Oniscidea of Liguria (north-western Italy), with the description of a new species (Malacostraca: Isopoda)

Terrestrial isopods (Isopoda: Oniscidea) are a diverse and ecologically important taxon, yet knowledge of their diversity in Italy remains uneven. Liguria, a small but biogeographically complex region of north-western Italy, had long lacked a synthesis of its oniscidean fauna despite the numerous studies carried out in early 20th-century. Here we provide a comprehensive assessment of Ligurian terrestrial isopod fauna based on a critical review of historical literature and examination of material preserved in museum collections or collected during recent field surveys. A total of 109 species in 38 genera and 18 families are recorded, representing more than one quarter of all terrestrial isopods known from Italy. Armadillidium genuaense n. sp. is described, and figures of several poorly described species are provided. Haplophthalmus portofinensis, Cylisticus ligurinus, and Armadillidium albigauni are considered junior synonyms of H. mengii, C. annulicornis, and A. gestroi, respectively. Three families and seven genera are recorded for the first time in Liguria, and three species—Trichoniscus darwini, T. nicaeensis and Caeroplastes porphyrivagus—represent new records for Italy. At the same time, five previously cited species could not be confirmed, and one is treated as species inquirenda. Chorological analysis underscores Liguria’s role as a biogeographic crossroad, with nearly half of the fauna belonging to Alpine or Apennine categories. A high level of endemism is observed, with 15 species restricted to the administrative region and 27 to the broader Ligurian geographic area. Persistent taxonomic uncertainties in some genera underscore the necessity of further revisions. By providing the first comprehensive assessment of the Oniscidean fauna from Liguria, this study establishes a necessary baseline for future research in the region.