Hemidactylus beninensis, Bauer, Aaron M., Tchibozo, Sévérin, Pauwels, Olivier S. G. & Lenglet, Georges, 2006

Bauer, Aaron M., Tchibozo, Sévérin, Pauwels, Olivier S. G. & Lenglet, Georges, 2006, A review of the gekkotan lizards of Bénin, with the description of a new species of Hemidactylus (Squamata: Gekkonidae), Zootaxa 1242, pp. 1-20 : 11-16

Hemidactylus beninensis sp. nov.

Figures 4–5

Holotype

Institut Royal des Sciences Naturelles de Belgique ( IRSNB) 2617, adult male; Bénin, Département des Collines, Collines de Dassa­Zoumè, (07°45’N, 02°10’E); collected by Sévérin Tchibozo, 13 June 2005. Paratype. IRSNB 2618, subadult male; same data as holotype.

Diagnosis

A moderate­sized Hemidactylus , snout­vent length at least 68 mm. One pair of greatly enlarged postmentals, in contact behind mental. 14–16 rows of relatively small tubercles. 49 scale rows across venter between lowest rows of tubercles. Six to seven enlarged paired scansors beneath fourth toes of both manus and pes. A single row of 38 precloacal­femoral pores in adult males. Original tail atuberculate, with median subcaudal scales forming broad transverse plates. Dorsal pattern with a series of four complete, dark crossmarkings between nape and sacrum, alternating with incomplete transverse bands extending dorsally form the flanks but failing to meet along the dorsal midline.

Hemidactylus beninensis may be distinguished from all other mainland West African congeners on the basis of (sympatric taxa with differing or non­overlapping character states indicated parenthetically): 14–16 rows of dorsal tubercles (0 rows in H. matschiei , 0–4 rows in H. richardsonii , 8–10 in H. ansorgii , 18–24 rows in H. fasciatus , 18–20 rows in H. n. sp. from Cameroon), precloacal­femoral pores in male in single row of 38 (fewer than 12 in H. echinus , H. muriceus , and H. ansorgii , 14–17 in H. pseudomuriceus , 45 in H. n. sp. from Cameroon), median subcaudal scale row greatly enlarged transversely (not enlarged or hexagonally enlarged in H. echinus , H. kamdemtohami , H. pseudomuriceus , H. muriceus , and H. ansorgii ). Both H. angularis and H. mabouia share overlapping precloacal­femoral pore counts and transversely enlarged subcaudal scales with H. beninensis ; however, both species have conspicuous tubercles on the dorsum of the tail, whereas that in H. beninensis . The new species is most similar in general appearance to a newly described species of Hemidactylus from Cameroon (Bauer et al., in press), with which it shares a mostly smooth dorsal tail surface (atuberculate in H. beninensis , very weakly tuberculate in H. n. sp.), transversely enlarged subcaudal scales, and a similar dorsal color pattern. However, these taxa differ with respect to ( H. beninensis versus H. n. sp.): size (68 versus 100 mm SVL), scansors beneath the fourth toe (6–7 versus 10–11), precloacal­femoral pores (38 versus 45 in the respective holotypes), and rows of dorsal tubercles (14–16 versus 18–20).

Description (based on the holotype, IRSNB 2617)

Adult male, SVL 68.3 mm. Head long (HeadL/SVL ratio 0.29), relatively narrow (HeadW/HeadL ratio 0.67), somewhat depressed (HeadH/HL ratio 0.44), strongly distinct from neck. Lores and interorbital region slightly inflated. Snout moderate (SnEye/HeadL ratio 0.41), less than twice eye diameter (OrbD/SnEye ratio 0.57); scales on snout and forehead small, granular; scales on snout much larger than those on occipital region. Eye relatively large (OrbD/HeadL ratio 0.24); pupil vertical with crenelated margins; supraciliaries short, without spines. Ear opening oval, relatively small (EarL/HeadL ratio 0.06); eye to ear distance greater than diameter of eyes (EyeEar/OrbD ratio 1.22). Rostral approximately 1.5 times wider (3.0 mm) than deep (1.9 mm), incompletely divided dorsally by a deeply­incised rostral groove; two enlarged supranasals separated by a single internasal; rostral in contact with supralabial I, supranasals, and internasal; nostrils oval, each surrounded by supranasal, rostral, first supralabial (narrow contact), and three postnasals, the middle one of which smallest, with very narrow contact with nostril rim; each nostril with a recessed valvular scale at posteromedial border; 3–4 rows of scales separate orbit from supralabials. Mental triangular, minimally deeper (3.2 mm) than wide (2.9 mm) and much deeper than infralabials; one pair of greatly enlarged postmentals meeting at a point behind the mental, each postmental bordered anteriorly by first infralabial, medially by mental, and laterally and posteriorly by a series of four chin shields, the lateralmost much enlarged and also bordering first and second infralabials; remaining three chinshields smaller, approximately four times the size of a granular gular scale. Infralabials bordered by a row of enlarged and axially elongated scales, decreasing in size posteriorly. Enlarged supralabials to midpoint of orbit 8 (left)–9 (right); supralabials to angle of jaws 10 (right)–13 (left); infralabials 10 (left)–9 (right); interorbital scale rows across narrowest point of frontal 14, between supraciliaries 36.

Body moderately slender, trunk relatively long (TrunkL/SVL ratio 0.40), oval in crosssection, with very feebly developed ventrolateral folds without denticulate scales. Dorsal scales heterogeneous, granular; regularly arranged, small (4 times size of granules), weakly conical to slightly keeled, erect to posteriorly­directed tubercles extending from behind occiput to tail base; no tubercles on temporal region; tubercles more or less uniform across dorsum, somewhat more prominent on flanks; tubercles in 14 rows at midbody. Ventral scales larger than dorsal tubercles, subimbricate; somewhat larger on abdomen than on chest, granular and much smaller in gular region; midbody scale rows across belly to lowest row of tubercles 49. Precloacal­femoral pores in a single row of 38, with a single poreless scales in midline separating continuous series of 19 pored scales on each side, extending nearly to knees. Scales on palm and sole smooth, flat, rounded; scales on dorsal aspects of limbs heterogeneous – granular, intermixed with larger domed to conical tubercules, particularly on knees and shanks.

Fore­ and hindlimbs moderately long, stout; forearm and tibia moderately long (ForeaL/SVL ratio 0.15; CrusL/SVL ratio 0.17); digits relatively short, strongly clawed; all digits of manus and pes webbed proximally only; distal portions of digits curved, arising from distal portion of expanded subdigital pad; scansors beneath each toe divided, except for distalmost and a few, basal scansors (usually 0–1); scansors from proximalmost at least twice diameter of palmar scales to distalmost divided scansor: 5­6­7­7­7 (left manus), 5­7­6­7­7 (right manus), 5­7­8­7­6 (left pes), 4­7­7­6­6 (right pes). Relative length of digits of manus: IV ~ III> V> II> I; of pes: IV> III> V> II> I.

Original portion of tail depressed; regenerated portion more slender; length of partly regenerated tail approximately equal to snout­vent length (TailL/SVL ratio 0.97); basal part of original portion of tail covered dorsally with small, posteriorly­pointed, subimbricate to imbricate scales, atuberculate; scales forming regular transverse rows, about 8 such rows per distinct caudal segment (corresponding to underlying muscle segments); ventral scales much larger, smooth, imbricate, with a median row of greatly enlarged subcaudal plates extending nearly across the width of tail. Regenerated portion of tail like original but without segmentation. One small, rounded postcloacal spur on each side of tail base.

Mensural features (holotype / paratype). SVL 68.3/ 54.3 mm, ForeaL 10.5/ 8.3 mm, CrusL 11.5/ 9.9 mm, TailL 66.5 (31.3 regenerated)/51.3 (5.9 regenerated) mm, TailW 7.3/ 5.1 mm, TrunkL 27.2/21.0 mm, HeadL 19.7/ 16.4 mm, HeadW 13.2/ 10.3 mm, HeadH 8.7/ 6.1 mm, OrbD 4.6/ 4.1 mm, EyeEar 5.6/ 4.3 mm, SnEye 8.1/ 6.4 mm, NarEye 5.5/ 4.2 mm, Interorb 2.4/ 1.7 mm, EarL 1.3/ 1.5 mm, Internar 2.1/ 1.5 mm.

Osteology

Parietal bones paired. Stapes imperforate. Phalangeal formulae 2­3­4­5­3 for manus and 2­3­4­5­4 for pes. Presacral vertebrae 26, including 3 anterior cervical (without ribs), 1 lumbar, and 2 sacral vertebrae; 5 pygal and 8.5 post pygal caudal vertebrae to point of regeneration (18.5 in paratype). One pair of slender, crescentic cloacal bones present in both holotype and paratype. Endolymphatic sacs enlarged extracranially, extending to level of 4th–6th vertebrae in both specimens. Radiographs reveal that the holotype is skeletally mature, as is confirmed by its well­developed precloacal­femoral pores, whereas the subadult paratype exhibits incomplete ossification of the carpal and tarsal elements.

Coloration (in preservative)

Body grayish with a series of dark grayish­brown crossbands with darker brown borders; one across nape, one behind axilla, one at mid­trunk, and one in lumbar position. These complete dorsal bands alternating with bands extending dorsally from flanks but not meeting in the dorsal midline, first over scapula. Tips of tubercles whitish, particularly on the flanks. Parietal and temporal regions of head with grayish­brown markings without darker margins. A thick white to cream stripe from lateral surface of rostral and anterior of first supralabial to anterodorsal corner of orbit ­ continuing behind orbit and on to occiput as a series of irregular pale blotches. This stripe bordered above by a grayish­brown stripe extending from nostril to top of orbit and below by a similarly colored triangular marking extending posteriorly from the 2nd to 3rd supralabial scales to ventral half of the anterior margin of the orbit. Limbs mottled with alternating brown and pale gray blotches, particularly distal to the knees and elbows, basal limb segments mostly grayish with faint darker irregular markings. Tail with alternating markings as on dorsum; two complete, dark­bordered brown bands on original portion of post­pygal tail; regenerated portion grayish­brown with darker speckles, without distinct pattern. Venter grayish­cream becoming pale gray subcaudally.

Va r i a t i o n

The subadult paratype differs from the holotype in the following features: postmentals bordered posteriorly by 3 chin shields; supralabials 11, 9 to midpoint of orbit (L), 8(R); infralabials 9 (L&R); dorsal tubercles in 16 rows at midbody; no precloacal or femoral pores; subdigital lamellae: (left manus) 4­6­7­7­7, (right manus) 4­7­7­7­6, (left pes) 4­7­ 7­7­6, (right pes) 4­7­7­7­6. Paratype similar in color to holotype, but more boldly patterned with four complete dark bands on original portion of post­pygal tail.

Distribution and natural history

At present known only from the type locality in the relatively hilly region of the Département des Collines in central Bénin ( Fig. 6 ). The area lies adjacent to the Nigerian border and it is likely that this species occurs in that country as well. A juvenile Hemidactylus angulatus was collected at the same site as the types of H. beninensis . The holotype exhibits damage to the skin of the dorsum of the head ( Fig. 1 ). Such damage is indicative of mechanically weak skin, which is associated with regional integumentary loss, an escape mechanism employed against certain predators by a variety of geckos ( Bauer et al. 1989, 1993).

Figures

FIGURE 1. Map of Bénin showing the localities referred to in the text. Coordinates are degrees north and east. Large font — neighboring countries, small font — départements. Numbered localities: 1 = Chutes de Koudou, Parc National du W du Bénin, 2 = Parc National de la Pendjari, 3 = Koussokoinga (= Koussoukoingou), 4 = Bassila, 5 = Manigri, 6 = Diho (= Idiho), 7 = Agougon (= Agouagon), 8 = Collines de Dassa­Zoumè, 9 = Kétou, 10 = Abomey, 11 = Lokoli, 12 = Niaouli, 13 = Attogon, 14 = Ouidah, 15 = Godomé, 16 = Grand Popo, 17 = Porto Novo.

FIGURE 4. Dorsal view of the holotype of Hemidactylus beninensis sp. nov. (IRSNB 2617). Scale bar = 20 mm.

FIGURE 5. Dorsal view of the paratype of Hemidactylus beninensis sp. nov. (IRSNB 2618). Scale bar = 20 mm.

FIGURE 6. Type locality of Hemidactylus beninensis sp. nov. in the Collines de Dassa­Zoumè Département des Collines, central Bénin.