Contribution to the knowledge of the oribatid mite genus Discoppia (Acari, Oribatida, Oppiidae)

The supplementary description of the oribatid mite species Discoppia (Cylindroppia) cylindrica (Perez-inigo, 1965) (Oribatida, Oppiidae) is presented, based on materials collected from deep layers of coastal sandy soils in the Republic of Dagestan, eastern Caucasus. The morphology of exobothridial seta, gnathosoma and ovipositor, and the identification of leg setae and solenidia are given for the first time for this species. The revised generic diagnosis, identification key, distribution, and habitats of all known representatives of Discoppia Balogh, 1983 are presented. Some taxonomic nuances within Discoppia are discussed, resulting in the following proposals: Oppia bifidus Bayoumi and Al-Khalifa, 1985 is a junior synonym of D. (C.) cylindrica; Oppia agricola Fujikawa, 1982 is not synonym of D. (C.) cylindrica and transferred to the genus Microppia Balogh, 1983; Oppia tenuis Hammer, 1958 is not representative of Discoppia; Discoppia (Cylindroppia) rostroincisa Subias and Rodriguez, 1986 n. stat. (instead of the existing subspecies status). Together with D. (C.) cylindrica, in the same samples, two rare Oppiidae species were found: Oxyoppia (Oxyoppiella) minuscula Hugo-Coetzee, Lotfollahi, Abbasi-Kalo and Movahedzade, 1917 (known only from the open habitats in Iran) is first recorded in Russia; Graptoppia (Stenoppia) boucheri Ermilov and Frolov, 2021 (known from passalid beetles collected in Ghana and Gabon, West Africa) is first found in the Palaearctic. Both findings in Dagestan are among the northernmost records of their semicosmopolitan subgenera.