Gehyra serraticauda Skipwith & Oliver, 2014, sp. nov.

Gehyra serraticauda sp. nov.

(Figs 1–3)

Holotype. MCZ R7314, adult male, purchased from Antwerp Edgar Pratt and with collection locality recorded as Fakfak, Onin Peninsula (~2°55'"S, 132°18'E), West Papua Province, Indonesia. Date of original collection unknown, but lodged in the MCZ collection in 1909.

Additional material. Uncollected specimen, from near Kamaka (formerly Warika) Village, 45 km SSE of Kaimana, Triton Bay, (03°46’14”S, 134°10’14”E), West Papua Province, Indonesia, 150–160 m a.s.l., collected, photographed and released by Dmitry Telnov, 10 September 2010.

Diagnosis. Gehyra serraticauda is distinguished from other Gehyra species by the following suite of characters: moderately large size (91 mm SVL), prominent popliteal fold on the hindlimbs, high number of digital lamellae (finger IV = 16, toe IV = 17), distal lamellae deeply notched, rostral concave, supranasals small and widely separated by numerous small internasals, preanal pores arranged in a long single continuous chevron (36), and original tail strongly compressed dorsoventrally and adorned with a continuous series of acuminate scales on the lateral edges.

Comparisons. A summary of comparative data for Melanesian Gehyra is given in Table 1. The combination of moderately large body size (> 90 mm) and distinctive acuminate lateral scales on the tail distinguish this species from all other Gehyra.

Gehyra serraticauda sp. nov. specifically differs from Gehyra mutilata, G. papuana and the types of G. lampei and G. interstitialis in having very distinct lateral caudal serrations (versus minute or none), a much larger adult size (> 90 mm versus <70 mm), and a higher number of internasal scales (~10 versus <4). Based on the original description of G. interstitialis (actual types lost), Gehyra serraticauda sp. nov. further differs in having a notched rostral (versus quadrangular) and U-shaped mental (versus triangular). Gehyra leopoldi is a poorly known taxon that may be synonymous with G. mutilata (Bauer & Henle 1994); it is distinguished from G. serraticauda sp. nov.

by its much smaller size (44 mm), lower number of subdigital lamallae (always <9 versus usually>9 (exceptions being finger I and toe I)), and presence of only a single internasal in a dorsal concavity of the rostral.

Gehyra serraticauda sp. nov. is similar in size to G. baliola, G. barea and G. oceanica, but again differs in having well developed tail serrations. It is further differentiated from G. oceanica by having deeply notched lamellae (versus shallowly notched and undivided), the presence of numerous small internasal scales (versus absent), enlarged subcaudals (versus small), and the presence of a prominent popliteal skinfold (versus absent). Gehyra serraticauda sp. nov. can be distinguished from a final large species of Papuan Gehyra, G. membranacrularis by its deeply notched subdigital lamellae (versus shallowly notched and undivided) and smaller and more numerous internasals (~10 versus 1–4).

Gehyra serraticauda sp. nov. differs from Gehyra marginata Boulenger from the Maluku Islands of Indonesia (just west of New Guinea) in its smaller adult size (<130m versus > 130 mm), divided digital lamellae (versus undivided), lower number of lamellae (digit IV manus = 17 versus 20–25, digit IV pes = 17 versus 20–23), by the presence of many small internasals (versus a single large internasal), well developed popliteal skin folds only (versus well developed lateral skin folds on the trunk and both antecubital and popliteal skin folds), and having enlarged polygonal subcaudals (versus small and relatively uniform).

Two other gekkonid genera occuring in the Pacific region may also have flattened tails with lateral serrations. The three species of Perochirus from Micronesia and Vanuatu have dorso-ventrally flattened tails with very distinct lateral spines; but differ from all Gehyra in the presence of a well developed claw and free phalanx on the inner toe (versus vestigal or absent), and further differ from G. serraticauda sp. nov. specifically in lacking popliteal folds and having much more widely spaced lateral spines (one per tail segment) (Zug 2013). Hemidactylus includes a number of species that have tail serrations and expanded digital pads, but can again be readily distinguished by the presence of a distinct claw on all digits (greatly reduced on the inner toe in Gehyra serraticauda sp. nov.), and are also generally somewhat smaller than G.serraticauda sp. nov.

Description of holotype.– Adult male with expressed postcloacal pores and large flap of loosely attached skin on the right side of the head (Figs. 1 a–b): SVL 91.0 mm; TrK 46.3 mm; HW 17.1 mm; HL 21.8 mm; HD 10.8 mm; EN 7.6; IORB 8.6 mm; POM 2.9 mm; FA 12.3 mm; CS 13.3 mm; EYE 5.8 mm; EAR 2.1 mm; TL(total) 83.0; TL(original) 65.0; IN 10; INT 5; SUPR 13; INFR 11; LAMF4 17; LAMT4 17.

Head triangular, longer than wide (HW/HL=0.78) moderately large (HL/SVL = 0.24) and deep (HD/HL = 0.50); anterior left dentary fractured, posterior corner of jaw upturned. Rostrum long and robust (EN/HL = 0.35) with distinct dorsal concavity, transverse fold of skin extends across tip of rostrum. Rostral with deep dorsal notch, in contact with two supranasals and five small internasals along dorsal edge (Fig. 2 c). Supranasals separated by a high number of small internasals (n = 10) and up to five in transverse series. Nares contacting one supralabial, rostral, one large supranasal and one large postnasal; supralabials 11–12; infralabials 12. Mental U-shaped, bordered by oblong post-mentals. Pupil partially dilated, somewhat elliptical with smooth margins and limited crenulations (Fig. 2 d). Body long and robust (TrK /SVL = 0.40), thorax flexed prominently to the left. Skin on dorsum and venter smooth and composed entirely of small, flat, granular scales.

Limbs relatively short and stout. Digits on both the fore and hind limbs with prominent and expanded pads (finger pads 1.1–1.6 times minimum width of finger, toe pads 1.2–1.5 minimum width of toe) (Fig. 2 a–b); penultimate phalanx free and well developed on all digits except finger I and toe I. The scansorial pad of digit I of both manus and pes is narrower relative to length than the other digits. Distal lamallae (excluding penultimate lamallae) deeply notched on fingers and toes, lamellar counts for all digits (total/deeply notched) as follows: fingers I = 11/4, II = 12/5, III = 16/6, IV = 17/7, V = 16/7; toes I = 14/6, II = 16/7, III = 17/8, IV = 17/8, V = 16/7. Basal webbing between digits limited, never reaches first phalangeal joint. Precloacal and femoral pores (n = 36) arranged in a single curved row terminating halfway along the femur (Fig. 2 f). Hemipenal bulge present but not pronounced, single row of three short cloacal spurs angled posteriorly on each bulge.

Tail strongly compressed dorsoventrally, approximately 1.5 times wider than high, 83.0 mm in total length (65.0 mm original, 18.0 mm regenerated). Original portion partially autotomised 24.0 mm from the vent, with a distinct medial groove on the ventral surface, a single row of greatly enlarged pentagonal subcaudals extending its full length, and a continuous lateral fringe of densely packed acuminate scales extending from just posterior to the hindlimbs to the end of the original tail (Fig. 2 e). Scalation on the regenerated section of the tail is substantially smaller and more irregular and heterogeneous than that of the original, although the subcaudals are still relatively enlarged.

In preservative, dorsum beige with irregular dark grey patches on the left shoulder, lateral regions of torso, pelvic area, and distal portion of the tail. Dorsal surface of the hands and feet beige like the dorsum of the body but with a slight reddish tinge, giving an overall darker appearance; lamellae of all digits beige becoming slightly darker distally. Colouration on the regenerated tail light reddish-grey.

Variation. Photographs of the uncollected specimen from near Kamaka Village kindly provided to us by Dmitry Telnov (Fig. 3 a–c), specimen details above) show that it has a deeply divided rostral, prominent popliteal folds and acuminate scales on the lateral edges of the original tail. It is on the basis of these characters and its large size (field measured SVL ~ 120mm) that we assign this individual to the G. serraticauda sp. nov. When originally captured the colouration of this specimen was as follows; dorsum silvery grey with very extensive terracotta mottling and numerous indistinctly edged transverse bands along the dorsum; fore and hindlimbs predominently terracotta with no clear pattern but some silvery flecking; head with similar mottled colouration to the body and distinct silvery loreal and postorbital stripes; regrown tail silvery brown with no clear pattern; supralabials, infralabials and region of venter visible in photographs yellow; iris light olive green and pupil ellipitical with scalloped edges. In photos taken at a later time prior to release the dorsal colouration is greatly faded and mostly silvery grey with a brownish tinge towards the anterior regions and the only clear patterning being a small number of silvery spots and stripes on the head and neck.

Distribution and ecology. Presuming the collection data for the holotype is accurate; this distribution of this species extends from Fakfak on the Onin Peninsula east as far as the Triton Bay region. Collection information for the holotype indicates that it was purchased from local people, and it thus seems likely that it is from a locality that is within walking distance of Fakfak. However, more fieldwork is required to confirm that this species occurs in this area.

The Triton Bay specimen was collected in primary lowland rainforest on limestone in the environs of Kamaka Village. It was found during the day while hiding under bark on a dead standing tree. Like many Gehyra the strong dorsal patterning on this specimen varied over short periods of time (King & Horner 1989). Nothing is known about the collection locality and habitat of the holotype.

Eytmology. The specific epithet is a feminine combination of the Latin adjective ‘serratus’ (notched like a saw) and the noun “cauda” (tail), and refers to the distinctive enlarged lateral scales on the tail of this species.

Remarks. The taxonomic status and distribution of many Papuan Gehyra remains unclear (a situation exacerbated by low samples sizes for non-human commensal species and the loss and destruction of key types). New material and a proper phylogenetic analysis is required before G. serraticauda sp. nov. can be confidently placed in the phylogeny of Gehyra. However, it is superficially most similar to G. baliola and G. b a re a in overall size and proportions, the presence of a high number of scales between the nasals, and deeply notched lamellae. The distribution of this species also sits between the known range of G. baliola (southern New Guinea) and G. barea (probably widespread over islands just to the west of New Guinea), suggesting possible geographic turnover of ecologically similar and related taxa.

Gehyra, for the most part, is a morphologically conserved taxon and the prominent lateral fringe of acuminate scales on the tail of G. serraticauda sp. nov. is quite unique (although Gehyra mutilata does have a similar, but much less prominent fringe). Many other gekkonids have flattened and or ornamented tails; ranging from prominent lappets (e.g., Ptyhcozoon sp.) to spiniform scales (e.g., Kolekanos plumicaudus and Phelsuma serraticauda). These structures may serve an array of functions, but are most frequently and most easily correlated with outline disruption and camouflage (Young et al. 2002; Heinicke et al. 2012).