Amolops terraorchis, Saikia & Sinha & Laskar & Shabnam & Dinesh, 2022

Saikia, Bhaskar, Sinha, Bikramjit, Laskar, Mostaque A., Shabnam, A. & Dinesh, K. P., 2022, A new species of Amolops (Anura: Ranidae) representing the morphological ‘ Marmoratus species group’ from Sessa Orchid Sanctuary, Arunachal Pradesh, Northeast India, Records of the Zoological Survey of India 122 (3), pp. 303-322 : 310-312

Amolops terraorchis sp. nov.

(Sessa Cascade Frog)

Zoobank ID: urn:lsid:zoobank.org:act:FB8FD1E9-DC4A-49AA-B063-1B0021922725

( Figures 4, 5 , Table 2)

Holotype: V /A/ NERC/1702 , adult male ( Figures 4-5), collected by Bikramjit Sinha on 31 August, 2019 from Sessa River (27.1045 N, 92.5268 E, 1429 m; Figure 6 ), Sessa Orchid Sanctuary , Sessa, West Kameng, Arunachal Pradesh, India.

Paratypes: V /A/ NERC/1703 , adult male, and V /A/ NERC/1704 , adult female, collected along with the holotype; V /A/ NERC/1705 , adult male, and V /A/ NERC/1706 , adult female, collected by Bikramjit Sinha on 31 August, 2019 from an unnamed hill-stream, (27.0987N,

92.5273E, 1113 m), Eaglenest Wildlife Sanctuary , Sessa, West Kameng, Arunachal Pradesh, India .

Field diagnosis: Amolops terraorchis sp. nov. is a member of the morphological Marmoratus species group. The new species can be diagnosed based on the following set of morphological characters: adult male size medium (SVL 38.6-42.6 mm) and adult female size large (SVL

65.8-82.9 mm); head length wider than long; obtusely pointed snout; snout longer than eye length; inter-orbital distance equals upper eyelid width but smaller than inter-narial distance; tympanum distinct, about 40% of eye length; finger I disc slightly dilated, all discs with circum-marginal grooves; tibia longer than femur and foot, about 2/3 rd of SVL; tibio-tarsal articulation reaches beyond snout; no supra-tympanic fold; a discontinuous row of small glandular tubercles dorsolaterally.

Description of the Holotype: Adult male (SVL 38.6 mm), body slender, head wider than long, flat above; snout obtusely pointed, slightly protruding in lateral view, snout longer than the eye diameter; canthus rostralis distinct, loreal region concave; inter-orbital space flat, equals the width of the eyelid, but narrower than the inter-narial distance; nostrils laterally placed, nearer to the snout; pupil horizontal; tympanum distinct and circular, separated from the eye by a distance less than its diameter; pineal ocellus visible; a pair of vomerine teeth situated between the choanae; tongue slightly bilobed.

Arms thin, forearm length shorter than the hand length; fingers free, tips ending in the disc, the finger I disc slightly dilated, all discs with circum-marginal grooves, relative length of fingers I<II<IV<III; sub-articular tubercles prominent, circular; prepollex oval.

Hindlimbs long, tibia longer than both femur and foot; toes long and thin, tips of all toes dilated into discs with circum-marginal grooves, toes completely webbed; sub-articular tubercles domed shaped; inner metatarsal tubercle oval-shaped, outer absent.

Dorsal skin is smooth, and slightly granular towards the hinder and lateral sides; a discontinuous row of glandular tubercles present dorsolaterally from the posterior corner of the eye to the sacral region; no supra-tympanic fold; lateral skin is coarsely granular; ventral skin smooth.

Colouration of the Holotype: (in life) Dorsal colour dark brown, marbled with mustard green; laterally mottled with mustard green; ventral colour dirty white with maculated throat and chest. Limbs banded; dorsal thighs with alternating dark brown and mustard green bands ( Figure 4). In preservative same as in live condition except that all the mustard green colour is faded ( Figure 5 ).

Condition of the type series: All the types are in good condition. The ventral incision was made in all the type specimens to extract the liver tissue which was used in the molecular study. The female paratype V /A/ NERC/1704 was gravid .

Sexual dimorphism: Male much smaller than female. Male with internal vocal sac which opens near the throat. Female eggs ca. 1.3 mm in diameter. Disc in finger I in females is much more prominent than finger I in males.

Variations: Mensural differences are provided in Table 2. Paratypes agree with the holotype in overall morphological colourations and characters except in V /A/ NERC/1703 , where pineal ocellus is not visible .

Natural history: The individuals of Amolops terraorchis sp. nov. were collected after dusk hours from two different-sized torrential hill streams. The holotype and two paratypes were collected from the Sessa River ,

well within the boundary of Sessa Orchid Sanctuary and are characterized by the rapid flow of water amidst large-sized boulders and logs ( Figure 6 ). The other paratypes were collected from a small first order stream from another adjacent protected area, Eaglenest Wildlife Sanctuary, which also marks the boundary between the two protected areas. The vegetation is typical of moist evergreen forests with a wide variety of orchids as well as heavy growth of moss all around.

Distribution: Currently, this species is known from two protected landscapes of West Kameng district of Arunachal Pradesh, India – Sessa Orchid Sanctuary and Eaglenest Wildlife Sanctuary.

Comparisons: Based on phylogenetic analysis and morphological examination, Amolops terraorchis sp. nov. is a member of the Marmoratus species group. The new species is compared morphologically with the other species of the Marmoratus species group.

From the Indian Marmoratus species group, Amolops terraorchis sp. nov. differs from A. assamensis (in parentheses) in having adult male size smaller (vs. larger), supra-tympanic fold absent (vs. present), outer-metatarsal tubercle absent (vs. present); from A. gerbillus (in parentheses) in having head wider than long in males (vs. as long as broad in males), nostril nearer to snout tip (vs. nearer to eye), males with small gular pouch (vs. distinct and large gular pouch); from A. indoburmanensis (in parentheses) in having smaller adult male size (vs. large), supra-tympanic fold absent (vs. present), outer-metatarsal tubercles absent (vs. present), dorsum dark brown, marbled with mustard green (vs. brown with scattered darker brown spots); from A. jaunsari (in parentheses) in having head wider than long (vs. equal), IN>IUE (vs. IN=IUE), supra-tympanic fold absent (vs. present), finger I<II (vs. finger I=II), thighs banded (vs. blotched with reticulum), outer-metatarsal tubercle absent (vs. present), dorsum dark brown (vs. dark olive green); from A. senchalensis (in parentheses) in having nostril nearer to snout tip (vs. nearer to eye), toes entirely webbed (vs. nearly webbed), dorsum marbled in mustard green (vs. dark/black spots).

From the Marmoratus species group found outside India, Amolops terraorchis sp. nov. differs from A. afghanus (in parentheses) in having male size smaller (vs. larger); supra-tympanic fold absent (vs. short and thick), IUE=UEW (vs. IUE>UEW), dorsal skin slightly granular towards the hinder region (vs. smooth); from A. mahabharatensis (in parentheses) in not having dorsolateral glandular folds (vs. present), supra-tympanic fold absent (vs. present), IUE=UEW<IN (vs. IUE>UEW and IN), tongue slightly bilobed (vs. lanceolate), TTA reaching beyond snout (vs. up to snout), outer meta-tarsal tubercle absent (vs. weekly developed); from A. marmoratus sensu stricto (in parentheses) in having distinct tympanum (vs. indistinct), supra-tympanic fold absent (vs. short), slightly granular towards the hinder and lateral sides (vs. strongly granular), dorsum marbled with mustard green (vs. dark mottling), outer meta-tarsal tubercles absent (vs. present); from A. nepalicus (in parentheses) in having head wider than long (vs. longer than wide), IUE<IN (vs. (IUE>IN), Finger I<II (vs. Finger I=II); outer meta-tarsal tubercle absent (vs. indistinct); from A. panhai (in parentheses) in having female larger sized (vs. medium); head wider than long (vs. longer than wide), a gular pouch in males (vs. absent).

Etymology: The species epithet is derived from two Latin words – terra meaning ‘land’ and orchis meaning ‘orchid’,meaning ‘from the land of orchids.The name refers to the type collection locality of Sessa Orchid Sanctuary, which is the first such unique protected landscape in India, and most probably in the world, dedicated to the protection and conservation of the rich orchid diversity of the area. Interestingly, with an area of just 100 km 2, the Sessa Orchid Sanctuary harbours an incredible 149 species of orchids including 59 rare and five extremely rare species, with further scope of documenting much more species ( Tsering and Rinya, 2020).

Suggested Common Name: We suggest ‘Sessa cascade frog’ as a common English name for this species.

Figures

Figure 5. Holotype of Amolops terraorchis sp. nov. in preserved condition (A: dorsal view; B: ventral view).

Figure 6. Type locality of Amolops terraorchis sp. nov. from Sessa Orchid Sanctuary, West Kameng district, Arunachal Pradesh, India.