Review of the genus popilius and preliminary phylogeny of Passalidae (Coleoptera)

Preliminary phylogenetic analyses of Passalidae and the genus Popilius are presented based on 207 characters for the family level part of this study and 232 characters for the generic portion. The strict consensus and successive approximation trees show that the New World passalid fauna is monophyletic, and that Popilius is paraphyletic and intertwined with several closely related, also paraphyletic, genera (at least Heliscus, Odontotaenius and Petrejoides). An unrooted analysis of Popilius identified four species groups, two that are monophyletic, one that is probably paraphyletic (more closely related to Petrejoides than to other members of Popilius) and one for a distinct species, the single specimen of which was not available for examination. New character systems were investigated and the metendosternite, eversible internal sac of the male genitalia, prostheca of the right mandible, epipharynx, and hypopharynx provided useful characters to supplement those traditionally used. A new autapomorphy for the family is reported, an organ on the inner surface of both elytral humeri. The structure has a membranous covering and appears to contact an apophysis on the base of the wing. Its position and structure suggest that it may be a sound receptor. A rigorous investigation of the relationships among the genera closely related is required to define generic boundaries and identify the out-group taxa most appropriate for the analysis of the component taxa.