Euryachen seuzei a new genus and species of Placusini (Coleoptera: Staphylinidae Aleocharinae) from Brazil Pires-Silva, Carlos M. Zootaxa 2023 2023-01-24 5230 4 467 477 Pires-Silva, 2023 Pires-Silva 2023 [238,372,1303,1330] Insecta Staphylinidae Euryachen Animalia Coleoptera 1 468 Arthropoda genus gen. nov.    Typespecies  Euryachen seuzei gen. et sp. nov., present designation.   Diagnosis:Head spherical, widest behind eyes; with a broad and distinctive neck occupying the entire basal head width. Posterior angles of head indistinct. Antennomeres VII–X distinctively transverse. Mandibles with dorsal molar area with seven transverse rows of large denticles. Maxillae with galea slightly longer than lacinia; lacinia with about nine large teeth apically. Labium short, 2-articulated. Ligula short and broadly rounded. Pronotum transverse; anterior margin straight with fore angles short and rounded; posterior margin broadly and weakly arcuate, hind angles straight. Tibial spur present, formula 2-1-1. Last tarsomeres of all legs longer than the previous together. Tarsal formula 4-4-5. Abdomen parallel-sided; segments III–VII with two pairs of paratergites each; tergite V of males bearing 7–9 spine-like thicker bristles near middle; tergite VII slightly broader at posterior region; on males with thicker and darker bristles on lateral margins.  Comparative notes:The genus  Euryachen  gen. nov., is most similar to  EuviraSharpin overall appearance, but is distinguishable in Placusinifrom any other genus by a combination of unique characters: distinct and broad neck, occupying the entire basal head width (unique in the tribe), distinct and short anterior angles of pronotum, and antennomeres VII–X transverse. Moreover, members of Placusinimay also present secondary sexual characteristics. For instance, males of  PlacusaErichsonhave modified tergite VIII, forming band of varied sizes spines on posterior margin, while in males of  Euvirathe tergite VIII is larger and prolonged posteriorly. Males of  Euryachenhave thicker spine-like bristles on tergite V, and also bear thick bristles on lateral margins of tergite VII. As far as is known, this kind of sexual dimorphism is unique in Placusini. The pronotum in the tribe is in mostly transverse. In  Euryachen, the pronotum is transverse, similar to that of  Euvira, but is distinguishable by the short anterior angles, contrasting with the broadly rounded angles, and in some cases indistinct, of  Euviraspecies.Further, members of  Euvirahave straight and distinctive posterior angles on the head, while it is indistinct in  Euryachendue to the presence of the broad neck. The tergite VIII in  Euryachenis a transverse to subquadrate plate in both males and females, contrasting with the modified tergite VIII from males of  Placusa(above mentioned); in species of  Placukornait is like a conspicuously curved horn. In  Euvira, the tergite VIII is broader in males rather than females.   Etymology. The generic name is a junction of two Greek words, ευρύς ( evrýs, wide) and the nominative singular noun αὐχήν ( aukhḗn, neck). Thus,  Euryachenmeans “wide neck” in allusion to the large neck distinctively in the tribe. Gender masculine.    Updated Key to the genera of Placusini (modified from Santiago-Jiménez & Santiago-Navarro 2016)    1 Head with distinct neck................................................................................ 2  - Head with an indistinct neck............................................................................ 4   2 Neck broad, almost same width of head; head spherical with indistinct posterior angles; anterior angles of head shortly rounded; males with thicker spine-like bristles on the central region of tergite V..........................   Euryachen gen. nov.  - Neck narrower than head. Head quadrate with strong posterior angles; anterior angles of pronotum broadly rounded; tergite V of males without spine-like bristles....................................................................... 3   3 Antennomeres 4–10 distinctively transverse; spermatheca rounded, stem somewhat triangular ( Pace 2008, fig 92)..................................................................................................  KirtusaPace  - Antennomeres 5–10 distinctively transverse; spermatheca not as above................................  EuviraSharp   4 Head rounded or transversally sub-orbicular; tergite VIII transverse, not modified...  SpeiraphallusaPace( Pace 2013; fig 1)  - Head transverse; tergite VIII not transverse, modified, bearing spines or as a curved horn............................ 5    5 Maletergite VIII with a variable number of small to large spines ( Klimaszewski et al. 2001; figs 33–49).......................................................................................................  PlacusaErichson  - Male and female tergite VIII without spines, forming a conspicuously curved horn ( Santiago-Jiménez & Santiago-Navarro 2016; figs 2, 11)...............................................................  PlacukornaSantiago-Jiménez