A taxonomic monograph of the liphistiid spider genus Heptathela, endemic to Japanese islands

Among the eight extant genera of primitively segmented spiders, family Liphistiidae, two are confined to East Asian islands, Heptathela Kishida, 1923 and Ryuthela Haupt, 1983. In this paper, a taxonomic revision of the genus Heptathela (Heptathelinae) from Kyushu and Ryukyu archipelago, Japan is provided. This study follows a multi-tier species delimitation strategy within an integrative taxonomic framework that is presented in a parallel paper, in which diagnosable lineages are considered as valid species. There, the initial hypothesis of species diversity (19) based on classical morphological diagnoses is tested with multiple species delimitation methods aimed at resolving conflict in data. This revision follows those analyses that converge on the species diversity of 20, which includes a pair of cryptic species that would have been undetected with morphology alone. After this revision, eight previously described species remain valid, two junior synonyms are proposed, and 12 new Heptathela species are described based on diagnostic evidence. To ease identification and to hint at putative evolutionary units, Heptathela is divided into three groups. The Kyushu group contains H. higoensis Haupt, 1983, H. kikuyai Ono, 1998, H. kimurai (Kishida, 1920), and H. yakushimaensis Ono, 1998; the Amami group contains H. amamiensis Haupt, 1983, H. kanenoi Ono, 1996, H. kojima sp. nov., H. sumiyo sp. nov., and H. uken sp. nov.; and the Okinawa group contains H. yanbaruensis Haupt, 1983, H. aha sp. nov., H. gayozan sp. nov., H. kubayama sp. nov., H. mae sp. nov., H. otoha sp. nov., H. shuri sp. nov., H. tokashiki sp. nov., H. unten sp. nov., and H. crypta sp. nov. Heptathela helios Tanikawa & Miyashita, 2014 is not assigned to a species group. A combination of diagnostic tools augments the morphological diagnoses that, in isolation, would be prone to error in morphologically challenging groups of organisms.