Alsophis Fitzinger, 1843

Hedges, Blair, Couloux, Arnaud & Vidal, Nicolas, 2009, Molecular phylogeny, classification, and biogeography of West Indian racer snakes of the Tribe Alsophiini (Squamata, Dipsadidae, Xenodontinae), Zootaxa 2067, pp. 1-28 : 13

Genus Alsophis Fitzinger, 1843

Type species. Psammophis antillensis Schlegel, 1837:214 .

Diagnosis. Species in this genus have 19–23 midbody scale rows, 184–220 ventrals, 94–138 subcaudals, two apical scale pits, eight upper labials, 10 lower labials, 18–21 maxillary teeth, and 21–26 dentary teeth ( Table 2). Alsophis differs in at least one of these characters from all alsophiine genera except Borikenophis and Hypsirhynchus . Alsophis differs almost completely from Hypsirhynchus in ventrals (184–220 versus 123–189 in Hypsirhynchus ). It differs from most Borikenophis (163–187), except for B. sanctaecrucis (191–198), in having a higher number of ventrals (184–220).

Content. Eight species (nine species + subspecies) are included in the genus ( Table 1).

Distribution. The genus is distributed in the northern Lesser Antilles ( Fig. 2 ).

Remarks. Species of Alsophis are moderate-sized (1080 mm, maximum SVL) racers ( Fig. 3 A). They are all endemic to islands in the northern Lesser Antilles, from Anguilla to Dominica ( Fig. 2 ). These northern islands are sometimes referred to as the “Leeward” islands. Within the genus, two well-supported geographic groups are present ( Figs. 1 and 4 ) for which we propose species groups. The rufiventris Group comprises species from the northernmost Leeward islands of Anguilla to Antigua ( A. antiguae , A. rijgersmaei , A. rufiventris , and A. sajdaki ). Within this group, we lacked A. antiguae which is possibly extinct (Henderson et al. 1996), but it is closest to A. sajdaki , morphologically. The rufiventris Group is also supported by a hemipenial character ( Zaher 1999). The antillensis Group comprises species from Montserrat to Dominica ( A. antillensis , A. manselli , A. sanctonum , and A. sibonius ), the southern Leeward islands. We did not sample A. sanctonum , but it shares a unique hemipenial character with A. sibonius ( Zaher 1999) , and we assume the two species to be closely related. A comprehensive review of the morphology of Lesser Antillean alsophiines is needed.

Figures

FIGURE 2. Map showing the West Indies (including the southern tip of Florida above, Central America to the west, and the northern edge of South America below) and the distributions of the genera of the Tribe Alsophiini, Subfamily Xenodontinae, Family Dipsadidae.

FIGURE 3. Representatives of genera of the snake Tribe Alsophiini (Dipsadidae: Xenonodontinae). Subtribe Alsophiina: Alsophis manselli (Woodlands Spring, Montserrat), Borikenophis portoricensis (1.5 km W. Playa de Tamarindo, Puerto Rico), Cubophis cantherigerus (2.0 km W Viñales, Pinar del Rio, Cuba), Hypsirhynchus ferox (Barahona, Barahona, Dominican Republic), Ialtris dorsalis (3 km N Bois Sec, Grand’Anse, Haiti), and Magliophis stahli (1.9 km NE Vista Alegre, Puerto Rico). Subtribe Arrhytonina: Arrhyton taeniatum (0.2 km WE Windmill Beach, Guantanamo Bay Naval Station, Cuba). Subtribe Uromacerina: Uromacer oxyrhynchus (4.4 km W Canada Honda, La Altagracia, Dominican Republic). Photos by S. B. Hedges.

FIGURE 1. A phylogeny of Alsophiini. Bayesian tree obtained from the combined data set of six genes (RAG 2, 12 S & 16 S rRNA, cytochrome b, ND 2 and ND 4; 3387 sites). Alsophis portoricensis portoricensis and A. p. anegadae have identical sequences at all genes sampled, and therefore the latter taxon is not shown. Values are ML bootstrap values above 70 % followed by Bayesian posterior probabilities above 90 %. The generic taxonomy in this tree reflects usage prior to this study and shows paraphyly and polyphyly of Alsophis (blue), Arrhyton (purple), and Antillophis (orange). See Table 1 and Figure 4 for the new classification proposed here.

FIGURE 4. A timetree of Alsophiini. Divergence times and credibility / confidence intervals are shown in Table 3. Plei = Pleistocene. The generic taxonomy in this tree reflects the new classification proposed here and detailed in Table 1.