Megophrys (Xenophrys) oreocrypta, 2018

Mahony, Stephen, Kamei, Rachunliu G. & Teeling, Emma C., 2018, Cryptic diversity within the Megophrys major species group (Amphibia: Megophryidae) of the Asian Horned Frogs: Phylogenetic perspectives and a taxonomic revision of South Asian taxa, with descriptions of four new species, Zootaxa 4523 (1), pp. 1-96 : 50-54

Megophrys (Xenophrys) oreocrypta sp. nov.

( Figures 18 & 19 ; Table 1)

Holotype. One adult female ( BNHS 6045 [field no. SDBDU 2009.1108 ]: Figures 18 , & 19A & C), from Tura Peak Reserve Forest (25°30'29.4"N, 90°13'44.82"E, 640 m asl.), near Tura town , West Garo Hills district , Meghalaya state, Northeast India, collected by members of the Systematics Lab, University of Delhi on 20 June 2009.

Paratypes. Four unsexed juveniles ( BNHS 6046 – BNHS 6049 [field nos. SDBDU 2009.1104 – 1107 ]: Figure 19B, D, E & F ), collected along with the holotype .

Referred specimen. One unsexed juvenile (SDBDU 2008.1400; not measured), from Tura Peak Reserve Forest (25°30'40"N, 90°13'50"E, 510 m asl.), near Tura town, West Garo Hills district, Meghalaya state, Northeast India, collected by RGK on 13 May 2008; one juvenile (FMNH 74154 [previously ZSIC 18492]), from “Tura, Garo Hills, Assam ” (now West Garo Hills district, Meghalaya state), collected by S.W. Kemp, date unknown.

Holotype description (measurements in mm). Mature female (SVL 94.9) ( Figures 18 , & 19A & C). Head moderately large, slightly wider than long (HW 35.9, HL 35.7, IFE 16.2, IBE 25.6); snout bluntly pointed in dorsal view, obtusely protruding beyond mandible in lateral view, without rostral appendage ( Figure 18C ); loreal region acute, concave; canthus rostralis angular; dorsal surface of snout concave; eye diameter almost twice as long as maximum diameter of visible portion of tympanum, and shorter than length of snout (EL 9.0, TYD 4.7, SL 11.8); eye–tympanum distance (TYE 8.2) longer than diameter of visible portion of tympanum; tympanum oval-shaped, slightly oblique ( Figure 18C ), with upper ~15% concealed by supratympanic ridge; pupil in life vertically elliptical; nostril positioned laterally, closer to eye than to snout (EN 6.0, NS 6.5); internarial distance greater than eyelid width, and slightly less than narrowest point between upper eyelids (IN 9.3, UEW 8.4, IUE 9.6); pineal ocellus not visible externally; vomerine ridges medium sized, ovoid, moderately raised, positioned between to slightly posterior to choanae, equidistant from each other and choanae; vomerine teeth small; maxillary teeth present; tongue moderately large, medial lingual process absent, posterior edge not observed due to fixation of jaw and in interest of preventing potential damage to jaws by forcing open mouth wide enough for examination.

Forelimbs moderately long, thin ( Figures 18A & B , & 19A & C ), forearm not enlarged relative to upper forelimb, and shorter than hand length (FAL 21.5, HAL 23.3); fingers moderately long, narrow, without lateral fringes ( Figure 18D ), finger length formula IV<II<I<III (FIL 12.4, FIIL 10.7, FIIIL 15.4, FIVL 10.1); interdigital webbing, subarticular, supernumerary and metacarpal tubercles absent; thenar tubercles weak; finger tips rounded, slightly expanded relative to digit widths (FIIIW 1.8, FIIIDW 2.0), with subcircular pads, terminal grooves on pads absent. Hindlimbs long, thin ( Figures 18A & B , & 19A & C ); thighs shorter than shanks, longer than feet (TL 44.8, SHL 48.0, FOL 41.6); toes long, dorsoventrally flattened, without lateral fringes ( Figure 18E ), relative toe lengths I<II<V<III<IV; toe tips rounded, moderately expanded relative to digit width (TIVW 2.0, TIVDW 2.5) with distinct longitudinally oval-shaped pads, terminal grooves on pads absent; webbing basal, to distal edge of metatarsal on Toe IV (3III 2.5– 4IV 4.2–2.5V); inner metatarsal tubercle very weakly developed; subarticular, supernumerary and outer metatarsal tubercles absent; ridge of callous tissue absent on ventral surface of toes.

Skin of dorsal surfaces of body, limbs, and dorsal and lateral surfaces of head primarily smooth; tympanum smooth, slightly concave, with borders slightly raised; outer edge of upper eyelids with a weak medial bump; supratympanic ridges narrow anteriorly gradually expanding beyond posterior edge of tympanum to become moderately enlarged and glandular, extending from posterior edge of orbits, through upper portion of tympanum, curving down abruptly at posterior tympanum border, terminating above forelimb insertion; flanks weakly granular with medium to large scattered pustular tubercles; dorsolateral ridges thin, weakly defined, extending from behind supratympanic ridges, almost entire length of trunk; weakly developed V-shaped parietoscapular ridge present, sacral ridges absent; ventral surfaces of head, body and limbs smooth; pectoral glands small, weakly raised, positioned on chest at mid-level of forelimb insertion; femoral glands large, flat, on posterior surface of thighs, slightly closer to knees than to cloaca; dermal asperities absent from all surfaces.

Colouration: In preservative ( Figure 18 ): Dorsal and lateral surfaces of body, and dorsal surface of head primarily mid brown; light-edged, dark brown incomplete triangular marking between eyes; faint dark brown blotch on centre of dorsum; tubercles on flanks primarily creamish-white; lateral surfaces of head below supratympanic ridges and canthus rostralis dark brown with cream-white stripe on upper lip, extending from anterior to nostril to rear of jaw; dorsal and lateral surfaces of forelimbs and hindlimbs primarily brown; two or three dark brown blotches on dorsolateral surface of forearms; dorsal surface of fingers with dark brown blotches; dorsal surfaces of hindlimbs with faint transverse crossbars; throat pale brown with brown and creamish-white spots and blotches along edge of gular region, light-edged wide light brown stripe extending from posterior edge of mandible onto base of forearms; chest light brown; abdomen, ventral surfaces of forelimbs and thighs plain creamish-white, ventral surface of shanks grey; dark brown longitudinal stripe ventrolaterally on both sides of abdomen; area surrounding vent and posterior surfaces of thighs dark brown; ventral surfaces of tarsi and feet dark greyish-brown; hands ventrally pale greyish-brown; pectoral and femoral glands creamish-white. In life ( Figure 19A & C ): Dorsal surfaces of head, body and limbs orangish-brown; upper lip stripe pale greyish-brown, darker anteriorly, fading posteriorly; posterior flanks and groin region with yellow hue; ventral surface of throat and chest primarily pale grey with dark orange speckling, speckling more dense on lateral stripes of throat, and ventrolaterally on anterior abdomen; abdomen and ventral surfaces of thighs white.

Variation. See Table 1 for morphometric variation within the examined specimen series, consisting of an adult female, and five juveniles. All juveniles have head width less than head length; FMNH 74154 has finger length formula IV<I=II<III; posterior edge of tongue (examined on FMNH 74154 and BNHS 6046) distinctly bifurcate posteriorly; up to ~20% of upper portion of tympanum appears to be concealed by supratympanic ridge; dorsal surfaces of head and body of juveniles weakly granular; light upper lip stripe not visible on specimens smaller than SVL 41.0 mm (e.g., Figure 19E & F ); BNHS 6046 has distinct brown X-shaped marking on dorsum; BNHS 6046 and BNHS 6047 have small white asperities along dorsal ridges (e.g., Figure 19E ). See Figure 19C and 19D for ventral colouration variation between holotype and juvenile specimens.

Secondary sexual characters. Males currently unknown.

Morphological comparison. Megophrys oreocrypta sp. nov. (adult female, N =1) differs from M. monticola by its larger adult female body size, SVL 94.9 mm (vs. female SVL 40.5–56.1 mm, N =6); differs from M. robusta , M. medogensis and M. zhangi by absence of distinct dark brown vertical bar extending from lower orbital edge to edge of upper lip (vs. present) and presence of a distinctly lighter continuous upper lip stripe (vs. upper lip stripe absent). From other members of M. major species complex, it can be distinguished from Megophrys flavipunctata sp. nov. and M. mangshanensis by its larger adult female body size, SVL 94.9 mm (vs. female SVL 68.0– 74.6 mm, N =3; female SVL 73.0 mm, N =1, respectively), upper lip stripe extends anteriorly beyond nostril, N =4 [includes subadults] (vs. stripe terminates at, or posterior to nostril); differs from M. major s.s. by larger tympanum diameter/ eye diameter ratio, TYD/EL 52.2% (vs. female TYD/EL 40.0–41.2%, N =3), upper lip stripe extends anteriorly beyond nostril, N =4 [includes subadults] (vs. stripe terminates at, or posterior to nostril on all examined specimens, N= 15), pair of distinctly enlarged glands adjacent to cloaca absent, N =2 (vs. present, N =15).

Systematic position. This taxon represents M. cf. major 1 in the molecular analyses (discussed as OTU 7), and in Mahony et al. (2017).

The systematic position of Megophrys oreocrypta sp. nov. within the MMC clade is not fully resolved. It has consistently been found to be a member of the western clade of the MMC, and the sister taxon to M. major s.s. across all multigene analyses except the ML analysis of Dataset I (Appendix II, Figure 6 ), however, the relationship of this sister taxa clade with other members of the MMC is not clear when molecular data for the MMSG was subjected to a variety of phylogenetic techniques ( Figures 2–5 ; Appendix I, Table 3; Appendix II, Figures 1 , 2 , 5 & 6 ). Refer to Appendix I, Table 6 for uncorrected p -distances for the 16S rRNA gene between Megophrys oreocrypta sp. nov. and other MMSG species.

Etymology. The specific epithet “ oreocrypta ” is an adjective derived from the Latinised Greek words óros meaning “mountain” and kryptos meaning “hidden” or “secret”, in reference to the difficulty of finding adults of this species despite making several field trips to the Tura Peak Reserve Forest during 2008, 2009 and 2011.

Suggested common name: Garo White-lipped Horned Frog. Sangma and Saikia (2015) provide the local Garo (language) name “Diplok Nakma” for this species.

Distribution. Megophrys oreocrypta sp. nov. is currently known only from the southern slopes of the Tura Peak Reserve Forest (510–640 m asl.), in the West Garo Hills district of Meghalaya state ( Figure 8A ). Sangma and Saikia (2015) collected this species from slightly lower elevation on Tura Peak (437 m asl.) at Rengsangrap waterfall. It is likely that this species will be found throughout the adjoining Nokrek National Park and Biosphere Reserve, however its eastern distribution limits and altitudinal range are yet to be determined.

Habitat and natural history. The habitat at the collection locality for this species consisted primarily of tropical lowland forest. The adult female holotype was collected after dusk, from the banks of one of the major streams flowing west towards Tura town. Juveniles were all collected after sunset on forest trails within ~ 20 m from the nearest large stream. The biology of this species remains unknown; no adult males have been heard calling from streams that were surveyed and the ovaries of the holotype are empty. Sangma and Saikia (2015) reported observing two (or five, according to their table 1) individuals of this species (as Xenophrys glandulosa ) at the type locality, from among leaf litter and under moist rocks in the forest.

Remarks. A report of M. robusta by Dutta (1997) from the Garo Hills is presumably based on Megophrys oreocrypta sp. nov. (see “Remarks” for M. robusta ). Smith (1929) reported M. major from Tura possibly based on the specimen collected by W. Kemp (FMNH 74154 [originally ZSIC 18492]), which we herein verify to represent Megophrys oreocrypta sp. nov. Sangma and Saikia (2015) provided a photograph (plate 4a) of a preserved specimen collected from the type locality, Tura Peak, which they referred to as Megophrys glandulosa . This specimen appears to represent Megophrys oreocrypta sp. nov. based on the presence of a white upper lip stripe that clearly extends anteriorly beyond the nostril.

Figures

FIGURE 1. Ultrametric guide tree topologies used for BPP analyses: A. topology based on *BEAST analyses of phased nuclear alignments, with posterior probability values for nodes; B. alternative topology guide tree based on the results of concatenated mt+nuDNA gene tree analyses (Dataset E); C. alternative topology based on *BEAST analyses of unphased nuclear alignments, with posterior probability values for nodes. Taxon names in pink represent the eastern clade, blue represents the western clade (southern subclade), and green represents the western clade (northern subclade). Refer to Appendix I, Table 2 for revised names for taxa based on the taxonomic review.

FIGURE 2. BI concatenated gene tree based on the 47 taxa concatenated mt+nuDNA alignment (Dataset C), with ML node values provided. Posterior probability/bootstrap values>95% in both analyses are represented by a black spot on the node, values <95% in one or both analyses are provided next to relevant nodes, where * is>95%, and – is given for nodes that were not resolved on the ML tree. Taxon names in pink represent the eastern clade, blue represents the western clade (southern subclade), and green represents the western clade (northern subclade). Revised names for taxa based on the taxonomic review are provided in parentheses.

FIGURE 3. Concatenated gene trees based on the 29 taxa concatenated nuDNA alignment (Dataset D): A. RAxML tree; B. MrBayes tree. Posterior probability/bootstrap values are provided next to associated nodes. Taxon names in pink represent the eastern clade, blue represents the western clade (southern subclade), and green represents the western clade (northern subclade). Refer to Appendix I, Table 2 for revised names for taxa based on the taxonomic review.

FIGURE 4. RAxML tree for the combined mt+nuDNA dataset expanded to include the Chen et al. (2017) sequences (Dataset J). Bootstrap support values are provided adjacent to the associated nodes. Refer to Appendix I, Table 2 for revised names for taxa based on the taxonomic review.

FIGURE 5. DensiTree cloudogram representations of *BEAST analyses, removing the first 10% of trees as burn-in, produced from the four nuDNA gene alignments of Dataset E: A. original unphased; B. phased. Dark blue branches represent the most frequently occurring topology, light blue branches represent the consensus trees with intensity proportional to the frequency of the topology in the dataset, and green areas represent all topologies in the dataset. Refer to Appendix I, Table 2 for revised names for taxa based on the taxonomic review.

FIGURE 6. Megophrys monticola lectotype: adult female (BMNH 1947.2.25.13) in preservation: A. dorsal view; B. ventral view; C. profile view of head; D. ventral view of hand; E. ventral view of foot.

FIGURE 8. Distribution map of the western MMSG taxa: A. All taxa (excluding M. monticola) from Northeast India and surrounding countries: diamonds represent type localities, circles represent referred localities based on molecularly sampled specimens: orange = M. zhangi; yellow = M. robusta; black = M. medogensis; dark blue = M. major; pink = Megophrys flavipunctata sp. nov.; dark green = Megophrys oreocrypta sp. nov.; light blue = Megophrys himalayana sp. nov.; light green = Megophrys periosa sp. nov.; pale blue = M. cf. periosa; purple = M. glandulosa. B. Inset rectangle in Figure A enlarged to show the distribution map for M. monticola from Darjeeling and Sikkim region, Northeast India, showing distribution of named mitochondrial haplotypes: stars represent the type localities, circles represent referred localities confirmed from sequence data: red = M. “sanu” comb. nov., light blue = M. “katabhako” comb. nov. Blue lines represent major rivers; grey lines represent international borders.

FIGURE 18. Megophrys oreocrypta sp. nov. holotype: adult female (BNHS 6045: SVL 94.9 mm) in preservation: A. dorsal view; B. ventral view; C. profile view of head; D. ventral view of hand; E. ventral view of foot.

FIGURE 19. Megophrys oreocrypta sp. nov.: A. and C. holotype adult female (BNHS 6045: SVL 94.9 mm) immediately after euthanisation: A. dorsolateral view; C. ventral view. B. and D. juvenile paratype (BNHS 6046: SVL 41.7 mm) in life: B. front view; D. ventral view. E. and F. recently metamorphosed paratype (BNHS 6048: SVL 20.6 mm) in life: E. dorsolateral view; F. view of head showing absence of upper lip stripe.