Cyrtodactylus hutchinsoni, Oliver & Karkkainen & Richards, 2021

Oliver, Paul M., Karkkainen, Denise Taimi & Richards, Stephen J., 2021, A new species of Cyrtodactylus (Squamata: Gekkonidae) from the northern versant of New Guinea’s Central Cordillera, Zootaxa 5057 (2), pp. 260-270 : 261-267

Cyrtodactylus hutchinsoni sp. nov.

Hutchinson’s Bent-toed Gecko

Figs. 1 , 2A 3A urn:lsid:zoobank.org:act:472DCD6D-226C-4690-89A2-E0B0A0337901

Holotype. SAMA R70284 (F# SJR12821), adult female with original tail and alcohol-preserved tissue ( ABTC 114857 ). Collected from an unnamed limestone range approximately 13 km south-east of Hotmin Mission , West Sepik (Sandaun) Province, Papua New Guinea (4.6439ºS, 141.6791ºE; 950 m a.s.l.) by S.J. Richards and D. Ama on 8 December 2009.

Diagnosis. Cyrtodactylus hutchinsoni sp. nov. can be distinguished from all other Melanesian and Wallacean Cyrtodactylus by its unique combination of adult size large (SVL up to at least 144.0 mm); body slender; head moderately wide (HW/SVL 0.19); dorsal tubercles flat or at most slightly keeled, rounded, and in approximately 18–20 longitudinal rows at mid-torso; tubercles on ventrolateral folds rounded; tubercles not extending ventrally past ventrolateral folds; tubercles absent on lower jaw and throat; caudal tubercles flat or slightly keeled and at base of tail only; subcaudal scales on original tail not transversely widened; enlarged precloacal and femoral scales forming a continuous series of up to 80 scales that extends to knee; and dorsal colour pattern in life including four pairs of dark-brown dorsal blotches with prominent off-white margins on grey-brown background, and further extensive dark-brown reticulations and small blotchings across head and limbs.

Description of the holotype. Adult female of large size (SVL 144.0 mm, TrK 69.6 mm). Head long (HL/SVL 0.25), moderately wide (HW/SVL 0.19), and clearly distinct from neck. Snout rounded in dorsal and lateral profile. Eye to naris distance greater than orbital diameter (EN/OrB 1.42), loreal region slightly inflated, interorbital region and posterodorsal region of snout concave, canthus rostralis rounded. Eyes large (OrB/HL 0.27), pupil vertical with four lobes on each side, supraciliaries extending from anteroventral to posterodorsal edge of orbit, slightly longer at the anterodorsal margin. Ear opening oval, longitudinally widened, bordered above by dorsal skin fold.

Rostral roughly pentagonal, about two-thirds as high as wide, with medial suture extending vertically approximately two-thirds ventrally from dorsal edge, bordered dorsally by two flattened supranasals and one much narrower internasal. Nares bordered by first supralabial (point contact), rostral, one enlarged supranasal and enlarged postnasals—five on left and three on right. Supralabials, mostly squarish and ranging from slightly higher than wide to slightly wider than high, 14 to rictus and 10 to midpoint of eye on both sides. Head, temporal and nuchal scales small and granular. Nuchal and temporal regions interspersed with numerous rounded or slightly conical tubercles approximately 2–3 times width of surrounding scales. Enlarged infralabials wider than high, 12 on both sides, bordered by several rows of slightly enlarged scales that grade into small granular gular scales, gular tubercles absent. Mental wider than high, broadly triangular, slightly constricted at point of contact with postmentals.

Body moderately gracile and narrower than head; trunk long (Trk/SVL 0.48) with ventrolateral folds. Dorsum with 18–20 middorsal rows (excluding tubercles on ventrolateral folds) of flat or slightly keeled tubercles approximately 3–4 times width of surrounding small granular scales. Tubercles on ventrolateral folds low and slightly conical in dorsal profile, rounded in lateral profile, in series of 35–37. Ventral scales much larger than dorsal scales, increasing in size medially and arranged in approximately 40 rows at midpoint of torso. Precloacal region with patch of enlarged scales beginning approximately five rows from cloaca, continuous with a single row of enlarged femoral scales extending along full length of femur, up to 80 scales across the longest continuous femoral and precloacal series.

Limbs slender, forelimbs (FA/SVL 0.15) shorter and less robust than hindlimbs (HDL/SVL 0.18). Lateral and dorsal surfaces of lower forelimbs, and upper and lower hindlimbs with numerous low, rounded tubercles approximately 2–4 times size of surrounding granular scales. Digits long, well developed, inflected at basal interphalangeal joints; subdigital lamellae smooth, rounded, undivided and expanded proximal to digital inflection (6–12–13–14–10 on left manus; 9–11–14–15–13 on left pes); narrow distal to digital inflection (7–9–10–9–11 on left manus; 8–10– 11–10–11 on left pes); large recurved claws sheathed by one dorsal and one ventral scale.

Tail original, complete, fixed in recurved position ( Fig. 1 ), 169.0 mm long; scales irregular in shape, medial subcaudal scales twice size of dorsal scales; up to eight indistinct rows of slightly keeled or flat and round dorsal tubercles extending to approximately 10 mm posterior of tail base and approximately 2–3 times size of surrounding scales; a single flat, round lateral tubercle present on each side approximately 5 mm posterior of tail base. Two low, rounded, postcloacal tubercles on each side of tail.

Colouration in preservative. Torso dorsally with medium-brown background, overlain by four pairs of irregular dark-brown blotches with light greyish-brown margins, posterior-most pair of blotches much smaller than others ( Fig. 1A ). Nuchal band dark brown, roughly triangular, extending along posterolateral surfaces of head to posterior edge of eye, thinly divided by a discontinuous light grey-brown medial stripe. Pair of distinct light greybrown stripes extend along posterior margin of nuchal band from shoulder to rictus. A further short grey-brown postorbital stripe present at posterodorsal edge of each eye. Crown of head medium brown with four clusters of irregular dark-brown blotches with indistinct grey-brown margins. Snout light to medium brown with indistinct dark-brown blotching. Supralabials and infralabials buff, with medium-brown speckling. Limbs and digits medium brown dorsally with scattered darker-brown flecks; on hindlimbs and all digits these flecks coalesce to form indistinct bands or blotches. Ventral surfaces of head, torso and limbs buff with scattered light- to medium-brown maculations and flecks, most dense on limbs ( Fig. 1B ). Dorsal surface of tail medium brown with large irregularly shaped dark-brown blotches, anterior three blotches clearly margined with light grey, posterior blotches with very indistinct margins. Ventral surface of tail medium buff with scattered darker-brown flecks. Postcloacal tubercles light beige with light-brown flecks.

Colouration in life. The following description is based on photographs of the holotype taken at night. Pattern in life similar to that in preservative, but more strongly contrasting. Dorsal surfaces of head, neck, trunk and tail greyish brown, lateral surfaces of neck, trunk and posterior of tail grey; these dorsal and lateral base colours are strongly contrasting against darker-brown dorsal and lateral blotches, flecks and mottling ( Fig. 2A ). Dorsal blotches and nuchal band all have distinct off-white margins and are further mottled with varying tones of brown, including indistinct dark-brown reticulations. Labial scales, postorbital stripes and ventral margins of nuchal band off-white with minimal brown patterning. Dorsal surfaces of limbs grey with distinct to indistinct dark-grey bands or blotches with extensive dark-brown mottling, margins of bands and blotches off-white and indistinct, further dark-brown flecking on limbs. Dorsal surface of tail grey with five large irregular dark-brown blotches or bands with distinct off-white margins followed by two indistinct dark-brown regions without pale margins. Ventral surfaces dark buff with extensive flecking and maculations in varying tones of brown. Ventral surface of tail dark brown with minimal darker flecking, buff anteriorly. Postcloacal tubercles light beige with brown flecks. Iris silvery-grey with extensive chestnut reticulations. Tongue pink.

Summary measurements of holotype (mm). SVL 144.0, TL 169.0, OT 169.0, TrK 69.6, HW 27.2, HH 17.1, HL 36.1, EN 13.6, IN 5.0, OrB 9.6, EAR 1.8, FA 21.7, HDL 26.3. Meristics: SUPR 14L/14R to rictus (10L/10R to midpoint of eyes), INFR 12L/12R, DTR 18–20, VENT 40, Toe I LAM (manus) 6 expanded, 7 narrow, Toe 1 LAM (pes) 9 expanded, 8 narrow, Toe IV LAM (manus) 14 expanded, 9 narrow, Toe IV LAM (pes) 15 expanded, 10 narrow, PCTUB 2L/2R.

Comparisons. Grismer et al. (2021a) provide definitions and summaries of species groups within Cyrtodactylus and we use these groups in the comparisons below. Cyrtodactylus hutchinsoni sp. nov. can be distinguished from members of the C. arcanus group ( C. arcanus Oliver, Richards & Sistrom and C. manos Oliver, Karkkainen, Rösler & Richards ), C. capreoloides group ( C. boreoclivus Oliver, Krey, Mumpuni & Richards , C. capreloides Rösler, Richards & Günther , C. medioclivus Oliver, Richards & Sistrom , C. minor Oliver & Richards and C. tanim Nielsen & Oliver ) and C. sermowaiensis group ( C. atremus Kraus & Weijola , C. crustulus Oliver, Hartman, Turner, Wilde, Austin & Richards and C. sermowaiensis De Rooij ) by a combination of large size (SVL> 120 mm versus maximum SVL <120 mm) and dorsal pattern consisting of four pairs of large and irregular dark-brown dorsal blotches (versus five or more numerous and narrower brown blotches or series of bands, often with extensive brown vermiculations or reticulations).

Cyrtodactylus hutchinsoni sp. nov. differs from members of the C. lousiadensis group ( C. epiroticus, Kraus , C. klugei Kraus , C. lousiadensis De Vis , C. murua Kraus & Allison , C. robustus Kraus , C. salomonesis Rösler, Richards & Günther , and C. tripartitus Kraus ) in lacking transversely widened subcaudal scales (versus present), in having a lower number of dorsal tubercle rows (18–20 versus 20–35), and (with the exception of C. murua ) in having a dorsal pattern in life of paired dark-brown blotches on a greyish-brown background (versus alternating and unbroken dark-brown and light-brown transverse bands).

Cyrtodactylus hutchinsoni sp. nov. differs from the larger-bodied taxa in the C. novaeguineae group ( C. equestris Oliver, Richards, Mumpuni & Rösler , C. irianjayaensis Rösler , C. novaeguineae Schlegel , C. rex Oliver, Richards, Mumpuni & Rösler and C. zugi Oliver, Tjaturadi, Mumpuni, Krey & Richards ) in lacking enlarged tubercles ventral to the ventrolateral folds or on the throat (versus present). Cyrtodactylus hutchinsoni sp. nov. differs from the two smaller species in the C. novaeguineae group ( C. aaroni Gu ̈nther & Rösler and C. mimikanus Boulenger ) in its combination of larger body size (up to at least SVL 144 mm versus maximum SVL of 86.5 mm for C. aaroni and 103 mm for C. mimikanus ), in lacking transversely widened subcaudal scales (versus present), and in having a dorsal pattern of a small number of dark-brown irregularly shaped pairs of blotches (versus 7–11 relatively straight and largely unbroken brown bands bordered posteriorly by narrow to wide whitish margins).

Cyrtodactylus hutchinsoni sp. nov. is genetically and morphologically part of the C. loriae group. Within this group, populations currently referred to as C. loriae represent a paraphyletic species complex of at least four probable species distributed across eastern New Guinea ( Tallowin et al. 2018; Grismer et al. 2021a). In this context, the most critical comparison of the new species is with whichever of these taxa is most likely to be true C. loriae , which was originally described from specimens collected in Moroka district inland from Port Moresby. The following comparisons with C. loriae therefore focus on the type material (n=2), and on two genotyped specimens collected near the type locality (Fane area, Central Province) that are morphologically similar to the types ( Fig. 2B ). Cyrtodactylus hutchinsoni sp. nov. can be differentiated from these specimens by its larger size (up to at least SVL 144 mm versus maximum SVL of 123 mm), by having a grey-brown (in life) or medium-brown (in preservative) dorsal ground colour (versus yellowish-brown in both life and preservative), by having dark-brown dorsal blotches with strongly contrasting off-white margins (versus very indistinct light-brown blotches without contrasting margins but with the blotches containing two pairs of small dark-brown spots—one anteriorly, one posteriorly—except for the nuchal band, which only has the posterior pair of spots), dorsal surface of head with further dark-brown blotches that strongly contrast against the grey-brown base colour in life (versus no distinct pattern, and overall light yellowish-brown in life), and venter dark buff in life with scattered darker-brown flecks and maculations (versus yellowbrown and unpatterned). From the geographically most proximate known populations of the C. loriae complex from localities in Chimbu Province, including the vicinities of Karimui, Doido, Noru and Yuro Villages (Appendix 1), C. hutchinsoni sp. nov. can be distinguished by its larger size (up to at least SVL 144 mm versus SVL to 128 mm; n = 21) and dark-buff venter in life with dark-brown flecks and maculations (versus buff and unpatterned).

Cyrtodactylus hutchinsoni sp. nov. is geographically and genetically most proximate to C. serratus and shares large size with that species. However, it has ventrolateral and caudal tubercles of different shape (low and at most slightly keeled in dorsal profile versus raised and dentate), 18–20 tubercle rows across the dorsum (versus approximately 10–15 rows), and more densely arranged ventrolateral tubercles in the region just superior to the ventrolateral folds (on adults typically more than two rows in the region 5 mm dorsal to the ventrolateral fold versus typically, at most, only one row within the region 5 mm dorsal to the ventrolateral fold), dorsal and lateral tubercle rows on original tails at base only (versus enlarged tubercles extending along the tail in prominent regular whorls) ( Fig. 3A–B ), and in having light greyish-brown base colouration on the dorsal and lateral surfaces in life (versus usually khaki or darker-brown) ( Figs. 2C–D ).

Genetic differentiation. Based on analyses of mitochondrial ND2 data published elsewhere ( Tallowin et al. 2018), C. hutchinsoni sp. nov. (therein listed as Cyrtodactylus cf. serratus ) is most closely related to C. serratus (mean p-distances 0.121 –0.129) and is more divergent from C. loriae from near the type locality (p-distance 0.160). Other candidate species identified in the C. loriae group identified by Tallowin et al. (2018) have similar or higher levels of genetic divergence (p-distances 0.127 –0.213).

Etymology. Named in honour of Mark Hutchinson, recently retired Curator of Herpetology at the South Australian Museum; first, in recognition of his broad contributions to herpetology spanning ecology, osteology, paleontology, systematics and conservation; and second, and more specifically, acknowledging his support and supervision of both PMO and SJR over the last two decades.

Distribution and Habitat. Cyrtodactylus hutchinsoni sp. nov. is known from one location on the northern slopes of Papua New Guinea’s Central Cordillera ( Fig. 4 ), where it was collected from primary upper-hill forest on limestone substrate at an altitude of 950 m a.s.l. ( Fig. 5 ). Given the large extent of apparently suitable habitat in the region, this species probably has a broad distribution along the northern slopes of the Central Cordillera in northwestern Papua New Guinea and adjacent north-eastern Papua Province of Indonesian New Guinea. The holotype is gravid with two well-developed eggs. It was collected from amongst the branches of a large tree that had been felled to make a small clearing for a temporary field camp. This indicates that it is arboreal, like other members of the C. loriae group.

Cyrtodactylus sermowaiensis was collected in sympatry with the new species, but was most commonly observed in lower strata of the forest, on shrubs and close to the ground. Cyrtodactylus rex has also been collected from elevations up to at least 425 m a.s.l. in nearby forests ( Oliver et al. 2016).

Suggested IUCN conservation status. Although this species is only known from the holotype, it comes from an area that is sparsely settled and in which large areas of primary forest remain. The type locality is located on a system of karst ranges that are unsuitable for agriculture and difficult to access. On this basis, we suggest the species be listed as Least Concern.

Figures

FIGURE 1. Holotype of Cyrtodactylus hutchinsoni sp. nov. (SAMA R70284) in preservative: (A) dorsal and (B) ventral view of specimen. Photograph courtesy of Peter Waddington, Queensland Museum.

FIGURE 2. (A) Adult female holotype Cyrtodactylus hutchinsoni sp. nov. (SAMA R70284) from West Sepik (Sandaun) Province, Papua New Guinea. (B) Adult male Cyrtodactylus loriae (BPBM 18649) from Fane, Central Province, Papua New Guinea. (C) Cyrtodactylus serratus (F# SJR14628) from Tabubil, Western Province, Papua New Guinea. (D) Cyrtodactylus serratus (F# SJR12040) from Gugusu Camp in the foothills of the Muller Range in Western Province. Photos A, C–D Stephen J. Richards, B—Fred Kraus.

FIGURE 3. Details of subcaudal scalation on (A) Cyrtodactylus hutchinsoni sp. nov. (SAMA R70284) and (B) Cyrtodactylus serratus (SAMA R66155), showing prominent serrate tubercles extending along the tail on the latter species.

FIGURE 4. Map of New Guinea and surrounding islands with localities for taxa in the Cyrtodactylus loriae Group. Broad overall extent of the Cyrtodactylus loriae complex in eastern New Guinea is highlighted in light blue, with areas over 2000 m a.s.l.—where this complex is unlikely to occur—further marked in purple.

FIGURE 5. Habitat of Cyrtodactylus hutchinsoni sp. nov. in primary upper hill forest on limestone substrate, at an altitude of 950 m a.s.l. in West Sepik (Sandaun) Province, Papua New Guinea: (A) general structure of forest canopy and nearby ranges; (B) forest interior at the type locality. Photographs by Stephen Richards.