Systematic Entomology (2007), 32, 635–667 DOI: 10.1111/j.1365-3113.2007.00392.x Thoracic morphology of adults of Derodontidae and Nosodendridae and its phylogenetic implications (Coleoptera) SI-QIN GE 1,2 , ROLF G. BEUTEL 2 and X I N G - K E Y A N G 1 1 Institute of Zoology, Chinese Academy of Sciences, Beijing, China, and 2 Institut fu¨r Spezielle Zoologie und Evolutionsbiologie, FSU Jena, Jena, Germany Abstract. External and internal structures of the thorax of six adult representa- tives of the families Derodontidae and Nosodendridae were examined. A detailed description of the skeleton and musculature is presented for Derodontus maculatus and Nosodendron sp. Phylogenetically relevant characters are discussed and analysed cladistically. A basal origin of Derodontidae within Polyphaga and a sister-group relationship between this suborder and the remaining Coleoptera are not supported. Muscular and skeletal features of Derodontidae are largely consistent with the typical polyphagan pattern and the group is characterized by many specialized features. Previous references to the family as ‘primitive’ are unjustified. The absence of a firm connection between the meso- and metaventrite is a secondary feature, as seen in Scirtoidea and some members of Leiodidae. The contact of the metanepisternum with the mesocoxal cavity is probably also an autapomorphic condition. Two derived muscular features are shared by Dero- dontidae and Nosodendridae, and several muscle losses are shared by these two families and Scirtoidea and Dascillidae. The monophyly of Derodontidae and a sister-group relationship between Peltastica and the remaining genera are confirmed. Laricobius and Nothoderodontus are probably sister groups. Nosoden- dron is characterized by several autapomorphic features. Whether the flight musculature is reduced in all members of Nosodendridae is unclear. Introduction Derodontidae were considered one of the most enigmatic beetle taxa by Crowson (1944) and this is reflected by statements on its phylogenetic position and its placement in classifications. The group was considered as one of the ‘most primitive’ polyphagan groups by Crowson (1955, 1959) and Lawrence & Newton (1995), and was referred to as a ‘primitive family’ of Cucujiformia by Lawrence (1991), with affinities with Cucujoidea and Dermestidae. A superfamily Derodontoidea also including Nosodendridae and Jacobsoniidae was proposed in the classification of Lawrence (1991) (see also Beutel, 1996). By contrast, Lawrence & Newton (1995) placed Derodontoidea, com- prising only Derodontidae, at the beginning of the series Bostrichiformia. Despite the widely recognized phylogenetic importance of the group, comparatively little is known about its morphol- ogy. Although larval features were studied by Franz (1958), Fukuda (1963), Lawrence & Hlavac (1979) and Beutel (1996), and selected features of adults by Hlavac (1972, 1975), Lawrence & Hlavac (1979) and Lawrence (1985), very little is known about the internal structures of immature stages and adults. Lawrence (2001) emphasized the impor- tance of detailed morphological studies of supposedly ‘basal’ polyphagan taxa, including muscular dissections. This inspired us to carry out the present investigation of thoracic features of Derodontidae and Nosodendridae. In agreement with Lawrence’s suggestion, our study empha- sized internal structures, especially the muscular system. The basal branching pattern within the immensely com- plex suborder Polyphaga remains insufficiently resolved, Correspondence: R. Beutel, Institut fu¨r Spezielle Zoologie und Evolutionsbiologie, FSU Jena, 07743 Jena, Germany. E-mail: Rolf. Beutel@uni-jena.de # 2007 The Authors Journal compilation # 2007 The Royal Entomological Society 635