Platymantis citrinospilus, Brown, Rafe M., Richards, Stephen J. & Broadhead, Taylor S., 2013

Brown, Rafe M., Richards, Stephen J. & Broadhead, Taylor S., 2013, A new shrub frog in the genus Platymantis (Ceratobatrachidae) from the Nakanai Mountains of eastern New Britain Island, Bismarck Archipelago, Zootaxa 3710 (1), pp. 31-45 : 33-40

Platymantis citrinospilus sp. nov.

Figs. 2–4

Holotype. South Australia Museum (SAMA) R64758 (SJR Field No. 10860), adult male, collected by S. J. Richards at Tompoi Camp, 1700 m above sea level (05°20.623'S, 151°18.873'E; WGS-84), Nakanai Mountains, East New Britain Province, Papua New Guinea, 23 April 2009.

Paratypes. SAMA R64756, R64757 (SJR Field Nos. 10831, 10832), and Papua New Guinea National Museum (PNGNM) 24042 (SJR Field No. 10811) three adult males, same locality data as holotype, SAMA R64756, 64757 collected 22 April 2009, and PNGNM 24042 collected 21 April 2009.

Etymology. The specific epithet, a masculine name, is derived from the Greek adjective kitrinos (yellow) and the Greek noun spilos (spot or stain), in reference to the distinctive bright yellow flank areolations of all known specimens ( Fig. 2 ).

Diagnosis. Platymantis citrinospilus is assigned to the genus Platymantis on the basis of established diagnostic characters for the genus (Small body size, lack of interdigital webbing, presence of distinct subarticular tubercles, expanded terminal phalanges of the hand and foot, and nuptial pads absent; Brown 1952; Gorham 1965; Menzies 2006) and it is distinguished from congeners by (1) body size (29.5–32.2 mm in four males), (2) widely expanded terminal disks of the fingers and toes ( Figs. 2 , 3 ), (3) skin of dorsum smooth to finely granular with enlarged dermal, fleshy tubercles, (4) ventral surface of subarticular tubercles on fingers, toes, hands and feet uniformly low and flattened, (5) fingers and toes without lateral dermal flange, (6) interdigital webbing absent, (7) tibio-tarsal articulation with prominent, ornate white dermal tubercles, (8) flank with prominent yellow areolations, (9) intraocular region with low but distinct mid-sagittal crest, and (10) unique advertisement call consisting a relatively slow series of dull, high-frequency notes (resembling the sound produced by slowly striking together two pieces of wood).

Comparisons.—The new species is phenotypically most similar to (and likely most closely related to) a pair of other Nakanai Mountains shrub frogs, P. macrosceles and P. mamusiorum . Platymantis citrinospilus differs from P. macrosceles by the presence of brick reddish-brown ground coloration ( Fig. 2 ) with bright yellow flank areolations (versus homogenous bright green body coloration), by the presence of low supra-ocular and tarsal tubercles (versus presence of highly enlarged, white and prominent tubercles; Fig. 2 ), by the presence of a conspicuous mid-saggital crest between the eyes (versus absence), by its mottled bronze-brown iris (versus light lime green iris), and by its higher frequency, slowly-pulsed advertisement call (versus lower frequency, rapidly pulsed call). Platymantis citrinospilus is also a high elevation species, known only from 1700 m above sea level in the Nakanai Mountains while Platymantis macrosceles has only been recorded at elevations between 800 and 900 m above sea level (Foufopoulos & Brown, 2004; Foufopoulos & Richards, 2007); neither species has been recorded at intervening elevations despite multiple surveys (Foufopoulos & Brown, 2004; Foufopoulos & Richards, 2007). Platymantis citrinospilus differs from syntopic P. mamusiroum by the presence of fleshy dermal dorsal tubercles (versus absence; interocular region flat), by its more pointed (versus rounded) snout and sharp (versus sloping) canthus, by its brick reddish-brown dorsal ground color and lateral yellow flank areolations (versus bright dreen dorsum with fine brown reticumum), by the presence (versus absence) of supra-ocular and tarsal tubercles, and by its pulsed advertisement call (versus a stridulated series of “croaks” or “crunches” in P. mamusiorum ). Of the other tree-dwelling shrub frogs of New Britain, Platymantis citrinospilus (SVL 29.5–32.2) differs from the larger P. nakanaiorum (SVL 35.8–38.0) and P. nexipus (SVL 39.3–43.7) and the much smaller P. caesiops (SVL 18.9–22.9) by body size, and more extensive dorsal, supra-ocular, and extensive (versus minimal) tarsal tuberculation, and pulsed (versus click and buzzes) advertisement call (Foufopoulos & Brown, 2004; Brown et al., 2006a; Kraus & Allison, 2009) ( Table 1 ). Platymantis citrinospilus can easily be distinguished from all terrestrial species of Platymantis on New Britain ( P. adiastolus , P. akarithymus , P. boulengeri , P. bufonulus , P. gillardi , P. magnus , P. mimicus , P. schmidti , and P. sulcatus ) by the presence of widely expanded digital disks of fingers and toes (versus finger and toe termini non-expanded to slightly expanded); additional morphological and acoustic differences are summarized by Brown and Tyler (1968), Brown and Menzies (1979), Brown et al., (2006a,b), and Kraus and Allison (2007).

Description of holotype —A mature male, in excellent condition; habitus slender; head slightly distinct, equal in dorsal aspect to width of body, HL 36.6% SVL; HL100% HW; snout moderate, terminating in bluntly round point in lateral and doral aspects, protruding only sigthly beyond lower jaw; eyes protrude only slightly beyond silhouette of head in dorsal aspect, and moderately beyond dorsal surface of head in lateral aspect; labial region slightly flared, not extending beyond eyes in dorsal aspect; interorbital region with a moderately prominent, longitudinally-oriented crest; ED 120% IOD; pupil horizontally ovoid; canthus rostralis markedly medially bowed; loreal region very concave; ED 61.0% SNL; narial openings slightly laterally protuberant; eye-narial distance 5 times the distance from nostril to tip of snout; internarial region flat; tympanum distinct, TD 56% ED; dorsal edge of tympanic annulus partially concealed by supratympanic fold, the latter extending from dorsoposterior edge of eye, over dorsal edge of tympanum, and terminating at supra-axillary (post-rictal) region; two or three conical postrictal tubercles present between posteroventral edge of tympanum and forearm insertion (one much larger than others); tongue triangular, with shallow posterior notch and narrow anterior attachment; choanae round, minute, at anterolateral edge of palate, separated by a distance 6–8 times their diameter, not obscured by palatal shelf; dentigerous process of vomer ovoid; vomerine teeth minute, translucent, numbering two or three; dentigerous process anterolaterally angled, with closest (posterior) points separated by a distance 1.5 times the diameter of one choana, their most distant (anterior) ends separated by a distance equal to three or four times diameter of choanae; openings to vocal sac minute slits, at the level of the angle of the jaw.

Skin of dorsal surfaces of body, head, and limbs finely granular, with ornamentation in the form of moderate fleshy conical dermal tubercles (lacking obvious keratin) in supra-orbital, post-orbital, and post-rictal regions ( Fig. 2 ); dermal tubercles of lateral body surfaces and dorsal limb surfaces low and irregularly scattered; two infralabial tubercles barely visible in ventral and lateral aspect at the outer (posterior) margins of the jaw; low fleshy tubercular ridges present on lateral edges of radii and sacral region; irregular row of prominent tubercles extends along the posteromedial (postaxial) edge of tarsal segment of the hind limb ( Fig. 3 ), clustered most prominently and densely clustered at tibio–tarsal articulation; ventral surfaces of trunk, head, and throat, slightly glandular, becoming more coarsely glandular in posterior quarter of trunk, groin, and medial half of the humeri.

Hand length 65.6% PL; fingers ( Fig. 4 ) wide and round in cross-section, (lateral dermal flanges absent); terminal disks barely expanded (Finger I) to widely expanded (> 2 times the width of penultimate phalanges in Fingers II–IV), with circum-marginal folds encircling distal edges of disks; supra-articular folds indistinct, more evident above penultimate and ultimate phalangeal articulation of inner two fingers; decreasing finger length III, IV, II, I; subarticular tubercles low, mostly flat on ventral surfaces, not pointed, the most prominent angled slightly anteriorly towards tip of fingers; one subarticular tubercle under fingers I–II, two tubercles under fingers III–IV; supernumerary tubercles flat and somewhat indistinct, present at the base of fingers II–IV; palmar surfaces basal to supernumerary tubercles nearly smooth; thenar (inner metacarpal), medial palmar and outer metacarpal tubercles moderate, flat on ventral surfaces, edges irregular but distinct, unpigmented; thenar tubercle irregularly ovoid, situated on medial edge of finger I; medial palmar (inner metacarpal) tubercle ovoid on left, elongate on right, only moderately enlarged, with slightly distinct, raised medial edge, approximately the same size as thenar tubercle; outer metcarpal tubercles small, ovoid, slightly more than half the size inner metacarpal tubercle and distinct (separated from medial metacarpal tubercle); nuptial pads absent, forearm musculature not well developed or hypertrophied.

Species: P. citrinospilus P. macrosceles P. mamusiorum P. nakanaiorum P. nexipus P. caesiops

(4) (4) (6) (4) (16) (2) SVL (mm) 29.5–32.2 29.4–31.8 27.4–30.7 35.8–38.0 39.3–43.7 18.9–22.9 Hindlimbs long; TBL 58.5% SVL, PL 83.2% TBL; skin of dorsal hind limb surfaces smooth; tarsus smooth, with prominent posteriorly oriented conical tubercles; low conical tubercles distributed along postaxial dermal tarsal flange and at heel; tubercles most prominent and clustered around tibio-tarsal articulation; terminal toe disks non-expanded (Toe V), narrowly expanded (<2 times the width of penultimate phalanges; Toes I and IV) to moderately expanded (> 2 times the width of penultimate phanges; Toes II, III), with circum-marginal grooves and supra-articular cutaneous folds; plantar surface of feet ( Fig. 4 ) smooth, devoid of supernumerary tubercles, with well-developed, prominently rounded (not pointed) subarticular tubercles; subarticular tubercles with flattened ventral surfaces, three under Toe IV, two under Toes III and V, and one under Toes I and II; decreasing toe length (longest to shortest when adpressed) IV, III, V, II, I; outer metatarsal tubercle small, round, pointed; separated from inner metatarsal tubercle by distance three times width of outer; inner metatarsal tubercle low, flat, moderate, oblong, with slightly sharp medial edge, four to five times size of outer metatarsal tubercle; toes without interdigital webbing.

Cloacal region coarsely glandular, with small supra-cloacal dermal flap; low, fleshy cluster of enlarged white tubercular swellings present ventrolaterally on each side of vent.

Measurements of holotype —SVL 32.2; ED 3.9; TD 2.2; HL 12.8; SNL 6.1; END 3.9; IOD 2.6; HW 11.9; FL 16.0; TBL 17.5; TSL 9.7; PL 15.3; ML 10.3; FA 5.1; Toe4L 9.5; Fin1L 4.3; Fin3L 3.8; Fin3DW 2.4; Fin3PPW 0.8; Toe4DW 1.1; Toe4PPW 0.8.

Coloration of holotype in preservative —Dorsal surfaces of body, head and limbs dark brick reddish-brown (ground coloration of dorsal and lateral surfaces of head distinctly darker), with scattered diffuse steel gray-green pigmentation clustered most densely on snout, eyelids, forearms, midbody and sacral regions, knees, and tibial segments of hindlimbs; congregation of this pigmentation feature forms a fine vertebral line from tip of snout to vent; grey-green pigment densely clustered along outer margins of eyelids, continuous with lateral snout pigmentation and forming a prominent palpebral–canthal “stripe;” dark dorsal color continues laterally on to brick reddish-brown flanks, with prominent series of bold, highly distinct, yellow spots and blotches running in a continuous series from inguinal region, across all ventrolateral surfaces, to supra-articular region above forelimb insertion (terminating below tympanum); a similar, bold marking is angled obliquely across the tympanum (anteriodorsally to posteroventrally); labial region similarly bright pale yellow, nearly devoid of any dark pigment; dorsal surfaces of forelimbs light brick reddish-brown, with less dense steel gray-green pigment than dorsal surfaces of body, lacking transverse bars; dorsal surfaces of hands and fingers light reddish-brown, with differentiated absence of brown (resulting in pale cream color in unpigmanted areas) on articulations of penultimate–ultimate phalanges; dorsal surfaces of finger disks light cream with brown blotches (Fingers III and IV) or bright cream (Fingers I and II); dorsal surfaces of hindlimbs orange-brown on femur, steel gray-green on tibia, and orangish-brown on tarsus, transverse bars absent; concealed surfaces on posterior thighs orangish-brown with large bright pale yellow spots, similar to those on flanks; dorsal surfaces of toes light brown with slightly darker terminal disks on outer toes (IV and V) and lighter cream on inner toes (I–III); ventral surfaces orangish brown with distinct, bold pale yellow spots, wrapping on to ventrum from lateral surfaces; underside of throat homogenous orangish-brown contrasting with bright pale yellow lower lip; ventral surfaces of forelimbs reddishbrown, with irregular bold pale yellow markings on upper arms, some steel gray-green pigment wrapping ventrally from lateral surfaces, bright pale yellow forearm tubercles, and pale cream subarticular tubercles and ventral surfaces of terminal finger disks; ventral surfaces of glandular skin of trunk orangish, fading to pale gray midventrally; ventral surfaces of hindlimbs slightly darker orangish brown with a few bold pale yellow spots on femoral segments; ventral surfaces of foot homogenous reddish-brown with pale yellow to cream subarticular tubercles and gray terminal disks.

Variation —Our small type series exhibits some notable color variation but the types are generally phenotypically similar to one another. The holotype (SAMA R64758) exhibits markedly more steel gray-green pigmentation than the three paratypes, although PNGNM 24042 has this same pigment on its limbs and head, and all specimens have this color feature on eyelids and lateral surfaces of limbs. The paratypes all exhibit dorsal coloration darker than that of the holotype. SAMA R64756 and R64757 have notably lighter, homogenous orangish-brown dorsal coloration. All specimens possess the faintly lighter, thin vertebral line from snout to vent (least evident in SAMA R64756). No specimens have transverse bars on limbs, and all paratypes have nearly homogenous orangish-brown dorsal limb color. The bold lateral pale yellow flank areolations are present in all specimens but vary in size and density ( Fig. 2 ). The holotype (SAMA R64758) and paratype PNGNM 24042 exhibit a series of large areolations that connect into a near-continuous wavy line, whereas SAMA R64756 possesses nearly discrete, unconnected flank spots. SAMA R64757 has discrete spots on the left flank but fewer, partialy connected spots on the right. In SAMR R64756 and 64757, flank areolations are bordered by thin black lines. Bold yellow flank spot series continue to the infratympanic region (above forearm insertion) and extend onto the tympanum in the holotype (SAMA R64758) and paratype PNGNM 24042 while in paratypes SAMR R64756 and 64757, distinct pale yellow spots extend only to the ventral edge of the tympanum. In these latter specimens, tiny pale yellow spots are also present at the center of the tympanum. All specimens exhibit bright, pale yellow upper and lower labial coloration which is interrupted by orangish-brown pigment in SAMR R64756 and 64757.

Ventral coloration is nearly invariant and similar to that of the holotype except that darkened pigment on the throat (congregation of dark pigment marking the positions of the vocal sacs) is more evident in SAMA R64756 and 64757, and in SAMA R64758 more bright pale yellow spots extend from flanks on to the ventral surface of the trunk. Variation in bright pale yellow spot configurations on the posterior surfaces of the thighs and the cloacal region is as follows: in the holotype (SAMA R64758) spots on the distal portions of the posterior surfaces of the thighs are distinct and separate, and gradually fuse together to form a continuous supra-cloacal marking; in PNGNM 24042, a bright pale yellow supra-cloacal bar is present and distal thigh spot are absent; and in SAMR R64756 and 64757 only a few small, intermittently fused, bright pale yellow spots are present in the cloacal region. Ventral surfaces of the hands and feet are largely invariant, although subarticular tubercles and terminal disks of SAMA R64756 and 64757 are cream to light gray whereas these same structures are pale yellow in paratype PNGNM 24042and the holotype (SAMA R64758).

Coloration in life —Based on color images of all specimens in life (images of the holotype, SAMA R64758, and paratypes PNGNM 24042 and SAMA R64756 are included in Fig. 2 ). Dorsal ground coloration dark brick reddish-brown with extensive (SAMA R64758), limited (PNGNM 24042) or nearly absent suffusion of light green pigment on dorsal surfaces of head, trunk and limbs ( Fig. 2 ). When juxtaposed with white dermal tubercles on dorsal surfaces, overall pale green lichenatious color results on dorsum (strongest in holotype SAMA R64758). All specimens have a thin light cream to white vertebral stripe, a bright immaculate white (SAMA R64756) to yellow (SAMA R64758, PNGNM 24042) labial and postrictal region, with (SAMA R64758, PNGNM 24042) or without (SAMA R64756, PNGNM 24042) intrusion of bright postrictal coloration on to ventral edge of the tympanum. Lateral head color similar to dorsum; iris pale brown above and below the pupil. Flank surfaces and concealed posterior surfaces of the thighs with bold, bright yellow areolations varying from numerous (10–12) small but distinct yellow spots (SAMA R10831) to four or five larger blotches with irregular borders.

Dorsal limb surfaces were colored as body, with indistinct slightly darker reddish-brown transverse bars present (PNGNM 24042) or absent (remainder). The dorsal surfaces of the digits were brick reddish-brown; expanded digital disks white.

Ventrum was pale pink, with dark red throat, and reddish color wrapping slightly on to ventrum from lateral surfaces ( Fig. 3 D). In life the ventral body surfaces of SAMA R64756 and PNGNM 24042 were somewhat translucent, with darker and lighter organs visible though the skin. The ventral surfaces of limbs were dark red with bold yellow spots; the ventral surfaces of all specimens’ hands and feet were dark red with pale yellow (PNGNMR24042) to cream subarticular tubercles and terminal ventral surfaces of digital disks (remainder).

Advertisement call and acoustic comparisons to P. macrosceles —The following call descriptions are based on two recording segments approximately of two minutes per species. Calls of P. citrinospilus (both individuals vouchered, SAMA R64758 and R64756) and P. macrosceles (UWZM 23721, another individual recorded but not collected) were all recorded at ambient temperatures of 16.9–18.0°C.

Platymantis citrinospilus calls (defined here as sounds produced per single expiration) consist of a relatively slow series of dull, medium-frequency notes sounding to the human ear like the sound produced by striking together two pieces of wood. Depending on the number of pulses included, calls vary from short “warm-up” single-pulse chirps (n=4 recorded), short calls (2–3 pulses) to lengthy (n=2 recorded), drawn-out trains of 10 or 11 pulses. Individual pulses consist of a rapid rise from ambient to peak sound levels (2–3 ms), then a slower decline to ambient levels (8–10 ms). Pulses are followed by a brief sub pulse (5–10 ms), which has a relative peak amplitude 43–49% that of the initial pulse. SAMA R64758 called 11 times over a period of 23 seconds (0.045 calls/s). The mean pulse duration in short calls was 43 ms (range: 39–47 ms) and the mean interpulse interval was 125 ms (range 116–132). Mean pulse repetition rate for short calls was 2.17 pulses/s (range: 1.98–2.30). Long calls consisted of 10 or 11 (SAMA R64758 and R64756, respectively) pulses over approximatey 2 s time intervals. The pulse repetition rates for these two calls were 5.5 and 5.8 pulses/s respectively. Over long calls mean pulse duration was 23.8 ms (range 10.5–26.2) and the mean interpulse interval was 159 ms (range: 147–164). Dominant (=fundamental) frequency was 3.0 kHz in SAMA R64758 (with peak frequencies for two faint harmonics at 6.0 and 9.6 kHz respectively) and 3.1 in SAMA R64756. We detected no evidence of stereotyped amplitude or frequency modulation across the call.

The advertisement call of P. citrinospilus differs from that of P. macrosceles (recorded at 17–18°C; see Foufopoulos and Brown, 2004, for a full description) by (1) a lower pulse repetition rate (mean = 5.5, 5.8 pulses/s for two individuals; versus 11.2, 11.7 pulses/s in P. macrosceles , giving the overall impresssion of a “slower” call in the new species), (2) the absence of distinct subpulses before the primary pulse (subpulses present in P. macrosceles ), (3) a markedly higher dominant frequency (3.0, 3.1 kHz); throughout the call (verus 2.5, 2.7 kHz in P. macrosceles ), (4) the absence of frequency modulation at the initial onset of long calls (versus frequency increase at start of long calls in P. macrosceles ), (5) invariant pulse duration and interpulse interval (versus steady, progressive increase in these characters in P. macrosceles , giving the immpression in the latter species of a vocalization that gets slower towards the end of each call) and (6) the absence of a rapid initial burst of pulses at the start of each long call (3–6 pulse initial bust of pulses present in P. macrosceles ). Although the above differences are slight, they are entirely consistent across the calls analyzed, conistent with calls heard in the background of recording segments focused on other species (Foufopoulos & Brown 2004; Brown et al. 2006a, b; J. Foufopoulos, SJR and RMB, unpublished data) and are consistent with numerous calls heard but not recorded in the field (SJR, personal observations).

Ecology, Distribution, and Natural History.—Tompoi Camp is located in a patch of mossy montane forest surrounded by dense thickets of native bamboo. During the visit of SJR (19–25 April, 2009), this site was extremely wet from the frequent rain and dense fog that shrouded the forest on most days. No aquatic habitats were found in the vicinity and all frog species encountered are direct developers. The new species called from elevated perches, on leaves 30–100 cm above the ground in small shrubs that were surviving in small pockets within dense native bamboo thickets. Sympatric species included Batrachylodes sp., Platymantis adiastolus , P. nakanaiorum , P. mamusiorum , P. cf. sulcatus and Oreophryne brachypus . The new species is known only from the type locality, Tompoi Camp, 1650–1700 m above sea level in the Nakanai Mountains of eastern New Britain Island, Bismarck Archipelago.

Figures

FIGURE 2. Photographs in life of the holotype (A: SAMA R 64758) and paratypes (B: PNGNM 24042, C: SAMA R 64756) of Platymantis citrinospilus and P. macrosceles (D: SAMA R 64815).

FIGURE 3. Close up images of of the holotype of P. citrinospilus (A, C: SAMA R 64758) and a paratype (B, D: PNGNM 24042) in life. Note white optical sclera encircling orbit (A), continuation of lateral areolation spot series into supracloacal region (B), low but distinct tarsal tubercles (C), and semi-transparent ventrum (D).

FIGURE 4. Close views of ventral surfaces of right hand (ML = 10.3 mm) and foot (PL = 15.3 mm) of Platymantis citrinospilus holotype (A: SAMA R 64758).

Tables

TABLE 1. Summary of the distribution of selected qualitative (+ present, – absent) and quantitative diagnostic characters and ranges of morphometric ratios in male specimens of Platymantis citrinospilus and the phenotypically similar species from the New Britain. (sample size of males in parentheses; females examined when available [Specimens examined] but not included in measurements).

Dermal body – or + tubercles	+	–	– or +	–	–
Pointed dorsal – asperities	+	–	– or +	–	–
Supraocular Low tubercles	Prominent	–	– or Low	– or Low	–
Tarsal tubercles Low	Prominent	–	– or Low	–	–
Dorsolateral – folds/ridges	–	– or +	–	+	–
Sagittal crest +	–	–	–	–	–