Xenotyphlops mocquardi Wallach, Mercurio & Andreone, 2007, n. sp.

Xenotyphlops mocquardi n. sp.

(Figs. 1–4)

Holotype. MRSN R3208 (field no. FAZC 13182), an adult female collected by V. Mercurio, on 14 January 2005.

Type locality. Ambodivahibe (approximately 12 km SE Antsiranana), Antsiranana Fivondronana, Antsiranana Faritany, 22°23’25”S, 49°26’20”E, elevation ca. 40 m.

Diagnosis. Xenotyphlops mocquardi can be immediately diagnosed from all other Typhlopidae by its lateral snout profile (with greatly enlarged circular rostral that is nearly vertically oriented) or anal shield (which is single and broad as in many Alethinophidia). Internally it is unique among the Typhlopidae in the absence of a tracheal lung and expanded tracheal membrane, presence of type G tracheal foramina, and a long heartliver gap. From Letheobia (= Rhinotyphlops), which contains its apparently closest relatives, X. mocquardi can be separated by a long tail (3.7% vs. <0.7–2.2% total length with a length/width ratio of 2.7 vs. 0.7–1.7) that does not taper distally, high number of subcaudals (22 vs. 6–17), and short snout­heart interval (26.4% vs. 29.5%–40.7% SVL). Additionally, Xenotyphlops mocquardi can be distinguished from its congener X. grandidieri by midbody scale rows (22 vs. 20), posterior scale row reduction present (vs. absent), third supralabial (larger than fourth vs. fourth larger than third), orientation of anteroventral rostral point (ventrally vs. anteriorly), vestigial left lung (present vs. absent), and anterior liver extension (right lobe vs. left lobe).

Etymology. This species in named in honor of François Mocquard (1834–1917), the herpetologist who described Xenotyphlops grandidieri. During his life Mocquard contributed in a substantial way to the knowledge of Malagasy herpetofauna (Glaw & Vences, 1994), culminating in his grand systematic synopsis (Mocquard, 1909).

Description. An adult female with nearly uniform diameter throughout, snout­vent length 248.5 mm, tail length 9.5 mm, tail/total length 3.7%, midbody diameter 4.1 mm (nuchal diameter 3.5 mm, cloacal diameter 3.6 mm), total length/midbody diameter ratio 62.9, midtail diameter 3.5 mm, tail length/tail width ratio 2.7; scale rows 22­22­20, middorsals 478, subcaudals 22, dorsocaudals 21, anal shield transversely enlarged and single, three scales wide with anterior margin bordered by five scales; tail with uniform diameter throughout, apex rounded, lacking terminal spine; head narrower than neck, snout truncated in dorsal view; rostral narrowly visible in dorsal view due to its angle; rostral very large, and sub­circular, covered with numerous minute, dome­like convexities and with an acute, ventrally directed point projecting from narrow corneal cutting edge; rostral width/head width ratio 0.90; frontal fused with supraoculars to form narrow broad shield bordering caudal edge of rostral and contacting supranasals laterally; discrete parietals and occipitals lacking; lateral profile of snout with plane of rostral nearly vertical, rostral with an acute apex directed ventrally; second largest shield (after rostral) is supranasal, which widens ventrally and contacts supralabials I–III, minute crescent­shaped infranasal separated completely from supranasal by inferior nostril (that contacts rostral) and inferior nasal suture, which contacts supralabial II; preocular absent, presumably fused with supranasal; ocular small, eye invisible, subocular larger than ocular, in contact with supralabial III; 3 postoculars; SIP T­0, supralabial I minute with pointed anterior end, supralabial II twice the size of supralabial I, supralabial III largest, 1.5 times as long as tall, twice the size of supralabial IV and six times as large as supralabial II, supralabial IV taller than broad with a medial indentation (indicative of fusion of two scales); mental shield enlarged and projecting into notch in upper jaw.

Colouration. In life the specimen exhibited a pink colouration, with some translucent parts that made visible the darker internal organs. In general, anyhow, pigmentation is lacking throughout the entire body. After two years of collection the holotype is now whitish.

Viscera. Sternohyoideus muscle posterior tip 8.2%, sternohyoideus­heart gap 0.65; heart 3.0% (MP = 24.8%), elongate with right atrium 0.67 heart length, ventricle 0.53 heart length, and left atrium 0.40 heart length, ventricle length/width 2.0, snout­heart interval 26.4%; heart­liver gap 7.6%, heart­liver interval 45.1%, heart­gall bladder gap 41.6%; liver narrow, straight, and unipartite, each lobe with a single notch (less than width of lobe), colouration light brown with a pattern of black reticulations forming cris­crossing network of roughly parallel lines, right liver lobe 30.2% (MP 53.3%), unsegmented but with notch at 45.5%, left liver lobe 19.5% (MP 43.8%), unsegmented but with notch at 47.3%, total liver 49.7% (MP 51.2%), total liver segments 2, left liver/right liver 0.65, anterior liver extension (0.12 liver length) on right lobe as in Leptotyphlopidae, posterior liver tail (0.43 liver length) also on right lobe; liver tip overlapping gall bladder (liver­gall bladder gap ­ 0.4%), liver­gall bladder interval 31.4%, liver­kidney gap 21.3%, liver­kidney interval 57.5%; gall bladder 1.6 % (MP 68.8%), anterior to and slightly overlapping pancreas (1.4%), spleen not detectable; gall bladder­kidney gap 20.1%, gall bladder­kidney interval 27.8%, gall bladder­gonad gap 10.1%; right ovary 3.6 % (MP 81.5%), left ovary 2.2% (MP 86.4%), total ovary 5.8% (MP 84.0%); right adrenal MP 82.9%, left adrenal MP 87.7%, total adrenal MP 85.3%; gonad­kidney gap 2.2%, kidneys smooth, right kidney 4.4% (MP 92.0%), left kidney 4.4% (MP 93.6%), total kidney 8.8% (MP 92.8%), kidney overlap 0.47 kidney length, kidney­vent gap 4.2%, kidney­vent interval 10.3%; rectal caecum small (1.4%), bulbous and twice the diameter of adjacent intestine, caecum­vent interval 10.9%, caecum/left kidney 0.32.

Respiratory system lacking tracheal lung, expanded tracheal membrane, left orifice and left bronchus but with a small (0.6%) teardrop shaped expansion of vascular tissue on ventrolateral aspect of right lung just posterior to heart apex (MP 27.1%), precisely where a vestigial left lung would be located. This structure has no free edges, being fused with the parenchyma of the right lung, but has a hollow inner air chamber with a connection to the tracheal airway via the small type G foramen between the tracheal tips. It is reminiscent of a blind sac since no bronchus or typical large orifice are present, but since it is vascularized it must be considered a left lung. Trachea (25.6%, MP 13.6%) with pink cartilages and clear interspaces of equal width, lacking free tips, numbering approximately 273 (or 107.7/10% SVL); tracheal membrane thin and avascular, extending along right lateral aspect of trachea, tracheal membrane/tracheal ring ratio at midpoint 0.33; terminal tracheal entry into right lung, anterior tip of parenchyma 24.9%, cardiac lung 1.4%, right lung highly vascular, 23.1 % (MP 37.9%), with two layers of small, thin­walled faveoli along cranial third of organ, a single layer of larger ediculae along caudal 2/3 of lung, lacking avascular portion, tapering to posterior tip at 49.5%; intrapulmonary bronchus short 7.0% with tiny type G foramina between the cartilage tips, posterior tip of bronchus at 33.4%, bronchus/right lung 0.30; trachea­bronchus 32.6% (MP 17.1%); trachea­bronchus/total lung 0.66.

Organ midpoint­organ midpoint segments include heart MP­right lung MP (13.1%), trachea MP­liver MP (27.6%), heart MP­liver MP (28.5%), liver MP­total kidney MP (39.5%), trachea­bronchus MP­gall bladder MP (39.6%), right lung MP­total adrenal MP (47.4%), heart MP­right gonad MP (56.7%), trachea MP­total adrenal MP (59.6%), trachea­bronchus MP­total kidney MP (63.6%), and heart MP­total kidney MP (68.0%).

Reproduction. Right oviduct hypertrophied (2.5 mm wide), enlarged with thickened walls with two elongate bulges posteriorly that retain the shape of what is interpreted as two large eggs (both exactly 5 mm long or 2.0% SVL) that had been laid shortly before capture on January, thus suggesting that oviposition occurs in the summer. The right ovary held 3 vitellogenic ova (1.5 x 0.75 mm [2] and 1.0 x 0.5 mm) and one small follicle; the left ovary had eleven very small follicles.

Habitat. The specimen was found along a nearly dry sun exposed stream surrounded by riverside vegetation with thin sandy soil substratum and some scattered water pools with a deep of about 20–30 cm. Outside the riverbed the area is characterized by a dry bushy savannah. This species appears similar ecologically to the xeric­adapted Leptotyphlopidae (i.e., Leptotyphlops macrorhynchus) and Typhlopidae (i.e., Letheobia episcopa) that occupy moist fringes of sandy arid regions (Schleich et al., 1996; Franzen & Wallach, 2002; Baha el Din, 2006).

Justification for the new species. The two species differ in seven external characters enumerated in Table 1 (see characters denoted by *) and for the numerous differences in size and position of the viscera as shown in Table 2. Neither species can be confused with any other typhlopid based upon the unique lateral head profile and anal shield. We are aware that the sample size is minimal but both specimens of Xenotyphlops (paralectotype of X. grandidieri MNHN 1905.271, and holotype of X. mocquardi, MRSN R3208) for which visceral data are available are females of identical length so the data are comparable and the observed differences cannot be attributed to either ontogeny or sexual dimorphism.

Revised definition of Xenotyphlops. Examination of the freshly preserved Xenotyphlops mocquardi necessitates revision of the generic diagnosis of Xenotyphlops due to one major error in its description. A supposedly unique character of Xenotyphlops was the presence of numerous soft, flexible papillae on the rostral shield, which necessitated hypothesizing a wet microhabitat for the snake (Wallach & Ineich, 1996). It is now obvious that the rostral shields of both X. grandidieri specimens had sloughed off, a not uncommon occurrence in century­old, poorly preserved serpents, and what was taken to be external papillae are actually the soft tissue structures lying beneath the typical granular, dome­like convexities found in xeric­adapted typhlopids and leptotyphlopids. Presumably these structures have a sensory function, as they appear to be extensions of the nervous system.

According to this new definition, the genus Xenotyphlops is distinguishable externally from all members of the Typhlopidae by its greatly enlarged and nearly circular rostral shield that is nearly vertical in lateral aspect (giving it a ‘bulldozer” appearance) and a single enlarged anal shield. Internally Xenotyphlops is unique among typhlopids in lacking a tracheal lung and possessing an unexpanded tracheal membrane, type G tracheal foramina, and a long heart­liver gap. Other characters that are rare within the family include absence of a preocular, presence of a subocular that is larger than the ocular, absence of a visible eye, T­X supralabial imbrication pattern, elongate body of uniform diameter, absence of an apical spine, pigmentless pattern, and unipartite liver.

Little can be said about the affinities of the two species of Xenotyphlops with the other typhlopids of Madagascar, since up to now no detailed phylogenetic analysis has been carried out. In the only phylogenetic analysis to date on the Scolecophidia, which was unfortunately analyzed only to the species group level, Xenotyphlops was found to be the sister group to the Ramphotyphlops angusticeps group of Australia, which itself was sister group to the R. australis and R. bituberculatus groups with the basal R. affinis group being the most primitive (Wallach, 1998b: Fig. 4). This surprising finding suggests a relationship to Australian rather than Malagasy taxa. It is even more remarkable that Xenotyphlops shows some resemblance to the Leptotyphlopidae and we can add one additional character of X. mocquardi in the arrangement of the liver lobes: the right liver lobe lies craniad of the left, a condition unknown among the Typhlopidae where the left liver lobe extends cranially of the right (as also in X. grandidieri). It is possible that our specimen of X. mocquardi is aberrant in possessing a shortened left liver lobe but that can only de determined with the examination of further material. The presence of a vestige of the left lung is also noteworthy and indicates retention of a primitive characteristic that is quite rare among scolecophidians (Wallach, 1993b).