A new species of Megophrys (Amphibia: Anura: Megophryidae) from Vietnam Author Nguyen, Truong Quang Author Pham, Cuong The Author Nguyen, Tao Thien Author Luong, Anh Mai Author Ziegler, Thomas text Zootaxa 2020 2020-01-16 4722 5 401 422 journal article 24330 10.11646/zootaxa.4722.5.1 5e67f491-f0ee-4236-93d7-bdebaceccb6e 1175-5326 3609639 DCBD1DE2-06C9-4688-95E8-3021ED5E5320 Megophrys caobangensis sp. nov. ( Figs. 2 , 3 ) Holotype . IEBR 4384 (Field number CB 2015.68 ), adult male, collected by C. T . Pham & T . V . Nguyen on 13 October 2015 in the evergreen forest ( 22 o 36.675’N , 105 o 53.039’E , at an elevation of 1,252 m asl .) within Phia Oac-Phia Den National Park , Nguyen Binh District , Cao Bang Province , northeastern Vietnam . Paratypes (n = 10). Specimens collected from the forest of Phia Oac-Phia Den National Park , Nguyen Binh District , Cao Bang Province , Vietnam : two adult males IEBR 4385 , 4386 (Field numbers CB 2015.60 , 61 ), collected by C. T . Pham and T . V . Nguyen on 12 October 2015 ( 21 o 36.151’N , 107 o 52.495’E , at an elevation of 1518 m asl .) ; eight adult males IEBR 4387–4391 (Field numbers CB 2015 . 69–73), and VNMN 2019.04 – 2019.06 (Field numbers CB 2015.94 – 96 ), collected by C. T . Pham and T . V . Nguyen on 13 October 2015 ( 22 o 36.147’N , 105 o 52.726’E , at an elevation of 1461 m asl .) . Diagnosis. The new species was strongly supported as a member of Megophrys based on molecular analyses ( Fig. 1 ) and is distinguishable from its congeners by a combination of the following morphological characters (n = 11, adult males): 1) size small (SVL 34.9–38.9 mm in males); 2) tympanum visible (TD/ED 0.40–0.50); 3) vomerine teeth absent; 4) tongue not notched posteriorly; 5) vocal sac present; 6) toes with rudimentary webbing; 7) subarticular tubercles and lateral fringes absent on all digits; 8) nuptial pads with spicules on fingers I and II in males; 9) dorsal skin with scattered granules and tubercles; 10) flank with tubercles; 11) dorsum with a X-shaped dorsal ridge; 12) dorsolateral folds prominent; 13) a horn-like small tubercle present at the outer edge of the eyelid; and 14) dorsal surface yellowish brown with a dark brown triangle between the eyes and a dark brown marking along the X-shaped ridge on the back. TABLE 1 . Uncorrected (“p”) distance matrix showing percentage pairwise genetic divergences (%) for the 16SrRNA gene between members of the Megophrys species group

1	2	3	4	5	6	7	8	9	10	11	12
Megophrys caobangensis sp. nov.	-
M. acuta	10.80
M. baolongensis	8.31	7.68
M. binlingensis	4.83	9.13	5.21
M. boettgeri	6.69	7.66	3.71	4.91
M. brachykolos	10.17	8.60	6.69	9.18	6.67
M. cheni	6.68	8.23	3.69	5.46	3.39	6.04
M. daweimontis	4.52	7.29	6.13	3.65	4.87	9.46	5.15
M. fansipanensis	7.49	11.38	6.07	5.69	6.04	8.17	6.28	6.88
M. hoanglienensis	5.72	9.84	5.83	3.38	4.00	8.87	5.45	5.12	3.65
M. jingdongensis	5.44	8.86	6.13	3.08	5.82	9.87	5.49	3.39	5.72	4.84
M. jinggangensis	6.95	7.65	5.77	6.33	5.15	7.01	3.97	6.61	7.49	6.62	6.36
M. kuatunensis	6.98	8.54	4.6	6.38	3.68	5.77	3.09	6.04	6.6	6.37	7.02	5.46
M. latidactyla	7.32	8.9	8.00	6.39	7.39	10.29	7.99	5.48	9.49	7.65	7.06	8.64
M. leishanensis	7.31	7.91	3.40	4.90	2.53	6.67	3.67	5.47	5.72	4.88	5.49	4.82
M. lini	7.90	7.61	6.99	7.27	5.15	5.44	3.96	6.32	8.12	7.89	7.34	4.59
M. lishuiensis	7.98	8.67	4.93	6.78	3.71	7.70	5.21	6.73	7.33	6.79	8.71	6.73
M. minor	8.2	10.85	7.97	6.66	6.40	8.63	6.99	7.57	6.91	6.35	7.90	7.24
M. obesa	7.86	8.26	7.30	8.53	4.55	7.90	3.37	6.35	8.12	7.90	7.34	6.37
M. omeimontis	5.71	9.51	6.45	2.79	5.20	8.26	5.17	3.65	4.53	3.95	3.1	6.33
M. parva	7.85	9.53	8.32	6.33	6.10	9.56	7.29	5.42	7.23	6.34	4.27	7.56
M. rubrimera	4.26	10.51	6.46	3.38	3.98	8.90	5.47	3.38	6.3	4.55	3.11	6.94
M. spinata	4.84	9.48	5.49	1.10	5.19	9.46	4.57	3.66	5.09	3.97	3.09	6.35
M. tuberogranulata	6.69	7.28	2.24	3.69	1.96	6.36	2.52	4.87	5.71	4.29	4.58	4.25
M. wuliangshanensis	5.75	9.62	6.78	4.89	5.82	9.25	6.08	3.99	6.93	6.08	4.02	7.62
M. wushanensis	8.23	8.24	2.83	5.17	3.39	6.66	3.96	5.75	6.02	5.78	6.72	5.11

......continued on the next page TABLE 1. (Continued)

14	15	16	17	18	19	20	21	22	23	24	25
Megophrys caobangensis sp. nov.
M. acuta
M. baolongensis
M. binlingensis
M. boettgeri
M. brachykolos
M. cheni
M. daweimontis
M. fansipanensis
M. hoanglienensis
M. jingdongensis
M. jinggangensis
M. kuatunensis
M. latidactyla
M. leishanensis	7.10
M. lini	7.06	6.03
M. lishuiensis	8.43	4.60	6.39
M. minor	10.25	6.68	8.88	8.31
M. obesa	9.58	6.04	4.56	5.76	9.51
M. omeimontis	6.39	5.19	6.37	6.17	7.26	7.01
M. parva	8.63	6.67	7.34	8.98	8.86	7.92	5.44
M. rubrimera	7.35	5.20	7.92	7.40	6.99	7.29	3.38	4.26
M. spinata	7.32	5.17	6.35	7.06	7.57	7.59	2.80	6.65	3.97
M. tuberogranulata	7.39	2.23	5.43	4.60	6.06	5.43	5.18	6.70	4.60	3.97
M. wuliangshanensis	7.72	5.81	7.95	7.04	8.57	6.69	4.59	6.10	4.01	4.87	5.20
M. wushanensis	7.69	2.51	6.31	4.30	7.59	6.94	5.47	8.24	6.10	5.45	1.95	6.42

FIGURE 1. Phylogram based on the Maximum likelihood (ML) analysis (16S rRNA gene). ML inferences (ML-BS)/Bayesian posterior probabilities (BPP) are shown near the node. For GenBank accession numbers, refer to Table 2. TABLE 2. GenBank accession numbers and associated samples that used in this study.

No.	Species	Locality	Voucher	Accession	Reference
No.
1.	Megophrys acuta	Heishiding Nature Reserve,	SYS a001957	KJ579118	Li et al. 2014
2.	M. baolongensis	Guangdong, China Baolong, Chongqing, China	YPX 47798	KX811812	Chen et al. 2017
3.	M. binlingensis	Wawu Shan, Sichuan, China	KIZ 025807	KX811852	Chen et al. 2017
4.	M. boettgeri	Yangjifeng, Jiangxi, China	SYS a001673	KJ560380	Wang et al. 2014
5.	M. brachykolos	Hong Kong, China	SYS a002258	KJ560403	Wang et al. 2014
6.	M. daweimontis	Dawei Shan, Yunnan, China	KIZ 048997	KX811867	Chen et al. 2017
7.	M. cheni	Jinggangshan, Jiangxi, China	SYS a002142	KJ560398	Wang et al. 2014
8.	M. fansipanensis	Sa Pa, Lao Cai, Vietnam	VNMN 2018.01	MH514886	Tapley et al. 2018
9.	M. fansipanensis	Sa Pa, Lao Cai, Vietnam	AMS R186115	MH514887	Tapley et al. 2018
10.	M. hoanglienensis	Che Tao, Yen Bai, Vietnam	IEBR MCC.2017.86	MH514894	Tapley et al. 2018
11.	M. hoanglienensis	Che Tao, Yen Bai, Vietnam	HNUE MCC.2017.83	MH514895	Tapley et al. 2018
12.	M. jingdongensis	Wenlong, Yunnan, China	KIZ 011821	KX811874	Chen et al. 2017
13.	M. jingganensis	Taoyuandong Nature	SYS a001860	KJ560400	Wang et al. 2014
14.	M. kuatunensis	Reserve, Hunan, China Guangdong, China	SYS a003449	MF667881	Wang et al. 2017
15.	M. kuatunensis	Wuyi Shan, Fujian, China	SYS a001579	KJ560376	Wang et al. 2014
16.	M. latidactyla	Pu Mat, Nghe An, Vietnam	VNMN 5135	LC483948	This study
17.	M. latidactyla	Pu Mat, Nghe An, Vietnam	VNMN 5137	LC483949	This study
18.	M. leishanensis	Leigong, Guizhou, China	SYS a002213	MH406673	Li et al. 2018
19.	M. leishanensis	Leigong Shan, Guizhou,	KIZ 049172	KX811825	Li et al. 2018
20.	M. lini	China Taoyuandong, Hunan, China	SYS a002128	KJ560416	Wang et al. 2014
21.	M. lishuiensis	Zhejiang, China	YPX 52910	KY113085	Wang et al. 2017
22.	M. microstoma	Xiaoqiaogou Nature Reserve,	KIZ 048799	KX811914	Chen et al. 2017
23.	M. minor	Yunnan, China Emeishan, Sichuan, China	SYS a001805	KJ560387	Wang et al. 2014
24.	M. obesa	Heishiding Nature Reserve,	SYS a001956	KJ579117	Li et al. 2014
25.	M. obesa	Guangdong, China Heishiding Nature Reserve,	5025	MH406868	Liu et al. 2018
26.	M. omeimontis	Guangdong, China Emei Shan, Sichuan, China	KIZ 025765	KX811884	Chen et al. 2017
27.	M. parva	Sa Pa, Lao Cai, Vietnam	K685	JN848362	Ohler et al. 2011
28.	M. rubrimera	Lao Cai, Sa Pa, Vietnam	VNMN 2017.002	MF536420	Tapley et al. 2017
29.	M. spinata	Fanjing Shan, Guizhou,	CIB ZYC644	AY526205	Tapley et al. 2017
30.	M. synoria	China Mondolkiri, Cambodia	FMNH 262778	KY022198	Mahony et al.
31.	M. tuberogranulata	Badagongshan Nature Re-	YPX 10987	KX811823	2017 Chen et al. 2017
32.	M. tuberogranulata	serve, Hunan, China Badagongshan Nature Re-	4310	MH406801	Liu et al. 2018
33.	M. wuliangshanensis	serve, Hunan, China Huangcaoling, Yunnan,	KIZ 046812	KX811881	Chen et al. 2017
34.	M. wushanensis	China Dangyang, Chongqing, China	YPX 47799	KX811835	Chen et al. 2017
35.	Megophrys	Nguyen Binh, Cao Bang,	IEBR 4385	LC483945	This study
36.	caobangensis sp. nov. Megophrys	Vietnam Nguyen Binh, Cao Bang,	IEBR 4386	LC483946	This study
37.	caobangensis sp. nov. Megophrys	Vietnam Nguyen Binh, Cao Bang,	IEBR 4384	LC483947	This study
caobangensis sp. nov.	Vietnam

Description of holotype . Adult male; SVL 35.9 mm ; head as long as wide (HL 12.4 mm , HW 12.4 mm ); snout round anteriorly in dorsal view, projecting beyond lower jaw; nostril lateral, oval, closer to the eye than to the tip of snout (NS 2.7 mm , EN 1.7 mm ); canthus rostralis distinct; pupil horizontally oval; loreal region slightly concave and oblique; eye diameter greater than snout length (SL 4.5 mm , ED 4.9 mm ); internarial distance wider than interorbital distance and upper eyelid (IND 4.7 mm , IOD 3.5 mm , UEW 3.8 mm ); tympanum visible, oval, 43% of eye diameter (TD 2.1 mm ); vomerine teeth absent, maxillary teeth present; tongue cordiform, not notched posteriorly; vocal sac single. Forelimbs: Upper arm length (UAL) 6.7 mm , forearm length (FAL) 7.3 mm ; relative finger lengths IV<I<II<III; fingers free of webbing; tips of fingers blunt; subarticular tubercles absent; palmar tubercles indistinct; inner metatarsal tubercle oval, elongate; outer metatarsal tubercle small; fingers I and II with elongate nuptial pads( 1.82 mm on fingers I), covered by spicules. Hindlimbs: Tibia longer than thigh (FeL 16.3 mm , TbL 17.3 mm ), approximately four times longer than wide (TbW 3.9 mm ); tips of toes blunt; relative length of toes I<II<V<III<IV; toes with rudimentary webbing; subarticular tubercles absent; lateral fringes absent; tarsal fold absent; inner metatarsal tubercle elongate; outer metatarsal tubercle absent; tibio-tarsal articulation reaching to the middle of eye. FIGURE 2. Dorsolateral view (A) and ventral view (B) of the holotype (IEBR 4384, male) of Megophrys caobangensis sp. nov. in life. FIGURE 3. Dorsolateral view (A) and ventral view (B) of the holotype (IEBR 4384) of Megophrys caobangensis sp. nov. in preservative. Skin texture in life: Dorsal surface with scattered granules and tubercles; dorsum with a X-shaped ridge; dorsolateral folds prominent; a horn-like tubercle present on the outer edge of the upper eyelid; supratympanic fold dis- tinct; temporal region with small black spines; flanks with some tubercles; dorsal surface of limbs granular; throat, chest, belly and ventral surface of thigh smooth. Coloration in life: Dorsum yellowish brown with a dark brown triangle between the eyes; a dark brown marking along X-shaped ridge; flanks yellowish brown with some small black spots; tympanum dark brown; pupil black, outlined in copper-gold, iris lemon-yellow with tiny dark reticulations spreading from pupil; dorsal surface of fore and hind limbs yellowish brown with dark crossbars; throat and chest dark brown, pectoral glands white; anterior part of belly white with brown blotches, posterior part of belly white, two broad dark brown stripes on either side of belly; ventral surface of limbs dark brown with white marking, anterior part of thigh, inner metatarsal and outer metatarsal tubercles orange-red; posterior part of thigh dark brown; femoral glands white; toe webbing dark brown. Coloration in preservative: Dorsum greyish with a dark brown triangle between the eyes; a dark brown marking along X-shaped ridge; flanks greyish with some small dark spots; throat and chest brown; two broad dark brown stripes on either side of belly; dorsal surface of fore and hind limbs greyish with dark brown crossbars; posterior part of thigh dark brown; femoral gland white; toe webbing dark brown. FIGURE 4. Lateral view of the head (A), right food (B), and right hand (C) of the holotype (IEBR 4384) of Megophrys caobangensis sp. nov. Variation. Measurements and morphological characters of the type series are given in Table 3 . No female specimens were collected but all male specimens have a single vocal sac and nuptial pads with spicules on fingers I and II. Comparisons. We compared the new species with other species of Megophrys from Vietnam and neighbouring countries, including Laos , Cambodia , Thailand and southern China . Megophrys caobangensis sp. nov. can be distinguished from its congeners by morphological characters as shown in Table 4 . The new species was compared with the members of the subgenus Panophrys as listed below. Morphologically, Megophrys caobangensis sp. nov. is most similar to M. tuberogranulata Shen, Mo & Li but they are different from each other in internarial distance in males (IND 4.5–4.9 mm in the new species vs. 4.0– 4.4 mm in M. tuberogranulata ), a greater average TbL/SVL ratio in males (0.49 vs 0.46 in M. tuberogranulata ), the fourth finger being the shortest on forelimb of the new species (vs. the second finger being the shortest in M. tuberogranulata ), and anterior part of thigh orange-red, posterior part of thigh dark brown (vs. sides of thigh scarlet in M. tuberogranulata ). Megophrys caobangensis sp. nov. differs from M. acuta Wang, Li & Jin by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.57–0.71 in M. acuta ), a greater TbL/SVL ratio in males (0.45–0.52 vs. 0.38–0.45 in M. acuta ), and the absence of lateral fringes on toes (vs. narrow lateral fringes on toes in M. acuta ); from M. baolongensis Ye, Fei & Xie by having a smaller body size in males (SVL 34.9–38.9 mm vs. 41.8–45 in M. baolongensis ), tongue not notched (vs. tongue feebly notched in M. baolongensis ), and a greater average FoL/SVL ratio in males (0.69 vs. 0.42 in M. baolongensis ); from M. binchuanensis Ye & Fei by having an average ED/SL ratio>1 (vs. < 1 in M. binchuanensis ), a greater average FoL/SVL ratio in males (0.69 vs. 0.44 in M. binchuanensis ), a larger eye in males (ED 4.8–5.3 mm vs 3.4–4.0 mm in M. binchuanensis ), and the absence of lateral fringes on toes (vs. present in M. binchuanensis ); from M. binlingensis Jiang, Fei & Ye by having a smaller body size in males (SVL 34.9–38.9 mm vs. 45.1–51.0 mm in M. binlingensis ), a smaller TD/ED ratio in males (0.40–0.47 vs. 0.47–0.61 in M. binlingensis ), tongue not notched (vs. tongue feebly notched in M. binlingensis ), and the absence of lateral fringes on toes (vs. present in M. binlingensis ); from M. boettgeri (Boulenger) by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.51–0.53 in M. boettgeri ), tongue not notched (vs. tongue feebly notched in M. boettgeri ), and the absence of lateral fringes on toes (vs. present in M. boettgeri ); from M. brachykolos Inger & Romer by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.61–0.67 in M. brachykolos ), a greater average FoL/SVL ratio in males (0.69 vs. 0.41 in M. brachykolos ), and toes with rudiment of webbing (vs. at most one-fourth webbed in M. brachykolos ); from M. cheni (Wang & Liu) by having a larger body size in males (SVL 34.9–38.9 mm vs. 26.2–29.5 mm in M. cheni ), a smaller average HW/SVL ratio in males (0.34 vs. 0.42 in M. cheni ), a smaller average HL/SVL ratio in males (0.35 vs. 0.37 in M. cheni ), tongue not notched (vs. tongue notched in M. cheni ), and the absence of lateral fringes on toes (vs. present in M. cheni ); from M. daweimontis Rao & Yang by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.53–0.55 in M. daweimontis ), the absence of vomerine teeth (vs. present in M. daweimontis ) and a larger eye in males ( 4.8–5.3 mm vs. 4 mm in M. daweimontis ); from M. dongguangensis Wang, Lyu, Liu, Liao, Zeng, Zhao, Li & Wang by the absence of vomerine teeth (vs. present in M. dongguangensis ), HL/HW>1 (vs. < 1 in M. dongguangensis ), and a smaller average FoL/SVL ratio in males (0.40–0.50 vs. 0.58–0.70 in M. dongguangensis ); from M. fansipanensis Tapley, Cutajar, Mahony, Nguyen, Dau, Luong, Le, Nguyen, Nguyen, Portway, Luong & Rowley by having a smaller TD/ED ratio in males (0.40–0.47 vs 0.53–0.8 in M. fansipanensis ), a larger eye in males ( 4.8–5.3 mm vs. 2.8–4.2 mm in M. fansipanensis ), and the absence of vomerine teeth (vs. present in M. fansipanensis ); from M. hoanglienensis Tapley, Cutajar, Mahony, Nguyen, Dau, Luong, Le, Nguyen, Nguyen, Portway, Luong & Rowley by having a smaller TD/ED ratio in males (0.40–0.47 vs 0.54–0.75 in M. hoanglienensis ), a smaller average HW/ SVL ratio in males ( 0.32–0.37 mm vs. 0.37–0.42 mm in M. hoanglienensis ), and the absence of vomerine teeth (vs. present in M. hoanglienensis ); from M. huangshanensis Fei & Ye by having tongue not notched (vs. tongue feebly notched in M. huangshanensis ) and the absence of subarticular tubercles on toes (vs. present in M. huangshanensis ); from M. jingdongensis by having a smaller body size in males (SVL 41.8–45 mm vs. 53–56.5 mm in M. jingdongensis ), the absence of vomerine teeth (vs. present in M. jingdongensis ), and the absence of lateral fringes on toes (vs. lateral fringes on toes wide in M. jingdongensis ); from M. jinggangenis (Wang) by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.76–0.88 in M. jinggangenis ), the absence of vomerine teeth (vs. present in M. jinggangenis ), the absence of lateral fringes on toes (vs. lateral fringes on toes narrow in M. jinggangenis ), toes with rudiment of webbing (vs one-fourth webbed in M. jinggangenis ), and the absence of subarticular tubercles on toes (vs. present in M. jinggangenis ); from M. jiulianensis Wang, Lyu, Liu, Liao, Zeng, Zhao, Li & Wang by the absence of vomerine teeth (vs. present in M. jiulianensis ), HL/HW>1 (vs. < 1 in M. jiulianensis ), and a smaller TD/ED ratio in males (0.40–0.47 vs. 0.76–0.88 in M. jiulianensis ); from M. kuatunensis Pope by having tongue not notched (vs. tongue feebly notched in M. kuatunensis ) and the absence of lateral fringes on toes (vs. lateral fringes on toes narrow in M. kuatunensis ); from M. latidactyla Orlov, Poyarkov & Nguyen by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.85 in M. latidactyla ), the absence of vomerine teeth (vs. present in M. lactidactyla ), and the absence of lateral fringes on toes (vs. lateral fringes on toes wide in M. lactidactyla ); from M. leishanensis Li, Xu, Liu, Jiang, Wei & Wang by having the ratio HL/HW>1 (vs. < 1 in M. leishanensis ), a greater average ED/TYD ratio in males (2.0 vs. 1.7 in M. leishanensis ), and a longer foot in males (FoL 23.2–26.6 mm vs. 14.9–17.3 mm in M. leishanensis ); from M. lini (Wang & Yang) by the absence of lateral fringes on toes (vs. lateral fringes on toes distinct in M. lini ), toes with rudiment of webbing (vs. one-fourth webbed in M. lini ), and the absence of subarticular tubercles on toes (vs. distinct in M. lini ); from M. lishuiensis (Wang, Liu & Jiang) by having a larger body size in males (SVL 34.9–38.9 mm vs. 30.7–34.7 mm in M. lishuiensis ), a greater average FoL/SVL ratio in males (0.69 vs. 0.41 in M. lishuiensis ), and the presence of horn-like tubercle on outer edge of upper eyelid (vs. absent in M. lishuiensis ); from M. minor Stejneger by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.67–0.74 in M. minor ), a broader upper eyelid in males ( 3.5–4.4 mm vs. 3.0– 3.9 mm in M. minor ), a smaller tympanum diameter in males (2.0– 2.4 mm vs. 2.5–3.6 mm in M. minor ), and tongue not notched (vs. tongue feebly notched in M. minor ); from M. mufumontana Wang, Lyu, Liu, Liao, Zeng, Zhao, Li & Wang by having a larger body size in males (SVL 34.9–38.9 mm vs. 30.1–30.8 in M. mufumontana ), a smaller average TYE/TD ratio in males (0.50–0.60 vs. 0.85–1.10 in M. mufumontana ), and a smaller TD/ED ratio in males (0.40–0.47 vs. 0.51–0.58 in M. mufumontana ); from M. nakunensis Wang, Lyu, Liu, Liao, Zeng, Zhao, Li & Wang by the absence of vomerine teeth (vs. present in M. nakunensis ), a larger body size in males (SVL 34.9–38.9 mm vs. 29.9–34.9 mm in M. nakunensis ), and a greater TbL/SVL ratio in males (0.45–0.52 vs. 0.35–0.42 in M. nakunensis ); from M. nanlingensis Wang, Lyu, Liu, Liao, Zeng, Zhao, Li & Wang by the absence of vomerine teeth (vs. present in M. nanlingensis ), a smaller average FoL/SVL ratio in males (0.40–0.50 vs. 0.61–0.73 in M. nanlingensis ), and smaller average TYE/TD ratio in males (0.50–0.60 vs. 0.67–0.97 in M. nanlingensis ); from M. obesa Wang, Li & Zhao by having an average HL/HW ratio>1 (vs. < 1 in M. obesa ), a smaller TD/ED ratio in males (0.40–0.47 vs. 0.66 in M. obesa ), an average HL/HW ratio>1 (vs. HL/HW< 1 in M. obesa ), and a larger eye diameter in males ( 4.8–5.3 mm vs. 4.1 mm in M. obesa ); from M. ombrophila Messenger, Dahn, Liang, Xie, Wang & Lu having a larger body size in males (SVL 34.9–38.9 mm vs. 27.4–34.5 mm in M. ombrophila ), a smaller TD/ED ratio in males (0.40–0.47 vs. 0.53–0.61 M. ombrophila ), and a greater TbL/SVL ratio in males (0.45–0.52 vs. 0.33–0.41 in M. ombrophila ); from M. omeimontis Liu by having a smaller body size in males (SVL 34.9–38.9 mm vs. 56–59.5 mm in M. omeimontis , the absence of vomerine teeth (vs. present in M. omeimontis ), the absence of lateral fringes on toes (vs. lateral fringes on toes narrow in M. omeimontis ), and the absence of subarticular tubercles on toes (vs. present in M. omeimontis ); from M. palpebralespinosa Bourret by having a smaller TD/ED ratio in males (0.40–0.47 vs. 0.50–0.57 in M. palpebralespinosa ), the absence of vomerine teeth (vs. present in M. palpebralespinosa ), the absence of lateral fringes on toes (vs. lateral fringes on toes narrow in M. palpebralespinosa ), toes with rudiment of webbing (vs. at least one-fourth webbed in M. palpebralespinosa ), and the absence of subarticular tubercles on toes (vs. present in M. palpebralespinosa ); from M. parva (Boulenger) by having absence of vomerine teeth (vs. present in M. parva ), a smaller average HW/SVL ratio in males (0.34 vs. 0.36 in M. parva ), and a larger FoL/SVL ratio in males (0.69 vs. 0.47 in M. parva ); from M. rubrimera Tapley, Cutajar, Mahony, Chung, Dau, Nguyen, Luong & Rowley by having a larger body size in males ( 34.9–38.9 mm vs. 26.7–30.4 mm in M. rubrimera ), a smaller TD/ED ratio in males (0.40–0.47 vs. 0.58–0.76 in M. rubrimera ), and the absence of vomerine teeth (vs. present in M. rubimera ); from M. spinata Liu & Hu by having a smaller body size in males ( 34.9–38.9 mm vs. 47.2–54.4 mm in M. spinata ), tongue not notched (vs. feebly notched in M. spinata ), the absence of lateral fringes on toes (vs. present in M. spinata ), toes with rudiment of webbing (vs. at least one-fourth webbed in M. spinata ), and the absence of subarticular tubercles on toes (vs. present in M. spinata ); from M. wugongensis Wang, Lyu, Liu, Liao, Zeng, Zhao, Li & Wang by having a greater TbL/SVL ratio in males (0.45–0.52 vs. 0.37–0.44 in M. wugongensis ), HL/HW>1 (vs. < 1 in M. wugongensis ), and a smaller TD/ED ratio in males (0.40–0.47 vs. 0.51–0.58 in M. wugongensis ); from M. wuliangshanensis Ye & Fei by having a larger body size in males ( 34.9–38.9 mm vs. 27.3–31.6 mm in M. wuliangshanensis ), the presence of horn-like tubercle on outer edge of upper eyelid (vs. absence in M. wuliangshanensis ), a smaller average HW/SVL ratio in males (0.34 vs. 0.36 in M. wuliangshanensis ) and a greater average FoL/SVL ratio in males (0.69 vs. 0.48 in M. wuliangshanensis ); and from M. wushanensis Ye & Fei by the presence of horn-like tubercle at edge of upper eyelid (vs. absence in M. wushanensis ), the absence of lateral fringes on toes (vs. lateral fringes on toes wide in M. wushanensis ), and the absence of subarticular tubercles on toes (vs. present in M wushanensis ). TABLE 3. Measurements (in mm) and proportions of the type series of Megophrys caobangensis sp. nov. (H = holotype, P = paratype, for other abbreviations see Material and methods).

Specimen ID	IEBR 4384	IEBR 4385	IEBR 4386	IEBR 4387	IEBR 4388	IEBR 4389	IEBR 4390	IEBR 4391	VNMN 2019.04	VNMN 2019 05	VNMN 2019.06
Sex	M	M	M	M	M	M	M	M	M	M	M	Min-Max	Mean±SD
Type status	H	P	P	P	P	P	P	P	P	P	P	(n=11)	(n=11)
SVL	35.9	35.0	34.9	35.5	36.0	36.5	38.0	37.5	38.9	38.3	38.3	34.9–38.9	36.9±1.5
HL	12.4	12.3	12.2	12.5	12.9	13.1	12.7	12.6	12.9	13.4	12.8	12.2–13.4	12.37±0.36
HW	12.4	12.2	12.0	12.4	12.3	12.6	12.8	12.4	12.9	12.9	12.8	12.0–12.9	12.52±0.31
MN	9.0	8.1	8.5	8.5	9.0	8.9	8.3	8.0	9.0	9.4	8.7	8.0–9.4	8.63±0.44
MFE	8.1	7.2	7.7	7.2	8.1	7.4	7.1	6.9	8.1	8.5	7.2	6.9–8.5	7.52±0.52
MBE	3.5	3.3	3.5	3.3	3.9	3.1	3.7	3.5	4.0	3.7	3.6	3.1–4.0	3.55±0.27
SL	4.5	4.1	4.4	4.3	4.4	4.5	4.8	4.4	4.6	4.6	4.5	4.1–4.8	4.47±0.17
ED	4.9	4.9	5.2	4.8	4.9	5.2	5.1	5.2	5.0	5.3	4.9	4.8–5.3	5.05±0.18
UEW	3.8	4.1	3.5	3.7	3.7	4.4	4.2	3.9	3.9	4.1	4.1	3.5–4.4	3.96±0.27
IND	4.7	4.6	4.5	4.5	4.7	4.5	4.8	4.7	4.9	4.8	4.8	4.5–4.9	4.68±0.14
IOD	3.5	3.4	3.1	3.5	3.4	4.2	3.7	3.5	3.3	3.7	3.5	3.1–4.2	3.51±0.3
DAE	6.8	6.9	6.9	7.1	7.2	7.2	7.1	7.0	7.7	7.4	7.3	6.9–7.7	7.17±0.26
DPE	9.8	10.3	10.1	10.4	10.6	11.0	10.1	10.4	10.8	11.0	11.1	10.1–11.1	10.59±0.37
NS	2.7	2.5	2.8	2.6	2.7	2.7	2.7	2.8	2.9	2.9	2.8	2.5–2.9	2.73±0.13
EN	1.7	1.7	1.8	1.5	1.6	2.0	1.7	1.6	1.8	1.6	1.8	1.5–2.0	1.7±0.14
TD	2.1	2.0	2.3	2.2	2.3	2.2	2.4	2.3	2.0	2.4	2.2	2.0–2.4	2.23±0.14
TYE	1.1	1.0	1.1	1.1	1.3	1.1	1.1	1.0	1.2	1.2	1.4	1.0–1.4	1.16±0.14
UAL	6.7	6.3	6.9	6.5	6.3	8.1	7.2	6.3	6.6	7.1	7.0	6.3–8.1	6.83±0.55
FAL	7.3	7.1	6.8	6.8	7.3	7.6	7.1	6.8	7.6	7.0	6.9	6.8–7.6	7.12±0.53

......continued on the next page TABLE 3. (Continued)

Specimen ID	IEBR 4384	IEBR 4385	IEBR 4386	IEBR 4387	IEBR 4388	IEBR 4389	IEBR 4390	IEBR 4391	VNMN2019.04	VNMN2019.05	VNMN2019.06
Sex	M	M	M	M	M	M	M	M	M	M	M	Min-Max	Mean±SD
Type status	H	P	P	P	P	P	P	P	P	P	P	(n=11)	(n=11)
TFL	6.5	6.3	6.3	6.4	6.7	6.7	6.8	6.3	6.4	6.1	6.3	6.1–6.8	6.41±0.23
IPT	2.1	2.5	2.6	2.5	2.6	2.2	2.6	2.1	2.6	2.8	2.3	2.1–2.8	2.48±0.21
OPT	1.7	1.6	2.1	2.0	1.8	2.1	2.1	1.5	2.1	1.8	1.9	1.5–2.1	1.9±0.23
FeL	16.3	16.6	16.2	16.1	16.9	17.2	16.9	15.7	16.4	17.4	16.7	15.7–17.4	16.6±0.53
TbL	17.3	17.4	17.1	17.5	17.6	18.9	18.4	17.1	18.9	18.5	18.4	17.1–18.9	17.89±0.71
TbW	3.9	4.6	4.6	4.4	4.8	4.5	4.8	4.6	5.1	4.9	4.7	4.4–5.1	4.71±0.22
FoL	14.6	15.2	14.7	15.1	14.9	14.4	17.2	15.4	15.2	16.1	16.0	14.4–17.2	15.35±0.81
IMT	2.2	2.5	2.5	2.4	2.1	2.4	2.7	2.0	2.6	2.5	2.3	2.0–2.7	2.39±0.21
HL/SVL	0.4	0.4	0.4	0.4	0.4	0.4	0.3	0.3	0.3	0.4	0.3	0.3–0.4	0.35±0.01
HW/SVL	0.3	0.4	0.3	0.4	0.3	0.3	0.3	0.3	0.3	0.3	0.3	0.3–0.4	0.34±0.01
HL/HW	1.0	1.0	1.0	1.0	1.1	1.0	1.0	1.0	1.0	1.0	1.0	1.0–1.1	1.02±0.02
SL/ED	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.9	0.89±0.03
TD/ED	0.4	0.4	0.5	0.5	0.5	0.4	0.5	0.4	0.4	0.5	0.5	0.4–0.5	0.44±0.02
SL/HL	0.4	0.3	0.4	0.4	0.3	0.3	0.4	0.4	0.4	0.4	0.4	0.3–0.4	0.35±0.01
TYE/TD	0.5	0.5	0.5	0.5	0.6	0.5	0.5	0.5	0.6	0.5	0.6	0.5–0.6	0.52±0.07
NS/EN	1.6	1.5	1.6	1.8	1.7	1.4	1.6	1.8	1.7	1.8	1.5	1.4–1.8	1.62±0.13
UAL/SVL	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.19±0.22
FAL/SVL	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.4	0.4	0.5	0.5	0.4–0.5	0.46±0.01
FeL/SVL	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.4	0.4	0.5	0.4	0.4–0.5	0.45±0.02
TbL/SVL	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.5	0.49±0.02
FoL/SVL	0.4	0.4	0.4	0.4	0.4	0.4	0.5	0.4	0.4	0.4	0.4	0.4–0.5	0.42±0.02
TbL/TbW	4.4	3.8	3.7	4.0	3.6	4.2	3.8	3.7	3.7	3.8	3.9	3.6–4.2	3.82±0.18

TABLE 4. Mensural and meristic data of Megophrys caobangensis sp. nov . compared with 58 recognized species from Vietnam and neighboring countries (excluding M. nankiangensis [subgenus Atympanophrys ]). Characters: 1. SVL in males (mm); 2. SVL in females (mm); 3. ratio TD/ED in males; 4. ratio TbL/SVL in males; 5. Horn-like tubercle at edge of upper eyelid absent (0), small (1), slightly larger (2), long point (3); 6. Vomerine teeth absent (0), present (1); 7. Vocal sac absent (0), present (1); 8. Tongue not notched (0), feebly notched (1), notched (2); 9. Lateral fringes on toes absent (0), narrow (1), wide (2); 10. Toes without webbing (0), with rudiment of webbing (1), at most one-fourth webbed (2), at least one-fourth webbed (3); 11. Subarticular tubercles on toes absent (0), indistinct (1), distinct (2). Data in bold: diagnostic characters.? = data not available. Data sources: (1) Boulenger (1908) , (2) Smith (1921) , (3) Pope (1929) , (4) Bourret (1937) , (5) Bourret (1942) , (6) Liu et al . (1950) , (7) Inger & Romer (1961) , (8) Taylor (1962) , (9) Kou (1985) , (10) Fei et al. (1992) , (11) Manthey & Grossman (1997), (12) Rao et al . (1997) , (13) Huang et al. (1998) , (14) Orler et al. (2002), (15) Ohler (2003) , (16) Xu et al . (2005) , (17) Stuart et al . (2006) , (18) Chan-ard et al. (2007), (19) Ye et al . (2007) , (20) Jiang et al . (2008) , (21) Fei et al. (2009) , (22) Fei et al . (2010) , (23) Mo et al. (2010) , (24) Mahony (2011), (25) Mahony et al . (2011) , (26) Wang et al . (2012) , (27) Liao et al . (2013) , (28) Mahony et al . (2013) , (29) Neang et al. (2013) , (30) Shen et al. (2013) , (31) Li et al. (2014) , (32) Lv et al. (2014), (33) Wang et al . (2014) , (34) Zhao et al. (2014) , (35) Le et al. (2015) , (36) Orlov et al . (2015) , (37) Nguyen et al. (2016) , (38) Deuti et al. (2017), (39) Poyarkov et al. (2017) , (40) Tapley et al. (2017) , (41) Wang et al. (2017a) , (42) Wang et al. (2017b) , (43) Zhang et al. (2017) , (44) Tapley et al. (2018) , (45) Li et al. (2018) , (46) Wang et al. (2019) , (47) Messenger et al. (2019).

Species	1	2	3	4	5	6	7	8	9	10	11	Data source
Megophrys caobangenis sp. nov.	34.9–38.9	?	0.40–0.47	0.45–0.52	1	0	1	0	0	1	0	This study
M. aceras	55.8–62.4	88	0.50–0.67	0.42–0.46	1	1	0	1 or 0	?	1 or 2	0	1, 8, 11
M. acuta	27.1–33.0	28.1–33.6	0.57–0.71	0.38–0.45	1	0	1	0	1	1	0	31
M. auralensis	71.0–76.9	?	?	?	1	0 or 1	1	0	0	1	1	14, 29
M. baolongensis	41.8–45.0	?	0.39–0.41	0.44–0.46	1	0	1	1	0	0	0	19, 21, 22
M. binchuaensis	32.0–36.0	40.2–42.5	?	0.46–0.48	0	0	1	1 or 0	2	1	1	21, 22
M. binlingensis	45.1–51.0	?	0.47–0.61	0.52–0.53	0	0	1	1	2	1	2	21, 22
M. boettgeri	34.5–37.8	39.7–46.8	0.51–0.53	0.48–0.49	1	0	1	1	2	1	0	21, 22
M. brachykolos	33.7–39.3	33.9–45.9	0.61–0.67	0.59–0.63	1	0	1	0	0	2	1	7, 21, 22
M. carinense	91.6–112.5	137	?	0.37	3	1	1	1 or 0	1	2	0	1, 6, 8, 21, 22
M. caudoprocta	70.8–81.3	77.8	?	0.5	2	1	0	0	?	1	0	21, 22, 30
M. cheni	26.2–29.5	31.8–34.1	0.41–0.54	0.5–0.56	1	0	1	2	2	1	1	33
M. chuannanensis	91.4–109.4	119.6	?	0.39	3	1	1	1	1	1	1	21, 22, 32, 34
M. damrei	47.7–54.5	69.1	?	?	0	1	1	2	0	1	0	24, 29
M. daweimontis	32.6–33.2	45.6–45.8	0.53–0.55	0.52	1	1	1	0	0	0	0	10, 21, 22, 35
M. dongguanensis	30.2–39.3	?	0.42–0.6	0.41–0.46	1	1	1	0	0	1	1	46
M. elfina	26.9–33.9	35.1–36.5	0.49–0.63	?	1	0	1	0	0	1	0	39
M. fansipanensis	30.9–44.3	41.7–42.5	0.53–0.8	0.49–0.59	1	1	1	1	0	0	0	44

......continued on the next page TABLE 4. (Continued)

Species	1	2	3	4	5	6	7	8	9	10	11	Data source
M. feae	78.0–101.8	91.0–113.5	?	0.38	3	1	1	1	1	1	1	8, 18, 21, 22, This study
M. gerti	31.7–42.2	43.1–47.4	?	?	3	0	1	0	0	1	0	15, 39
M. gigantica	80.5–107	110.4–115.4	Hidden	0.49–0.45	0	0	1	2	2	1	0	21, 22
M. glandulosa	76.3–81.0	76.5–99.5	0.5	0.54–0.59	1	1	1	1	2	1	0	10, 13, 21, 22
M. hansi	33.4–43.1	45.1–53.9	?	?	2	0	1	0	0	1	1	15, 39
M. huangshanensis	36–41.6	44.2	0.46–0.49	0.43–0.47	1	0	1	1	0	0	2	21, 22
M. hoanglienensis	37.4–47.6	59.6	0.542–0.75	0.44–0.63	1	1	1	1	1 or 0	1	0	44
M. insularis	36.8–41.2	47.1	0.46–0.57	0.40–0.43	1	1	1	1	0	0	1	42
M. intermedia	86.0–103.0	63–92	?	?	3	1	1	1	1	2	1	2, This study
M. jingdongensis	53–56.5	63.5	?	0.58–0.61	1	1	1	1	2	3	0	21, 22, 37
M. jinggangensis	35.1–36.7	38.4–41.6	0.76–0.88	0.47–0.5	2	1	1	0	1	2	2	26
M. jiulianensis	30.4–33.9	34.1–37.5	0.5–0.59	0.44–0.48	1	1	1	1	0	1	1	46
M. koui	28.0–30.0	25.0–26.0	?	0.48	2	0	1	2	1	0	0	9, 21, 22
M. kuatunensis	28.8–31.4	26.6–37.3	0.33–0.46	0.43–0.48	1	0	1	1	1	0	0	3, 21, 22, 40
M. latidactyla	38.9–38.9	?	0.85	0.52	1	1	?	0	2	3	2	36
M. leishanensis	30.4–38.7	42.3	0.6	0.47	1	0	1	0	0	1	0	45
M. lekaguli	55.6–66.6	71.4–94.0	0.59–0.74	0.47–0.52	1	1	0	0	0	1	0	17, 29
M. liboensis	34.7–67.7	60.8–70.6	0.47–0.61	0.48–0.51	3	1	1	2	0	1	1	43
M. lini	34.1–39.7	37–39.9	0.40–0.60	0.46–0.53	1	0	1	0	2	2	2	31
M. lishuiensis	30.7–34.7	36.9–40.4	0.34–0.55	0.43–0.51	0	0	?	0	0	0	0	41
M. longipes	47	65	?	0.57	1	1	1	1	?	1	0	1, 8, 11
M. major	77	94	0.44	0.53	1	1	1	1	1	3	0	1, 5
M. mangshanensis	62.5–73.1	73.0–86.2	?	0.46–0.52	1	1	1	1	0	0	0	10, 13, 21, 22
M. maosonensis	58.0–76.0	68.0–93.5	0.42–0.67	0.50–0.60	1	1	2	1	1	1	0	4, 5, This study
M. medogensis	57.2–68	?	0.4	0.56	1	1	1	1	0	1 or 0	0	21, 22
M. microstoma	28.0–36.0	46.5–48.5	?	0.46	3	0	1	0	0	1	0	5, 15, 21, 22, This study
M. minor	32.2–40.5	42.0–48.2	0.67–0.74	0.45–0.49	1	0	1	1	0	1	0	6, 21, 22, 43
M. mufumontana	30.1–30.8	36.3	0.51–0.58	0.47–0.53	1	0	0	0	1	1	1	46

......continued on the next page TABLE 4. (Continued)

Species	1	2	3	4	5	6	7	8	9	10	11	Data source
M. nankunensis	29.9–34.9	39.4–41.9	0.43–0.61	0.35–0.42	1	1	1	0	0	1	1	46
M. nanlingensis	30.4–37.3	?	0.43–0.57	0.45–0.51	1	1	1	1	1	1	1	46
M. nasuta	72.0–82.0	135	?	0.36–0.39	2	0	1	0	0	1	?	1, 5, 8, 11
M. obesa	35.6	37.5–41.2	0.66	0.44	1	0	?	0	1	1	2	31
M. ombrophila	27.4–34.5	32.8–35.0	0.53–0.61	0.33–0.41	1	0	?	0	0	0	0	47
M. omeimontis	56–59.5	68.0–72.5	?	0.55–0.56	1	1	1	1	1	1	2	6, 21, 22
M. pachyproctus	35.3–36.2	35.8	0.35	0.48–0.49	0	1	1	1	0	0	1	13, 21, 22
M. palpebralespinosa	33.0–35.5	39.0–41.0	0.50–0.57	0.50–0.57	2	1	1	0	2	3	1	4, 21, 22, This study
M. parva	35.6–50.6	41.5–44.8	?	0.42–0.50	1	1	1	0	0	1 or 0	1	1, 5, 21, 22, 38
M. popei	70.7–83.5	86.2	?	0.38–0.43	3	1	1	2	2	3	1	34
M. rubrimera	26.7–30.5	?	0.58–0.76	0.48–0.56	1	1	1	0	1	0	0	40
M. sangzhiensis	53–60.8	73	?	0.58	1	0	1	1	1	1	2	21, 22
M. shapingensis	65.9–84.2	77.6–104.0	hidden	0.50–0.51	0	0	0	1	2	3	0	6, 21, 22
M. shuichengensis	99.8–115.6	102.0–118.3	0.62–0.65	0.46–0.48	2	0	0	1	2	3	0	21, 22
M. spinata	47.2–54.4	54.0–55.0	0.36–0.45	0.55–0.57	0	0	1	1	2	3	2	21, 22
M. synoria	38.2–53.7	51.4–70.7	0.65–0.85	?	3	0	1	0	0	1	1	17, 39
M. takensis	47.3–53	47.3–53.0	0.72–0.76	0.45–0.46	0	1	1	0	0	1	0	25, 29
M. tuberogranulata	33.2–39.6	50.5	0.42–0.48	0.41–0.49	1	0	1	0	0	1	0	23
M. wawuensis	34.4–42.8	47.4–49.8	0.39–0.41	0.50–0.52	0	0	1	1	0	1	0	21, 22
M. wugongensis	31.0–34.1	38.5–42.8	0.43–0.53	0.37–0.44	1	0	1	0	0	1	1	46
M. wuliangshanensis	27.3–31.6	41.0–41.5	0.46–0.49	0.51–0.52	0	0	1	1 or 0	0	0	0	21, 22
M. wushanensis	30.4–35.5	38.4	0.49–0.52	0.47–0.48	0	0	1	0	2	1	2	21, 22
M. zhangi	32.5–37.2	?	0.5	0.49	0	1	1	1	1	0	0	21, 22

Etymology. The specific epithet “ caobangensis ” refers to the type locality of the new species, Cao Bang Province in northeastern Vietnam . For the common names, we suggest “ Cao Bang Spadefoot Toad” (English), and “Cóc mắt cao bằng” (Vietnamese). Ecological notes. Specimens were found between 19:00 and 23:00 h in rocky streams of Phia Oac-Phia Den National Park, Nguyen Binh District, Cao Bang Province , Vietnam ( Fig. 5 , 6 ). Most specimens were found on leaves of trees, ca. 0.2–0.5 m above the ground. No calls or tadpoles of this species were recorded or collected. The surrounding habitat was secondary evergreen forest of medium and small hardwoods mixed with bamboo, shrubs and vines. Air temperature at the site was 18.1–25.0 oC and relative humidity was 65–88%. Other amphibian species found at the site were Amolops ricketii (Boulenger) , Quasipaa boulengeri (Günther) , Odorrana geminata Bain, Stuart, Nguyen, Che and Rao , O. nasica (Boulenger) , Rana johnsi (Smith) , and Raorchestes parvulus (Boulenger) . Distribution. Megophrys caobangensis sp. nov. is currently known only from the type locality in Cao Bang Province , northeastern Vietnam ( Fig. 6 ). It is expected that this species may occur in the nearby evergreen forest in northeastern Vietnam and potentially in neighboring Guangxi Province , China .