Platymantis akarithymus Brown and Tyler, 1968

Kraus, Fred & Allison, Allen, 2007, Two new species of Platymantis (Anura: Ranidae) from New Britain, Zootaxa 1485, pp. 13-32 : 14-17

Platymantis akarithymus Brown and Tyler, 1968

Figs. 1 A, 2A, D

Diagnosis. A small species of Platymantis (males to 25.4 mm and 1.70 g; females to 26.8 mm and 1.75 g) with moderately long snout (EN/IN = 0.89–1.08); small eye (EY/SN = 0.77–0.93); short dorsal ridges ( Fig. 1 A); fingertips only slightly flattened and barely expanded ( Fig. 2 A); first finger slightly longer than the second; dorsal surface of snout with small warts; abdomen straw with scattered brown punctations; rear of thighs heavily and uniformly dusted with brown; tubercles of plantar and palmar surfaces same color as surrounding skin; and call consisting of a single nasal note repeated at irregular intervals in a call group.

Comparisons with other species. Platymantis akarithymus may be distinguished from P. adiastolus Brown, Foufopoulos and Richards , P. browni Allison and Kraus , P. guppyi (Boulenger) , P. macrosceles Zweifel , P. mamusiorum Foufopoulos and Brown , P. nakanaiorum Brown, Foufopoulos and Richards , P. neckeri (Brown and Myers) , P. nexipus Zweifel , P. rhipiphalcus Brown and Tyler , and P. schmidti Brown and Tyler in having discs of the fingers poorly developed and scarcely wider than the penultimate phalanges (vs. considerably wider than penultimate phalanges); from P. acrochordus (Brown) in its smaller size and in lacking (vs. having) sharply pointed fingertips; from P. aculeodactylus Brown in having dorsal ridges and lacking (vs. having) sharply pointed fingertips; from P. macrops (Brown) and P. p a r k e r i (Brown) in having the first finger approximately equal in length to the second (vs. shorter); from P. boulengeri (Boettger) , P. gilliardi Zweifel , P. magnus Brown and Menzies , P. myersi Brown , P. papuensis Meyer, P. s o l o m o n i s (Boulenger), and P. weberi Schmidt by its much smaller adult size (males to 34 mm in P. gilliardi , 64 mm in P. magnus , 69 mm in P. m y e r s i, 44 mm in P. papuensis , 49 mm in P. s o l o m o n i s, 40 mm in P. w e b e r i; males unknown in P. boulengeri but females to 80 mm). Platymantis akarithymus is most similar in size and general appearance to P. mimicus Brown and Tyler , from which it differs in its smaller size (males to 40 mm SVL in P. mimicus ), first finger approximately equal in length to the second (vs. distinctly longer in P. mimicus ), and relatively smaller eye (EY/SN = 1.04–1.11 in P. mimicus ).

Description. Size small (males to 25.4 mm and 1.70 g; females to 26.8 mm and 1.75 g), vocal slits present. Head wide (HW/SV = 0.37–0.45), wider than long (HW/HL = 0.95–1.03), with oblique loreal region; canthus rostralis rounded, concave when viewed from above; nostrils small, directed laterally, much closer to tip of snout than to eyes; internarial distance generally but not always wider than distance from naris to eye (EN/IN = 0.82–1.08); snout truncate to slightly rounded when viewed from side, broadly to acutely rounded when viewed from above; eyes large (EY/SV = 0.15–0.17); eyelid larger than width of interorbital distance; tympanum distinct, fairly large (TY/SV = 0.069–0.092) but smaller than eye (TY/EY = 0.43–0.59), with a distinct annulus. Supratympanic fold short, obscure. Dorsal and lateral surfaces granular with series of short ridges and pustules, the dorsolateral ridges the longest. Dorsal surface of snout with distinct series of pustules or small ridges. Ventral surfaces generally smooth but may be granular on abdomen. Fingers unwebbed, relative lengths 3>1~2>4; tips flattened but bearing terminal grooves only on third finger, only slightly wider than penultimate phalanges ( Fig. 2 A). Subarticular and metacarpal tubercles well-developed. Toes unwebbed, bearing flattened discs with terminal grooves, except on first toe, which is slightly flattened but lacks terminal groove; relative lengths 4>3>5>2>1. Toe discs larger than finger tips, approximately half again as wide as penultimate phalanges ( Fig. 2 D). Subarticular tubercles well-developed; inner metatarsal tubercle small and oval, outer a raised circular cone; entire plantar surface covered by rows of small supernumerary tubercles. Hind legs moderately long (TL/SV = 0.49–0.60). Variation in mensural characters is presented in Table 1 .

Character Platymantis akarithymus (n = 18) Platymantis sulcatus (n = 6) Platymantis bufonulus (n = 5) Color in preservative. Dorsal ground color brown, often speckled or blotched with tan, skin around some of the dorsal ridges often marked with black; overall effect is that of a frog blotched medium and dark brown ( Fig. 1 A). Three juveniles and one adult with tan vertebral stripe. Lips blotched with dark brown. Posterodorsal quarter to half of tympanum dark brown, remainder tan. Ventral ground color dirty white to straw overlain with dark brown stippling or mottling, densest on chin and throat and diminishing abruptly on chest and abdomen. Ventral surface of thighs with pale orange wash; rear of thighs densely and uniformly stippled with brown. Plantar and palmar surfaces uniformly brown, having little contrast to metacarpal and metatarsal tubercles and none with supernumerary tubercles. Iris black stippled with silver or bronze.

Color in life. As determined from color transparencies, BPBM 22203 was tan mottled dorsally and laterally with dark brown ( Fig. 1 A). Lips were heavily barred with dark brown. Small lateral spots of orange-red were present behind and below the tympanum. Groin with orange-red flush. Iris brass with numerous black flecks and pale orange wash around the pupil.

Call. Platymantis akarithymus calls during the day, most frequently in the afternoon. We recorded three individuals from 2.6 km NNW Marmar, East New Britain Province ( Table 2 ). The vocalization included a train of 10–31 irregularly spaced notes ( Fig. 3 ). Each note was heavily pulsed at the beginning and less so at the end ( Fig. 4 A). The notes were short, with a mean duration of 58 ms (range 46–71; n = 77; Fig. 4 C), and were separated by long internotes that averaged 1.109 s (range 0.220–4.6; n = 73). The mean dominant frequency was 3560 Hz (range 1800–3960; n = 77; Fig. 4 B). The entire vocalization could be interpreted as a single multi-note call or as a group of single-note calls. It is difficult and somewhat arbitrary to distinguish between these possibilities, but to facilitate comparison with a closely related species that we describe below, we interpret the vocalization as a series of single-note calls delivered at irregular intervals in a group. Using this terminology, Fig. 3 A shows a partial call group followed by two complete call groups; Fig. 3 B includes a single, complete call group.

Ecological notes. Platymantis akarithymus inhabits primary and advanced secondary rainforest from approximately sea level to 865 m. The species is diurnally active, calling from 1200 h until dark, with a brief burst of pre-dawn calling as well. Animals were typically found while calling hidden in burrows under limestone rocks, crevices in such rocks, or under leaves, but several times animals were also found wandering on the forest floor during the day. Platymantis akarithymus is syntopic with Platymantis adiastolus , P. boulengeri , P. browni , P. gilliardi , P. macrosceles , P. nexipus , P. s c h m i d t i, and the two species whose descriptions follow.

Range. Known from low to moderate elevations in the Whiteman, Nakanai, and Baining mountain ranges. Likely occurs at appropriate elevations throughout New Britain.

Figures

FIGURE 1. Portraits of (A) Platymantis akarithymus, male, BPBM 22203; (B) Platymantis sulcatus, male, BPBM 22184; (C) P. s ul catu s, male, BPBM 22189; (D) P. sulcatus, male, BPBM 22222; (E) P. bufonulus, male, BPBM 22188; and (F) P. bufonulus, male, BPBM 22187. Photos by F. Kraus.

FIGURE 2. Palmar surface of hand for (A) Platymantis akarithymus (BPBM 22205); (B) holotype of Platymantis sulcatus (BPBM 22192); (C) holotype of Platymantis bufonulus (BPBM 22188); (D – F) plantar surface of foot for same specimens.

FIGURE 3. (A) Waveform of the complete recorded call sequence of the vocalization of Platymantis akarithymus, BPBM 22208, from 2.6 km NNW Marmar, East New Britain Province, Papua New Guinea; recorded 10 March 2005 at 1330 h, air temperature 25.2 ºC. The vocalizations at the beginning of the sequence are interpreted as a partial call group and were not included in the analysis, and (B) waveform of a single vocalization sequence of Platymantis akarithymus (uncaptured) from 2.6 km NNW Marmar, East New Britain Province; recorded 10 March 2005 at 1545 h, air temperature 23.2 ºC.

FIGURE 4. (A) Waveform, (B) power spectrum, and (C) spectrogram of the call of Platymantis akarithymus, BPBM 22208, from 2.6 km NNW Marmar, East New Britain Province, Papua New Guinea; recorded 10 March 2005 at 1330 h, air temperature 25.2 ºC.

Tables

TABLE 1. Mensural variation among adult Platymantis akarithymus and for the type series of P. sulcatus and P. bufonulus from New Britain Island, Papua New Guinea.

Mean	Range Mean	Range Mean	Range
SVL (mm) 23.5	17.5–26.8 19.1	15.3–21.6 18.1	15.4–21.4
TL/SVL 0.55	0.49–0.60 0.51	0.44–0.61 0.45	0.42–0.46
EN/SVL 0.11	0.10–0.12 0.10	0.09–0.11 0.10	0.10–0.11
IN/SVL 0.11	0.10–0.13 0.12	0.10–0.14 0.11	0.10–0.11
SN/SVL 0.18	0.16–0.19 0.17	0.16–0.20 0.17	0.16–0.18
TY/SVL 0.084	0.074–0.092 0.079	0.074–0.089 0.12	0.12–0.13
EY/SVL 0.16	0.15–0.17 0.15	0.14–0.17 0.15	0.14–0.16
HW/SVL 0.41	0.37–0.45 0.42	0.38–0.46 0.45	0.42–0.46
HL/SVL 0.41	0.39–0.45 0.40	0.37–0.45 0.41	0.38–0.43
FD/SVL 0.024	0.020–0.027 0.025	0.022–0.028 0.023	0.021–0.025
TD/SVL 0.034	0.029–0.037 0.033	0.031–0.036 0.036	0.031–0.039
EN/IN 0.95	0.87–1.08 0.88	0.81–0.91 0.93	0.88–1.04
HW/HL 1.00	0.95–1.03 0.60	0.57–1.04 1.08	1.04–1.11
FD/TD 0.71	0.55–0.80 0.85	0.82–0.85 0.64	0.56–0.73

TABLE 2. Call characteristics of Platymantis akarithymus recorded 10 March 2005 at 2.6 km NNW Marmar, East New Britain Province, Papua New Guinea.

Specimen	Time	Temperature ºC	Call No.	Total notes	Mean note Mean internote Dominant fre- duration (s) duration (s) quency (Hz)	Repetition Rate (notes/s)
Uncaptured 1	1300	25.2	A	24	0.055 1.121 3625	0.85
BPBM 22208	1330	"	B	10	0.055 1.626 3445	0.59
"	"	"	C	12	0.053 1.519 3470	0.64
Uncaptured 2	1545	23.2	A	30	0.065 0.739 3650	1.32