Gehyra louisiadensis, Kraus, 2024

Kraus, Fred, 2024, New species of Gehyra (Squamata: Gekkonidae) from Papua New Guinea, Zootaxa 5512 (2), pp. 240-271 : 262-267

Gehyra louisiadensis sp. nov.

urn:lsid:zoobank.org:act:8311665D-1E96-4EB8-9133-91D37A8E6B8B

Figs. 3E , 4D , 10

Gehyra oceanica Kraus & Shea 2005: 471 .

Gehyra oceanica Goldberg, Bursey & Kraus 2010: 139 [part].

Holotype.— BPBM 19763 (field tag FK 9893 ), mature male, F. Kraus, collected at Araeda, Sudest Island , 11.4362° S, 153.4301° E, 1–20 m a.s.l., Milne Bay Province, Papua New Guinea, 28 April 2004.

Paratypes (n=14).— Papua New Guinea: Milne Bay Province: Sudest Island : same data as holotype ( BPBM 19762 ) , same data as holotype except collected 11 April 2004 ( BPBM 19759 ) , ridge N of Camp 1, 11.48° S, 153.41° E, 120–130 m a.s.l., 26 April 2004 ( BPBM 19760–61 ) ; Rossel Island: Damunu , 11.365° S, 154.001° E, 0–40 m a.s.l., 1 May 2004 ( BPBM 19764–67 ) , Cheme , 11.3231° S, 154.2428° E, 5 m a.s.l. 5 May 2004 ( BPBM 19768 ) ; Misima Island: Liak , 10.6608° S, 152.6854° E, 0–20 m a.s.l., 11–15 January 2003 ( BPBM 17218 , 17220–22 ) , Bwaga Bwaga Ridge , 10.674° S, 152.683° E, 440–480 m a.s.l., 12 January 2003 ( BPBM 17219 ) .

Diagnosis.—A medium-sized ( SVL of adult males 68.0–83.0 mm, of adult females 53.0–77.0 mm) species of Gehyra having entirely undivided subterminal lamellae on all toes; 11–15 T 4 lamellae; 10–15 T 1 lamellae; moderate amount of webbing between all toes ( T 3– T 4webL/ T 4L = 0.17–0.31, T 4– T 5webL/ T 4L = 0.08–0.19); long snout (SN/HL = 0.46–0.51, EN/HL = 0.37–0.42); narrow head ( HW /HL = 0.73–0.86); 38–56 enlarged precloacal/femoral scales; 28–55 precloacal/femoral pores in a continuous chevron; a medial row of enlarged subcaudal scales with some smaller scales interspersed; tail depressed, flattened, lacking lateral serrations; skin folds absent on trunk and forearms; popliteal skin fold absent (n = 13) or small (n = 2); elongate postmentals; 1–6 scales in posterior contact with postmentals; three postnasals; all postsupranasal scales small, with none>50% size of supranasal; dorsal color pattern of large, dark-brown, anastomozing maculations on a medium-brown or yellow-brown ground color.

Comparisons with other species.—Among Melanesian Gehyra , G. louisiadensis is easily distinguished from G. baliola , G. barea , G. insulensis , G. interstitialis , G. lampei , G. leopoldi , and G. papuana by having undivided (vs. divided) subapical lamellae under the toes. Gehyra louisiadensis differs from G. cf. dubia in having extensive webbing between the digits (vs. absent or only basal in G. cf. dubia ); from G. chrysopeleia , G. georgpotthasti , G. marginata , G. membranacruralis , and G. rohan by its much smaller size (up to 83 mm SVL in G. louisiadensis vs.> 100 mm in those other species), lack of popliteal and antecubital skin folds (vs. prominent skin folds in those other species), and fewer T 4 lamellae (11–15 vs. 16–27 in those other species); and from G. serraticauda in its smaller size (up to 83 mm SVL vs. 90 mm SVL in G. serraticauda ), absence of lateral serrations on the tail (vs. present in G. serraticauda ), and dorsum boldly maculated with dark brown (vs. dorsum gray with or without red markings in G. serraticauda ).

Gehyra louisiadensis is most similar to G. oceanica and G. maculicincta . It differs from G. oceanica in its generally smaller size (up to 83 mm SVL vs. up to 102 mm in G. oceanica ), fewer T 4 lamellae (11–15, mean 13.8 vs. 13–19, mean 15.7 in 157 Polynesian G. oceanica , 15–20, mean 17.7 in 80 Micronesian G. oceanica ); medial row of enlarged subcaudal scales (vs. subcaudals small and subequal in G. oceanica ); and color pattern of large dark-brown maculations on a lighter-brown ground (vs. dorsum uniform gray, brown, or with small scattered spots but not boldly maculated in G. oceanica ). These meristic differences are most clear in a bivariate plot of numbers of precloacal/femoral pores vs. numbers of T 4 lamellae ( Fig. 8 ).

Gehyra louisiadensis differs from G. maculicincta in its larger size (up to 83 mm SVL vs. up to 69.5 mm in G. maculicincta ), greater number of T4 lamellae (11–15, mean 13.8 vs. 11–13, mean 12.4 in G. maculicincta ), greater number of T1 lamellae (10–15, mean 11.8 vs. 8–11, mean 9.8 in G. maculicincta ), medial row of enlarged subcaudal scales (vs. subcaudals small and subequal in G. maculicincta ), relatively narrower head (HW/HL = 0.73–0.86, mean 0.80 vs. 0.80–0.94, mean 0.89 in G. maculicincta ), and dorsum with large dark-brown maculations on a medium-brown or yellow-brown ground color (vs. dorsum with alternating bands of bold dark-brown and pale yellow-tan spots in G. maculicincta ).

Description of holotype.—A mature male of medium size (SVL = 72.5 mm) with a right-lateral incision behind the pectoral region; liver removed for molecular studies and most viscera removed for prior parasite studies. Head relatively long (HL/SVL = 0.23) and narrow (HW/HL = 0.83), distinct from neck ( Fig. 10A ). Loreal region slightly inflated; no distinct canthus rostralis. Top of snout concave, area behind nares shallowly concave. Snout tapered and rounded at tip, relatively long (SN/HL = 0.48), almost twice eye diameter (SN/EY = 1.9). Eye of modest size (EY/HL = 0.26, EY/EN = 0.65); pupil vertical, constricted into four lobes; anterior supraciliaries slightly larger than adjacent granules and posterior supraciliaries, remainder subequal to adjacent granules. Ear opening of moderate size (Ear/HL = 0.095), squarish; distance between ear and eye one-third again as large as eye diameter (EE/EY = 1.3). Rostral approximately half again as wide (3.0 mm) as high (1.9 mm), highest medial to supranasals, lower medially, with medial suture on dorsal quarter; length 1.0 mm. Single large internasal separates supranasals, with smaller internasal between this and rostral. Rostral in contact with first supralabials, two supranasals, and two internasals (narrow contact only with larger, posterior internasal). External nares circular; each bordered by rostral, single supranasal, first supralabial, and three postnasals. Each supranasal bordered posteriorly by three (R) or four (L) small postsupranasals, all <<50% size of supranasal. Mental triangular, 2.8 mm wide, rear margin slightly scalloped. Mental bordered posteriorly by two elongate postmentals that are longer than mental ( Fig. 10B ), these each bordered posteriorly by two round scales slightly larger than chin granules. Two shorter subinfralabials lie sequentially lateral to each postmental, decreasing in size posteriorly. First infralabial bordered below by postmental and first subinfralabial, second by both subinfralabials and a smaller round scale, and third by four small scales; subinfralabials behind this increasingly smaller, becoming granular posteriorly. Supralabials to mid-orbital position nine on each side; four tiny supralabials posterior to this; angle of jaw bordered with granular scales. Infralabials ten on each side.

Body of fairly robust habitus (TrL/SVL = 0.43), slightly depressed. Dorsal scales on head, body, limbs, throat, and tail small juxtaposed granules; tubercles absent. Ventral scales larger, flat, smooth, subimbricate, larger midventrally, gradually decreasing in size laterally to become granular. Skin folds absent on body and limbs.

Enlarged precloacal/femoral scales in series of 26 scales on right side (absent from left), containing 24 pores extending in a curve from center of precloacal region to center of thigh ( Fig. 10D ), pores larger medially, smaller laterally; thigh scales anterior to this row flat, subimbricate, larger than those immediately posterior to row; enlarged scales anterior to pore-bearing series extending laterally along most of length of pore series but decreasing in size near lateral end of pore series. Enlarged, imbricate scales form a pubic patch between precloacal series and vent, smaller anteriorly, larger posterior to that, then decreasing slightly in size posteriorly to vent; 12–13 scales in a row between apex of enlarged precloacal series and vent. Scales under arms flat, small, subimbricate; those under hindlimbs larger, flat, imbricate; scales on palms and soles granular to subimbricate.

Fore- and hindlimbs well-developed (FA/SVL = 0.11, CS/SVL = 0.13). Digits well-developed, with broad pads on toes (T4W/T4L = 0.46), all but first fingers with well-developed recurved claws; clawed terminal phalanges on all digits except T1 laterally compressed, free above, arising from toe pad, inset from its margin, extending slightly beyond it; claw on T1 small, terminal, extending slightly beyond toe-pad margin. Subdigital lamellae narrow and smooth, all undivided, most forming a shallowly curved chevron medially ( Fig. 10C ); lamellae extend for two-thirds length of each toe (T4lamellaeL/T4L = 0.65). Lamellae of manus 12-13-14-13-13 on right, 12-13-14-14-13 on left; of pes 13-14-14-15-15 on right, 13-13-15-15-15 on left. Relative lengths of digits on manus and pes I <II <III <V <IV. Webbing present between all digits, reduced on hands, most extensive between T3 and T4 (T3T4webL/T4L = 0.22, T4T5webL/T4L = 0.19).

Tail relatively long (TL/SVL = 0.68), wide (TW/SVL = 0.11) and flattened, no lateral serrations; approximately 4–6 mm of tip missing. Tail constricted slightly just behind cloacal sacs, denoting fracture plane, but scale size and arrangement and coloration continuous on either side of this constriction, suggesting tail is original. Dorsally, tail with granules anteriorly, becoming slightly larger and subimbricate posteriorly; under tail with midventral row of enlarged hexagonal scales and smaller scales laterally ( Fig. 3E ); lateral scales decreasing in size laterally and posteriorly. Cloacal sacs swollen, with single oblong external orifice situated near each lateral margin of vent; four slightly enlarged, blunt postcloacal spurs on each side of tailbase; midventral scales of sac flat, subimbricate, larger posteriorly, slightly larger than those ventrolaterally.

Color in preservative: Dorsal ground color on body, head, limbs, and tail medium brown, with small, slightly darker-brown scattered flecks. Supralabials medium brown; infralabials pale whitish yellow with brown punctations. Ventral surfaces pale whitish yellow heavily punctated with brown, less densely mid-ventrally. Lamellae below expanded portions of digits brown. Iris pale gold around margins, brown around pupil, with brown veins.

Measurements (in mm).—SVL = 72.5, TrL = 31.2, FA = 8.3, CS = 9.2, HL = 16.8, HW = 13.9, HH = 7.3, Ear = 1.6, EE = 5.4, EY = 4.3, SN = 8.1, EN = 6.6, IN = 3.0, T4L = 6.3, T4W = 2.9, T4lamellaeL = 4.1, T3T4webL = 1.4, T4T5webL = 1.2.

Variation.—Males are larger than females (SVL of adult males 68.0–83.0 mm, of adult females 53.0–77.0 mm). As for Gehyra maculicincta , G. louisiadensis develops a number of wide but thin subcaudals in regenerated tails (e.g., BPBM 17222, 19760); one specimen (BPBM 19766) has a mix of thin, widened subcaudals with smaller interspersed scales. Nonetheless, there is still a medial row of enlarged subcaudals in original tails ( Fig. 3E ), with the subcaudals not being as wide or thin as is seen in regenerated tails, nor being small and subequal, as seen in G. maculicincta or G. oceanica . Even by the friable tail standards seen within Gehyra , G. louisiadensis has a remarkable number of missing or damaged tails: nine of 15 specimens lack tails (with the break in each being at the post-cloacal cleavage plane), and two others have clearly regenerated portions of their tails, leaving only four that retain original tails.

Variation in numbers of precloacal/femoral pores in males is striking, varying from 28–55 in series that are complete; two incomplete series (left side damaged or missing in each) include 24 and 36 pores. Precloacal/femoral pores lie within scales that decrease gradually in size laterally and are not greatly different from scale rows anterior to that, so it is impossible to arrive at a reliable count of scales in the pore-bearing series in females or in males having fewer pores. Other mensural and meristic differences between the sexes seem minor ( Table 4 ).

In preservative, many specimens are a uniform brown, but BPBM 19761 also has patches of gray mottling, BPBM 19762 has many tiny brown flecks, BPBM 17222 and BPBM 19759 have dark dorsal markings that are faded anteriorly, and BPBM 17219, 19760, and 19764–65 have a mixture of some pale spots and dark-brown markings, especially anteriorly. Venters vary in degree of brown punctation, with BPBM 19760 and 19764 having extensive punctation and appearing brown to the naked eye, whereas BPBM 17220 and 17222 have very little, appearing white to the naked eye. Irises of all paratypes appear brown, with many showing little of the underlying gold background, though a few do; none has the distinct separation of the gold and brown into separate fields as seen in the holotype.

Color in life.—Field notes for BPBM 17218 recorded the animal as light ashy gray with a pale lemon-yellow venter and tan iris. Color pattern of BPBM 17219, as determined from photographs, comprised a network of dark-brown maculations on a medium-brown ground color, with paler, off-white markings behind the eye and a tan iris. BPBM 19764 was similar though with the dark-brown markings more arrayed in bands across the dorsum and with the markings on the head and neck comprising pale-brown spots and the dark-brown markings arrayed as lines anterior and posterior to the eye ( Fig. 4D ).

Etymology.—The species is named in recognition of its restriction to the Louisiade Archipelago of Papua New Guinea.

Range.—Known from Misima, Sudest, and Rossel Islands, the three main islands of the Louisiade Archipelago ( Fig. 5 ); it is likely to range across the islands of the Calvado Chain, which all lie within the fringing reef that surrounds Sudest and this island chain. It is currently known to occur from sea level to 480 m a.s.l.

Ecology.—All but two animals came from the environs of villages. Habitat in these instances was either gardens or disturbed secondary forest. One animal from Misima and another from Sudest came from inland primary rainforest, the former at 440–480 m a.s.l., the second from 120–130 m a.s.l. Both sites had complete canopy cover with emergents to 25+ m, and both sites were along small streams.

Remarks.—Like many Gehyra species, G. louisiadensis is prone to significant regional intergumentary loss and tail autotomy when captured. As a result, none of the available specimens is perfect for designation as a holotype. The specimen chosen has the virtue of having an original tail (though the tip is missing), thereby showing the size of the original subcaudals, and it has available tissues and little skin damage. It has the disadvantage of having precloacal/femoral pores only on the right leg, with a total on that side of only 24 pores. If the left side were symmetrical in pore distribution, the total number would have been approximately 47–48 pores. All of the paratypes with complete series of precloacal/femoral pores lack original tails, have more skin damage, or are missing their viscera. All other specimens with original tails are either female, also have a damaged precloacal/femoral pore series, or have long, but possibly regenerated, tails. I view determination and illustration of the expanded subcaudals of greater diagnostic importance than the number of precloacal/femoral pores, thereby explaining choice of BPBM 19763 for holotype.

Differences between Gehyra louisiadensis and G. maculicincta in toe lamellae were given above as averages and ranges for T4 lamellae and T1 lamellae because these are standard and quick counts to make. However, the true magnitude of the lamellar differences between these species is more striking when total numbers of lamellae on all digits are contrasted. I did not make these counts for all specimens, but I did so for their respective holotypes. The holotype of G. maculicincta has a total of 210 lamellae under its digits whereas G. louisiadensis has 273, emphasizing the large difference between these two specimens, which averages to approximately a 3-lamellar difference for each toe (273—210 lamellae/20 toes = 3.15 lamellae/toe).

Figures

FIGURE 3. Ventral views of tails of (A) Gehyra chrysopeleia, BPBM 19772, holotype; (B) G.aquilonia, BPBM 34745, holotype; (C) G. maculicincta, BPBM 19771, paratype, showing small, subequal subcaudals of an original tail; (D) G. maculicincta, UMMZ 244055, holotype, showing wide, thin subcaudals of a regenerated tail; (E) G. louisiadensis, BPBM 19763, holotype. Scale bars = 5 mm.

FIGURE 4. Portraits in life of (A) Gehyra chrysopeleia, BPBM 19772, holotype; (B) G. aquilonia, BPBM 34745, holotype; (C) G. maculicincta, UMMZ 244056, paratype; (D) G. louisiadensis, BPBM 19764, paratype; (E) G. oceanica, American Samoa; (F) G. membranacruralis, UMMZ 247752, Varirata National Park, Central Province, PNG. Photo credits: (A) G. Shea, (E) U.S. Geological Survey, (F) V. Weijola, remainder F. Kraus.

FIGURE 5. Map of the Milne Bay region of Papua New Guinea showing collecting localities for species described herein. Solid circle = type locality for both Gehyra chrysopeleia and G. louisiadensis, open circles = additional localities for G. louisiadensis, solid square = type locality for G. maculicincta, open squares = additional localities for G. maculicincta.

FIGURE 8. Bivariate plot of numbers of precloacal/femoral pores vs. numbers of subdigital lamellae on the fourth toe. Lamellae numbers for each specimen are averages of the numbers from each foot. Stars = Gehyra maculicincta, squares = G. louisiadensis, solid circles = Micronesian lineage of G. oceanica, open circles = Pacific lineage of G. oceanica.

FIGURE 10. Details of holotype of Gehyra louisiadensis, BPBM 19763. (A) head, (B) chin, (C) left foot, and (D) precloacal/ femoral pore series. Scale bars = 5 mm.