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 † Hydrophilopsia Ponomarenko, 1987 Hydrophilopsia Ponomarenko, 1987: 93 . Type species. Hydrophilopsia longitarsalis Ponomarenko, 1987 (by original designation). Time range. Latest Jurassic, Tithonian, ca. 151–146 mya. Diagnosis. Adult : Head and pronotum without setiferous granules, gula wide, pronotal flanks extremely wide, elytra without elevated costae, legs with dense series of swimming hairs on tibiae and tarsi; it is also probable that the pronotum lacks longitudinal grooves and that the median portion of frontoclypeal suture is not grooved (both these characters are incompletely preserved in the single specimen available). In the helophorid lineage, the extremely wide pronotal flanks delimited by a non-sinuate inner ridge are only developed in the modern Helophorus subgenera Empleurus Hope, 1838 and Orphelophorus Orchymont, 1927 ; both of them bear very distinct granulation on the head and pronotum, lack swimming hairs on legs and bear strongly costate elytra. Taxonomic note. The genus is largely defined by plesiomorphies, but bears at least one autapomorphy, i.e. extremely wide pronotal flanks, hence it may represent an extinct late Jurassic clade of the helophorid lineage. All characters shared between H. longitarsalis ( type species) and the remaining species assigned previously to this genus are plesiomorphic and Hydrophilopsia in its original concept seems to be paraphyletic or polyphyletic for that reason. In order to keep Hydrophilopsia monophyletic and easily diagnosable, we are excluding all other species into a separate genus Laetopsia gen. nov. , which makes Hydrophilopsia a monotypic genus confined to the Latest Jurassic.