The genus Dactylopisthoides is very similar to Dactylopisthes Simon, 1884, with the type species D. digiticeps (Simon, 1881). Both genera belong to the Savignia-genus group sensu Millidge (1977). The main diagnostic characters are as follows:

1. Formula of leg chaetotaxy: Dactylopisthoides – 2.2.2.1, vs 2.2.1.1 in Dactylopisthes;
2. Male carapace in Dactylopisthoides is unmodified, vs highly modified except for three Oriental species of which the generic assignment is doubtful;
3. Male palpal tibia in Dactylopisthoides is only slightly elongated dorsally, vs highly modified, sickle-shaped in Dactylopisthes, except for D. mirabilis (Tanasevitch, 1985), known from Kyrgyzstan (Tanasevitch 1985);
4. Epigyne in Dactylopisthoides with an opened fovea, its lateral walls with a distinct posterior projection on each (Figs 1F, 2F), vs fovea absent.

Small to medium erigonine. Male total length 1.50–1.80, carapace 0.63–0.79 long. Female total length 1.53–1.75, carapace 0.6–0.68 long. Carapace unmodified in both sexes. Formula of leg chaetotaxy 2.2.2.1, tibial spines short and weak. Metatarsi I–III each with trichobothrium. TmI 0.50–0.70. Male palpal tibia slightly modified, somewhat elongated dorsally. Paracymbium small and narrow, L-shaped, uncinate apically. Distal suprategular apophysis greatly enlarged, highly sclerotized, median tooth present. Embolic division relatively large, radix curved, with small outgrowth (= radical tooth); embolus proper short, thick, covered with short median membrane. Epigyne with cavity, lateral walls with distinct posterior projection in each.

An analysis of both somatic and copulatory organ structures of the type species of Uusitaloia and Dactylopisthoides has revealed that they are undoubtedly congeneric: all the species in both genera are of a similar small size, possess the same chaetotaxy (2221) and trichobothriotaxy (I–III; TmI: 0.64–0.65), and are characterized by the same conformation of copulatory organs in both sexes, differing from each other only in minor details: cf. Figs 1–3. Thus, the genus Uusitaloia Marusik, Koponen & Danilov, 2001 is to be considered a junior synonym of Dactylopisthoides Eskov, 1990.

Figure 1. 

Details of the male palp (A–E) and epigyne (F) of Dactylopisthoides hyperboreus Eskov, 1990, specimens from the type locality A–C right palp, retrolateral (A, B) and dorsal view (C), respectively D, E bulb, lateral view, different aspects F epigyne, ventral view. Abbreviations: dsa – distal suprategular apophysis, ep – embolus proper, mm – median membrane, mt – median tooth, pp – posterior projections of lateral walls, r – radix, rt – radical tooth.

Figure 2. 

Details of the male palp (A–E) and female epigyne (F) of Dactylopisthoides wrangelianus (Marusik & Koponen, 2009), specimens from Mamontovaya River, Wrangel Isl A–D right palp, retrolateral, dorsal, ventral and frontal view, respectively E embolic division, frontal view F epigyne, ventral view. Abbreviations: dsa – distal suprategular apophysis, ep – embolus proper, mm – median membrane, mt – median tooth, pp – posterior projections of lateral walls, r – radix, rt – radical tooth.

Figure 3. 

Frontal view of the embolic divisions of Dactylopisthoides hyperboreus Eskov, 1990 (A), D. wrangelianus (Marusik & Koponen, 2009) (B) and D. transbaicalicus (Marusik, Koponen & Danilov, 2001) [reproduced from Marusik and Koponen (2009)] (C). Abbreviations: dsa – distal suprategular apophysis, mm – median membrane, mt – median tooth, rt – radical tooth. Black, thick arrows show additional differences between species. Scale bar: 0.1 mm (С).

In the papers dealing with Dactylopisthoides (Eskov 1990) and Uusitaloia (Marusik et al. 2001; Marusik and Koponen 2009), the authors provided different tibial chaetotaxy even for different sexes. The reason for this appears to have been the small size of the spines, which could be easily overlooked (for further details, see Tanasevitch 2022).

The genus Dactylopisthoides currently consists of three very similar species: D. hyperboreus Eskov, 1990; D. transbaicalicus (Marusik, Koponen & Danilov, 2001) and D. wrangelianus (Marusik & Koponen, 2009).

From north-eastern Transbaikalia to Wrangel Island (Fig. 4). Its occurrence in Yakutia and Kamchatka is very likely.

Figure 4. 

Collecting localities of Dactylopisthoides species: D. hyperboreus (dot), D. transbaicalicus (diamond), D. wrangelianus (square), records of D. hyperboreus that could also refer to D. wrangelianus (triangle).

Holotype ♂ (ZMMU), Russia, Magadan Area, the upper reaches of Kolyma River, Sibit-Tyellakh, Pinus pumila thickets, 14.IX.1985, leg. Y.M. Marusik. Paratypes (all in ZMMU): 2 ♀♀, collected together with the holotype; 4 ♂♂, 8 ♀♀, same habitat, 12.VII. 1985, leg. Y.M. Marusik; 1 ♂, upper reaches of Kolyma River, c. 10 km upstream of Vetrenny Vil., Salix thicket on Carex swamp, 5.VIII.1984, leg. K.Y. Eskov; 1 ♂, headwater of Kolyma River, Kulu River, mouth of Stokovy Creek, Pinus pumila thicket on scree, 11.VIII.1986, leg. Y.M. Marusik; 1 ♂, Detrin River (the right tributary of Kolyma River), c. 56 km upstream of the mouth, 30.VIII.1986, leg. Y.M. Marusik.

This species has been known from a single taxonomic entry.

Dactylopisthoides hyperboreus seems particularly similar to D. wrangelianus. The male differs in the shorter dorsal tibial outgrowth (cf. Figs 1C and 2B) and a triangular radical tooth, vs stylet-shaped (cf. Figs 1E, 2E and Fig. 2A, B); the female differs in the wider fovea of the epigyne (cf. Fig. 1F and Fig. 2F). From D. transbaicalicus, it can be easily distinguished by the wider and shorter dorsal tibial outgrowth (cf. Fig. 1C and figs 40, 41, 43, 44 in Marusik et al. [2001]), as well as by the well-developed radical tooth of the embolic division (cf. Fig. 1E and Fig. 3C).

See Eskov (1990).

This species was described from several localities in the upper reaches of Kolyma River and Wrangel Island (Eskov 1990). Later, it was reported from Chukotka Peninsula (Marusik 1993), Ola Plateau in the south part of Magadan Area (Marusik 2005). The records of D. hyperboreus from Chukotka Peninsula (Marusik 1993) are likely to be erroneous and may refer to D. wrangelianus.

Holotype ♂ (ZMUT), Russia, Buryatia, Barguzin Mt. Range, Olso River, 54°52'N, 110°55'E, 1650 m, 04.VII.1996, leg. M. Uusitalo.

No SEM figures are provided for this species, as it remains known from the holotype male only.

From D. hyperboreus and D. wrangelianus, this species differs in having the longer and narrower dorsal tibial outgrowth (cf. figs 40, 41, 43, 44 in Marusik et al. [2001] and Figs 1C, 2B) and the reduced radical tooth of the embolic division (cf. Fig. 3C and Fig. 3A, B).

Only the type locality, Transbaikalia, Russia.

Holotype ♂ (ZMMU), Russia, Wrangel Isl., the upper reaches of Neizvestnaya River, 71°12.933'N, 179°19.353'W, 128 m, steppe-like mound #2, 06.VII–03.VIII.2006, leg. O.A. Khruleva. Paratypes: 1♂ (ZMMU), same locality, steppe-like, mound #3, 03.VII.–03.VIII.2006, leg. O.A. Khruleva; 2 ♂ (ZMMU, paratypes of D. hyperboreus) Wrangel Isl., lower reaches of Gusinaya River, gravel hilltop, 2.VII. 1984, leg. O.A. Khruleva; 1♂, 1♀ (ZMMU), middle reaches of Mamontovaya River, 22.VII–5.VIII.2015, leg. O.A. Khruleva.

Since a single female of this species was used to obtain SEM photographs, its technical description was impossible to produce.

Dactylopisthoides wrangelianus is most similar to D. hyperboreus (see above for diagnostic characters). From D. transbaicalicus, it differs in having a wider and shorter dorsal tibial outgrowth (cf. Fig. 2B and figs 40, 41, 43, 44 in Marusik et al. [2001]) and a well-developed radical tooth of the embolic division (cf. Fig. 3B, C).

See Marusik and Koponen (2009).

To date, this species is known from Wrangel Island only (Khruleva et al. 2022). Yet, the records of D. hyperboreus from Chukotka Peninsula (Marusik 1993) are likely to also refer to D. wrangelianus. There are also unpublished data (YM, personal data) about its occurrence in Chaun Bay in Chukotka. Unfortunately, the sample studied, represented by females, was lost.