Jiang et al. (2019) used a mitochondrial phylogeny, “distinct morphological differences,” geographic distribution patterns, and reproductive modes to diagnose the three subclades of Rhacophorus sensu lato as the genera Rhacophorus sensu stricto, Leptomantis, and Zhangixalus. However, our evaluation of the six morphological characters presented by Jiang et al. (2019) demonstrate that the diagnostic characters were objectively inaccurate and not operationally diagnostic. Body size and dorsal coloration are highly variable and overlap across genera; longitudinal dermal folds on limbs are purportedly absent in both Leptomantis and Zhangixalus (Jiang et al. 2019) but are actually present, for example, in Z. achantharrhena (Harvey, Pemberton & Smith, 2002), Z. pachyproctusYu et al., 2019, Z. dulitensis (Boulenger, 1892), Z. prominanus (Smith, 1924), and Z. frankiNinh et al., 2020 (Harvey et al. 2002; Inger et al. 2017; Yu et al. 2019; Ninh et al. 2020; Haas et al. 2021); a supracloacal fold is purportedly absent in Zhangixalus (Jiang et al. 2019) but is actually present, for example, in Z. dorsoviridis (Bourret, 1937), Z. pachyproctus, Z. dulitensis, and Z. prominanus (Zhang et al. 2011; Inger et al. 2017; Yu et al. 2019; Haas et al. 2021); upper eyelid projections are absent in all three genera, or present (only) in Leptomantis (Jiang et al. 2019). Thus, the non-exclusiveness of these characters provides no diagnostic utility, and none of the characters that putatively distinguish the three genera comply with the Phenotypic Diagnosability TNC.

The distribution of Leptomantis was described as Maritime Southeast Asia, whereas Rhacophorus sensu stricto was reported from across Southeast Asia (Jiang et al. 2019). However, the former is almost a complete subset of the latter (Jiang et al. 2019: fig. 2) and hence, has no differentiating power in terms of biogeography. The distribution of Zhangixalus was stated as eastern Asia and northern Indochina, which is erroneous as Z. achantharrhena occurs in Indonesia (Harvey et al. 2002), while Z. dulitensis and Z. prominanus occur in Malaysia (Chan et al. 2010; Inger et al. 2017). Although genomic data showed that clade support for the monophyly of Leptomantis and Zhangixalus is strong (Chan et al. 2020c; Chen et al. 2020), there are no clear differences in morphology, ecology, or distribution (secondary and accessory TNCs; Vences et al. 2013) that can reliably diagnose Leptomantis, Zhangixalus, and Rhacophorus sensu stricto. Thus, we formally propose to assign Leptomantis Peters, 1867 and Zhangixalus Li, Jiang, Ren & Jiang, 2019 (in Jiang et al. 2019) to the subgenus rank within the genus Rhacophorus Kuhl & van Hasselt, 1822.

Tamixalus and Vampyrius were proposed as monotypic genera that were previously congeneric with Rhacophorus. Their recognition as distinct genera was solely based on their phylogenetic positions that were inferred to be paraphyletic with regard to Rhacophorus (Dubois et al. 2021). However, these relationships were not strongly supported. According to Dubois et al. (2021), the genus Vampyrius is sister to the genus Gracixalus with weak support, which is not surprising because the sequence data available to them for Vampyrius on GenBank (Benson et al. 2017) was demonstrably insufficient (fewer than 600 bps of a partial 16S mtDNA fragment; see Chan et al. 2022a). In contrast, the genomic study by Chan et al. (2020c), which included genomic sequences of Vampyrius and several species of Gracixalus, and was based on a dataset comprising more than 2.5 million bps in length, inferred Vampyrius within the genus Rhacophorus with strong support. Similarly, Dubois et al. (2021) established the genus Tamixalus based on its weakly supported relationship as the sister lineage to the clade comprising Feihyla + Ghatixalus + Taruga + Polypedates (also derived from < 600 bps of a partial 16S mitochondrial fragment). Other studies have shown Tamixalus to be nested within Rhacophorus (Biju et al. 2016; Pan et al. 2017). The genus Orixalus is a subclade within Gracixalus (Dubois et al. 2021) and thus, has no precedent to be recognized as a distinct genus. Furthermore, the “diagnoses” for Tamixalus, Vampyrius, and Orixalus were merely recapitulations of morphological diagnoses from previously published descriptions (see Dubois et al. 2021) without any context to their relevance when compared to related taxa; hence, such non-diagnostic “diagnoses” do not demonstrate diagnosability in the context of the Phenotypic Diagnosability TNC. We, therefore, consider Tamixalus Dubois, Ohler & Pyron, 2021 syn. nov. and Vampyrius Dubois, Ohler & Pyron, 2021 syn. nov. to be junior subjective synonyms of Rhacophorus Kuhl & van Hasselt, 1822, and Orixalus Dubois, Ohler & Pyron, 2021 syn. nov. a junior subjective synonym of Gracixalus Delorme, Dubois, Grosjean & Ohler, 2005.

Our proposed treatment of Zhangixalus at the rank of subgenus requires the return of 37 (most) species back to the genus Rhacophorus in which they all have either been originally named or had been placed almost continuously for several decades before the most recent episode of taxonomic rearrangements. Four species have been recently named in Zhangixalus (Yu et al. 2019; Nguyen et al. 2020; Ninh et al. 2020; Brakels et al. 2023), so their reallocation to Rhacophorus requires the creation of the following new combinations: Rhacophorus (Zhangixalus) franki (Ninh et al., 2020) comb. nov., Rhacophorus (Zhangixalus) jodiae (Nguyen et al., 2020) comb. nov., Rhacophorus (Zhangixalus) melanoleucus (Brakels et al. 2023) comb. nov., Rhacophorus (Zhangixalus) pachyproctus (Yu et al., 2019) comb. nov. The proposed treatment of Leptomantis as a subgenus-level taxon and the synonymy of Tamixalus and Vampyrius requires only that all those species be returned to the genus Rhacophorus, without the need for the creation of any new binomial combinations. The same applies to the synonymy of Orixalus into Gracixalus.

Justification for the formation of the genus Rohanixalus was partly based on its phylogenetic position as the sister lineage to Chiromantis Peters, 1854 as opposed to Feihyla, despite weak node support (Biju et al. 2020). This relationship was also recovered in previous studies (Pyron and Wiens 2011; Meegaskumbura et al. 2015). Alternatively, other studies have recovered Rohanixalus within the Feihyla clade, implying that Rohanixalus could be congeneric with Feihyla (Hertwig et al. 2013; Li et al. 2013; Chan et al. 2018). Although the aforementioned studies were based on a limited number of Sanger-derived markers, had weak branch support, and thus, could not reject either hypothesis, two recent independent studies that employed different sets of genomic markers and analytical methods conclusively demonstrated that Rohanixalus forms a clade with Feihyla with strong support (Chan et al. 2020c; Chen et al. 2020). Chan et al. (2020c) further demonstrated that high levels of gene tree discordance and incomplete lineage sorting were the deterministic processes underlying the conflicting phylogenetic relationships of numerous rhacophorid clades. In our ML analysis, the inclusion of new Rohanixalus sequences did not alter the initial topology inferred by Chan et al. (2018). Rohanixalus was not reciprocally monophyletic with Feihyla and was inferred as the sister lineage to the F. kajau + F. inexpectata clade with moderate support (bootstrap = 77; Fig. S1). These results demonstrate that Sanger markers are insufficient to resolve the phylogenetic placement of Rohanixalus.

In their “Comparison” section, Biju et al. (2020) stated that Rohanixalus can be distinguished from Feihyla by the following characters: (i) “the presence of a pair of contrasting light-colored dorsolateral stripes (with variable degree of prominence, prominent to faint, continuous or discontinuous) starting from the snout tip, extending over the upper eyelid margins, and ending close to the vent on either side (vs. absent…);” (ii) “presence of prominent and dense minute speckles throughout the dorsal and lateral surfaces of the body (including dorsum, lateral surfaces, and dorsal surface of limbs) (vs. absent);” (iii) “freshly laid eggs light green and unpigmented (vs. creamy-white with pigmentation on poles, except in some members of Feihyla vittiger group);” (iv) “eggs laid in bubble nests (vs. jelly nests);” and (v) “absence of a prominent white streak along the upper lip margins from below the eye up to shoulder (vs. present).” We found all these characters to have been improperly characterized, four were not mutually exclusive and the fifth character is only questionably diagnostic for adults of these two groups. The presence of dorsolateral stripes is not only known to be variable within several rhacophorid genera [e.g., not just in Rhacophorus which was implied in Biju et al. (2020), but also in Polypedates, RaorchestesBiju et al., 2010, and Pseudophilautus Laurent, 1943; Manamendra-Arachchi and Pethiyagoda (2005); Biju and Bossuyt (2009)], but also even within species [e.g., Raorchestes akroparallagi (Biju & Bossuyt, 2009), Pseudophilautus pleurotaenia (Boulenger, 1904); Manamendra-Arachchi and Pethiyagoda (2005); Biju and Bossuyt (2009)], and was even shown to be occasionally indiscernible in Rohanixalus (see Biju et al. 2020: fig. 7D). The presence of speckling is not exclusive to Rohanixalus as some individuals of F. vittiger (Boulenger, 1897) also have distinct speckling on their dorsal and lateral surfaces (e.g., Biju et al. 2020: fig. 6H). The light green and unpigmented eggs in Rohanixalus are not unique to this genus, as the authors themselves noted for the F. vittiger group [further corroborated by Kusrini et al. (2017)].

Biju et al. (2020) stated in their “Comparison” section for Rohanixalus (point iv, above) that Feihyla and Rohanixalus differed regarding their nest structures but gave conflicting information elsewhere in their paper. The “Diagnosis” section for Feihyla stated “…; eggs laid in terrestrial jelly nests (Fig. 3)”, and in the “Discussion” section, they stated, “Feihyla have jelly-nests with a complete absence of bubbles even in freshly laid egg clutches”. However, Biju et al. (2020: fig. 3F) gave a “schematic illustration of egg clutch morphology in the Feihyla vittiger group” directly referring to it as a “bubble nest” in the figure, thus demonstrating that Feihyla can have either a “jelly” or “bubble” nest. Confusingly, Biju et al. (2020) also referred to the nests of Rohanixalus as a “jelly-nest” in several places (e.g., in their fig. 10 caption). The distinction between bubble and jelly nesting requires further investigation. Numerous “bubble” nests of Rohanixalus depicted in Biju et al. (2020: figs 10A, C, 18H) appear to be essentially bubble-free, including a relatively fresh one-day-old egg clutch depicted in their fig. 11B.

Finally, the fifth stated diagnostic character for Feihyla is neither consistent, given as “prominent white streak along the upper lip margins from below the eye up to shoulder” in the comparison for Rohanixalus, or stated in the “Diagnosis” section for Feihyla as “a white streak extends along the upper lip margins, either from below the eye up to the shoulder (in Feihyla palpebralis group) or from snout tip to the groin (in Feihyla vittiger group)”, nor is it properly characterized in either description since in some cases details given in the original descriptions of the species have been apparently overlooked for the species diagnoses sections in Biju et al. (2020). For example, in some individuals of F. kajau (Dring, 1983), F. vittiger, and F. inexpectata (Matsui, Shimada & Sudin, 2014), this stripe is thin (not “prominent”), irregular, can begin below the nostril or at the anterior border of the orbit, extending around the ventral border of orbits, across or above the tympanum (but not bordering the upper lip margin in these species), and ends on the mid-flanks in some individuals or continues to the inguinal region in others (e.g., Pratihar et al. 2014: fig. 104; Haas et al. 2018: fig. 5, 2021; Biju et al. 2020: fig. 6). In the holotype description of F. kajau, Dring (1983) wrote “Upper lip, temporal area below supratympanic ridge, lower flanks, entire inguinal area, … all unpigmented, except for white spots on lips, tympanum, flanks, …”, and in the variation section (for eight paratypes) Dring (1983) wrote “There is little pattern variation, but sometimes the lateral white pigment forms a broken band from below the eye to the mid-flank.” In contrast, and despite citing Dring (1983), Biju et al. (2020) wrote in the species “Diagnosis” for F. kajau “presence of a narrow white streak starting from the snout tip and extending along the lateral surfaces up to the groin, that separates the dorsal and lateral body colouration”. Similarly, in the original description of F. inexpectata, Matsui et al. (2014) stated that the white stripe extended to half the body length in the holotype and adult paratype, but for the juvenile paratype, “ventral white stripe is not recognizable”. In contrast, Biju et al. (2020) wrote in the species diagnosis for F. inexpectata, “a narrow white streak starting from the snout tip and extending along the lateral surfaces up to the groin…”. In this case, no citation was provided for the characters listed in their species “Diagnosis”, and besides mentioning the examination of “Chinese Feihyla specimens, including the type series of F. fuhua”, no voucher specimen numbers of any examined Feihyla species were explicitly listed in Biju et al. (2020). Besides the photographed animals shown in the figures, it is not clear from where the information provided in this section originated. In the Feihyla palpebralis group, the streak extends beyond the shoulder, and nearly to the groin on some individuals (e.g., Biju et al. 2020: fig. 5A, B). No white streak or “spots” are present laterally on the head in Rohanixalus that we are aware of making this perhaps the only character to potentially diagnose adult individuals of these two groups, however this character is apparently highly variable, and reported as “not recognizable” on at least one juvenile (Matsui et al. 2014). Morphological variation in all Feihyla species is still very poorly documented in the literature and considering many rhacophorid genera exhibit high levels of variation in markings that exceeds those seen in Feihyla sensu lato, we consider that this character alone is insufficient to justify splitting the genus.

Dubois et al. (2021) synonymized Rohanixalus with Feihyla, though without providing any discussion or justifications besides the position of taxa in their phylogeny. The community is currently divided on the correct genus name for this clade, e.g., Portik et al. (2023b) followed the synonymy of Rohanixalus, whereas Ellepola et al. (2022) and Liu et al. (2023) treated Rohanixalus as valid. Our study substantiates the synonymization of Rohanixalus with Feihyla by demonstrating that only one of the stated diagnostic characters proposed for Rohanixalus in Biju et al. (2020) might be diagnostic pending further study. Furthermore, genomic analyses indicate that Rohanixalus forms a clade with Feihyla (Chan et al. 2020c; Chen et al. 2020). Although there is evidence to support the monophyly of the Rohanixalus clade, its uncertain phylogenetic placement and the lack of proper diagnostic characters do not comply with the Clade Stability and Phenotypic Diagnosability priority TNCs and as such do not warrant generic recognition. Thus, we confirm the proposed synonymization of Dubois et al. (2021) and consider RohanixalusBiju et al., 2020, to be a junior subjective synonym of FeihylaFrost et al., 2006. Our proposed synonymy requires F. hansenae (Cochran, 1927) and F. vittata (Boulenger, 1887) to be returned to the genus Feihyla, and the formal genus reallocation resulting in new binomial combinations for the following five species that prior to Biju et al. (2020), four were placed in the genera Chirixalus Boulenger, 1893 or Chiromantis (Wilkinson et al. 2003; Chan et al. 2011; Riyanto and Kurniati 2014), or one has subsequently been described as new (Liu et al. 2023): Feihyla baladika (Riyanto & Kurniati, 2014) comb. nov., Feihyla marginis (Chan et al., 2011) comb. nov., Feihyla nauli (Riyanto & Kurniati, 2014) comb. nov., and Feihyla punctata (Wilkinson et al., 2003) comb. nov., and Feihyla wuguanfui (Liu et al., 2023) comb. nov. Biju et al. (2020), presumably unintentionally, also created the new binomial combinations of “Feihyla senapatiensis” (Mathew & Sen, 2009) and “Feihyla shyamrupus” (Chanda & Ghosh, 1989) in the captions for their figures 17, and 18 and 19, respectively. The species epithet for F. punctata is here changed from “punctatus” to accommodate the feminine genus name Feihyla. How to treat the species epithet “shyamrupus” is not so obvious. According to Chanda and Ghosh (1989), “The species is named after Dr. Shyamrup Biswas, …”, who was a man. Rather than adopting the typical naming convention for a species epithet formed as a patronym, i.e., as a noun in the genitive case, “shyamrupi” (ICZN 1999; Art. 31.1.2), the authors instead chose to Latinize the personal name by adding the suffix -us and thus treating it as a noun in apposition. This treatment is acceptable according to the Code (ICZN 1999; Art. 31.1), so the gender of the specific epithet does not change, i.e., Feihyla shyamrupus (Chanda & Ghosh, 1989).

Meegaskumbura et al. (2010) erected a new genus, Taruga, to represent the clade of Polypedates that is sister to a second clade that contains all other Polypedates species, and diagnosed the two clades from each other based on a comparison of morphological data obtained from a very limited sample of species. Adult specimens of all three Taruga species [T. eques (Günther, 1858), T. fastigo (Manamendra-Arachchi & Pethiyagoda, 2001), and T. longinasus (Ahl, 1927)] were compared only against specimens of three other Polypedates species [P. maculatus (Gray, 1830), P. cruciger Blyth, 1852, and P. leucomystax (Gravenhorst, 1829)––out of 20 valid species recognized at that time]. Here, we provide the stated diagnostic characters and evidence that demonstrates that those characters are not unique to the clade described as Taruga: (i) “Taruga possess a dorsolateral glandular fold that extends from the posterior margin of the upper eyelid to the mid-flank (vs. a supratympanic fold that curves over the dorsal margin of the tympanic membrane in Polypedates);”, we do not consider this character as diagnostic because many published photographs of Taruga clearly show that the “dorsolateral glandular fold” does not extend to the mid-flank, but terminates above the forelimb insertion or slightly beyond (e.g., T. eques: Dawundasekara and De Silva 2011: fig. on pg. 30; T. fastigo: Manamendra-Arachchi and Pethiyagoda 2001: fig. 1; Meegaskumbura et al. 2010: fig. 2; T. longinasus: Bopage et al. 2011: fig. 1C; Peabotuwage et al. 2012: fig. 14), no different to the supratympanic folds in other Polypedates species. Also, the supratympanic folds in most Polypedates are straight (not curved); (ii) “a prominent calcar at the distal end of the tibia (absent in most Polypedates)”, as indicated, this is not an exclusive or robust character as a prominent calcar is present in P. otilophus (Boulenger, 1893) and P. pseudotilophus Matsui, Hamidy & Kuraishi, 2014 (Boulenger 1893; Matsui et al. 2014a), a blunt calcar in P. ranwellai Wickramasinghe, Munindradasa & Fernando, 2012 (Wickramasinghe et al. 2012), or a calcar that is reduced to a tubercle on some other taxa [e.g., P. colletti (Boulenger, 1890) and P. discantus Rujirawan, Stuart & Aowphol, 2013 (Rujirawan et al. 2013)]; (iii) “a more acutely pointed snout;”, the three Taruga species were only compared with P. cruciger and P. maculatus, and not with species that have distinctly more pointed snouts such as P. colletti (Inger et al. 2017), P. otilophus, and P. pseudotilophus (Matsui et al. 2014a). Furthermore, the degree of “pointedness” within Taruga also varies between species and the sexes. For example, T. eques has a markedly less “pointy” snout compared to T. fastigo and T. longinasus and no intraspecies variation was provided (Meegaskumbura et al. 2011). This qualitative character provides no objective distinguishing properties and hence, does not qualify as a diagnostic character; (iv) “6–10 prominent conical tubercles surrounding the cloaca (absent in Polypedates);”, some Polypedates species also possess tubercles on the cloacal region (e.g., P. discantus: Rujirawan et al. 2013). In addition to comparing adult specimens, tadpole specimens were compared between T. eques and P. cruciger. However, no attempt was made to expand the comparison to include tadpole descriptions of other Polypedates species and the authors even suggested that further work is required to determine if the differences observed were diagnostic for the genera. Senevirathne et al. (2017) made a detailed comparison of osteological characters between Taruga eques, T. longinasus, P. cruciger, and P. maculatus and identified some additional characters that diagnosed these two pairs of species. But such limited sampling of Polypedates (two of 24 valid species ca. 2017, which excluded the type species, P. leucomystax), prevents any meaningful assessment of the diagnostic utility of these characters at the genus level. In terms of priority TNCs, Taruga satisfies the monophyly and clade stability criteria but not the phenotypic diagnosability criterion. Therefore, we recommend that Taruga Meegaskumbura et al., 2010 be considered a subgenus of Polypedates Tschudi, 1838, and recognize its sister clade as the nominal subgenus, Polypedates (Polypedates), which contains all remaining species in the genus. The proposed relegation of Taruga to the subgenus rank returns the three currently valid taxa back to their previously widely accepted species-genus combinations.

The genus Nanohyla was split from the genus Microhyla based on monophyly, morphological diagnosability, biogeography, and clade age, which the authors claimed to satisfy all three priority TNCs of Monophyly, Clade Stability, and Diagnosability, as well as the secondary TNCs of Time Banding and Biogeography (Gorin et al. 2021). We demonstrate that of all those criteria, only monophyly and clade stability were adequately satisfied, albeit less important because Nanohyla is reciprocally monophyletic with Microhyla. Below, we provide justifications in support of our argument:

Phrynoglossus was removed from the synonymy of Occidozyga and elevated to the genus level by Köhler et al. (2021) based on reciprocal monophyly with Occidozyga and various aspects of morphology, ecology, and amplexus mode. However, their inferred reciprocal monophyly was based on a phylogeny that only included taxa from Indochina, neglecting the majority of other species of Occidozyga that occur throughout the countries of Malaysia, Indonesia, and the Philippines (Frost 2024), many of which had representative sequences on GenBank. Dubois et al. (2021) established the genus-level name Frethia for the species previously known as Occidozyga celebensis Smith, 1927, O. diminutiva (Taylor, 1922), O. floresiana Mertens, 1927, O. laevis (Günther, 1858), O. semipalmata Smith, 1927, and O. tompotika Iskandar, Arifin & Rachmanasah, 2011, and further resurrected the genus-level name Oreobatrachus for the species previously known as Occidozyga baluensis (Boulenger, 1896). However, this decision was solely based on a weakly supported and highly incomplete phylogeny of Occidozyga sensu lato represented by only five out of the then 15 described taxa. The expanded phylogeny presented here, which includes 13 out of 18 described species shows that Frethia and Phrynoglossus are not monophyletic and that the recognition of Oreobatrachus induces paraphyly within the baluensis + diminutiva clade (Fig. 2; also see Chan et al. 2022a). Both the phylogenies presented here and in Dubois et al. (2021) have numerous poorly supported relationships, but the latter’s phylogeny is vastly under-represented. Despite this impediment, Dubois et al. (2021) proceeded to establish the new genera without presenting any supporting information, accompanying data, new analyses, or provision of diagnostic characters. The negative ramifications of this untenable practice are exemplified by the phylogenetically incoherent allocations of numerous species such as the assignment of Occidozyga sumatrana (Peters, 1877) to Phrynoglossus; and O. diminutiva, O. semipalmata, and O. celebensis to Frethia, all of which rendered their respective genera paraphyletic. Finally, Dubois et al. (2021) further assigned O. floresiana and O. tompotika to the genus Frethia without any supporting evidence. Specimens of those two species were not reported to have been examined, nor have they ever been sequenced, and hence, their generic allocation appears to be conjecture. The classification proposed by Dubois et al. (2021) also leaves numerous distinct lineages without a genus including lineages previously assignable to O. cf. rhacoda, O. cf. baluensis (Flury et al. 2021) and O. berbeza Matsui et al., 2021 (Fig. 2). We do not claim our phylogeny to be more accurate because several major clades remain poorly supported (Fig. 2). Moreover, the first and only genomic study of this group to-date that analyzed ~2.7 million base pairs comprising more than 1.2 million parsimony-informative-sites also failed to resolve fully the relationships among all Occidozyga species and further demonstrated that extensive gene flow produced misleading patterns of phylogenetic topology and clade divergence (Chan et al. 2022b). Because the generic classification proposed by Köhler et al. (2021) and Dubois et al. (2021) not only fails to satisfy any TNCs but also creates additional taxonomic chaos, we agree with Lyu et al. (2022) for the return of the genera Phrynoglossus Peters, 1867 and Oreobatrachus Boulenger, 1896 to the synonymy of Occidozyga and the synonymization of the genus Frethia Dubois, Ohler & Pyron, 2021 with Occidozyga Kuhl & van Hasselt, 1822 to preserve taxonomic stability until more robust data suggests otherwise. This taxonomic action restores most species to their long accepted binomial combinations except for the following two recently described species: Occidozyga myanhessei (Köhler, Vargas, Than & Thammachoti, 2021, in Köhler et al. 2021), and Occidozyga swanbornorum (Trageser et al., 2021), which were recently published in this combination by Chen et al. (2022) and Lyu et al. (2022), who also provisionally rejected the splitting of Occidozyga on the grounds of inadequate species sampling and lack of nuDNA sequence data used in Dubois et al. (2021) and Köhler et al. (2021).

Oliver et al. (2015) split the long recognized monophyletic genus Hylarana, elevating eight subgenera to the genus rank (Amnirana, Chalcorana, Humerana, Hydrophylax, Hylarana, Papurana, Pulchrana, Sylvirana) and creating two new genus-level names (Abavorana, Indosylvirana) based on phylogenetic relationships, biogeography, and purported diagnostic characters. Their phylogeny, that comprised 69 of the 97 taxa recognized at that time, was overall weakly supported and numerous proposed genera were not strongly supported as monophyletic (Oliver et al. 2015: fig 2). Oliver et al. (2015) used their phylogeny for the biogeographical analyses (ancestral area reconstructions) which ideally requires a well-supported phylogeny with complete (or near complete) extant taxon sampling to provide reasonably reliable estimates, hence, their dataset was inadequate for this kind of analysis. Although a subsequent genomic study by Chan et al. (2020b) was able to infer a more robust phylogeny, the taxonomic coverage was still relatively low. In their genomic tree (Chan et al. (2020b: fig. 1) comprising taxa from eight out of ten of the then recognized genera, only Chalcorana and Pulchrana formed a stable clade, while the relationships among other genera exhibited varying levels of gene tree discordance [Amnirana, Hylarana, Humerana, Hydrophylax, Sylvirana, Papurana and “Indosylvirana” nicobariensis (Stoliczka, 1870)]. Chan et al. (2020b: fig. 8) also analyzed a combined genomic and 16S dataset (adding 55 additional taxa from all genera), totalling 77 out of 103 currently recognized species, but still, the phylogenetic relationships among several of the currently recognized genera remained uncertain (i.e., within the clade comprising Indosylvirana, Hydrophylax, Sylvirana and Papurana and “Indosylvirana” nicobariensis). The topology of the genomic+16S tree differed from the tree derived from genomic data only (i.e., “Indosylvirana” nicobariensis was inferred as the sister lineage to Indosylvirana, albeit with weak branch support), further demonstrating that the evolutionary history of Hylarana sensu lato is far from being fully understood. Dubois et al. (2021) proposed to continue treating Abavorana as valid but synonymized all remaining genera into Hylarana due to low support obtained between the taxa in their phylogeny (comprising Sanger data), an opinion that was inconsistent with their proposals to split other genera that contained poorly supported subclades (e.g., Occidozyga). This synonymy has not been universally adopted (e.g., Conradie et al. 2023; Griesbaum et al. 2023). The estimated topology by Dubois et al. (2021) differed considerably from those obtained by Oliver et al. (2015) and Chan et al. (2020). For example, Chalcorana macrops (Boulenger, 1897) formed a unique clade with “Indosylvirana” nicobariensis and this clade was indicated as distantly related to both Chalcorana and Indosylvirana, whereas these two taxa were individually placed within these genera in Oliver et al. (2015) and Chan et al. (2020), respectively, though with low support in both studies. The topological incongruences between analyses using different datasets demonstrates continued instability in the Hylarana sensu lato. In all three studies (Oliver et al. 2015; Chan et al. 2020; Dubois et al. 2021), and others (e.g., Reilly et al. 2022; Portik et al. 2023b; Liu et al. 2024) the inclusion of taxa not previously sampled molecularly, but assigned to “genera” based on perceived morphological similarities, continue to demonstrate polyphyly in these Hylarana sensu lato genera indicating a lack of reliable morphological diagnosability for some of these clades. The combination of all these factors account as clade instability (Vences et al. 2013), and is in itself a strong argument against the ten-genus division of Hylarana sensu lato.

Oliver et al. (2015) presented 18 morphological characters that putatively diagnosed their proposed genera within Hylarana sensu lato. However, most of these characters were either qualitative and subject to interpretation and/or circumstances of preservation (e.g., skin texture) or represent variable characters pertaining to color pattern (e.g., dorsal coloration) and overlapping continuous traits (e.g., ratios of finger disc widths). The low diagnostic power of these characters was openly acknowledged by Oliver et al. (2015), who stated that their “diagnostic” characters were only potentially informative, primarily based on “states” reported in the literature or the examination of limited voucher specimens and may be subject to change following additional specimen-based research. Here, we provide additional data taken from our own examination of specimens and a wider review of the literature, to demonstrate that none of the morphological characters proposed by Oliver et al. (2015) can unambiguously diagnose any of their proposed genera (Table 1). Because their splitting of Hylarana does not fulfill either Clade Stability or Phenotypic Diagnosability TNCs, we formally relegate the following genus-level nomina to the subgenus rank within Hylarana Tschudi, 1838: Abavorana Oliver, Prendini, Kraus & Raxworthy, 2015, Amnirana Dubois, 1992, Chalcorana Dubois, 1992, Humerana Dubois, 1992, Hydrophylax Fitzinger, 1843, Indosylvirana Oliver, Prendini, Kraus & Raxworthy, 2015, Papurana Dubois, 1992, Pulchrana Dubois, 1992, Sylvirana Dubois, 1992.

Pterorana, is a poorly known monotypic genus created for a Hylarana-like species, P. khare Kiyasetuo & Khare, 1986, with the sole diagnostic character of having extensive loose skin folds on the flanks and legs of breeding males (Kiyasetuo and Khare 1986). This species has recently been included in several phylogenetic studies that resolved it as nested within Hylarana sensu lato (Hime et al. 2021; Muansanga et al. 2021; Portik et al. 2023a, 2023b). Hime et al. (2021) included a specimen (CAS 234711) collected from Chin State, Myanmar identified as P. khare (CAS Herpetology Collection Database, https://researcharchive.calacademy.org/research/herpetology/catalog/index.asp?xAction=getrec&close=true&CatalogNo=CAS+234711), represented by 194 out of total 220 loci of genomic data in their amphibian phylogeny. They resolved (100% bs in ML; 99.5 ASTRAL) this sample as sister to “Sylvirana” nigrovittata (Blyth, 1856), within a well-supported (100% bs in ML; 85.5 ASTRAL) clade that also included Papurana and Pulchrana. Portik et al. (2023a) included the 194 loci of Hime et al. (2021) in their anuran phylogeny that sampled representatives of all major Hylarana sensu lato subclades resolving P. khare as sister to Sylvirana (thus deeply nested within Hylarana sensu lato) in all trees. Portik et al. (2023b) expanded this dataset to include 5242 anurans species, including most (84 species) of Hylarana sensu lato and the aforementioned P. khare data, and resolved the sample as nested within a subclade of Sylvirana that received 100% support and included S. nigrovittata, the type species of Sylvirana. Muansanga et al. (2021) sequenced a partial 16S gene fragment from a P. khare specimen collected from Mizoram Sate, India, which they included in a partial 16S gene tree along with a selection of ranids that included at least one representative of most Hylarana sensu lato genera. Their tree was largely unresolved (e.g., Polypedates shown as nested within Ranidae) and generally uninformative. However, their P. khare sequence was fully resolved as a member of a clade also comprising a sequence (KU589215.1) identified as “Hydrophylax leptoglossa” (Cope, 1868) and five sequences of Sylvirana lacrima Sheridan & Stuart, 2018. The GenBank record for the aforementioned “H. leptoglossa” sequence, KU589215, cited both Ao et al. (2003) and Bortamuli et al. (2010) as the source and gave the voucher number IASST AR79, however, neither study mentioned examining this specimen nor did they mention generating any sequences. Further, Ao et al. (2003) did not mention collecting H. leptoglossa but did include three specimens (MA 115–117) they identified as “Rana khare”. Hydrophylax was also paraphyletic on their tree (Muansanga et al. 2021), forming three clades, one of which included three additional sequences from three different studies that were all identified as H. “leptoglossa”. A BLAST search of GenBank for one of these sequences (KR264065.1) shows that it is >98% identical to 23 other sequences identified as H. leptoglossa. We conclude that the “H. leptoglossa” sequence, KU589215.1, found to be sister to P. khare in Muansanga et al. (2021) is misidentified on GenBank and represents P. khare (>98% identical), or a very closely related species.

Biju et al. (2014) included sequences from a specimen (SDBDU 2009.293) collected from the type locality of H. danieli (Pillai & Chanda, 1977), but identified as “H. cf. danieli” in their ML analysis. This analysis comprised 2208 bp of concatenated mtDNA and nuDNA, and placed this specimen within a clade comprising Sylvirana species with relatively high support (bs 87%). Hylarana leptoglossa is the only other Hylarana species reported from the vicinity of the type locality, but only based on unverified anecdotal evidence (Mahony 2008). Therefore, we do not doubt the identity of the specimen reported in Biju et al. (2014) as “H. cf. danieli”. We did a BLAST of the partial 16S sequence (KM069009.1) of this H. danieli specimen and found it to be 98.6% identical to P. khare from Muansanga et al. (2021). Hylarana danieli is currently considered a junior subjective synonym of H. garoensis (Boulenger, 1920) (Ao et al. 2003) which together are herein considered to be very closely related to Pterorana khare based on genetic and morphological similarity (Boulenger 1920; Pillai and Chanda 1977; Ao et al. 2006; examined specimens).

The systematic position of Pterorana is not at all surprising. Dubois (1992) placed both Rana garoensis and Rana danieli in the genus Rana Linnaeus, 1758 (sensu Dubois 1992) subgenus Sylvirana, and considered Pterorana a subgenus closely related to Sylvirana based on general morphology. Ao et al. (2006) had a similar opinion but specifically excluded Pterorana from Sylvirana stating that it “lacks the beard-like papillae on lower lip of larvae, which are an apomorphic character for Sylvirana + Hylarana”. Chanda et al. (2001) rejected the synonymy of Pterorana into Rana by Dubois (1992) for the reason that Dubois had not examined the type specimens, and that they considered the “patagium” as a distinctive character. The loose skin on the flanks and hindlimbs originally considered unique is relatively common across the anuran tree on species that are largely aquatic in the breeding season (Ao et al. 2006; Zheng 2019), so this character alone is not considered taxonomically informative. Despite this, most subsequent authors treated Pterorana as valid (e.g., Frost et al. 2006). One of us (SM) has examined type material for P. khare, H. danieli and H. garoensis and found no diagnostic morphological characters that exclude these species from Hylarana sensu lato (Table 1). We herein formally synonymize Pterorana Kiyasetuo & Khare, 1986 with the subgenus Sylvirana Dubois, 1992 based on the combined morphological and strong molecular evidence that confirm this placement (Biju et al. 2014; Hime et al. 2021; Muansanga et al. 2021; Portik et al. 2023a, 2023b; Table 1).

The taxonomic hierarchical restructuring we propose here require the creation of new binomial combinations for a relatively small proportion of the included species, whereas all remaining taxa had either previously been placed within the genus Hylarana prior to the recent nomenclatural destabilization (Oliver et al. 2015; Dubois et al. 2021), or have most recently been published in combination with Hylarana by implication of proposals in Dubois et al. (2021). Unfortunately, the major systematic papers dealing with Hylarana suggested blanket rearrangements without explicitly listing all the included taxa with their updated binomials (i.e., Che et al. 2007; Oliver et al. 2015; Dubois et al. 2021). Following these proposals, Frost (2024, and earlier versions) implemented the changes on the Amphibian Species of the World online database citing those papers for the new genus-species combinations “by implication.” Subsequently, following the taxonomy in Frost (2024, and earlier versions) or the original papers that suggested rearrangements, some authors unknowingly/unintentionally published the new combinations for many Hylarana species for the first time in unexpected places (e.g., in species checklists, in phylogenetic trees, papers on parasitology, etc.), making it difficult, if not impossible, to determine who first used these new combinations, or whether some species have yet been published in combination with the genus Hylarana at all (e.g., in “gray literature”/obscure publications). For the following comb. nov. list, we provide the binomials that we think might not have been published previously based on a search of each species in Google Scholar as “Hylarana xxxx” and/or “H. xxxx.” We recognize the obvious limitations of this method and encourage more exhaustive literature searches for those interested in creating accurate chresonymies: Hylarana (Abavorana) decorata (Mocquard, 1890) comb. nov.; Hylarana (Abavorana) nazgul (Quah et al., 2017) comb. nov.; Hylarana (Amnirana) adiscifera (Schmidt & Inger, 1959) comb. nov.; Hylarana (Amnirana) parva (Griesbaum et al., 2023) comb. nov.; Hylarana (Pulchrana) fantastica (Arifin et al., 2018) comb. nov.; Hylarana (Sylvirana) khare (Kiyasetuo & Khare, 1986) comb. nov.