Paranonychus Briggs, 1971

Paranonychus brunneus (Banks, 1893).

The Paranonychidae can be diagnosed by their relatively complex glans (except Paranonychus) (Figure 7 and Suppl. material 2: Figure 4), and by their intestinal complex (Suppl. material 2: Figure 2). For all taxa that have been examined, the paranonychids possess a small D1 that is circular to subtriangular, and a simple and shorter OD3. The paranonychids are restricted to western North America and East Asia. In southern Japan the paranonychids are sympatric with Yuria and can be diagnosed by several characteristics: Yuria possesses a free ninth tergite, and the penis has a dorsal plate with fused stylus; the paranonychids do not have a free ninth tergite and the penis glans lacks a dorsal plate. In western North America, the paranonychids are sympatric and syntopic in surface habitats with the Cladonychiidae (Briggsus, Isolachus) and Cryptomastridae (Cryptomaster). The paranonychids can be differentiated from these families by the structure of D1: paranonychids possess a small circular to subtriangular unbranched D1, while Cladonychiidae and Cryptomastridae possess an elongate, triangular, and branched D1.

Paranonychus (Figure 1K). This trans-Beringian genus includes three known species: P. brunneus (Banks, 1893) distributed in the Coast and Cascade Ranges of Oregon and Washington with records extending north to Alaska; P. concolor Briggs, 1971, recorded from a single location in the southern Cascade Range of Oregon; and P. fuscus found throughout northern Honshu in Japan.

Metanonychus Briggs, 1971. This genus and all species were described by Briggs (1971) and are restricted to the moist forests of the Pacific Northwest of North America. Metanonychus includes three species: M. nigricans Briggs, 1971 with two subspecies, M. n. nigricans and M. n. oregonus, found in Oregon; M. setulus Briggs, 1971 with five subspecies, M. s. setulus, M. s. cascadus, M. s. mazamus, M. s. navarrus, and M. s. obrieni, found in Oregon, Washington, and northern California; and M. idahoensis Briggs, 1971 found in northern Idaho.

Sclerobunus Banks, 1893 (Figure 1L). Recently revised by Derkarabetian and Hedin (2014), Sclerobunus is distributed throughout western North America and currently includes 12 species divided into three species groups. The nondimorphicus group includes S. nondimorphicus Briggs, 1971 from Oregon, Washington, and British Columbia, and S. idahoensis Briggs, 1971 from northern Idaho. The cave-obligate cavicolens group includes: Sclerobunus cavicolens (Banks, 1905) restricted to Lewis and Clark Caverns, Montana; Sclerobunus ungulatus (Briggs, 1971) from caves in Great Basin National Park, Nevada; Sclerobunus madhousensis (Briggs, 1971) from caves near Provo, Utah. The robustus group includes the widespread S. robustus (Packard, 1877), S. glorietus Briggs, 1971, and S. skywalkeri Derkarabetian & Hedin, 2014, all distributed throughout the high elevation forests of the southwestern United States, and S. jemez Derkarabetian & Hedin, 2014, S. klomax Derkarabetian & Hedin, 2014, S. speoventus Derkarabetian & Hedin, 2014, and S. steinmanni Derkarabetian & Hedin, 2014, which are all troglomorphic species restricted to cave and talus habitats along the eastern edge of the southern Rocky Mountains in New Mexico and Colorado.

Kaolinonychus Suzuki, 1975. This monotypic genus endemic to South Korea is recorded mostly from caves. Kaolinonychus coreanus (Suzuki, 1966) includes two subspecies K. c. coreanus and K. c. longipes.

Metanippononychus Suzuki, 1975. (Figure 1M). Endemic to Japan, Metanippononychus is restricted to southern Honshu, Shikoku, and Kyushu and includes four species: M. daisenensis Suzuki, 1975; M. iriei Suzuki, 1975, with two subspecies M. i. iriei and M. i. yakuensis; M. iyanus Suzuki, 1975; M. tomishimai Suzuki, 1975, with two subspecies M. t. tomishimai and M. t. awanus.

Nippononychus Suzuki, 1975. A monotypic genus endemic to Japan, Nippononychus japonicus (Miyosi, 1957) is restricted to southern Honshu and Shikoku.

Zuma (Figure 1N). Zuma includes two species restricted to forests of central and northern California: Zuma acuta Goodnight & Goodnight, 1942 restricted to the coastal forests south of San Francisco; Zuma tioga Briggs, 1971 found in the central and northern Sierra Nevada range.

Izunonychus Suzuki, 1975. A monotypic genus endemic to Japan, Izunonychus ohruii Suzuki, 1975 is restricted to the Izu peninsula and Hakone area in central Honshu.

Kainonychus Suzuki, 1975 (Figure 1O). A monotypic genus endemic to Japan, Kainonychus akamai (Suzuki, 1972) includes two subspecies, K. a. akamai distributed throughout northern Honshu and K. a. esoensis restricted to Hokkaido.

In this study all genera in the Paranonychidae have been sampled and the generic relationships are consistent and highly supported across all analyses (Figs 4, 5). Although the study of Derkarabetian et al. (2010) only included North American taxa, the relationships of paranonychids recovered here are the same, notably Paranonychus as the earliest diverging genus, and a sister relationship between Sclerobunus and Metanonychus. The familial name Sclerobunidae has been used previously (Giribet et al. 2010) for the “northern triaenonychids”. However, Paranonychidae and the subfamily Paranonychinae Briggs, 1971 have priority over the names Sclerobunidae and Sclerobuninae Dumitrescu 1976.

The Japanese genera Metanippononychus and Nippononychus show levels of UCE divergence consistent with congeners (Figs 4, 5). Intermediate morphological forms between Nippononychus japonicus and Metanippononychus daisenensis can be found where the two species come into contact (Tsurusaki pers. obs.). These genera are differentiated only by tarsal claw structure: Metanippononychus possessing a ventral tooth on the median prong of the hind claws. The original drawings of male genitalia show that M. daisenensis and N. japonicus differ in the width of the stylus (Suzuki 1975b). However, the penis of N. japonicus is highly similar to that of the geographically proximate M. tomishimai tomishimai.

Kury et al. (2014) includes Paranonychus fuscus (formerly Mutsunonychus fuscus) as a synonym of Paranonychus brunneus (Banks, 1893) based on Shear’s (1986) statement “Paranonychus brunneus (=Mutsunonychus fuscus Suzuki; Paranonychidae)”. Later in Shear and Derkarabetian (2008), the genus Mutsunonychus was formally synonymized under Paranonychus, and although a potential species level synonymy was noted, it was not formally established. The levels of UCE divergence between P. brunneus and P. fuscus are consistent with species level divergences compared to other pairs of congeneric taxa included (Figs 4 and 5), and as such, P. fuscus is again treated as a distinct species here.