Geodipsas fatsibe, Mercurio & Andreone, 2005

Mercurio, Vincenzo & Andreone, Franco, 2005, Description of a new Geodipsas snake from northern Madagascar (Squamata: Colubridae), Zootaxa 1093 (1), pp. 61-68 : 62-67

Description of Geodipsas fatsibe n. sp.

( Figs 1–3 )

Holotype — MRSN R1922 , an adult male in good state of preservation, collected on 28 January 1996, western slope of Anjanaharibe­Sud Massif , Valley of Analabe River, 14°46.62’S, 49°26.60’E, 1050 m a.s.l., Befandriana Fivondronana, Mahajanga Faritany (Majunga Province), Madagascar, by F. Andreone, H. Randriamahazo, and J. E. Randrianirina.

Paratypes —MRSN R1921, an adult male in good state of preservation with slightly truncated tail, date of collecting and provenience as for the holotype; MRSN R1920 , an adult male in good state of preservation with partially everted hemipenis, collected on 3 February 2001, eastern slope of Tsaratanana Massif, Antsahamanara, 14°02.55’S, 48°46.79’E, Marovato Fivondronana, Antsiranana Faritany ( Diégo Suarez Province ), by F. Andreone, F. Mattioli, J.E. Randrianirina, and M. Vences .

Diagnosis —The only Geodipsas species with 21 rows of dorsal scales at midbody and a high number of ventrals (195–198).

Description of the holotype —Total length 522 mm; tail 127 mm; 21­21­19 rows of smooth dorsal scales at forebody, midbody and precloacal zone respectively; body rather compressed laterally, more high than wide; 198 ventral scales; 78 divided subcaudals; cloacal plate undivided; 7 supralabials, 3 rd and 4 th in contact with the eye; 9 infralabials, 4 in contact with the anterior genials; anterior genial barely longer than posterior genials; rostral wider than high, visible from above; loreal trapezioidal; one preocular, two postoculars; temporals 1 + 2 + 3 rows; eye vertical diameter 3.2 mm; pupil circular; head distinct from the neck. Measurements and scale characters are summarized in Table 1.

* specimen with truncated tail. Values are therefore not significative for a comparison.

Hemipenial morphology —Fully everted hemipenis single, slightly clavate, noncapitate, and acalyculate. Everted organs little flexed (maybe due to the cut of the major retractor muscle required for the extraction), total length of approximately 14.0 mm. Sulcus spermaticus centrolineal forked distally, represented by a deep furrow bifurcated for about 2.0 mm of its total length of approximately 12.6 mm. Undifferentiated ornamentation with proximal area naked and distal area covered with minute spines tidily arranged around the sulcus forks, lack of irregular surface texture; in sulcal view composed of two large basal hooks on either side of the sulcus spermaticus symmetrically arranged followed by four very strong, elongate and hooked spines in the left and right side; in asulcal view composed by one centred large basal spine followed by three pairs of very large spine, one for each side.

Colouration —In the holotype the scale borders outlined in black, often forming narrow chevrons that draw dark somehow appears as diagonal lines on the flanks or a irregular network. In the posterior part of the body a black vertebral line, from midbody to the tail tip is present. The head shows a typical pattern, on the ground colour a more or less distinct stripe is present between the suture of the parietals on the superior margin of the prefrontals, internasals and rostral and on the one of the posterior supralabials. These stripes are formed through the union of the black margin of the scales of the head. Furthermore, there are many dark flecks that occur to create a spotted pattern. A black band on the neck is also present. In contrast to this dark colouration the supralabials are yellowish to white and separated from each other by a dark line. Lower labials and throat creamy white to yellow. Ventral colour whitish to yellow, more or less pigmented by small brown flecks that posteriorly former a more or less distinct narrow midventral stripe. Subcaudals white, with a dark mid­ventral line. After 4–9 years the analysed specimens maintained the overall natural colour pattern, although they showed a general body shrinkage and slight loss of colour.

Variation — The three specimens are similar in general aspect, and share similarities in size, lepidosis and body proportions ( Table 1). However, they show polychromy in the dorsolateral background colour, with the two individuals from Anjanaharibe­Sud being purple greyish and the one from Tsaratanana light brownish. The paratype MRSN R1921 is a mature male with a dorsolateral purple greyish colour, with an irregular network of dark diagonal stripes (especially on the posterior part of the body), and a black vertebral line. Ventral colour whitish anteriorly immaculate pigmented by small brown flecks that posteriorly form a distinct narrow midventral stripe. The paratype MRSN R1920 , from Tsaratanana, has a light brownish dorsolateral ground colour with a quite regular network of dark diagonal stripes from head to the tail and with a black vertebral line posteriorly. Belly anteriorly yellowish, with small brown flecks that increase in number posteriorly towards the vent; subcaudals whitish with dark brownish midventral line .

Etymology —The specific name “fatsibe” is a Malagasy name, composed by two words: “fatsy”, meaning spine, and the suffix “be”, meaning “big” or “large sized”. The specific epithet (pronounced fow­tsee­bay) makes reference to the large hooked spines at the base of the hemipenis. It is used as a noun in apposition.

Distribution —So far the species is known only from the Anjanaharibe­Sud Massif and the Tsaratanana Massif. We suspect that it might be present in other northern rainforest areas, such as Marojejy, Ambolokopatrika, and Masoala.

Habitats and habits —The three specimens were found at night, while climbing small trees, at about 1.5–2.0 m of elevation from the ground.

Justification— Geodipsas fatsibe can be distinguished from all the species hitherto known, because it is the only of the genus with 21 rows of dorsal scales at midbody and for other diagnostic lepidosis characters ( Table 2). Unfortunately, the small number of available specimens and the presence of only males in the series do not allow an exhaustive comparison with the other Geodipsas species. In terms of pattern of dorsolateral colouration and overall aspect G. fatsibe could be confused with G. laphystia and with G. infralineata . However, G. fatsibe differs from G. infralineata , by having more ventrals (195–198 vs 172–193 in males) and subcaudals (78–82 vs 53–77 in males), smaller body size (620 vs 783 mm maximum known length in males). Geodipsas fatsibe is also distinguished from G. infralineata by having a body laterally more compressed, head more distinct from the neck (1.8 vs 1.3 ratio head width / neck width in specimens of equivalent dimensions), a darker network on the upper side of the head (vs presence only along the interparietal suture), and a comparatively shorter snout (4.7 vs 7.0 mm in specimens of similar size). Remarkable differences lie in the hemipenial ornamentation with the presence on the sulcal side in G. fatsibe of elongate and hooked spines (vs. smaller hooked spines). Geodipsas fatsibe is distinguished from G. laphystia by general lepidosis characters, by having dorsum with a irregular network of dark diagonal stripes (vs. longitudinal fine dark lines), and by characters of hemipenial morphology.

Used abbreviations: SVL: maximum snout vent lenght in mm; TL: maximum tail length in mm; DS: number of dorsal scale rows counted at forebody, midbody and precloacal zone; VS: number of ventral scale; SS number of subcaudal scales. Data are given only for males. Question marks indicate the missing data for a still undescribed species.

Figures

FIGURE 1. Living holotype of Geodipsas fatsibe n. sp., from Analabe Valley, Anjanaharibe­Sud Massif, north­eastern Madagascar (MRSN R1922).

FIGURE 2. Living paratype of Geodipsas fatsibe n. sp., from Antsahamanara, Tsaratanana Massif, northern Madagascar (MRSN R1920).

FIGURE 3. Everted hemipenis of Geodipsas fatsibe n. sp. (from the holotype MRSN R1922). Left sulcal side, right: asulcal side.