Taxonomic revision of Amolops chunganensis (Pope,1929) (Amphibia: Anura) and description of a new species from southwestern China, with discussion on Amolops monticola group and assignment of species groups of the genus Amolops

Ke Jiang, Jin-Long Ren,2, Zhi-Tong Lyu, Dan Wang,2, Zeng Wang,2, Ke Lv, Jia-Wei Wu, Jia-Tang Li,＊

1 CAS Key Laboratory of Mountain Ecological Restoration and Bioresource Utilization & Ecological Restoration and Biodiversity Conservation Key Laboratory of Sichuan Province, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, Sichuan 610041, China

2 University of Chinese Academy of Sciences, Beijing 100049, China

3 State Key Laboratory of Biocontrol/ The Museum of Biology, School of Life Sciences/School of Ecology, Sun Yat-Sen University,Guangzhou, Guangdong 510275, China

4 Swild Studio, Chengdu, Sichuan 610015, China

5 Chengdu Expert Advisory Committee for Wildlife Conservation and Epidemic Prevention, Chengdu, Sichuan 610000, China

ABSTRACT Amolops chunganensis is a species complex and reported widely from eastern, southern, and southwestern China. Based on molecular data of 19 populations of A. chunganensis sensu lato from China, including the population from Mt. Wuyi (type locality), we recognize A. chunganensis sensu stricto and provide an expanded description based on the topotypic specimens. Combining morphological and molecular data, we describe a new species, Amolops chaochin sp. nov., from southwestern China, which was previously identified as A. chunganensis. The new species is distinguished from all other species in the A. monticola group by: (1) moderate body size,SVL 35.3−39.2 mm in males (n=7), and 50.5−54.4 mm in females (n=7); (2) distinct tympanum, larger than half of eye diameter; (3) small tooth-like projection on anteromedial edge of mandible; (4)circummarginal groove on all fingers; (5) white tubercles on dorsal side of posterior body in both sexes; (6) distinct tubercles on dorsal thigh and white spinose tubercles on dorsal tibia in both sexes; (7)white tubercles on posterior region of tympanum in males; (8) toe webbing reaching disk by dermal fringe on inner side of toe II; (9) vomerine teeth present; (10) transverse bands on dorsal limbs;(11) external vocal sacs present in males. We further reviewed the assignment of Amolops groups, with an overall revision of membership and diagnosis of all species groups.

Keywords: Amolops chaochin sp. nov.; Complex;Distribution;Amolops gerbillus; Amolops chayuensis group; Amolops spinapectoralis group

lNTRODUCTlON

The genusAmolopsCope, 1865 currently contains 69 species distributed from Nepal, northern India, western and southern China to Malaya (Frost, 2021). At least eight species groups have been suggested to accommodate these species (Fei et al., 2009b; Lyu et al., 2019b; Wu et al., 2020; Zeng et al.,2020):A. daiyunensisgroup,A. hainanensisgroup,A.larutensisgroup,A. mantzorumgroup,A. marmoratusgroup,A. monticolagroup,A. rickettigroup, andA. viridimaculatusgroup. Nevertheless, several species are unassigned to any group, and the membership of certain groups remains controversial. For example, Wu et al. (2020) recently proposed theA. viridimaculatusandA. larutensisgroups, with the former containing two recognized species,A. medogensisandA. viridimaculatus, transferred from theA. marmoratusandA.mantzorumgroups, respectively (Fei et al., 2009b; Lyu et al.,2019b). Although the morphological characters of theA.viridimaculatusgroup are provided in the literature,morphological revisions of the latter two groups are still lacking (Wu et al., 2020).

TheA. monticolagroup contains 21 species, diagnosed with smooth skin, dark lateral side of head, light-colored upper lip stripe extending to shoulder, and distinct dorsolateral folds(Che et al., 2020; Gan et al., 2020a, 2020b; Jiang et al., 2016;Yu et al., 2019). The species includeA. aniqiaoensisDong,Rao & Lü, 2005,A. akhaorumStuart, Bain, Phimmachak &Spence, 2010,A. archotaphus(Inger & Chanard, 1997),A.bellulusLiu, Yang, Ferraris & Matsui, 2000,A. chakrataensisRay, 1992,A. chunganensis(Pope, 1929),A. compotrix(Bain,Stuart & Orlov, 2006),A. cucae(Bain, Stuart & Orlov, 2006),A. chayuensisSun, Luo, Sun & Zhang, 2013,A. daorum(Bain, Lathrop, Murphy, Orlov & Ho, 2003),A. dengJiang,Wang & Che, 2020,A. gerbillus(Annandale, 1912),A. iriodes(Bain & Nguyen, 2004),A. mengyangensisWu & Tian, 1995,A. monticola(Anderson, 1871),A. mengdingensisYu, Wu &Yang, 2019,A. nyingchiensisJiang, Wang, Xie, Jiang & Che,2016,A. putaoensisGan, Qin, Lwin, Li, Quan, Liu & Yu, 2020,A. tuanjieensisGan, Yu & Wu, 2020,A. vitreus(Bain, Stuart &Orlov, 2006), andA. wenshanensisYuan, Jin, Li, Stuart & Wu,2018. Within this group, the assignment of two species is disputed. BothA. gerbillusandA. chayuensiswere placed in this group due to the presence of dorsolateral folds (Fei et al.,2005, 2009b; Sun et al., 2013). Nevertheless, the addition ofA. gerbillusto theA. monticolagroup was questioned by Stuart et al. (2010) due to its divergent morphology from other species within the group, e.g., presence of large compressed longitudinal tubercles on dorsum and lack of dark side of head and light-colored upper lip stripe. At present, however, most studies still includeA. gerbillusin theA. monticolagroup (Gan et al., 2020a, 2020b; Jiang et al., 2016; Wu et al., 2020; Yu et al., 2019; Yuan et al., 2018).Amolops chayuensiswas phylogenetically separated from other species within theA.monticolagroup based on mitochondrial sequencing data(Che et al., 2020; Gan et al., 2020a, 2020b; Jiang et al., 2016;Lyu et al., 2019b; Zeng et al., 2020) and was suggested to represent a new species group but without formal establishment (Zeng et al., 2020). Additionally, according to the original species description,A. kohimaensisBiju, Mahony& Kamei, 2010 should be a member of theA. monticolagroup based on morphological characteristics.

Amolops chunganensiswas originally described from Kuatun (now spelled as Guadun), a small village in Mt. Wuyi located at the border between Fujian and Jiangxi (Pope,1929), and was reported in Sichuan by Liu (1940, 1941). It has since been widely recorded in Anhui, Chongqing, Gansu,Guangdong, Guangxi, Guizhou, Hunan, Jiangxi, Shaanxi,Yunnan, and Zhejiang (AmphibiaChina, 2021; Fei et al.,2009b). Based on molecular phylogenetic analyses, Wu et al.(2020) revealed thatA. chunganensisshows relatively high genetic divergence and may contain several undescribed cryptic species.

In the present study, we reconstructed the phylogenetic relationships within theA. monticolagroup based on 19 populations ofA. chunganensissensu latofrom China,including the population close to its type locality in Mt. Wuyi.Phylogenetic evidence indicated thatA. chunganensis sensu latoforms three distinct clades, as reported in Wu et al.(2020), which likely contain at least two undescribed species.Based on the specimens from Mt. Wuyi, we confirmed and redescribed the phylogenetic position ofA. chunganensis sensu strictoand described a new species previously misidentified asA. chunganensisfrom Sichuan, southwestern China. Additionally, we reviewed the assignment of species groups in the genus. We established theA. chayuensisandA.spinapectoralisgroups, revised membership and diagnostic characters for all species groups, and provided a speciesgroup key and new species key of theA. monticolagroup in China.

MATERlALS AND METHODS

Sampling

A total of 18 specimens were collected, including 14 specimens from Chengdu (Sichuan) and four specimens from Mt. Wuyi (Yanshan county, Jiangxi). Following euthanasia, all specimens were fixed in 10% formalin solution after liver tissue sampling (95% ethanol). All specimens were transferred to 75% ethanol after fieldwork and were deposited in the Herpetological Museum, Chengdu Institute of Biology (CIB),Chinese Academy of Sciences.

Morphological data

All measurements were carried out with slide calipers to the nearest 0.1 mm. Morphological characters and measurements of adults followed Fei et al. (2009a, 2009b) and Jiang et al.(2016), morphological characters and measurements of tadpoles followed Fei et al. (2009a) and McDiarmid & Altig(1999). Morphological characters and their abbreviations include: SVL, snout-vent length; HL, head length; HW, head width; SL, snout length; INS, internarial distance; IOS,interorbital distance; EHD, eye horizontal diameter; UEW,maximum width of upper eyelid; TD, tympanum diameter;FAHL, forelimb and hand length; LAW, width of lower arm;HAL, hand length; F3W, width of finger III disk; FML, femur(thigh) length; TBL, tibia (shank) length; TFL, length of tarsus and foot; FOL, foot length; T4W, width of disk of toe IV; TAL,tail length (for tadpoles); TOL, total length (for tadpoles); TH,tail height (for tadpoles).

Morphological data of congeners were obtained from voucher specimens (Supplementary Materials) and previously published literature (Annandale, 1912; Bain et al., 2006; Bain& Nguyen, 2004; Boulenger, 1920; Che et al., 2020; Fei et al.,2009b; Gan et al., 2020a, 2020b; Jiang et al., 2016; Stuart et al., 2010; Wang et al., 2020; Yu et al., 2019; Yuan et al.,2018).

Molecular data and analyses

For specimens sequenced in this study, genomic DNA was extracted from ethanol-preserved liver tissue samples using an Ezup Column Animal Genomic DNA Purification Kit(Sangon Biotech, China) following the protocols of the manufacturer. Two mitochondrial loci, 1 036 bp of 16S ribosomal RNA (16S) and 637 bp of cytochrome c oxidase subunit I (COI), were selected for phylogenetic reconstruction.The16SandCOIfragments were amplified using primer pairs: 16Sar-L (5'-GCCTGTTTATCAAAAACAT-3')/16Sbr-H(5'-CCGGTCTGAACTCAGATCACGT-3') (Yu et al., 2009) and Chmf4 (5'-TYTCWACWAAYCAYAAAGAYATCGG-3')/Chmr4(5'-ACYTCRGGRTGRCCRAARAATCA-3') (Che et al., 2012),respectively. Amplification of the16Sfragments was performed in a 25 μL volume reaction. Initial denaturation step: 3 min at 94 ℃ (COI: 5 min at 95 ℃), 40 cycles (COI: 35 cycles): denaturation 60 s at 94 ℃ (COI: 60 s at 95 ℃),annealing for 60 s at 51 ℃ (COI: 60 s at 46 ℃), extension for 1 min at 72 ℃; final extension: 10 min at 72 ℃. The polymerase chain reaction (PCR) products were purified and then sequenced in both forward and reverse directions using an ABI 3730xL sequencer (Applied Biosystems, USA) by Sangon Biotech Co., Ltd (China). All new sequences were deposited in GenBank under accession Nos. MZ702011−MZ702029 and MZ706954−MZ706971 (Table 1; Figure 1).

Table 1 lnformation on voucher numbers, GenBank accession Nos., and localities of samples used in this study

Continued

Amolops rickettiwas selected as the outgroup based on previous phylogenies (Wu et al., 2020; Zeng et al., 2020).Additional sequences ofAmolopsspecies and outgroup taxa were obtained from GenBank. The DNA sequences were aligned and manually adjusted using MEGA 6.0 (Tamura et al., 2013) with default parameters. Maximum-likelihood (ML)and Bayesian inference (BI) analyses were used for the 1 673 bp concatenated16S+COIdataset. The ML analyses were conducted using RAxML v8.2.10 (Stamatakis, 2014) and bootstrap proportions (BSP) were calculated with 1 000 nonparametric bootstrap replicates. The BI analyses were performed in MrBayes v.3.2.6 (Ronquist & Huelsenbeck,2003) with the GTR+G model, as determined using Akaike Information Criterion (AIC) in PartitionFinder v2 (Lanfear et al.,2017). The dataset was run for 10 000 000 generations and Markov chains were sampled every 100 generations. After convergence among runs was verified by examining the likelihood plots using Tracer v1.6 (Rambaut et al., 2013) and effective sample sizes (ESSs) were confirmed to exceed 200,the first 25% of trees were discarded as burn-in. Tree topology confidence was evaluated by Bayesian posterior probability(BPP).

Bioacoustic analysis

Advertisement calls ofA. chunganensisfrom Longsheng,Guangxi, China, were recorded in the field using a SONY PCM D100 digital sound recorder on 24 May 2010.Advertisement calls of the new species from Mt. Qingcheng,Chengdu, Sichuan, China, were recorded in the lab using a SONY PCM ICD-PX470 digital sound recorder on 30 May 2021. The sound files in wave format were sampled at 44.1 kHz with a depth of 24 bits. Praat v6.0.27 (Boersma,2001) was used to obtain the oscillogram, sonogram, and power spectrum (window length=0.015 s).

Figure 1 Sampling localities of species from A. monticola group used in this study (colored circles)

Abbreviations:CIB, Herpetological Museum of Herpetology, Chengdu Institute of Biology, Chinese Academy of Sciences; KIZ, Kunming Institute of Zoology, Chinese Academy of Sciences; LAB, Dr. Jia-Tang Li’s lab collections in CIB; AMNH, American Museum of Natural History; CAS,California Academy of Science; FMNH, Field Museum of Natural History; GXNU, Guangxi Normal University; KU,University of Kansas Museum of Natural History; KUHE,Graduate School of Human and Environmental Studies, Kyoto University; SCUM, Zoological Museum, Sichuan University;SYNU, Shenyang Normal University; SYS, Museum of Biology, Sun Yat-sen University; ZISP, Zoological Institute,R ussian Academy of Sciences.

RESULTS

Phylogenetic analyses

The ML and BI analyses yielded highly similar topologies and strong support for the monophyly of the ingroup (Clade A;BSP=100/BPP=1.00), largely coinciding with theA. monticolagroup, except forA. chayuensis(Figure 2). BI analysis strongly supported three highly divergentA. chunganensis sensu lato(Clade B) lineages (BPP=0.99), but ML bootstrap support was low (BSP=48). Specimens from the type locality ofA. chunganensis(Mt. Wuyi, located at the Fujian and Jiangxi border; ID: 8-11) as well as other localities from Zhejiang, Guangdong, Guangxi, Hunan, Hubei, Chongqing,and Sichuan (ID: 12-27) were recovered as a strongly supported monophyletic group (Clade C;BSP=100/BPP=1.00), identified asA.chunganensis sensu stricto. Clade D, which incorporated specimens from Guizhou,Gansu, and Sichuan (ID: 1-6, 62-65; 1BSP=100/BPP=1.00),was weakly clustered with Clade C (A.chunganensissensu stricto) (BSP=54/BPP=0.57), which represented a new species (Amolops chaochinsp. nov.), as described herein.Additionally, the specimen from Fangxian (Hubei) was identified as sister taxon to Clade C+Clade D with weak support (clade B; BSP=48/BPP=0.99) and was identified asA.cf.chunganensis(ID: 7).

Morphological comparisons

In theAmolops monticolagroup, our newly collected specimens from Chengdu (Sichuan) were most similar to the specimens ofA.chunganensis sensu strictofrom Mt. Wuyi,e.g., body size moderate, dorsal side brown, circummarginal groove on all fingers, tibiotarsal articulation beyond snout,transverse bands on dorsal limbs, and external vocal sacs present. However, the specimens differed fromA.chunganensisby white tubercles on dorsal side of posterior body, distinct tubercles on dorsal thigh, white spinose tubercles on dorsal tibia, white tubercles on temporal region,toe webbing not reaching disk on inner side of toe II, and outer metatarsal tubercle small but distinct (Figure 3).

Bioacoustics

The calls of the two species differed significantly in spectral and temporal characteristics, especially in call repertoire. The calling behavior of the new species (Figure 4G−I) is more complex than that ofA. chunganensis(Figure 4A−C). The male of the new species can produce extremely complex compound calls (Figure 4H, I).

Systematic accounts

Re-description of Amolops chunganensis (Pope, 1929)based on topotypic specimens(Figures 5, 6A)

RanachunganensisPope, 1929, Am. Mus. Novit., 352: 3.Type locality: Kuatun, northwestern Chungan Hsien(=Wuyishan City), Fukien (=Fujian) Province, China, 4 500-5 000 feet altitude. Holotype: AMNH 30 479, ♂, by original designation.

Staurois chunganensis: Liu, 1940, J. West China Border Res.Soc., 12 (B): 32; Liu, 1941, Peking Nat. Hist. Bull., 15(4): 291(in part).

Figure 2 Phylogeny of Amolops frogs represented by selected species and constructed using mitochondrial sequences from 16S and COl fragments

Figure 3 Comparisons of morphological characteristics between male holotype (ClB 116971) of Amolops chaochin sp. nov. (left,A1, B1, C1) and male topotype (SYS a008411) of A. chunganensis(right, A2, B2, C2)

Amolops chunganensis: Inger, 1966, Fieldiana, Zool., 52: 256,by implication; Fei, Hu, Ye & Huang, 2009, Fauna Sinica,Amph. 3: 1514.

Referred specimens:Five male specimens, including one male (CIB 33536) from Miaowan, Mt. Wuyi, Wuyishan City,Fujian; four males (CIB 116985−88) from Huanggang(N27.813344°, E117.719879°, at 1 100 m a.s.l.), Mt. Wuyi,Yanshan County, Jiangxi; and one female specimen (CIB 118077) from Guwangkeng (N27.701737°, E117.688498°, at 941 m a.s.l.), Mt. Wuyi, Wuyishan City, Fujian.

Remark:Mt. Wuyi is located on the border between southeastern Jiangxi and northwestern Fujian. Due to the close geographical distance between Kuatun, Miaowan,Guwangkeng, and Huanggang, the specimens from Miaowan,Guwangkeng, and Huanggang can be regarded as topotypic specimens ofA. chunganensis.

Diagnosis:(1) skin smooth; (2) lateral side of head dark, with light-colored upper lip stripe extending to shoulder; (3) distinct dorsolateral folds; (4) moderate body size, SVL 37.2−41.5 mm in males (n=5), SVL 52.6 mm in female (n=1); (5) tympanum distinct, slightly larger than half of eye diameter; (6) small tooth-like projection on anteromedial edge of mandible; (7)circummarginal groove on all fingers; (8) white tubercles on dorsal side of posterior body absent; (9) distinct tubercles on dorsal thigh and white spinose tubercles on dorsal tibia absent; (10) white tubercles on temporal region absent; (11)toe webbing reaching disk on inner side of toe II; (12)vomerine teeth present; (13) transverse bands on dorsal limbs; (14) external vocal sacs present in males.

Figure 4 Amplitude-modulated waveforms (1) and spectrograms (2) of three call types in A. chunganensis (A-C) and Amolops chaochin sp. nov. (D-l)

Description:Moderate body size, SVL 37.2−41.5 mm in males, SVL 52.6 mm in female (other known female specimen was recorded to 58.0 mm by Pope (1929)), slightly compressed on vertical direction. Head slightly longer than wide (HL/HW ratio 1.10 in males, 1.02 in female); snout projecting forward, rounded at tip; nostril lateral, slightly closer to eye than tip of snout; canthus rostralis distinct; loreal region concave and oblique; eye relatively large (EHD/HL ratio 0.34 in males, 0.35 in female); interorbital distance larger than width of upper eyelid; tympanum distinct, tympanum diameter slightly larger than half eye diameter (TD/EHD ratio 0.54 in males, 0.59 in female), tympanic rim elevated; vomerine teeth present; tongue pyriform, deeply notched posteriorly; vocal sac openings present.

Figure 5 Adult male specimen (ClB 116985) of A. chunganensis sensu stricto from Mt. Wuyi, Jiangxi, in life

Figure 6 Adult male specimen of A. chunganensis sensu stricto(ClB 116988) (A) from Mt. Wuyi, Jiangxi, and adult male holotype of Amolops chaochin sp. nov. (ClB 116971) (B) in preservative

Forearm robust. Tips of all four fingers expanded into small discs, finger III disc much smaller than diameter of tympanum;circummarginal grooves present on tips of all fingers, but indistinct on first finger; relative finger length I

Hindlimb slender, tibiotarsal articulation beyond snout, heels overlapped when hindlimbs flexed and held perpendicular to body. Tips of all five toes expanded into small discs, width of toe IV disc slightly smaller than finger III disc; relative toe length I

Dorsal surface relatively smooth, without any distinct warts on dorsal head, body, or limbs; lateral surface smooth, except very small white warts below dorsolateral folds, especially near crotch; supratympanic fold indistinct, temporal region without any tubercles; dorsolateral fold distinct, from rear of upper eyelid to near vent; ventral surfaces smooth except flat tubercles on ventral surface of basal thigh; one low rictal gland, continuous with upper lip.

Coloration of holotype in life:Dorsal side pale brown, with dark brown spots on dorsal head and body; irregular transverse dark brown bands on forelimbs, distinct transverse dark brown bands on hindlimbs. Lateral head black, upper lip white, with black line below; lateral body above half grayish brown, below half pale brown, with indistinct yellow pigmentation on crotch, without distinct spots. Ventral head and body white, throat and chest with brownish black spots,sides of belly with brownish black spots or not; ventral side of limbs brownish yellow. Upper one fourth of iris golden with small brown spots, lower part red brown.

Coloration of holotype in preservative:Dorsal color pale brownish gray, spots or bands black; lateral side, yellow pigmentation changed to white; ventral color cream white,spots pale gray.

Secondary sexual characters:Males with pair of developed external subgular vocal sacs; inner side of first finger with developed, velvety nuptial pad; forearm strong.

Variation:Measurements of referred specimens are summarized in Table 2. Specimens show some differences in coloration on ventral side (in preservative), two male specimens (CIB 116 986−87) without spots on sides of belly.

Distribution and habitat:Amolops chunganensisis currently known from Fujian, Jiangxi, Chongqing, Guangdong, Guangxi,Guizhou (Leishan), Hubei (Shennongjia), Hunan, Sichuan (Mt.Daba), and Zhejiang, China (Fei et al., 2009b; Yang, 1991;this study).

TheA. chunganensispopulation inhabits mountain streams at 950 to 1 150 m a.s.l. in Huanggang, Mt. Wuyi, China. The streams are ~10 m wide and surrounded by moist subtropical evergreen broadleaved forests. Males were observed calling actively on leaves or twigs of bushes at the bank of streams from dusk to midnight during our investigation in early July 2020. Nevertheless, we did not find any individuals of this population during our investigation of the same locality in late July 2019. Thus, the breeding season of this Huanggang population may end before mid-July.

Table 2 Measurements of five adult male specimens and one adult female specimen of A. chunganensis sensu stricto from Mt. Wuyi(in mm)

In the same microhabitat from Huanggang, Mt. Wuyi,A.wuyiensis(Liu & Hu, 1975),Odorrana huanggangensisChen,Zhou & Zheng, 2010,Quasipaa spinosa(David, 1875), andTrimeresurus stejnegeriSchmidt, 1925 were commonly observed during the survey period in 2020. For further details on the life history of the type locality population see Pope(1931)

Amolops chaochinsp. nov. Jiang, Ren, Lyu, and Li(Figures 6B, 7)

Staurois chunganensisLiu, 1940, J. West China Border Res.Soc., 12 (B): 32-35; Liu, 1941, Peking Nat. Hist. Bull., 15(4):291-295.

Amolops chunganensisFei et al. 2009, Fauna Sinica Amphibia, vol.3: 1514-1519.

Holotype:CIB 116971 (field no. LAB 2020130), adult male,collected from Jiguanshan (E103.351094°, N30.782583°, 1 179 m a.s.l.), Chongzhou City (county-level city), Chengdu City,Sichuan, China, on 20 June 2020 by Jin-Long Ren and Xin-Yu Li.

Allotype:CIB 116972 (field no. LAB 2020133), adult female,collected from Sanlang (E103.460097°, N30.826772°, 920 m a.s.l.), Chongzhou City (county-level city), Chengdu City,Sichuan, China, on 20 June 2020 by Jin-Long Ren and Xin-Yu Li.

Paratypes:CIB 116974, CIB 116978 (two males), collected from the same locality and date as holotype; CIB 116973, CIB 116975-77 (four males), CIB 116979-84 (six females),collected from the same locality and date as allotype.

Figure 7 General and close-up views of Amolops chaochin sp.nov. in life, showing color variation among individuals and features in amplexus

Referred specimens:CIB 118027 (vouchered bottle number,contains 12 tadpoles numbered CIB 118027−1 to 118027−12,including 10 tadpoles at stage 31, one at stage 30, and one at stage 28), collected from Qingyin’ge, Mt. Emei, Sichuan,China, on 3 October 2020 by K. Jiang.

Etymology:Specific epithet “chaochin” is named after Prof.Ch’eng-Chao Liu (1900-1976) and his wife Prof. Shu-Chin Hu(1914-1992), combining the last words of their given names“Chao” and “Chin”. Prof. Liu and Prof. Hu both greatly contributed to Chinese herpetology and established the Herpetological Museum at the Chengdu Institute of Biology,Chinese Academy of Sciences. During their fieldwork in Mt.Emei, Prof. Liu and Prof. Hu found the first pair of specimens of this new species. Furthermore, based on field observations from 1938 to 1940, Prof. Liu published the detailed life history of this new species under the name “Staurois chunganensis”(Liu 1941), and the specimens collected by Prof. Liu are still preserved in CIB (Figure 8A). We suggest the English common name as “Chaochin’s torrent frog” and the Chinese common name as “钊琴湍蛙 (in Chinese Pinyin: Zhāo Qín Tuān Wā)”.

Diagnosis:According to the morphological characters of theA. monticolagroup stated by Stuart et al. (2010),Amolops chaochinsp. nov. is placed in theA. monticolagroup based on the following diagnosis: (1) skin relatively smooth; (2)dorsolateral fold distinct; (3) lateral side of head black, upper lip stripe yellowish white extending to shoulder.

Figure 8 Paired specimens (A) (ClB 33471; field number: 川793)of Amolops chaochin sp. nov. collected by Prof. Cheng-Chao Liu from Mt. Emei, Sichuan, on 21 July 1940, photo by Ke Jiang, and tadpole (B) of Amolops chaochin sp. nov. from Mt. Emei, Sichuan,in preservative

Amolops chaochinsp. nov.is distinguished from all other congeners in theA. monticolagroup by the following combination of characters: (1) moderate body size, SVL 35.3−39.2 mm in males (n=7) and 50.5−54.4 mm in females(n=7); (2) tympanum distinct, larger than half of eye diameter;(3) small tooth-like projection on anteromedial edge of mandible; (4) circummarginal groove on all fingers; (5) white tubercles on dorsal side of posterior body in both sexes; (6)distinct tubercles on dorsal thigh and white spinose tubercles on dorsal tibia in both sexes; (7) white tubercles on posterior region of tympanum in males; (8) toe webbing reaching disk by dermal fringe on inner side of toe II; (9) vomerine teeth present; (10) transverse bands on dorsal limbs; (11) external vocal sacs present in males.

Description of holotype.Moderate body size, SVL 37.3 mm,slightly compressed in vertical direction. Head slightly longer than wide (HL/HW 1.03); snout projecting forward, rounded at tip; nostril lateral, slightly closer to eye than tip of snout;canthus rostralis distinct; loreal region concave and oblique;eye relatively large (EHD/HL ratio 0.35); interorbital distance larger than width of upper eyelid; tympanum distinct,tympanum diameter about two thirds of eye diameter (TD/EHD ratio 0.63), tympanic rim elevated; vomerine teeth present;tongue pyriform, deeply notched posteriorly; vocal sac openings present.

Forearm robust. Tips of all four fingers expanded into small discs, finger III disc much smaller than diameter of tympanum;circummarginal grooves present on tips of all fingers, but indistinct on first finger; relative finger length I

Hindlimb slender, tibiotarsal articulation beyond snout, heels overlapped when hindlimbs flexed and held perpendicular to body. Tips of all five toes expanded into small discs, width of toe IV disc slightly smaller than finger III disc; relative toe length I

Dorsal surface relatively smooth, small warts present on dorsal head and body, white tubercles present on dorsal side of posterior body, distinct tubercles on dorsal thigh and white spinose tubercles on dorsal tibia; lateral surface smooth, very small white warts below dorsolateral folds, especially near crotch; supratympanic fold indistinct, temporal region with small white tubercles; dorsolateral fold distinct, from rear of upper eyelid to near vent; ventral surfaces smooth except flat tubercles on ventral surface of basal thigh; one low rictal gland, continuous with upper lip.

Coloration of holotype in life:Dorsal side brown, with black spots on dorsal head and body; irregular transverse black bands on forelimbs, distinct transverse black bands on hindlimbs. Lateral head black, upper lip white, with black line below; lateral body gray with large black spots, and yellow pigmentation on crotch. Ventral head and body yellowish white, throat and chest with dark gray spots; ventral side of limbs yellow. Upper one fourth of iris golden with small brown spots, lower part red brown.

Coloration of holotype in preservative:Dorsal color brownish gray, spots or bands grayish black; lateral side,yellow pigmentation changed to white; ventral color cream white, spots pale gray.

Sexual dimorphism:Males with pair of developed external subgular vocal sacs; inner side of first finger with developed,velvety nuptial pad; forearm of males stronger than females,and snout-vent length of males smaller than females; white tubercles on dorsal side of posterior body, tubercles on dorsal thigh and white spinose tubercles on dorsal tibia of males more distinct than that of females.

Variation:Measurements of type series and referred specimens are summarized in Tables 3, 4. Specimens show some differences in coloration on ventral side (in preservative). Two male specimens (CIB 116973 and CIB 116977) and three female specimens (CIB 116981-82,CIB116984) with dark gray spots on throat and chest, other five male specimens (CIB 116971, CIB 116974-76, CIB 116978) and three female specimens (CIB 116979-80, CIB 116983) with pale gray spots on throat and chest.

Tadpoles in preservative(based on 10 tadpoles at stage 31): SVL 12.4−14.2 mm (mean 13.2 mm), TAL 21.4−25.3 mm(mean 23.7 mm), TOL 33.9−39.2 mm (mean 36.9 mm) (Table 5; Figure 8B). Body vertically flattened; eyes on dorsal head;pair of rounded yellow glands behind gills, same size as eyes;spiraculum on left side, spiracular tube present; large “U”shaped sucker behind mouth on ventral side; pair of rounded yellow glands at base of hindlimb buds, smaller than eyes;medial vent tube small, opening at end; tail horizontally flattened, tail length about 1.8 times body length, tail muscle developed, tail tip blunt. Single row of regular papillae on each side of lateral mouth, single row of regular papillae on edge of lower lip; keratodont formula III: 4+4/1+1: II, some specimens III: 3+3/1+1: II in Fei et al. (2009b). Dorsal and lateral sides brownish gray, caudal fins with small dark gray spots and tiny lines; ventral side grayish white.

Distribution and habitat:Amolops chaochinsp. nov. is known from mountainous regions at the edge of the Sichuan Basin, including Chengdu City (Chongzhou, Dayi, and Dujiangyan), Leshan City (Mt. Emei), Mianyan City (Anxian)and Ya’an City (Tianquan) (Liu, 1941), Sichuan. Based on molecular data, it is also distributed in Bijie (Guizhou) and Wenxian (Gansu).

The new species seems to be both diurnal and nocturnal.During our field investigations in May 2019 and June 2020 at Chengdu, both males and females were rather active across daytime and nighttime, especially on rainy days. Males were found energetically calling on leaves or twigs of bushes, rocks,and even on roads adjacent to the banks of the mountain streams (Figure 9). All females were found paired with males,and the mating pairs were mostly found floating with the stream currents. Local population density appears quite large,with Liu (1941) collecting 123 males and 87 females from Mt.Emei, Sichuan, on 20 July 1940. Although we found no eggs in the field, Liu (1941, 1950) recorded egg masses attached to the under surface of stones in deep water, with a clutch size of 417-448. For further details on life history, see Liu (1941,1950).

Table 3 Measurements of seven adult male specimens (type series) of Amolops chaochin sp. nov. (in mm)

Table 4 Measurements of seven adult female specimens (type series) of Amolops chaochin sp. nov. (in mm)

Table 5 Measurements of 10 tadpoles (at stage 31) of Amolops chaochin sp. nov. (in mm)

In the same microhabitat in Chengdu,Bufo gargarizans(Cantor, 1842),A. mantzorum(David, 1871),Odorranacf.margaretae(Liu, 1950),Zhangixalus omeimontis(Stejneger,1924), andHebius metusia(Inger, Zhao, Shaffer & Wu, 1990)were commonly observed during the survey period in 2019.

Comparison:Amolops chaochinsp. nov.differs from all other species, except theA. monticolaspecies group, by smooth skin, lateral side of head dark, with light-colored upper lip stripe extending to shoulder, and distinct dorsolateral folds.In theA. monticolaspecies group,Amolops chaochinsp. nov.differs fromA. bellulus,A. compotrix,A. cucae,A.nyingchiensis,A. deng,A. putaoensis, andA. akhaorumbased on the following characters: pair of external subgular vocal sacs present (vs. absent inA. bellulus,A. deng, andA.nyingchiensis; internal vocal sacs present inA. akhaorum,A.compotrix,A. cucae, andA. putaoensis).Amolops chaochinsp. nov.differs fromA. archotaphusby presence of circummarginal groove on all fingers (vs. circummarginal

Figure 9 Habitat of Amolops chaochin sp. nov. at 1 179 m a.s.l.on Jiguanshan, Chongzhou, Chengdu, Sichuan, China

Type series were found across rocky, flowing streams (A) and adjacent pools (B, mating pairin situon stones), ditches, and shrubs.Photos by Jin-Long Ren.groove absent at first finger); differs fromA. chakrataensisby tibiotarsal articulation beyond snout (vs. tibiotarsal articulation not reaching snout); differs fromA. daorum,A. iriodes,A.mengdingensis,A. vitreus, andA. wenshanensisby dorsal side brown (vs. dorsal side green); differs fromA.mengyangensisby smaller body size (SVL 35.3−39.2 mm in males and 50.5−54.4 mm in females vs. SVL 39.0−40.0 mm in males and 60.0 mm in females) and tubercles and warts on dorsal surface present (vs. absent); differs fromA.tuanjieensisby tympanum diameter greater than half of eye diameter (vs. tympanum diameter less than half of eye diameter); differs fromA. monticolaby smaller body size (SVL 35.3−39.2 mm in males and 50.5−54.4 mm in females vs. SVL 41.0 in male and 65.0 in female) and larger tympanum (TD/ED 0.60−0.65 vs. 0.33−0.50); differs fromA. aniqiaoensisby smaller body size (SVL 35.3−39.2 mm in males and 50.5−54.4 mm in females vs. SVL 51.6 mm in males and 69.5−71.7 mm in females) and “/ ” shaped pattern on throat absent (vs.present); differs fromA. kohimaensisby smaller body size(SVL 35.3−39.2 mm in males vs. SVL 42.8-48.6 mm in males)and patch covered by microgranules on chest absent (vs.present).

Amolops chaochinsp. nov.is most similar toA.chunganensisbut differs by presence of white tubercles on dorsal side of posterior body, distinct tubercles on dorsal thigh,white spinose tubercles on dorsal tibia, white tubercles on temporal region, toe webbing not reaching disk but reaching disk by dermal fringe on inner side of toe II, outer metatarsal tubercle small but distinct (vs. absence of above tubercles, toe webbing reaching disk of inner side of toe II, and outer metatarsal tubercle small and indistinct).

DlSCUSSlON

Cryptic diversity in Amolops chunganensis complex

Amolops chunganensisis widely reported from Fujian, Jiangxi,Chongqing, Gansu, Guangdong, Guangxi, Guizhou, Hubei,Hunan, Shaanxi, Sichuan, Yunnan, and Zhejiang, China(AmphibiaChina, 2021; Fei et al., 2009b, 2012; Frost, 2021).Both Wu et al. (2020) and this study suggest thatA.chunganensismay contain three clades with relatively high levels of intraspecific divergence. According to molecular and morphological data, the records ofA. chunganensisfrom the northern, western, and southern edges of the Sichuan Basin(including Chengdu, Emei, and Mianyang in Sichuan; Wenxian in Gansu; Bijie in Guizhou; Figure 1, red circle) should be revised toAmolops chaochinsp. nov., but the records from the northeastern edge of the Sichuan Basin (including Nanjiang in Sichuan; and Chongqing City; Figure 1, blue circle) should remain asA. chunganensis.In addition, the historic records ofA. chunganensisin eastern and southern China (Fujian, Jiangxi, Guangdong, Guangxi, Hunan, and Zhejiang; Figure 1, blue circle) are correctly identified.However, another clade previously identified as "A.chunganensis" should be further discussed. Although the single sample collected from Fangxian, northwestern Hubei(Figure 1, green circle) is geographically close to the localities ofA. chunganensis sensu strictofrom western Hubei and northern Chongqing, it formed a sister taxon to theA.chunganensis+Amolops chaochinsp. nov. clade based on phylogeny (Figure 2; BSP=48/BPP=0.99). Consequently, the northwestern Hubei population likely represents a cryptic species, and further study is needed.

Problematic records of Amolops chunganensis in Yunnan, China

Amolops chunganensisis also recorded from Yunnan (Fei et al., 2009b; Yang, 1991; Yang & Rao, 2008). However, our results indicate thatA. chunganensissensu strictois not distributed in this region and these problematic records should be clarified.

Amolops mengyangensisis described from Mengyang,Jinghong City, Xishuangbanna Prefecture, southern Yunnan(Wu & Tian, 1995), but was synonymized withA.chunganensisby Yang & Rao (2008) and Fei et al. (2009b), it is the reason why remained the record ofA. chunganensisin this region. Although molecular data ofA. mengyangensisfrom the type locality are not available, molecular samples from Vietnam do not cluster withA. chunganensisfrom the type locality (Mt. Wuyi) or other localities (Stuart et al., 2010;Wu et al., 2020; this study), andA. mengyangensismorphologically differs fromA. chunganensisby its smaller tympanum (tympanum diameter less than half eye diameter vs. tympanum diameter larger than eye diameter). As the validity ofA. mengyangensisis widely accepted (Frost, 2021;Nguyen et al., 2009; Ohler, 2007; Stuart et al., 2010), theA.chunganensisrecord from Xishuangbanna (Jinghong),southern Yunnan (Fei et al., 2009b; Yang & Rao, 2008) should be revised to its original identification, i.e.,A. mengyangensis.

Yang (1991) also reportedA. chunganensisfrom Menglian County, southwestern Yunnan. We re-examined the Menglian specimens (information given in the Supplementary Materials)used in Yang (1991), and their morphological characters are consistent with the original description ofA. tuanjieensis(Gan et al., 2020b), especially in regard to living coloration, i.e.,“dorsal side brown-red with irregular gray and black spots,upper part of flanks green with dark blotches, lower part white with large dark blotches”, which is distinguished fromA.chunganensisand other species of theA. monticolagroup in Yunnan. Therefore, the record ofA. chunganensisfrom Menglian, Yunnan, should be provisionally revised toA.tuanjieensis, with further molecular confirmation required.

Revision on Amolops species groups

Group re-assignment of A. gerbillus:Amolops gerbilluswas placed in theA. monticolagroup by Fei et al. (2005). Although this placement was doubted by Stuart et al. (2010), it has been retained in most studies (Gan et al., 2020a, 2020b; Jiang et al., 2016; Yu et al., 2019; Yuan et al., 2018). According to the original description (Annandale, 1912),A. gerbillushas “a distinct glandular laterodorsal fold”. Combined with the figure(Annandale, 1912: plate II, Figure 1), the “glandular laterodorsal fold” is distinguished from the true dorsolateral folds of other species in theA. monticolagroup, but is consistent with species in theA. marmoratusgroup, e.g.,“raised tubercles…along dorsolateral row but distinct dorsolateral fold absent (A. marmoratus(Blyth, 1855); Dever et al., 2012)”, “dorsolateral glands forming incomplete series on each side of dorsum (A. nepalicusYang, 1991; Wang et al., 2020)”, and “dorsolateral fold very weakly developed with warty granules (A. mahabharatensisKhatiwada, Shu, Wang,Zhao, Xie & Jiang, 2020; Khatiwada et al., 2020)”. On the other hand,A. gerbillusalso has “large compressed longitudinal tubercles’’ on the dorsum and lacks a dark lateral head with a light-colored upper lip stripe extending to the shoulder (Annandale, 1912), in contrast with species in theA.monticolagroup (i.e., smooth skin, lateral side of head dark,with light-colored upper lip stripe extending to shoulder) but consistent with species in theA. marmoratusgroup (Dever et al., 2012; Khatiwada et al., 2020; Wang et al., 2020).Furthermore, Wang et al. (2020) suggested thatA. gerbillusmay be conspecific withIxalus argusAnnandale, 1912, a nomenclature synonymized withA. marmoratusin theA.marmoratusgroup. Therefore, we propose thatA. gerbillusbe moved from theA. monticolagroup to theA. marmoratusgroup, with further vouchers required for confirmation.

Establishment of A. chayuensis group and A.spinapectoralis group:Amolops chayuensiswas placed into theA. monticolagroup by Sun et al. (2013) based on the presence of dorsolateral folds only, but it did not cluster phylogenetically with other species in theA. monticolagroup based on mitochondrial sequencing data (Che et al., 2020;Gan et al., 2020a, 2020b; Jiang et al., 2016; Lyu et al., 2019b;Zeng et al., 2020). Zeng et al. (2020) proposed that a new species group is needed for this species but did not provide relevant taxonomic analysis or morphological diagnosis.Conversely, Wu et al. (2020) suggested to retainA.chayuensisinside theA. monticolagroup as the most basal lineage using anchored hybrid enrichment data.

Morphologically, althoughA. chayuensishas true dorsolateral folds and smooth skin, but it lacks lateral side of head dark, with a light-colored upper lip-stripe extending to the shoulder (forA. chayuensis, lateral head process the same color as dorsal side and lacking light-colored upper lip-stripe;from Che et al., 2020; Sun et al., 2013; this study), which is a diagnostic character of theA. monticolagroup.Phylogenetically,A. chayuensiswas consistently recovered as a distinct monophyletic clade, thus the distinctiveness ofA.chayuensisshould be recognized (Figure 2). Therefore, we support Zeng et al. (2020) and suggest thatA. chayuensisbe removed from theA. monticolagroup to form an independentA. chayuensisspecies group.

The Vietnamese speciesA. spinapectoralisInger, Orlov &Darevsky, 1999 is phylogenetically recognized as sister to theA. hainanensis,A. daiyunensisandA. rickettigroups clade but cannot be placed into any recognized species group (Wu et al., 2020). Morphologically,A. spinapectoraliscan be distinguished from theA. hainanensis,A. daiyunensisandA.rickettigroups, as well as other known species groups, based on the following characters: disc of first finger distinctly larger than disc of second finger, nuptial pad in males containing whitish conical spines, and chest of males with oval area of similar spines. Therefore, we suggest the establishment of a new species group, i.e.,A. spinapectoralisgroup, to contain this single species.

Revised memberships and diagnoses for Amolops species groups:Wu et al. (2020) proposed a new species group, i.e.,A. viridimaculatusgroup, which containedA.viridimaculatus,A. medogensis, and four undescribed species(three were described in Che et al., 2020). Before the new group was proposed,A. viridimaculatusandA. medogensiswere placed in theA. mantzorumgroup andA. marmoratusgroup, respectively (Fei et al., 2009b; Lyu et al., 2019b).Furthermore, three new species (A. beibengensisJiang, Li,Zou, Yan & Che, 2020,A. gyirongensisJiang, Wang, Wang,Pan & Che, 2020, andA. wangyufaniJiang, 2020) clustered with species in theA. viridimaculatusgroup were described in Che et al. (2020). However, diagnostic revisions of theA.mantzorum,A. marmoratus, andA. viridimaculatusgroups are needed. Together with re-assigningA. gerbillusand the establishment of theA. chayuensisandA. spinapectoralisgroups, we present an overall revision of all species groups as follows:

I. Diagnosis and content of revisedA. monticolagroup

Diagnosis: (1) true dorsolateral folds present (not formed by incomplete series of glands); (2) skin smooth; (3) lateral side of head dark, with light-colored upper lip stripe extending to shoulder.

Content (21 species):A. aniqiaoensis,A. akhaorum,A.archotaphus,A. bellulus,A. chakrataensis,A. chaochinsp.nov.,A. chunganensis,A. compotrix,A. cucae,A. daorum,A.deng,A. kohimaensis,A. iriodes,A. mengdingensis,A.mengyangensis,A. monticola,A. nyingchiensis,A.putaoensis,A. tuanjieensis,A. vitreus, andA. wenshanensis.

Remarks: Placements are supported by both molecular and morphological data (Che et al., 2020; Gan et al., 2020a,2020b; Liu et al., 2000; Ray, 1992; Zeng et al., 2020; this study), except forA. kohimaensis(Biju et al., 2010) andA.monticola(Anderson, 1871; Boulenger, 1920), which are supported by morphological data only.

II. Diagnosis and content of newly proposedA. chayuensisgroup

Diagnosis: (1) true dorsolateral folds present (not formed by incomplete series of glands); (2) skin smooth; (3) lateral side of head same color as dorsal side, light-colored upper lip stripe extending to shoulder absent.

Content (one species):A. chayuensis.

Remarks: Placement is supported by both molecular and morphological data (Che et al., 2020; Sun et al., 2013; Zeng et al., 2020; this study).

III. Diagnosis and content of revisedA. mantzorumgroup

Diagnosis: (1) moderate or small body size, usually SVL<65 mm in males; (2) true dorsolateral folds absent, but welldeveloped glands present in incomplete series along dorsolateral junction of body on each side in several species;(3) vomerine teeth present, except forA. loloensisandA.ottorum; (4) circummarginal groove on disc of finger I absent;(5) tarsal fold and tarsal glands absent; (6) vocal sac present or absent in males; (7) nuptial pad present on first finger in males.

Content (10 species):A. granulosus(Liu & Hu, 1961),A.mantzorum,A. jinjiangensisSu, Yang & Li, 1986,A. lifanensis(Liu, 1945),A. loloensis(Liu, 1950),A. minutusOrlov & Ho,2007,A. ottorumPham, Sung, Pham, Le, Ziegler & Nguyen,2019,A. shuichengicusLyu & Wang, 2019,A.tuberodepressusLiu & Yang, 2000, andA. xinduqiaoFei, Ye,Wang & Jiang, 2017.

Remarks: Placements are supported by both molecular and morphological data (Lyu et al., 2019b; Pham et al., 2019; Wu et al., 2020; Zeng et al., 2020), except forA. minutus(Orlov &Ho, 2007), which is supported by morphological data only.

IV. Diagnosis and content of revisedA. marmoratusgroup

Diagnosis: (1) true dorsolateral folds absent, but welldeveloped glands present in incomplete series along dorsolateral junction of body on each side in individuals of several species; (2) vomerine teeth present; (3)circummarginal groove on disc of finger I present; (4) tarsal fold and tarsal glands absent; (5) vocal sac present in males;(6) nuptial pad present on first finger in males.

Content (10 species):A. afghanus(Günther, 1858),A.assamensisSengupta, Hussain, Choudhury, Gogoi, Ahmed &Choudhury, 2008,A. gerbillus,A. indoburmanensisDever,Fuiten, Konu & Wilkinson, 2012,A. jaunsariRay, 1992,A.mahabharatensis,A. marmoratus,A. nepalicus,A. panhaiMatsui & Nabhitabhata, 2006, andA. yarlungzangboJiang,Wang, Li, Qi, Li & Che, 2020.

Remarks: Placements are supported by both molecular and morphological data (Che et al., 2020; Khatiwada et al., 2020;Wang et al., 2020; Wu et al., 2020), except forA. assamensis(Sengupta et al., 2008), which is supported by morphological data only. Furthermore,A. jaunsariis suggested to be closely related toA. afghanus(Dutta, 1997).

V. Diagnosis and content of revisedA. viridimaculatusgroup

Diagnosis: (1) large body size, usually SVL>70 mm in males, except forA. gyirongensisandA. wangyufani; (2)dorsolateral folds absent; (3) vomerine teeth distinct; (4)circummarginal groove on disc of finger I present or absent;(5) tarsal fold and tarsal glands absent; (6) vocal sac absent in males; (7) nuptial pad present on first finger in males.

Content (13 species):A. beibengensis(asAmolopssp. 2 in Wu et al., 2020),A. caelumnoctisRao & Wilkinson, 2007,A formosus(Günther, 1875),A. gyirongensis(asAmolopssp. 4 in Wu et al., 2020),A. himalayanus(Boulenger, 1888),A.kaulbacki(Smith, 1940),A. longimanus(Andersson, 1938),A.medogensisLi & Rao, 2005,A. nidorbellusBiju, Mahony &Kamei, 2010,A. pallasitatusQi, Zhou, Lyu, Lu & Li, 2019,A.splendissimusOrlov & Ho, 2007,A. viridimaculatus(Jiang,1983), andA. wangyufani(asAmolopssp. 3 in Wu et al.,2020).

Remarks: Placements are supported by both molecular and morphological data (Che et al., 2020; Qi et al., 2019; Wu et al.,2020; Zeng et al. 2020), except forA. caelumnoctis(Rao &Wilkinson, 2007),A. formosus(Günther, 1875; Boulenger,1920),A. himalayanus(Boulenger, 1888; Nidup et al., 2016),A. kaulbacki(Smith, 1940),A. longimanus(Andersson, 1938;Dubois, 1986),A. nidorbellus(Biju et al., 2010), andA.splendissimus(Orlov & Ho, 2007), which are supported by morphological data only.

VI. Diagnosis and content of newly proposedA.spinapectoralisgroup

Diagnosis: (1) dorsolateral folds absent; (2) vomerine teeth present; (3) circummarginal groove on disc of finger I present;(4) disc of first finger distinctly larger than that of second finger; (5) vocal sac present in males; (6) nuptial pad with whitish conical spines present on first finger in males; (7)chest with oval area of similar spines in males.

Content (one species):A. spinapectoralis.

Remarks: Placement is supported by both molecular and morphological data (Inger et al., 1999; Wu et al., 2020).

VII. Diagnosis and content ofA.larutensisgroup

Diagnosis: (1) dorsolateral folds absent; (2) tympanum distinct; (3) vomerine teeth present; (4) circummarginal groove on disc of finger I present; (5) tarsal fold or tarsal glands present; (6) vocal sac present in males; (7) nuptial pad present on first finger in males.

Content (four species):A. australisChan, Abraham,Grismer & Grismer, 2018,A. cremnobatusInger & Kottelat,1998,A. gerutuChan, Abraham, Grismer & Grismer, 2018,andA. larutensis(Boulenger, 1899).

Remarks: Placements are supported by both molecular and morphological data (Inger & Kottelat, 1998; Chan et al., 2018;Wu et al., 2020).

VIII. Diagnosis and content ofA. rickettigroup

Diagnosis: (1) dorsolateral folds absent; (2) vomerine teeth present or absent; (3) circummarginal groove on disc of finger I present; (4) disc of first finger distinctly smaller than that of second finger; (5) tarsal fold and tarsal glands absent; (6)vocal sac present or absent in males; (7) nuptial pad with conical or papillate spines present on first finger in males.

Content (six species):A. albispinusSung, Wang & Wang,2016,A. ricketti(Boulenger, 1899),A. sinensisLyu, Wang &Wang, 2019,A.wuyiensis,A. yatseniLyu, Wang & Wang,2019, andA. yunkaiensisLyu, Wang, Liu, Zeng & Wang,2018.

Remarks: Placements are supported by both molecular and morphological data (Lyu et al., 2019a; Wu et al., 2020; Zeng et al., 2020).

IX. Diagnosis and content ofA. daiyunensisgroup

Diagnosis: (1) dorsolateral folds absent; (2) tympanum distinct or hidden; (3) vomerine teeth absent; (4)circummarginal groove on disc of finger I present; (5) tarsal glands present; (6) vocal sac present in males; (7) nuptial pad present on first finger in males.

Content (two species):A. daiyunensis(Liu & Hu, 1975) andA. hongkongensis(Pope & Romer, 1951).

Remarks: Placements are supported by both molecular and morphological data (Fei et al., 2009b; Wu et al., 2020; Zeng et al., 2020).

X. Diagnosis and content ofA. hainanensisgroup

Diagnosis: (1) dorsolateral folds absent; (2) tympanum distinct; (3) vomerine teeth absent; (4) circummarginal groove on disc of finger I present; (5) tarsal fold or tarsal glands present; (6) vocal sac present or absent in males; (7) nuptial pad absent in males.

Content (two species):A. hainanensis(Boulenger, 1900)andA. torrentis(Smith, 1923).

Remarks: Placements are supported by both molecular and morphological data (Fei et al., 2009b; Wu et al., 2020; Zeng et al., 2020).

Key to Amolops species group

1a)True dorsolateral folds present ......................................... 2

1b)True dorsolateral folds absent............................................3

2a)Light-colored upper lip stripe extending to shoulder.......................................................................A. monticola group

2b)Light-colored upper lip stripe absent...........................................................................................A. chayuensis group

3a)Males without nuptial pad on first finger.............................................................................................A. hainanensis group

3b)Males with nuptial pad on first finger..................................4

4a)Nuptial pad with conical or papillate nuptial spines............5

4b)Nuptial pad without conical or papillate nuptial spines.......6

5a)Disc of first finger distinctly smaller than that of second finger...............................................................A. ricketti group

5b)Disc of first finger distinctly larger than that of second finger.................................................A. spinapectoralis group

6a)Vocal sac in males present and circummarginal groove on disc of finger I present..............................................................7

6b)Not possessing above two characters at same time..........9

7a)Tarsal fold and tarsal glands absent.............................................................................................A. marmoratus group

7b)Tarsal fold or tarsal glands present....................................8

8a)Vomerine teeth present.......................A. larutensis group

8b)Vomerine teeth absent.....................A. daiyunensis group

9a)Large body size, usually SVL>70 mm in males; not possessing glands in incomplete series along dorsolateral junction.............................................A. viridimaculatus group

9b)Moderate or small body size, SVL<65 mm in males;sometimes possessing glands in incomplete series along dorsolateral junction................................A. mantzorum group

Key to Chinese species of Amolops monticola group

1a)Vocal sacs absent in males................................................2

1b)Vocal sacs present in males...............................................4

2a)Circummarginal groove absent on tip of finger I..........................................................................................A. bellulus

2b)Circummarginal groove present on tip of finger I...............3

3a)Patch of grayish white microgranules on chest present in males.............................................................................A. deng

3b)Patch of grayish white microgranules on chest absent in males..............................................................A. nyingchiensis

4a)Coloration of dorsal body green in life................................5

4b)Coloration of dorsal body brown in life...............................7

5a)Distinct transverse bands on dorsal surfaces of limbs,white spinules on posterior part of dorsolateral folds....................................................................................A. mengdingensis

5b)Indistinct transverse bands on dorsal surfaces of limbs,without white spinules on posterior part of dorsolateral folds.............................................................................A. wenshanensis

6a)Lateral sides green in life............................A. tuanjieensis

6b)Lateral sides not green in life.............................................7

7a)Snout-vent length in males larger than 50 mm...................................................................................A. aniqiaoensis

7b)Snout-vent length in males less than 50 mm.....................8

8a)Tympanum diameter less than half of eye diameter............................................................................A. mengyangensis

8b)Tympanum diameter larger than half of eye diameter.......9

9a)White tubercles present on dorsal side of posterior body,distinct tubercles on dorsal thigh, white spinose tubercles on dorsal tibia, and white tubercles on temporal region, toe webbing not reaching disk but reaching disk by dermal fringe on inner side of toe II...................Amolops chaochin sp. nov.

9b)Above tubercles absent, toe webbing reaching disk on inner side of toe II..........................................A. chunganensis

NOMENCLATURAL ACTS REGlSTRATlON

The electronic version of this article in portable document format represents a published work according to the International Commission on Zoological Nomenclature (ICZN),and hence the new names contained in the electronic version are effectively published under that Code from the electronic edition alone (see Articles 8.5-8.6 of the Code). This published work and the nomenclatural acts it contains have been registered in ZooBank, the online registration system for the ICZN. The ZooBank LSIDs (Life Science Identifiers) can be resolved and the associated information can be viewed through any standard web browser by appending the LSID to the prefix http://zoobank.org/.

Publication LSID:

urn:lsid:zoobank.org:pub: E5EB662A-C0AB-47F4-B16E-38D8 10D38FF6.

Amolops chaochinLSID:

urn:lsid:zoobank.org:act: D5788B93-C880-453E-A820-0737 05499AAE.

SClENTlFlC FlELD SURVEY PERMlSSlON lNFORMATlON

Permission for field surveys in Chengdu was granted by the Chengdu Municipal Park City Construction and Management Bureau (No. CDGYCS2019-SW08).

SUPPLEMENTARY DATA

Supplementary data to this article can be found online.

COMPETlNG lNTERESTS

The authors declare that they have no competing interests.

AUTHORS’ CONTRlBUTlONS

K.J., J.L.R., and Z.T.L. prepared the manuscript with input from all other authors. J.W.W. and J.T.L. revised the manuscript. J.L.R. and Z.T.L. collected the specimens in the field. K.J. and K.L. collected morphological data. D.W. and Z.W. collected genetic data. J.L.R. analyzed the data. All a uthors read and approved the final version of the manuscript.

ACKNOWLEDGEMENTS

We thank Prof. Yue-Zhao Wang, Mr. Wei Wu, Mr. Xin-Yu Li,Mr. Di-Hao Wu (CIB), Mr. Jia-Jun Zhou (Zhejiang Forest Resource Monitoring Center), Dr. Ying-Yong Wang, Mr. Zhao-Chi Zeng (SYS), Mr. Mian Hou (Sichuan Normal University),and the Jiangxi Wuyishan National Nature Reserve for help in fieldwork. We also thank Dr. Bin Wang (CIB) and Mr. Shuo Liu(KIZ) for help in specimen examination and Dr. Bi-Cheng Zhu(CIB) for help in acoustic analyses.