Limnonectes (Elachyglossa) savan, Phimmachak, Somphouthone, Richards, Stephen J., Sivongxay, Niane, Seateun, Sengvilay, Chuaynkern, Yodchaiy, Makchai, Sunchai, Som, Hannah E. & Stuart, Bryan L., 2019

Phimmachak, Somphouthone, Richards, Stephen J., Sivongxay, Niane, Seateun, Sengvilay, Chuaynkern, Yodchaiy, Makchai, Sunchai, Som, Hannah E. & Stuart, Bryan L., 2019, A new caruncle-bearing fanged frog (Limnonectes, Dicroglossidae) from Laos and Thailand, ZooKeys 846, pp. 133-156 : 137-145

Limnonectes (Elachyglossa) savan sp. nov. Figures 3, 4, 5, 6

Limnonectes sp. Chan-ard, 2003: 120.

Holotype.

NCSM 76288 (field tag BLS 12395), adult male (Figs 3, 4), Laos, Savannakhet Province, Vilabouli District, Sepon Mining Tenement, Ban Houay Hong Village, Houay Hong Stream, 17.04444°N, 106.12622°E, 254 m elev., under boulder in shallow water of 1-3 m wide swift, rocky stream in semi-evergreen forest, coll.15 November 2008 at 2220 h by Bryan L. Stuart, Somphouthone Phimmachak, Stephen J. Richards, and Niane Sivongxay.

Paratypes.

Laos, Savannakhet Province, Vilabouli District: NCSM 76287 (one adult male), SAMA R64243 (one juvenile), same data as holotype. NCSM 76294 (one adult female), NCSM 76295, SAMA R64251 (two juveniles), same data as holotype except coll. 04 December 2008. NCSM 76289 (one adult male), SAMA R64244 (one adult female), same data as holotype except Houay Po Stream, 17.04297°N, 106.12503°E, 278 m elev., coll. 18-20 November 2008. SAMA R64245 (one adult male), NCSM 76290, SAMA R64249 (two juveniles), same data as holotype except Ban Nam Pa Village, Houay Hua Tad Stream, 16.96317°N, 106.04661°E, 326 m elev., coll. 22-25 November 2008. SAMA R64246-47 (two adult males), SAMA R64248, NCSM 76291-93 (four juveniles), same data as holotype except Houay Lavi Stream, 16.95653°N, 106.06767°E, 303 m elev., coll. 26 November 2008. SAMA R64250 (one adult female), same data as holotype except Houay Nam Pa Stream, 16.95944°N, 106.04661°E, 280 m elev., coll. 29 November 2008. NCSM 76308 (one adult male), NCSM 76309 (one juvenile), same data as holotype except 17.04120°N, 106.12889°E, 315 m elev., coll. 6 July 2009 by Bryan L. Stuart, Somphouthone Phimmachak, and Niane Sivongxay. NUOL 00092 [formerly NCSM 76298], NCSM 76296, NCSM 76300 (Fig. 4), NCSM 76301 (Fig. 3), NCSM 76304 (five adult females), NUOL 00091 [formerly NCSM 76297], NCSM 76299, NCSM 76302, NCSM 76303 (Fig. 3), NCSM 76305-06 (six adult males), NCSM 76307 (one juvenile), same data as holotype except Nam Sangi River Drainage Basin, 17.02073°N, 106.28625°E, 454 m elev., coll. 25 June– 1 July 2009 by Bryan L. Stuart, Somphouthone Phimmachak, and Niane Sivongxay. NCSM 84943 (one adult male), same data as holotype except Ban Namalou Village, 16.93401°N, 105.90562°E, coll. 28 September 2014 by Bryan L. Stuart, Sengvilay Seateun, Niane Sivongxay, Derin Henderson, and Singthong Sanvixay. NUOL 00061 (one adult female; Fig. 3), same data as holotype except Phou Thaeng kham Mountain, 16.95279°N, 105.92284°E, coll. 28 September 2014 by Bryan L. Stuart, Sengvilay Seateun, Niane Sivongxay, Derin Henderson, and Singthong Sanvixay.

Laos, Khammouan Province, Boualapha District: NCSM 80962 (one juvenile), Xe Bangfay River, 6 km upstream of Ban Pakphanang Village, 17.39972°N, 105.77278°E, coll. 17 March 2002 by Maurice Kottelat. FMNH 255385 (one adult male), FMNH 255386-87 (two juveniles), Hin Nam No National Protected Area, Phou Khaonok Mountain, 17.38333°N, 105.75000°E, 545 m elev., coll. 19-21 February 1998 by Bryan L. Stuart. FMNH 255388 (one adult female), FMNH 255389-90 (two juveniles), same data as FMNH 255385 except 17.33333°N, 105.68333°E, 500 m elev., coll. 23-24 February 1998.

Laos, Champasak Province, Pakxong District: NUOL 01151 (one adult female), NUOL 01152-55 (four adult males), Ban Nong Theuam Village, Phou Katam Moun tain, Houay Hongkhimin Stream, 15.14461°N, 106.61658°E, 790 m elev., coll. 3 April 2016 by Somphouthone Phimmachak and Sengvilay Seateun. NUOL 01156 (one juvenile), Ban Nam Tuad, downstream of Houay Hongkhimin Stream near road to Attapeu Province, 15.12535°N, 106.63216°E, 503 m elev., coll. 6 April 2016 by Somphouthone Phimmachak and Sengvilay Seateun. NUOL 01157 (one adult male), same data as NUOL 01156 except Xe Katam Waterfall, 15.12355°N, 106.63779°E, 350 m elev.

Thailand, Ubon Ratchatani Province, Na Chaluai District: FMNH 266149 (one adult male), Phu Jong-Na Yoi National Park, Huay Luang Noi Stream, 14.43775°N, 105.28006°E, 360 m elev., coll. 15 September 2004 by Bryan L. Stuart, Yodchaiy Chuaynkern, Chatchay Chuechat, and Sunchai Makchai. FMNH 266155 (one adult male), FMNH 266156 (one adult female), same data as FMNH 266149 except hill evergreen forest along road, 14.43850°N, 105.26792°E, 325 m elev., coll. 13 September 2004.

Thailand, Ubon Ratchatani Province, Buntharik District: FMNH 266157-58 (two adult females), Phu Jong-Na Yoi National Park, evergreen forest along dirt road, 14.44186°N, 105.30753°E, 400 m elev., coll. 16 September 2004 by Bryan L. Stuart, Yodchaiy Chuaynkern, Chatchay Chuechat, and Sunchai Makchai.

Thailand, Ubon Ratchatani Province, Sirindhorn District: FMNH 173514-15 (two juveniles), Forestry Station, Sai Noi River, coll. 23 March 1958 by Edward H. Taylor.

Referred specimens.

NCSM 76491 (13 larvae), same data as NUOL 00091. NCSM 76492 (28 larvae), NCSM 76493 (43 larvae), NCSM 76494 (one clutch of 70 eggs), same data as NCSM 76305.

Etymology.

The specific epithet savan means paradise in the Lao language, and is a commonly used, truncated form of the name for Savannakhet Province, Laos, that contains the holotype and most paratype localities of the new species. The specific epithet savan is a noun in apposition.

Suggested common names.

Savan Fanged Frog (English), Kop Hone Savan (Lao), Kop Panomdongrak (Thai).

Diagnosis.

Assigned to the genus Limnonectes on the basis of its inferred phylogenetic position (Fig. 1), the presence of fang-like odontoid processes on the lower jaw ( Emerson et al. 2000; Lambertz et al. 2014), and having males with hypertrophied heads ( Lambertz et al. 2014). Assigned to the subgenus Elachyglossa (following Ohler and Dubois 1999; Lambertz et al. 2014) on the basis of its close phylogenetic position to the subgenerotype L. gyldenstolpei (Fig. 1). A medium-sized Limnonectes having the combination of adult males with SVL 39.0-56.2, adult females with SVL 38.9-55.2; males with hypertrophied head; males with interorbital caruncle consisting of low-profile swelling without a free posterior margin, extending from level of anterior margin of eye to level midway between posterior margin of eye and tympanum; odontoid processes on anterior margin of lower jaw larger in males than in females; horizontal diameter of tympanum equal to eye in adult males, ¾ of eye diameter in subadult males, immature males, and females; enlarged, rounded, tubercles on dorsum, becoming more elongated dorsolaterally; dark brown or gray spotting on throat, belly, and ventral surfaces of forelimbs and hindlimbs; and ova with pigmented poles.

Description of holotype.

Habitus moderately stocky; body broad anteriorly, tapering to narrow groin. Head broad and depressed, head width equal to head length. Snout obtusely pointed in dorsal view; round, projecting well beyond lower jaw in profile; nostril dorsolateral, much closer to tip of snout than to eye, below canthus; internarial distance 72% of interorbital distance; canthus rostralis indistinct, rounded, slightly constricted behind nostrils; lores concave, oblique; eye diameter 59% of snout length, upper eyelid width 50% of interorbital distance; pineal ocellus visible; tympanum imperfectly circular, not elevated from side of head, annulus visible, tympanum diameter equal to eye diameter and greater than distance between tympanum and eye; small, slit-like vocal sac openings on floor of mouth near lateral margin of tongue; vomerine teeth on two oblique ridges, equidistant to each other as to choanae; two large odontoid processes at front of mandible, triangular, tapered, length subequal to depth of mandible at base of process; median triangular symphysial knob at mandibular symphysis.

Forelimbs robust. Fingers relatively slender, without webbing, with fringe of skin on preaxial and postaxial sides of all fingers, fringes on Fingers II-III movable; tips of fingers rounded, expanded into discs; relative finger lengths II <I <IV <III; distinct, rounded subarticular tubercles, one on Fingers I–II, two on Fingers III–IV; distinct thenar tubercle; two palmar tubercles in contact at base of Fingers II–IV; nuptial pad absent.

Hindlimbs robust. Toes relatively slender; tips of toes rounded, expanded into small discs; relative toe lengths I<II<III=V<IV on right foot, I<II<V<III<IV on left foot; webbing on Toe I to base of disc, on preaxial side of Toe II to level midway between subarticular tubercle and disc and continuing as fringe to base of tip, on postaxial side of Toe II to base of disc, on preaxial side of Toe III to level of distal subarticular tubercle and continuing as fringe to base of disc, on postaxial side of Toe III to base of disc, on preaxial and postaxial sides of Toe IV to level of distal subarticular tubercle and continuing as fringe to base of disc, and on Toe V to base of disc; moveable fringe of skin on outer margins of Toes I and V; distinct fold on distal two-thirds of tarsus; distinct, elongate, oval, inner metatarsal tubercle, length approximately 59% distance between tip of toe I and tubercle; no outer metatarsal tubercle.

Skin on dorsum and flank shagreened with large, irregular, scattered tubercles; tubercles tipped with single, whitish spinule on loreal region, eyelid, lower back near groin, around vent, and ventral surfaces of tibiotarsus and foot; dense clusters of warts (enlarged tubercles), each tipped with numerous whitish spinules, on dorsal surfaces of shank; interorbital caruncle consisting of low-profile swelling without free posterior margin, extending from level of anterior margin of eye to level midway between posterior margin of eye and tympanum, with highest point between eyes; hypertrophied jaw musculature forming two low postorbital swellings on top of head at level of tympanum; distinct supratympanic fold from posterior corner of eye to axilla; rictal gland absent; dorsolateral fold absent; aberrant, triangular skin tag near midline of back; skin on throat with weak longitudinal wrinkles, that on remaining ventral surfaces smooth.

Color of holotype in life.

Dorsum tan. Loreal region, tympanic region, and dorsal surfaces of digits whitish gray. Back of head, dorsolateral region, under canthus and dorsoposterior region of tympanum with gray mottling. Dorsal and posterior surfaces of thigh, posterior surface of shank, and groin with yellowish wash. Lips with irregular, broad, gray bars, dorsal surfaces of limbs with cross-bands. Interorbital bar tannish yellow. Iris bronze with black vermiform mottling, black vertical and horizontal bars forming shape of a single plus sign ( “+”) over eye (Fig. 3). Ventral surfaces not photographed prior to preservation.

Color of paratype male in life.

Based on NCSM 76303. Dorsal surfaces same as holotype except narrow yellow vertebral stripe from tip of snout to vent. Ventral surfaces very light gray with dark gray mottling, only small area near midline of chest nearly immaculate, dark gray mottling becoming denser on ventral surfaces of limbs, nearly uniformly dark gray on ventral surfaces of hands and feet. Inguinal region and ventral surfaces of shank with yellowish wash (Fig. 3).

Color of holotype in preservative.

Dorsal surfaces nearly uniformly brown with indistinct, scattered, dark brown mottling, lips with indistinct dark brown bars, and dorsal surfaces of limbs with indistinct dark brown cross-bands. Tympanum and forelimbs with lighter brown than remaining dorsum. Interorbital bar indistinct. Ventral surfaces light brown with dark brown mottling, becoming uniformly dark brown on ventral surfaces of hands and feet (Fig. 4).

Description of eggs.

Based on subsample of eggs (NCSM 76494) collected from a larger clutch in situ (Fig. 5). Most in Gosner Stage 14, with single jelly layer having diameter of 4.8-5.5 mm (5.1 ± 0.3, n = 13), and embryos with a darkly pigmented animal pole having diameter of 2.2-2.5 mm (2.3 ± 0.1, n = 13).

Description of larvae.

Based on largest individual in series of 28 larvae (NCSM 76492; Fig. 6). Gosner Stage 31, TL 18.4 mm, BL 7.4 mm, TAL 11.0 mm. Body oval in dorsal view, slightly compressed dorsoventrally, maximum body width slightly anterior to level of spiracle. Nares dorsal, without raised rim. Eyes dorsolateral, not visible from below. Spiracular tube single, sinistral on left side, angled slightly dorsally, aperture near midline and projecting posteriorly, approximately midway between snout and end of body. Tail slender, tapering in distal one-fourth to rounded tip, origins of dorsal and ventral fins at end of body, dorsal and ventral fin widest near middle of tail, dorsal fin only slightly deeper than ventral fin. Oral disk ventral, subterminal, width about 39% maximum width of body. Anterior labium with single row of papillae on lateral margins; posterior labium with single row of papillae on lateral and posterior margins; papillae homogenous in length. Labial tooth row formula 2(2)/3(1). A-1 longer than A-2, medial gap in A-2 approximately three-fourth length of A-2. P-1 and P-2 subequal in length, P-3 approximately one-half length of P-1 and P-2. Upper and lower jaw sheaths black with serrated margins, upper sheath without median convexity. In life, dorsum light brown. In preservative, body and tail white with brown mot tling on dorsolateral surfaces of body, forming indistinct crossbands on tail. Intestine yellow in dorsal and ventral views. Measurements (TL) of additional larvae (NCSM 76491-93): Gosner Stage 25 11.7-13.1 mm (12.4 ± 0.4, n = 15), Gosner Stage 26 12.9-14.5 mm (13.6 ± 0.5, n = 13), Gosner Stage 27 14.2-15.8 mm (15.0 ± 0.6, n = 13), and Gosner Stage 28 15.5-17.0 mm (16.3 ± 0.8, n = 3).

Variations.

Females lack caruncle and postorbital swellings (Fig. 3); have narrower heads in dorsal view than males (Table 1; Fig. 4); have relatively smaller tympana than males, with tympanum diameter less than eye diameter (Table 1; Fig. 3); have smaller and shorter odontoid processes than males; have more elongated tubercles on dorsolateral region and flank than males; and contain ova with pigmented poles (Fig. 5).

The holotype is the largest male in the type series, with the next largest male (NCSM 76299) having SVL of 53.6 mm. Two paratype males (NCSM 76299, NCSM 76303) have higher-profile caruncles, higher-profile postorbital swellings, and more distinct longitudinal wrinkles on skin of throat than holotype.

Dorsal surfaces are lighter brown, or have more gray mottling, in some specimens than in the holotype. Lip bars on lips and crossbands on dorsal surfaces of limbs more distinct in some specimens than in the holotype. Six paratypes (NCSM 76294, NCSM 76302-04, NUOL 00061, NUOL 00091, NUOL 01153, and SAMA R64247) have a narrow, pale vertebral stripe from tip of snout to vent. Measurements of adults are summarized in Table 1.

Distribution, natural history.

Limnonectes savan is known to occur in central and southern Laos (Khammouan, Savannakhet, and Champasak Provinces), and northeastern Thailand (Ubon Ratchatani; Fig. 7). Chan-ard (2003) also reported it (as Limnonectes sp.) from Amnat Charoen Provinces in northeastern Thailand. The species occurs in hill and semi-evergreen forest from 254-790 m elevation, and is usually associated with small (1-3 m wide) streams (Fig. 8); based on 51 specimens sampled at night (1900 h– 2251h), 38 (74.5%) were found in streams (permanent streams with rocky or sandy substrates, or intermittent streams), nine (17.7%) were found in puddles, two (3.9%) were found in ponds, and two (3.9%) were found on the forest floor, away from an obvious body of water. Nineteen (37.3%) of the 51 specimens were sampled in water, with the remaining 32 individuals (62.7%) found on substrates of soil, leaf litter, rocks or logs.

Limnonectes savan breeds in puddles on the forest floor during the rainy season. A chorus of calling males, including paratype male NCSM 76299, was observed in a wet gully under roots and dead leaves in semi-evergreen forest at 1935 h on 28 June 2009. Egg clutch NCSM 76494 was found adhering to the underside of a submerged dead palm frond in a puddle in the same wet gully on 1 July 2009 (Fig. 5). Larvae NCSM 76491 (n=13), NCSM 76492 (n=28), and NCSM 76493 (n=43) were sampled from small puddles (0.2-1 m diameter) in the same wet gully during 28 June– 1 July 2009 (Fig. 6).

Limnonectes savan occurs in sympatry with L. lauhachindai in Ubon Ratchathani Province in northeastern Thailand (Appendix 1), but its geographic distribution appears to be parapatric to that of L. dabanus in southern Laos, and to that of L. gyldenstolpei in central and southern Laos and northeastern Thailand (Appendix 1).

Comparisons.

Limnonectes savan differs from all other species of mainland Southeast Asian Limnonectes , except L. gyldenstolpei , L. lauhachindai , L. dabanus , L. macrognathus , and L. plicatellus , by having mature males with an interorbital caruncle (sensu Lambertz et al. 2014). Limnonectes savan differs from these five species by having mature males with interorbital caruncle consisting of low-profile swelling without free posterior margin, with highest point at level between eyes (vs. caruncle U-shaped with free posterior margin in L. gyldenstolpei and L. lauhachindai , caruncle high-profiled in L. dabanus , caruncle high-profiled and horned in L. plicatellus , and caruncle with highest point posterior to level of eyes in L. macrognathus ); and by having dark spotting on ventral surfaces of chest, belly, and limbs in preserved specimens of adults and juveniles of both sexes (vs. these surfaces mostly immaculate in L. gyldenstolpei , L. lauhachindai , L. dabanus , L. macrognathus , and L. plicatellus ; Figs 9, 10).

Limnonectes savan further differs from L. gyldenstolpei , L. lauhachindai , L. dabanus , and L. macrognathus by having relative toe lengths I<II<III=V<IV, with the tips of Toes III and V reaching the base of the distal subarticular tubercle on Toe IV (vs. relative toe lengths I<II<V<III<IV, with the tip of Toe III shorter not reaching the distal subarticular tubercle on Toe IV in L. gyldenstolpei , L. lauhachindai , L. dabanus , and L. macrognathus ). Limnonectes savan further differs from L. plicatellus by having males with much larger body size (SVL ≤ 43.0 in L. plicatellus ; Boulenger 1920; Taylor 1962; Chan-ard 2003; Lambertz et al. 2014) and by lacking dorsal rugosities arranged in distinct, longitudinal rows parallel to the body axis (vs. present in L. plicatellus ).

Limnonectes savan is phenotypically most similar and phylogenetically most closely related (Fig. 1), to L. dabanus . The new species further differs from L. dabanus by having mature males with two large, tapered odontoid processes of length subequal to depth of mandible at base of process (vs. odontoid processes much less tapered and with length less than one-half depth of mandible at base of process in L. dabanus ; Fig. 11); by having mature males with TMP = EYE (vs. TMP> EYE in L. dabanus ); by having the dorsal surfaces of shank with dense clusters of warts, each tipped with numerous whitish spinules (vs. warts and tubercles less distinct and lower in profile, with more homogeneous distributions of whitish spinules in L. dabanus ); by having larvae with A-1 longer than A-2 (vs. A-1 and A-2 subequal in length in L. dabanus ), with medial gap in A-2 approximately three-fourths length of A-2 (vs. approximately one-half length of A-2 in L. dabanus ), and having P-1 and P-2 subequal in length (vs. P-1 longer than P-2 in L. dabanus ); and by having much shorter calls of 57-74 ms (vs. 141-197 ms in L. dabanus ; Rowley et al. 2014).

Male secondary sexual characters are unknown in L. khammonensis ( Smith 1929), which is known only from the female holotype, but females of L. savan differ by having a distinct tympanum (indistinct in L. khammonensis ); having larger body size, with SVL 38.9-55.2 (vs. gravid holotype female SVL 37.5 in L. khammonensis ); and less toe webbing (vs. Toe IV webbed to distal subarticular tubercle, continuing as fringe to base of disc, and all remaining toes webbed to base of disc in L. khammonensis ).