Limnonectes fastigatus, Stuart & Schoen & Nelson & Maher & Neang & Rowley & Mcleod, 2020

Stuart, Bryan L., Schoen, Sara N., Nelson, Emma E. M., Maher, Heather, Neang, Thy, Rowley, Jodi J. L. & Mcleod, David S., 2020, A new fanged frog in the Limnonectes kuhlii complex (Anura: Dicroglossidae) from northeastern Cambodia, Zootaxa 4894 (3), pp. 451-473 : 459-464

Limnonectes fastigatus sp. nov.

Limnonectes kuhlii Stuart, Sok & Neang, 2006:138 ; Neang & Holden, 2008:94; Stuart in McLeod, 2008:26.

Limnonectes kuhlii “Lineage 4” McLeod, 2010:995; McLeod, Kelly & Barley, 2012:263; Pham, Le, Ngo, Ziegler & Nguyen, 2018:127.

Limnonectes “ kuhlii ” 2: Suwannapoom, Yuan, Chen, Hou, Zhao, Wang, Nguyen, Nguyen, Murphy, Sullivan, McLeod & Che, 2016:185.

Limnonectes “cf kuhlii 2” Pham, Le, Ngo, Ziegler & Nguyen, 2018:117.

Holotype. MVZ 258214 (field tag BLS 11325), adult male ( Figs. 5–6 ), Cambodia, Ratanakiri Province, Veunsai District, Virachey National Park , at 14.19287°N, 106.99612°E, 650 m elev., coll. 13 October 2007 by Bryan L. Stuart, Jodi J.L. Rowley, and Thy Neang.

Paratypes. All from Virachey National Park, Cambodia .

Ratanakiri Province, Ta Veng District : FMNH 262722–262725 (four males), O Lopeung Stream, 14.18786°N, 107.29336°E, 160 m elev., coll. 19–21 November 2003 by Bryan L. Stuart, Thy Neang, and Ko Sok .

Ratanakiri Province, Veunsai District : MVZ 258204 , 258209–10 , 258212 , 258216 (five males), MVZ 258203 , 258205–07 , 258211 , 258215 (six females; Figure 7 A–B), MVZ 258213 , 258225 , 258227 (three juveniles), same data as holotype except coll. 2–13 October 2007. MVZ 258217 , 258219 , 258232 (three males), MVZ 258208 , 258218 , 258220 (three females), 14.18778°N, 106.99573°E, 602 m elev., coll. 6–14 October 2007 by Bryan L. Stuart, Jodi J. L. Rowley, and Thy Neang. MVZ 258245 (one male), 14.23813°N, 106.98158°E, 603 m elev., coll. 11 October 2007 by Bryan L. Stuart, Jodi J.L. Rowley, and Thy Neang .

Stung Treng Province, Siem Pang District : FMNH 262726 (one male), FMNH 262727–730 (four females), 14.26769°N, 106.629056°E, 550–600 m elev., coll. 1 December 2003 by Bryan L. Stuart, Thy Neang, and Ko Sok .

Referred material. All from Virachey National Park, Ratanakiri Province, Cambodia.

Ta Veng District : MVZ 258079–87 (nine, unsexed, post-metamorphic frogs), vicinity of 14.20000°N, 107.36667°E, 450–500 m elev., coll. 20–21 June 2006 by David A. Emmett and Jodi J.L. Rowley .

Veunsai District : MVZ 258251 (egg clutch; Fig. 7C ), 14.18778°N, 106.99573°E, 602 m elev., coll. 14 October 2007 by Bryan L. Stuart, Jodi J.L. Rowley, and Thy Neang .

Etymology. The specific name fastigatus (L.) for sharp, pointed, or wedge-shaped refers to the particularly sharp and pointed odontoid processes (“fangs”) in this species.

Diagnosis. Assigned to the genus Limnonectes on the basis of its molecular phylogenetic position ( McLeod 2010; McLeod et al. 2012; Suwannapoom et al. 2016; Pham et al. 2018) and having fang-like odontoid processes on lower jaw, larger in males than females ( Emerson et al. 2000). Assigned to the L. kuhlii complex on the basis of its molecular phylogenetic position ( McLeod 2010; McLeod et al. 2012; Suwannapoom et al. 2016; Pham et al. 2018) and having tympanum hidden and toes fully webbed ( Boulenger 1920; Taylor 1962; Inger 1966).

Limnonectes fastigatus sp. nov. can be distinguished from all other members of the L. kuhlii complex by having the combination of adult males with SVL 50.3–70.3 mm (mean 59.7 ± SD 7.8; n = 7), adult females with SVL 48.9–67.4 mm (mean 59.7 ± SD 6.0; n = 6); adult males with BL 29.6–38.0 mm (mean 34.3 ± SD 3.4; n = 7), adult females with BL 27.9–41.3 mm (mean 36.1 ± SD 4.6; n = 6); adult males and females having similar head and body sizes and proportions, with no significant difference between sexes in BL, SVL, HL:SVL, or HL:HW; males with nuptial pads on first finger (Finger II); odontoid processes thin and elongated with sharply-pointed or rounded tips, longer in males than females; prominent supratympanic fold extending from posterior corner of eye to axilla; venter whitish gray in life, creamy white in preservative, belly immaculate, throat and ventral surfaces of thighs with brown mottling at outer margins; relative finger lengths IV>V>III>II; and relative toe lengths IV>III>V>II>I.

Description of holotype. Habitus robust with moderately enlarged head, HL 47% SVL, HL slightly shorter than HW. Rostrum acutely rounded in dorsal view, projecting beyond lower jaw, obtusely sloping in profile; nostril elongate, ovoid, anterodorsolaterally oriented, about midway between snout tip and eye, EN 50% ES; IN subequal to IO; canthus rounded; lores concave; upper lip distinctly swollen with longitudinal groove, reaching post-rictal tubercle; ED 21% HL; UEW shorter than IO. Hypertrophied jaw musculature (adductors) visible on dorsum of head forming two distinct oval mounds posterior to eyes. Supratympanic fold robust, extending from eye to angle of jaw (insertion of arm); tympanic annulus not visible through skin. Vomerine teeth on oblique ridges, narrowly separated from each other (less than width of one ridge), subequal in size to choanae. Choanae oval, perpendicular to longitudinal axis of body. Odontoid processes robust at base tapering to pointed tips, length almost twice depth of mandible at base of processes. Symphysial knob at mandibular symphysis. Tongue oval, notched posteriorly.

Forelimbs robust. Finger tips rounded, not expanded into discs, with rounded distal pad; relative finger lengths IV>V>III>II; no webbing between fingers; distinct, movable fringe of skin on pre- and postaxial sides of Fingers III and IV; indistinct, immovable fringe on preaxial side of Finger V; subarticular tubercles prominent, rounded, elevated, one on Fingers II and III, two on Fingers IV and V; thenar metacarpal tubercle at base of Finger II large, oval, slightly elevated; middle metacarpal tubercle at base of Finger IV oval, smaller than thenar tubercle, not contacting outer or thenar tubercles; outer metacarpal tubercle at base of Finger V smaller than middle metacarpal tubercle, oval, slightly elevated; prominent nuptial pad composed of minute spines forming a shagreen texture on dorsal and medial surface of Finger II from tip of digit to base of thenar tubercle. Hindlimbs robust. Tips of toes rounded without circummarginal groove, not expanded into discs, toe pads elevated; relative toe lengths IV>III>V>II>I; toes webbed to middle of terminal phalanx at base of toe pad, formula I 0 + –0 + II 0 + –0 + III 0 + –0 + IV 0 + –0 + V; distinct, movable flap of skin on postaxial side of Toe V from base of toe pad to proximal end of metatarsus; distinct, movable flap of skin on preaxial side of Toe I from base of toe pad to level of inner metatarsal tubercle, continuing as distinct fold on distal half of tarsus; subarticular tubercles prominent, rounded, elevated, one on Toes I and II, two on Toes III and V, three on Toe IV; inner metatarsal tubercle oval, elongate with elevated post axial border.

Skin on top of head, dorsal surfaces of forelimbs, and dorsum crenulate; skin on sides, around vent, and dorsal surfaces of thigh, shank, and foot distinctly tuberculate, covered with moderately dense small, low warts tipped with translucent spinules; ventral skin smooth, with weak longitudinal wrinkles on throat. Caruncle absent. Small, triangular aberrant skin tag on right side of head posterior to eyes; small aberrant skin tag on dorsal surface of left distal forearm.

Measurements of holotype (mm): BL 37.5; ED 6.8; EN 5.2; ES 10.3; FEL 38.8; FOL 46.6; HL 32.8; HW 35.1; IN 7.2; IO 6.9; LAL 13.0; MD 2.8; MN 30.6; NS 5.1; OH 5.3; PAL 20.2; SVL 70.3; TBL 34.4; UEW 5.2.

Color of holotype in life. Dorsal surfaces golden brown (Yellow Ocher 14) with dark gray-brown (Grayish Olive 273) mottling; upper lip and rostrum black (Sepia 286), lower lip with irregular, black (Dark Grayish Olive 275) blotches; supratympanic fold black (Dark Grayish Olive 275); oblique, golden (Buff 5) band between supratympanic fold and upper lip, continuing to angle of jaw; golden (Buff 5) interorbital bar, bordered posteriorly by black (Dark Grayish Olive 275) blotch on top of head; irregular, dark gray-brown (Grayish Olive 273) or black (Sepia 286) crossbars on dorsal and lateral surfaces of limbs; posterior surfaces of thighs dark gray brown (Grayish Olive 273) with black (Sepia 286) mottling; belly immaculate whitish gray (Cyan White 155), throat and ventral surfaces of thighs whitish gray (Cyan White 155) with dark gray-brown (Medium Neutral Gray 298) mottling at outer margins; ventral surfaces of shank, dorsal surfaces of tarsus, and palmar and plantar surfaces dark gray brown (Medium Neutral Gray 298) with whitish-gray (Cyan White 155) mottling. Pupil diamond shaped, black (Jet Black 300) with narrow gold (Chamois 84) margin, iris light brass (Smoke Gray 266) with dark gray-brown (Grayish Olive 273) lines bisecting eye vertically and horizontally through pupil.

Color of holotype in preservative. Dorsal surfaces faded to brown (Grayish Horn Color 268) with darkbrown (Vandyke Brown 281) mottling; rostrum and top of head dark brown (Vandyke Brown 281) with light brown (Ground Cinnamon 270) interorbital bar; crossbars on limbs faded to dark brown (Vandyke Brown 281); dorsal surfaces of fingers yellow brown (Tawny Olive 17); belly immaculate creamy white (Pale Buff 1), throat and ventral surfaces of thighs creamy white (Pale Buff 1) with brown (Glaucous 289) mottling at outer margins; ventral surfaces of shank, dorsal surfaces of tarsus, and palmar and plantar surfaces dark gray brown (Dark Neutral Gray 299).

Variation. Males vary considerably in size ( Table 5) and degree of head enlargement. The most extreme head enlargement was observed in males from the type locality in Veunsai District, with the holotype being considerably larger with a more robust habitus than all other males examined. Odontoid form tends to vary with male head size: males without gross head enlargement tend to have slender, tapering, round-tipped odontoids ( Fig. 2A ), but males with gross head enlargement tend to have sharper, needle-like odontoids.

Independent t -tests showed that adult males (n = 7) and adult females (n = 6) of L. fastigatus sp. nov. are similar in head and body size and proportions, with no significant difference in BL, SVL, HL:SVL, or HL:HW (P> 0.05), a trend contrary to the generally accepted paradigm of strong male-biased size dimorphism in the L. kuhlii complex. Paratype male FMNH 262725 with well-developed nuptial pads and a gravid paratype female specimen FMNH 262729 show little differences in body proportions and it would be difficult to determine their sex in the field except for the greater odontoid length in the male and more rotund abdomen in the female.

The oviducts of paratype female FMNH 262729 contained approximately 250–300 mature ova that were pigmented on one pole.

Distribution and ecology. Limnonectes fastigatus sp. nov. is known only from Virachey National Park in Ratanakiri and Stung Treng provinces, northeastern Cambodia ( Fig. 1 ), where it occurs along small, rocky, lotic streams in hill evergreen forest, sometimes mixed with bamboo, at 160–650 m elevation ( Figs. 7 D–E). All individuals were found in shallow water or on the bank on soil, sand, gravel, or rock substrates within 3 m of water, and usually in stream sections having swift-flowing water, chutes, or small cascades. MVZ 258210 was found in a hole under a boulder at the bank of a swift stream. FMNH 262726 was found during the day at 1230 h, but all others were taken during the evening or night between 1810–2100 h. Adult male MVZ 258217 was found at night (1935 h) attending egg clutch MVZ 258251 in a pool of a 1.5 m wide swift, rocky stream. Advertisement calls and larvae of the new species are unknown.

Limnonectes fastigatus sp. nov. shares a type locality with Leptobrachella melica (Rowley, Stuart, Neang & Emmett, 2010) and Leptobrachium lunatum Stuart, Som, Neang, Hoang, Le, Dau, Potter & Rowley, 2020 .

Comparisons. Limnonectes fastigatus sp. nov. is most closely related to L. kiziriani , and these two species in turn form the sister clade to L. fragilis ( McLeod 2010; McLeod et al. 2015; Suwannapoom et al. 2016; Fig. 3 ). Limnonectes fastigatus sp. nov. differs from its sister taxon L. kiziriani by having significantly larger mean total body sizes of both sexes, with SVL of adult males 50.3–70.3 mm, mean 59.7 ± SD 7.8, n = 7 (vs. 42.7–53.9 mm, mean 48.6 ± SD 4.5, n = 7, P <0.05, in L. kiziriani ) and adult females 48.9–67.4 mm, mean 59.7 ± SD 6.0, n = 6 (vs. 40.2–55.0 mm, mean 49.1 ± SD 4.6, n = 12, P <0.005, in L. kiziriani ); by having significantly larger mean body lengths of both sexes, with BL of adult males 29.6–38.0 mm, mean 34.3 ± SD 3.4, n = 7 (vs. 23.9–29.4 mm, mean 26.6 ± SD 2.4, n = 7, P <0.0005, in L. kiziriani ), adult females 27.9–41.3 mm, mean 36.1 ± SD 4.6, n = 6 (vs. 23.2–32.9 mm, mean 29.1 ± SD 3.1, n = 12, P <0.05, in L. kiziriani ), and pooled sexes 27.9–41.3 mm, mean 35.2 ± SD 3.9, n = 13 (vs. 22.9–32.9 mm, mean 27.9 ± SD 3.3, n = 19, P <0.0001, in L. kiziriani ); by having significantly different BL-adjusted ED, IN, and NS in pooled sexes ( Table 3); and by having a significantly different male head shape ( Fig. 4B ; Table 4).

Limnonectes fastigatus sp. nov. differs from the Hainan-endemic L. fragilis by having significantly larger mean total body sizes of both sexes, with SVL of adult males 50.3–70.3 mm, mean 59.7 ± SD 7.8, n = 7 (vs. 36.3–65.8 mm, mean 46.2 ± SD 6.9, n = 30, P <0.01, in L. fragilis ) and adult females 48.9–67.4 mm, mean 59.7 ± SD 6.0, n = 6 (vs. 35.2–69.2 mm, mean 50.9 ± SD 8.3, n = 38, P <0.05, in L. fragilis ); by having significantly larger mean body length of adult males and pooled sexes, with BL of adult males 29.6–38.0 mm, mean 34.3 ± SD 3.4, n = 7 (vs. 22.3–44.7 mm, mean 30.5 ± SD 5.0, n = 30, P <0.05, in L. fragilis ) and pooled sexes 27.9–41.3 mm, mean 35.2 ± SD 3.9, n = 13 (vs. 22.1–46.7 mm, mean 32.0 ± SD 5.6, n = 68, P <0.05, in L. fragilis ); by having significantly different BL-adjusted HL in pooled sexes ( Table 3); by having males with nuptial pads on first finger [(Finger II) vs. absent in L. fragilis ; Fei et al. 2013]; and by lacking fragile skin that readily tears during capture (vs. present in L. fragilis ; Liu et al. 1973).

Although phylogenetically unrelated to the new species ( McLeod 2010; McLeod et al. 2015; Suwannapoom et al. 2016; Fig. 3 ), four additional members of the L. kuhlii complex occur in the geographic proximity of the new species in eastern Thailand, Laos, and Vietnam: L. bannaensis , L. isanensis , L. megastomias , and L. taylori . Limnonectes fastigatus sp. nov. differs from all four species by having odontoid processes thin and elongated (vs. odontoids broader, more bluntly tipped in L. bannaensis , L. isanensis , L. megastomias , and L. taylori ); by having 2–5 significantly different BL-adjusted characters in pooled sexes ( Table 3); and by having a significantly different male head shape ( Fig. 4B ; Table 4). Limnonectes fastigatus sp. nov. further differs from L. bannaensis , L. isanensis , and L. megastomias by having an immaculate belly (belly with brown flecking or vermiform markings in L. bannaensis , L. isanensis , and L. megastomias ). Limnonectes fastigatus sp. nov. further differs from L. megastomias by having significantly smaller mean body lengths of both sexes, with BL of pooled sexes 27.9–41.3 mm, mean 35.2 ± SD 3.9, n = 13 (vs. 22.8–59.1 mm, mean 43.0 ± SD 8.5, n = 25, P <0.001, in L. megastomias ). Limnonectes fastigatus sp. nov. further differs from L. taylori by having significantly larger mean body lengths of both sexes, with BL of pooled sexes 27.9–41.3 mm, mean 35.2 ± SD 3.9, n = 13 (vs. 21.1–40.2 mm, mean 30.4 ± SD 5.1, n = 19, P <0.01, in L. taylori ).

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Figures

FIGURE 1. Map illustrating the holotype (star) and paratype (square) localities of Limnonectes fastigatus sp. nov. and localities of samples of Limnonectes kiziriani (circles) and Limnonectes fragilis (triangles) used in this study.

FIGURE 2. Odontoids in male Limnonectes: (A) Limnonectes fastigatus sp. nov. (paratype MVZ 258204) in life. (B) Limnonectes fragilis (unknown voucher) in preservative. Photograph by Jing Che. (C) Limnonectes kiziriani (field tag LNT 2917) in life. Photograph by Luan Thanh Nguyen. (D) Placements of 11 landmarks on heads of preserved male specimens of Limnonectes frogs for geometric morphometric analyses.

FIGURE 3. Fifty percent majority-rule consensus phylogram resulting from Bayesian analysis of 2,504 aligned characters of mitochondrial DNA (12s, tRNA Val, 16S) from the Limnonectes kuhlii complex. Trees were rooted with Limnonectes acanthi (GenBank accession AY313721) and Limnonectes ingeri (GenBank accession KP318721; not shown). Numbers at nodes are Bayesian posterior probabilities and numbers at terminal tips are GenBank accession numbers. Voucher and locality data for newly sequenced samples are provided in Table 1.

FIGURE 4. Morphometrics of six species of Limnonectes frogs. (A) Bivariate ordination with 95% confidence ellipses of the first two linear discriminants from linear discriminant analysis of ratios of 12 measurements divided by body length (BL) from preserved males and females. (B) Bivariate ordination with 95% confidence ellipses of the first two canonical variates of 11 geometric landmarks from heads of preserved male specimens.

FIGURE 5. Limnonectes fastigatus sp. nov. in life or immediately prior to preservation. Holotype male (MVZ 258214) in (A) dorsolateral, (B) frontal, (C) dorsal, (D) ventral, and (E) facial views, and paratype male (MVZ 258204) in (F) dorsolateral view.

FIGURE 6. Holotype male (MVZ 258214) of Limnonectes fastigatus sp. nov. in preservative in (A) dorsal, (B) ventral, (C) tibiotarsal, (D) palmar and (E) plantar views.

FIGURE 7. (A) Holotype male (MVZ 258214) and paratype female (MVZ 258215) of Limnonectes fastigatus sp. nov. in preservative, photographed at scale. (B) Paratype female (MVZ 258203) in life. Photograph by Piotr Naskrecki. (C) Partial view of egg clutch (MVZ 258251) of Limnonectes fastigatus sp. nov. photographed in situ in a stream pool attended by paratype male (MVZ 258217; not shown). Hill evergreen forest at the type locality of Limnonectes fastigatus sp. nov. in Virachey National Park, Veunsai District, Ratanakiri Province, Cambodia as viewed from (D) Veal Thom Grasslands (foreground) and (E) a helicopter.