Oreophryne riyantoi Putri, Trilaksono, Kurniati, Engilis & Hamidy, 2023

Putri, Auni Ade, Trilaksono, Wahyu, Kurniati, Hellen, Hitch, Alan Thomas, Jr, Andrew Engilis, Widayati, Kanthi Arum, Farajallah, Achmad & Hamidy, Amir, 2023, A new high elevation species of Oreophryne Boettger (Anura: Microhylidae) from Sulawesi, Indonesia, Zootaxa 5353 (5), pp. 455-467 : 459-464

Oreophryne riyantoi Putri, Trilaksono, Kurniati, Engilis & Hamidy , sp. nov.

( Figs. 3 A−D, 4A−D)

Oreophryne sp1 .: Kurniati & Laksono 2021, pp. 30–31

Holotype: MZB Amph. 17494 (field number ATH 2794: Fig. 3 A−B, 4A−D), adult male . Paratype: An adult male and a juvenile, MZB Amph. 17493 (field number ATH 2792: Fig. 3 C−D) and MZB Amph. 17495 (field number ATH 2797 ), respectively. All specimens were collected by Wahyu Trilaksono on 20 November 2011, on Mount Mekongga, Mekongga Mountains, Wawo District , Kolaka Regency , Southeast Sulawesi (3.66267º S, 121.22067º E, 2528 m asl: Fig. 1 ) .

Diagnosis. The new species is assigned to the genus Oreophryne based on phylogenetic analysis. It can be distinguished from all congeners by the following combination of characters: snout rounded in dorsal and lateral view, tympanum indistinct, interorbital distance narrow (IOD/SVL 0.106–0.107), hands small (HAL/SVL 0.221–0.222), fingers and toes unwebbed, terminal discs on fingers and toes small (F3D/SVL 0.032–0.033, T4 D/SVL 0.031–0.032), legs very short (TL/SVL 0.318–0.322) and in life, dorsal surfaces of head, body and limbs irregularly tuberculated.

Description of the holotype. Measurements are given in Table 3 .Adult male 20.7 mm SVL ( Fig. 4 ). Head slightly wider than long (HL/HW 0.852, HL/SVL 0.320, HW/SVL 0.375); snout short (SL/SVL 0.094) rounded in dorsal and lateral view; canthus rostralis rounded; loreal region vertical, nearly flat; tympanum indistinct; nostrils directed laterally, closer to tip of snout than eye (SNL/SL 0.305, EN/SL 0.593); internarial distance more than half of interorbital distance (IND/IOD = 0.776, IND/SVL 0.083); interorbital distance much broadder than upper eyelid (UEW/IOD = 0.731, UEW/SVL 0.078, IOD/SVL 0.107); eye of moderate size (ED/SVL 0.091), pupil ovoid, oriented horizontally.

Fingers unwebbed, relative lengths III> IV> II> I; tips of fingers small, rounded, with faint terminal grooves; disc of first finger not expanded (F1D/SVL 0.019); discs on second and fourth fingers approximately as broad as of third finger (F3D/SVL 0.032), the third finger disc slightly wider than penultimate phalanges (phalanges 0.561, F3D/ phalanges 1.176). Toes unwebbed, relative lengths IV> III> V> II> I; tips of toes poorly developed, round discs with faint terminal grooves, slightly wider than penultimate phalanges (phalanges 0.594, T4D/phalanges 1.111); diameter of disc of first toe smaller than that of fourth (T1D/SVL 0.026, T4D/SVL 0.032); no subarticular tubercle; no metatarsal tubercle; hind limbs short (TL/SVL 0.318). Fingers and toes with lateral fringes extending to discs.

Dorsal surfaces of head, body and limbs irregularly tuberculated, ( Fig 3A–D ); supratympanic fold distinct; belly and gular region coarsely granulated, slightly wrinkled. Color in life dark grey, slightly lighter anteriorly; upper arms, dorsal surfaces of fingers and toes orange; indistinct W-shaped mark in scapular region; and mid-dorsal line from snout to vent continuous to the lateral posterior of femur, tibia, to fifth toes ( Figs. 3B–D ). In preservative, dorsally reddish brown; ventrally pale brown, gular region dusted with brown ( Fig. 4A–B ).

Variation. The adult holotype is morphometrically similar to the adult male paratype (morphometric measurements are given in Table 3 ). In preservative, dorsal skin of body in adult paratype and juvenile with prominent tubercles, less on limbs. Juvenile specimens with dark brown in dorsal, indistinct W-shaped in the scapular region, and a large white indistinct lumbar ocellus. Color in life of dorsal body in male paratype light yellow to brown; loreal region and beneath eye grey; mouth region with irregular light patches or mottling; tympanic regions beneath the tympanic fold bright yellow; a slightly curved dark bar between upper eyelids; upper surface of snout pale grey to yellowish; a large white defined ocellus in lumbar region ( Fig. 3C–D ).

Comparisons. In the following comparisons, we compared the new species only to male specimens of congeners. Oreophryne riyantoi sp. nov. is a morphologically distinct species that can be distinguished from all congeners in Sulawesi (morphometric measurements are given in Table 4 ) as follows: it is distinguished from O. variabilis in smaller body size, SVL 20.19–20.70 mm (vs. 23.14–26.85 mm); interorbital distance narrower, IOD/SVL 0.106 –0.107 (vs. 0.118 –0.141); snout rounded in dorsal view (vs. truncate with an obtusely angled tip); tympanum indistinct (vs. distinct); smaller hands, HAL/SVL 0.221 –0.222 (vs. 0.261 –0.292); smaller digital discs, F3D/SVL 0.032 –0.033, T4D/SVL 0.031 –0.032 (vs. 0.049 –0.057 and 0.041 –0.047); shorter hind limbs, TL/SVL 0.318 –0.322 (vs. 0.375 –0.443); in preservative, lower surfaces pale brown, gular region dusted with brown or less dense mottling (vs. uniform whitish, or greyish with yellow spots, or dark brown with yellow spots).

Oreophryne riyantoi sp. nov. differs from O. celebensis in having its head relatively shorter, HL/SVL 0.320– 3.222 (vs. 0.350–0.356); interorbital distance narrower, IOD/SVL 0.106–0.107 (vs. 0.131–0.165); eyes smaller, ED/ SVL 0.091–0.103 (vs 0.116–0.123); snout rounded in dorsal and lateral view (vs. truncate with an obtusely angled tip in dorsal, and protruding slightly in lateral view); snout shorter, SL/SVL 0.083–0.094 (vs. 0.110–0.127); tympanum indistinct (vs. distinct); shorter forearms, FAL/SVL 0.194–0.200 (vs. 0.256–0.262); much smaller hands, HAL/ SVL 0.221–0.222 (vs. 0.311–0.332); finger and toe discs small, F3D/SVL 0.032–0.033, T4 D/SVL 0.031–0.032 (vs. 0.056–0.076 and 0.052–0.058); foot shorter, FL/SVL 0.373– 0.381 (vs. 0.459–0.476); hind limbs shorter, TL/SVL 0.318–0.322 (vs. 0.476–0.513).

Oreophryne riyantoi sp. nov. differs from O. zimmeri in having interorbital distance narrower, IOD/SVL 0.106 – 0.107 (vs. 0.140); eyes smaller, ED/SVL 0.091 –0.103 (vs 0.132); snout rounded in dorsal and lateral view (vs. truncate with an obtusely angled tip in dorsal, and protruding slightly in lateral view); snout shorter, SL/SVL 0.083 –0.094 (vs. 0.119); shorter forearms, FAL/SVL 0.194 –0.200 (vs. 0.243); smaller hands, HAL/SVL 0.221 –0.222 (vs. 0.284); smaller finger discs, F3D/SVL 0.032 –0.033 (vs. 0.049); smaller foot, FL/SVL 0.373 – 0.381 (vs. 0.444); shorter hind limbs, TL/SVL 0.318 –0.322 (vs. 0.475); in life, dorsal surfaces of head, body and limbs irregularly tuberculated (vs. nearly smooth); absence of spots dorsally (vs. presence scattered black spots of irregular shape).

Among the Lesser Sunda species, Oreophryne riyantoi sp. nov. differs from O. jeffersoniana in having smaller toe discs, T4D/SVL 0.031 –0.032 (vs. 0.035 –0.040); smaller foot, FL/SVL 0.373 – 0.381 (vs 0.478 –0.512); shorter hind limbs, TL/SVL 0.318 –0.322 (vs. 0.486 –0.537); a dorsolateral line from eye to the groin absent (vs. only extending from the eye to more than half-way towards the groin). The new species differs from O. rookmaakeri Mertens 1927 by its indistinct tympanum (vs. distinct tympanum); smaller toe discs, T4D/SVL 0.031 –0.032 (vs. 0.040 – 0.047); smaller foot, FL/SVL 0.373 –0.381 (vs 0.404 –0.430); and shorter hind limbs, TL/SVL 0.318 –0.322 (vs. 0.412 –0.435). Also it differs from O. monticola ( Boulenger 1897) by its indistinct tympanum (vs. distinct); smaller toe discs, T4D/SVL 0.031 –0.032 (vs. 0.044 –0.046); and shorter hind limbs TL/SVL 0.32 (vs. 0.425 –0.448).

The unwebbed fingers and toes, together with very short hind limbs and poorly developed digital discs, clearly distinguish Oreophryne riyantoi sp. nov. from all Moluccan and Papuan Oreophryne except O. minuta Richards & Iskandar 2000 , O. alticola Zweifel, Cogger & Richards, 2005 , O. brevirostris Zweifel, Cogger & Richards, 2005 , O. geminus Zweifel, Cogger & Richards, 2005 , O. habbemensis Zweifel, Cogger & Richards, 2005 , and O. terrestris Zweifel, Cogger & Richards, 2005 . Oreophryne riyantoi sp. nov. differs from O. minuta by its body size (SVL 20.19– 20.70 vs. 9.2–11.5) and by dorsolateral stripes (absent vs. present) ( Richards & Iskandar 2000); from O. alticola by its ventral colour pattern (belly pale brown vs. dark with large irregular white blotches centrally); from O. brevirostris by its dorsolateral pattern (stripes absent vs. two brown stripes beginning on the nape and becoming indistinct in the lumbar region); from O. geminus by its skin texture (body and limbs irregularly tuberculated vs. body with low longitudinal ridges, most prominent laterally, slightly tuberculate on limbs); from O. habbemensis by its lateral color pattern (without spot vs. with darker spot) and its lumbar ocelli (present vs. absent); and from O. terrestris by its ventral colour pattern (belly pale brown and gular region dusted with brown vs. moderately large, irregular, well separated dark spots) ( Zweifel et al. 2005).

Etymology. The new species is dedicated to Mr. Awal Riyanto, a senior researcher at Museum Zoologicum Bogoriense (MZB), in recognition of his remarkable contributions on taxonomic work and conservation of herpetofauna in Sulawesi.

Distribution and natural history. The new species is only known from the type locality, Mekongga Mountains, Southeast Sulawesi in primary montane forest at an elevation of 2528 m. Specimens were found among leaf litter on extremely wet-forest floor, where the trees were mossy with relatively closed-canopies.According to W.T.L., Oreophryne riyantoi sp. nov. calls only between 2 and 5 am. The call, which was not recorded, was described as a series of 3–5 loud “peeping” notes, in which the last note is distinctly softer than those preceding it. We found no other amphibians in sympatry with the new species.

Figures

FIGURE 1. Map showing the known locality of Oreophryne riyantoi sp. nov. and the type localities of all other congeners in Sulawesi (from Müller 1894; Boulenger 1896; Ahl 1933).

FIGURE 3. Live specimen of Oreophryne riyantoi sp. nov. (A–B) holotype, MZB. Amph 17494. (C–D) Paratype MZB Amph. 17493. Photographed at 2528 m asl near the summit of Mount Mekongga by W.T.L.

FIGURE 4. Oreophryne riyantoi sp. nov., holotype, MZB.Amph. 17494. (A) Dorsal view, (B) ventral view, (C) lateral and dorsal view of head, (D) ventral view of right foot and right hand. Scale = 5 mm.