Nyctimystes hanwara, Richards, 2024

Nyctimystes hanwara , new species

( Figs 1–2 View Fig View Fig , 4 View Fig , 6 View Fig )

Holotype. SAMA R72452 (FN SJR10255 ). Adult male with nuptial pads, Baia River headwaters, Karius Range, Hela Province, Papua New Guinea (5.9910°S, 142.6767°E, 1,390 m a.s.l.), collected by S. Richards on 7 February 2008. GoogleMaps

Paratypes (n=6). PNGNM (FN SJR10258 ) , SAMA R72453– 72454 (FN SJR10256–10257 ) , R72456 (FN SJR10285 ) , and SAMA R72451 (FN SJR10231 ) , males with vocal slits, all with same collection details as holotype but R72451 collected on 6 February 2008 and R72456 collected on 9 February 2009; SAMA R72455 (FN SJR10259 ) , adult female, same collection details as holotype.

Diagnosis. Assigned to Nyctimystes on the basis of having a vertical pupil, prominent palpebral reticulum, and large unpigmented eggs ( Kraus, 2013). The new species can be distinguished from all congeners by the following unique combination of characters: size moderate (male SVL 38.5– 43.5 mm, sole female 52.9 mm); finger webbing reduced, not extending beyond distal subarticular tubercle on Fingers 3 and 4; toe webbing extensive, extending beyond distal subarticular tubercle on both sides of Toe 4; finger and toe discs prominently expanded (3FD/SVL 0.055 –0.064; 4TD/ SVL 0.052 –0.061), those on Finger 3 same size or slightly larger than those on Toe 4 (3FD/4TD 1.00-1.15); palpebral venation forming thick gold (in life) reticulate pattern without obvious vertical or horizontal orientation; lateral edges of forearm and hindlimb with row of low but distinct tubercles, 1–4 small tubercles on each heel; dorsal colouration in life mottled pale russet and dark brown, or brown with yellow and darker-brown to black spots; and call comprising 1–3, but most commonly two, rapidly repeated notes produced at intervals of approximately 1–10 seconds for long periods.

Description of holotype. An adult male with vocal slits and nuptial pads. Measurements are presented in Table 1. Habitus slender ( Fig. 1A View Fig ), head moderately wide (HW/SVL 0.32), slightly narrower than long (HL/SVL 0.34; HW/HL 0.93). Snout broadly rounded in dorsal view, except at tip where distinct swelling forms short protuberance in dorsal view ( Fig 2A View Fig ), narrowly rounded and distinctly protruding in lateral view ( Fig. 1A View Fig ); canthus rostralis sharp, nearly straight, loreal region sloping, distinctly concave, nostrils closer to tip of snout than to eyes, oriented laterally; internarial distance greater than distance from external naris to eye (EN/ IN 0.94). Eyes moderately large (EYE/SVL 0.12), barely protruding in dorsal view ( Fig. 2A View Fig ). Tongue broadly oval, nearly round, with shallow posterior notch. Paired vocal slits laterally in floor of mouth extend anteriorly from point approximately level with angle of jaw to half-way to tip of snout. Vomeropalatines with two patches of 4–5 low, poorly defined teeth, each elevation approximately 1.5 mm across the longest axis, angled posteromedially from about midway between choanae where they are separated by 2.0 mm, to about 0.8 mm behind posterior edge of choanae where of Finger 3 and outside of Finger 2, restricted to basal fringe between Fingers 1 and 2 ( Fig. 2B View Fig ). Subarticular tubercles prominent, distal tubercles on Fingers 1, 3 and 4 partially lobed, remainder unilobed, circular. Inner plantar tubercle prominent, ovoid; outer plantar tubercle low but distinct, nearly circular ( Fig. 2B View Fig ). Nuptial pads low, brown, finely granular, extending 3.0 mm distally from base of Finger 1.

Hind limbs long (TL/SVL 0.57), toes moderately short, relative lengths 4>5>3>2>1 on left foot, Toes 3 and 5 subequal on right foot, terminal discs prominently expanded (4TD/SVL 0.058; 4TD/4TP 1.56) with circum-marginal grooves ( Fig. 2C View Fig ); toes extensively webbed, web reaching to base of disc on Toes 1–3 and inside of Toe 5, and to midway between distal subarticular tubercle and disc on both sides of Toe 4 ( Fig. 2C View Fig ). Subarticular tubercles prominent, not divided or at most with shallow indentation in midline; inner metatarsal tubercle small, narrow; outer metatarsal tubercle poorly defined, barely detectable.

they are just 0.3 mm apart. Tympanum small (EAR/SVL 0.046), less than half width of eye (EAR/EYE 0.39), annulus narrow but clearly defined, except dorsal edge obscured by strong, nearly straight supratympanic fold extending from posterior edge of eye to above arm insertion; posterior edge of annulus of right tympanum less clearly defined than that of left tympanum.

Skin finely shagreened dorsally without prominent tubercles, finely but more distinctly granular around tympana; skin above arm insertion and posterior to supratympanic fold strongly tuberculate; ventral surfaces, including of thighs, coarsely granular except throat striated; ventral surfaces of tibiae and feet smooth; tubercles below vent prominent; posteroventral edge of forearm with single row of small but distinct tubercles transitioning to low, slightly serrated dermal ridge along outer edge of fourth finger; posteroventral edge of tarsus with low, serrated dermal ridge, transitioning to straight-edged ridge along outer edge of fifth toe; each heel with 2–4 small tubercles.

Fingers moderately long, relative lengths 3>4>2>1, terminal discs prominently expanded (3FD/SVL 0.062; 3FD/3FP 1.80), with circum-marginal grooves ( Fig. 2B View Fig ). Fingers slightly more than one-quarter webbed, web reaching to base of distal subarticular tubercle on inner side of Finger 4 and just short of base of distal subarticular tubercle on outside of Finger 3, to base of proximal subarticular tubercle on inside In life, dorsal surfaces mottled pale russet and darker brown, dark-brown areas concentrated on top of head and in scapular region, these overlain by fine grey stippling; some patches on mid dorsum orange brown, those on dorsal surfaces of limbs grey brown ( Fig. 1A View Fig ); mottled dorsal surfaces overlain with scattered fine, grey, lichenose pigment patterns; lateral surfaces of head orange grey, paler than adjacent dorsum, these paler areas of head sharply delineated from darker dorsal surfaces along canthus rostralis ( Fig. 1A View Fig ); remaining lateral surfaces grey, overlain with small creamy blotches; tubercles along outer edges of forearms and tarsi, large tubercles below vent, and dermal folds along edges of hands and feet all cream. Ventral surfaces white, hidden surfaces of thighs grey. Palpebral venation gold ( Fig. 1D View Fig ).

In preservative, ground colour of dorsum pale ivory brown with grey and dark-brown patches ( Fig. 2A View Fig ), grey elements within dark brown patches more prominent than in life; lichenose spots grey; dorsal surfaces of fingers and toes ivory with grey patches; ventral surfaces white.

Variation. Snout-vent length of adult males with well-developed nuptial pads and vocal slits ranges from 38.5–43.5 mm ( Table 1). The smallest specimen ( SAMA R72451 ; 36.4 mm SVL) is a male with short vocal slits but without nuptial pads and is possibly just maturing; the largest specimen ( SAMA R72455 ; 52.9 mm SVL) is the only adult female in the series. None of the paratypes has the short protuberance at the tip of the snout exhibited by the holotype ( Fig 1A View Fig vs. 1B–C). Leg length is rather variable, with TL/ SVL ranging from 0.53–0.60, but otherwise morphometric variation among the type series is limited ( Table 1). Palpebral venation of all specimens was gold in life and formed a thick reticulum without obvious vertical or horizontal orientation. All specimens have at least one, and as many as four, small but distinct tubercles on each heel. All specimens were predominantly brown dorsally in life but the extent of darker and lighter mottling, and presence of grey lichenose pigment patches and yellow or dark-brown to black spots was highly variable ( Fig. 1A–C View Fig ). SAMA R72453 was more analysis due to the loud background noise of the flooding stream and heavy rainfall. However, I provide general comments on their structure to support the call description where relevant. The call of Nyctimystes hanwara , new species is a pair of rapidly repeated, distinctly pulsed notes ( Fig. 4 View Fig ) produced in series lasting at least several minutes; recording conditions precluded more extended observations. The three consecutive calls produced by the holotype were 8.4 and 10.8 seconds apart but some unvouchered males were producing calls as frequently as every 1–2 seconds. Calls produced by the holotype are 0.36– 0.40 s long, the first note is longer (0.17–0.23 vs. 0.08– 0.10 s) and softer than the second note and notes within calls are separated by intervals of 0.07– 0.08 s. All notes are distinctly pulsed, producing a rasping sound, but first notes are more finely pulsed than second notes in a couplet ( Fig. 4 View Fig ). Furthermore, amplitude increases gradually before decreasing rapidly at the end of the first note, producing a ‘buzz’ sound, while amplitude increases and decreases rapidly at the start and end of second notes producing a more explosive ‘chick’ sound. It was not possible to count all pulses in any of the first notes due to their fine structure and background noise, but pulse rates calculated from the best 0.07 s segments extracted from two first notes were nearly three times as fast (357 and 385 vs. 112–128 pulses/s) as those from three second notes. Dominant frequency of the three calls is 2750–2850 Hz, and there is no consistent difference in dominant frequency between first and second notes .

uniformly brown dorsally than the holotype, with scattered large, discrete orange-brown patches, lateral surfaces more white than grey, and side of face grey rather than orange grey ( Fig. 1B View Fig ). SAMA R72451 was uniform pale brown with yellow and dark-brown to black spots dorsally, the latter also extending onto dorsal surfaces of limbs ( Fig. 1C View Fig ). Very dark-brown to black spotting on the dorsum is most conspicuous on SAMA R72452 and is also present, to a lesser extent, on the female SAMA R72455 . The pale, lichenose pigment patches are most conspicuous on the holotype and on PNGNM ( SJR 10285 ); they are absent or barely detectable on the remaining specimens. Distinct barring is absent from hidden surfaces of the thighs of all specimens. All of these colour-pattern differences remain visible in preservative .

Advertisement call. I recorded calls produced by several males along a turbulent, fast-flowing stretch of the upper Baia River ( Fig. 3A–B View Fig ) in heavy rain at an air temperature of 19°C. Three consecutive calls produced by the holotype (R72452) are described below; it was not possible to confidently associate calls from more distant individuals with voucher specimens, and they are of insufficient quality for detailed Of 55 additional calls recorded from a distance of more than 5 m in heavy rain, 44 (80%) were produced in couplets like the holotype, nine (16%) appeared to comprise a single note, and two (4%) were triple notes. However, first notes were always softer than second notes and it is possible that some apparent single-note calls were couplets in which the first note was not detected. Additional variation in these calls involves the relative length and pulse structure of the first note, which in a small number of couplets appears to be of equivalent length (vs. longer) to the second note and to have a similar, more coarsely pulsed structure. Unfortunately, the quality of recordings precluded more detailed analysis of this variation.

Comparisons with other species. Nyctimystes hanwara , new species, differs from all congeners for which the call is known, except N. bivocalis , by having an advertisement call comprising two rapidly repeated notes (vs. calls not biphasic). It further differs from N. avocalis Zweifel, 1958 , N. disruptus Tyler, 1963a , N. oktediensis Richards & Johnston, 1993 , N. papua ( Boulenger, 1897) , N. trachydermis Zweifel, 1983 , and N. tyleri Zweifel, 1983 in having (vs. lacking) vocal slits in males; from N. cryptochrysos Kraus, 2012 , N. foricula Tyler, 1963a , N. granti ( Boulenger, 1914) , N. gularis Parker, 1936 , N. humeralis ( Boulenger, 1912) , N. kubori Zweifel, 1958 , N. kuduki Richards, 2007 , N. montanus ( Peters & Doria, 1878) , N. narinosus Zweifel, 1958 , N. persimilis Zweifel, 1958 , and N. zweifeli Tyler, 1967 in having (vs. lacking) at least one distinct tubercle on the heel; from N. calcaratus Menzies, 2014 and N. cheesmani Tyler, 1964 in its smaller size (male SVL 38.5–43.5 vs. 43.0–52.0 mm in calcaratus and 47.6–56.5 mm in cheesmani ), palpebral venation of thick lines forming dense reticulum (vs. thinner, obliquely oriented lines with few cross connections); from N. daymani Zweifel, 1958 in its shorter snout (EN/IN 0.94–1.13 vs. 1.17–1.39; Kraus, 2012a), and palpebral venation of thick lines forming dense reticulum (vs. thin, obliquely oriented lines with few cross connections; from N. eucavatus Menzies, 2014 in having palpebral venation of thick lines forming dense reticulum without obvious orientation (vs. thick gold palpebral venation oriented obliquely with few cross connections), and less extensively webbed fingers (webbing not extending beyond base of distal subarticular tubercle on Finger 4 (vs. webbing extending beyond distal subarticular tubercle); from N. intercastellus Kraus, 2012 in having palpebral venation of thick lines forming dense reticulum without obvious orientation (vs. venation predominantly vertical but with many horizontal cross connections; from N. latratus Menzies, 2014 and N. traunae Menzies, 2014 in having palpebral venation of thick lines forming dense reticulum (vs. thinner, obliquely oriented lines with few cross connections). It further differs from N. latratus in its smaller size (male SVL 38.5–43.5 vs. 42.0–51.0 mm); from N. myolae Menzies, 2014 in its smaller size (male SVL 38.5–43.5 vs. 46.0–51.0 mm) and white venter (vs. “pinkish-white, speckled grey all over”; Menzies, 2014); from N. ocreptus Menzies, 2014 by its higher EN/IN values (0.94–1.13 vs. 0.73–0.84), near-smooth (vs. warty) dorsum and uniformly grey (vs. with distinct yellow spots) hidden surfaces of thighs; from N. obsoletus Lönnberg, 2019 , in having a distinct tympanum (vs. not visible); from N. pulcher Wandolleck, 1911 in its smaller size (male SVL 38.5–43.5 vs. males to 65 mm) and small tubercle (vs. large, triangular lappet) on heel; from N. fluviatilis Zweifel, 1958 in lacking bright orange on rear of thighs (vs. present); from N. perimetri Zweifel, 1958 , in its smaller size (male SVL 38.5–43.5 vs. males to 61 mm), shorter snout (EN/IN 0.94–1.13 vs. 1.23–1.56; Kraus, 2012a) and lacking yellow on hidden surfaces of the thighs; from N. semipalmatus Parker, 1936 in having rear of thighs grey (vs. uniform bright orange), lacking tiny black spots across the dorsum (F. Kraus, pers. comm.), and less finger webbing (not extending beyond base of distal subarticular tubercle on Finger 4 vs. extending to or beyond distal subarticular tubercle; Kraus, 2012a).

The only other species of Nyctimystes known to have a biphasic advertisement call is N. bivocalis , and that species is also morphologically similar to N. hanwara , new species. However, the new species differs from N. bivocalis , a species restricted to the easternmost portion of Papua New Guinea’s southeast peninsula ( Fig. 5 View Fig ) in its less extensive hand webbing (web reaching no further than base of distal subarticular tubercle on fourth finger vs. extending to middle of or beyond distal subarticular tubercle), and in having palpebral venation of thick lines forming a dense reticulum without obvious orientation (vs. thinner lines with vertical to oblique orientation and few cross connections; Fig. 6 View Fig ).Furthermore, although both species produce biphasic calls in long series there are differences between their calls. Those of N. hanwara , new species are shorter (0.36– 0.40 s vs. 0.44– 0.52 s), pulsed (vs. unpulsed), have a higher dominant frequency (2750–2850 vs. 1560–1720 Hz) and appear to be produced at a much slower rate (~0.1–0.5 vs. 1.05-1.44 calls/s) than those of N. bivocalis ( Kraus, 2012a) .

Distribution and natural history. Nyctimystes hanwara , new species, is known only from the type locality at an altitude of 1,390 m a.s.l. at the base of the Karius Range in Hela Province, central mainland Papua New Guinea ( Fig. 5 View Fig ). Adult males called from foliage 2–3 meters above the ground, or from high in trees, in lower montane forest along a narrow (~ 5 m wide; centre-background of Fig. 3B View Fig ) section of a fast-flowing rocky stream that is part of a complex of streams and swamps forming the headwaters of the Baia River. The female contains large yellow eggs; five eggs measured in situ were 1.9–2.2 mm in diameter (mean = 2.1, SD = 0.11). No animals were seen or heard where the stream broadened (to> 10 m wide) downstream.

Other torrent-breeding treefrogs found along the same stream were Litoria angiana ( Boulenger, 1915) , L. arfakiana ( Peters & Doria, 1878) , L. micromembrana ( Tyler, 1963b) , and L. modica ( Tyler, 1968) . A torrent-breeding Papurana Dubois, 1992 species was also encountered along streams at the type locality.

Suggested IUCN Conservation Status. Nyctimystes hanwara , new species, is known only from a single location and, although the region is topographically rugged ( Fig. 3A View Fig ) and human population density is low, potential threats to this species are unknown. Until data are available to better assess this species’ distribution, habitat requirements and any threats, its conservation status should be considered Data Deficient.

Etymology. The name hanwara is Melanesian pidgin for stream and refers to this species’ occurrence along forest streams.