DESCRIPTION OF A NEW SPECIES OF GYRINICOLA YAMAGUTI, 1938, FROM THE MONTEZUMA FROG, RANA MONTEZUMAE, IN THE TRANSITION ZONE BETWEEN THE NEARCTIC AND NEOTROPICS.

The present work includes the description of Gyrinicola pilyolcatzin n. sp. (Nematoda: Oxyurida) collected from the large intestine of tadpoles of the Montezuma frog, Rana montezumae. Nuclear DNA and mitochondrial DNA generated via a combination of Sanger and Next Generation shotgun sequencing were used to reconstruct the species in a phylogenetic context, by including the other 4 recognized species in the genus present in North America, namely, Gyrinicola batrachiensis, Gyrinicola armatus, Gyrinicola gulabrevioris, and Gyrinicola moohsia. The distinctiveness of the species was supported by an analysis of branching patterns using Bayesian Poisson tree processes. We used morphometric evidence to enumerate the diagnostic characters that define members of this unique clade within the genus. The species shares a common ancestor with G. gulabrevioris and G. moohsia; yet it is meristically similar to G. armatus. This is the first species of the genus described in Mexico and the fifth species described in the Nearctic, as it is present in the Transvolcanic Axis of Mexico, which acts as a transition zone between the Nearctic and the Neotropics. A dichotomous key to the species in the Nearctic is offered.