Cophixalus kethuk, Kraus, Fred & Allison, Allen, 2009

Kraus, Fred & Allison, Allen, 2009, New species of Cophixalus (Anura: Microhylidae) from Papua New Guinea, Zootaxa 2128, pp. 1-38 : 6-8

Cophixalus kethuk , sp. nov.

Fig. 1 C

Holotype. BPBM 20203 (field tag FK 10468), adult male, collected by F. Kraus along Rupu River, 11.33537ºS, 154.2247ºE, 280 m, Rossel Island, Milne Bay Province, Papua New Guinea, 15 May 2004.

Paratypes (n = 10). BPBM 20200–01, Damunu, 11.3650362ºS, 154.0013736ºE, 0–40 m, Rossel Island, 1 May 2004; BPBM 20202, W slope Mt. Rossel, 11.35435ºS, 154.22315ºE, 640 m, Rossel Island, 9 May 2004; BPBM 20204, between Rupu River and Gobubob, 11.33537ºS, 154.22343ºE, 280 m, Rossel Island, 16 May 2004; BPBM 20205–07, PNGNM 24049–51, same data as BPBM 20204 except collected 17 May 2004.

Diagnosis. A small species (male SV = 12.4–13.5 mm, female SV = 13.2–15.0 mm) with finger discs smaller than toe discs (3rdF/4thT = 0.57–0.68); first finger lacking a disc and circum-marginal groove; toes basally webbed; snout wide (EN/IN = 0.75–0.92); head narrow (HW/SV = 0.35–0.38); dorsum smooth, with wide, dark hourglass marking on dorsolateral surface; side of face dark with light speckles; and call a series of 12–13 notes like striking pebbles together, delivered with a decreasing interval toward the end that gives the impression of a marble falling on a hard surface.

Comparisons with other species. The new species differs from all other Papuan Cophixalus except C. bewaniensis Kraus and Allison , C. humicola Günther , C. pipilans Zweifel , C. shellyi Zweifel , and C. tridactylus Günther in the combination of having a first finger lacking a disc with circum-marginal groove and the finger discs distinctly smaller than the toe discs. From C. bewaniensis , C. humicola , and C. tridactylus the new species differs in retaining a recognizable first finger instead of a nub. From C. pipilans , and C. shellyi the new species differs in lacking a uniformly black face and in having dark hourglass-shaped markings on the dorsolateral surface. The only other Cophixalus having a dark hourglass pattern dorsally is C. tetzlaffi Günther , a species of larger size (males to 23 mm SV) and with the finger discs wider than the toe discs. The only other Cophixalus having toe webbing is C. tagulensis Zweifel. Cophixalus kethuk differs from C. tagulensis in its smaller size (male SV = 17.7–18.5 mm in C. tagulensis ), wider snout (EN/IN = 0.93–1.07 in C. tagulensis ), narrower head (HW/SV = 0.42–0.43 in C. tagulenis ), absence of a disc on first finger (present in C. tagulensis ), toes with only basal webbing (half-webbed in C. tagulensis ), finger discs distinctly smaller than toe discs (slightly smaller in C. tagulensis ), and dark stippling of venter in mottled pattern (evenly stippled in C. tagulensis ).

Description of holotype. An adult male with small right-lateral incision, vocal slits. Head moderately wide (HW/SV = 0.38), with oblique loreal region; canthus rostralis rounded, straight when viewed from above; nostrils directed laterally, closer to tip of snout than to eyes; internarial distance larger than distance from naris to eye (EN/IN = 0.92, IN/SV = 0.094, EN/SV = 0.087); snout slightly rounded when viewed from the side, truncate when viewed from above; eyes moderately large (EY/SV = 0.13); eyelid approximately 2/3 width of interorbital distance; tympanum small (TY/SV = 0.047), anterior and ventral margins of annulus distinct, posterior and dorsal margins largely hidden. Dorsal, lateral, and ventral surfaces smooth; supratympanic fold absent. Fingers unwebbed; relative lengths 3>4>2>1; bearing discs with terminal grooves on F2–F4; first finger somewhat reduced, lacking disc; finger discs barely wider than penultimate phalanges. Subarticular tubercles low and indistinct; metacarpal tubercles distinct, inner elongate, outer round and positioned centrally away from margin of palm. Toes with basal webbing, bearing discs with terminal grooves; relative lengths 4>3>5>2>1. Toe discs considerably larger than those of fingers (3rd F/4thT = 0.57); disc of fourth toe approximately 1.5 times width of penultimate phalanx; disc of first toe slightly wider than penultimate phalanx. Subarticular tubercles low; inner metatarsal tubercle oval, outer lacking. Hind legs moderately long (TL/SV = 0.46).

Dorsum medium brown, vaguely clouded with slightly darker brown, and with an obscure V-shaped blotch medial to but just posterior to eyes; with two broad dorsolateral stripes of dark brown, these constricted medially in scapular region such that the mid-dorsal ground forms an hourglass pattern; these dorsolateral dark stripes sharpely margined medially, gradually fading and irregularly broken laterally. Lower sides dark brown spotted with white. Face dark brown flecked with white. Most of tympanum dark brown; anteroventral third white punctated with brown. Front and rear of thighs dark brown spotted with white on ventral half. Venter and undersides of legs with a dirty white ground color heavily flecked with dark brown, giving appearance of dark-brown venter evenly spotted with white. Iris black.

Measurements (in mm). SV = 12.7, TL= 5.9, HW = 4.8, HL = 4.3, IN = 1.2, EN = 1.1, SN = 1.7, EY = 1.6, TY = 0.6, 3rd F = 0.36, 4th T = 0.63.

Variation. Mensural variation for the type series is shown in Table 2 . Color patterns are rather uniform; specimens differ primarily in their degree of melanization, so that some specimens are lighter overall than the holotype, with the dark dorsolateral stripes not extending so far ventrally on the sides. Most specimens have the dark V-shaped interocular blotch more distinctly developed than the types. Degree of brown flecking on the ventral surfaces varies such that lightly melanized specimens appear to have almost white venters vaguely clouded with light brown, while darker specimens have the same appearance as the holotype, looking to be dark brown ventrally with scattered white spots.

Color in life. BPBM 20200: “Dorsum mud brown, mottled with dark gray, creating hourglass pattern out of dorsal color. Iris brown with red rim around pupil. Venter dark gray with numerous light gray flecks.” BPBM 20201 had the dorsum muddy orange-brown and the iris black reticulated with gold, but also with a red rim around the pupil. BPBM 20202 had the dorsum brown with broad black dorsolateral bands having indefinite lateral borders, few scattered tiny white spots, and a black mark between eyes; rear of thighs as dorsum; venter dark gray with light gray flecks; and iris dark brown with red margin to the pupil. Several specimens (BPBM 20205–07, PNGNM 24049–51) were lighter at night, being light orange-brown dorsally and pale gray, almost white, ventrally.

Character Males (n = 6) Females (n = 5)

Call. This species calls primarily just at dawn and for the last hour or so before nightfall. We also heard it during the night at 750 m but not at 250– 275 m. It calls from under brush piles, under boulders, under leaves on the soil surface, and from under rocks near the surface of deep rock piles.

The call sounds like two pebbles hitting each other, with the interval between notes quickly decreasing toward the end of the call. This gives an acoustic impression similar to that of a marble falling and quickly coming to rest on a.hard surface.

We recorded six calls produced by the holotype ( Table 3 ). These were produced at intervals ranging from 7–17 s, included 12–13 notes and averaged 1.39 s (range 1.36– 1.45 s). Mean note duration was 0.0068 s (range 0.0035–0.0165). The intervals between notes averaged 0.1136 s (range 0.0015–0.1765). The repetition rate averaged 8.3 notes/s (range 7.9–8.8). There is a tendency for the interval between notes to steadily decrease and then to abruptly decrease for the last 3–4 notes. This is apparent in the spectrogram ( Fig 5 A) and is shown graphically in Fig. 6 . The duration of the first internote in the six calls analyzed averaged 0.1683 s (range 0.1562–0.1765) compared to an average of 0.0047 s (range 0.0015–0.0079) for the last internote. The dominant frequency of the calls averaged 4530 Hz (range 4400–4800 Hz) ( Fig. 5 B, C).

Etymology. The trivial epithet is a noun in apposition, being the Javanese name of a gamelan instrument whose manner of playing involves a dribble of subdividing strokes whose acoustic impression is similar to the advertisement call of this species. It is pronounced “kë- tu’ ”, where the bold notes the stressed syllable and the “’” is a glottal stop.

Range. Known only from Rossel Island, Milne Bay Province, Papua New Guinea ( Fig. 7 ).

Ecological notes. Animals were common but difficult to locate because of their habit of calling beneath objects, most often rocks or boulders. We found it to occur from approximately sea level to 640 m in primary and advanced secondary rainforest.

Figures

FIGURE 1. Photos in life of (A) holotype of Cophixalus cupricarenus (BPBM 20223), (B) paratype of Cophixalus cupricarenus (BPBM 20208), (C) paratype of Cophixalus kethuk (BPBM 20202), (D) paratype of Cophixalus iovaorum (BPBM 19280), (E) paratype of Cophixalus desticans (BPBM 15703), and (F) paratype of Cophixalus desticans (BPBM 16434).

FIGURE 5. (A) Waveform, (B) power spectrum, and (C) spectrogram of call “ A ” (see Table 3) of holotype of Cophixalus kethuk (BPBM 20203) recorded by F. Kraus along the Rupu River, 280 m elevation, Rossel Island, Milne Bay Province, Papua New Guinea, at 1715 h, 15 May 2004. Air temperature 25.7 ° C. The call was recorded on a Sony MDSJE 480 minidisc recorder and was slightly overmodulated, producing the false harmonics seen above 10 Hz.

FIGURE 6. Internote duration of call “ D ” (see Table 3) recorded from the holotype of Cophixalus kethuk (BPBM 20203).

FIGURE 7. Map showing known distributions for Cophixalus interruptus (circle), C. kethuk (inverted triangles), C. linnaeus (star), and C. phaeobalius (square). Filled symbols are type localities; open symbols are additional localities, as relevant.

Tables

TABLE 2. Mensural data for type series of Cophixalus kethuk sp. nov. Data include only adult animals.

	mean	range	mean	range
SV (mm)	12.9	12.4–13.5	13.9	13.2–15.0
TL/SV	0.45	0.43–0.47	0.44	0.22–0.46
EN/SV	0.081	0.073–0.087	0.079	0.075–0.083
IN/SV	0.097	0.092–0.103	0.093	0.087–0.098
SN/SV	0.13	0.12–0.13	0.13	0.11–0.14
TY/SV	0.047	0.044–0.048	0.049	0.045–0.053
EY/SV	0.14	0.13–0.14	0.14	0.12–0.15
HW/SV	0.37	0.36–0.38	0.36	0.35–0.37
HL/SV	0.33	0.31–0.34	0.33	0.31–0.34
3rdF/SV	0.033	0.028–0.038	0.030	0.026–0.034
4thT/SV	0.053	0.050–0.056	0.048	0.040–0.054
EN/IN	0.84	0.75–0.92	0.85	0.79–0.92
3rd F/4th T	0.63	0.57–0.68	0.64	0.59–0.68
HL/HW	0.89	0.86–0.91	0.92	0.90–0.96