Ancylodactylus chyuluensis, Malonza & Bauer, 2022

Malonza, Patrick K. & Bauer, Aaron M., 2022, Resurrection of the African gecko genus Ancylodactylus Müller, 1907 (Squamata: Gekkonidae) and description of six new species from Kenya, Zootaxa 5141 (2), pp. 101-139 : 129-131

Ancylodactylus chyuluensis sp. nov.

Chyulu Hills Pygmy Forest Gecko

( Figure 13 )

Holotype. NMK-L3869, adult male, Chyulu Hills National Park , Makueni County, Kenya (02.56017° S, 37.88877° E; 1200 m), collected September 21 2016 by Patrick K. Malonza, Felista K. Kilunda & Justus Ochong.

Diagnosis. An extremely small-sized Ancylodactylus with a SVL of 28 mm in the unique type. Dorsal scalation mostly homogeneous with a single pair of rows of very small tubercles along the flanks; other scales minute and granular. Limbs and digits long, with enlarged basal lamellae under and proximal to penultimate interphalangeal joint (3 under digit IV). Length of intact original tail slightly longer than SVL. Tail dorsum distal to the pygal portion of the tail atuberculate; median subcaudal scales in a single row of large, but not transversely widened scales. Male precloacal pores in a single continuous row of 8. Dorsal pattern of pale fleurs-de-lis and chevrons as well as pale and dark spots on spots on a gray-brown to olive background; tail with pairs of dark brown and ashy chevrons or crossbands. Ventral coloration grayish with darker markings on the edges of scales yielding a mottled pattern; throat and chin mottled with a bluish center.

Comparisons with Congeners. Ancylodactylus chyuluensis sp. nov. may be distinguished from A. spinicollis and A. petrodroma in lacking an enlarged preaxial metatarsal scale and from these two species plus A. alantika in having a series of flattened, rectangular lamellae subtending the second and third phalanges of the pedal digits, rather than single enlarged, rounded scale (plaque of Perret 1986) at the penultimate joint of each digit. It is distinguished from A. uzungwae , A. quattuorseriatus , A. dickersonae (but see Spawls et al. 2018), A. petrodroma , A. occidentalis , A. spinicollis , A. alantika , A. kituiensis sp. nov., and A. spawlsi sp. nov. by lacking tubercles on the post-pygal (autotomic) portion of the tail dorsum. It has only two tubercle rows on the trunk, one on each flank, a feature that differentiates it form all congeners except some A. dickersonae (0–6 rows fide Perret 1986; 0–4 fide Spawls et al. 2018) and A. mathewsensis sp. nov. (0–2 rows), and A. spawlsi sp. nov. (2 rows). It possesses a lower number of precloacal pores (8) than A. africanus (9–12), A. barbouri (14), A. alantika (11), and A. gigas (15–16), but has a greater number than A. mathewsensis sp. nov. (6–7), A. laikipiensis sp. nov. (7), and A. spawlsi sp. nov. (6). It may also be distinguished in having a single median series of enlarged, but not transversely widened subcaudals in contrast to A. spinicollis , A. petrodroma , and A. occidentalis (irregular subcaudals), A. elgonensis , A. barbouri , A. uzungwae , A. kenyaensis sp. nov., and A. kituiensis sp. nov. (alternating single and paired scales), and A. dilepis , A. gigas , A. africanus , A. quattuorseriatus , A. dickersonae , and A. koehleri , (single row of median subcaudals, but transversely widened or not uniform throughout). In lacking any yellow or orange ventral coloration A. chyuluensis sp. nov. may be distinguished from A. africanus , A. elgonensis , A. koehleri , A. dilepis , A. spinicollis , A. petrodroma , A. occidentalis , A. alantika , A. mathewsensis sp. nov., A. laikipiensis sp. nov., and A. spawlsi , sp. nov. This last feature also distinguishes the new species from A. elgonensis ,

With the only known specimen having a SVL of 28 mm, Ancylodactylus chyuluensis sp. nov. is the smallest known Ancylodactylus . Although diminutive (<30 mm SVL) species of South Asian Cnemaspis have been identified ( Rösler 2016; Batuwita et al. 2019; Sayyed et al. 2021), A. spawlsi sp. nov. and A. chyuluensis sp. nov. represent the first such tiny forms for Ancylodactylus . Among Kenyan congeners both of these species are easily separated on size from A. africanus (maximum 54 mm SVL), A. elgonensis (maximum SVL 61 mm), A. dickersonae (maximum SVL 41 mm), A. kenyaensis sp. nov. (maximum SVL 65 mm, kituiensis sp. nov. (maximum SVL 50 mm), and A. mathewsensis sp. nov. (maximum SVL 40 mm).

Description of holotype. Specimen generally in good condition. Body dorsoventrally flattened, tail entire ( Fig 13 ). Measurements: SVL = 27.2; TAL = 27.1; TRL = 12.5; HL = 8.7; HW = 5.7; OD = 1.3; SE = 3.3. Head elongate (HL/SVL = 0.32), moderately wide (HW/HL = 0.65), depressed, and distinct from the neck, loreal region flattened, canthus rostralis slightly pointed. Scales on snout and loreal region domed, larger than scales of interorbital region and crown. Eyes very small (OD/HL = 0.15), ear opening slit-like; two large internasals, 4 infralabials and 5 supralabials. Mental scale subtriangular; 3 postmentals, the outer pair in contact with the first infralabials and mental, central postmental hexagonal and smaller than its neighbors; 5 post-post mentals.

Mental scale pentagonal and divided, 3 postmentals the outer larger and in contact with the infralabials and mental, and 5 post-post mentals.

Dorsal pholidosis mostly homogenous, body covered by minute granular scales ( Fig. 13A, 13D ) 13. Very small (~ twice size of granular scales), somewhat elongate tubercles present in a sparse row from the neck, across the flanks to the tail base ( Fig. 13A ). Ventral scales much larger than dorsals, smooth, imbricate, slightly larger in precloacal and femoral regions than on chest and belly, smallest in gular region; scales on lateral aspect of neck granular. Ventrolateral folds feebly developed. Fore-and hind limbs relatively long, slender, covered by granular to slightly enlarged sub-imbricating scales, the latter chiefly on the preaxial surfaces. All digits moderately long and slender, strongly clawed; penultimate phalanx of all digits curved, arising angularly from distal portion of wider basal toe pad; three wide basal lamellae, the distalmost much larger than the more proximal, and 9 narrower distal lamellae under digit IV of pes ( Fig. 11C ). Enlarged basal lamellae on digits of pes: I:1, II:2, III:4, IV:3, V:1.

Male precloacal pores in a single continuous row of 8 ( Fig. 13E ). Hemipenial bulge pronounced, a single pair of small postcloacal spurs ( Fig. 13A ). Tail slightly depressed in cross section; segmentation not pronounced. Length of tail 99% of SVL. Scales of tail dorsum granular, squarish to rectangular or rounded, larger than trunk granules; lacking tubercles in post-pygal portion of tail ( Figs. 13C, 13F ). Subcaudal scales larger than dorsals; enlarged midventral subcaudal scales in a single row, but not greatly broadened transversely ( Fig. 13B ).

Coloration (in preservative). Dorsum dark grayish-brown with a series of light gray blotches or chevrons along the back, separated from one another by narrow dark transverse bands ( Fig. 13C ). Dark brown spots parallel to chevrons and also forming a lower row along the flanks, though weakly differentiated. Crown of the head dark grayish-brown, mostly uniform except for a light grayish marking on the occiput and scattered darker patches, e.g. on the snout. Labial scales with alternating light and dark markings. Limbs grayish-brown with darker mottling or spotting; dark bands on all digits. Tail dorsum slightly lighter than trunk with thin transverse dark brown bands. Venter whitish with dark stippling.

Coloration (in life). Based on photographs of freshly euthanized holotype (see Figs. 13A, 13B ). During the day the dorsal color is mainly shades of light to dark gray-brown to olive, although like its congeners, body color was changeable based on substrate, environmental conditions and physiological state. Dorsum bearing a series of eight partly overlapping blue-greyish fleurs-de-lis from the nape to the sacrum. An additional smaller peach-colored marking (cream to orangish) present on the occiput. Anterior margins of fleurs-de-lis with dark brown anterior borders, expanding laterally to form pairs of blotches lateral to the anterior apices of the fleurs-de-lis ( Figs. 13A ). Lateral surfaces with a series of approximately 12 small, roundish, blue-grayish spots extending from the neck, across the shoulder and down the flanks to the sacrum; largest spots between the limb insertions. The sparse flank tubercles are bright white and are each enclosed within a pale spot, although not all spots contain tubercles. A parallel series of smaller, less conspicuous pale spots runs between the fleurs-de-lis and larger spots. Much of the flank area not occupied by pale markings supports irregular, almost blackish spots of different sizes. The head grayish with a dark brown line passing from the snout and through the eye and another extending posteroventrally from the corner of the mouth. Broken transverse blackish bands pass over the crown and between the orbits and there are whitish granules speckled over the lower margins of the head. Posterior to the angle of the jaws there is a single pale peach-colored marking ( Fig. 13A ). Limbs predominantly gray with blackish markings forming irregular banding on the limbs. Thighs with whitish banding alternating with gray and black. Alternating bands of blackish, gray, and ashy white on the digits. The small postcloacal spur is bright white. Tail dorsum mostly pale grayish-olive and bearing a series of 12 dark brown chevrons or cross bands from tail base to tail tip. Proximal dark bands are thin and are followed by a more diffuse ashy border. These markings become less regular near the middle of the tail and both the dark (now blackish) and ashy marks become thicker, excluding the grayish-olive base color from the tail tip, which terminates in a dark brown tip. Individual dark brown or ashy scales are scattered on the spaces between the bands and larger spots alternate along the ventrolateral margin of the tail ( Fig. 13A ). Ventral color of trunk dark overall ( Fig. 13B ) with most individual ventral scales including scattered blackish pigment granules. Distal margins of most scales from neck to groin appear almost pale yellowish as do some of the lateralmost of the ventral scales. Undersides of limbs similarly dark, darker beneath thighs where dark pigment is present at the periphery of all scales. Palms and soles gray with scattered darker punctations. Throat and chin dull whitish to bluish (centrally) and heavily marked by purplish spotting anteriorly and complex reticulations posteriorly that are confluent with the dark trunk markings. Subcaudal surface of the tail pale greenish-white with most scales having their distal and lateral margins darkly pigmented. Pigmentation denser towards tail tip, where some scales are almost entirely black.

Etymology. Named for the Chyulu Hills, the type locality where the single known specimen was collected.

Natural History. This specimen was found at approximately 8h00 in a pitfall trap in an X-shaped drift fence array in a dry forest patch growing within volcanic rocks with fallen dry tree branches/logs in the vicinity. We suspect that the species is arboreal but can descend to utilize fallen logs and trunk bases as well as the crevices in volcanic rocks. It is likely to be a diurnal species and we assume it had entered the trap on the morning of capture or during late afternoon of the previous day, as it was found resting during the cold morning. However, we have no evidence to rule out the possibility of it being nocturnal. Two-day searches had been done in the area before the trapping with the only commonly recorded gecko species at the site being Lygodactylus tsavoensis Malonza, Bauer, Granthon, Williams & Wojnowski on trees and fallen logs/branches. The sampling was carried out during the peak of the dry season in September.

Habitat and Distribution. This is a mid- to high altitude montane species. In the Chyulu Hills there is dry forest on volcanic rocks from elevations of around 1200m that gives way to largely open grasslands from about 1400m. The grassland continues up to the hilltops’ maximum elevation of around 2000m with hilltop patches of moist forests surrounded by grasslands from elevations of about 1800m and above. We suspect the species to be present in these forest patches on tree trunk crevices and cracks, like its congeners. The Chyulu Hills are prone to perennial wildfires. The area where the specimen was collected had been burned in previous years and fires occurred during the sampling period. This is a major conservation threat for this species because the dry trees increase the fire intensity, permitting the fires to burn for long periods, even underground within the volcanic rocks.

Figures

FIGURE 11. Ancylodactylus spawlsi sp. nov. A) Dorsal view of holotype, NMK-L3470. Scale bar = 10 mm. B) Precloacal region of holotype showing series of 6 precloacal pores. C) Ventral view of right hind foot of paratype, NMK-L4007/1. D) Dorsum of tail of holotype illustrating rows of tubercles near the posterior margins of each tail segment.

FIGURE 13. Holotype of Ancylodactylus chyuluensis sp. nov., NMK-L3869.A) Dorsal view. B) Ventral view showing the bluish throat and extensive dark pigmentation on most of the ventral scales. C) Dorsal view of preserved specimen. Scale bar = 10 mm. D) Trunk dorsum at midbody showing mostly granular surface. E) Precloacal region showing single row of 8 pores (arrows mark the lateralmost pores). F) Tail dorsum showing atubercular surface. Photos A–B © P.K. Malonza.