Litoria stellarum Richards, Johnston & Oliver, 2025, sp. nov.
Year: 2025
Type: article
Abstract: Litoria stellarum sp. nov. urn:lsid:zoobank.org:act: 8D147850-24E3-490C-A591-584A855CE0E8 Star Mountains Torrent Treefrog Figs 1–3 Holotype. SAMA R71763 (FN USNM [SJR]209377), adult male, Dokfuma Meadow, Star Mountains, West Sepik Province, Papua New Guinea (5.0220°S, 141.1171°E; 3,200 m a.s.l.) by S.J. Richards and G. Johnston on 17 November 1991. Paratypes. SAMA R71762 (FN USNM [SJR]209375), PNGNM (FN USNM [SJR]209376), both adult males, same collection details as holotype. Diagnosis. Distinguished from all other Litoria by the following unique combination of characters: 1) size medium (SVL of three males 36.1–41.8 mm, female unknown); 2) snout rounded in dorsal profile, acuminate in lateral profile; 3) vomerine teeth present; 4) males with vocal slits; 5) finger webbing basal, thick, fleshy, not extending beyond proximal subarticular tubercle on finger 4; 6) toes no more than 3/4 webbed; 7) heels without prominent dermal spike or lappet; 7) supratympanic skinfold nearly straight; 8) ear less than ½ diameter of eye (EAR/EYE 0.33–0.43); and 9) dorsal colouration brown, sometimes overlain with large pale green lateral and anterior blotches. Description of holotype. An adult male of medium size (SVL = 41.8 mm) with vocal slits and nuptial pads. Morphometric data are summarised in Table 1. Body moderately robust for a Melanesian pelodryadid (Fig. 1A). Limbs short (TL/SVL 0.54). Head moderately broad (HW/SVL 0.32), slightly narrower than long (HL/SVL 0.33, HW/HL 0.97). Snout narrowly rounded in dorsal view (Fig. 2A), protruding distinctly beyond lower jaw and sloping sharply back to tip of lower jaw in lateral view, tip acuminate (Fig. 2B); canthus rostralis well defined, narrowly rounded, slightly curved; loreal region steeply sloping, slightly concave, lips flared; nostrils slightly closer to tip of snout than eyes, oriented laterally; internarial distance much greater than distance from external naris to eye (EN/IN 0.67, IN/SVL 0.11, EN/SVL 0.07); eyes moderately small (EYE/SVL 0.11) but prominent, protruding in dorsal and lateral views; pupil horizontal. Tympanum small (TYM/SVL 0.04), one third diameter of eye (TYM/ EYE = 0.33), annulus poorly defined, dorsal edge obscured by short, nearly straight supratympanic ridge (Fig. 2B). Vomeropalatines forming two narrow elevations between choanae, left elevation more prominently raised than right, each with six distinct teeth; an additional small, isolated vomeropalatine elevation present on each side, located anterolaterally of choanae; tongue large, covering most of mouth floor, broad with barely detectable shallow posterior notch; vocal slits lateral, short, extending approximately 3 mm anteriorly from near angle of jaws. Skin on dorsum and dorsal surfaces of limbs smooth in preservative, with scattered small tubercles in life, skin on chest and throat very finely granular, on belly and ventral surfaces of thighs moderately granular. Heel with low, poorly defined tubercle; series of low, pale tubercles around vent. Limbs without dermal folds. Fingers moderately long with expanded terminal discs (3FD/SVL 0.06, 3FD/3FP 1.64) with distinct marginal grooves. Subarticular tubercles prominent, rounded, except distal-most tubercle on Finger 3 compressed, possibly artifact of preservation (Fig. 2C); inner metacarpal tubercle elongate, outer metacarpal tubercle broad, flat. Nuptial pad large, pale brown, finely granular, extending 3.7 mm along outer edge of Finger 1. Relative lengths of fingers: 3>4>2>1. Fingers nearly free of webbing, web restricted to thick, fleshy fringe at base of fingers 3–4 and along outside of finger 2 (Fig. 2C). Toes moderately long with expanded terminal discs (4TD/SVL 0.05, 4TD/4TP 1.4) with distinct marginal grooves; disc on Toe 4 smaller than disc on Finger 3 (3FD/4TD 1.10). Subarticular tubercles moderately prominent, rounded, except distalmost subarticular tubercle on Toe 4 compressed, possibly as artifact of preservation (Fig. 2D); inner metatarsal tubercle well developed, oval; no outer metatarsal tubercle. Relative lengths of toes 4>5>3>2>1. Toes about ¾ webbed, webbing thick and fleshy, on outside of Toe 1 reaching distal subarticular tubercle, on inside of Toe 5 and outside of Toes 2 and 3 extending to approximately midway between distal subarticular tubercle and base of disc, and on both sides of Toe 4 to slightly beyond distal edge of middle subarticular tubercle (Fig. 2D). Colour in preservative. Dorsum with dark-brown base colouration, bordered on both sides by two large, relatively symmetrical paler brown dorsolateral blotches that extend from forelimbs to groin (Fig. 3); posterior region of head including orbitals dark brown, snout overlain by large clearly margined greyish brown triangular patch. Side of head dark brown with pale brown blotch under eye, lower lateral regions of torso mid brown, overlain with scattered small dark-brown blotches. Exposed surfaces of arms and legs dark brown, dorsal surfaces of digits dark brown, with exception of Fingers 1 and 2 which are light brown. Ventral surfaces buff, heavily overlain with darker brown blotches and punctations, especially on throat, middle regions of torso, and lower forearms. Underside of fingers and toes mid-brown, becoming noticeably lighter towards, and especially on, underside of discs. Colour in life. Base colouration on dorsum, upper torso and exposed surfaces of limbs dark brown with limbs slightly lighter than dorsum; large lateral blotches along sides of body and triangular patch on snout light green with sparse and very scattered light brown vermiculations (snout) or dark punctations (lateral regions of torso). An additional light green patch posterior to eye extends along edge of lower jaw. Iris silver, heavily flecked with brown, giving appearance of overall orange-brown hue. Variation. Morphometric variation among the three types specimens is presented in Table 1. All are adult males with vocal slits and nuptial pads. SVL ranges from 36.1–41.8 mm. SAMA R71762 is very similar to the holotype in both morphology and colour pattern (Table 1; Figs 1, 3) but paratype PNGNM differs from them both in having longer limbs (TL/SVL 0.65 vs. 0.54–0.58; compare Figs 1A–C), a wider head (HW/SVL 0.36 vs. 0.32 for both other types), and a lower EN/IN ratio (0.59 vs. 0.64–0.67). This paratype also has a colour pattern that differs dramatically in life from the other two specimens, comprising a mid-brown dorsum covered with extensive small dark-brown flecks with no trace of any green pigmentation (Fig. 1C). However, extensive variation in colour pattern is common among torrent-breeding pelodryadid frogs (e.g. Tyler 1968; Oliver et al. 2024; and see Fig. 4) and in its overall body form and snout shape the PNGNM paratype closely resembles the other two types. The co-occurrence of these three specimens on a single waterfall at a high-montane stream where no other pelodryadids were observed also suggests that the observed differences reflect variation within a single species. Future collections including genetic material may necessitate a reassessment of this conclusion. Comparisons with other species. High-elevation treefrog communities in New Guinea are dominated by a radiation of torrent-dwelling Litoria that appears to be monophyletic (Oliver et al. 2024). Unfortunately, genetic samples were not taken from the type series of Litoria stellarum sp. nov. so we were unable to generate sequence data to confirm its phylogenetic associations. However, based on its size, acuminate snout shape, reduced webbing on hands, and ecology, we are confident that the new species is part of this radiation of stream-breeding Litoria, and we here focus comparisons against other species in this group. Litoria stellarum sp. nov. is substantially larger (min adult male SVL> 35 mm versus max adult male SVL <30 mm) than L. amnicola Richards, Tjaturadi, Krey & Donnellan, 2021, L. brongersmai (Loveridge, 1945), L. fuscula Oliver & Richards 2007, L. grinpela Richards and Oliver, 2024, L. lakekamu Richards & Bickford, 2023, L. leucova (Tyler, 1968), L. megalops Richards & Iskandar, 2006, L. modica (Tyler, 1968), L. napaea (Tyler, 1968), L. rara Günther & Richards, 2005, L. rivicola Günther & Richards, 2005 and L. scabra Günther & Richards, 2005. Litoria stellarum sp. nov. is substantially smaller than L. angiana (Boulenger, 1915) and L. skeliphros Oliver, McDonald, Dahl, Nagombi & Richards, 2024 (max male SVL <45 mm versus> 50 mm), and further differs in having hands webbed between fingers 3–4 only (versus webbed between all digits). Litoria stellarum sp. nov. can be distinguished from similar-sized (male SVL between 30–45 mm) species of torrent-dwelling Litoria as follows: from L. arfakiana (Peters & Doria, 1878), L. macki Richards, 2001, L. oenicolen Menzies & Zweifel, 1974, L. spinifera (Tyler 1968) and L. wollastoni (Boulenger, 1914) by lacking (versus having) one or more prominent conical tubercles on the heel. It further differs from L. arfakiana, L. macki and L. spinifera by having thick fleshy basal webbing between fingers 3–4 (Fig. 2C; versus at most a trace of thin membranous webbing), and further from L. oenicolen by its basal finger webbing (versus fingers ~1/3 webbed) and from L. wollastoni by its reduced toe webbing (~3/4 webbed versus web between toes extending to discs on outside of Toe 3 and inside of Toe 5 (cf. Fig. 2D)). It differs from L. micromembrana (Tyler 1968) and L. bulmeri (Tyler 1968) in its distinctly different snout shape (acuminate versus rounded in lateral profile) and in having (versus lacking) webbing between Fingers 3–4, and further from L. bulmeri by having brown base colouration and lacking a welldefined black lateral stripe (versus green dorsum and black lateral stripe present). The new species differs from L. dorsivena (Tyler, 1968) and L. hastula Oliver, Iskandar & Richards, 2023 by its rounded snout in dorsal profile (versus moderately to sharply acuminate), webbing on
Authors: Richards, Stephen J., Johnston, Gregory R., Oliver, Paul M.
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W6912220132
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