Megophrys (Xenophrys) oropedion Mahony, Teeling & Biju, 2013

Mahony, Stephen, Kamei, Rachunliu G., Teeling, Emma C. & Biju, S. D., 2020, Taxonomic review of the Asian Horned Frogs (Amphibia: Megophrys Kuhl & Van Hasselt) of Northeast India and Bangladesh previously misidentified as M. parva (Boulenger), with descriptions of three new species, Journal of Natural History 54 (1 - 4), pp. 119-194 : 163-166

Megophrys (Xenophrys) oropedion Mahony, Teeling & Biju, 2013

Megophrys oropedion Mahony, Teeling & Biju, 2013, p. 151 , In: Three new species of horned frogs, Megophrys ( Amphibia : Megophryidae ), from northeast India, with a resolution to the identity of Megophrys boettgeri populations reported from the region. Zootaxa, 3722 (2), 143 – 169.

Holotype. Adult male ( ZSI A 11601 [field tag SDBDU 2009.1000 ]) from ‘ Um Risa stream (25°33.644 ′ N 91°52.960 ′ E, 1520 m asl.), Malki Forest (on Shillong Peak), Shillong, East Khasi Hills district, Meghalaya state, northeast India ’, collected by Systematics Lab members on 18 May 2009 ( Mahony et al. 2013).

Paratypes. Three adult males ( ZSI A 11602 [field tag SDBDU 2009.1001 : Figure 12 (a)], BNHS 5595 [field tag SDBDU 2009.1002 ], BNHS 5596 [field tag SDBDU 2009.1003 ]), collected along with holotype; adult female ( ZSI A 11603 [field tag SDBDU 2009.1016 ]), from ‘ Um Risa stream (25°33.327 ′ N 91°53.099 ′ E, 1,600 m asl.), Malki Forest , Shillong, East Khasi Hills district, Meghalaya state, northeast India ’, collected by Systematics Lab members on 22 May 2009 ( Mahony et al. 2013) .

Originally referred specimens. Three adult males ( SDBDU 2009.300 [ Figure 12 (e,f)], SDBDU 2009.301 [ Figure 12 (e,f)], SDBDU 2009.1164 ) and one adult female ( SDBDU 2009.299 [ Figure 12 (b,e,f)]), from ‘ Mawphlang Sacred Forest (25°26.617 ′ N 91°44.767 ′ E, 1,810 m asl.), Mawphlang, East Khasi Hills district, Meghalaya state, northeast India ’, collected by Systematics Lab members on 30 May 2009 ( Mahony et al. 2013) .

Newly referred specimens. Subadult male ( SDBDU 2007.310 [ Figure 12 (d)]) from near the Inspection Bungalow (I.B.) Rest House (25.492778, 90.324167, 1115 m asl.), Nokrek National Park , Daribokgre , East Garo Hills district, Meghalaya state, NEI, collected by SDB and RGK on 9 October 2007; adult male ( BMNH [18]72.4.17J) from ‘ Darjeeling ’ [corrected here to Khasi Hills, Meghalaya state], NEI, collected by T .C. Jerdon ca. 1870; adult male paralectotype of Xenophrys monticola ( BMNH [18]53.8.12.52) ‘ Khasya ’ [= Khasi Hills], Meghalaya state, Northeast India, presented by Sir William Jackson Hooker ( BMNH Specimen Catalogue ), likely collected by his son Sir Joseph Dalton Hooker between June and September 1850 ( Hooker 1854) .

Morphological comparisons. Megophrys oropedion (adult males, N = 9; subadult male, N = 1; adult females, N = 2) differs from the following species that have not yet been assigned to a subgenus or species group through molecular analyses: from M. damrei and M. shuichengensis by much smaller adult size, male SVL 32.8 – 39.2 mm, female SVL 44.1 – 48.7 mm (vs. M. damrei : adult male SVL 47.7 – 57.1 mm, N = 7, adult female SVL 69.1 mm, N = 1 [Mahony 2011; Neang et al. 2013]; M. shuichengensis : adult male SVL 102.0 – 118.3 mm, N = 8, adult female SVL 99.8 – 115.6 mm, N = 7 [ Tian et al. 2000]); from M. feii by larger adult size, male SVL 32.8 – 39.2 mm, female SVL 44.1 – 48.7 mm (vs. adult male SVL 24.3 – 25.1 mm, N = 4, adult female SVL 28.2 – 28.9 mm, N = 2), lateral dermal fringes on toes absent (vs. present), and nuptial pads on fingers of males present (vs. absent) ( Yang et al. 2018).

Megophrys oropedion differs from M. parva s.s. by larger adult female size, SVL 44.1 – 48.7 mm (vs. female SVL 41.1 – 41.4 mm, N = 2), and fingertips not expanded relative to finger width (vs. fingertips noticeably expanded relative to finger width).

Megophrys oropedion differs from species molecularly assigned to the M. (X.) megacephala SG based on the following combinations of characters: from the following species by smaller adult male size, SVL 32.8 – 39.2 mm (vs. M. ancrae SVL 39.1 – 45.0 mm, N = 8; M. megacephala SVL 45.9 – 53.4 mm, N = 7), further from M. ancrae by HW ≥HL (vs. HL> HW), digit tips not expanded terminally (vs. digit tips distinctly expanded terminally), small, sharp horn-like tubercle absent on the eyelids (vs. present on most individuals), further from M. megacephala by considerably narrower head HW / SVL 32.7 – 39.4%, N = 12 (vs. HW / SVL 40.2 – 45.1%, N = 12).

Refer to the ‘ Morphological comparisons ’ sections of Megophrys dzukou sp. nov., Megophrys awuh sp. nov., Megophrys numhbumaeng sp. nov., M. serchhipii and M. zunhebotoensis for diagnostic characters.

Suggested common name. Since this species is currently endemic to Meghalaya state, and is the smallest species found there, we suggest the common name ‘ Little Meghalayan Horned Frog ’.

Distribution. Megophrys oropedion was originally described from three nearby populations, at Malki Forest and North East Hill University (NEHU), near Shillong town, and Mawphlang Sacred Forest, near Mawphlang village, all in the East Khasi Hills district (1410 – 1810 m asl.), Meghalaya state ( Mahony et al. 2013). Within the East Khasi Hills district, this species might also be found further south in the vicinity of Sohra (previously Cherrapunji) (see Remarks section below). This study has assigned a single specimen collected from Nokrek National Park (1115 m asl.) to this species, significantly increasing the geographic distribution ~ 140 km west into the East Garo Hills district of Meghalaya ( Figure 2 ). Megophrys oropedion is likely to be found elsewhere in the Garo Hills and Shillong Plateau above 1100 m asl.

Habitat and natural history. See Mahony et al. (2013) for habitat and natural history notes for the type series and originally referred specimens from the East Khasi Hills district , including bioacoustics analyses of advertisement calls, and possible conservation concerns . At Nokrek National Park , the single male specimen ( SVL 32.1 mm) was found near a hedge boundary of an abandoned vegetable garden below the IB Rest House . By October (the collection time), the (southwest) monsoons in NEI have generally significantly receded and most of the seasonal streams dry up and/or only have trickling water; there was a remnant of a small stream (~ 0.5 m wide) under the hedges of drying (wild and cultivated) vegetation where the specimen was collected . This specimen appears to have enlarged testes, however, other secondary sexual characters (nuptial pads, internal vocal sac slits, enlarged forearms relative to upper forelimbs) were not present indicating that this specimen was nearing sexual maturity at this size . The smallest known sexually mature male is the holotype ( ZSI A 11601) at SVL 32.8 mm .

Remarks. Refer to Mahony et al. (2013) for the holotype description, morphological variation within the type series and originally referred specimens, secondary sexual characters, and etymology of the species name. Mahony et al. (2013) discussed published reports attributable to this species under the name Megophrys monticola Kuhl and Van Hasselt (a synonym of M. montana Kuhl and Van Hasselt, 1822a by Pillai and Chanda 1979; Dutta 1997), Megophrys parva (by Chanda 1994, 1995, 2002; Dutta 1997), and more recently as Xenophrys cf. parva (by Mahony 2008; Das et al. 2010).

Deuti et al. (2017) provisionally assigned the paralectotype of Xenophrys monticola ( BMNH [18]53.8.12.52) to M . parva s.s. and redefined the collection locality as ‘ Cherrapunji ’ (currently Sohra), East Khasi Hills district , Meghalaya, India, assuming that the (presumed) collector, J .D. Hooker, might have collected the specimen from near his base camp. We consider this specimen to be morphologically conspecific with M. oropedion and provisionally consider this locality valid, but recognise that it must be confirmed by new collections from Sohra town or its vicinities. We also assign one historical specimen ( BMNH [18]72.4.17J) collected by T .C. Jerdon to M. oropedion . Though the jar label for this states ‘ Darjeeling ’ as the collection locality, we consider the specimen to have been collected from the Khasi Hills (see Taxonomic Accounts section above for further information) . Our molecular analyses confirmed M. oropedion to be also present in the West Garo Hills district based on a single specimen ( SDBDU 2007.310 [ Figure 12 (d)]). The three new specimens do not significantly expand the previously reported morphological variation within the species (see Mahony et al. 2013), except as follows: BMNH [18]53.8.12.52 has the finger length formula IV <I = II < III; SDBDU 2007.310 (like SDBDU 2009.299 ) does not have vomerine teeth — all other specimens do .

Kharkongor et al. (2018) recently reported M. oropedion based on a single specimen (ZSI V/ A/NERC-1217) from Umlyngka village , Upper Shillong (nearby the type locality). The authors also provided a list of other specimens from nearby the type locality which they referred to as M. parva . Based on the photographs of specimens provided ( Kharkongor et al. 2018, figs. 3 – 5), most (if not all) of these specimens appear to be referable to M. oropedion , currently the only small-sized Megophrys species found on the upper reaches of the Shillong Plateau .

Figures

Figure 2. Topographic distribution map of the Megophrys (X.) megacephala SG taxa: Left. All taxa from Northeast India and surrounding countries: diamonds represent type localities; circles represent referred localities based on examined specimens; circles with central dot represent identifications based on literature where sufficient evidence was available (see Remarks sections); Right. Inset rectangle enlarged to show the distributions of species from more densely sampled southern Nagaland and northern Manipur states, Northeast India. Blue lines represent major rivers; grey lines represent international borders.

Figure 12. Megophrys oropedion from Meghalaya state, India: (a). adult male paratype (ZSI A 11602: SVL 33.9 mm) in life from Malki Forest, East Khasi Hills district; (b). adult female referred specimen (SDBDU 2009.299: SVL 48.7 mm) in life from Mawphlang Sacred Forest, East Khasi Hills district; (c). adult male (not collected) in life from Malki Forest, East Khasi Hills district; (d). subadult male (SDBDU 2007.310: SVL 32.1 mm) in life from Daribokgre, East Garo Hills district; (e–f). two adult males (left— SDBDU 2009.301: SVL 39.2 mm; right—SDBDU 2009.300: SVL 35.0 mm) and adult female (centre— SDBDU 2009.299: SVL 48.7 mm) referred specimens in preservation (not to scale) showing variation, from Mawphlang Sacred Forest, East Khasi Hills district: (e). dorsal view; (f). ventral view.