Description

Platymantis macrosceles was originally described by Zweifel (1975), based on a single female specimen. It has since been redescribed along with two other specimens (Foufopoulos and Brown 2004). Platymantis macrosceles can be distinguished from other geographically proximate congeners by its bright yellowish-green to olive-green ground coloration with symmetric brown patches on the dorsum. The tip of the snout is slender and acutely pointed. There is a large tubercle on the snout tip. and another tubercle slightly anterior and medial to each nostril. Each eyelid also bears one or two prominent yellow tubercles, with one large tubercle located medially on the eyelid and sometimes a smaller one immediately posterior to it. White-tipped, enlarged tubercles are also present along the outer edge of the tarsi, particularly at the tibio-tarsal articulations. Pale yellow to bright white tubercles are present at the margin of the jaw. The skin is smooth but has low, white conical tubercles on the dorsum. There are also a pair of enlarged white tubercles on each side of the vent (Foufopoulos and Brown 2004).

The canthus rostralis is nearly straight over much of its length but curves abruptly anterior to the eye. The loreal region is deeply concave and nearly vertical. The snout is elongated and pointed. The pupil is horizontally elliptical. The tympanum is vertically oval and distinct but small. Vomerine teeth are in two groups medial and posterior to the internal nares. Relative finger lengths are as follows: 3>4>2>1. Relative lengths of the toes are 4>3>5>2>1. Toe discs are widely expanded but smaller than those on the fingers. Discs of the first and fifth toes are about one and one-half times the width of the penultimate phalanges. There is no webbing (Zweifel 1975; Foufopoulos and Brown 2004).

The dorsal body surfaces are bright yellowish-green to olive-green, with the head, central dorsal region of the body, and sacral region being the darkest green and the lateral portions of the head and limbs being the lightest yellow. Symmetric chestnut-brown patches are present on the dorsum, flanks, and tibia. The post-axial regions and humerus are bright yellow. There is a single dark supra-axillary spot, as well as clusters of darker melanic spots on the sacrum. The nares are darker and a faint canthal stripe runs from the eye to the naris. The labial region and scapular crests are bright yellow. Above the pupil, the iris is bright golden yellow; below the pupil, the iris is grayish-yellow. Hands and feet are dark green with pale yellow discs on the digit tips (Foufopoulos and Brown 2004).

Other members of this genus that also have large digital discs and are sympatric with Platymantis macrosceles are P. guppyi, P. neckeri, and P. nexipus. However, P. macrosceles can be distinguished from these species based on the following combination of characters: bright green and brown mottled dorsal coloration; small adult SVL (30 mm), prominent tubercles on eyelids and the tarsal segments of the hind limbs, long hind limbs (TL/SV, 0.589), unwebbed toes, internarial distance much less than distance from eye to naris (E-N/IN, 1.68), and a narrow head (HW/SV, 0.321) (Zweifel 1975; Foufopoulos and Brown 2004).

Distribution and Habitat

Country distribution from AmphibiaWeb's database: Papua New Guinea

View distribution map in BerkeleyMapper.

The exact type locality is unclear. The holotype was collected by E. J. Ford, Jr. at a locality recorded as Ti, Nakanai Mountains, West New Britain Province, Papua New Guinea, on July 29, 1956. However, this locality does not appear on maps, and the Nakanai Mountains are actually in central New Britain province. The elevation was apparently not recorded (Zweifel 1975).

Subsequently two more specimens were collected in the Nakanai Mountains, on the ridge between the Ivule and Sigole Rivers, at 900 m above sea level (Foufopoulos and Brown 2004). They were perched on mossy branches above a mountain stream on a steep slope.

Life History, Abundance, Activity, and Special Behaviors
This frog perches on mossy branches of shrub-layer vegetation near small montane streams, about 1 m above the ground. The coloration and skin texture are cryptic and mimic the mossy substrate (Foufopoulos and Brown 2004). The advertisement call is highly pulsed and amplitude-modulated, and has been described as a "krrrr...krrrr..." which sounds like a "moderately rapid vibration of wood on wood". Calls vary from short chirps with 2-4 pulses, to a long series of 15-20 pulses. Longer calls begin with an initially rapid burst of pulses, after which both pulse duration and interpulse interval steadily increase. During the first three pulses, the frequency climbs from 2.07 to 2.24 to 2.5-2.66 kHz, with dominant frequencies then remaining at 2.5-2.66 kHz. Two faint harmonics are present at 4.65 and 6.99 kHz (Foufopoulos and Brown 2004).

Platymantis macrosceles is rare but quite cryptic, and it is suspected that this species might be present in other New Britain, Papua New Guinea localities with similar habitat (Foufopoulos and Brown 2004).

Possible reasons for amphibian decline

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

References

Foufopoulos, J., and Brown, R. M. (2004). ''New frog of the genus Platymantis (Amphibia; Anura; Ranidae) from New Britain and redescription of the poorly known Platymantis macrosceles.'' Copeia, 2004(4), 825-841.

zweifel, R.G. (1975). ''Two new frogs of the genus Platymantis (Ranidae) from New Britain.'' American Museum Novitates, 2582, 1-7.

Species Account Citation: AmphibiaWeb 2021 Cornufer macrosceles <https://amphibiaweb.org/species/4902> University of California, Berkeley, CA, USA. Accessed Jan 24, 2025.

Citation: AmphibiaWeb. 2025. <https://amphibiaweb.org> University of California, Berkeley, CA, USA. Accessed 24 Jan 2025.

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