Limnonectes phuyenensis, Pham & Do & Le & Ngo & Nguyen & Ziegler & Nguyen, 2020

Pham, Cuong The, Do, Dang Trong, Le, Minh Duc, Ngo, Hanh Thi, Nguyen, Luan Thanh, Ziegler, Thomas & Nguyen, Truong Quang, 2020, A new species of Limnonectes (Amphibia: Anura: Dicroglossidae) from Vietnam, Zootaxa 4894 (3), pp. 387-402 : 390-398

Limnonectes phuyenensis sp. nov.

( Figs. 2–5 )

Holotype: IEBR 4737 (Field number DTD 138 ), adult male, collected by D. T. Do on 28 March 2015 (12°51.184 ’ N, 109°13.151 ’ E, at an elevation of 359 m asl.) in the evergreen forest of Ca Mountain Pass , near Hoa Thinh Commune, Tay Hoa District, Phu Yen Province, Vietnam.

Paratypes: 18 specimens collected from the evergreen forest of Phu Yen Province, Vietnam: One adult male, PYU 535 (Field number DTD 04 ) and two adult females, IEBR 4739 , 4740 (Field numbers DTD 163 , 171 ), collected by D. T. Do on 28 March 2015 (12°51.184 ’ N, 109°13.151 ’ E, at an elevation of 359 m asl.) from Ca Mountain Pass , near Hoa Thinh Commune , Tay Hoa District ; one adult male, IEBR 4738 (Field number DTD 535 ) and one adult female, PYU 536 (Field number DTD 536 ), collected by D. T. Do on 19 August 2015 (12°52.470 ’ N, 108°49.511 ’ E, at an elevation of 554 m asl.) from Ca Mountain Pass , near Son Thanh Tay Commune , Tay Hoa District ; one adult male, ZFMK 103169 (Field number DTD 680 ) and one adult female, ZFMK 103170 (Field number DTD 708 ), collected by D. T. Do on 10 September 2016 (13°27.437 ’ N, 108°52.005 ’ E, at an elevation of 430 m asl.) from Phu Mo Commune , Dong Xuan District ; one adult male, ITBCZ 4598 (Field number SH 040) collected by L. T. Nguyen, M. V. Le , and H. V. Lo on 26 March 2019 (12°78.549 ’ N, 109°03.737 ’ E, at an elevation of 350 m asl.); six adult males, ITBCZ 4746 , 4747 , 4749 , 4753 , 4754 (Field numbers SH 188, 189, 191, 195, 196, respectively) and VNMN 010902 (Field number SH194) and four adult females, ITBCZ 4745 , 4748 , 4750 (Field numbers SH 187, 190, 192, 193, respectively) and VNMN 010903 (Field number SH193) collected by L. T. Nguyen, M. V. Le , and H. V. Lo on 31 March 2019 (12°78.549 ’ N, 109°03.737 ’ E, at an elevation of 350 m asl.) from Song Hinh Protection Forest, Song Hinh District .

Diagnosis: Molecular and morphological data, including the presence of fang-like odontoid processes on the lower jaw and sexual dimorphism, with males larger than females and enlargement of the head in males ( Emerson et al. 2000), revealed the new species to be nested within Limnonectes .

Limnonectes phuyenensis sp. nov. is distinguishable from its congeners by a combination of the following morphological characters: (1) SVL 49.8–77.9 mm in males, 40.8–61.8 mm in females; (2) males with moderately enlarged head (HL/SVL 0.47, HW/SVL 0.48); (3) head slightly broader than long (HL/HW 0.97 in males, 0.95 in females); (4) vomerine teeth present; (5) external vocal sacs absent; (6) rostral length short (RL/SVL 0.15); (7) tympanum invisible; (8) dorsal surface of head, body and flanks with ridges and tubercles; (9) dorsal surface of tibia and foot distinctly tuberculate, covered with moderately dense, small, low tubercles; (10) supratympanic fold present; (11) dorsolateral fold absent; (12) Finger I with nuptial pad, composed of minute spines on dorsal surface and medial edge in males; (13) toes webbed to distal of terminal phalanx, webbing formala I0–0II0–0III0–0IV0 - –0V0; (14) in life, dorsum yellowish brown with dark brown markings; (15) ventral surface white with brown markings.

Description of holotype: Adult male (IEBR 4737); SVL 62.8 mm; habitus robust with enlarged head (HL/SVL 0.48, HW/SVL 0.50); head slightly broader than long (HL 30.1 mm, HW 31.2 mm); snout round anteriorly in dorsal view, projecting beyond lower jaw; nostril lateral, closer to tip of snout than to eye (NS 4.2 mm, EN 4.8 mm); canthus rostralis indistinct; loreal region oblique and slightly concave; rostral length greater than eye diameter (RL 9.0 mm, ED 7.6 mm); interorbital distance wider than internarial distance and upper eyelid width (IOD 6.4 mm, IND 5.3 mm, UEW 3.9 mm); tympanum invisible; vomerine teeth in two oblique ridges; tongue cordiform, notched posteriorly; lower jaw with two tooth-like, odontoid processes robust with very sharp tips (OH 4.0 mm); external vocal sac absent.

Forelimbs: Arms short; upper arm length (UAL) 10.8 mm, forearm length (FAL) 26.2 mm; relative finger lengths: I<II<IV<III; fingers free of webbing; dermal ridge on sides of fingers absent; tips of fingers blunt, not expanded; subarticular tubercles prominent, round, formula 1, 1, 1, 1; inner metatarsal tubercle oval, elongate; outer metatarsal tubercle small; Finger I with nuptial pad, composed of minute spines on dorsal surface and medial edge.

Hind limbs: Tibia length shorter than thigh length (FeL 28.8 mm, TbL 27.1 mm), approximately 2.2 times longer than wide (TbW 12.4 mm); tips of toes blunt, slightly round; relative length of toes: I<II<V<III<IV; toes webbed to distal of terminal phalanx, webbing formala I0–0II0–0III0–0IV0 - –0V0; dermal ridge on outer sides of toes I and V; subarticular tubercles prominent, elongate, formula 1, 1, 2, 3, 2; inner metatarsal tubercle elongate; outer metatarsal tubercle absent; tibio-tarsal articulation reaching behind eye.

Skin texture in life: Dorsal surface of head, body and flanks with ridges and tubercles; small tubercles on upper eyelid; supratympanic fold distinct, extending from eye to angle of jaw; dorsolateral fold absent; small tubercles around cloaca; dorsal surface of forelimbs and thighs smooth; dorsal surface of tibia and foot distinctly tuberculate, covered with moderately dense, small, low tubercles; throat, chest, belly and ventral surface of thighs smooth.

Coloration in life: Iris dark gray in upper half and light gray in lower half; head with a pale yellow bar in anterior interorbital region and a narrow dark brown bar in posterior interorbital region; dorsum and flanks with yellowish brown marking; lips with dark bars; supratympanic fold dark brown; dorsal surface of limbs yellowish brown with dark crossbars; ventral surface of limbs, throat, chest, and belly white with brown markings; toe webbing brown.

Coloration in preservative: Dorsum and upper part of flanks pale brown with dark brown marking; lower part of flanks white with brown marking; lips with dark bars; head with a narrow dark brown bar in anterior interorbital region; supratympanic fold dark brown; dorsal surface of limbs pale brown with dark crossbars; ventral surface of limbs, throat, chest, and belly white with brown markings; minute spines on Finger I greyish brown; toe webbing brown.

Variation and sexual dimorphism: Measurements and morphological characters of the type series are provided in Table 1 and photographs of paratypes in life are presented in Fig. 6 . Males are larger than females ( SVL 60.1 ± 8.3 mm, n = 11 males vs. 50.3± 7.3 mm, n = 8 females). Males have a larger head than females (HL/SVL 0.47 vs. 0.44, HW/SVL 0.48 vs. 0.46). The male specimens have a nuptial pad on Finger I. The males have robust fanglike odontoid processes, which are less pronounced in the females. The females contained yellowish cream eggs of varying sizes. One juvenile (unvouchered) had a yellowish dorsum with distinct brown marking ( Figure 6F ).

Etymology. The specific epithet “ phuyenensis ” refers to the type locality of the new species, Phu Yen Province. As common names we suggest Phu Yen Wart Frog (English), Ếch nhẽo phú yên (Vietnamese).

Ecological notes. Specimens were found between 19:00 and 23:00 in the head-water of small, rocky streams ( Fig. 7A ). They were found in the water or on the ground of stream banks at elevations above 300 m. Males were sometimes found in small water pools with two or three females nearby. The surrounding habitat was secondary forest of large, medium and small hardwoods mixed with shrubs and vines. Air temperature at the sites was 20.5–26.3 oC and relative humidity was 73–96%. The females collected in March, August, and September contained yellowish cream eggs of varying sizes. Male advertisement calls and tadpoles of the species have not been recorded during our field surveys. Other amphibian species found at the sites included Leptobrachella macrops (Duong, Do, Ngo, Nguyen & Poyarkov) , Megophrys elfina (Poyarkov, Duong, Orlov, Gogoleva, Vassilieva, Nguyen, Nguyen, Nguyen, Che & Mahony) , Limnonectes poilani (Bourret) , Odorrana morafkai (Bain, Lathrop, Murphy, Orlov & Ho) , Kurixalus cf. banaensis (Bourret), and Rhacophorus annamensis (Smith) .

Distribution. Limnonectes phuyenensis sp. nov. is currently known only from Phu Yen Province, South-central Vietnam ( Fig. 8 ).

Comparisons. We compared the new species with its congeners from Vietnam and neighboring countries including Laos, Cambodia, Thailand, and China.

Limnonectes phuyenensis sp. nov. differs from L. bannaensis Ye, Fei & Jiang by having a smaller size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 74.9 mm, n= 10 males, 60.8 mm, n= 8 females in L. bannaensis ), head broader than long (vs. head longer than wide in L. bannaensis ), tips of toes blunt (vs. tips of toes expanded into discs in L. bannaensis ), dorsal surface of tibia and foot with tubercles (vs. smooth in L. bannaensis ), and males with nuptial pad on Finger I (vs. males with nuptial pad on fingers I and II in L. bannaensis ); from L. coffeatus Phimmachak, Sivongxay, Seateum, Yodthong, Rujirawan, Neang, Aowphol & Stuart by having a larger size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 37.9 mm, n= 1 male, 40.5 mm, n= 3 females in L. coffeatus ), males with nuptial pad on Finger I (vs. absence in males of L. coffeatus ), tympanum invisible (vs. visible in L. coffeatus ), and the absence of W marking on head (vs. presence in L. coffeatus ); from L. dabanus (Smith) by the absence of caruncle on head in males (vs. presence in L. dabanus ), tympanum invisible (vs. visible in L. dabanus ), toes fully webbed (vs. webbing formula I0–1/3II0–1/4III0–1IV1–0V in L. dabanus ), and males with nuptial pad on Finger I (vs. absence in L. dabanus ); from L. fastigatus by having a differrent odontoid processes shape (robust with very sharp tips vs. thin and elongated in L. fastigatus ), nostril closer to tip of snout than to eye (vs. midway between snout tip and eye in L. fastigatus ), and belly with brown flecking or vermiform markings in preservative (vs. creamy white in preservative in L. fastigatus ); from L. fragilis (Liu & Hu) by having a head broader than long (vs. head longer than wide in L. fragilis ), a greater ratio of HL/SVL and HW/SVL (HL/SVL=0.47, HW/SVL=0.48, n= 11 males and HL/SVL=0.44, HW/SVL=0.46, n= 8 females vs. HL/SVL=0.45, HW/SVL=0.42, n= 6 males and HL/SVL=0.42, HW/SVL=0.41, n= 10 females in L. fragilis ), tibia length shorter than thigh length (vs. tibia length longer than thigh length in L. fragilis ), and males with nuptial pad on Finger I (vs. absence in males of L. fragilis ); from L. fujianensis Ye & Fei by having a head broader than long (vs. head longer than wide in L. fujianensis ), a greater ratio of HL/SVL and HW/SVL (HL/SVL=0.47, HW/SVL=0.48, n= 11 males and HL/SVL=0.44, HW/SVL=0.46, n= 8 females vs. HL/SVL=0.45, HW/SVL=0.44, n= 20 males and HL/SVL=0.38, HW/SVL=0.37, n= 20 females in L fujianensis ), males with nuptial pad on Finger I (vs. nuptial pad on Fingers I and II in L. fujianensis ), and the absence of W marking on head (vs. presence in L. fujianensis ); from L. gyldenstolpei (Andersson) by the absence of caruncle on head in males (vs. presence in L. gyldenstolpei ), tympanum invisible (vs. visible in L. gyldenstolpei ), toes fully webbed (vs. webbing formula I0–3/4II0–1III1/4–1IV11/2–0V in L. gyldenstolpei ), and males with nuptial pad on Finger I (vs. absence in L. gyldenstolpei ); from L. kiziriani by having larger size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 54.1 mm, n= 13 males, 46.8 mm, n= 7 females in L. kiziriani ), head broader than long (vs. longer than wide in L. kiziriani ), a smaller ratio of TbL/TbW (TbL/TbW 2.31, n= 11 males and 2.40, n= 8 females vs. TbL/TbW 2.54, n= 13 males and 2.57, n= 7 females in L. kiziriani ), and the absence of two dermal ridges parallel from posterior of eye to the end of shoulder (vs. presence in L. kiziriani ); from L. hascheanus (Stoliczka) by having a larger size (SVL 60.1 mm, n= 11 males, 50.3 mm n= 8 females vs. 22.1 mm, n= 9 males, 23.0 mm, n= 9 females of L. hascheanus ), the absence of dorsolateral folds (vs. presence in L. hascheanus ), males with nuptial pad on Finger I (vs. absence in males of L. hascheanus ), and tympanum invisible (vs. visible in L. hascheanus ); from L. isanensis McLeod, Kelly & Barley by having a smaller size in males (SVL 60.1 mm, n=11 vs. 71.5 mm, n= 11 in L. isanensis ), head broader than long (vs. head longer than wide in L. isanensis ), dorsum and flank with tubercles (vs. absence in L. isanensis ), and males with nuptial pad on Finger I (vs. nuptial pad on Fingers I and II in L. isanensis ); from L. jarujini Matsui, Panha, Khonsue & Kuraishi by having a smaller size in males (SVL 60.1 mm, n=11 vs. 73.3 mm, n= 8 in L. jarujini ), head broader than long (vs. head longer than wide in L. jarujini ), length of fingers I<II (vs. fingers II=I in L. jarujini ), and dorsum and flank with tubercles (vs. absence in L. jarujini ); from L. khammonensis (Smith) by having a larger size in females (SVL 50.3 mm, n=8 vs. 37 mm, n= 1 in L. khammonensis ) and tympanum invisible (vs. visible in L. khammonensis ); from L. kohchangae (Smith) by having a larger size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 35.9 mm, n= 21 males, 35.2 mm, n= 14 females of L. kohchangae ), tympanum invisible (vs. visible in L. kohchangae ) and males with nuptial pad on Finger I (vs. absent in L. kohchangae ); from L. limborgi (Sclater) by having a larger size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 33.0 mm, n= 30 males, 31.7 mm, n= 24 females of L. limborgi ), the absence of dorsolateral folds (vs. presence in L. limborgi ), males with nuptial pad on Finger I (vs. absence in males of L. limborgi ), and tympanum invisible (vs. visible in L. limborgi ); from L. liui (Yang) by having a larger size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 35.7 mm, n= 3 males, 32.7 mm, n= 1 female of L. liui ), tympanum invisible (vs. visible in L. liui ), and dorsolateral fold absent (vs. present in L. liui ); from L. longchuanensis Suwannapoom, Yuan, Sullivan & McLeod by having head broader than long (vs. head longer than wide in L. longchuanensis ), males with nuptial pad on Finger I (vs. nuptial pad on Fingers I and II in L. longchuanensis ), and dorsal ridges present (vs. absent in L. longchuanensis ); from L. lauhachindai Aowphol, Rujirawan, Taksinum, Chuaynkern & Stuart by having a larger size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 33.8 mm, n= 20 males, 35.2 mm, n= 4 females in L. lauhachindai ), the absence of caruncle on head (vs. presence in L. lauhachindai ), tympanum invisible (vs. visible in L. lauhachindai ), and males with nuptial pad on Finger I (vs. absence in L. lauhachindai ); from L. macrognathus (Boulenger) by having a larger size in males (SVL 60.1 mm, n=11 vs. 45.5 mm, n= 3 in L. macrognathus ), the absence of caruncle on head (vs. presence in L. macrognathus ), and tympanum invisible (vs. visible in L. macrognathus ); from L. megastomias McLeod by having a smaller size (SVL 60.1 mm, n= 11 males, 50.3 mm in, n= 8 females vs. 80.2 mm, n= 22 males, 74.0 mm, n= 11 females), head broader than long (vs. head longer than wide in L. megastomias ), dorsal surface of tibia and foot with tubercles (vs. smooth in L. megastomias ), and males with nuptial pad on Finger I (vs. nuptial pad on Fingers I and II in L. megastomias ); from L. nguyenorum by having a smaller ratio of HL/SVL (0.47, n= 11 males, 0.44, n= 8 females vs. 0.42–0.43, n= 2 males, 0.39–0.39, n= 2 females in L. nguyenorum ), the head broader than long (vs. head longer than wide in L. nguyenorum ), tibia shorter than thigh (vs. tibia longer than thigh in L. nguyenorum ), males with nuptial pad on Finger I (vs. nuptial pad on Fingers I and II in L. nguyenorum ), and the absence of two dermal ridges parallel from posterior of eye to the end of shoulder (vs. presence in L. nguyenorum ); from L. poilani (Bourret) by having a smaller size (SVL 60.1 mm, n= 11 males, 50.3 mm, n= 8 females vs. 90.0 mm, n= 4 males, 80.2 mm, n= 6 females of L. poilani ), head broader than long (vs. head longer than wide in L. poilani ), tibia shorter than thigh (vs. tibia longer than thigh in L. poilani ), tympanum invisible (vs. visible in L. poilani ), and ventral surface of limbs and abdomen white with brown markings (vs. yellow in L. poilani ); from L. quangninhensis Pham, Le, Nguyen, Ziegler, Wu & Nguyen by having a head broader than long (vs. head longer than wide in L. quangninhensis ), tympanum invisible (vs. visible in L. quangninhensis ), tibia shorter than thigh (vs. tibia longer than thigh in L. quangninhensis ), toes fully webbed (vs. webbing formula I0–0II0–1/3III0–1/3IV1/2–0V in L. quangninhensis ), and dorsal surface of tibia and foot with distinct tubercles (vs. small tubercles in L. quangninhensis ); from L. taylori Matsui, Panha, Khonsue & Kuraishi by having a head broader than long (vs. head longer than wide in L. taylori ), tympanum invisible (vs. slightly visible in L. taylori ), length of fingers I<II (vs. fingers I=II in L. taylori ), and the presence of dorsal ridges (vs. absence in L. taylori ); from L. savan Phimmachak, Richards, Sivongxay, Seateun, Chuaynkern, Makchai, Som & Stuart by the absence of caruncle on head in males (vs. presence in L. savan ), tympanum invisible (vs. visible in L. savan ), relative length of toes I<II<V<III<IV (vs. I<II<V=III<IV in L. savan ), and males with nuptial pad on Finger I (vs. absence in L. savan ).

Figures

FIGURE 2. Dorsolateral view (A) and ventral view (B) of the holotype (IEBR 4737, male) of Limnonectes phuyenensis sp. nov. in life.

FIGURE 3. Dorsolateral view (A) and ventral view (B) of the holotype (IEBR 4737, male) of Limnonectes phuyenensis sp. nov. in preservative.

FIGURE 4 Lateral view of the head (A) and shape of odontoid processes (B) of the holotype (IEBR 4737) of Limnonectes phuyenensis sp. nov.

FIGURE 5. Right hand (A), right foot (B), and dorsal view of finger I (C) of the holotype (IEBR 4737) of Limnonectes phuyenensis sp. nov.

FIGURE 6. Paratypes of Limnonectes phuyenensis sp. nov. in life (with ventral view inserted). (A) male ITBCZ 4598 (male on the right with two unvouchered females nearby on the left). (B) male ITBCZ 4753, (C) male ITBCZ 4754, (D) female ITBCZ 4750, (E) female VNMN 010903, and (F) an observed juvenile.

FIGURE 7. Habitat of Limnonectes phuyenensis sp. nov. (A) and threats to the habitat of the new species in Phu Yen Province, Vietnam: hydropower construction (B) and timber logging (C).

FIGURE 8. Map showing the type locality (purple circle) of Limnonectes phuyenensis sp. nov. in Phu Yen Province, Vietnam.