Choerophryne grylloides, Iannella, Amy, Oliver, Paul & Richards, Stephen, 2015

Iannella, Amy, Oliver, Paul & Richards, Stephen, 2015, Two new species of Choerophryne (Anura, Microhylidae) from the northern versant of Papua New Guinea’s central cordillera, Zootaxa 4058 (3), pp. 332-340 : 337-339

Choerophryne grylloides sp. nov.

( Fig. 1 B)

Holotype. SAMA R67921 (Field No. SJR 12700), adult male, calling when collected, un-named camp in upper Sepik River basin, West Sepik Province, Papua New Guinea (near 4°39.185’S, 141°43.448’E; 900 m a.s.l), collected by S. Richards 0 2 December 2009.

Referred specimen. A single specimen, SAMA R67928 (Field No. SJR 12885), un-named camp in upper Sepik River basin, West Sepik Province, Papua New Guinea (4°37.247’S, 141°41.380’E; 440 m a.s.l), collected by S. Richards on 13 December 2009, is tentatively assigned to this species given its morphological similarity to the holotype and the proximity of the collection site to the type locality. However, as no call or genetic data are available, this specimen is not nominated as a paratype.

Diagnosis. A small species of Choerophryne (SUL 12.5 mm) with a distinctly projecting, elongated snout (OHG/SUL 0.084); urostyle projecting posteriorly beyond the insertion of the hind limbs; long legs (TL/SUL 0.42); expanded discs present on all digits except the first finger, but not more than 1.4 times width of penultimate phalanx; dorsum densely tuberculate; and advertisement call consisting of 4–5 (normally five) distinctly pulsed notes, of which the last comprises more than double the number of pulses of its predecessors (9–10 vs. 3–4).

Comparison with other species. Choerophryne grylloides sp. nov. differs from all congeners previously included in the genus Albericus by having a distinctly projecting snout comprising an extension of the nasal bones and the alary processes of the premaxillae. From other long-nosed Choerophryne it differs in the following characters: it is much smaller (SUL <12.5 mm) than C. bryonopsis , C. longirostris , C. microps , C. nigrescens and C. proboscidea (SUL ≥ 15 mm) and further differs from these species in lacking an expanded digital disk on the first finger. It is slightly smaller than C. epirrhina sp. nov., C. gracilirostris and C. rostellifer (male SUL 12.5 mm vs. 14.9–15.0, 13.5–14.7 and 14.0– 16.8 mm respectively); and further differs from C. gracilirostris and C. rostellifer in having dense dorsal tuberculation (tubercules much smaller and less densely arrayed in C. rostellifer , localised to the flanks in C. gracilirostris ).

Choerophryne grylloides sp. nov. is distinguishable from most other small long-nosed Choerophryne species ( C. allisoni , C. amomani and C. burtoni ) by its longer snout (OHG/SUL 0.084 vs. ≤ 0.074) and longer tibiae (TL/ SUL 0.42 vs. ≤ 0.38), and from C. arndtorum by its slightly longer tibiae (Tl/SUL 0.42 vs. 0.38–0.42) and slightly shorter head (HL/SUL 0.33–0.34 vs. 0.34–0.39). Key diagnostic features of long-nosed Choerophryne found on the central cordillera of New Guinea are summarised in Table 2 .

In having calls normally containing five notes Choerophryne grylloides sp. nov. differs from C. amomani (1–2 notes), C. bryonopsis (1 note), C. epirrhina sp. nov. (4 notes), C. longirostris (3–4 notes), C. nigrescens (6–10 notes), C. proboscidea (3 notes) and C. rostellifer (3–4 notes). From all long-nosed species that produce 5-note calls C. grylloides sp. nov. differs in having terminal notes containing many more pulses than the non-terminal notes (9–10 vs. 3–4). Species regularly or rarely producing 5-note calls further differ in the following characters (comparisons with non-terminal notes of C. grylloides sp. nov. only): Choerophryne arndtorum has much longer notes (0.13–0.18 vs. 0.04– 0.06 s) produced at a slower rate (2.7–3.4/s vs. 15.7–17.5/s); C. gracilirostris produces call notes at a slower rate (7.2–13.3/s vs. 15.7–17.5/s) and containing more pulses (4–9 vs. 3–4); C. burtoni notes are much longer (0.18– 0.29 s vs. 0.017–0.035), contain many more pulses (9–15 vs. 3–4) and are produced at a much slower rate (1.36–1.64/s vs. 15.7–17.5/s); and Choerophryne microps produces 5–9 notes calls with much longer notes (0.055–0.105 vs. 0.017– 0.035 s) produced at a much slower rate (7.1/s vs. 15.7–17.5/s).

Description of holotype. Adult male with a small ventral incision on the right side, liver removed, and with the following measurements (in mm): SUL 12.5; TL 5.3; HW 4.3; HL 4.2; ED 1.3; END 1.9; IND 0.9; SL 2.9; OHG 1.1; F1D 0.1; F3D 0.5; T1D 0.3; T4D 0.6. Head rather narrow (HW/SUL 0.34), canthus rostralis weakly defined, smoothly rounded, straight in dorsal view, loreal region very slightly concave. Snout slender, projecting well beyond anterior margin of lower jaw (OHG 1.1 mm), tip rounded in dorsal and lateral profiles, ventral surface of tip with an unpigmented medial ridge, widest anteriorly and tapering towards anterior margin of the jaw. Nares oval, located close to tip of snout, oriented ventrolaterally, not visible in dorsal view, internarial distance moderately large (IN/SUL 0.073). Eye moderately small (ED/SUL 0.10), transverse diameter less than length of snout, pupil horizontal. Tympanic annulus indistinct, ventral edge faintly apparent. Tongue oval, two slightly curved prepharyngeal ridges present; vomerine teeth absent, vocal slits present just anterolateral to base of tongue. Urostyle projecting beyond vent, tip rounded and slightly elevated. Dorsum, flanks and dorsal surface of hindlimbs with scattered low, rounded tubercules; venter smooth.

Fingers moderately long and slender, with distinct circum-marginal grooves, relative lengths III>IV≥II>I, finger I more than half length of II, fingers II–IV with distinctly expanded discs up to 1.4 times width of penultimate phalanx, finger I lacking expanded disk and with only faint circum-marginal groove; subarticular and metacarpal tubercles low and poorly defined, webbing absent. Legs moderately long (TL/SUL 0.42). Toes long and slender, relative lengths IV>III>V>II>I, all toes with expanded terminal discs up to 1.4 times width of penultimate phalanx, all with circum-marginal grooves; metatarsal tubercles and webbing absent. Disks on toes wider than those on fingers (F3/T4 0.78).

In preservative, ground colour of dorsum dark brown grading laterally to medium brown, overlain with dense darker brown maculations, slightly denser anteriorly than posteriorly. Snout pale tan with few dark-brown maculations. Inguinal regions with a pair of indistinctly edged white spots. Vent bordered dorsally by a pale-buff posterior band and ventrally by a very-dark-brown band. Exposed dorsal and lateral surfaces of limbs medium brown, extensively flecked with varying darker brown and unpigmented blotches; darker pigmentation on limbs tends not to form distinct patterns, with the exception of some indistinct very-dark-brown transverse bands at the midpoint of thigh, shank and foot. Dorsal surfaces of hands and feet medium brown with extensive darker-brown flecking and numerous unpigmented patches that are increasingly large towards the distal extremities. Venter pale buff with fine tan maculations coalescing on the throat, thighs and ventral surface of limbs and feet. Palmar and plantar surfaces largely unpigmented, with light-tan speckling, coalescing to form a darker brown band at the base of the distal phalanges.

Variation. Referred specimen SAMA R67928 is slightly smaller than the holotype, with slightly shorter tibiae (TL/SUL 0.51 vs. 0.42), but is otherwise of similar dimensions ( Table 1 ). In preservative, dorsal colouration of the referred specimen is much paler than the holotype, being predominantly pale grey with a dark-brown, roughly Xshaped marking spanning the dorsum. Limbs and venter have similar colouration to the holotype. Dorsum less densely tuberculate than holotype.

Appearance in life. A photograph in life ( Figure 1 B) of the holotype taken at night, shows stronger colouration and sharper tonal variation than is evident in preservative. Medial area of dorsum black, strongly contrasting with orangish-brown snout, thighs and posterior of dorsum. Flanks and limbs with extensive scattered pale grey-blue spots. Iris black with extensive small orange-bronze flecks. Pupil horizontal, encircled by a distinctive thin bright-orange ring. Dorsal surfaces of body densely tuberculate.

Advertisement call. A single complete call from the holotype is presented in Figure 2 B. A call bout containing nine consecutive calls produced by the holotype (SAMA R67921) lasted for 9.9 seconds, and calls were produced at a rate of 0.8 calls/s. The dominant frequency was very high, ranging from 4845 hz to 5115 hz (mean = 4978, SD = 104; n = 7 calls). Calls contained 4–5 notes (but eight of nine calls had 5 notes), and were 0.23– 0.30 s long (mean = 0.28, SD = 0.02), narrowing to 0.29– 0.30 s (mean = 0.29, SD = 0.005) when the 4-note call was excluded. Non-terminal notes of each call contained 3–4 pulses ranging in length from 0.017– 0.035 s (mean = 0.023, SD = 0.035; n = 27). Notes were produced at a rate of 15.7–17.5 notes/s (mean = 16.5, SD = 0.5; n = 9). Pulse rate in non-terminal notes was 93.8–130.4/s (mean = 113.5, SD = 9.7). Terminal notes in each call were longer (0.043– 0.056 s, mean = 0.049, SD = 0.004; n = 7 calls) and contained a higher number of pulses (9–10 vs. 3–4) produced at a faster rate (167–212 pulses/s, mean = 185, SD = 14.0; n = 7 notes).

Etymology. The specific name is a feminine compound adjective, comprising the Latin gryllus (cricket) and the Greek - oides (resembles), alluding to the resemblance of the high-pitched advertisement calls of this species to the stridulatory sounds made by crickets.

Natural history and distribution. C. grylloides sp nov occurs in primary foothill rainforest on the northern side of Papua New Guinea’s central cordillera at altitudes of 440–900 m a.s.l. The holotype was calling at night from the exposed surface of a leaf, roughly 30 cm from the ground. No other individuals were seen or heard at the type locality; however, given the extent of suitable habitat in the area, this species probably has a broad distribution along the northern slopes of the central cordillera.

Figures

FIGURE 1. (A) Choerophryne epirrhina sp. nov. holotype SAMA R 67920 in life and (B) Choerophryne grylloides sp. nov. holotype SAMA R 67921 in life.

FIGURE 2. Advertisement calls (A) Choerophryne epirrhina sp. nov. (SAMA R 67920) recorded at 23.5 ° C and (B) Choerophryne grylloides sp. nov. (SAMA R 67921) recorded at 23.5 ° C. Top = waveform, bottom = spectrogram, left = power spectrum.

Tables

TABLE 2. Key diagnostic features of male long-nosed Choerophryne found on the central cordillera of New Guinea.

Species	C. epirrhina sp. nov.	C. grylloides sp. nov.	C. gracilirostris C. rostellifer	C. burtoni	C. allisoni
SUL (mm)	14.9-15.0	12.5	13.5–14.7 14.0–16.8	12.1–13.6	11.5–11.6
TL/SUL	0.41	0.42	0.37–0.40 0.37–0.47	0.33–0.37	0.33
F3D/SUL	0.05	0.04	0.03–0.04 0.03–0.06	0.02–0.04	0.03
OHG/SUL	0.09–0.10	0.08	0.06–0.09 0.08–0.10	0.03–0.06	0.04
IND/SUL	0.07	0.07	0.05–0.06 0.06–0.09	0.03–0.07	0.05–0.07