Megophrys (Xenophrys) periosa, 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 : 59-63

Megophrys (Xenophrys) periosa sp. nov.

( Figures 22 & 23 ; Table 1)

Holotype. Adult male ( BNHS 6055 [field no. SDBDU 2009.793 ]: Figures 22 , & 23A & H), from Pangin town (28°12'33.96"N, 94°59'10.02"E, 450 m asl.), East Siang district , Arunachal Pradesh state, Northeast India, collected by members of the Systematics Lab, University of Delhi on 26 July 2009.

Paratypes. Four adult males ( BNHS 6057 [field no. SDBDU 2009.794 ]: Figure 23B ; BNHS 6058–6060 [field nos. SDBDU 2009.1170 – 1172 ]: Figure 23H ), collected along with the holotype by members of the Systematics Lab , University of Delhi on 26–28 July 2009 ; four adult males ( BNHS 6061 [field no. SDBDU 2009.1243 ]: Figure 23E ; BNHS 6062 [field no. SDBDU 2009.1244 ], BNHS 6063–6064 [field nos. SDBDU 2009.1265 – 1266 ]: Figure 23G ), and one adult female ( BNHS 6056 [field no. SDBDU 2009.1285 ]: Figure 23F ), from the Sessa River , nearby Sessa village (27°6'4.02"N, 92°31'38.52"E, 1110 m asl.), West Kameng district , Arunachal Pradesh state, Northeast India, collected by members of the Systematics Lab, University of Delhi on 07–09 August 2009 .

Referred specimens. Two adult males (SDBDU 2009.1189: Figure 23D ; SDBDU 2009.1190: Figure 23C ), from Rigo Village (28°9'34.56"N, 94°47'19.38"E, 260 m asl.), Along town, West Siang district, Arunachal Pradesh state, Northeast India, collected by Systematics Lab members on 30 July 2009; one adult male ( SDBDU 2009.1267 ), from the Sessa River , nearby Sessa village (27°6'4.02"N, 92°31'38.52"E, 1110 m asl.), West Kameng district , Arunachal Pradesh state, Northeast India, collected by members of the Systematics Lab, University of Delhi on 07–09 August 2009 .

Provisionally referred specimens (see Remarks). One juvenile male (SDBDU 2009.132), and two juvenile females (SDBDU 2009.133 & SDBDU 2009.134), from Pangkava ju (24°40'21.6"N, 94°28'19.86"E, 820 m asl.), Kangpat Khullen, Kamjong sub-division, Ukhrul district, Manipur state, Northeast India, collected by RGK and SDB on 21 May 2009; adult female ( CAS 232938 ––tissue only), from Hepu Stream (25°5'25.2"N, 96°24'13.2"E), Hepu village , Moe Nyin township, Myitkyina district, Kachin state, northern Myanmar, collected by G.O.U. Wogan, J.A. Wilkinson, J.V. Vindum, H. Win, T. Thin [“Additional collectors: K.S. Lwin, A.K. Shein and H. Tun ”] on 14 May 2003 .

Holotype description (measurements in mm). Mature male (SVL 93.8) ( Figures 22 , & 23A & H). Head moderately large, wider than long (HW 35.0, HL 33.6, IFE 15.5, IBE 25.3); snout bluntly pointed in dorsal view, obtusely protruding beyond mandible in lateral view, without rostral appendage ( Figure 22C ); loreal region acute, concave; canthus rostralis angular; dorsal surface of snout very slightly concave; eye diameter twice maximum diameter of visible portion of tympanum, and shorter than snout length (EL 10.7, TYD 5.4, SL 11.7); eyetympanum distance (TYE 8.2) less than twice diameter of visible portion of tympanum; tympanum oval-shaped, oblique ( Figure 22C ), with upper ~15% concealed by supratympanic ridge; pupil vertically elliptical; nostril positioned laterally, closer to eye than to snout (EN 5.2, NS 7.1); internarial distance greater than eyelid width, and equal to narrowest point between upper eyelids (IN 10.5, UEW 8.7, IUE 10.5); 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 ( Figures 22A & B , & 23A ), forearm moderately enlarged relative to upper forelimb, and shorter than hand length (FAL 20.6––left side; right side deformed; HAL 24.0); fingers long, narrow, without lateral fringes ( Figure 22D ), finger length formula IV<II<I<III (FIL 13.7, FIIL 10.9, FIIIL 15.5, FIVL 10.3); interdigital webbing, subarticular and supernumerary tubercles absent; thenar and outer metacarpal tubercles weakly developed; finger tips flattened, not expanded relative to digit width, and with subcircular pads, terminal grooves on pads absent. Hindlimbs long, thin ( Figures 22A & B , & 23A ); thighs equal to shanks, and longer than feet (TL 47.4, SHL 50.2, FOL 45.8); toes long, dorsoventrally flattened, without lateral fringes ( Figure 22E ), 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 rudimentary; inner metatarsal tubercles weakly defined, longitudinally ovalshaped; 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, weak granules; tympanum with borders raised relative to surrounding region; outer edge of upper eyelids with a broad pointed bump; supratympanic ridges narrow anteriorly, gradually expanding posterior to tympanum to become moderately enlarged, glandular, extending from orbit, 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 posteriorly from behind supratympanic ridges to ~90% distance to vent; parietoscapular-sacral ridges weakly developed, “>–<” configuration, composed primarily of single row 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, flat, level with axilla on chest; femoral glands medium sized, 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, sparse on tympanic regions between tympanum and eyes, on dorsal surfaces of body and upper posterior surface of flanks, increasing in density posteriorly, present along all dorsal ridges, absent from all remaining surfaces.

Colouration: In preservative ( Figure 22 ): Dorsal surfaces of body and head primarily greyish-brown; lightedged, darker brown triangular marking between eyes; parietoscapular-sacral and dorsolateral ridges narrowly bordered by dark brown; flanks grey, darker dorsally, tubercles on flanks primarily dark brown or black, many with small lighter tips; large dark brown blotch covers tympanic region, another extends from lower posterior border of orbits, additional dark brown bar extends vertically from lower orbital border to edge of upper lips; lateral surfaces of canthus rostralis black, front of snout dark brown; remaining surfaces of upper lips and area between dark blotches on lateral surfaces of head greyish-white; dorsal and lateral surfaces of forelimbs primarily light grey with large dark brown transverse blotches on forearms; dorsal surface of fingers with dark brown blotches; dorsal and lateral surfaces of hindlimbs brown with distinct dark brown transverse crossbars; throat, chest and anterior abdomen primarily brown with white-edged darker brown blotches and mottling; posterior half of abdomen and ventral surfaces of forelimbs and hindlimbs primarily creamish-white with dark brown blotches; ventral surfaces of 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 23A ): Dorsal surfaces of head, body and hindlimbs more olive-brown, distinctly paler on flanks and forelimbs; ventral surfaces generally lighter, with darker brown blotches distinct and revealing distinct wide brown longitudinal stripe on gular region; dark blotches on chest; ventral surfaces of limbs dark to light purple/mauve; distinct orange speckles present on dorsal and ventral surfaces, most noticeable on dorsal surfaces of toes and fingers and on flanks; iris very dark orange.

Refer to Figures 22 and 23A for further details of colouration and markings for holotype (in life, and in preservation).

Variation. Refer to Table 1 for morphometric variation within the type series and referred specimens, consisting of 12 adult males and one adult female. The paratypes and referred specimens generally resemble the holotype for most morphological characters with the following exceptions: Lateral fringes on toes typically absent, but some specimens have very narrow fringes on all toes; relative finger lengths vary between individuals, including IV<II<I<III for most specimens, but IV=II<I<III observed on three (SDBDU 2009.1189, BNHS 6061, BNHS 6064); posterior edge of tongue varies from weakly, to moderately bifurcated, likely due to varying fixation conditions; dorsolateral ridges vary from weak to moderately well developed, always extending>75% of the trunk length ( Figure 23 A–F); typically only upper border of tympanum is concealed by supratympanic ridge, though up to ~25% of tympanum appears to be concealed on some specimens; parietoscapular-sacral ridge configuration varies considerably amongst individuals, i.e., “>- (”, “>––<”, “> <”, “> |”, “>- <”, or only V-shaped parietoscapular ridge present; coverage of dermal asperities varies mostly in density between individual males in comparison with holotype, however, on some specimens both black (or brown) and white asperities were observed, may sparsely cover upper lips, loreal region, front of snout, posterior dorsal surface of upper eyelids, head, and dorsal surface of tibia-tarsus joints; asperities white on female, restricted to dorsal surface of body, sparse on middorsum, increasing in density posteriorly to above cloaca; outer metacarpal tubercles not visible on most specimens; tubercle cover on flanks varies considerably, some with only sparse scattering of small tubercles, others with moderately dense cover of heterogeneous (large to small) sized tubercles ( Figure 23 A–F). Dorsal and ventral markings vary considerably between individuals (see Figure 23 which represent extremes in variation).

Secondary sexual characters. Males: nuptial pads present, weakly raised, covered with brown/black microasperities on freshly collected specimens, 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 almost to base of distal phalange; external vocal sac indistinct; large internal vocal slits present on floor of mouth near rear of mandible, on each side; forearms enlarged relative to upper forelimbs. Female: mature ova without pigmented poles; nuptial pads, vocal sac, vocal slits, enlarged forearms, all absent.

Morphological comparison. Characters used for comparing Megophrys periosa sp. nov. with its congeners do not include those from the provisionally assigned referred specimens.

Megophrys periosa sp. nov. (adult males, N =12, adult female, N =1) differs from M. medogensis , M. zhangi and M. monticola by its larger adult body size, male SVL 71.3–93.8 mm, female SVL 112.0 mm (vs. male SVL 57.2–68.0 mm, N =17; male SVL 32.5–37.2 mm, N =3; male SVL 38.2–49.5 mm, N =17, female SVL 40.5–56.1 mm, N =6, respectively); differs from M. robusta by absence of black dermal asperities on posterior abdomen of adult males (vs. usually present), Finger II<I in length, N =13 (vs. Finger I=II, N =10); differs from Megophrys flavipunctata sp. nov., Megophrys oreocrypta sp. nov., M. major s.s. and M. mangshanensis by absence of distinct white, cream or light coloured stripe along upper lips (vs. present); further differs from Megophrys flavipunctata sp. nov. and M. mangshanensis by its larger adult body size, male SVL 71.3–93.8 mm, female SVL 112.0 mm (vs. male SVL 56.9–68.4 mm, N =4, female SVL 68.0– 74.6 mm, N =3; male SVL 62.5 mm, N =1, female SVL 73 mm, N =1, respectively); further from M. major s.s. by dark spots associated with flank tubercles typically present (vs. absent), toe tips not expanded relative to adjacent toe width (vs. expanded); differs from Megophrys himalayana sp. nov. by its typically larger adult body size, male SVL 71.3–93.8 mm, female SVL 112.0 mm (vs. male SVL 68.0– 73.5 mm, N =7, female SVL 83.9 mm, N =1), typically smaller eye diameter to snout length ratio for males, ED/ES 76.6–91.5%, mean 84.3 ± 4.2% (vs. ED/ES 87.6–101.1%, N =7, mean 94.2 ± 4.6%).

Systematic position. This taxon represents M. cf. major 4 (OTU 12) in the molecular analyses, and “ M. cf. major [5]” in Mahony et al. (2017).

Megophrys periosa sp. nov. consistently formed a sister taxa relationship with two populations found east of the Brahmaputra River in Manipur and Myanmar referred to herein as Megophrys cf. periosa ( M. cf. major 6/OTU 14 in molecular analyses). Uncorrected p -distances for the 16S rRNA gene between Megophrys periosa sp. nov. and M. cf. periosa was 1.6–2.0% (Appendix I, Table 6). The systematic position of this clade within the MMC was not fully resolved (see Systematic position section for Megophrys himalayana sp. nov. for further details), however most analyses placed this species as the sister taxon of Megophrys himalayana sp. nov. ( Figures 2 & 4 ; Appendix I, Table 3; Appendix II, Figures 1 , 2 & 5 ; Mahony et al. 2017). Refer to Appendix I, Table 6 for uncorrected p - distances for the 16S rRNA gene between Megophrys periosa sp. nov. and other MMSG species.

Etymology. The species epithet “ periosa ” is a Latinised Greek adjective meaning “immense”, in reference to the very large size that this species attains, even compared to otherwise generally large species in the MMC.

Suggested common name: Giant Himalayan Horned Frog.

Distribution. Megophrys periosa sp. nov. is so far confirmed from three localities in the state of Arunachal Pradesh, Northeast India. The currently known distribution ranges from East Siang district, west through West Siang district, to at least West Kameng district, between 260 and 1110 m asl. ( Figure 8A ). An improved and more extensive sampling is necessary to define the east-west limits of this species’ geographic range. Specimens assigned here to Megophrys cf. periosa were collected from Ukhrul district (at 820 m asl.), Manipur state, Northeast India, and from Myitkyina district, Kachin state, northern Myanmar ( Figure 8A ).

Habitat and natural history. All males were in breeding condition, and the female contained well-developed ova within her ovaries, indicative that the breeding season extends at least through late-July and early-August. All specimens were collected after dusk, typically perched on the rocky banks of small to large (1–15 m wide) moderately fast flowing mountain streams flowing through dense mature secondary/primary forest (e.g., Figure 9A & F ). Males spaced themselves along the banks of the streams at least 10 m apart. Vocalisations typically consisted of a succession of a few notes followed by an extended silence, but were rarely heard. Healed injuries were observed on two specimens; the right hand of the holotype appears to have been badly dislocated or broken ( Figure 22B & E ). This large mature male had noticeably less well-developed nuptial pads than the other males, possibly as a result of lower overall fitness, although it otherwise appeared to be in good health. One other specimen (BNHS 6064) had a large swelling on Finger II on the right hand, the cause for which is unclear.

Remarks. Specimens reported as M. lateralis and/or M. robusta by Borah and Bordoloi (2001), Bordoloi et al. (2000) and Sarkar and Ray (2006) from Arunachal Pradesh may apply to this species, and/or Megophrys himalayana sp. nov. The specimens reported in these studies should be re-examined to determine the correct identities. Populations provisionally assigned to this taxa (as M. cf. periosa ) from eastern Manipur state, Northeast India and northern Myanmar, were found to be the sister taxon to Megophrys periosa sp. nov. ( Mahony et al. 2017 [as M. cf. major [6]]; Figures 2 , 4 & 5 ). Regardless of BPP results indicating that this lineage may represent a distinct species-level taxon (Appendix I, Table 5), we recommend that comparable series of adult specimens be studied to further determine the taxonomic status of this lineage. For now, it may provisionally be regarded as conspecific with Megophrys periosa sp. nov.

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 22. Megophrys periosa sp. nov. holotype: adult male (BNHS 6055: SVL 93.8 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 23. Megophrys periosa sp. nov.: A. lateral view of adult male holotype (BNHS 6055: SVL 93.8 mm) in life. B. lateral view of adult male paratype (BNHS 6057: SVL 80.7 mm) in life. C–E. dorsolateral views of adult males in life showing typical variation: C. referred specimen (SDBDU 2009.1190: SVL 73.6 mm); D. referred specimen (SDBDU 2009.1189: SVL 71.3 mm); E. paratype (BNHS 6061: SVL 87.7 mm). F. dorsolateral view of adult female paratype (BNHS 6056: SVL 112.0 mm) in life. G. ventral view of two adult male paratypes immediately after euthanisation, showing variation of markings (left, BNHS 6064: SVL 88.8 mm; right BNHS 6063: SVL 81.3 mm). H. ventral view of three adult male specimens in preservation showing variation of makings (left, paratype BNHS 6059: SVL 81.9 mm; centre, paratype BNHS 6060: SVL 80.2 mm; right, holotype BNHS 6055: SVL 93.8 mm).