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

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Hypsirhynchus Günther, 1858


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. 2View FIGURE 2).

Remarks. Species of Hypsirhynchus  ( Fig. 3View FIGURE 3 D) are small and moderate-sized (850 mm, maximum SVL) racers. Members of the Genus Hypsirhynchus  included in our analysis ( Figs. 1View FIGURE 1. A and 4View FIGURE 4. A) 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. 1View FIGURE 1. A and 4View FIGURE 4. A). 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  .