Ialtris Cope, 1862

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 : 19

Genus Ialtris Cope, 1862

Type species. Philodryas dorsalis Günther, 1858:126 .

Diagnosis. Species in this genus have 19 midbody scale rows, 132–192 ventrals, 40–115 subcaudals, zero or two apical scale pits, seven upper labials, 8–9 lower labials, 18–19 total maxillary teeth, and 20–24 dentary teeth ( Table 2). Ialtris differs in at least one of these characters from all other alsophiine genera except Hypsirhynchus . In most Ialtris , maxillary teeth are grooved whereas in Hypsirhynchus (as in other alsophiines) they are ungrooved; in I. haetianus they are ungrooved. Also, most Hypsirhynchus have eight upper labials whereas Ialtris has seven upper labials; the small Jamaican Hypsirhynchus ( H. callilaemus , H. funereus , and H. polylepis ) have seven upper labials ( Table 2).

Content. Four species (six species + subspecies) are included in the genus ( Table 1).

Distribution. The genus is distributed on Hispaniola ( Fig. 2 ).

Remarks. Ialtris ( Fig. 3 E) includes the former Genus Darlingtonia with its single species ( A. haetianus ) and three subspecies (the haetianus Group) and the three species in the genus Ialtris (the dorsalis Group) ( Table 1). Besides the strong molecular support for the monophyly of this genus, there is some morphological support as well. All four species of the Genus Ialtris have seven upper labials, a rare number found only in the three species of the callilaemus group ( Jamaica) of the genus Hypsirhynchus , among other members of the Subtribe Alsophiina (which otherwise have eight). Also, two species of the genus Ialtris ( A. agyrtes and A. haetianus ) lack apical scale pits; such pits are present in the genera Alsophis , Borikenophis , and Cubophis , and absent in the Genus Magliophis . Thus, the Genus Ialtris is separable from all other genera of Alsophiina except Hypsirhynchus . Relationships among the genera of the Subtribe Alsophiina are not well-resolved ( Fig. 1 ), and it might be that these two genera ( Ialtris and Hypsirhynchus ) occurring on Hispaniola are closest relatives.

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.