Internal and external features of Tetraphalerus bruchi were studied using X-ray microtomography (µ-CT) and other techniques, and head structures were described in detail. µ-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: (†Tshekardocoleidae + (†Permocupedidae, †Rhombocoleidae + (†Triadocupedidae + ((Adephaga + (Myxophaga + Polyphaga))) + Archostemata s.str. [including Jurodidae]))). Sikhotealinia is placed as sister group of †Jurodes (Jurodidae), and Jurodidae as sister group of the remaining Archostemata (Bayesian analysis) or of a clade comprising Micromalthidae, Crowsoniellidae, †Ademosynidae, †Schizophoridae and †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 †Tshekardocoleidae), the formation of a closed subelytral space (Coleoptera excluding †Tshekardocoleidae and †Permocupedidae), the reduction of two apical antennomeres, and the loss of the broad prothoracic postcoxal bridge (Coleoptera excluding †Tshekardocoleidae, †Permocupedidae and †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.

© The Willi Hennig Society 2007.