Kikori torrent treefrog

SAMA R69990 (SJR[JCUNQ]3245), adult male with vocal slits and nuptial pads, calling when collected, Libano Sok, Hegigio River, Southern Highlands Province, Papua New Guinea (6.3989°S, 142.9761°E; 250 m a.s.l.), collected by Stephen Richards on 7 August 2003.

SAMA R69986 (SJR[JCUNQ]3222), R69987 (SJR[JCUNQ]3240), R69988 (SJR[JCUNQ]3243), R69989 (SJR[JCUNQ]3244, R69991–R69992 (SJR[JCUNQ]3246–3247), QMJ 98371 (JCUNQ[SJR]3241), PNGNM JCUNQ[SJR]3242), all males with same locality and collector details as holotype, collected between 4–7 August 2003; SAMA R72336 (SJR14135), male, and R72337 (SJR14141), female, Bifo Creek, Southern Highlands Province, Papua New Guinea (6.4483°S, 142.9597°E; 360 m a.s.l.), collected by Stephen Richards on 2 and 4 August 2014 respectively.

A species of Litoria that can be distinguished from all congeners by the following unique combination of characters: size moderate (male SVL 29.9–35.8); snout moderately long (EN/IN 0.51–0.75), slightly pointed in dorsal view, truncate in lateral view; canthus rostralis curved in dorsal view, relatively sharply defined in lateral view; limbs long (TL/SVL 0.59–0.68); finger webbing moderate, extending to distal subarticular tubercles between fingers 3 and 4; toe webbing extensive, reaching to disc or to intercalary cartilage at base of disc on all digits except toe 4; finger and toe discs moderately narrow (3FD/SVL 0.04–0.05, 4TD/SVL 0.04–0.05); dorsal skin finely rugose with numerous larger tubercles on exposed surfaces of torso; hindlimbs with low, crenulated dermal ridges on outer edges of tibiae and tarsi; heels with 2–3 low conical tubercles; vomerine teeth in two prominent raised clumps; vocal slits present in males; dorsal colouration mottled green and brown; hidden surfaces of shanks and groin purplish in life; and advertisement call a single loud, unpulsed musical note lasting 0.03–0.05 s and produced at intervals of ~12–37 seconds for long periods.

We emphasize comparisons with torrent-breeding Litoria because based on taxa genetically sampled so far (e.g., Richards et al. 2021, 2023) they form a monophyletic group that is also ecologically distinctive. The new species can be distinguished from non torrent-breeding Litoria by the following combination of characters: dorsum mottled green and brown, skin tuberculate (Fig. 1A–C), canthus rostralis strongly curved and moderately sharply defined in dorsal view, snout-tip shallowly acuminate, webbing on fingers moderate, extending to distal subarticular tubercles on outside of fingers 2 and 3, and adult size moderate (male SVL 30–36 mm).

Litoria kikorisp. nov. can be distinguished from other torrent-breeding Litoria in New Guinea as follows: it is larger than L. amnicola Richards, Tjaturadi, Krey & Donnellan, 2021, L. brongersmai (Loveridge, 1945), L. lakekamu Richards & Bickford, 2023, L. leucova (Tyler, 1968), L. megalops Richards & Iskandar, 2006, L. napaea (Tyler, 1968), L. rara Günther & Richards, 2005 and L. rivicola Günther & Richards, 2005 (male SVL > 30 mm versus < 25 mm); and further differs from L. amnicola, L. brongersmai, and L. napaea in having prominent vomerine teeth (versus indistinct, detectable only as slight bumps); from L. lakekamu and L. leucova in its green-and-brown-mottled dorsum (versus green); from L. megalops in having moderate finger webbing (versus absent), and in its smaller eye (EYE/SVL 0.12–0.14 versus 0.14–0.17); and from both L. rara and L. rivicola by its longer hindlimbs (TL/SVL > 0.59 versus < 0.56) and green or brown dorsal colouration (versus predominantly grey or greyish brown). Litoria kikorisp. nov. is substantially smaller than L. angiana (Boulenger, 1915) (max male SVL <40 mm versus >50 mm), and further differs in having the snout distinctly acuminate (versus relatively blunt) in dorsal aspect, canthus rostralis curved in dorsal view (versus straight), and dorsum and lateral edge of tarsus strongly tuberculate in life (versus relatively smooth).

Litoria kikorisp. nov. differs from the following ten similar-sized or slightly larger torrent-breeding species – L. arfakiana (Peters & Doria, 1878), L. becki (Loveridge, 1945), L. bulmeri (Tyler, 1968), L. oenicolen Menzies & Zweifel, 1974, L. fuscula Oliver & Richards, 2007, L. macki Richards, 2001, L. micromembrana (Tyler, 1963), L. modica (Tyler, 1968), L. spinifera (Tyler, 1968) and L. wollastoni (Boulenger, 1914) – in having moderately extensive finger webbing that extends to distal subarticular tubercle on fingers 2, 3, and 4 (versus at most basal webbing between fingers 3 and 4); and further differs from L. arfakiana, L. oenicolen, L. spinifera and L. wollastoni in its less sharply acuminate snout tip and lacking prominent spiniform tubercles on heel (and in L. spinifera across body); from L. becki in its extensively webbed toes (versus toes half-webbed); from L. bulmeri by lacking a dark brown to black lateral band on head and body (versus present); from L. fuscula in having prominent vomerine teeth (versus indistinct, detectable only as slight bumps), green and/or brown mottled dorsal colouration (versus dark brown with no obvious pattern), and in having small conical tubercles along heel (versus no tubercles); and from L. macki in having low, indistinct tubercles on eyelids (versus prominent and large) and dark purplish-brown colouration in groin (versus yellow).

Litoria kikorisp. nov. can be distinguished from four similar-sized species with moderate webbing between the fingers as follows: from L. dorsivena (Tyler, 1968) and L. hastula Oliver, Iskandar & Richards, 2023 by its green-and-brown mottled dorsal colouration (versus predominantly brown) and snout relatively rounded in lateral view (versus distinctly acuminate in both lateral and dorsal views); from L. pratti (Boulenger, 1911) by its curved canthus rostralis (versus straight) and slightly longer limbs (TL/SVL > 0.59 versus < 0.57); and from L. scabra Günther & Richards, 2005 by its longer limbs (TL/SVL > 0.59 versus < 0.56), hindlimbs with series of low lateral tubercles (versus a crenulated ridge), and green or green-and-brown mottled dorsal colouration (versus predominantly grey or greyish brown) (Günther and Richards 2005).

Litoria kikorisp. nov. is most similar to L. spartacus Richards & Oliver, 2006 (Fig. 2A) and is closely related to it (see below), but can be differentiated by its smaller size (male SVL 29.9–35.8 versus 35.6–37.4, female SVL 45.4 versus 51.1), narrower finger pads (3FD/SVL 0.045–0.052 versus 0.048–0.062), narrower toepads (4TD/SVL 0.037–0.050 versus 0.052–0.062) (Fig. 2B), distal subarticular tubercle of finger 4 wider than long and slightly bifid (versus roughly equal in width and length and not bifid) (Fig. 2B), groin in life unpigmented or light purplish (versus orange) (Fig. 2C–E), throat in males without brown mottling (versus typically with brown mottling) and call consisting of a single note repeated at 12–37 second intervals for at least several minutes (versus multiple notes in short series lasting 5–20 seconds; Richards and Oliver 2006).

Adult male with vocal slits and indistinct pale-brown nuptial pads with fine asperities. Habitus moderately slender, limbs long (TL/SVL 0.67), head wide (HW/SVL 0.36). Snout protruding distinctly beyond lower jaw, rounded in lateral view, moderately acuminate in dorsal view (Fig. 3A, B). Canthus rostralis with rounded edge, but clearly defined in both dorsal and lateral view and curved in dorsal view; loreal region steeply sloping, slightly concave. Nostrils near top of snout, oriented laterally, not visible in dorsal view. Vomeropalatines forming two prominent elevations, each with 3–4 teeth positioned midway between choanae. Tongue small, nearly round, with prominent posterior notch; vocal slits laterally in floor of mouth, extending from near angle of jaws about one half distance to front of jaw. Eyes large (EYE/SVL 0.14), prominent, protruding in dorsal and ventral views; pupil horizontal, pigmentation on nictitating membrane restricted to very thin narrow band of maculations along dorsal edge. Tympanum moderately small (TYM/SVL 0.05), one-third diameter of eye (TYM/EYE 0.32), tympanic annulus clearly defined, except dorsal edge obscured by thick, slightly curved supratympanic ridge.

Skin on dorsal surfaces of torso and head rugose, with numerous large, rounded tubercles (Fig. 3A), skin on throat finely granular, on abdomen coarsely granular. Forelimbs finely tuberculate on exposed surfaces, with scattered tubercles on ventral surface, and distinct ventrolateral fold along outer edge of forearm. Hindlimbs tuberculate on exposed dorsal surfaces of tibia and tarsus, outer edge of tibia and tarsus with series of tubercles (Fig. 3C), heel with three low white tubercles. Ventral surfaces of thighs coarsely granular proximally, becoming less so distally, ventral surfaces of tarsus and tibia smooth.

Fingers long, relative lengths 3>4>2>1. All fingers webbed (Fig. 3D), in thin strip between fingers 1–2, and extending to distal subarticular tubercles on outside of fingers 2 and 3, and inside of finger 4 (Figs 2B, 3D). Tips of all digits expanded into prominent discs (3FD/3FP 1.6) with circum-marginal grooves. Subarticular tubercles rounded or bifid, distal tubercles of fingers 3 and 4 most notably bifid (Fig. 3D); outer metacarpal tubercles ovoid, indistinct; inner metacarpal tubercle prominent, visible as lunate lateral extension from base of finger 1 in both ventral and dorsal view. Nuptial rugosity on outer metacarpal tubercle finely granular, indistinct.

Toes long, relative lengths 4>3>5>2>1, all webbed (Fig. 3E); web reaching to terminal disc or to intercalary cartilage at base of disc on toes 1, 2, 3 and 5 and to distal subarticular tubercle on both sides of toe 4. Discs prominent (4TD/4TP 1.6), with supramarginal grooves. Subarticular tubercles prominent, rounded or slightly bifid (Fig. 3E); inner metatarsal tubercle indistinct and ovoid, outer metatarsal tubercle slightly smaller, indistinct and rounded.

Dorsal surfaces predominately dark blueish green with small areas of dark brown (Fig. 3A); lateral surface of snout predominately brown, with diffuse blueish green blotch extending anteriorly from lower edge of eye; prominent brown blotch below supratympanic fold; labial region with numerous small white spots; upper lips and region around rictus of jaws white (Fig. 3B). Ventral surfaces largely off white, with some tiny brown maculations along edge of jaw. Dorsal surfaces of arms and legs predominately greenish brown, towards extremities brown colouration becomes more diffuse and off-white ground colouration becomes more visible. Most ventral surfaces of limbs largely off white with scattered patches of brown, particularly on hands, lateral edge of arms and femur; tarsi and feet (including webbing) off white, heavily spotted with brown.

Measurements and proportions of males in the type series are similar (Table 1) and all paratypes have similar webbing on the hands and feet. Dorsal colour pattern is variable, ranging from bluish green heavily mottled with dark brown, through to predominantly greyish-brown with a small amount of blueish-green splotching. Ventral colouration is consistently off white to buff, with only slight variation in the extent of light-brown mottling on the legs and along the sides of the torso. The single female is substantially larger than the males in the type series (Table 1) and has more extensive greyish-brown mottling on the ventral surfaces but is otherwise similar in colouration and proportions.

The following description of colouration in life is based on photographs of three specimens (Figs 1A–C, 2D, E). Dorsal surfaces of torso, snout, forelimbs and most exposed surfaces of hindlimbs mottled with medium brown and bright green, with relative extent and dominance of green and brown areas showing considerable variation across specimens. Exposed surfaces of thigh light brown without green pattern. Tympanum always brown. Posterior edge of upper jaw usually with at least some small off-white blotches. Lateral surfaces of body sometimes with large ragged-edged silvery-yellow blotches. Where portions of venter are visible in photos (2D) they are translucent, but heavily overlaid with white spots and brown maculations. Hidden posterior edge of thighs, shanks and inguinal region purplish. Tubercles around vent white. Iris silver with thin dark-brown vermiculations.

We recorded 13 calls from four individuals. Calls were similar among all individuals and were combined for analysis. The call of Litoria kikorisp. nov. is a single loud, musical note, sounding like ‘tink’, uttered from leaves and branches between 2 and >5 m above the banks of large foothill streams. Calls are 0.03–0.05 s long (mean = 0.04, SD = 0.008, n = 13); notes are not pulsed, but two notes are partially divided into two subpulses. Frequency is concentrated in two bands, one at about 3600 Hz and the other at 1800 Hz (Fig. 4). The higher band is dominant in 11 calls (3460–3660 Hz, mean = 3600, SD = 58.32) while the lower frequency was dominant in two calls produced by SAMA R69992. Calls were produced at 0.38–37.0 seconds. However, if a single rapidly repeated couplet produced by SAMA R69991 (0.38 s interval) is excluded then inter-call interval is 11.9–37.0 seconds (mean = 17.8, SD = 8.0 s, n = 8). Males produced these single-note calls in bouts lasting for at least several minutes. An exemplar call from paratype SAMA R72336 has been uploaded to iNaturalist (https://www.inaturalist.org/observations/218063325).

Genetic divergences (p-distances) between Litoria kikorisp. nov. and its closest relative L. spartacus were between 0.135–0.146 (based on comparisons of 654bp of mitochondrial ND4 gene data).

Named in reference to the Kikori River basin to highlight the remarkable frog diversity and broader conservation significance of this region. Used as a noun in apposition.

Known only from two locations, Libano Sok and Bifo Creek, located 6 km apart in the Kikori River basin along the southern slopes of the Central Cordillera of Papua New Guinea (Fig. 5).

Males in the type series were calling from leaves between 2–4 metres above swift-flowing rivers in hill forest (Fig. 6A). The female paratype (SAMA R72337) was collected from a tree adjacent to Bifo Creek. Five large, yellow eggs measured in situ were 1.7–2.0 mm diameter in diameter. At Libano Sok Litoria kikorisp. nov. occurred in sympatry with one other torrent-breeding pelodryadid frog, the new species described below. No other torrent-dwelling Litoria were detected at Bifo Creek.

Litoria kikorisp. nov. is known only from two sites approximately six kilometres apart. However, there are large areas of forest in the region, which is sparsely inhabited. Furthermore, it occurs at elevations at which ecologically similar torrent-breeding Litoria in tropical Australia have been able to persist in the presence of the frog pathogen B. dendrobatidis. Despite its small range, and uncertainty about the species’ ability to persist if intensive logging occurs, we suggest that this species should be considered Least Concern at this stage. However, we stress that further surveys are needed to better document this species’ distribution and the extent to which it overlaps with areas of forest loss.

Green torrent treefrog

SAMA R72339 (SJR10513), adult male with vocal slits and nuptial pads, Liddell River, upper Strickland River basin, Western Province, Papua New Guinea (5.8078°S, 142.3083°E; 215 m a.s.l.), collected by Stephen Richards on 30 March 2008.

SAMA R72340 (SJR[JCUNQ]3249), adult male with vocal slits and nuptial pads, Libano Sok, Hegigio River, Southern Highlands Province, Papua New Guinea (6.3989°S, 142.9761°E; 250 m a.s.l.), collected by Stephen Richards on 7 August 2003.

A species of torrent-breeding Litoria that can be distinguished from all congeners by the following unique combination of characters: size moderately small (male SVL 26.1–27.5 mm); snout rounded in both dorsal and lateral view; canthus rostralis strongly curved in dorsal view, rounded in lateral view; limbs long (TL/SVL 0.62–0.64); finger webbing moderate, web between fingers 3 and 4 extending to distal subarticular tubercle and, on finger 4, continuing as fringe to base of disc; toe webbing extensive, extending to base of disc on all toes except toe 4 where it reaches distal subarticular tubercle on both sides of digit; dorsal skin relatively smooth with no prominent tubercles; vocal slits present in males; dorsal colouration predominately mid-green with no or little pattern; thin brown canthal stripe or blotch present; hidden surfaces of thighs and groin orange; venter largely off-white with no pattern; and advertisement calls comprising 7–21 rapidly repeated unmusical tapping notes produced at a rate of 7.8–9.6 notes/s at a dominant frequency of 2707–3082 Hz.

The combination of moderately small size (adult male SVL between 25–30 mm), snout rounded in dorsal view, dorsal skin relatively smooth with no prominent tubercles, moderate webbing on the fingers and predominantly green dorsal colouration (Fig. 7A, B) readily distinguishes L. grinpelasp. nov. from the majority of other torrent-breeding Litoria from New Guinea.

Litoria grinpelasp. nov. differs from other small, green, torrent-breeding species as follows: from L. lakekamu Richards & Bickford, 2023 in its larger size (male SVL >25 versus <25 mm), white labial patch restricted to below eye only (versus full labial stripe), brown canthal stripe or patch present (versus absent), canthus rostralis moderately well defined (versus very indistinct), tympanum distinct (versus indistinct), and call consisting of 7–21 rapid popping notes (vs. a series of short, distinctly pulsed rasping notes followed by an explosive chattering; Richards and Bickford 2023); from L. leucova (Tyler, 1968) in its slightly larger size (adult male SVL >25 versus <25 mm), in having longer hindlimbs (TL/SVL > 0.62 versus < 0.57), a wider head (HW/SVL 0.36 versus 0.32–0.34), shorter snout (EN/SVL < 0.084 versus > 0.095) and yellow patches in groin and on hidden surfaces of thighs (versus translucent pink with yellow spots) (Johnston and Richards 1994); and from populations of the geographically overlapping L. longicrus (Boulenger, 1911) (Fig. 7C, D) by its slightly larger size (adult male SVL >25 versus <25 mm), plain green dorsum (versus mottled brown and green), green (versus brown) tympanic membrane, white lateral patch restricted to posterior edge of lower jaw (versus white patches extending from lower jaw along side of body almost to groin), and more extensive webbing on fingers (extending beyond distal subarticular tubercle on finger 4 versus not extending beyond distal subarticular tubercle on finger 4).

Litoria grinpelasp. nov. can be distinguished from three other species of moderately small, green lentic-breeding Litoria that occur in the Kikori region as follows; from L. auae Menzies & Tyler, 2004 by having a brown canthal stripe or blotch on the snout only (versus a white or yellow canthal stripe, and supratympanic stripe), in lacking white or yellow flecks on the dorsum (versus typically present), and by its slightly smaller size (male SVL < 28 mm versus typically greater than 30 mm); and from two species in the L. bicolor (Gray, 1842) group (L. chloristona Menzies, Richards & Tyler, 2008 and L. viranula Menzies, Richards & Tyler, 2008) by its broader head and more broadly rounded snout, the presence of a brown canthal stripe or blotch restricted to the head (versus brown and white lateral stripes extending along sides of torso) and its medium-green dorsal colouration (versus typically yellowish green or brown).

Adult male with vocal slits and pale-brown nuptial pads made up of fine asperities. Habitus moderately robust, limbs long (TL/SVL 0.64), head wide (HW/SVL 0.48). Snout protruding beyond lower jaw, slightly rounded (nearly truncate) in lateral view, rounded in dorsal view (Fig. 8A, B). Canthus rostralis clearly defined, strongly curved in dorsal view, rounded in lateral view; loreal region steeply sloping, slightly concave. Nostrils near top of snout, oriented laterally, not visible in dorsal view. Vomeropalatines poorly developed, detectable but teeth insufficiently developed to count. Tongue rounded with prominent posterior notch; vocal slits laterally in floor of mouth, extending from near angle of jaws about one third distance to front of jaw. Eyes large (EYE/SVL 0.12), prominent, protruding in dorsal and ventral views; pupil horizontal, nictitating membrane unpigmented. Tympanum moderately small (TYM/SVL 0.047), less than half diameter of eye (TYM/EYE 0.39), tympanic annulus clearly defined except dorsal edge obscured by moderately thick, slightly curved supratympanic ridge.

Skin on dorsum finely rugose, on dorsal surfaces of limbs largely smooth except for scattered indistinct tubercles on forearms; skin on throat finely granular, on abdomen coarsely granular. Ventral surfaces of forelimbs smooth with scattered tubercles; ventral surfaces of thighs coarsely rugose along posterior edge, becoming less so on adjacent surfaces, with scattered large pale off-white tubercles below vent; tarsi and tibiae smooth ventrally.

Fingers moderately long with expanded terminal discs (3FD/3FP 1.6; 3FD/SVL 0.058) with distinct circum-marginal grooves; relative lengths of fingers 3>4>2>1, subarticular tubercles unilobed or weakly bifid. Webbing moderate (Fig. 8C), reaching distal edge of distal subarticular tubercle and continuing to disc as narrow fringe on inside of finger 4; to base of distal subarticular tubercle on outside of finger 3; to base of penultimate subarticular tubercle on inside of finger 3; to base of distal subarticular tubercle on outside of finger 2; and in a narrow basal flange between fingers 1 and 2. Hands with long (1.3 mm) prominent ovoid inner metacarpal tubercles and shorter (0.5 mm), rounded and lower, but still distinct, outer metacarpal tubercle. Nuptial pads pale brown, comprising fine asperities, extending across base of finger 1, elongate, much longer that high, with distinct constriction demarcating short distal portion from much longer proximal portion.

Toes with expanded terminal discs with terminal grooves, some discs slightly shrivelled in preservative; disc on toe 4 distinctly narrower than disc on finger 3 (3FD/4TD 1.2). Relative lengths of toes 4>5>3>2>1. Webbing between toes extensive (Fig. 8D) reaching to distal subarticular tubercle on both sides of toe 4, to base of disc on inside of toe 5 and outside of toes 1–3, and to distal subarticular tubercle on inside of toes 2–3. Inner metatarsal tubercle oval, short (1.1 mm long) but prominent; outer metatarsal tubercle absent.

Dorsum predominately blue with few indistinct small brown blotches just behind eyes. Lateral surfaces of snout densely spotted with blue and brown, brown maculations coalesce to form canthal stripe that extends from eye, across nostril and down to edge of jaw; white patch below eye; upper lip with thin margin lacking maculations giving appearance of an off-white labial stripe. Exposed dorsal surfaces of limbs blue, hidden surfaces of limbs buff with scattered dark-brown or green maculations, dorsal surfaces of digits buff, with scattered dark-brown flecking. Ventral surfaces largely off-white, with scattered regions of brown maculations along edges of lower jaw, extremities of limbs, and posterior edge of thighs.

SVL 27.5; TL 17.6; HW 13.4; HL 10.3; EYE 3.3; TYM 1.3; IN 3.5; EN 2.3; 3FD 1.6; 3FP 1.0; 4TD 1.3; 4TP 1.0.

The paratype (SAMA R72339) is an adult male with the following measurements: SVL 26.1; TL 16.2; HW 9.3; HL 9.9; EYE 4.5; TYM 1.3; IN 3.8; EN 2.0; 3FD 1.2; 3FP 0.8; 4TD 0.9; 4TP 0.8. It is broadly similar in colouration, nuptial pad form, and extent of webbing to holotype, but differs in having a mauve dorsal colouration in preservative (likely a preservation artefact), much more prominent white patch laterally on head extending from below eye, across tympanic membrane to insertion point of forelimb, and exposed dorsal surfaces of limbs largely cream with extensive very fine mauve maculations. The vomeropalatines are more prominent than those of the holotype, each supporting 3–4 sharp teeth medial to the choanae (vs. vomeropalatines small, poorly developed in the holotype).

The following description is based on photographs of the holotype and paratype (Figs 7A, B, 8C–E,). Dorsum green with small number of darker-brown flecks. Lateral surface of snout with brown patch bordered sharply dorsally by canthus rostralis, this brown patch forming thin canthal stripe in holotype but covering most lateral surfaces of snout in paratype. Supratympanic fold light brown. Small white patch on upper lip and below eye present in both specimens but more prominent and extensive in paratype. Lateral surfaces of torso ranging from green, yellowish green to translucent with extensive buff flecks, also overlain with sparse brown flecks in paratype. Exposed surfaces of limbs green, sometimes edged by indistinct brown regions. Hidden surfaces of groin and posterior surface of thighs orange (Fig. 8E). Iris pale grey with extensive darker-brown vermiculation, pupil with very thin orange margin.

We analysed 14 calls from the holotype (n = 4) and paratype (n = 10) at 23.6 and 24.5°C respectively. Calls of both animals were extremely similar and were combined for analysis. The call of L. grinpelasp. nov. is a series of 7–21 (mean = 15.0, SD = 5.03) unmusical tapping or popping notes uttered in quick succession (Fig. 9). Calls are produced at intervals of 4.3–132.0 seconds (mean = 24.1, SD = 39.4). Call length is 0.67–2.56 seconds (mean = 1.62, SD = 0.62), and notes within calls are produced at a rate of 7.8–9.6 notes/s (mean = 8.74, SD = 0.44). Dominant frequency is 2707–3082 Hz (mean = 2910, SD = 131.08). An exemplar call from the holotype has been uploaded to iNaturalist (https://www.inaturalist.org/observations/218063820).

Genetic divergences (p-distances) indicate that L. grinpelasp. nov. is most genetically similar to the clade comprising L. kikorisp. nov. and L. spartacus (p-distances from 0.144–0.161).

The name combines the New Guinea pidgin word for green (grin) with its adjectival ending (-pela).

Litoria grinpelasp. nov. is known from two locations along the southern slopes of Papua New Guinea’s Central Cordillera: the type locality in the upper Strickland River basin in Western Province, and Libano Sok, on the Hegigio River in the Kikori River basin in Southern Highlands Province, 100 km to the east of the type locality (Fig. 5).

Both animals were calling from foliage 3–4 m above the ground in low-elevation hill forest (Fig. 6B) adjacent to swiftly flowing rivers. Four other torrent-breeding pelodryadids were documented at the type locality, one of which (L. longicrus) occurred in microsympatry with the new species, while three others (L. arfakiana, L. spartacus and Nyctimystes pulcher Wandolleck, 1911) were found slightly upstream where a waterfall emerges from the side of a karst hill slope (Fig. 6C). At just 215 m a.s.l. this location appears to be the lowest known elevation for L. arfakiana, L. spartacus and N. pulcher (Menzies 2006; Richards and Oliver 2006). At Libano Sok L. grinpelasp. nov. occurred in sympatry with only one other stream-breeding pelodryadid, L. kikori (described above).

The two Litoria grinpelasp. nov. records span approximately 100 kilometres of extensively forested terrain with relatively low human population density. It also occurs at elevations (<500 m a.s.l.) at which populations of torrent-breeding Litoria in the Australian wet tropics have been able to persist in the face of the frog pathogen B. dendrobatidis. If this pathogen colonises New Guinea, this species may therefore be less vulnerable than most other Melanesian torrent-breeding Litoria, which are restricted to higher and cooler areas. For these reasons we suggest an IUCN status of Least Concern.