Isoplastus Horn, 1880: 295 Brown 1937b: 173 Daffner 1988: 301 Isoplastus fossor Horn, 1880 Systematics and distributions of the genera Cyrtusa Erichson, Ecarinosphaerula Hatch, Isoplastus Horn, Liocyrtusa Daffner, Lionothus Brown, and Zeadolopus Broun of the United States and Canada (Coleoptera: Leiodidae: Leiodinae: Leiodini) Peck, Stewart B. Cook, Joyce Insecta Mundi 2013 2013-06-28 2013 310 1 32 8VRRT Horn Horn 1880 [192,412,513,538] Insecta Leiodidae Isoplastus Animalia Coleoptera 8 7 Arthropoda genus      Isoplastus Horn, 1880: 295;  Brown 1937b: 173;  Daffner 1988: 301. Typespecies:  Isoplastus fossor Horn, 1880, by monotypy.   Diagnosis.Body strongly convex. Antenna with 10 antennomeres, with strong 3-antennomere club. Mandibles forming semicircle when closed together; left mandible with large tooth in basal one-third. Ventral side of head with distinct antennal grooves below eyes. Mesosternum vertical between the mesocoxae, without median carina. Tibiae strong, widened and shovel-like; protibiae with distinct tarsal grooves, their outer margins with strong spines; outer margins of meso- and metatibiae strongly spinose. Tarsal formula 5-5- 4 inboth sexes. Males are distinguished by large tooth-like expansion of lower margin of metafemur.   Distribution.The distribution of the genus is eastern Holarctic; it also occurs in Mexico, with undescribed species in the northern Neotropics ( Newton 1998).