Urocotyledon norzilensis, Lobón-Rovira & Rocha & Gower & Perera & Harris, 2022

Lobón-Rovira, Javier, Rocha, Sara, Gower, David J., Perera, Ana & Harris, D. James, 2022, The unexpected gecko: A new cryptic species within Urocotyledon inexpectata (Stejneger, 1893) from the northern granitic Seychelles, Zootaxa 5150 (4), pp. 556-578 : 562-573

Urocotyledon norzilensis sp. nov.

( Figs. 6–7 )

Diplodactylus inexpectatus [part]: Loveridge, 1947: 251

Phyllodactylus inexpectatus [part]: Wermuth, 1965: 137

Urocotyledon inexpectata [part]: Kluge 1983; Gardner, 1985; Bauer et al. 1997; Rösler, 2000: 119; Gerlach & Ineich, 2006; Gerlach, 2008; Rocha et al. 2011; Pawlowski 2022.

Urocotyledon inexpectata: Bourquin & Hitchins 1999 ; Pawlowski & Krämer 2006.

Holotype ( Fig. 6 ). BMNH 1987.1388 , male, collected 100 m above Anse Volbert , Praslin Island, Seychelles by A. S. Gardner on 12 December 1980.

Paratypes. BMNH 1907.10 .15.31 female, collected at Anse Marie-Louise , Praslin Island, Seychelles by J. S. Gardiner without precise collecting data ; BMNH 1987.1391 , male, from Felicité Island , Seychelles, collected by A. S. Gardner on 5 October 1980 ; BMNH 1987.1392 , male, from Coco Island , Seychelles, collected by A. S. Gardner on 6 October 1980 ; BMNH 1987.1389 , male, from Anse Bodamier , Praslin Island, Seychelles, collected by A. S. Gardner on 20 June 1980 .

Additional material. BMNH 1987.1390 , possible juvenile, from Anse Bodamier, Praslin Island, Seychelles, collected by A. S. Gardner on 20 June 1980. This is not included as a paratype because it is not well preserved and is much smaller than the other types ( SVL ~ 16 mm).

Etymology. The name “ norzilensis ” derives from two local words, “ nor ” and “ zil ” which in Seselwa, the official Seychelles creole language, refer to “ north ” and “ islands ”, respectively, and refer to the geographical distribution of this cryptic species. The termination “- ensis ” refers to being from a place or locality.

Diagnosis. A medium sized Urocotyledon with maximum snout-vent length 41.5 mm (mean = 38.9 ± 2.4 mm, n=18), with rounded and moderate snout, 10–12 supralabials and 11–12 infralabials. Dorsal pholidosis with homogeneous small and granular scales; ventral scales smooth and slightly larger. A small, triangular small mental scale, and four to five small postmentals followed by a line of subequally sized post-postmentals. Precloacal and femoral pores absent. Two to four postcloacal spurs. As typical in Urocotyledon , prehensile tail with characteristic lamellae on the underside of the tip of the tail. Subcaudal scales smooth and slightly larger than dorsal scales. One pair of leaf-like terminal scansors separated by a groove on all fingers and toes. Four undivided scansors beneath first digit of both manus and five of pes, 9 or 10 beneath fourth digit of manus, 10 or 13 beneath fourth digit of pes. Dorsum presents pale greyish-pink coloration (in life) with two darker dotted or continuous crossbands from neck to the proximal end of the tail. Lateral band on head from eye to nape.

Comparative diagnosis. Urocotyledon norzilensis sp. nov. is readily distinguished from western African Urocotyledon by the absence of dermal webbing on the posterior face of the hindlimb and absence of enlarged subcaudal scales (present in U. palmata ) plus pale dorsal background coloration and in U. norzilensis sp. nov.; longer snout than U. weileri with more supra- and infralabial scales (11–12 versus 9(10)–9). The new species differs from U. rasmusseni in the absence of denticulate ventrolateral tail margins, more lamellae under the 4 th toe (4 versus 10–13), and absence of rostral cleft. Urocotyledon norzilensis sp. nov. differs from U. wolterstorffi by having more lamellae under the 4 th toe (10–13 versuss 8–9 in U. wolterstorffi ) and smaller and more numerous postmental scales (4–5 small versus two enlarged postmental scales). Urocotyledon norzilensis sp. nov. differs from U. inexpectata , its only Seychelles congener, by having a slightly more extensively ossified skull with a more closed frontoparietal fontanelle and basicranium sutures (versus more paedomorphic form in U. inexpectata ), more maxillary and dentary tooth loci (29–31 and 30 (n=5) in U. norzilensis sp. nov. versus 26–27 and 27 (n=2) in U. inexpectata , respectively; see Table 2 ), shorter hind limb (HLL/SVL <1.37 versus HLL/SVL ≥ 1.4 in U. inexpectata ), relatively larger distance between eyes (SE/SVL>0.63 versus SE/SVL <0.62 in U. inexpectata ) and relatively smaller eye diameter (OD/SVL <0.38 versus OD/SVL> 0.38). They also differ by a genetic differentiation of circa 9% for part of the mitochondrial Cytochrome b gene, and a lack of nuclear haplotype sharing in C-mos, Rag-2 and RELNint61.

Holotype description ( Fig. 6 ). Adult male, SVL 34.3 mm, regenerated tail length 34.3 mm. Body slender, nape indistinct. Head wider in the posterior region, narrowing anteriorly to the snout. Canthus rostralis not prominent, almost absent. Eye diameter 2.4 mm, pupil vertical. One row of small, rounded and slightly prominent supraciliar scales. Ear height 0.8 mm. Ear to eye distance (2.6 mm) slightly larger than eye diameter. Snout dorsally rounded. Frontal and occipital scales small and granular. Rostral wider than deep, in contact with nares, 1 st supralabial, supranasal and three internasal scales. 12 and 10 supralabials on the left and right side, respectively. 12 infralabials on both sides. First supralabial in contact with nostril. Nostril circular and surrounded by rostral, supranasal, two postnasal and first supralabial. Postnasals larger than supranasal. Nostril in direct contact with the rostral and 1 st supralabial. Triangular mental smaller than 1 st infralabials. Five small rounded postmental scales in broad contact with the mental scale, 1 st and 2 nd infralabial. Post-postmental scales similar in size and shape to postmental. Gular scales granular slightly smaller than ventral scales on the belly. A row of enlarged scales is present between the gular scales and infralabials, decreasing in size until the 7 th infralabial where they become the same size as the gular scales.

Body slender ( TRL / SVL = 0.47). Ventral scales larger than dorsal scales, with a group of larger scales immediately anterior to the hindlimbs. The dorsal pholidosis comprises homogenous, small granular scales, with two marked black lines from nape to the regenerated section of the tail. One fourth of the tail is regenerated, with homogeneous granular scales dorsally and more enlarged and flattered scales ventrally. The tip of the tail has 7 irregular setae. Precloacal scales same size as ventral scales. Three well-developed postcloacal spurs on each side.

Fore- and hindlimbs moderately short and stout. Digits relatively long, bearing reduced claws. All digits with granular scales dorsally and distally widened undivided lamellae ventrally. One pair of leaf-like terminal scansors separated by a groove. Terminal scansor of 4 th finger is absent. Number of scansors: 4-6-8-/-5 (right manus) / 5-7- 9-10-9 (right pes) and 4-6-8-8-5 (left manus) /5-7-10-11-9 (left pes). Relative length of digits on manus and pes: I< II < V < III < IV and I< V < II < III < IV, respectively.

Skull with fused (single) nasal bones and fused frontal bones. Parietals divided (paired). Sutures of the braincase visible. Squamosal present. Postorbitofrontal twice the size of the squamosal. Otostapes imperforate. Jugal present, small, almost vestigial. Maxillary with 29 pleurodont isodont tooth loci. Premaxilla with 11 tooth loci. Compound bone of the jaw and surangular distinct, not fused. Dentary with 30 pleurodont isodont tooth loci. Sclerotic ring with 14 segments. See below for a more detailed description of the skull.

Variation. Variation in body measurements of the paratypes of U. norzilensis sp. nov. are reported in Table 1 and 2 . This species presents variation in the number of supralabial and infralabial scales which range from 10–12 and 11–12, respectively. Females tend to be smaller than males ( Fig. 3A ). Nevertheless, all paratypes are in agreement with the holotype in scalation and meristic characters.

Coloration. In life ( Fig. 3A , specimen DB6776): dorsum pale cream with irregular dark brown markings from the posterior of the head to anterior part of the tail; the dorsal region of the nape with a larger aggregation of dark brown marks; dorsal surface of head and tail slightly paler without dark spots. Skin slightly translucent through which darker internal organs can be seen. Lateral dark brown crossband from posterior part of the eye to neck. Supraciliary scales around the eye pale yellowish. Supralabials with same coloration as dorsal region, with interspersed yellowish and brownish specks. Infralabial homogeneously pale. Ventrum orangish from anterior part of the forelimbs until cloaca. Ventral part of head, limb and tail pale cream, with small dark brown speckles. Terminal leaf-toe scansor pure white. In preservative (Holotype, Fig. 5 ): dorsum brownish with two dark dorsolateral bands bordering middorsal pale cream region; head slightly darker than the central section of the dorsum, with two darker bands from eye to nape; uniform cream coloration ventrally with black speckles from rostral scale to tail. Variation: substantial variation in dorsal pattern ( Fig. 3A ); some specimens with two mottled dorsal dark brown crossbands from nape to tail; occasionally, continuing anteriorly as a V-shaped mark from eyes to nape, or posteriorly until the middle part of the tail; finally, in some specimens the lateral dark markings on the head continue anteriorly to the nares. Similar variation is present also in preserved specimens.

Urocotyledon inexpectata and U. norzilensis sp. nov. skull and mandible description ( Figs. 5 & 7 ). The skulls and mandibles of Urocotyledon inexpectata and U. norzilensis sp. nov. are similar, but with differences in the extent of ossification and the number of tooth loci, as noted above. The skull of both species is longer than wide. The figured CT-scanned specimens of U. inexpectata and U. norzilensis sp. nov. (1907.10.15.7 and 1987.1388, respectively) have a maximal length of 7.94 mm and 8.52 mm, and maximal width of 4.59 mm and 5.1 mm, respectively. All the skull bones present a smooth external surface without co-ossification with overlaying skin. In lateral view, both skulls have a moderately depressed frontal region. The roof of the skulls comprises a pair of semi-rounded parietals, an unpaired well-ossified frontal, unpaired (fused) nasal bones and the supraoocipital bone. The parietals have a posterolateral process that reaches the posterior part of the paraoccipital process. A substantial frontoparietal fontanelle is present in U. inexpectata (n=2) but absent in U. norzilensis sp. nov. (n=5). The postorbitofrontal is a moderate-sized bone in the external part of the frontoparietal suture, in broad contact with both frontal and parietal bones, and with a slightly downward curved lateral process. The frontal bone is overlapped anteriorly by the nasal and has a short anterolateral process. The prefrontal, maxilla and nasal bones surround the bony narial aperture, and an elongated septomaxilla occupies the space between the vomer and the nasal, without being in direct contact with either of these bones. The maxilla overlaps the prefrontal bone. The squamosal is reduced in contact with the posterolateral process of the parietal, curving downward posteriorly towards the quadrate bone to almost close the orbito-temporal space. However, the prefrontal, frontal, postorbitofrontal, jugal and maxilla frame a space occupied by the eye (without forming a well-defined bony orbit). This space occupies ~1/3 of the total length of the skull and the sclerotic ring (14 bones) occupies the majority of this space. The dorsal part of the quadrate bone lies ventral to the anterior semicircular canal of the inner ear and immediately anterior to the paraoccipital process, lateral to the fenestra ovalis and otostapes. Otostapes imperforate. The jugal is a small splinter of bone, flattened dorsolaterally, overlying a facet on the maxilla. A large infraorbital fenestra is visible between the palatine and the pterygoid. The pterygoid is forked, the posterior part widely curved and contacting the medial condyle of the quadrate. Vomers paired. The palate has a well-developed incisive fenestra between the premaxillary shelf and the vomer. The basipterygoid processes are elongate. All braincase sutures are visible, the basipterygoid suture being more distinct in U. inexpectata . The qualitative differences reported above for a single specimen of each species are matched (with minor variation) by the additional specimens that were CT scanned from the southern (n=2) and northern (n=5) island specimens ( Table 1 ).

Maxilla with well-developed foramina laterally, and with 25 (n=2) pleurodont tooth loci in U. inexpectata and 29–31 (n=5) in U. norzilensis sp. nov. Premaxilla with 11 (n=7) pleurodont tooth loci in both species ( Table 2 ). The mandible is composed of a dentary, well-developed coronoid, splenial, surangular and compound bone. Dentary with three large mental foramina, and 26–27 (n=2) pleurodont-isodont tooth loci on each side in U. inexpectata and 30 (n=5) pleurodont-isodont tooth loci in U. norzilensis sp. nov. ( Table 2 ). The splenial is a transversely flattened bone, medially overlapping all other mandibular bones. Splenial with two alveolar foramina, as typically occurs in gekkotans ( Daza et al. 2008).

Natural history and habitat ( Figs. 3D ). Primarily a rock-dwelling species observed in crevices of granitic boulders, where it is often found close to mud-nests of solitary wasps, as reported on its sister species U. inexpectata ( Pawlowski 2022) . However, this species is also found occasionally on fallen bark and leaves. Urocotyledon norzilensis sp. nov. has been found in sympatry with other gekkotan species, including Ailuronyx tachyscopaeus Gerlach & Canning , Phelsuma astriata Tornier , P. sundbergi Rendahl , and Gehyra mutilata (Wiegmann) . Also, U. inexpectata have been recorded to be present in costal forest, mountain rainforest and grassy areas, spanning the altitudinal range from 10 m to 300 m a.s.l. on Mahé and Silhouette islands ( Pawlowski 2022). Therefore, due to the allopatric character and similar behaviour and of U. norzilensis sp. nov, we expected this newly described taxon to occupy the same ecological niches in the northern granitic archipelago.

Distribution ( Fig. 3B ). Urocotyledon norzilensis sp. nov. is widely distributed across the northern Seychelles islands, including Praslin, Curieuse, Aride, Grande Soeur, La Digue, Felicite and Coco. Populations of ‘U. inexpectata’ recorded from Cousine ( Bourquin & Hitchins 1999; Gerlach & Ineich 2006; Pawlowski 2021), another island of the northern archipelago, presumably also refer to this species, although this awaits genetic confirmation.

Figures

FIGURE 3. A—Photographs of dorsal views showing morphological variability found in live Urocotyledon inexpectata and U. norzilensis sp. nov.; circles depict records of U. inexpectata from Silhouette (green) and Mahé (orange), while triangles depict records of U. norzilensis sp. nov. from Praslin (pink) and Felicité (blue). B—distributional records of live material used for morphological analyses; C—Photos of habitat in southern islands. D & E—Photos of habitat in northern granitic islands. Photos by Ana Perera.

FIGURE 5. Skull of Urocotyledon inexpectata (BMNH 1907.10.15.7) in A—lateral, B—dorsal, C—ventral, and mandible in D—lateral, dorsal, medial and ventral view (from up to down). Each color represents a different bone present in the head.

FIGURE 6. Holotype of Urocotyledon norzilensis sp. nov. (BMNH 1987.1388) from Praslin Island, Seychelles. A—Detail of head (from left to right) in dorsal, right and left lateral and ventral views. B—Dorsal and ventral view of whole specimen. C—Detail of pelvic region in ventral view. Scale bars in 1mm increments. Photos by Kevin Webb (NHM).

FIGURE 7. Skull of holotype of Urocotyledon norzilensis sp. nov. (BMNH 1987.1388) in A—lateral, B—dorsal, C—ventral, D—medial, E—frontal and F—posterior view. Each color represents a different bone present in the head.