Unravelling a tangle of Mexican serpents: a systematic revision of highland pitvipers

As most recently recognized, the name Cerrophidion barbouri Dunn, 1919, refers to a highland species of pitviper endemic to Guerrero, Mexico, of which Agkistrodon browni Shreve, 1938, is considered a junior synonym. This species is rarely collected and prior to recent decades it was known from only a few specimens. A careful re‐examination of nearly all known specimens of C. barbouri and the type series of A. browni reveals that both names represent valid species and we therefore resurrect A. browni . Both species are extremely variable with respect to cephalic scalation and colour pattern, which has previously confounded efforts to identify them. We provide phylogenetic analyses using both Bayesian and maximum parsimony criteria of New World pitvipers to investigate the phylogenetic position of A. browni and C. barbouri . Our phylogenetic tree, based on 2235 bp of mitochondrial data [12S, 16S, cytochrome b (cyt b ), NADH dehydrogenase subunit 4 (ND4)], strongly supports a clade consisting of A. browni , C. barbouri , and Ophryacus melanurus , which has a distant sister relationship to Ophryacus undulatus . Based on the deep phylogenetic divergences amongst these species and distinctive morphology we recommend that a new genus be recognized for A. browni , C. barbouri , and O. melanurus . Finally, we revise the genera Cerrophidion and Ophryacus in accordance with our new classification. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society , 2011, 163 , 943–958.