Arachnocorys pentacantha (Popofsky, 1913) Petrushevskaya, 1971

Plate 5, Figs. 8–9B.

Arachnocorys pentacantha n. sp., Popofsky, 1913, text-figs. 84–86; pl. 22, figs. 5–6.

Arachnocorys pentacantha Popofsky, Petrushevskaya, 1971, pl. 65, figs. 8–9; pl. 66, figs. 5–6.

? Arachnocorys pentacantha Popofsky, Nishimura and Yamauchi, 1984, pl. 55, figs. 8a–8b.

non Arachnocorys cf. pentacantha Popofsky, Nishimura and Yamauchi, 1984, pl. 24, figs. 11a–11b.

non Arachnocorys pentacantha Popofsky, Okazaki et al., 2005, fig. 12.19.

Arachnocorys pentacantha Popofsky, Matsuoka, 2009, fig. 2-53, fig. 3-44,?fig. 3-43.

non Archiperidium pentacanthum (Popofsky) nov. com., Matsuzaki et al., 2014, pl. 3, fig 2.

Arachnocorys cf. pentacantha sp 1, Trubovitz et al., 2020, supplementary data 7.

Remarks. This species was originally described by Popofsky (1913), but was amended by Petrushevskaya (1971) It often has variable development/preservation of the thorax and arachnoidal filaments, so shows some variation in the fossil record. Petrushevskaya (1971) noted that some specimens of Arachnocorys pentacantha were significantly larger, and have relatively smaller gaps between the cephalis and thorax, than others. It is unclear whether or not she considered these specimens to belong to Arachnocorys pentacantha, as they were referred to as Arachnocorys cf. pentacantha in the caption of pl. 65, figs. 10–11, but were not explicitly referred to as cf. pentacantha in the species description. In our study, we also observed that there were two similar forms resembling Arachnocorys pentacantha; the larger form we have broken out as the separate subspecies Arachnocorys pentacantha wanii n. subsp. (Pl. 5, Figs. 1A – 7B). Matsuzaki et al. (2014) listed Arachnocorys pentacantha as Archiperidium pentacanthum (Popofsky) nov. com., but did not provide a justification for the genus reassignment. In addition, the specimen figured by Matsuzaki et al. (2014) appears to have a relatively larger, more triangular cephalis, negligible gaps between thorax and cephalis, and weaker apical spine, compared to the specimens figured by Petrushevskaya (1971) and those observed in this study. These characteristics may indeed justify placing the species figured by Matsuzaki et al. (2014) into Archiperidium; however, we do not consider this species to be the same as the one described by Popofsky (1913) and amended by Petrushevskaya (1971).

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Range. Late Pliocene—Recent in the EEP (Table 1).