Taxonomic determination of Hypselotriton populations distributed in eastern Guangdong, China (Caudata, Salamandridae), with description of a new species and a new subgenus

In this work, the Hypselotriton populations distributed in eastern Guangdong, China are studied in detail to clarify their taxonomic status. Based on morphological comparison and phylogenetic analysis, H. glaucus syn. nov. is synonymised with H. orphicus . Hypselotriton ( Cynotriton ) oolong sp. nov. from Mt Fenghuang in Chaozhou which used to be misidentified as H. orphicus , is revealed to be an independent lineage of subgenus Cynotriton and can be distinguished from all known congeners in morphology. By contrast, H. orphicus did not cluster within Cynotriton , but gathered with H. jiaoren comb. nov. to form a distinct unnamed clade within the genus. We therefore re-delimitate the intrageneric classification of the genus and a new subgenus Hakkatriton subgen. nov. is erected, corresponding to this unnamed clade. The Chinese Fire-bellied Newt genus Hypselotriton currently contains three subgen-era and about ten known species. Identified keys to the subgenera and related congeners of genus Hypselotriton are further provided.


Introduction
The Fire-bellied Newts contain about 18 species distributed in China and Japan in East Asia (Raffaëlli 2022;Lyu et al. 2023a).In traditional configuration, these species were provisionally placed in a single genus Cynops Tschudi, 1838, in spite of several controversies (Zhao and Hu 1984;Zhao et al. 1988;Lyu et al. 2023a).However, recent phylogenetic studies suggested the Chinese and Japanese congeners are paraphyletic from each other (Rancilhac et al. 2021;Yuan et al. 2022).In the phylogenetic analysis, the Fire-bellied Newt species distributed in Japanese Archipelago are revealed to be the basal lineage of the Modern Asian Newts.Compared with the insular species, the Fire-bellied Newt species occurring in main-land China are phylogenetically closer to other newt genera from mainland China and Indochina, i.e.Pachytriton Boulenger, 1878, Paramesotriton Chang, 1935 and Laotriton Dubois & Raffaëlli, 2009(Rancilhac et al. 2021;Yuan et al. 2022).Thus, Raffaëlli (2022) partitioned these species into two independent genera, Cynops for the Japanese Fire-bellied Newts and Hypselotriton Wolterstorff, 1934 for the Chinese Fire-bellied Newts and which was followed in this work.Particularly, a recent work has described two new species of Chinese Fire-bellied Newts (Lyu et al. 2023a), but did not adopt the latest taxonomic proposal by Raffaëlli (2022) in a timely manner, resulting in two new nomenclature combinations in this work, H. jiaoren (Lyu, Qi & Wang, 2023), comb. nov. and H. maguae (Lyu, Qi & Wang, 2023), comb.nov.
Within the genus Hypselotriton, Dubois and Raffaëlli (2011) classified the congeners into two subgenera, based on morphological and geographical characteristics, Hypselotriton and Cynotriton Dubois & Raffaëlli, 2011, corresponding to the former Cynops wolterstorffi and Cynops orientalis groups, respectively (Zhao et al. 1988;Raffaëlli 2022).Nonetheless, phylogenetic analysis has suggested three distinct and divergent clades within the genus, indicating that the intrageneric classification of this genus requires re-delimitation (Lyu et al. 2023a).
The species diversity of Fire-bellied Newts was considered underestimated.Tominaga et al. (2013Tominaga et al. ( , 2015) ) have revealed multiple distinct lineages within Cynops pyrrhogaster (Boie, 1826).Compared with the traditional recognition of two known species for Japanese Fire-bellied Newts, Raffaëlli (2022) documented four nominated species and four unnamed species within the insular genus Cynops.Meanwhile, four new species of Hypselotriton have been described from Southeast Chinese Hilly Area since 2010, dramatically raising the diversity of this mainland genus (Wu et al. 2010;Yuan et al. 2013;Lyu et al. 2023a).However, the taxonomic status for several Hypselotriton species remains unresolved.Lyu et al. (2023a) have discussed the taxonomic confusion on the congeners from Yunnan-Guizhou Plateau in southwestern China that still require further studies.During our fieldwork and study on the Hypselotriton populations from Guangdong in southeastern China, we have found that the recognition on H. orphicus (Risch, 1983) is also with confusion, especially for its delimitation from another congener in eastern Guangdong, H. glaucus (Yuan, Jiang, Ding, Zhang & Che, 2013).
Hypselotriton orphicus was nominated by Risch (1983), based on specimens collected and primarily described by Gressitt (1941) from "Dayang (Tai-Yong), Shantou Region [now belonging to Jiexi County, Jieyang City], 23°35'N, 115°51'E [= 23.58°N, 115.85°E], altitude 640 m" (Fig. 1, sites 2-3).Hypselotriton glaucus was described, based on specimens collected from "Meiguang Village (23.67°N, 115.80°E; elevation 742 m), in Mt Lianhua, Wuhua County, Meizhou" (Fig. 1, site 9) (Yuan et al. 2013), where it is in close proximity to the type locality of H. orphicus.When proposing H. glaucus, the data from Jiexi County were not mentioned.Instead, two separate populations collected from Mt Fenghuang of Guangdong and Mt Daiyun of Fujian were recorded as H. orphicus and used for comparison (Yuan et al. 2013).Morphologically, the diagnostic characters of H. glaucus almost match the description of H. orphicus in Risch (1983), except for the irregular greyish-blue patches on the dorsum of H. glaucus.Such colour pattern was not described by Gressitt (1941) based on living or freshly-preserved specimens and would fade after preservation.Particularly, Risch (1983) has mentioned that the type series of H. orphicus are morphologically different from the population from central Fujian.Thus, the employment of specimens from Mt Daiyun, central Fujian (as well as those from Mt Fenghuang, eastern Guangdong) as H. orphicus might be problematic, which further adds to the confusion on the proposal of H. glaucus.
In this work, we perform morphological comparisons and molecular analyses on the topotypical population of Hypselotriton orphicus and H. glaucus, as well as on the Hypselotriton population from Mt Fenghuang (Fig. 1, site 1).The results suggest that H. glaucus is conspecific with H. orphicus, while the population from Mt Fenghuang represents an unnamed lineage of genus Hypselotriton that is described hereby.The taxonomic status for the population from central Fujian is also discussed.Furthermore, we re-delimitate the intrageneric classification of the genus, as well as proposing a new subgenus for the clade comprised of H. orphicus and H. jiaoren comb.nov.

Specimens and morphological analyses
A series of museum specimens of the genus Hypselotriton from eastern Guangdong were examined.Detailed information for these specimens is presented in related species accounts below.Abbreviations for museums and institutes include: GEP (Guangdong Polytechnic of Environmental Protection Engineering, Foshan, China), CIB (Herpetological Museum, Chengdu Institute of Biology, the Chinese Academy of Sciences, Chengdu, China), SYS (The Museum of Biology, Sun Yat-sen University, Guangzhou, China), MVZ (Museum of Vertebrate Zoology, University of California, Berkeley, USA), MNHN (Museum national d'Histoire naturelle, Paris, France), AMNH (American Museum of Natural History, New York, USA) and CAS (California Academy of Sciences, San Francisco, USA).
External measurements were made for the unnamed specimens with digital calipers (Neiko 01407A Stainless Steel 6-Inch Digital Caliper) to the nearest 0.1 mm.These measurements are as follows: total length (TOL) from tip of snout to tip of tail; snout-vent length (SVL) from tip of snout to posterior edge of vent; tail length (TAL) from posterior edge of vent to tip of tail; maximum tail depth (TAD); head length (HL) from tip of snout to the posterior edge of the parotoid gland; maximum head width (HW); snout length (SL) from tip of snout to the anterior corner of eye; eye diameter (ED) from the anterior corner to the posterior corner of the eye; interorbital distance (IOD) between the anterior corner of each eye; eye-nostril length (EN) from the anterior corner of the eye to the nostril; internasal distance (IND) between the external nares; axilla-groin length (AG) between the axilla and the groin along the body; fore-limb length (FLL) from elbow to tip of finger III; and hind-limb length (HLL) from knee to tip of toe III.

Phylogenetic analyses
In total, 76 samples were used for phylogenetic analyses, encompassing 11 newly-sequenced individuals (three of the Hypselotriton population from Mt Fenghuang, four of H. orphicus from Jiexi County and two from Fengshun County in Guangdong and two of H. yunnanensis from Honghe County in Yunnan) and others obtained from GenBank.
Genomic DNA was extracted, using a DNA extraction kit from Tiangen Biotech (Beijing) Co., Ltd.Two mitochondrion genes, namely NADH dehydrogenase subunit 2 (ND2) and Cytochrome b (cytb) were amplified for phylogenetic analyses.Primers for ND2 were L4437 (5'-AAGCTTTC-GGGCCCATACC-3') and 5081R (5'-GTCGTAGGGT-CAAAGCCTGC-3') and, for cytb, these were 14052F (5'-CCTGGGCTCTAACCAAGACC-3') and 15293R (5'-TCGGCTTACAAGACCGATGT-3').PCR amplifications were processed with the cycling conditions of: initial denaturing step at 95 °C for 4 min, 35 cycles of denaturing at 95 °C for 40 s, annealing at 53 °C for 34 s and extension at 72 °C for 60 s and a final extension step at 72 °C for 10 min.PCR products were purified with spin columns and then sequenced with both forward and reverse primers using BigDye Terminator Cycle Sequencing Kit from Applied Biosystems, on an ABI Prism 3730 automated DNA sequencer by Guangzhou Jierui Biotechnology Co., Ltd.All sequences were deposited in GenBank (Table 1).
For phylogenetic analyses, DNA sequences were aligned by the Clustal W algorithm with default parameters (Thompson et al. 1997).PartitionFinder2 was used to test the best partitioning scheme and jModelTest v.2.1.2was used to test the best fitting nucleotide substitution model.Bayesian Inference (BI) in MrBayes 3.2.4(Ronquist et al. 2012) and Maximum Likelihood (ML) in RAxML GUI (Silvestro and Michalak 2012) were used to conduct phylogenetic analyses.For the ML analysis, an optimal tree was obtained and branch supports were evaluated with 1000 rapid bootstrapping replicates.For the BI analysis, two independent runs with four Markov Chain Monte Carlo simulations were performed for ten million iterations and sampled every 1000 iterations.
The first 25% of the samples were discarded as burn-in after the standard deviation of split frequencies of the two runs was less than a value of 0.01.The remaining trees were used to create a consensus tree.

Results
The BI and ML analyses resulted in identical topologies (Fig. 2).Most major nodes were well supported with the Bayesian posterior probabilities (BPP) > 0.95 and the ML bootstrap supports (BS) > 70.All samples of Hypselotriton formed a monophyletic group, as the sister taxon to the monophyletic group including Paramesotriton, Pachytriton and Laotriton, but paraphyletic with Cynops.This is corresponding to previous studies (Rancilhac et al. 2021;Yuan et al. 2022), supporting the resurrection of Hypselotriton as a distinct genus.Within Hypselotriton, three distinct and divergent clades were revealed, as those recovered in Lyu et al. (2023a).Morphological comparisons further sustained the differences amongst these clades (present below), which are treated as representing three subgenera.The clade involving H. orientalis has been proposed as subgenus Cynotriton and the clade involving H. cyanurus is considered to represent the nominotypical subgenus Hypselotriton (Dubois and Raffaëlli 2011;Raffaëlli 2022).A new subgenus is nominated in this work to accommodate species within the remaining unnamed clade.
As shown in the tree, the Hypselotriton populations distributed in eastern Guangdong have been separated into two distinct and distant lineages.Topotypical samples of H. orphicus from Jiexi were clustered with samples of type series of H. glaucus in a lineage and almost without genetic divergences, indicating these samples should be conspe-cific.Morphological examination further confirmed such insight (present below).This lineage was the sister taxon to H. jiaoren comb.nov.from northern Guangdong and collectively constituted the new subgenus as mentioned above.
Samples of Hypselotriton population from Mt Fenghuang, which was employed as H. orphicus (Yuan et al. 2013(Yuan et al. , 2022;;Lyu et al. 2023a), formed an independent lineage within the subgenus Cynotriton, representing the southernmost lineage of this subgenus (Fig. 1).Specimens of this lineage showed distinct differences in morphology that can be distinguished from H. orphicus, as well as all known congeners of Hypselotriton.Thus, this lineage represents an unnamed species that is described in this work.Moreover, the samples of Hypselotriton population from central Fujian, which was also employed as H. orphicus (Yuan et al. 2013(Yuan et al. , 2022;;Lyu et al. 2023a), formed a distinct lineage as the sister taxon to the Mt Fenghuang lineage, with small genetic divergence.The taxonomic status of this lineage is further remarked below.
Distribution.Endemic in mainland China.
Remark.In spite of the paraphyletic relationships and distinct geographical isolation, species of the mainland genus Hypselotriton are very similar to those of insular genus Cynops in morphology, resulting in the prolonged categorising of these Fire-bellied Newts in a single genus.Hypselotriton can be distinguished from Cynops by the inconspicuous parotoid gland (vs.well developed) and smooth or slightly granular skin (vs.distinctly granular).Content and remarks.This subgenus includes all known Fire-bellied Newts populations distributed in the Yunnan-Guizhou Plateau in southwestern China.Currently, four nomenclatures have been provisionally documented, i.e. H. (Hy.) chenggongensis (Kou & Xing, 1983), H. (Hy.) cyanurus (Liu, Hu & Yang, 1962), H. (Hy.) wolterstorffi (Boulenger, 1905) and H. (Hy.) yunnanensis (Yang, 1979) (Lyu et al. 2023a).However, the exact taxonomic status for these populations/species is still unresolved (Raffaëlli 2022;Lyu et al. 2023a).Thus, it is improper to present a key to these nomenclatures before a comprehensive study to precisely delimitate their taxonomic placements.
Etymology.The nomen of Hakkatriton subgen.nov. is derived from Hakka, referring to its distribution in northern and eastern Guangdong where is the settlement of Hakka people and generic nomen Triton Laurenti, 1768. Diagnosis.
Content.Two species distributed in isolated regions in northern and eastern Guangdong in southern China, respectively (Fig. 1).
Common name.Dayang Fire-bellied Newt (in English) / cháo shàn róng yuán (潮汕蝾螈 in Chinese).Description of new specimens.Body slender and small-sized, TOL 68.5-77.0mm in adult males, 85.1-99.7 mm in adult females, with detailed measurements listed in Table 2. Head oval in dorsal view; snout truncate, projecting slightly beyond mandible; nostril small, but conspicuous; labial fold developed on posterior part of upper jaw; tongue elongate, enlarged anteriorly, with free lateral margin; vomerine tooth patch "^"-shaped; eye small, not extending beyond lateral margins of head; an inconspicuous longitudinal ridge found posterior to each eye; parotoid gland inconspicuous, gill remnants absent; gular fold absent.Surface smooth, finely granular; a few inconspicuous longitudinal wrinkles present on chin; continuous vertebral ridge weak and inconspicuous; cloacal opening oval, slightly protruding.
Limbs slender, fingers and toes overlapping when forelimb and hind-limb adpressed towards each other along body; four fingers and five toes, slender and elongated, lack webbing; relative length of fingers I < IV < II < III; relative length of toes I < V < II < IV < III.Tail laterally compressed, tapering posteriorly; caudal fin distinct; tail tip bluntly pointed.
Colouration of new specimens.In life, ground colour dark brown to olive brown, with irregular greyish-blue patches on dorsum and lateral tail; lateral tail with black spots; a single bright orange dot on insertion of upper forearm; tips of digits light yellow to bright orange; ground colour of venter dark brown with irregular bright orange patches, bright orange blotches on chin, ventral limbs and cloaca; ventral tail with a bright orange stripe (Fig. 3).
In preservation, ground colour dark brown, irregular greyish-blue patches on dorsum and lateral tail faded and almost invisible; black spots on lateral tail and bright orange dot on insertion of upper forearm faded; bright orange blotches on ventral trunk and tail, bright orange blotches on chin, ventral limbs and cloaca slightly faded, dark patches more distinct.
Variations.For measurements, see Table 2. Larger body size in females; cloaca wider and more swollen in males than in females; tail proportionally shorter and wider in males than in females; variable greyish-blue patches on dorsum and lateral tail in both breeding males and females.
Distribution and natural history.This species is known from multiple localities at elevations of 490-1500 m in the Lianhua Mountains and on the west of the Hanjiang River in eastern Guangdong (Fig. 1).
Adults are observed in wetlands, seasonal ponds, cultivated valleys and small lakes surrounded by forests from March to September.The breeding season is spring to summer.When breeding, a large number of individuals gather in the lentic water area.Males chase the females and show their courtship willingness by wagging their tails.Females lay eggs with jelly coating on tips of the leaves of aquatic plants.Eggs develop into larvae after about half a month and larvae develop into adults after about six to eight months.The newts feed on a variety of food sources, mainly small molluscs and arthropods in their habitat.Risch (1983) surmises that the newt might inhabit water all year round; however, adults leave the water from late September to early March to live on land until the next spring rains arrive.
Remarks.The type specimens of this species were reported to be collected from Tai-yong (Gressitt 1937(Gressitt , 1941;;Fig. 1, site 2).When describing them as a new species, Risch (1983) provided the type locality from traditional transliteration "Tai-yong" to current Pinyin as "Dayang".Risch (1983) further provided the coordinates for this locality as "23°35'N, 115°51'E [= 23.58°N, 115.85°E]"; however, this coordinate is located in Liangtian Township (Fig. 1, site 3) which is ca.15 km from Dayang Township.During the surveys across the region in Jiexi and Fengshun counties encompassing these two localities, we failed to observed Hypselotriton populations from the vicinity of both sites 2 and 3, possibly due to the development of urbanisation.Nonetheless, morphological characters of the specimens from neighbouring Mt Dabei, Mt Liwangzhang, Mt Hongtuzhang, Mt Tongguzhang and Mt Shijiadong (Fig. 1, sites 4-8) all match the original description of H. orphicus.
According to the original descriptions of Hypselotriton glaucus syn.nov.and H. (Ha.) orphicus, the only difference between them is the irregular greyish-blue patches on dorsum.Such colour pattern just occurs in the breeding living individuals and will fade after preservation according to our examinations.Thus, based on the morphological and phylogenetic results, we synonymised H. glaucus syn.nov.with H. (Ha.) orphicus.
Content.Four recognised species distributed in eastern China (Fig. 1).Hypselotriton (Cynotriton) oolong sp.nov. https://zoobank.org/7E9557A2-9C78-4227-B7C1-07ED6930D045 Cynops orphicus Risch, 1983-Fei et al. (2006, 2012) Etymology.The specific name oolong is used as a noun in apposition, derived from oolong tea.The type locality of this species, Mt Fenghuang, is famous for the cultivation and production of the Phoenix Oolong Tea.Yet, the developments of tea cultivation have affected and threatened the habitats of this species.We name this new species after the most famous local economic output in the hope that it would bring attention on the green and sustainable development as well as the harmonious co-existence between humanity and nature.This species name is also in memory of the Japanese manga artist Akira Toriyama (1955-2024).His most famous work, Dragon Ball, was originally inspired by Chinese culture and one of the characters is named as Oolong who makes the first shown wish with the Dragon Balls.
(1) small body size, TOL 69.9-70.7 mm in adult males; (2) parotoid gland inconspicuous; (3) postocular orange spot absent; (4) surface rough and granulated, gular fold present; (5) interrupted vertebral ridge conspicuous and bulged; (6) fingers and toes overlapping when fore-limb and hind-limb adpressed towards each other along body; (7) ground colour dark brown to olive brown with black spots; (8) lateral tail with black spots; (9) ground colour of venter dark brown with irregular bright orange patches, bright orange blotches on chin, base of ventral limbs and anterior half of cloaca; (10) ventral tail with a bright orange stripe.
Description of the holotype.Body slender and smallsized, TOL 70.7 mm.Head oval in dorsal view; snout truncate, projecting slightly beyond mandible; nostril small, but conspicuous; labial fold well developed on posterior part of upper jaw; tongue elongate, enlarged anteriorly, with free lateral margin; vomerine tooth patch "^"-shaped; eye small, not extending beyond lateral margins of head; a conspicuous longitudinal ridge found posterior to each eye; parotoid gland inconspicuous, gill remnants absent; gular fold present.
Surface rough, dense tapered granules and tiny spines on dorsum, flanks, limbs and tail; dense granules and inconspicuous wrinkles on venter; interrupted vertebral ridge conspicuous and bulged; cloacal opening oval, slightly protruding.
Limbs slender, fingers and toes overlapping when forelimb and hind-limb adpressed towards each other along body; four fingers and five toes, slender and elongated, lack webbing; relative length of fingers I < IV < II < III; relative length of toes I < V < II < IV < III.Tail laterally compressed, tapers posteriorly; caudal fin distinct; tail tip bluntly pointed.
Colouration of the holotype.In life, ground colour dark brown with black spots; vertebral ridge and upper margin of tail yellowish-brown; lateral tail with black spots; tips of digits light yellow; irregular bright orange stripe bordering dark patches on ventral trunk, bright orange blotches on chin, base of ventral limbs and anterior half of cloaca; ventral tail with a bright orange stripe.
In preservation, ground colour faded, greyish, black spots absent; vertebral ridge, upper margin of tail and digits dark grey; black spots on lateral tail indistinct; bright orange stripe on ventral trunk and tail, bright orange blotches on chin, ventral limbs and anterior half of cloaca slightly faded, dark patches more distinct.
Variations.Measurements of the type series are given in Table 2.All male specimens are similar in body proportions; however, the number, shape and position of ventral orange blotches vary amongst individuals.
Distribution and natural history.This species is known only from Tianchi Lake and surrounding streams of Mt Fenghuang at elevations of ca.1300 m.This locality is situated on the east of the Hanjiang River in eastern Guangdong, while the populations of H. (Ha.) orphicus were all discovered from the west of the Hanjiang River (Fig. 1).
The adult individuals inhabit puddles and slow streams that are surrounded by bushes and weeds.Fei et al. (2006) reported that 26 adults were observed from Mt Fenghuang during a survey in July 2002.However, only nine adults were observed in September 2019.The type locality is being threatened by the developments of tourism and tea planting, which might cause negative effects on this species.
Remarks.The Hypselotriton populations from central Fujian were originally reported as Cynops orientalis (Hu et al. 1978;Risch 1983).Fei et al. (2006) re-identified the specimens from Mt Daiyun as C. orphicus, based on the ventral colouration that is similar to the paratypes of C. orphicus preserved in MNHN.However, our morphological examinations found that such colouration could not be a distinguished character between the two species, which led to the misidentification.The phylogenetic analysis revealed close relationships between the central Fujian populations and the new species, however, with distinct genetic divergences.Their distribution areas are also distantly isolated (Fig. 1).As there is a lack of detailed morphological data of the Fujian populations for accurate identification, we prudently label them as Hypselotriton sp. in this work provisionally.

Discussion
For the intrageneric classification in zoology, subgenus and species group are usually employed.
Several recent works have referred to the usage of these ranks in particular groups (e.g.Lyu et al. (2021Lyu et al. ( , 2023b))).Subgenus is more official as it is regulated by the International Code of Zoological Nomenclature (the Code; available on https://www.iczn.org/the-code/the-codeonline/) in which a series of articles is formulated.For example, one of the requirements for the availability of a new subgenus is to provide a description or definition to differentiate the taxon (Article 13.1.1 of the Code).The species group is relatively flexible without clear rules, which was usually simply proposed for distinct phylogenetic clades and morphological definition is not mandatory (e.g.Boulenophrys omeimontis group in Lyu et al. (2023b)).In some cases, especially in the large genus containing numerous congeners, the subgenus and species group can be used simultaneously, while subgenus is always at the higher rank than species group indicating the subgenus possesses more distinct differences and divergences than the species group.Regardless, there are no strict standards on when to adopt subgenus or species group for classification and it usually depends on custom or subject tendencies.In the taxonomy of newt groups, subgenus is more welcome and widely used than species group.In a recent case for the intrageneric division of another newt genus Tylototriton Anderson, 1871, Lyu et al. (2021) suggested to partition the genus into three species groups while Raffaëlli (2022) replaced them with three subgenera that were previously nominated.Another newt genus Echinotriton Nussbaum & Brodie, 1982 has recently been partitioned into two subgenera (Dufresnes and Hernandez 2022).
The intrageneric classification of genus Hypselotriton is suggested for re-delimitation, as the result of a recent phylogenetic analysis (Lyu et al. 2023a).In this work, we further perform the morphological comparison amongst the three distinct lineages of the genus, which sustains the phylogenetic insights.Since two clades have been previously nominated, we provided a new subgenus for the third clade as Hakkatriton subgen.nov.(Fig. 2).Geographically, the subgenus Hypselotriton is endemic in Yunnan-Guizhou Plateau in southwestern China that is distinctly isolated from the other two subgenera.Cynotriton is primarily distributed in eastern China.The basal lineage of Cynotriton including H. (C.) orientalis and H. (C.) fudingensis occurs in the relatively northern area, while the southern members H. (C.) oolong sp.nov.and Hypselotriton sp. from Fujian are revealed to be relatively terminal in phylogeny, suggesting the subgenus immigrated and separated from north to south.Hakkatriton subgen.nov. is primarily distributed in southern China.Hypselotriton (Ha.) orphicus and H. (C.) oolong sp.nov.both occur in neighbouring areas of eastern Guangdong and Hanjiang River might act as an isolation barrier between them (Fig. 1).
During the reviewing stage, an anonymous reviewer has raised an important issue which requires the skeletal data for the subgeneric comparisons.We appreciate this comment very much, even though we have different considerations.Indeed, we would like to include the skeletal data when we initially proposed the new subgenus.Nonetheless, when we reviewed the literature, the published skeletal data is very inadequate for comprehensive comparison.Based on the limited skeletal data, Fei et al. (2006) and Fei and Ye (2016) compared Hypselotriton (Cynotriton) orientalis (as Cynops orientalis orientalis and Cynops orientalis qianshan Fei, Ye & Jiang, 2012), H. (Hy.) cyanurus (as Cynops cyanurus cyanurus), H. (Hy.) yunnanensis (as Cynops cyanurus chuxiongensis Fei & Ye, 1983), H. (Hy.) wolterstorffi and Cynops ensicauda (Hallowell, 1861).Their results showed that H. (Hy.) wolterstorffi possesses relatively different skeletal characters while those amongst other species are very similar.Thus, we consider that, in this newt group, the skeletal characters are not suitable to be used for subgeneric diagnosis, as it might vary within a subgenus such as H. (Hy.) wolterstorffi vs. H.(Hy.) yunnanensis, while it may be with little differences amongst subgenera or genera, such as H. (Hy.) cyanurus vs. H.(C.) orientalis vs. Cynops ensicauda.Besides, when Dubois and Raffaëlli (2011) erected the subgenus Cynotriton, the skeletal data were also excluded.The recognition of this subgenus has been steadily supported by both genetic relationship and external morphology.Furthermore, as the developments of new biotechnology, more and more higher ranks of amphibian groups are erected without skeletal data, but are supported by multiple series of molecular and external morphological evidences, such as the anuran genera Ghatixalus Biju, Roelants & Bossuyt, 2008, Sumaterana Arifin, Smart, Hertwig, Smith, Iskandar & 2018, Jingophrys Lyu & Wang, 2023 and the newt genus Laotriton Dubois & Raffaëlli, 2009and subgenera Hightonia Vieites, Nieto-Román, Wake & Wake, 2011and Sinotriton Hernandez & Dufresnes, 2022.The recognition of these ranks is not seriously affected despite the absence of skeletal data.

Figure 4 .
Figure 4.The holotype CIB 121430 of Hypselotriton (Cynotriton) oolong sp.nov. in life.A. Dorsal view; B. Ventral view; C. Lateral view of head; D. Dorsal view of head; E. Ventral view of hand; F. Ventral view of foot; G. Cloaca slit; H. Lateral view of tail.

Table 1 .
Localities, voucher information and GenBank accession numbers for all samples used in this study.