†Peltosynidae, a new beetle family from the Middle–Late Triassic of Kyrgyzstan: its affinities with Polyphaga (Insecta, Coleoptera) and the groundplan of this megadiverse suborder

Middle–Late Triassic fossil beetles previously assigned to Polyphaga <i>incertae sedis</i> and new material from this period are described and illustrated. †Peltosynidae fam. nov. is introduced to contain the type genus <i>Peltosyne</i>, and species <i>P. triassica</i> Ponomarenko, 1977, together with the new species <i>P. varyvrosa</i> sp. nov. Two new monospecific genera, <i>Gnathopeltos</i> gen. nov. and <i>Ofthalmopeltos</i> gen. nov., with type species <i>G. dixis</i> sp. nov. and <i>O. synkritos</i> sp. nov., are also included in †Peltosynidae. Morphological characters evaluated with respect to their phylogenetic significance confirm that the family belongs to the suborder Polyphaga, mainly supported by the apomorphic internalized propleura. †Peltosynidae is characterized by a large transverse head, long and prominent, strongly developed mandibles, a short prosternum with a narrow, relatively short prosternal process, an interlocking mechanism between this process and a groove of the anteromedian process of the mesoventrite, striated elytra, a short metakatepisternum, transverse coxae, and a short abdomen with five ventrites. The large and transverse head is a potential autapomorphy. †Peltosynidae do not fit into any of the seven extant major polyphagan infraorders (series). The presence of a mesothoracic transverse katepisternal ridge in †<i>Peltosyne</i> is a plesiomorphic feature distinguishing the new family from all other groups of the suborder and suggesting its placement in the stem-group of Polyphaga. The strongly prominent mandibles and the coarse body sculpture resemble features found in extant Archostemata. It is likely that the beetles were xylophagous and adapted to subcortical habitats, arguably maintaining plesiomorphies. The polyphagan groundplan is reconstructed based on recent phylogenies and features found in †Peltosynidae and other extinct and extant groups. A scenario for the evolution of non-archostematan beetles in the late Permian and early Mesozoic is presented. http://zoobank.org/urn:lsid:zoobank.org:pub:58428459-33EF-4C1C-AD69-A066D3D33ADF