Description
Philautus cornutus is a moderately sized bubble-nest frog with a snout-vent length range of 24.0 – 25.8 mm. The only known contemporary adult specimens are female. The snout is pointed in dorsal view and acute in profile. The canthus rostralis is sharply angular and straight to slightly concave. There is a distinct constriction immediately posterior to the naris. The loreal region is vertical and concave. The nostril is small, ovoid, oriented laterally and slightly posteriorly. A fleshy projection is on the rostrum of the individuals examined by Wostl et al. (2017). However, this character tends to be sexually dimorphic in Philautus and no males were examined. On the eyelids, there are several distinct conical tubercles and there is a row of conical tubercles along the ventral margin of the mandible. The pupil is horizontal. The tympanum is indistinct to barely discernable; but when the tympanum is visible the annulus is present. The supratympanic fold is straight to slightly curved and extends from the eye to just above the insertion of the forelimb. There is no lingual papilla and no vomerine teeth. The choanae are small and round to ovoid, separated by 5–7.5 times their greatest diameter. The tongue is bifurcate posteriorly and about half free (Wostl et al. 2017).

The arms are relatively long. On the hands, the palmar tubercle is oblong and partially to fully divided lengthwise; the thenar tubercle is ovoid. The subarticular tubercles are small and round and there is a small supernumerary tubercle present on the first phalanx of finger III or fingers III and IV. The pads of the finger are entire and slightly broadened to round. A fine dermal fringe is present on fingers II – IV, extending to the disk. There is very slight fleshy webbing between fingers III and IV. The relative finger lengths are I < II < IV < III (Wostl et al. 2017).

The legs are relatively long. The tarsus has a row of tubercles along the postaxial margin that extends to the first phalanx of toe V. There is no calcar, but the heel can have some very small rounded tubercles. There is a small patch of skin inferior to the vent with enlarged granules that extends to the ventral surface and laterally onto the posterior surface of the thigh. The ventral surface itself is granular, areolate on the throat. The musculus cutaneous pectoris is present and the pectoral septum is a broad sheet inserted across the breadth of the pectoral region. The plantar surface of the foot has numerous small tubercles and one enlarged tubercle at the base of metatarsal IV. The inner metatarsal tubercle is small and oblong. The subarticular tubercles of the toes are small and round. The proximal subarticular tubercle of toe IV is absent and the proximal subarticular tubercle of toe V is tiny. Supernumerary tubercles are present in any combination on the first phalanx of toes III – V. The toe pads are entire and round with a distinct ungual flap. There is a dermal fringe on toes II – V that extends to the disk. The relative toe lengths are I < II < III = V < IV. The webbing of the feet is reduced. Webbing formula is I(2) – (2.75 – 3)II(2 – 2+) – (3.5 – 3.75)III(2.5 – 2.75) – (4)IV(3.25 – 3.75) – (2 – 2.75)V (Wostl et al. 2017).

The dorsum is smooth with scattered round tubercles. The postorbital and suprascapular regions have a row of well-spaced enlarged conical tubercles that converge posteriorly to form a ‘‘V’’. The antecubital, thigh, and crus are tuberculate dorsally (Wostl et al. 2017).

This species is distinguished from all other Philautus on Sumatra by the extremely reduced pedal webbing with four phalanges of fourth toe free of webbing, relatively long limbs, and sharply angular canthus and snout. There is a distinct rostral tubercle in females. Philautus cornutus is most similar to P. refugii and P. thamyridion but can be differentiated by P. cornutus having a larger female size, lacking distinctive thigh patterning, and the above characteristics. More specific differences from P. thamyridion are that the focal species has a sharply angular canthus, vertical loreal region, and lacks enlarged tubercles in the interorbital region (Wostl et al. 2017).

In life, the dorsum is uniformly dark purple brown–light brown. Most individuals observed were patternless on the dorsum, but one (UTA-A 63819) had a dark forward pointing V originating at the sacral humps. The tubercles are lighter in color than the dorsum. There are usually thin dark bands on the antecubital, thigh, and crus. In most specimens, there is an indistinct light interorbital bar. All specimens have a distinctive black spot that surrounds the vent. The ventral surface is light brown with darker markings on the throat and chest. The undersides of the legs are marked with fuzzy-edged light flecks. The supratympanic fold is distinctly lighter and bordered inferiorly by a dark postorbital stripe. The iris is strongly bicolored, golden orange superiorly and inferiorly with dark brown wedges that extend from the anterior and posterior margins of the pupil to the margin of the eye. The palpebral membrane is mostly clear centrally with a thin band of pigmentation the color of the eyelid along the rim, fine speckling peripherally, and some patterning on the posterior portion that is continuous with that of the adjacent skin (Wostl et al. 2017).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Indonesia

View distribution map in BerkeleyMapper.

This species is known from Gunung Kerinci and Gunung Tujuh, Jambi Province, Sumatra at elevations above 1529 m asl. It has been collected as high as 1891 m asl. Though the upper elevational limit is unknown. All contemporary specimens are from mature forest (Wostl et al. 2017).

Life History, Abundance, Activity, and Special Behaviors
This species is known from only the type specimens, collected in before 1920, and five adult females collected in 2013. All contemporary specimens were collected at night on low vegetation in montane forests. Where it occurs, it is relatively common (Wostl et al. 2017).

Trends and Threats
Unknown. However, significant levels of deforestation have occurred on the lower slopes of the mountains where this species occurs.

Possible reasons for amphibian decline

General habitat alteration and loss
Habitat modification from deforestation, or logging related activities
Habitat fragmentation

Comments
The species authority is: Boulenger, G.A. (1920). “Reptiles and batrachians collected in Korinchi, West Sumatra, by Messers. H.C. Robinson and C. Boden Kloss.” Journal of the Federated Malay States Museums 8: 285–306.

This species is part of a monophyletic radiation of Philautus endemic to the island of Sumatra. Other species in the clade include P. amabilis, P. polymorphus, P. thamyridion, and P. ventrimaculatus. The sister relationship of this taxa remains unresolved (Wostl et al. 2017)

The original description of Philautus cornutus (Boulenger 1920) is probably derived from two species. The section “Color notes of a living example…” appears to be based on P. ventrimaculatus, a species that occurs sympatrically with P. cornutus (Wostl et al. 2017).

Philautus cornutus was originally assigned to the genus Ixalus by Boulenger (1920) but then moved to Philautus in 1923 by Van Kampen. However, the species was then moved to Rhacophorus by Ahl in 1931 before being moved back to Philautus by Bossuyt and Dubois in 2001 and supported by Hertwig et al. in 2012 (Wostl et al. 2017).

References

Wostl, E. Riyanto A., Hamidy, A., Kurniawan, N., Smith, E. N., Harvey, M. B. (2017). ''A Taxonomic Revision of the Philautus (Anura: Rhacophoridae) of Sumatra with the Description of Four New Species.'' Herpetological Monographs, 31, 70–113 .

Species Account Citation: AmphibiaWeb 2017 Philautus cornutus: Horned Bubble-nest Frog <https://amphibiaweb.org/species/4402> University of California, Berkeley, CA, USA. Accessed Apr 19, 2024.

Citation: AmphibiaWeb. 2024. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 19 Apr 2024.

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