WEST INDIAN XENODONTINE COLUBRID SNAKES: THEIR PROBABLE ORIGIN, PHYLOGENY, AND ZOOGEOGRAPHY VINCENT J. MAGLIO CONTENTS Al)stract 1 Introduction 1 A^e versus Haliitus 9 The Species Assemblages 9 cautJierigerus species assemblage 10 melanotus species assemblage 27 (ludrcae species assemblage 32 fiiiicreus species assemblage 36 A Problematical Cenus (laltiis) 48 Conclusions 48 Acknowledgments 50 Literature Cited 50 Appendix „_ 52 ABSTRACT The relationships between the thirty-three spe-cies of xenodontine snakes in the West Indies are reviewed primarily on the basis ot osteological and hemipenial morphology. Foiu" species assem-blages are recognized, distinguislied by the shape of the frontal and prefrontal bones and b\' the structure of the hemipenis. Within the caniheri-gcnis species assemblage three genera are recog-nized-A/.so/j/u's, HypsirJujnchus, and Uromacer. It is suggested that this group entered the West Indies from South or Central America, deri\ed from a primitive form of Alsophis. The South American species Alsophis chamissonis appears to be a relict of that primitive stock. The mainland genera Philoditjas and Conophis appear to be later specialized descendants from that same early stock. The three Galapagos species formerly referred to the genus Dromicits {hiserialis, dorsalis, and sk'vini), are placed in the genus AlsopJiis and regarded as close to the primitive mainland forms. The relationships of the genus laltris remain uncertain, but descent from West Indian Alsojiliis is reasonable. The mekinotits species assemblage has not progressed into the West Indies beyond the northern Lesser Antilles, and has almost certainly been derived from the mainland Leimadophis-Liophis-Lygophis complex. The generic name Dioniiciis is applied to these West Indian forms with the name Lcimadopliis as a junior synonym. Two species, andreae and parvifrons from Cuba and Hispaniola, respectively, share a number of osteological characters with Alsophis, but are like Dromicus externally. The hemipenis is of the Alsophis type and unlike that of Dromicus. Be-cause of their peculiar combination of characters these two species cannot readily be accommodated in any existing genus. The name AntiUopliis nov. gen. is proposed for them. It is suggested that they may be closely related to the mainland form Lijgophis hoursieri while the type species of that genus, L. lincatiis, appears to be closer to Dromi-cus. Eight species formerly placed in the genera Arrhytoii, Dromicus, and Darlingtonia, are con-sidered to form the funcrcus species assemblage. Except for the retention of Darlingtonia for hactiana, the species of this group are referred to the genus Arrhyton. A close relationsliip to the mainland genus Rhadinaca is postulated, and it is suggested that the two genera may have been derived from a connnon ancestor. The osteological similarities between these two groups are dis-cussed in terms of general seniiburrowing adapta-tions and are compared with other semi])urr()wiiig to burrowing New World colubrid snakes. It is concluded that these similarities represent a plnlo-genetic relationship rather than morpliological convergence. Four oversea colonizations from the mainland and numerous inter-island dispersals are recjuired to explain the recent West Indian fauna and its present distribution. INTRODUCTION Th(' \Vest Indies today contain an en-demic snake fauna of modest size. In the absence of an adequate fossil record, any Bull. Mus. Comp. Zool., 141(1): 1-54, December, 1970 1
BioStor
