Hypsirhynchus Günther, 1858

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 : 17-18

Genus Hypsirhynchus Günther, 1858

Type species. Hypsirhynchus ferox Günther 1858:49 .

Diagnosis. Species in this genus have 17–19 midbody scale rows, 123–189 ventrals, 62–151 subcaudals, 1–2 apical scale pits, 7–8 upper labials, 9–10 lower labials, 13–21 total maxillary teeth, and 18–27 dentary teeth ( Table 2). Hypsirhynchus differs in at least one of these characters from Arrhyton , Haitiophis , Magliophis , and Uromacer . Alsophis differs almost completely from Hypsirhynchus in ventrals (184–220 versus 123–189 in Hypsirhynchus ). Cubophis differs from Hypsirhynchus in possessing a unique hemipenial character: enlarged papillate body calyces in the basal region and medial surface of the lobes ( Zaher 1999). Most Hypsirhynchus have 19 midbody scales rows ( H. ater and H. melanichnus have 17 rows) whereas most Borikenophis have 17 rows (those populations from the Virgin Islands usually have 19 rows). Caraiba differs from Hypsirhynchus in having a unique hemipenis ( Zaher et al. 2009). In most Ialtris , maxillary teeth are grooved whereas in Hypsirhynchus (as in other alsophiines) they are ungrooved ( Maglio 1970); 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.

Content. Eight species (18 species + subspecies) are included in the genus ( Table 1).

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

Remarks. Species of Hypsirhynchus ( Fig. 3 D) are small and moderate-sized (850 mm, maximum SVL) racers. Members of the Genus Hypsirhynchus included in our analysis ( Figs. 1 and 4 ) were previously placed in three genera: “ Arrhyton ” ( Jamaica), and “ Antillophis ” and Hypsirhynchus (Hispaniola) . Here, the species formerly placed in those genera are assigned to three species groups in the Genus Hypsirhynchus : the callilaemus Group ( H. callilaemus , H. funereus , and H. polylepis ) occurring in Jamaica, the ferox Group ( H. ferox and H. scalaris ) occurring in Hispaniola, and the parvifrons Group ( H. parvifrons ) also occurring in Hispaniola. Members of the callilaemus Group have seven upper labials and nine lower labials compared with eight and 10–11 (respectively) present in other members of the genus. Members of the group also share two unique hemipenial characters ( Zaher 1999), and their monophyly suggests an island radiation on Jamaica. The ferox Group can be distinguished from the parvifrons Group by its fewer subcaudals (71–93 versus 100–138, respectively). Hemipenial morphology does not suggest a relationship between the callilaemus Group and any other West Indian group. Instead, Zaher (1999) found unique characters uniting Hypsirhynchus ferox , Haitiophis anomalus , and Borikenophis portoricensis , and other characters uniting Hypsirhynchus parvifrons , Ialtris haetianus , and " Arrhyton " exiguum .

Hypsirhynchus ater from Jamaica has not been seen in about 80 years or more ( Henderson 1992; Henderson & Powell 1996). Another related species, H. capistratus , was described from Jamaica at the same time that H. ater was described ( Gosse 1851), but it was synonymized with H. ater by Boulenger (1893). Although we do not recognize H. capistratus here, the original description suggests that H. capistratus could be a valid species; additional study is needed. No tissue samples were available from any of these taxa, but morphological data suggest some tentative assignments to genus. Hypsirhynchus ater (and H. capistratus , if a valid species) lacks a loreal scale, an uncommon character (the absence of the scale) in the Subtribe Alsophiina that occurs in a few species of the genera Hypsirhynchus ( H. callilaemus of Jamaica, and H. ferox and H. scalaris of Hispaniola), Ialtris ( I. haetianus of Hispaniola) and Magliophis ( M. exiguus of the Puerto Rican Bank). Although Zaher (1999) could not associate H. ater with any West Indian xenodontine based on hemipenial morphology, Maglio (1970) noted skull bone similarities with H. ferox .

Cochran (1941) noted that Hypsirhynchus melanichnus differs from species in the eastern Caribbean (genera Alsophis and Borikenophis ) in lacking a furrow on the side of the head at the upper border of the upper labials. In scale counts it differs from the genera Ialtris and Magliophis in having 17 midbody scale rows (not 19 rows), and from the Genus Borikenophis in having 102 subcaudals (not 106–145). Hypsirhynchus melanichnus also has relatively large posterior upper labials compared with Borikenophis portoricensis , and is closer in that sense to the Genus Hypsirhynchus . Considering all of the morphological evidence, and while recognizing it is not strong, we tentatively assign H. melanichnus to the Genus Hypsirhynchus . In terms of biogeography, such an assignment also makes sense because other species of the genus are distributed in Hispaniola.

Recently, Zaher et al. (2009) resurrected Ocyophis Cope for Hypsirhynchus ater (type species) and included Hypsirhynchus melanichnus , Haitiophis anomalus , Cubophis cantherigerus , C. vudii , and Borikenophis portoricensis in the genus. Such a grouping is unsupported in our expanded molecular data set ( Figs. 1 and 4 ). Therefore we place Ocyophis in the synonymy of Hypsirhynchus . Zaher et al. (2009) also named Schwartzophis for the three small Jamaican species of Hypsirhynchus (our callilaemus Group). However, while those three species have long been known to form a group, we consider it unnecessary to recognize every small cluster of species as a separate genus. Also, in this case the decision was premature because the larger Jamaican racer ( Hypsirhynchus ater ) may be part of that radiation (see above) and it carries an older generic name ( Ocyophis ) that would take priority. Therefore, we also place Schwartzophis in the synonymy of Hypsirhynchus .

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.