Microhyla Tschudi, 1838

Gorin, Vladislav A., Scherz, Mark D., Korost, Dmitriy V. & Poyarkov, Nikolay A., 2021, Consequences of parallel miniaturisation in Microhylinae (Anura, Microhylidae), with the description of a new genus of diminutive South East Asian frogs, Zoosystematics and Evolution 97 (1), pp. 21-54 : 21

Microhyla Tschudi, 1838

Synonymy

(fide Frost 2020).

Microhyla Tschudi, 1838. Type species. " Hylaplesia achatina Boie, 1827" (nomen nudum) (= Microhyla achatina Tschudi, 1838), by monotypy.

Micrhyla Duméril & Bibron, 1841. Ex errore.

Siphneus Fitzinger, 1843. Type species: Engystoma ornatum Duméril & Bibron, 1841.

Dendromanes Gistel, 1848. Nomen substitutum for Microhyla Tschudi, 1838.

Diplopelma Günther, 1859. Nomen substitutum for Siphneus Fitzinger, 1843.

Scaptophryne Fitzinger, 1861 “1860.” Type species: Scaptophryne labyrinthica Fitzinger, 1861 “1860” (nomen nudum).

Copea Steindachner, 1864. Type species: Copea fulva Steindachner, 1864.

Ranina David, 1872 “1871”. Type species: Ranina symetrica David, 1871, by monotypy. Junior homonym of Ranina Lamarck, 1801.

Etymology.

The genus name is derived from the Greek μικρός (mikros), meaning “small,” and " Hylas " (for origin of this name see above).

Common name.

Narrow-mouthed Frogs.

Taxonomic content.

42 species: M. achatina Tschudi, 1838; M. aurantiventris Nguyen, Poyarkov, Nguyen, Nguyen, Tran, Gorin, Murphy & Nguyen, 2019; M. beilunensis Zhang, Fei, Ye, Wang, Wang & Jiang, 2018; M. berdmorei (Blyth, 1856); M. borneensis Parker, 1928; M. butleri Boulenger, 1900; M. chakrapanii Pillai, 1977; M. darevskii Poyarkov, Vassilieva, Orlov, Galoyan, Tran, Le, Kretova & Geissler, 2014; M. darreli Garg, Suyesh, Das, Jiang, Wijayathilaka, Amarasinghe, Alhadi, Vineeth, Aravind, Senevirathne, Meegaskumbura & Biju, 2019; M. eos Biju, Garg, Kamei & Maheswaran, 2019; M. fanjingshanensis Li, Zhang, Xu, Lv & Jiang, 2019; M. fissipes Boulenger, 1884; M. fodiens Poyarkov, Gorin, Zaw, Kretova, Gogoleva, Pawangkhanant & Che, 2019; M. gadjahmadai Atmaja, Hamidy, Arisuryanti, Matsui & Smith, 2018; M. heymonsi Vogt, 1911; M. irrawaddy Poyarkov, Gorin, Zaw, Kretova, Gogoleva, Pawangkhanant & Che, 2019; M. karunaratnei Fernando & Siriwardhane, 1996; M. kodial Vineeth, Radhakrishna, Godwin, Anwesha, Rajashekhar & Aravind, 2018; M. laterite Seshadri, Singal, Priti, Ravikanth, Vidisha, Saurabh, Pratik & Gururaja, 2016; M. malang Matsui, 2011; M. mantheyi Das, Yaakob & Sukumaran, 2007; M. mihintalei Wijayathilaka, Garg, Senevirathne, Karunarathna, Biju & Meegaskumbura, 2016; M. minuta Poyarkov, Vassilieva, Orlov, Galoyan, Tran, Le, Kretova & Geissler, 2014; M. mixtura Liu & Hu in Hu et al. 1966; M. mukhlesuri Hasan, Islam, Kuramoto, Kurabayashi & Sumida, 2014; M. mymensinghensis Hasan, Islam, Kuramoto, Kurabayashi & Sumida, 2014; M. nepenthicola Das & Haas, 2010; M. nilphamariensis Howlader, Nair, Gopalan & Merilä, 2015; M. okinavensis Stejneger, 1901; M. orientalis Matsui, Hamidy & Eto, 2013; M. ornata ( Duméril & Bibron, 1841); M. palmipes Boulenger, 1897; M. picta Schenkel, 1901; M. pineticola Poyarkov, Vassilieva, Orlov, Galoyan, Tran, Le, Kretova & Geissler, 2014; M. pulchra (Hallowell, 1861); M. rubra (Jerdon, 1854); M. sholigari Dutta & Ray, 2000; M. superciliaris Parker, 1928; M. taraiensis Khatiwada, Shu, Wang, Thapa, Wang & Jiang, 2017; M. tetrix Suwannapoom, Pawangkhanant, Gorin, Juthong & Poyarkov, 2020; M. zeylanica Parker & Osman-Hill, 1949; and, tentatively, M. maculifera Inger, 1989.

Revised diagnosis.

Microhyla s. str. differs from all other Microhylinae genera by the following combination of osteological characters: (1) frontoparietals generally separated from exoccipitals (partially fused in M. mukhlesuri , M. picta and Microhyla sp. 2); (2) exoccipitals separate; (3) neopalatines present (in M. berdmorei , M. butleri , M. minuta , M. orientalis , M. pineticola , M. superciliaris and M. tetrix ) or absent (in M. achatina , M. heymonsi , M. fissipes , M. malang , M. mukhlesuri , M. nepenthicola , M. nilphamariensis , M. okinavensis , M. picta , M. pulchra and Microhyla sp. 2); (4) sphenethmoids not fused to parasphenoid; (5) crista parotica ossified posteriorly; (6) otic ramus of squamosal poorly developed; (7) tympanic annulus well-developed (reduced in M. heymonsi , M. nepenthicola , M. nilphamariensis , M. orientalis , M. pineticola , M. superciliaris and M. tetrix ); (8) orientation of transverse processes of presacral vertebrae VI-VIII anterolateral, other vertebrae with inconsistent orientation; (9) clavicles absent; (10) omosternum absent (cartilaginous omosternum present only in M. pulchra ); (11) prehallux cartilaginous; (12) terminal phalanges of the longest fingers T-shaped (in M. achatina , M. berdmorei , M. butleri , M. fissipes , M. heymonsi , M. malang , M. minuta , M. nepenthicola , M. nilphamariensis and M. pineticola ), knobbed (in M. minuta , M. mukhlesuri , M. nilphamariensis , M. superciliaris and M. tetrix ), or simple (in M. okinavensis , M. orientalis , M. picta and M. pulchra ), terminal phalanges of the longest toe T-shaped (in M. achatina , M. berdmorei , M. butleri , M. heymonsi , M. malang , M. nepenthicola and M. pineticola ), knobbed (in M. minuta , M. mukhlesuri , M. nepenthicola , M. superciliaris and M. tetrix ), or simple (in M. fissipes , M. okinavensis , M. orientalis , M. picta , M. pulchra and Microhyla sp. 2). The combination of diagnostic external morphological characters includes: (13) body size medium to extremely miniaturized (adult SVL 12.8-45.8 mm); (14) snout rounded or pointed in profile; (15) supratympanic fold present; (16) ridge on posterior margins of choanae absent; (17) FI length greater than ½ FII; (18) discs present on every finger, only FII-FIV, or absent; (19) dorsomedial grooves on fingers present or absent; (20) toe discs present or absent; (21) dorsomedial grooves on toes present or absent; (22) two metatarsal tubercles (except M. maculifera with a single metatarsal tubercle); (23) dorsomedial line present or absent; (24) superciliary tubercles present ( M. palmipes and M. superciliaris ) or absent (all remaining species); (25) tibiotarsal articulation reaching well beyond snout (in M. berdmorei , M. darevskii , M. mantheyi and M. tetrix ) or less; (26) toe webbing from basal to developed to discs; (27) skin on dorsum from smooth to tubercular; (28) tympanum externally indistinct; (29) terrestrial or subfossorial microhabitat preference.

Phylogenetic definition.

The genus Microhyla s. str. includes all species that share a more recent common ancestor with Microhyla achatina than with Nanohyla annectens and Glyphoglossus molossus .

Distribution.

Frogs of the genus Microhyla are widely distributed across the East (southern China, including Taiwan and Hainan islands, and Ryukyu Archipelago of Japan), Southeast (Myanmar and Indochina, Malayan Peninsula, Sumatra, Java, Bali, and Borneo), and South Asia (Bangladesh, Nepal, Indian subcontinent to north-eastern Pakistan in the west and Sri Lanka in the south) (Fig. 1 ).

Taxonomic comment.

In the last phylogenetic revision of Microhyla , Gorin et al. (2020) included all species of the genus in their analysis, except M. darevskii , M. fusca Andersson, 1942, and M. maculifera . Microhyla darevskii was described from five formalin-fixed specimens and morphologically appears to be very close to the members of M. berdmorei species complex ( Poyarkov et al. 2014). Although the phylogenetic position of M. darevskii is not known, this species can be confidently assigned to the genus Microhyla s. str. based on morphological data. Microhyla fusca was described from a single specimen collected from southern Vietnam ( Andersson 1942), and was recently demonstrated to be a junior synonym of M. butleri ( Poyarkov et al. 2020a).

Microhyla maculifera remains the most enigmatic species of the group due to the lack of molecular data and uncertainties regarding morphological characters. This species was described from only two specimens ( Inger 1989), and no additional specimens have been reported since that time, despite numerous field survey efforts. This small-sized species is unique among its congeners in having comparatively short hindlimbs, large and wide head, less triangular than in other Microhyla , comparatively stout body habitus (Fig. 12 ), and a single metatarsal tubercle (vs two). Microhyla maculifera is different from the members of the genus Nanohyla gen. nov. by having FI longer than ½ of FII (vs FI shorter than ½ of FII or reduced to a nub), lack of discs on fingers and rudimentary discs on toes (vs digital discs well-developed), absence (vs presence) of dorsal median grooves on tips of fingers and toes, having comparatively short hindlimbs with tibiotarsal articulation reaching to snout (vs to well beyond snout), and toe webbing being basal (vs well-developed; Inger 1989). Due to the lack of molecular data, the phylogenetic position and generic placement of " Microhyla " Microhyla maculifera remains uncertain; we tentatively retain this species Microhyla s. str. pending data or future phylogenetic studies, which might suggest another arrangement.

Figures

Figure 1. Distribution ranges of the three clades of the Microhyla - Glyphoglossus assemblage. Distribution area of Microhyla I is shown in yellow, of Microhyla II in red, and of Glyphoglossus in blue. Distributional data from Gorin et al. (2020). Question mark denotes the unconfirmed record of " Microhyla annamensis " from Khao Sebab in eastern Thailand by Taylor (1962).

Figure 12. Holotype of Microhyla maculifera Inger, 1989 (FMNH 231271, adult male) in dorsal (A) and ventral (B) aspects. Scale bar denotes 5 mm. Field Museum of Natural History. FMNH 231271. Created by Field Museum of Natural History, Amphibian and Reptile Collection and licensed under CC-BY-SA 4.0.