Proc, Indian Acad. Sci., Vol. 87 B (Animal Sciences-Zj, No.6, June 1978, pp. 173-177, @ printed in India.

A new frog of the genus Micrixalus Boul. from Wynad, S. India

RS PILLAI Zoological Survey of India, Mylapore, Madras 600 004

MS received 11 October 1977; revised 25 January 1978

Abstract. Micrixalus nudis sp. nov. is described from Wynad, S. India and com­ pared with other known species of the genus from India and abroad. It is felt that the generic composition of the genus requires redefinition. A key to the Indian and Ceylonese species is given.

Keywords. Micrixalus nudis; generic composition.

1. Introduction

During the course of a survey of the amphibian wealth of Western Ghats, South India, the author collected several males and females of an undescribed species of Micrixalus (family: Ranidae) from Wynad Forest. Although collections were made from several stations commencing with Manantoddy in the north to Coonoor in the south, these forms were encountered only in a single locality.

2. Material

A total of 33 examples ofmales and females were collected from a forest brook, 8 kID north of Forest Rest House, Chedleth, Kurichiat Reserve Forest, Wynad, Coli. R. S. Pillai, 20 October 1976. Some were in amplexus. Family Ranidae Genus Micrixalus Boulenger Micrixalus nudis sp. nov. (figure 1)

3. Diagnosis

Small frogs with tympanum indistinct, dorso-lateral glandular folds and lingual papilla absent, digits with small discs bearing circum-marginal grooves, fingers free, toes three-fourths webbed.

4. Description

4.1. Head

Not depressed, about as broad as long, width at level oftympanum equal to distance

173 174 R S Pilla;

10 mm

Figure 1. Dorsal view of Micrixalus nudis Pillai, from posterior edge of tympanum to tip of snout. Snout subacuminate, as long as eye; canthus rostralis rounded; lores almost vertical, slightly concave; nostril lateral, half way between tip of snout and eye; inter-orbital space a little broader than upper eyelid; tympanum small, faintly visible through rim hidden by skin, its maximum diameter less than one-half of eye; pupil horizontally rounded; vomerines absent; omosternum not forked at base. Tongue free, bifid behind. A faint, tiny depres­ sion present on tongue at its median front part in some examples but lingual papilla absent.

4.2. Forelimbs Short and thin. Fingers free, tips dilated into small distinct round discs, that of third hardly one and half times width of penultimate phalanx, discs with circum­ marginal grooves. First finger shorter than second which in turn is as long as fourth; subarticular tubercles small; outer metacarpal tubercle cleft.

4.3. Hindlimbs Relatively short being It times the total length from tip of snout to vent; heels just touching when the limbs are folded at right angles to the body; tibio-tarsal arti­ culation of adpressed limb reaching eye (little more forwards in males). Tibia half of body length and 2! times as long as broad. Toes with discs slightly larger than that of fingers, with deep circum-marginal pocket-like grooves. No intercalary ossicle. Terminal phalanx with thin transverse expansion. Toes not fully webbed, web reaching discs on outer side of first, second and almost so on the third toes. Narrow fringes of web connecting discs in other places; membrane midway between third and fourth digits extending up to level of distal tubercle of third toe and that between fourth and fifth up to distal tubercle of fifth toe. Subarticular tubercles small; a small inner metatarsal tubercle present, no outer one other than a slightly thickened patch of skin. Outer metatarsal separated'by web for more than one­ half. No external fringe along free edges of first and fifth toes; no tarsal fold. A new frog ofthe genus Micrixalus Boul. 175

4.4. Skin

Smooth above and below with a few scattered tubercles on the upper side of tibia (see secondary sex characters). Dorso-lateral glandular folds absent, a weak supra­ tympanic fold from eye to shoulder. A row of two or three small silvery pustules between tympanum and insertion of arm.

4.5. Colour

Dorsum greyish brown or dark without markings. A band ofchocolate-brown from hind end of eye spreading out on to the flank through upper half of tympanum and arching above the arm like a vest. An anterior narrow extension preorbitally up to nostril. Arms with a few patches or bars, up to finger tips. Legs with dark cross bars dorsally. Throat and breast mottled and marbled with brown, often forming white spots. Rest of venter white (see secondary sex characters also).

4.6. Secondary sex characters

Dorsum in males darker in colour rendering the two dark bands less conspicuous. Texture of skin of dorsum and flanks coarsely granular with scattered granules in contrast to the smooth or only very finely shagreened skin of females. Vocal sacs internal, opening to the floor of the mouth by paired openings near the angle of jaws. A nuptial pad bearing unpigmented asperities present on the upper side offirst finger extending from wrist to base of disc. There is a very clear sex difference in body size also. The male of the pair in amplexus was always noticed to be smaller in size than the female. The largest male in the collection measures 16 mm in length from tip of snout to vent while the largest female measures 21 mm. Holotype An adult female frog, 21 mm in total length, loco Chedleth, Kurichiat Reserve Forest, Wynad, S. India, Altitude 825 metres, Coll. R. S. Pillai, 20 October 1976. Paratypes Two adult male (16 and 15 mm) and two adult female (20 mm each) frogs with data same as holotype. All type specimens are at present deposited with the Southern Regional Station, Zoological Survey of India, Madras.

4.7. Type-locality andfield notes

The type-locality of Micrixalus nudis is a small brook inside the Kurichiat Reserve Forest at Chedleth (Wynad), 20 km north of Sultans Battery on Pulpally Road and 8 km north of Forest Rest House at Chedleth. The brook was well shaded by the surrounding tall trees and flowed over a muddy bed, strewn with stones and boulders to join ultimately the Kabani River which is a tributary ofthe Cauvery. The frogs were collected from shallow water or from wet rock surface. They did not appear to be good at swimming away or hiding in the many crevices which the habitat provided abundantly in sharp contrast to Nyctibatrachus major Boul. which was also collected from the same place. They would go under water when disturbed only to reappear at the edge of water almost immediately afterwards. Some were attached to the vertical sides of boulders and were seen creeping along effortlessly. 176 R S Pillai

A few pairs in amplexus were observed suggesting the fag end of the breeding period which might coincide with the monsoon season.

5. Conclusions

Out ofthe 10 valid world species ofM icrixalus hitherto known, six are from India and one from Sri Lanka. Out of the six Indian species, five are from the Western Ghats of South India (Boulenger 1890; Myers 1942). These are M. saxicola (Jerdon), M. opisthorhodus (Gunther), M. fuscus (Boulenger), M. silvaticus (Boulenger) and M. herrei Myers. M. sarasinorum (Muller) is known from Ceylon. The following characters which these S. Indian and Ceylonese species exhibit would easily serve to distinguish them from M. nudis. M. saxicola-a free pointed lingual papilla, broadly webbed toes, the web reaching all discs which are larger. M. opisthorhodus-dorsolateral folds and lingual papilla. M. fuscus-dorsolateral folds and nearly entirely webbed feet. M. silvaticus-dorsolateral folds and much less webbing. M. herrei-dorsolateral folds, longer legs and more fused outer metatarsals. M. sarasinorum-full webbing, much larger discs and corrugated, warty skin. The other four species included in the genus are M. borealis from Arunachal Pradesh, N. E. India (Annandale 1912), M. torrentis from Siam (Smith 1923), M. baluensis (Oreobatrachus baluensis, Boulenger 1896, referred to Micrixalus by Inger 1954) from North Borneo and M. mariae from Philippines (Inger 1954). It may however be remarked that the webbed fingers in M. borealis, the distinct tympanum and outer metatarsal tubercle in M. torrentis, the forked omosternurn in M. baluensis and M. mariae and the presence of vomerines in the latter are all features that do not fit in well with Boulenger's generic description of Micrixalus. On the other hand, the six S. Indian and Ceylonese species, and M. nudis sp. nov. form a compact group which accommodates itself easily in the genus. Whether the latter group should alone be restricted to the genus or whether the former four species should also be included with suitable redefinition of the genus is a question to be settled only after the relations and affinities of Micrixalus vis-a-vis Hylorana, Staurois and Cornufer are clearly understood.

6. Key to the Indian and Ceylonese species of Micriulu.

1. Dorso-Iateral glandular folds absent 2 1. Dorso-Iateral glandular folds present 5 2. Papilla on tongue present 3 2. Papilla on tongue absent 4 3. Skin of dorsum and belly smooth saxicola 3. Skin of dorsum corrugated with warts, belly granular sarasinorum 4. Fingers free nudisn. sp. 4. Fingers with rudimentary webs borealis 5. Papilla on tongue present opisthorhodus 5.. Papilla on tongue absent 6 A new frog ofthe genus Micrixalus Boul. 177

6. Inter-orbital space as broad as or broader than upper eyelid 7 6. Inter-orbital space narrower than upper eyelid herrei 7. Toes at least three-fourths webbed fuscus 7. Toes less than half webbed silvaticus

Acknowledgement

The author is thankful to Drs. T N Ananthakrishnan and A G K Menon, for all facilities.

References

Annandale M 1912 Zoological results of the Abor Expedition, 1911-12. 1. Batrachla; Rec, Indian Mus. 87-36 Boulenger G A 1890 in Fauna ofBritish India including Ceylon and Burma: Reptilia and Batrachia (London: Taylor and Francis) Boulenger G A 1896 Descriptions of new batrachians in the British Museum; Ann. Mag. Nat. Hlst; 17401-406 Inger R F 1954Systematics and Zoogeography of Philippine Amphibia; Fieldiana Zool.33 185-525 Myers G S 1942 A new frog of the genus Micrixalus from Travancore; Proc. Biol, Soc. Wash. 55 71-74 Smith M A 1923On a collection of reptiles and batrachians from the Island of Hainan; J. Nat. Hist, Soc. Siam 6195·212