Revision of Mesozoic fossils of the helophorid lineage of the superfamily Hydrophiloidea (Coleoptera: Polyphaga) Author Fikáček, Martin Department of Entomology, National Museum, Kunratice 1, CZ- 148 00 Praha 4, Czech Republic; e-mail: mfikacek @ gmail. com & Department of Zoology, Faculty of Science, Charles University in Prague, Viničná 7, CZ- 128 44 Praha 2, Czech Republic; e-mail: jprokop @ natur. cuni. cz Author Prokin, Alexander Papanin Institute for Inland Water Biology, Russian Academy of Science, Borok, Russia; e-mail: prokina @ mail. ru & Voronezh State University, Research-Educational Centre “ Venevitinovo ”, Voronezh, Russia Author Angus, Robert B. Department of Entomology, The Natural History Museum, London, UK; e-mail: r. angus @ rhul. ac. uk Author Pono, Alexander Author Marenko Borissiak Paleontological Institute, Russian Academy of Sciences, Moscow, Russia; e-mail: aponom @ paleo. ru Author Yue, Yanli School of Life Science, Ningxia University, Ningxia, China; e-mail: yueyanli 0407 @ yahoo. cn Author Ren, Dong Author Prokop, Jakub Department of Zoology, Faculty of Science, Charles University in Prague, Viničná 7, CZ- 128 44 Praha 2, Czech Republic; e-mail: jprokop @ natur. cuni. cz text Acta Entomologica Musei Nationalis Pragae 2012 2012-06-30 52 1 89 127 journal article 10.5281/zenodo.5330604 0374-1036 5330604 † Laetopsia gen. nov. Type species. Hydrophilopsia shatrovskiyi Prokin, Ren & Fikáček, 2011 (by present designation). Time range. Early Cretaceous, ca. 145–112 mya. Diagnosis. Adult : Head and pronotum without setiferous granules, with grooved median portion of frontal suture, gula wide, pronotal flanks narrow, elytra without elevated costae, pale with dark stripes along striae; pronotum with a median longitudinal groove. Within the helophorid lineage, the genus is easily recognized according to the pale elytra with dark longitudinal stripes along elytral striae (unique character), narrow pronotal flanks (in contrast to wide flanks in Hydrophilopsia ) and a pronotum with a single median longitudinal groove and without setiferous granules (in Helophorus , the subgenera Orphelophorus and Mesohelophorus bear a reduced number (i.e. less than five) of longitudinal pronotal grooves but always bear very distinct setiferous granules on the pronotum). Etymology. From laetus (Latin), meaning joyful, pleasant, referring to the colourful elytra of this genus, plus the ending - psia derived from the genus Hydrophilopsia to which all species of the genus were assigned before. Gender: feminine. Taxonomic note. All species included herein share plesiomorphic characters with Hydrophilopsia but lack its only autapomorphy, i.e. the extremely wide pronotal flanks. In addition, all of them are readily distinguishable by pale elytra bearing dark stripes along elytral striae, a character which may represent an unique autapomorphy of the genus (but is unfortunately not preserved in Hydrophilopsia ). In absence of any additional data, both above differences indicate that the species with striped elytra form an easily diagnosable lineage separate from Hydrophilopsia , which is here described as Laetopsia gen. nov. The genus seems to have coexisted with Helophorus until the early Cretaceous and likely represents an extinct Mesozoic clade of the helophorid lineage.