Review of Mesozoic Perissommatidae (Insecta: Diptera) Author Lukashevich, Elena D. Author Blagoderov, Vladimir A. text Zootaxa 2020 2020-01-08 4718 4 481 496 journal article 24411 10.11646/zootaxa.4718.4.3 c3fec010-6e0c-41e3-aece-3c6caccc951a 1175-5326 3602674 32C51811-97BA-40E4-B503-F25F8C4CF98A Collessomma gen. nov. ( Figures 2–6 ) urn:lsid:zoobank.org:act: E4 CEAD 3D-3FA8-4B7A-B54F-E661FEFB6995 Type species Collessomma sibirica sp. nov. Etymology. The generic epithet refers to Donald Henry (Don) Colless, an outstanding expert on Australian Diptera , who established the family Perissommatidae , and to the Greek term omma —eye. The name is feminine. Diagnosis. Eyes in male holoptic, with facets of different size, veins with macrotrichia, dense on radial ones except for R 5 , discal cell elongate, 1/4 wing length, CuP ending at level m-cu , anal lobe present. Description. Antenna moniliform, rather short and stout, with 11 segments, flagellum not clearly differentiated, segments 2 and 3 (pedicel and first flagellomere) enlarged, all segments with fine setae only ( Figs 2C , 5A, B, F ). Ocelli probably absent. Eyes in male holoptic, with facets of different size, without disconnected zone ( Figs 2C, D, F ; 5A, B ); in female dichopic, with facets of the same size ( Fig. 6B ). Mouthparts very short ( Figs 2D , 5A ). Mesonotum arched anterodorsally, scutellum separated from postscutum by distinct suture, metanotum very large ( Figs 2A , 3A , 5H ). Legs slender, with small tibial spurs, femur slightly expanded, first tarsomere longest, forth tarsomere shortest, empodium and pulvilli well-developed, narrow; pubescence of empodium and pulvilli invisible ( Figs 3A, B , 4B , 5C ). Wing relatively broad, longer than abdomen, with anal lobe but without alula, with numerous macrotrichia on pterostigma and on veins, denser on radial veins ( Figs 2A, E , 3A, C , 4F , 5D, H , 6A, C ). R 1 apex expanded; fork R 3+4 forms relatively acute angle, about 45°; crossvein r-m proximal to im and distal to m-cu ; discal cell elongate, 1/4 wing length, CuP ending at level m-cu ( Figs 2A, E , 3A, C , 4A, D, F , 5H , 6C ). Male hypopygium narrower than VIII abdominal segment and relatively simple, not rotated, gonocoxites elongate and massive, gonostyli simple, stout; ninth tergite prominent ( Figs 2B , 4C, E , 5D, E ). Female terminalia with large, prominent bilobed eighth sternite, cerci prominent, well chitinized but not horny, and with numerous setae; three sclerotized spermathecae ( Figs 4G , 5G , 6A ). Species included. Besides type species, C. gnoma gen. et sp. nov. from the same locality and C. mongolica gen. et sp. nov. from Lower Cretaceous of Mongolia , described below. Remarks. Characters typical of the family are observed in the wing venation of the new genus: the costal vein extends along the entire wing, strongly thickened at the anterior and distal margins, weak but distinct along the posterior margin; the peculiar position of the pterostigma between R 1 and R 3 ; a forked anterior branch of Rs, R 3+4 combined with a simple posterior branch R 5 ; r–m connects R 5 and M 1+2 ; M stem very weak, fold-like, M 1+2 is forked, М 3+4 is simple; m–cu is positioned in the proximal part of the wing; CuP is distally reduced ( Figs 2A, E , 3A, C , 4A , 5H , 6C ). As all members of subfamily Perissommatinae Collessomma gen. nov. has short Sc not ending at C, short R 1 (about half of the wing length); R 3 distally closer to R 4 than to R 1 ; r-m in proximal half of wing and m–cu ending on M 3+4 ( Figs 3A , 4A ). Tibial spurs are found in the new genus but they are unknown in the type genus Perissomma . In extant Perissommatidae “V-shaped suture of the tipuloid type ” present, in the new genus transverse suture on scutum present with certainty, but its shape is unclear. However, some other familial characters (coinciding with that of Perissomma ) are observed in body structures: antenna moniliform, with 11 segments, flagellum not clearly differentiated, pedicel and first flagellomere enlarged ( Fig. 5B ), thorax with large metanotum; halters long-stemmed; legs with well-developed empodium and pulvilli ( Figs 3A, B , 4B ); well-developed eighth abdominal segment; male hypopygium narrower than VIII abdominal segment and relatively simple, ninth tergite prominent ( Figs 2A, B , 4C ).