40
TYE 1.08 ± 0.03 1.1–1.1	1.17 ± 0.15 1.0–1.3	5.57 ± 0.86 3.3–7.1	1.6	1.6	7.02 ± 0.84 5.8–8.0
FLL 7.03 ± 0.06 6.3–6.5	8.03 ± 0.93 7.4–9.1	17.30 ± 1.54 14.7–19.9	8.4	9.0–9.9	19.39 ± 1.54 16.8–21.4
HAL 6.55 ± 0.05 7.0–7.2	7.90 ± 0.50 7.4–8.4	18.14 ± 1.50 15.7–21.3	9.5	9.1–10.0	19.17 ± 2.09 16.5–24.6
TFL 3.77 ± 0.20 3.5–3.8	4.77 ± 0.21 4.6–5.0	10.46 ± 0.98 8.9–12.3	5.5	5.4–5.5	10.83 ± 1.03 9.7–13.0
TL 12.45 ± 0.30 12.10–12.9	14.13 ± 0.51 13.70–14.70	38.47 ± 2.70 33.80–43.50	15.8	15.60–16.40	43.88 ± 3.78 38.20–51.30
FOL 11.95 ± 0.48 11.40–12.20	14.20 ± 0.20 14.00–14.40	36.20 ± 2.81 31.00–41.00	13.75	16.20–16.30	40.07 ± 4.20 32.80–48.50
FTL 5.83 ± 0.15 5.4–5.9	7.93 ± 0.21 7.7–8.1	20.34 ± 2.23 15.6–24.7	7.1	8.9–9.2	22.73 ± 2.79 18.1–27.3
IMT 1.45 ± 0.10 1.25–1.45	1.50 ± 0.26 1.30–1.80	5.22 ± 0.81 3.70–7.11	1.55	1.50–1.80	5.05 ± 0.97 3.80–7.00
ITL 3.18 ± 0.03 1.7–2.0	2.90 ± 0.26 2.60–3.10	6.50 ± 1.11 4.74–8.90	2.0	3.30–3.50	7.13 ± 1.05 5.90–9.50