Megophrys (Xenophrys) himalayana, 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 : 54-58

Megophrys (Xenophrys) himalayana sp. nov.

( Figures 20 & 21 ; Table 1)

Holotype. Adult male ( BNHS 6050 [field no. SDBDU 2009.1227 ]: Figures 20 , & 21A, F & H), from Elephant village (27°4'56.52"N, 92°34'50.22"E, 370 m asl.), West Kameng district , Arunachal Pradesh state, Northeast India, collected by members of the Systematics Lab, University of Delhi on either 0 4 or 0 5 August 2009.

Paratypes. Four adult males ( BNHS 6051–6054 [field nos. SDBDU 2009.1206 – 1209 ]: Figure 21C, D, F & H ), from Elephant village collected along with the holotype by members of the Systematics Lab, University of Delhi between 0 4 and 0 5 August 2009 .

Referred specimens. Adult male (SDBDU 2009.787: Figure 21E & G ), and adult female (SDBDU 2009.750: Figure 21B & G ), from Rengging village (28°8'32.52"N, 95°16'18.72"E, 410 m asl.), East Siang district, Arunachal Pradesh state, Northeast India, collected by Systematics Lab members between 24 and 25 July 2009.

Holotype description (measurements in mm). Mature male (SVL 72.1) ( Figures 20 , & 21A, F & H). Head moderately large, as wide as long (HW 27.0, HL 26.9, IFE 13.3, IBE 21.4); snout bluntly pointed in dorsal view, obtusely protruding beyond mandible in lateral view, without rostral appendage ( Figure 20C ); loreal region acute, concave; canthus rostralis angular; dorsal surface of snout very slightly concave; eye diameter more than twice maximum diameter of visible portion of tympanum, slightly shorter than snout length (EL 9.0, TYD 4.0, SL 9.6); eye–tympanum distance (TYE 5.8) approximately two times diameter of visible portion of tympanum; tympanum oval-shaped, oblique, with upper border concealed by supratympanic ridge ( Figure 20C ); pupil vertically elliptical; nostril positioned laterally, closer to eye than to snout tip (EN 4.0, NS 5.6); internarial distance greater than eyelid width and narrowest point between upper eyelids (IN 8.7, UEW 7.8, IUE 7.8); pineal ocellus not visible externally; vomerine ridge present, medium sized, ovoid, moderately raised, orientated acutely, positioned between to slightly posterior to choanae, equidistant from choanae and each other; vomerine teeth short; maxillary teeth present; tongue 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 long, thin ( Figure 20A & B ), forearm moderately enlarged relative to upper forelimb, and shorter than hand length (FAL 16.7, HAL 19.0); fingers long, narrow, without lateral fringes ( Figure 20D ), finger length formula IV<II<I<III (FIL 9.1, FIIL 8.7, FIIIL 12.2, FIVL 7.5); interdigital webbing, subarticular and supernumerary tubercles absent; thenar and outer metacarpal tubercles weakly developed; finger tips flattened, not expanded relative to digit widths, subcircular pads present, terminal grooves on pads absent. Hindlimbs long, thin ( Figure 20A & B ); thighs slightly shorter than shanks, and longer than feet (TL 36.7, SHL 37.5, FOL 33.1); toes long, rounded, not dorsoventrally flattened, without lateral fringes ( Figure 20E ), relative toe lengths I<II<V<III<IV; toe tips flattened, not dilated but with distinct oval-shaped pads, terminal grooves on pads absent; webbing basal; inner metatarsal tubercle weakly defined, longitudinally oval-shaped; subarticular, supernumerary and outer metatarsal tubercles absent; ridge of callous tissue absent on ventral surface of toes.

Skin of dorsal and lateral surfaces of head, body, and limbs primarily smooth, sparsely covered with small, weakly defined granules; tympanum with borders raised relative to surrounding region; outer edge of upper eyelids with a broad distinctly pointed bump; supratympanic ridges narrow anteriorly, gradually expanding beyond posterior edge of tympanum to become moderately enlarged and glandular, extending from orbits, curving downward abruptly at posterior upper border of tympanum, terminating above forelimb insertions; flanks sparsely covered with small to medium sized unevenly scattered pustular tubercles; dorsolateral ridges thin, weakly developed, extending from behind supratympanic ridges to ~95% trunk length; V-shaped parietoscapular ridge weakly developed, composed primarily of single rows of closely spaced asperities; dorsal surfaces of forearms, thighs and shanks with short transverse ridges; posterior thighs with small scattered pustular tubercles; gular region, chest, abdomen and ventral surfaces of limbs smooth; pectoral glands small, weakly raised, on chest level with axilla; femoral glands moderately large, flat, on posterior surface of thighs, slightly closer to knees than to cloaca; small white dermal asperities form broad dense band circummarginally on gular region, moderately dense on upper lips, tympanic region (except tympanum), supratympanic ridge and posterior dorsal surface of upper eyelids, sparse on posterior dorsal surface of head and anteriormost dorsum of body increasing in density posteriorly, present along all dorsal ridges, absent from all remaining surfaces.

Colouration: In preservative ( Figure 20 ): Dorsal and lateral surfaces of body, and dorsal surface of head primarily mid brown; light-edged, darker brown incomplete triangular marking between eyes; dorsum with distinct darker brown X-shaped marking on centre and dorsolateral longitudinal stripe on each side; tubercles on flanks primarily dark brown, many with small lighter tips; large dark brown blotch covers tympanic region; dark brown bar extends vertically from lower orbital border; lateral surfaces of canthus rostralis and front of snout dark brown; upper lip without contrasting light longitudinal stripe; dorsal and lateral surfaces of forelimbs and hindlimbs primarily mid brown; dark brown blotches on dorsolateral surface of forearms; dorsal surface of fingers with dark brown blotches; dorsal surfaces of thighs and shanks with distinct dark brown transverse crossbars; throat, chest and anterior abdomen primarily dark brown with darker brown blotches and mottling, throat with creamish-white spots and blotches along edge of mandible; posterior half of abdomen primarily creamish-white; ventral surfaces of forelimbs, thighs and shanks mid brown with lighter yellowish-brown mottling, ventral tarsi dark brown; area surrounding vent and posterior surfaces of thighs dark brown; ventral surfaces of feet and hands greyish-brown; pectoral and femoral glands creamish-white. In life ( Figure 21A & F ): Dorsal surfaces of head, body and hindlimbs orangish-brown, distinctly paler on flanks and forelimbs; ventral surfaces generally lighter, with brown blotches distinct, with distinct wide brown longitudinal striped on gular region; iris dark reddish-orange.

Variation. Refer to Table 1 for morphometric variation within the type series and referred specimens, consisting of six adult males and a female. Paratypes and referred specimens generally resemble the holotype for most morphological characters with the following exceptions: Head width/head length ratio varies considerably between individuals (HW/HL 94.3–106.3%); dorsolateral ridges typically weak to moderately well developed, always extending>65% of trunk length; posterior edge of tongue weakly bifurcate on three examined specimens (SDBDU 2009.750, BNHS 6051, BNHS 6053); typically only upper 10–25% of tympanum concealed by supratympanic ridge; parietoscapular-sacral ridges vary considerably in configuration, i.e., “>––<”, “> <”, “>– <”, or only V-shaped parietoscapular ridge present; coverage of dermal asperities varies mostly in density between individual males from Elephant Village, in comparison with holotype, however, male from Rengging Village (SDBDU 2009.787) has much less coverage of asperities, having white asperities mostly restricted to posterior dorsum and dorsal ridges; Rengging Village female (SDBDU 2009.750) has few white asperities on posterior dorsum and on dorsal surfaces of thighs; outer metacarpal tubercles not visible on some specimens; tubercle cover on flanks varies considerably, some with only sparse scattering of small tubercles, others with moderately dense cover of heterogeneous sized (large to small) tubercles ( Figure 21 A–E); dorsal and ventral markings vary considerably between individuals (see Figure 21 which represent extremes in variation).

Secondary sexual characters. Males: nuptial pads present, weakly raised, covered with black microasperities, covering most of dorsal surface of Finger I; nuptial pad on Finger II medium sized, oval, positioned on base of digit on inner dorsal side, extending onto base of proximal phalange; external vocal sac indistinct; moderately large internal vocal slits present on floor of mouth near rear of mandible on each side; forearms enlarged relative to upper forelimbs. Female: ova not pigmented; nuptial pads, vocal sac, vocal slits, enlarged forearms, all absent.

Morphological comparison. Megophrys himalayana sp. nov. (adult males, N =7, adult female, N =1) differs from M. monticola and M. zhangi by its larger adult body size, male SVL 68.0– 73.5 mm, female SVL 83.9 mm (vs. male SVL 38.2–49.5 mm, N =17, female SVL 40.5–56.1 mm, N =6; male SVL 32.5–37.2 mm, N =3, respectively); differs from M. robusta by its smaller adult male size, SVL 68.0– 73.5 mm (vs. male SVL 73.5–83.1 mm, N =6), black dermal asperities on ventral surface of thighs and posterior abdomen of males absent (vs. of six adult males examined, asperities present on ventral surface of thighs of all, and on abdomen of five); differs from M. medogensis by its slightly larger adult male body size, SVL 68.0– 73.5 mm (vs. male SVL 57.2–68.0 mm, N =16), iris colour in life maroon to red (vs. light golden [ Zhao et al. 2005; Li et al. 2010; Fei et al. 2010, 2012]). From MMC members, Megophrys himalayana sp. nov. differs from Megophrys flavipunctata sp. nov. by toes rounded, not flattened, lateral fringes absent (vs. toes dorsoventrally flattened, with or without narrow lateral dermal fringes), forearms of adult males moderately enlarged relative to upper arms (vs. not enlarged relative to upper arms); differs from Megophrys oreocrypta sp. nov. and M. major s.s. by dark spots associated with flank tubercles typically present (vs. absent), further from Megophrys oreocrypta sp. nov. by light portion of upper lip not extending beyond nostril (vs. light upper lip stripe extends anteriorly beyond nostril), further from M. major s.s. by webbing on Toe IV of males not extending beyond basal articulation, i.e., 4IV 4 (vs. webbing more extensive on males, i.e., 3.2IV3.2 to 3.6IV3.6), toe tips not expanded relative adjacent toe width (vs. expanded); from M. mangshanensis by larger adult body size, male SVL 68.0– 73.5 mm, female SVL 83.9 mm (vs. male SVL 62.5 mm, N =1, female SVL 73.0 mm, N =1). For comparisons with additional species covered in this study, refer to relevant morphological comparison sections.

Systematic position. This taxon represents M. cf. major 5 (OTU 13) in the molecular analyses, and “ M. cf. major [4]” in Mahony et al. (2017).

The systematic position of Megophrys himalayana sp. nov. within the MMC is currently unclear. Concatenated gene trees of mt+nuDNA or mtDNA only ( Figures 2 & 4 ; Appendix I, Table 3; Appendix II, Figures 1 , 2 & 5 ), and gene coalescence analysis of the unphased nuDNA-only dataset ( Figure 5A ; Appendix I, Table 3) placed this species as sister taxon to M. cf. major 4 (described as a new species, below), whereas, gene coalescence analysis of the phased nuDNA-only dataset ( Figure 5B ) placed this species as sister taxon to a clade comprising Megophrys flavipunctata sp. nov. and M. cf. major 4 (described as a new species, below). Refer to Appendix I, Table 6 for uncorrected p -distances for the 16S rRNA gene between Megophrys himalayana sp. nov. and other MMSG species.

Etymology. The species epithet “ himalayana ” is a toponym in reference to the known distribution range of this species that is restricted to the southern Himalayas.

Suggested common name: Himalayan Horned Frog.

Distribution. The type series and referred specimens were collected from two widely separated localities in the state of Arunachal Pradesh, indicating an Indian distribution that ranges at least from East Siang district, west to West Kameng district, at low elevation (375–410 m asl.) ( Figure 8A ). A more extensive sampling is necessary to define the east-west limits of this species’ geographic range.

Habitat and natural history. All specimens were collected after dusk. Animals were found typically perched on the rocky banks of small (~ 1–3 m wide), presumably temporary/seasonal, fast flowing mountain streams bordered by dense mature secondary/primary forest. This species probably favours smaller streams– –at the type locality specimens were collected from one of the small tributaries of the large Sessa stream ( Figure 9E ), but were not found on the banks of the Sessa stream itself. The two smallest male specimens, BNHS 6052 with no internal vocal slits and BNHS 6054 with very small internal vocal slits, had enlarged testes, well developed nuptial pads and enlarged forearms, indicating that males of this species begin reaching sexual maturity at around SVL 68.0– 68.5 mm. Although all males appeared to be in breeding condition, no vocalisations were heard at the collection localities. Furthermore, the female contained relatively under-developed ova in its ovaries indicative that the breeding season might begin sometime in late July or early August, towards the end of the monsoon season.

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 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 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 9. Habitat images for collection localities of MMSG species in Northeast India. A. Sessa River, near Sessa village (1110 m asl.), West Kameng dist., Arunachal Pradesh, collection locality of Megophrys robusta and Megophrys periosa sp. nov.; B. and D. Mawphlang Sacred Grove (~1810 m asl.), near Mawphlang village, East Khasi Hills dist., Meghalaya, type locality of Megophrys flavipunctata sp. nov.; C. Senchal Wildlife Sanctuary (2220 m asl.), Rambi (East Range), Darjeeling Sadar subdiv., Darjeeling dist., West Bengal, collection locality of M. monticola; E. Sessa River near Elephant village (370 m asl.), West Kameng dist., Arunachal Pradesh, off which smaller side streams were the type locality of Megophrys himalayana sp. nov.; F. stream near Pangin town (450 m asl.), East Siang dist., Arunachal Pradesh, type locality of Megophrys periosa sp. nov.

FIGURE 20. Megophrys himalayana sp. nov. holotype: adult male (BNHS 6050: SVL 72.1 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 21. Megophrys himalayana sp. nov.: A. dorsolateral view of adult male holotype (BNHS 6050: SVL 72.1 mm) in life; B. dorsolateral view of adult female referred specimen (SDBDU 2009.750: SVL 83.9 mm) in life; C–D. dorsolateral views of adult male paratype (BNHS 6051: SVL 70.2 mm) in life; E. dorsolateral view of adult male referred specimen (SDBDU 2009.787: SVL 70.2 mm) in life; F. ventral view of two adult males (left paratype BNHS 6051: SVL 70.2 mm; right holotype BNHS 6050: SVL 72.1 mm) immediately after euthanisation; G. ventral view of adult referred specimens in preservation, left male (SDBDU 2009.787: SVL 70.2 mm), right female (SDBDU 2009.750: SVL 83.9 mm); H. variation in ventral markings of adult male holotype and paratypes in preservation, clockwise from the top left specimen (BNHS 6050: SVL 72.1 mm; BNHS 6052: SVL 68.5 mm; BNHS 6054: SVL 68.0 mm; BNHS 6053: SVL 73.5 mm; BNHS 6051: SVL 70.2 mm).