Madascincus arenicola, Miralles, Aurélien, Köhler, Jörn, Glaw, Frank & Vences, Miguel, 2011

Miralles, Aurélien, Köhler, Jörn, Glaw, Frank & Vences, Miguel, 2011, A molecular phylogeny of the “ Madascincus polleni species complex ”, with description of a new species of scincid lizard from the coastal dune area of northern Madagascar, Zootaxa 2876, pp. 1-16 : 8-12

Madascincus arenicola sp. nov.

Holotype. ZSM 1565/2008 (field number FGZC 1703), adult male, collected at Baie des Sakalava (ca. 5 km SE Ramena), 12°16'34'' S, 49°23'24'' E, 25 m above sea level, Antsiranana Province, northern Madagascar, collected on 20 February 2008 by S. Megson.

Paratypes (8 specimens). ZSM 1564/2008 ( FGZC 1922), Ampombofofo region (Frontier base camp), 12°05'53'' S, 49°19'49'' E, 28 m a.s.l., collected on 10 June 2006 by S. Megson; ZSM 2076/2007 ( FGZC 1031), UADBA uncatalogued ( FGZC 1029, 1030), Baie des Dunes (E Ramena), 12°14'43'' S, 49°22'53'' E, 14 m a.s.l., collected on 23 February 2007 by P. Bora, H. Enting, F. Glaw, A. Knoll and J. Köhler; ZSM 1566–1569 /2008 ( FGZC 1743, 1744, 1767, 1797), Baie des Sakalava (ca. 5 km SE Ramena), 12°16'34'' S, 49°23'24'' E, 25 m a.s.l., collected from 21 to 23 February 2008 by S. Megson. All localities within Antsiranana Province, northern Madagascar.

Diagnosis. As a member of the Malagasy scincine lineage, Madascincus arenicola differs from the other Malagasy lygosomine genera ( Cryptoblepharus and Trachylepis ) by the presence of entirely scaly movable eyelids (versus fused immovable eyelids forming a spectacle over the eye in Cryptoblepharus ; or movable eyelids with a translucent disk or window in the lower eyelid in Trachylepis ), absence of prefrontal scales (present in both Cryptoblepharus and Trachylepis ), and absence of frontoparietal scales (present in Trachylepis ).

Within the Malagasy Scincinae , Madascincus arenicola is easily distinguishable from all other species by the combination of the following characters: presence of two pairs of pentadactyl legs, light bronze dorsal coloration with two dark well-defined lateral stripes, and absence of postnasals. The new species is assigned to the genus Madascincus based on its molecular phylogenetic relationships.

Within the genus Madascincus , the absence of postnasal scales is exclusively associated to M. arenicola . In addition to this highly discriminant character, M. arenicola is distinguished from all its congeners by the following combination of characters: SVL ranging from 61.5 to 81.7 mm (versus a maximum SVL of 29 mm in M. nanus , 33.5 mm in M. macrolepis , 39 mm in M. minutus , 50 mm in M. ankodabensis , 57 mm in M. melanopleura ); 74–81 rows of paravertebral scales (versus 51–64 in M. melanopleura , 60–68 in M. mouroundavae , and 48–57 in M. nanus ); 75–80 rows of ventral scales (versus 48–54 in M. minutus , 56–63 in M. melanopleura , 59–63 in M. nanus , 60 in M. macrolepis , 61 in M. ankodabensis , 63–67 in M. mouroundavae ; relatively long toes, with 16–19 (most often 17 or 18) subdigital lamellae under the fourth (versus 5–6 in M. macrolepis , 6–9 in M. nanus , 10–11 in M. minutus , 13 in M. ankodabensis , 9–16 in M. melanopleura ); 26 rows of scales around midbody (versus 18 in M. macrolepis , 20 in M. nanus , 20–22 in M. minutus , 22 in M. ankodabensis , 28–32 in M. mouroundavae , 30–32 in specimens of the " stumpffi " phenotype); presence of two well defined two-scales wide dark longitudinal stripes on the flank (versus six dark stripes in M. igneocaudatus , dorsum uniformly dark, without lateral stripes in M. minutus and M. nanus ; pentadactyl forelimbs (versus 4–5 digits in M. nanus and 3–4 in M. sp. "baeus"); and more generally by the very characteristic snout shape and its slender body.

Additionally, M. arenicola is also distinguishable from the other species of the “ polleni ” species complex by its contrasted coloration, characterized by the presence of a pair of two-scale wide dark lateral lines extending from snout to hindlimbs, well defined all along the body (versus lateral lines well defined anteriorly, becoming one – or two parallel – very thin dashed line posteriorly to forelimbs in M. polleni and in the lined morph of M. stumpffi , and lateral lines reduced to very short dark streak extending from the snout to the ear-opening, progressively fading and disappearing on the neck in the uniform morph of M. stumpffi ), and by the characteristic shape of its snout, being relatively long and acute in lateral aspect (shorter snout in M. polleni , and in lateral aspect more rounded both in M. polleni and M. stumpffi ).

Description of the holotype. ZSM 1565/2008 ( Fig. 2 ). Good state of preservation, with exception of a little circular sampling incision on the right flank (± 4 mm of diameter). Adult male, a mature white testis being recognizable inside the abdominal cavity, via the incision). SVL (71.0 mm) 8.2 times head length (8.7 mm), almost as long as tail (69.9 mm, apparently entire and not regenerated). Limbs remarkably short: SVL 9.4–11.2 times front limb length (6.4–7.6 mm) and 4.7–4.8 times hind limb lenght (15.1– 14.9 mm). Snout relatively long and acute on lateral aspect, with a rostral tip bluntly rounded in dorsal aspect. Rostral wider than high / long, contacting first supralabials, nasals, and supranasals. Paired supranasals in median contact, contacting loreals. Frontonasal roughly triangular, wider than long, contacting loreals, first supraciliaries and first suproculars. Prefrontals absent. Frontal approximately as wide as long, wider posteriorly, in contact with frontonasal, supraoculars, parietals and interparietal. Supraoculars four, all of them in contact with frontal; subequal in size, except the posteriormost pair significantly smaller. Frontoparietals absent. Interparietal longer than wide, well separated from supraoculars; parietal eyespot present with parietal eye evident. Parietals contact posterior to interparietal. Absence of enlarged nuchals.

Nasals just slightly larger than nostrils; contacting rostral, first supralabials and supranasals. Postnasals absent, seemingly fused with the first supralabials. Loreal single, about as high as long. Preocular trapezoidal, longer than high, single. Presubocular roughly square, single. Six supraciliaries on the right sight, seven on the left side, in continuous row; first and last pairs significantly larger and longer than the intermediate ones; last pair projecting onto supraocular shelf. Upper palpebrals small except for last which projects dorsomedially. Pretemporals two, both contacted by parietal. Postsuboculars two; upper contacting lower pretemporal; both contacting penultimate supralabial. Lower eyelid moveable, scaly; lower palpebrals small, longer than high, interdigitating with large polygonal scales of central eyelid. Contact between upper palpebrals and supraciliaries seemingly direct but flexible, i.e. palpebral cleft narrow. Primary temporal single. Secondary temporals two; upper long, contacting lower pretemporal anteriorly and overlapping lower secondary temporal ventrally. Two tertiary temporals bordering lower secondary temporal. Supralabials six, with the fourth being the enlarged subocular contacting scales of lower eyelid. Postsupralabial single. External ear opening relatively small, without lobules. Mental wider than long, posterior margin convex. Postmental wider than long, contacting first two pairs of infralabials. Infralabials six. Three pairs of large chin scales, both members of first and second pairs separated by the same single median scale, and members of third pair separated by three scale rows. No scales extending between infralabials and large chin scales; two asymmetrical postgenials posterolaterally in contact with the third pair of chin scales. Gulars similar in size and outline to ventrals. All scales, except head shields and scales on palms, soles, and digits, cycloid, smooth, and imbricate; longitudinal scale rows at mid-body 26; paravertebrals 80, similar in size to adjacent scales; ventrals 79. Inner preanals larger than outer. Both pairs of limbs pentadactyl; fingers and toes very short, clawed; relative length of toes in the following order: I<II=V<III<IV. Subdigital lamellae smooth, single, with 7 under fourth finger (on each side), 17 under right fourth toe, and 18 under left fourth toe.

In preservative, a pair of lateral dark brown stripes (about two scales wide at midbody) separating a bronze dorsal field (about eight scales wide at midbody) from the whitish ventral field (about 14 scales wide at midbody), extending from the loreals, around eye (except the eyelids that are whitish), above ear opening, above forelimb and hindlimbs, then progressively breaking up into a succession of little dots along tail. Dorsal sides of forelimbs, hindlimbs and tail dark chocolate brown. Light bronze dorsal field extending from dorsal side of head and neck to dorsum; laterally lighter on two scale wide along the lateral dark brown stripes. The bronze dorsal field is covered by numerous little dark dots, each one of them in the middle of a dorsal scale, in contact with its posterior edge; resulting in four (anteriorly) to six (posteriorly) thin dash lines, darker and more contrasted in the posterior part of the dorsum, becoming progressively indistinguishable from the dark chocolate-brown background coloration of tail. Immaculate whitish ventral field extending from lower side of head, throat, lower side of limbs and venter, to the ventral side of tail. Palms and soles darker than venter, slightly pigmented. The life coloration of the holotype is unknown. According to the photograph of the paratype specimen ZSM 2075/2007 ( Fig. 4 A, B), the coloration is warmer and brighter than after fixation: the dorsal field tends to be orange; under the black lateral stripes, the lateral side of the ventral field are pale orange colored; and most of the dark parts of the body, especially the dorsal sides of the tail and limbs, as well as the edges of the black lateral stripes, show a subtle purplish tint. A pinkish tint is recognizable on the cream colored throat. The two median rows of dorsal scales are slightly lighter than the adjacent scales. Venter uniformly cream. Eyes totally black.

Variation. The variation among the ZSM type specimens is as follows: number of lamellae under fourth finger: 6–7 (6.36 ± 0.50; 11 sides); number of lamellae under fourth toe: 16–19 (17.54 ± 0.77; 13 sides). Number of ventral scale rows: 75–80 (77.86 ± 1.57; 7); number of paravertebrals scale rows: 74–81 (79.00 ± 2.31; 7); number of longitudinal scale rows at mid-body: 26 (100%, n = 7). Number of supraciliaries (n = 14 sides): six (92.9%), seven (7.1%). Three specimens have a pair of enlarged nuchal scales (42.9%), two specimens have a single nuchal (one on the left side, the other on the right side; 28.6%), two specimens have no nuchal scale (28.6%). All studied specimen have six supralabials on each sides, the fourth being the enlarged subocular (n = 14 sides); all have supranasals in median contact, parietals in median contact, and are devoid of postnasals (n = 7). Head length: 8.7–9.6 mm (9.15 ± 0.29; 7); snout-vent length: 61.5–81.7 mm (72.30 ± 6.05; 7); tail length: 58.0–71.0 mm (65.90 ± 5.23; 7); forelimb length: 5.32–7.59 mm (6.72 ± 0.63; 10 sides); hindlimb length: 14.9–17.8 mm (15.76 ± 0.93; 13 sides). SVL/tail length ratio: 6.81–8.47; SVL/head length ratio: 0.94–1.36; SVL/forelimb length ratio: 8.86–13.28; SVL/ hindlimb length ratio: 3.94–4.92. There is no noteworthy variation of coloration within the material examined.

Etymology. The specific epithet is a composite of the Latin arena (sand) and incola (inhabitant). It refers to the sand-dwelling habits of the species and is used as an invariable noun in apposition.

Natural history. All specimens of the type series were captured with pitfall traps and drift fences over night on sandy soils within disturbed secondary forest or shrub. We were not able to observe active specimens during the day and therefore suspect a mainly fossorial or sub-fossorial habit during daytime, whereas the species must be active on the surface at least at night as demonstrated by the pitfall captures. Captured individuals had an excellent ability to quickly entrench themselves into the sand. Madascincus arenicola occurs in sympatry with other sanddwelling fossorial squamates, namely Paracontias minimus , P. rothschildi , P. f a s i k a and Xenotyphlops grandidieri (see Megson et al. 2009). Furthermore, it occurs together with another species of Madascincus , here called phenotype “ polleni " (corresponding to clade 1, see above).

Distribution. Only known from the Baie des Sakalava and Baie des Dunes in the Forêt d’Orangea area, and north of the Antsiranana bay in the Ampombofofo region, northern Madagascar ( Fig. 6 C).

MadascIncus stumpffI Phenotype “ pollenI ”

Figures

FIGURE 2. Schematic drawings of the holotype of Madascincus arenicola sp. nov. (ZSM 1565 / 2008); (A) dorsal, (B) ventral and (C) lateral view of the right side of the head, (D) detail of right eye. Scale bars = 1 mm.

FIGURE 4. Paratype specimen of Madascincus arenicola sp. nov. (ZSM 2076 / 2007) in life. (A) dorsolateral view, (B) detail of anterior body and head.

FIGURE 6. Distribution maps of the different taxa forming the " Madascincus polleni species complex ". Colored circles represent localities with voucher specimens and DNA sequences included in the present phylogenetic analyses, whereas black dots represent collection vouchers specimens that have been only used for the morphological study (see appendix for the exact localities).