Recent surveys of the plethodontid salamander fauna of Oaxaca, Mexico, disclosed the existence of a new, morphologically distinct arboreal species of the genus Pseudoeurycea . The new species, described here, is from the Sierra Mazateca in northern Oaxaca. Sequences of 1833 base pairs of the 16S, cytochrome b and ND4 mitochondrial DNA (mtDNA) genes from the new taxon were used to assess its phylogenetic position. Previous phylogenetic analyses based on mtDNA supported recognition of four clades within Pseudoeurycea : P. bellii , P. gadovii , P. juarezi and P. leprosa-Lineatriton species groups. One additional species, P. unguidentis , was not closely allied to any of the four groups. Re-analysis including the additional sequences reported here establishes a sister-group relationship between the new species and P. unguidentis . Moreover, it supports this clade as part of the P. juarezi species group. [ABSTRACT FROM AUTHOR]