An enigmatic new snake from the Peruvian Andes, with notes on the Xenodontini (Colubridae, Xenodontinae). American Museum novitates ; no. 2853

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New York, N.Y. : American Museum of Natural History
"Liophis problematicus, new species, is based on a specimen from 1520 m elevation on the Amazonian side of the Andes in the Department of Puno, extreme southeastern Peru. It is a very small snake (adult male 275 mm total length), with a bilobed hemipenis having nude apical discs, a condition that defines a probably monophyletic group (tribe Xenodontini) of at least six genera of Neotropical xenodontine colubrids. Beyond this, the relationships of the new species are uncertain, but a pragmatic assignment to Liophis (s.l.) scarcely violates the definition of this highly variable, possibly nonmonophyletic genus. Incidental notes are provided on the hemipenis, coloration, and behavior of Liophis williamsi, a small snake of Venezuelan cloud forest. It is pointed out in discussion that hemipenial variation among the Xenodontini is much greater than has been indicated in the literature, and that the tribe is based essentially on a single character - the paired apical discs, which may have been lost in some populations but which are accepted as a defining synapomorphy pending further study. Defensive neck flattening or hood display is widespread in the Xenodontini, having been recorded for at least five of the six genera currently assigned, and seems to provide a behavioral synapomorphy that corroborates the validity of the group. North American snakes of the genus Heterodon also flatten their necks and have been compared morphologically with some Xenodontini; a relationship between Xenodon and South American Hydrodynastes, another genus of neck spreaders, also has been suggested. Heterodon and Hydrodynastes have relatively primitive hemipenes and cannot be included in the Xenodontini. The hypothesis that one genus or the other is a sister group of the Xenodontini deserves to be tested by morphological criteria - although this seems to be strongly contraindicated by immunological distance data. Neck spreading therefore may have evolved several times within the subfamily Xenodontinae"--P. [1].
12 p. : ill. ; 26 cm.
Includes bibliographical references (p. 11-12).