An extraordinary case of elytra loss in Coleoptera (Elateroidea: Lycidae): discovery and placement of the first anelytrous adult male beetle Author Ferreira, Vinicius S. Natural History Museum of Denmark, Zoological Museum, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark vinicius.sffl@gmail.com Author Barbosa, Felipe Francisco Laboratório de Entomologia, Departamento de Zoologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro, A 1 - 107, Bloco A, Avenida Carlos Chagas Filho, 373, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, Brazil Author Bocakova, Milada Department of Biology, Faculty of Education, Palacky University, Purkrabska 2, CZ- 77140, Olomouc, Czech Republic Author Solodovnikov, Alexey Natural History Museum of Denmark, Zoological Museum, University of Copenhagen, Universitetsparken 15, 2100 Copenhagen, Denmark text Zoological Journal of the Linnean Society 2023 2023-07-01 199 2 553 566 http://dx.doi.org/10.1093/zoolinnean/zlad026 journal article 10.1093/zoolinnean/zlad026 0024-4082 8432514 5F8CB822-E5A6-4E68-8DB6-A5E07104F898 Genus Xenomorphon gen. nov. ( Figs 2–4 ) Zoobank registration. hưp://zoobank.org/ urn:lsid:zoobank. org:act: D958AFA5-4ABA-4AD4-B3DD-7B40E67BCC35 Differential diagnosis. Body dark brown, compressed, elytra and membranous wings absent ( Fig. 2A ). Pronotum subquadrate, with a median longitudinal carina developed, scutellar shield absent ( Fig. 2A, 2D ). Antennae inserted on gibbous prominence, distinctly serrate from antennomeres III–X, with pedicel ca. 3× longer than antennomere III ( Fig. 2A , 3C ). Maxillary, labial palps and mandibles fully developed ( Fig. 2E ). Legs short and stubby, tibiae tapered basally, gradually expanding towards the apex ( Fig. 2B ). Male genitalia distinctly trilobate ( Fig. 2G ). Etymology. The name of this genus is an allusion to the unique appearance of the studied specimen, which at first thought was not even considered to be a beetle. Xeno‐ , from the Greek, ξένος, meaning strange, alien, exotic or different, and morphon , from the Greek μορφῶν, meaning of shape or form. Gender masculine. Type species. Xenomorphon baranowskii sp. nov. Description of adult male. General dorsal coloration dark brown, pedicel slightly lighter, yellowish ( Fig. 2A ). Body moderately setose, with short, decumbent yellow setation throughout ( Fig. 2A, B ). Head: as long as wide, widest at eyes, posteriorly covered, in part, by pronotum, hypognathous, inclined, frons strongly bulgy, bearing pits behind antennal insertion ( Fig. 2A–C, E ). Posterior margin of epistoma clearly emarginate; labrum distinct from clypeus, transverse and small, apparently moveable and connected to clypeus with membrane. Eyes hemispherical, projecting anterolaterally in dorsal view, coarsely granulate ( Fig. 2A–C, E ). Antennae: distinctly serrate from antennomere III–IX, densely setose, dorsoventrally flaưened from III–XI, inserted in gibbous prominence at anterior distal portion of head, 11-segmented; in resting position reaching to basal half of body length ( Fig. 2A, C ). Scape pyriform, approximated at base by half distance of scape width, subconical ( Fig. 2C ); pedicel minute, ca. 4× shorter than scape; antennomeres III-IX slightly increasing in length towards apex ( Fig. 2A, B ); antennomere XI round apically ( Figs 2A , 3A ). Mouthparts: mandibles small, hook-shaped, opposable ( Fig. 2E ). Maxillary palp four-segmented ( Fig. 3B ); palpomere II elongate, as long as the sum of I + III + IV ( Fig. 2E ); terminal palpomeres abruptly acuminate ( Fig. 2E ). Labial palp threesegmented; terminal palpomere slightly blunt ( Fig. 2E ). Thorax, prothorax: pronotum nearly as long as wide, subrectangular ( Fig. 2A, D ); margins distinct and developed, angles round, bearing a median longitudinal carina developed throughout ( Fig. 2A, D ). Hypomeron slightly concave. Prosternum Y-shaped, posteriorly bifurcated apically, divergent towards procoxae ( Fig. 2B ). Protrochantins slender and exposed. Procoxal cavity open. Thorax, mesothorax: mesonotum plate-like, apically round, with angles slightly narrowed ( Fig. 2A, D ). Mesoscutum anteriorly divided by a tiny median suture (Supporting Information, Supplementary Material 4, Fig. S1 ). Elytra absent, with no vestiges of wing-base sclerites. Mesospiracles pill-shaped ( Fig. 2B ). Mesoventrite subtrapezoidal, with distinct visible suture connecting mesoventrite and mesanepisternum ( Fig. 2B ). Mesotrochantins slender and exposed. Thorax, metathorax: metanotum plate-like, having round angles; scutellar shield absent ( Fig. 2A, D ). Membranous wings absent, with no vestiges of wing-base sclerites ( Fig. 2A, D ). Metaventrite convex, posterolateral angles acute; metadiscrimen complete ( Fig. 2B ). Legs: short and stubby ( Fig. 2A, B ). Coxae conical, obliquely positioned, inner margin nearly contiguous but not touching ( Fig. 2A, B ); posterior face of metacoxae shallowly excavated. Trochanters shortened; subrectangular, not tubular ( Fig. 2A, B ). Femora and tibiae subequal in length ( Fig. 2A, B ); femora parallel sided; tibiae tapered basally, gradually expanding towards the apex ( Fig. 2A, B ). Tarsal formula 5-5-5; all tarsomeres narrowed; terminal tarsomere bearing two simple claws at end ( Fig. 2A, B ). Abdomen: with eight ventrites (sternites II–IX); ventrite seven medially apically notched; ventrite eight lanceolate, elongate, apically acuminate with apex blunt ( Fig. 2B ). Male genitalia typical elateriformia: trilobate, symmetrical ( Fig. 2G ); phallobase posteriorly round, median suture absent ( Fig. 2G ); parameres approximately half the length of median lobe, apices round ( Fig. 2G ); median lobe elongate, nearly parallel-sided, apically blunt, exposed portion approximately one-quarter longer the length of parameres + phallobase ( Fig. 2G ). Distribution. Mexico , Oaxaca , near the municipality of Valle Nacional (estimated 17°14ʹ48.85″N , 96°18ʹ15.31″W ; Fig. 3 ). Biology, immatures and females. Unknown. The only known specimen was collected in the leaf liưer of a pine–oak forest floor, and the female is presumed to be paedomorphic (see Discussion). Length (head through tip of abdomen). 2.9 mm . Width (across humerus). 0.5 mm .