Megophrys (Xenophrys) awuh, Mahony & Kamei & Teeling & Biju, 2020

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 : 142-148

Megophrys (Xenophrys) awuh sp. nov.

Holotype. Adult male ( BNHS 6070 [field tag SDBDU 2007.163 ] [ Figure 5 ]) from Star Lake (25.464444, 94.703889, 2220 m asl.), Reguri village , Meluri circle, Phek district, Nagaland state, Northeast India, collected by RGK and VK on 5 July 2007.

Paratypes. Adult female ( BNHS 6069 [field tag SDBDU 2007.161 ]) and adult male ( BNHS 6071 [field tag SDBDU 2007.162 ]) collected along with holotype .

Referred specimens. Adult male ( SDBDU 2007.111 [ Figure 6 (a)]) from about 1 km from Dzükou tourist entry office (25.571667, 94.120278, ca. 1650 m asl.), off highway NH 39, Jakhama village, Kohima district, Nagaland state, NEI, collected by RGK and VK on 24 June 2007; adult male ( SDBDU 2007.079 [ Figure 6 (e – f)]) and adult female ( SDBDU 2007.080 [ Figure 6 (b – d)]) from the river Dzütsürü (25.613611, 93.969444, 2010 m asl.), Dzüleke village , Sechu-Zubza circle, Kohima district , Nagaland state, NEI, collected by RGK and VK on 18 June 2007; tissue sample without associated specimen ( SDBDU 2007.192 ) from Aradurah Forest , above New Ministers ’ Hill (25.641389, 94.094167, 1980 m asl.), Kohima town , Kohima Sadar circle, Kohima district , Nagaland state, NEI, collected by RGK and SDB on 10 July 2007 .

Holotype description (measurements in mm). Mature male ( SVL 37.2) ( Figure 5 ). Head moderately large, as long as wide ( HW 13.0, HL 13.0, IFE 6.3, IBE 10.3); snout bluntly pointed in dorsal view, obtusely protruding in lateral view, rostral appendage absent ( Figure 5 (c)); loreal region acute, concave; canthus rostralis angular; dorsal region of snout slightly concave; eye larger than maximum tympanum diameter, and equal to snout length ( EL 4.7, TYD 2.8, SL 4.7); eye – tympanum distance ( TYE 2.2) shorter than maximum tympanum diameter; tympanum distinctly oval shaped, upper border not concealed by supratympanic ridge; pupil oval in preservation, orientated vertically; nostril oval, orientated laterally, closer to eye than to snout ( EN 2.2, NS 2.6); internarial distance greater than eyelid width, and equal to narrowest point between upper eyelids ( IN 3.9, UEW 3.7, IUE 3.9); pineal ocellus not visible externally; vomerine ridges weak, forming long narrow ridges without swollen posterior end, orientated acutely, extending from near anterior choanae border, terminating posterior to choanae, posterior ends equidistant from each other and choanae; vomerine teeth absent; maxillary teeth present; tongue large, covers almost entire floor of mouth, cordiform (with weak notch posteriorly), no medial lingual process.

Forelimbs moderately long, thin ( Figure 5 (a – b)); forearms slightly enlarged relative to upper forelimbs, forearm shorter than hand length ( FAL 9.1, HAL 10.1); fingers moderately long, thin, lateral dermal fringes absent ( Figure 5 (d)), finger length formula I = II <IV < III ( FIL 4.0, FIIL 4.0, FIIIL 7.0, FIVL 4.2); interdigital webbing, and subarticular and supernumerary tubercles absent; thenar and outer metacarpal tubercles weak; fingertips rounded, not expanded relative to digit widths, with small oval pads, terminal grooves absent on fingertips. Hindlimbs long, thin ( Figure 5 (a – b)); thigh shorter than shank, and foot (TL 16.7, SHL 18.3, FOL 17.1); toes long, rounded, distinct lateral dermal fringes absent ( Figure 5 (e)), relative toe lengths I <II < V < III <IV; toe tips rounded, not dilated, with small circular pads, terminal groves absent on toe tips; webbing rudimentary; inner metatarsal tubercle indistinct; subarticular, supernumerary and outer metatarsal tubercles absent; ridge of callous tissue present on ventral surface of all toes.

Skin of dorsal surfaces of body, limbs, and dorsal and lateral surfaces of head smooth ( Figure 5 (a)); tympanum smooth with borders weakly raised; ridge or tubercle on outer edge of upper eyelids absent; supratympanic ridge narrow anteriorly, expanding posterior to tympanum to become moderately large and glandular, extending from orbit in a straight line to upper tympanum border, broadly curving obliquely downward along posterior border of tympanum, terminating above forearm insertion on each side; flanks with numerous small to large pustular tubercles ( Figure 5 (a)); dorsolateral ridges thick, well defined, extending from behind supratympanic ridge to above groin on each side; weak, ‘ X ’ -shaped ridge present on dorsum, its two sides extending posteriorly from above anterior border of tympanum and terminating beyond level of axilla on parietoscapular region, and posterior ends join to dorsolateral ridges on mid dorsum ( Figure 5 (a)); weak tubercles and short, obliquely transverse ridges present on dorsal surfaces of thighs, shanks and forearms. Gular region, chest, abdomen and ventral surfaces of limbs all smooth; pectoral glands medium-sized, flat, positioned on level of axilla ( Figure 5 (b)); femoral glands moderately large, slightly raised, positioned equidistant from knee and cloaca on posterior surface of thighs; black dermal asperities restricted to tympanic regions, posterior upper eyelids and posterior-lateral portion of head near supratympanic ridges, absent from all remaining surfaces.

Colour: In preservation ( Figure 5 ): Dorsal and lateral surfaces of head and body primarily light brownish-grey; solid dark brown triangular marking on dorsal surface of head between eyes; longitudinal brown stripe on mid-dorsal snout, extending from medial anterior border of triangular marking to tip of snout; dorsal ridges and flank tubercles light brownish-cream, some with small bordering dark brown spots and speckling; front of snout and lateral canthus rostralis dark brown; wide vertical dark brown bar below eyes; dark brown blotch extends from posterior canthus, through tympanum to posterior supratympanic ridge on each side; supratympanic ridges light yellowish-cream; dorsal surfaces of forelimbs and hindlimbs primarily light yellowish-grey; two dark brown blotches on anterior lateral surface of forearms; dorsal surface of outer three fingers with dark brown blotches; lateral surfaces of thighs and shanks with dark brown spots and blotches. Throat, chest and abdomen primarily pale grey, lightening to creamishyellow on lateral and posterior surfaces of abdomen and ventral surfaces of forelimbs, thighs and shanks; throat with faint dark brown longitudinal blotches, those most defined extending from rear axis of mandibles to base of forelimbs on each side, and third on midgular region extending onto anterior chest; dark brown blotches form broken stripe laterally along abdomen on both sides; area surrounding vent and posterior surfaces of thighs dark brown; ventral surfaces of tarsus and feet dark brown with contrasting light grey callous ridges on toes; light grey oval patch on region where inner metatarsal tubercle would be on other species; forelimbs and hands ventrally mottled creamishyellow and light greyish-brown, ventral surfaces of digits light grey; pectoral and femoral glands creamish-white. In life: No images in life taken for this specimen.

Variation. See Table 2 for morphometric variation within the specimen series of four adult males and two adult females. Paratypes and the referred specimen resemble the holotype for most morphological characters with some exceptions: finger length formula typically I = II <IV <III for four specimens, except for BNHS 6069 (I <II <IV <III) and SDBDU 2007.111 (I <II <IV <III); on SDBDU 2007.111, SDBDU 2007.079, and SDBDU 2007.080, vomerine ridges differ from type series by possessing small, weakly raised, hemispherical or ovoid posterior end of vomerine ridges, positioned between to slightly posterior to level of choanae; only SDBDU 2007.079 possesses small vomerine teeth, otherwise absent on all other specimens; posterior edge of tongue on SDBDU 2007.079 and SDBDU 2007.080 appears rounded rather than notched (which may be artefact of preservation); SDBDU 2007.079 and SDBDU 2007.080 ( Figure 6 (c,e)) have brown ‘ V ’ -shaped marking on anterior dorsum surrounding parietoscapular ridges; SDBDU 2007.111 possesses small tubercle on outer upper eyelid, SDBDU 2007.079 and SDBDU 2007.080 have short ridge on upper eyelid ( Figure 6 (a)); parietoscapular and dorsal ridge configuration differs from holotype as follows: SDBDU 2007.111 has faintly raised, longitudinal ‘>-<’ configuration ( Figure 6 (a)), SDBDU 2007.079 and SDBDU 2007.080 possess only ‘ V ’ -shaped parietoscapular ridges ( Figure 6 (c,e)); BNHS 6069, BNHS 6071 and SDBDU 2007.080 have no observed dermal asperities, SDBDU 2007.111 has white dermal asperities found only on middorsum, increasing in density posteriorly to above vent, on SDBDU 2007.079, asperities only found on posterior surface of upper eyelids; SDBDU 2007.111, SDBDU 2007.079 and SDBDU 2007.080 are mid to light brown dorsally; on BNHS 6069 and BNHS 6071, triangular brown marking on dorsal surface of the head is faint, ventrolateral dark brown blotches are smaller and less dense, and do not form broken stripe laterally along abdomen on both sides, and ventral shanks and thighs with dark brown, dense speckling; BNHS 6069 has small dark brown spots spread over entire abdomen.

Secondary sexual characters. Males: weakly raised nuptial pads covered with brown or black micro-asperities, covering most of dorsal surface of base of Finger I, narrowing distally, extending onto base of distal phalange on inner dorsal side; on Finger II, nuptial pad small, oval shaped, widest proximally, extending just onto basal phalange on inner dorsal side; external vocal sac indistinct; internal vocal slits present near rear of lower mandible; forearms slightly enlarged relative to upper forelimbs; fleshy projection above cloaca absent. Females: nuptial pads, vocal slits, cloacal projection all absent; forearms not enlarged relative to upper forelimbs; both females contained moderately large, pigmentless ova.

Morphological comparisons. Megophrys awuh sp. nov. (adult males, N = 4; 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 smaller adult size, male SVL 35.7 – 41.1 mm, female SVL 43.7 – 48.0 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 35.7 – 41.1 mm, female SVL 43.7 – 48.0 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 awuh sp. nov. differs from M. parva s.s. by larger tympanum relative to eye length, TYD/ED 55.8 – 72.7%, N = 6 (vs. TYD/ED 40.0 – 55.0%, N = 4), longer relative forearm length, FAL/SVL 24.5 – 26.3%, N = 6 (vs. FAL/SVL 20.9 – 23.9%, N = 4), longer relative shank length, SHL/SVL 49.2 – 54.9%, N = 6 (vs. SHL/SVL 42.8 – 48.2%, N = 4), fingertips not expanded relative to finger width (vs. slightly expanded relative to finger width).

Megophrys awuh sp. nov. differs from species molecularly assigned to the M. (X.) megacephala SG based on the following combinations of characters: differs from M. ancrae by finger and toe tips not expanded relative to digit width (vs. digit tips distinctly expanded terminally), small raised bump or short ridge on outer upper eyelids sometimes present (vs. short, sharp horn-like tubercle on outer upper eyelids present), circummarginal patch of demal asperities ventrally on mandible of males absent (vs. present on seven of eight males examined), and typically narrower snout, IFE/ HW 45.3 – 49.6 %, N = 6 (vs. 49.6 – 57.1%, N = 10); differs from M. megacephala by smaller adult male size, SVL 35.7 – 41.1 mm (vs. SVL 45.9 – 53.4 mm, N = 7), and considerably narrower head, HW/ SVL 31.5 – 36.7 %, N = 6 (vs. HW/ SVL 40.2 – 45.1 %, N = 12); differs from M. oropedion by slightly longer relative shank length, SHL/ SVL 49.2 – 54.9 %, N = 6 (vs. SHL/ SVL 41.1 – 48.4 %, N = 12), vomerine teeth usually absent, five of six specimens (vs. usually present, nine of 11 specimens examined), dermal asperities, if present, sparsely distributed, may be found on tympanic region, mid to posterior dorsum, and posterior upper eyelids (vs. extensively distributed on most dorsal, and some ventral surfaces of head, body and limbs); differs from M. serchhipii by FIIL≤FIVL (vs. FIVL<FIIL), dorsolateral ridges typically extending for entire trunk length (vs. absent, or short if present, extending <40% trunk length), tubercles and short ridges on dorsum absent (vs. present, typically extensive), and typically shorter FOL/SVL (mean±SD) 49.2 ± 3.1%, range 46.0 – 54.9%, N = 6 (vs. FOL/ SVL 44.3 ± 2.2%, range 39.5 – 48.7%, N = 32); differs from M. zunhebotoensis by larger adult male size, SVL 35.7 – 41.1 mm (vs. 28.4 – 33.9 mm, N = 22), typically larger tympanum diameter relative to eye diameter ratio, TYD/ED (mean±SD) 60.1 ± 2.8%, range 55.7 – 63.6%, N = 6 (vs. TYD/ ED 50.5 ± 3.9%, range 42.9 – 58.5%, N = 26), tympanum oval (vs. circular).

For a comparison with the two new species described below, see the comparison sections for those species.

Etymology. The specific epithet ‘awuh’ is treated as a noun in apposition taken from the Pochury language, meaning ‘ frog ’. The Pochury tribe are the native inhabitants of Meluri circle in Nagaland state, within which the type locality lies.

Suggested common name. We suggest ‘ Naga Hills Horned Frog ’ for this species based on its currently known distribution.

Distribution. Known only from the vicinity of Kohima and Star Lake in southern and eastern Nagaland state, respectively, at elevations between 1650 and 2220 m asl. ( Figure 2 ). Considering the wide elevational range inhabited, the geographic distribution of this species is expected to be more extensive than currently reported. The proximity of the collection localities relative to political borders indicates that Megophrys awuh sp. nov. will most likely be found in neighbouring Manipur state (NEI) and Sagaing Region (western Myanmar) at similar elevations.

Habitat and natural history. All males were calling when collected, and both females contained mature ova indicating that the breeding season includes at least the mid monsoon months of June and July. The type specimens were collected from a primary forest with lush undergrowth, patches of closed canopy, hill streams, and where there were not any significant signs of human activities except perhaps occasional and regulated hunting by the local Pochurys. All specimens were collected during daylight hours (12:00 – 16:00 h). The holotype was found calling from within grasses on the edge of a spring about a metre deep and three metres diameter; the male paratype was found calling beneath grasses half submerged in a puddle in the forest. The female paratype was collected from the edge of the same pond as the holotype. The referred specimen SDBDU 2007.111 was collected from ground level in secondary forest adjacent to highway NH 39 on a night with light rain, about 10 m away from a seasonal stream. SDBDU 2007.079 and SDBDU 2007.080 were collected at ~20:00 h from vegetation within 10 m of the river Dzütsürü in a mature secondary forest. The Aradurah Forest tissue sample was collected from a juvenile (SVL ~ 12 mm) caught on a rainy night at ~19:30 h on the ground under a bush. The bush was situated about four metres away from a seasonal hill stream. A few males were heard calling but possibly due to the moderately heavy rain the calls were not prolonged enough for the individuals to be located.

Remarks. Molecular phylogenetic analyses consistently resolved Megophrys awuh sp. nov. (adult male SVL 35.7 – 41.1 mm) as the sister taxon of the smaller M. zunhebotoensis (male SVL 28.4 – 33.9 mm) in all analyses that included mtDNA ( Figures 1 & S1 ; Mahony et al. 2017, figs. 1 & 3 [as ‘M. sp. [2 & 3] ’]; Mahony et al. 2018, fig. 4 [as ‘M. sp. 5 ’]). Molecular dating analyses suggested that these sister taxa diverged from their most recent common ancestor at ca. 3.8 MY ( Mahony et al. 2017, fig. 1).

Figures

Figure 1. ML phylogenetic tree of the subgenus Megophrys (Xenophrys) based on the concatenated mt +nuDNA alignment. Bootstrap values ≥95% are represented by a black spot; 80–95% represented by a grey spot; <80% not given. Numbers next to species names correspond with specimen numbers in Table 1.

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 5. Megophrys awuh sp. nov. adult male holotype (BNHS 6070: SVL 37.2 mm) in preservation, from Phek district, Nagaland state, India: (a). dorsal view; (b). ventral view; (c). profile view of head; (d). ventral view of hand; (e). ventral view of foot.

Figure 6. Megophrys awuh sp. nov. referred specimens from Kohima district, Nagaland state, India: (a). adult male (SDBDU 2007.111: SVL 35.7 mm) in life from Jakhama village; (b–f). specimens in preservation from Dzüleke village, showing variation: (b–d). adult female (SDBDU 2007.080: SVL 48.0 mm): (b). profile view of head; (c). dorsolateral view; (d). ventral view; (e–f). adult male (SDBDU 2007.079: SVL 41.1 mm): (e). dorsolateral view; (f). ventral view.