On the head morphology of Tetraphalerus, the phylogeny of Archostemata and the basal branching events in Coleoptera

Internal and external features of Tetraphalerus bruchi were studied using X-ray microtomography (mu-CT) and other techniques, and head structures were described in detail. mu-Ct is highly efficient for the assessment of anatomical data. A data matrix with 90 morphological characters of recent and fossil beetles was analyzed with different approaches (parsimony, Bayesian analysis). The results of the parsimony analysis resulted in the following branching pattern: (dagger Tshekardocoleidae + (dagger Permocupedidae, dagger Rhombocoleidae + (dagger Triadocupedidae + ((Adephaga + (Myxophaga + Polyphaga))) + Archostemata s.str. [including Jurodidae]))). Sikhotealinia is placed as sister group of dagger Jurodes (Jurodidae), and Jurodidae as sister group of the remaining Archostemata (Bayesian analysis) or of a clade comprising Micromalthidae, Crowsoniellidae, dagger Ademosynidae, dagger Schizophoridae and dagger Catiniidae. The monophyly of Ommatidae and Cupedidae is well supported and Priacma is placed as the sister group of all other Cupedidae. Important events in the early evolution of Coleoptera are the shortening of the elytra and the transformation of the elytral venation (Coleoptera excluding dagger Tshekardocoleidae), the formation of a closed subelytral space (Coleoptera excluding dagger Tshekardocoleidae and dagger Permocupedidae), the reduction of two apical antennomeres, and the loss of the broad prothoracic postcoxal bridge (Coleoptera excluding dagger Tshekardocoleidae, dagger Permocupedidae and dagger Rhombocoleidae). Plesiomorphic features preserved in extant Archostemata are the tuberculate cuticle, the elytral pattern with parallel longitudinal ribs and window punctures, a mesoventrite with a transverse ridge, triangular mesocoxae with a distinct meron, and the exposed metatrochantin. The fossils included in the analyses do not only contribute to the reconstruction of character evolution but also influence the branching pattern. An understanding of the major evolutionary events in Coleoptera would not be possible without considering the rich fossil record of Permian and Mesozoic beetles. (C) The Willi Hennig Society 2007.