Xenorhina wiegankorum, Günther & Richards, 2021

Guenther, Rainer & Richards, Stephen, 2021, Description of six new species of Xenorhina Peters, 1863 from southern Papua New Guinea (Amphibia, Anura, Microhylidae), Zoosystematics and Evolution 97 (2), pp. 355-382 : 355

Xenorhina wiegankorum sp. nov.

Holotype.

SAMA R71653 (SJR 10372), adult male, from Baia River, Western Province, Papua New Guinea (6.0205°S, 142.5473°E; 330 m a.s.l.), collected by S.J. Richards on 15-02-2008.

Paratypes.

PNGNM (FN SJR10373), adult male, same details as for holotype; SAMA R71654 (FN SJR10400), adult male, from Camp 2, upper Strickland River basin, Western Province, Papua New Guinea (5.9018°S, 142.4360°E; 950 m a.s.l.), collected by S.J. Richards on 19-02-2008; ZMB 91132 (FN SJR14220), adult male, Rentoul River, Western Province, Papua New Guinea (6.4355°S, 142.5615°E; 380 m a.s.l.), collected on 14-08-2014 by S.J. Richards; SAMA R65073 (FN SJR10948), adult male, Gugusu Camp, Muller Range, Western Province (5.7290°S, 142.2630°E; 515 m a.s.l.), collected by S.J. Richards and C. Dahl on 8-09-2009.

Diagnosis.

This species of Xenorhina is characterised by the unique combination of: medium size (males 32.0-35.7 mm SUL); vomeropalatines each with one strongly developed triangular spike; legs moderately long (TL/SUL 0.44-0.47); all fingers tips without and all toe tips with expanded discs; eye-naris distance greater than internarial distance (END/IND 1.19-1.37); tympanum same size as, or slightly smaller than, eye (TyD/ED 0.80-1.00). Dorsal surfaces in life different shades of grey or brown; ventral surfaces different shades of red or yellow, throat and chest with some darker flecks. Advertisement calls uttered in series lasting 10-20 s and containing 20-40 calls; length of calls 60-100 ms, dominant frequency at 0.5 kHz.

Description of the holotype.

Measurements are summarised in Table 5 , a dorsolateral view in life is shown in Fig. 12a and ventral surfaces in life in Fig. 12b . Head broader than long (HL/HW 0.84); snout acuminate from above and below and distinctly protruding in profile; vomerine spikes strongly developed; prepharyngeal ridge clearly expressed with about 14 denticles; tongue long, broad, not bilobed posteriorly; loreal region oblique, no canthus rostralis; nostrils near tip of snout, positioned dorsolaterally, visible from above, but not from below; eye-naris distance greater than internarial distance (END/IND 1.37); tympanic annulus more strongly defined in preservative than in life, its diameter smaller than that of eye (TyD/ED 0.80); well defined supratympanic fold extends from marginally behind eye to insertion of fore leg; shank moderately short (TL/SUL 0.44); fingers moderately short, not webbed, tips of all fingers not wider than penultimate phalanges, but with circum-marginal grooves, relative lengths of fingers 3> 4> 2 = 1 (Fig. 12c ); all toe tips acuminate, but wider than penultimate phalanges, with circum-marginal grooves; toes not webbed, relative lengths 4> 3> 5> 2> 1 (Fig. 12d ); plantar, palmar and subarticular tubercles barely defined. Body laterally and dorsum of legs partly, with scattered small tubercles in life and in preservative; all ventral surfaces smooth; tip of snout (especially ventrally) with several tiny elevations.

In life, all dorsal surfaces almost uniformly light olive-brown (RAL 8008); lumbar spot absent; back with yellowish mid-dorsal line that continues along hind legs on to tarsus; tubercles with whitish apices concentrated mainly on lateral surfaces of body; large dark triangular spot on posterior of thighs around vent absent; iris blackish with golden speckles; ventral surfaces of toes predominantly signal-grey (RAL 7004), plantar surfaces brown-grey; ventral surfaces of fingers and palms predominantly signal-grey; abdomen and ventral surfaces of thighs, shanks and arms melon-yellow (similar to RAL 1028) with inconspicuous whitish spots; ground colour of throat and chest also melon-yellow, but overlain with dense pattern of beige-grey and off-white spots.

In preservative, all dorsal surfaces pastel-violet (RAL 4009), with only few darker areas and inconspicuous whitish tubercle apices. Melon-yellow ventral surfaces faded to ivory colour in preservative and pattern on chest and throat changed from beige-grey to brown-beige (RAL 1011).

Morphological variation.

Morphometric data for all paratypes are similar (Table 5 ). Colour pattern of ZMB 91132 (and probably of PNGNM [SJR 10373]) in life is similar to holotype. Dorsal surfaces of SAMA R71654 are telegrey (RAL 7045) with small whitish spots (Fig. 13 ) and ventral surfaces predominantly broom-yellow (RAL 1032). Dorsal surfaces of SAMA R65073 are a mixture of stone-grey (RAL 7030) and brown-grey (RAL 7013) reticula interspersed with whitish spots (mainly on lower flanks) and ventral surfaces predominantly zinc-yellow (RAL 1018).

In preservative, ground colour of dorsal surfaces of head and back of all specimens is dark shades of pastel-violet (RAL 4009), with dorsal surfaces of extremities light brown with dark brown stripes and spots. Two paratypes with and two without, light mid-dorsal line. Snout tip grey in all specimens. Part of chest, entire abdomen and ventral surfaces of thighs light ivory; throat and part of chest light ivory overlain by more or less expanded brown-beige areas. Rear of thighs in all type specimens predominantly brown, only a small area around vent blackish.

Distribution and ecological notes.

Xenorhina wiegankorum sp. nov. has a known distribution limited to altitudes of 330-950 m a.s.l. in the foothills of the upper Strickland River catchment in Western Province, south-western Papua New Guinea (Fig. 16 ). Males called at night from under the litter on the forest floor or from slightly beneath the soil surface, during or immediately after heavy rain.

Vocalisation.

We analysed one call series from the holotype (SAMA R71653) recorded at an air temperature of 23.7 °C, two call series from paratype SJR 10400 recorded at 21.0 °C and one call series of paratype ZMB 91132 recorded at 25.0 °C. Calls are rather deep, unpulsed “popping” notes that, as is typical for many Xenorhina species, increase in volume during the course of the call series. Pitch of calls also increases slightly during the course of each series. Although there is some variation in call length and inter-call interval amongst calls of the three animals recorded, there is high overlap in all call parameters and we have no doubt that all represent the same species. We, therefore, combined the calls for analysis

Calls are of approximately equal length, but inter-call intervals are somewhat variable. A call starts abruptly at high amplitude, which then decreases gradually until end of call (Fig. 14a ). There are 2-7 harmonics, though the second is often missing (Fig. 14b and c ); fundamental and dominant frequencies are at 0.55 kHz (Fig. 14c ). Length of call series is 13.8-18.1 s (mean 15.3 s, n = 4); with 22-39 calls per series (mean 28.8, n = 4); call length is 60-104 ms (mean 87.1 ± 6.7 ms, n = 115); intercall interval length is 286-1073 ms (mean 459.6 ± 137.6 ms, n = 111) with call repetition rate of 1.71-2.15 calls/s (mean 1.86 calls/s).

Etymology.

The specific epithet Xenorhina wiegankorum is the Latinised patronymic adjective in genitive plural of the family name Wiegank. It is given to recognise a very long-lasting friendship of the senior author with Ulla and Friedrich-Manfred (Conny) Wiegank from Potsdam.

Comparisons with other species.

We compare Xenorhina wiegankorum sp. nov. with all congeners of a similar size (SUL ~ 28-38 mm) that have a single spike on each vomeropalatine bone.

Xenorhina fuscigula has hind legs shorter (TL/SVL <0.40 vs.> 0.40), eye-naris distance shorter (END/SVL 0.064-0.074 vs. 0.070-0.084) and fourth toe shorter (T4L/SVL 0.34-0.41 vs. 0.45-0.47); advertisement calls of X. fuscigula are produced singly (vs. in a long series containing up to 39 calls).

Xenorhina huon (Blum & Menzies, 1989) has hind legs shorter (TL/SVL <0.40 vs.> 0.40), eyes larger (ED/SVL 0.070-0.091 vs. 0.062-0.066) and ventral surfaces with dark flecking (vs. ventral surfaces without dark flecking). Xenorhina huon is also known only from mountainous regions 1800-2000 m a.s.l. on the Huon Peninsula, near the north coast of Papua New Guinea (vs. lowlands south of the central cordillera).

Xenorhina lacrimosa exhibits considerable overlap in many morphometric characters, but displays extensive variation in dorsal colouration (vs. predominantly brown or grey); vent enclosed in dark brown patch (vs. patch absent) and ventral surfaces deep orange or occasionally grey-brown, with white spots (vs. ventral surfaces at least partially yellow) (Figs 1 - 2 vs. 12-13); dorsal surfaces also appear less rugose in life (Figs 1 - 2 vs. 12-13). Advertisement calls are very different: call series of X. lacrimosa much longer (26-60 s vs. 12-18 s), with fewer calls (7-12 vs. 22-39), repetition rate much slower (0.20-0.27 vs. 1.70-2.15 calls/s), call length longer (141-231 ms vs. 60 to 104 ms) and call interval longer (2.8-8.0 s vs. 286-1073 ms).

Xenorhina subcrocea (Menzies & Tyler, 1977) is smaller (SVL 30.5-33.3 vs. 32.0-35.7), with hind legs longer (TL/SVL> 0.46 vs. <0.47), ventral surfaces with dark reticulation in preservative (vs. without dark reticulation), call intervals within series shorter (154-285 ms vs. 286-1073 ms), produced at rate of about 4 calls/s (vs. 1.7-2.2 calls/s).

Xenorhina zweifeli has similar body size and ratios. It differs from Xenorhina wiegankorum sp. nov. by having a conspicuous dark brown supratympanic stripe (vs. absent) and greatly different advertisement calls: X. zweifeli utters single calls at long and irregular intervals ( Kraus and Allison 2002), with 2-3 calls sometimes uttered in quick succession, during the day and early evening ( Kraus and Allison 2002); in contrast, Xenorhina wiegankorum sp. nov. produces calls in discrete series with 22-39 calls produced in rapid succession, only at night.

Figures

Figure 1. Holotype (SAMA R 71648) of Xenorhina lacrimosa sp. nov. in life: (a) Dorsolateral view; (b) Ventral view; (c) Volar view of right hand; (d) Thenar view of right foot.

Figure 2. Xenorhina lacrimosa sp. nov. paratypes in life. Dorsolateral views: (a) SAMA R 65070; (b) ZMB 91129; (c) ZMB 91130; (d) SAMA R 71647. Ventral views: (e) SAMA R 65070 S; (f) ZMB 91129; (g) SAMA R 65071; (h) SAMA R 71647.

Figure 12. Holotype (SAMA R 71653) of Xenorhina wiegankorum sp. nov. in life: (a) Dorsolateral view; (b) Ventral view; (c) Volar view of left hand; (d) Thenar view of left foot.

Figure 13. Xenorhina wiegankorum sp. nov. paratype SAMA R 71654 in dorsolateral view.

Figure 14. (a) Oscillogram; (b) Spectrogram and (c) Amplitude spectrum of the last five calls from a call series containing 29 calls, produced by paratype ZMB 91132 of Xenorhina wiegankorum sp. nov.

Figure 16. Map of Papua New Guinea showing the known distributions of X. thiekeorum sp. nov. (blue circle), X. wiegankorum sp. nov. (yellow triangles) and X. woxvoldi sp. nov. (red square). Arrows indicate the type localities.