Megophrys megacephala, Mahony, Stephen, Sengupta, Saibal & Kamei, Rachunliu G., 2011

Mahony, Stephen, Sengupta, Saibal & Kamei, Rachunliu G., 2011, A new low altitude species of Megophrys Kuhl and van Hasselt (Amphibia: Megophryidae), from Assam, Northeast India, Zootaxa 3059, pp. 36-46 : 37-43

Megophrys megacephala sp. nov.

( Figs. 1–2 ; Table 1 )

Holotype. ZSI A 11213 , an adult male, from Basistha Road, approximately 5 km south of Basistha temple (26°03’59 N, 91°47’32 E, 145 m a.s.l.), East Khasi Hills, northern Meghalaya, India, collected 14 July 2009.

Paratypes. ZSI A 11214 , an adult male, locality as for holotype, collected on 15 July 2009; ZSI A 11321–ZSI A 11322 , two adult males, from Garbhanga Reserve Forest (25°55’– 26°06’ N, 91°36’– 91°47’ E), Kamrup district, Guwahati, Assam, India, collected on 2 May 2002; ZSI A 11323, an adult male, from Garbhanga Reserve Forest, collected on 24 April 2004; ZSI A 11324 , a sub-adult male, from Garbhanga Reserve Forest, collected on 10 June 2005; ZSI A 11326 an adult female, from Garbhanga Reserve Forest, collected on 16 July 2003.

Referred specimens. SDB 2009.698, an adult male, collected along with holotype; ZSI A 11325, an adult male, from Mayeng Hill Reserve Forest (25°49’– 25°55’ N, 91°21’– 91°29’ E), Kamrup district, Assam, India, collected on 23 June 2003.

Definition. This species is placed in the genus Megophrys s.l. through morphological exclusion from Brachytarsophrys and Ophryophryne as defined by Delorme et al. (2006). Megophrys megacephala differs from Ophryophryne based on the following characters: vomerine ridges present (vs. absent), HW:SVL 40.2–45.1% (vs. HW:SVL <25%) and pupil vertical (vs. horizontal); from Brachytarsophrys by projection of the snout beyond the jaw present (vs. absent), and fold of skin on the back of the skull absent (vs. present).

Megophrys megacephala is diagnosable from all other species currently referable to the genus Megophrys by the combination of the following characters: adult male SVL 45.9–53.4 mm N = 7, female SVL 64.4 mm N = 1, head relative to body size (HW:SVL 40.2–45.1%, HL:SVL 39.8–43.7%); tympanum exposed, slightly ovular, TYD:EL 52.9–82.4%; two circular, short stalk-like vomerine ridges with teeth, positioned between choanae, closer to choanae than each other; finger length formula IV<II<I<III, finger webbing absent; SHL:SVL 41.0–49.0%, FOL:SVL 34.0–45.3%, toe webbing rudimentary; subarticular tubercles and lateral fringes absent on all digits; non spinular nuptial pads present on fingers I and II of males; dorsal skin covered with dense granules and small to medium sized tubercles and ridges; outer surfaces of hind limbs and posterior dorsum with white asperities; palpebral horn absent; “X” marking on dorsum and white or yellow upper lip stripe absent; groin colouration of adult males greyish-white in life.

Comparisons. Megophrys megacephala is here compared with all 41 recognised mainland Asian species referable to the genus Megophrys ––details of congeners are provided in parentheses. It differs from M. boettgeri and M. wushanensis by larger adult male size, SVL 45.9–53.4 mm (vs. male SVL <38 mm), and lateral fringes on toes absent (vs. present); from M. kuatunensis and M. wuliangshanensis by larger adult male size, SVL 45.9–53.4 mm (vs. male SVL <32 mm), and wider head, HW:SVL 40.2–45.1% (vs. HW:SVL <37%); from M. binchuanensis and M. huangshanensis by larger adult male size, SVL 45.9–53.4 mm (vs. male SVL <36.0 mm; male SVL <42 mm, respectively), and wider head, HW:SVL 40.2–45.1% (vs. HW:SVL <34%); from M. minor and M. tuberogranulatus , by larger adult male size, SVL 45.9–53.4 mm (vs. male SVL <41 mm), wider head, HW:SVL 40.2– 45.1% (vs. HW:SVL <36%), and groin greyish-white on males (vs. red–orange on males); from M. pachyproctus and M. zhangi by larger adult male size, SVL 45.9–53.4 mm (vs. male SVL <37.5 mm), and wider head, HW:SVL 40.2–45.1% (vs. HW:SVL <37%); from M. baolongensis and M. wawuensis by larger adult male size, SVL 45.9– 53.4 mm (vs. male SVL ≤ 45 mm), wider head, HW:SVL 40.2–45.1% (vs. HW:SVL <36%), and TYD:EL 52.9– 82.4% (vs. TYD:EL <42%); M. brachykolos by larger adult male size, SVL 45.9–53.4 mm (vs. male SVL <40 mm), and basal subarticular tubercles on fingers absent (vs. present); from M. daweimontis and M. parva by larger adult size, male SVL 45.9–53.4 mm, female SVL 64.4 mm (vs. male SVL <37 mm, female SVL <46 mm; male SVL <44 mm, female SVL <54 mm, respectively), wider head, HW:SVL 40.2–45.1% (vs. HW:SVL 37.3% for holotype; HW:SVL <37 mm, respectively), and dorsum densely granular (vs. smooth to weakly granular); from M. zunhebotoensis by larger adult size, male SVL 45.9–53.4 mm, female SVL 64.4 mm (vs. male SVL 30 mm, female SVL 39 mm) and larger head proportions, HW:SVL 40.2–45.1%, HL:SVL 39.8–43.7% (vs. HW:SVL <34%, HL:SVL <36%); from M. serchhipii with unknown sex or maturity, by larger head proportions, HW:SVL 40.2– 45.1%, HL:SVL 39.8–43.7% (vs. HW:SVL 33.6%, HL:SVL 30.8%); from M. medogensis by smaller adult male size, SVL 45.9–53.4 mm (vs. male SVL 57.2–68.0 mm), shorter shank, SHL:SVL 41.0–49.0% (vs. SHL:SVL 55– 56%), shorter foot, FOL:SVL 34.0–45.3% (vs. FOL:SVL 49–50%), and “X” marking on dorsum absent (vs. present); from M. lekaguli by smaller adult male size, SVL 45.9–53.4 mm (vs. male SVL 56.6–68.1 mm), wider head, HW:SVL 40.2–45.1% (vs. HW:SVL <39%), and skin of dorsum densely granular (vs. smooth); from M. damrei by dorsum densely granular with small to medium sized tubercles and ridges (vs. smooth), and outer surfaces of hind limbs and posterior dorsum with white asperities (vs. asperities absent); from M. takensis by larger head proportions, HW:SVL 40.2–45.1%, HL:SVL 39.7–43.7% (vs. HW:SVL 33.9–38.3%, HL:SVL 31.4–36%), and vomerine ridges form short rounded stalks, choanae clearly visible when viewed from inside the mouth (vs. vomerine ridges form elongated stalks blocking the view of choanae); from M. binlingensis by larger head proportions, HW:SVL 40.2–45.1%, HL:SVL 39.8–43.7% (vs. HW:SVL 33.3–34.6%, HL:SVL 32.3–33.5%), and vomerine teeth present (vs. absent); from M. major and M. mangshanensis by smaller adult male size, SVL 45.9–53.4 mm (vs. male SVL> 60 mm), and white or yellow upper lip stripe absent (vs. present); from M. auralensis , M. glandulosa , and M. robusta by smaller adult male size, SVL 45.9–53.4 mm (vs. male SVL> 70 mm); from M. caudoprocta , M. jingdongensis , M. omeimontis , M. palpebralspinosa , M. shuichengensis , and M. spinata by possessing rudimentary webbing and lacking lateral fringes on the toes (vs. webbing ≥20% and lateral fringe on toes present); from M. gigantica , M. nankiangensis , and M. shapingensis by possessing a clearly visible tympanum (vs. tympanum covered by supratympanic fold); from M. aceras , M. longipes , M. montana , M. nasuta , and M. sangzhiensis by the absence of a distinct palpebral horn (vs. presence).

Holotype description. Mature male (SVL 51.5), body robust. Head large, wider than long (HW 22.6, HL 21.2, IFE 8.5, IBE 16.2). Snout rounded dorsally, laterally obtusely protruding beyond the mandible, without rostral appendage. Lores acute and slightly concave with well developed canthus rostralis, dorsal snout concave. Eye (EL 6.8) larger than tympanum ( TYD 3.7) and shorter than snout (SL 7.0). Eye-tympanum distance (TYE 4.0) slightly longer than tympanum diameter. Tympanum distinctly oval, obliquely orientated with the upper ~5 % concealed by the supratympanic ridge. Pupil indistinct (vertical in life). Nostril positioned laterally, oval, horizontal with a raised rim posteriorly, positioned midway between eye and snout (EN 3.6, SN 3.6). Internarial distance (IN 5.5) narrower than the narrowest point of the frontal (IUE 6.1), which is subequal to eyelid width (UEW 6.0). Pineal ocellus absent. Vomerine ridges of medium size, rounded, conical, with small vomerine teeth, vomerine ridges closer to choanae than each other, positioned between choanae. Tongue long and narrow, without notch posteriorly and no medial lingual process. Supratympanic fold narrow with minimal widening posteriorly, extends from the orbit and curves down along the upper and posterior border of the tympanum terminating above the shoulder.

Forelimbs moderately long and thin, forearm (FAL 13.8) slightly enlarged relative to the upper arm, slightly longer than hand length ( HAL 13.2). Fingers long and narrow, finger length formula IV<II<I<III (FIL 7.7, FIIL 6.2, FIIIL 10.0, FIVL 5.7). Interdigital webbing, lateral fringes, subarticular and supernumerary tubercles absent, prepollex barely distinguishable, palmar tubercles absent. Digit tips slightly expanded and rounded without discs or terminal grooves. Hind limbs short and thin, tibia do not meet when legs are held at right angles to the body, thigh length (TL 22.9) slightly longer than tibia length (SHL 22.2), longer than the foot (FOL 21.0). Toes long and thin, relative toe lengths I<II<V<III<IV. Digit tips slightly dilated and flattened but without discs, base of digits with a thick rudimentary webbing: distinct lateral fringes, outer metatarsal tubercle, subarticular and supernumerary tubercles all absent. Inner metatarsal tubercle indistinct and ridge of thickened skin on the ventral surface of digits absent.

Skin on dorsal and lateral surfaces of the head, body and dorsal thighs granular. Posterior back and flanks scattered with numerous small to medium sized granules and tubercles. Throat, ventral surface of body and limbs smooth. Dorsal surface of upper and lower arm, shank and tarsus with small, sparsely distributed tubercles. Posterior thigh and cloacal region finely granular. Tympanum skin smooth, borders slightly raised. Palpebral horn absent, replaced by a short, raised fleshy ridge. Dorsolateral folds absent. A fine “V” shaped parietoscapular ridge present extending posteriorly from the temporal region level with the anterior tympanum edge, with posterior apex slightly beyond the level of the insertion of the forelimbs. On middorsum an additional raised “W” shaped ridge is distinct. Pectoral glands small and flat, on right side barely distinguishable, positioned on the chest at the level of the axilla, femoral glands distinctly raised, positioned closer to knee than to cloaca. Small white asperities speckled around vent region, ventral and posterior thighs, few on dorsal tibia and proximal tarsus, broadly scattered on posterior back and flanks mostly restricted to tubercle tips, but absent on the lower jaw. Abdomen weakly granular, ventral and posterior thigh and cloacal region with small tubercles.

Colouration of holotype. In preservation ( Fig. 1 ): Dorsal and lateral head, body and limbs primarily plain greybrown, darkest dorsally, gradually becoming lighter on the flanks and limbs. A solid dark brown triangular marking between the eyes. Enlarged flank tubercles present with light centres, bordered below by dark brown spot. Lateral surfaces of the snout anterior to the orbit dark brown, and a wide oblique dark brown bar below the eye. Supratympanic fold white, bordered below by a thin dark brown line. Gular region and chest pale grey-brown with light blotches along the edges of the lower mandible, a short brown bar on both sides of the throat and a longitudinal bar from mid gular to the anterior chest. Pale grey-brown of the chest fades to pale yellow on the posterior abdomen and thighs. Ventral shanks primarily light grey with darker brown mottling, outer tarsus with a continuous dark brown blotch from the heel fading posteriorly to grey on the ventral surface of the feet. Dorsal surface of the fore and hind limbs with faint dark cross bars. A brown patch surrounds the cloaca. Ventral surface of forelimbs and hands pale grey-yellow with dark brown blotches laterally. Pectoral and femoral glands white. In life ( Fig. 2 ): Colouration is as described above except that the overall dorsal colour is slightly more brown than grey.

Variation. Refer to table 1 for variation in the morphometrics amongst the type series and referred specimens. Four of the nine specimens have more distinct inner metatarsal tubercles. Parietoscapular and “W” shaped dorsal ridges are fragmented or absent on some specimens. A few specimens have short fragmented dorsolateral ridges anteriorly. White asperities may also be present on the outer surface of forelimb. Colouration and markings vary considerably, dark crossbars on hind limbs are more vivid on some and not visible on others, a dark brown “V” shaped patch surrounds the parietoscapular ridge on some specimens, but not visible on others. Ventrally, some have a dark brown throat and chest, diffusing to speckles on the anterior abdomen with remaining abdomen plain cream-yellow in preservation, whereas ventrally others are similar to the holotype but with faint brown marbling and blotches covering the abdomen.

Male secondary sexual characters. Two dark brown, smooth, oval nuptial pads, the largest on the middorsal surface of basal phalange of finger I, and a smaller pad on the inner dorsal surface of basal phalange of finger II. External vocal sac indistinct, and caudal projection above vent, absent.

Distribution, habitat and natural history. This species is currently known only from Garbhanga Reserve Forest and Mayeng Hill Reserve Forest, southern Kamrup District, Guwahati, Assam and adjacent forest in the East Khasi foothills of northern Meghalaya. It is likely that this species is more widespread along the northern foothills of Meghalaya and neighbouring low lying hills of Assam. The habitat in Garbhanga Reserve Forest consists of disturbed mature secondary forest containing mostly tropical moist deciduous, with some patches of tropical wet evergreen and tropical semi-evergreen forest ( Saikia et al. 2009). Specimens were mostly observed in moist leaf litter, occasionally in mesic vegetation and also on rocks along narrow cascade streams between 18:45 h to 22:30 h. A single male was found calling from a broad leaf of a sapling about 1 m above ground level. Gut contents from specimens of this species (including several paratypes) were composed primarily of insects of the order Isoptera and Hymenoptera.

Etymology. The specific epithet megacephala is derived from the Greek words mega (large) and kephal ē (head––using New Latin derivative–– cephala), referring to the large head proportions comparative to body size of this species relative to many congeners.

Suggested common name. Big Headed Horned Frog.

Figures

FIGURE 1. Holotype of Megophrys megacephala sp. nov. (ZSI A 11213) in preservation: A. dorsal view, B. ventral view, C. lateral view of head, D. ventral view of hand, E. ventral view of foot.

FIGURE 2. Holotype of Megophrys megacephala sp. nov. (ZSI A 11213) showing typical live colouration.

Tables

TABLE 1. Morphometric data for the type series and referred specimens of Megophrys megacephala sp. nov. Measurements in mm. H. holotype, P. paratype, RS. referred specimen, (ind). indistinct.

sex	ZSI A 11213 male	ZSI A 11214 male	SDB 2009.698 male	ZSI A 11325 male	ZSI A 11323 male	ZSI A 11322 male	ZSI A 11321 male	ZSI A 11324 male	ZSI A 11326 female
status SVL HW	H 51.5 22.6	P 49.8 21.3	RS 51.8 20.8	RS 45.9 20.7	P 48.4 21.2	P 53.4 22.0	P 49.1 20.9	P 34.1 15.1	P 64.4 28.7
HL IFE IBE EL TYD TYE	21.2 8.5 16.2 6.8 3.7 4.0	20.0 8.4 15.9 6.4 3.8 3.9	20.6 7.8 16.2 6.5 4 4.4	19.0 7.8 14.8 5.4 3.4 3.9	20.5 7.9 15.8 5.9 4.2 4.2	21.2 8.2 16.7 6.6 4.7 4.7	20.1 6.8 15.9 6.4 3.6 4.7	14.9 6.1 11.5 5.1 2.7 2.7	26.9 10.8 20.4 7.4 6.1 5.4
SL EN SN IUE IN UEW	7.0 3.6 3.6 6.1 5.5 6.0	6.6 3.1 3.2 5.7 5.6 5.7	6.9 3.5 3.5 5.5 4.9 6.2	7.0 3.8 3.1 5.4 5.3 5.3	7.1 3.7 3.7 5.6 5.6 5.9	7.1 3.7 3.6 5.2 6.1 6.3	6.8 3.3 3.6 5.4 5.5 5.8	4.8 2.1 2.2 4.0 3.8 4.5	8.3 3.9 3.8 8.4 7.5 6.5
FAL	13.8	12.6	13.1	13.9	12.6	14.3	12.3	9.8	17.6
HAL FIL FIIL FIIIL FIVL	13.2 7.7 6.2 10.0 5.7	13.3 7.1 6.1 9.2 5.5	13.4 6.8 5.5 9.2 4.9	13.8 7.5 5.6 8.4 5.2	12.4 6.3 4.7 7.5 4.3	14.1 7.7 6.0 8.5 5.3	13.7 7.5 6.1 8.6 4.9	9.4 5.8 5.1 7.5 4.4	14.9 7.9 6.8 8.8 5.2
SHL TL FOL IMT	22.2 22.9 21.0 (ind)	21.5 20.5 19.4 2.5	21.3 22.3 19.1 3.0	22.5 19.0 20.8 (ind)	21.4 22.1 18.8 3.3	21.9 22.2 21.5 3.1	21.9 21.8 19.9 (ind)	16.0 15.9 14.9 (ind)	27.0 28.0 24.1 (ind)