Litoria sauroni, Richards, Stephen J. & Oliver, Paul M., 2006

Richards, Stephen J. & Oliver, Paul M., 2006, Two new species of large green canopy­dwelling frogs (Anura: Hylidae: Litoria) from Papua New Guinea, Zootaxa 1295, pp. 41-60 : 46-50

Litoria sauroni sp. nov. ( Figs 3 , 4 , 7 –9)

Holotype. SAMA R60727 adult male with nuptial pads and vocal slits, calling when collected, Darai Plateau, Southern Highlands Province, Papua New Guinea, (07°07'771'S, 143°36'806E at 420 m asl) collected by Stephen Richards and Allen Allison on 26th July 2003.

Paratypes. SAMA R57868 adult male with vocal slits 8­Oct 1999, SAMA R61588, 2­ Oct 1999 adult male with vocal slits, calling when collected; UPNG 10015, 9­Oct­1999 adult male with vocal slits, calling when collected, all from Dark End Lumber, Gulf Province (07°08'894S, 144°22'937E), collected by Stephen Richards.

Diagnosis

Litoria sauroni can be distinguished from congeners by the following combination of characters; 1) uniformly green dorsal colouration 2) large adult size (four males with vocal slits 63.7­70.4 mm) 3) prominent white dermal folds on the arms and legs 4) absence of white labial stripe 5) hands extensively webbed 6) iris finely mottled with red and black 7) sclera blue 8) nictitating membrane with dense stippling of pale blue pigment flecks 9) nuptial pad rounded and small (diameter less than one third length of digit I) and 10) head comparatively narrow (HW/SVL = 0.331­0.357).

Description of holotype

Adult male with following measurements (mm) SVL 70.4; EN 6.3; HW 24.2; EYE 7.3; TL 38.6; IN 6.1; HL 23.2; EAR 4.8; 4TD 4.5; 4TP 3.8; 3FD 5.4; 3FP 3.5. Habitus moderately slender; head marginally wider than long (HW/HL 1.045), not wider than body in dorsal view; snout truncate in dorsal and lateral views; labial region sloping and moderately flared; loreal region steeply sloping, marginally concave; canthus rostralis moderately well defined, curved; nares much closer to tip of snout than to eyes, oriented laterally, only marginally visible in both dorsal and anterior views.

Choanae large, roughly circular, separated by a distance approximately three times their width; vomerine teeth very low and triangular, positioned along the posterior ridge of two prominent elevations located medially to choanae. Eyes moderately small but prominent (EYE/SVL 0.104), distinct in both dorsal and lateral views, pupil horizontal; nictitating membrane heavily flecked with pale blue pigment spots. Tympanum moderately large (EAR/SVL 0.068), annulus distinct, dorsal edge obscured by thick, curved supratympanic fold that runs from posterior edge of eye to above axillary junction. In preservative skin on dorsal surfaces of body and limbs smooth; ventral skin smooth on throat, forelimbs and most of hindlimbs, coarsely granular on abdomen and lateral edge of femur.

Arms robust; a prominent white dermal fold extends from disc of finger IV along upper arm to elbow; relative lengths of fingers III>IV>II>I; terminal discs of all fingers significantly wider than penultimate phalanx (3FP/3FD 0.648), with circum­marginal grooves; subarticular tubercles prominent, rounded to conical, two tubercles on digits I and II, three tubercles (distal tubercle distinctly larger) on digits III and IV; supernumerary tubercles present on proximal phalanx of digits II­IV but low and very indistinct; a single large, ovoid inner metatarsal tubercle and small rounded nuptial excresence at base of digit I. All digits webbed, webbing between digits I and II extends to proximal end of penultimate phalanx; between digits II and III webbing extends to disc on II and proximal end of penultimate phalanx on III; between III and IV webbing extends to disc on both digits.

Legs moderately long (TL/SVL 0.548); prominent white dermal fold along tarsus extends from lateral edge of toe V to heel. Relative lengths of toes IV>V>III>II>I; discs expanded, with circum­marginal grooves (4TP/4TD 0.844), subarticular tubercles prominent, rounded or conical, two tubercles on digits I and II, three tubercles on digits III and V, and four tubercles on digit IV; numerous small round supernumerary tubercles on basal phalanges of digits III­V; inner metatarsal tubercle small, oval shaped. All digits with webbing that extends to the base of the disc.

In life uniform yellowish green dorsally, green tending to yellow on lateral surfaces and pure yellow ventrally. Tympanic membrane with distinct, horseshoe­shaped area of translucent skin. Dorsal surfaces of limbs largely green, except for pink unpigmented upper arm. Inner lateral surfaces of upper legs also pink. Outermost digit on hands and feet yellowish green, webbing and all remaining digits yellow. Prominent white dermal ridges on outer edge of legs and arms, upper eyelid also with thin white edge. Iris black with extensive fine red reticulations; sclera blue.

In preservative, dorsal surfaces coarsely mottled with dark and pale slate blue; this pattern extends onto dorsal surfaces of arms, legs, finger IV and toe V; dorsal surface of remaining digits off white, with slightly darker regions on the dorsal surfaces of the disc; all ventral surfaces pale off white. Nuptial excresences very faint brown, Areas of red pigmentation on the iris have faded to silver in alcohol.

Va r i a t i o n

There is little variation in size or ratios among the type series ( Table 1 ). The paratypes differ from the holotype in having a largely uniform (Vs mottled) pale slate blue dorsal colouration in preservative, although SAMA R57868 does have a very small amount of darker blue pigmentation in scattered and random spots across the dorsum and limbs. In life specimens from Dark End Lumber have a purplish­blue ventral colouration that contrasts significantly with yellow ventral colour of the holotype. This purplish blue extends to the dorsal surface of the pads, inner digits and webbing. In all other respects the colouration of the paratypes and the holotype in life is identical, and no difference in ventral colouration is apparent in preservative. The smallest specimen (SAMA R57868) lacks pigmented nuptial pads, but does have vocal slits, suggesting it is mature or very nearly so.

Comparison with other species

Litoria sauroni can be differentiated from all congeners except L. graminea by the characters used in the species complex diagnosis presented above. It differs from L. graminea in its striking and unique iris colouration of fine red and black mottling, in having dense pigment flecking on the nictitating membrane, in its overall more slender build (see Fig. 8 ) and in having a small round (vs elongate) nuptial pad.

Etymology

From the character Sauron, referred to as ‘the eye’ in Tolkien’s “The Lord of the Rings”, in reference to the striking red and black mottled eye of this taxon.

Natural history

This species has been found only in trees in primary rainforest where males call at night from branches high above the ground.

Figures

FIGURE 3. Lateral view of head of holotype of Litoria sauroni (SAMA R 60727), note extensive pigment flecking on nictitating membrane. Scale = 10 mm.

FIGURE 4. Palmar and Plantar views of holotype of Litoria sauroni (SAMA R 60727). Scale = 10 mm.

FIGURE 7. Litoria sauroni (A) and Litoria dux (B) in life. Note differences in colouration at the edge of the upper eyelid, of the sclera and of the iris. Photos: Stephen Richards.

FIGURE 8. Dorsal views of adult males of the three species discussed in this paper. From left to right Litoria graminea, L. sauroni and L. dux. Note the very broad head of L. graminea.