taxonID	type	description	language	source
03C0879CFFFEFFA706CE975933DAB27E.taxon	diagnosis	Diagnosis. Body length reaching ~ 5 mm [= “ small- ” to “ medium-sized ” Japanese Cybaeus, sensu Ihara (2004); Fig. 2 A]. The female of C. eremospelyngus sp. nov. is most similar to that of C. inagakii in the shapes of their spermathecae with SH, SS, and SB, all of which are bulbous, and their arrangement. However, the female of this new species can be clearly distinguished from the latter by the atrium, which is wider than long, whereas that of C. inagakii is longer than wide (see fig. 14 in Ono 2008). The male of C. eremospelyngus sp. nov. is distinguishable by the shape of its PA, which is directed anteriorly, while that of C. inagakii expands retrolaterally (see fig. 12 in Ono 2008). Furthermore, C. eremospelyngus sp. nov. is clearly distinguishable from C. inagakii by its possession of eight eyes (originally six reduced eyes in C. inagakii; fig. 8 in Ono 2008).	en	Matsushita, Eitaro, Ihara, Yoh, Nakano, Takafumi (2025): A New Species of the Genus Cybaeus (Araneae: Cybaeidae) from a Cave in Northeastern Central Honshu, Japan. Species Diversity 30 (1): 49-54, DOI: 10.12782/specdiv.30.49, URL: https://doi.org/10.12782/specdiv.30.49
03C0879CFFFEFFA706CE975933DAB27E.taxon	materials_examined	Material examined. Holotype: male, KUZ Z 5306, from Osawa-shonyudo Cave, Gosen, Niigata, Japan (cave entrance: 37.68254 ° N, 139.1011 ° E), collected by Yoh Ihara on 16 October 2023. Paratype: one female, KUZ Z 5307, same collection data as for holotype. Additional material: one subadult female, KUZ Z 5088, same locality data as for holotype, collected by Takafumi Nakano on 20 September 2023.	en	Matsushita, Eitaro, Ihara, Yoh, Nakano, Takafumi (2025): A New Species of the Genus Cybaeus (Araneae: Cybaeidae) from a Cave in Northeastern Central Honshu, Japan. Species Diversity 30 (1): 49-54, DOI: 10.12782/specdiv.30.49, URL: https://doi.org/10.12782/specdiv.30.49
03C0879CFFFEFFA706CE975933DAB27E.taxon	description	Description. Male (holotype, KUZ Z 5306: Figs 2 A, 3). Measurements (mm): CL 2.29, CW 1.57; head 0.93 wide; abdomen 2.50 long, 2.25 wide; ocular area 0.19 long, 0.53 wide; sternum 1.17 long, 1.05 wide; CW / CL 0.69, TibIL / CL 0.92. Leg formula IV> I> II> III; length of legs (femur + patella + tibia + metatarsus + tarsus): leg I 8.58 (2.17 + 0.75 + 2.10 + 2.03 + 1.53); leg II 8.23 (2.06 + 0.77 + 1.86 + 2.00 + 1.54); leg III 7.38 (1.93 + 0.72 + 1.53 + 1.92 + 1.28); leg IV 8.98 (2.24 + 0.74 + 2.12 + 2.34 + 1.54). Carapace (Fig. 2 A). Head narrow, ~ 0.59 × as wide as thoracic region; thoracic region almost as high as head. Eyes 8 in number; AER slightly recurved in frontal view; PER slightly recurved in dorsal view; AME smallest, <1 / 2 diameter of other eyes; ocular area ~ 2.8 × wider than long. Clypeus as long as median ocular area. Mouthpart. Chelicerae geniculate, promargin of fang furrow with 3 teeth (median one largest), retromargin with 4 teeth and 4 denticles, and basally with lateral condyle. Labium wider than long. Leg macrosetae (left legs). Leg I: tibia p 3, r 2, v 2 - 2 - 2 - 2; metatarsus p 3, r 1, v 2 - 2 - 3. Leg II: tibia p 4, r 2, v 2 - 2 - 1 - 2; metatarsus p 4, r 2, v 2 - 2 - 3. Abdomen (Fig. 2 A). Colulus two groups of 1 or 2 setae. Palp (Fig. 3). PA directed anteriorly, short digitiform in retrolateral view, retrolateral surface with 4 peg setae. Tibia as long as patella; RTA plate-like, occupying 1 / 2 of length of tibia. Cymbium ~ 2.6 × longer than wide, slightly expanded prolaterally. Genital bulb almost circular in ventral view. Conductor: distal part short; PCO conical and curved prolaterally. EM simple, originating and terminating, respectively, at ~ 10 o’clock and ~ 5 o’clock. Color (Fig. 2 A). Carapace: head pale brown, with whitish weak reticulate markings; thoracic region pale beige, with pale brown weak radiating bands. Chelicerae, maxillary lobe, and labium orangish brown. Sternum pale beige, dark- er towards margins. Legs pale beige, darker distally, without annulations. Abdomen: pale gray, dorsally without chevron-like markings. Female (paratype, KUZ Z 5307: Figs 2 B, C, 4, 5). Measurements (mm): CL 2.29, CW 1.47, head 0.88 wide; abdomen 2.71 long, 2.06 wide; ocular area 0.18 long, 0.54 wide; sternum 1.11 long, 1.04 wide; CW / CL 0.64, TibIL / CL 0.75. Leg formula IV> I> II> III; length of legs (femur + patella + tibia + metatarsus + tarsus): leg I 7.00 (1.89 + 0.73 + 1.72 + 1.56 + 1.10); leg II 6.68 (1.75 + 0.71 + 1.54 + 1.59 + 1.09); leg III 6.06 (1.64 + 0.64 + 1.28 + 1.52 + 0.98); leg IV 7.44 (1.99 + 0.64 + 1.75 + 1.89 + 1.17). Carapace (Fig. 2 B). Head narrow, ~ 0.60 × as wide as thoracic region; thoracic region almost as high as head. Eyes 8 in number; AER slightly recurved in frontal view; PER slightly recurved in dorsal view; AME smallest, <1 / 2 diameter of other eyes; ocular area ~ 3.1 × wider than long. Clypeus as long as median ocular area. Mouthparts. Chelicerae geniculate, promargin of fang furrow with 3 teeth (median one largest), basally with lateral condyle, and retromargin with 5 teeth and 4 denticles on left side, 4 teeth and 6 denticles on right side. Labium wider than long. Leg macrosetae (left leg). Leg I: tibia p 3, r 1, v 2 - 2 - 2 - 2; metatarsus p 5, r 2, v 2 - 2 - 1. Leg II: tibia p 4, r 1, v 2 - 2 - 1 - 2; metatarsus p 5, r 3, v 2 - 2 - 1. Abdomen (Fig. 2 C). Colulus two groups of 3 setae. Genitalia (Figs 4, 5). EPPM curved. Atrium located posteromedially on epigyne. CPs separated on anterior side of atrium; CD thick and short, running anteriorly and curved dorsally. SH developed, SH with PP located dorsally; SS bulbous, located retrolaterally to SH; SB bulbous, directed posteriorly; BG located on SS posteromedially around connection between SS and SB; FD running from SB, descending posteromedially, and then turned anterodorsally. Color (Fig. 2 B, C). Carapace: head pale brown, with whitish weak reticulate markings; thoracic region pale beige, with pale brown weak radiating bands. Chelicerae, maxillary lobe, and labium orangish brown. Sternum pale beige, darker towards margins. Legs pale beige, darker distally, without annulations. Abdomen: pale gray, with whitish reticulate markings, dorsally without chevron-like markings. Subadult (KUZ Z 5088). Measurements (mm): CL 2.22; abdomen 2.41 long. Mouthparts. Chelicerae geniculated, promargin of 3 teeth (median one largest), with basally lateral condyle, and retromargin 4 teeth and 4 denticles on left side, 5 teeth and 4 denticles on right side. Labium wider than long. Leg macrosetae (left leg). Leg I: tibia p 3, r 2, v 2 - 2 - 2 - 2; metatarsus p 4, r 1, v 2 - 2 - 2. Leg II: tibia p 4, r 0, v 2 - 1 - 2 - 2; metatarsus p 5, r 2, v 2 - 2 - 1. Abdomen. Colulus two groups of 2 or 3 setae. Color. Carapace: head pale brown, with whitish weak reticulate markings; thoracic region pale beige, with pale brown weak radiating bands. Chelicerae, maxillary lobe, and labium light orangish brown. Sternum pale beige, darker towards margins. Legs uniformly pale beige or slightly darker distally, without annulations. Abdomen: pale gray, dorsally without chevron-like markings.	en	Matsushita, Eitaro, Ihara, Yoh, Nakano, Takafumi (2025): A New Species of the Genus Cybaeus (Araneae: Cybaeidae) from a Cave in Northeastern Central Honshu, Japan. Species Diversity 30 (1): 49-54, DOI: 10.12782/specdiv.30.49, URL: https://doi.org/10.12782/specdiv.30.49
03C0879CFFFEFFA706CE975933DAB27E.taxon	distribution	Distribution. This species inhabits the subterranean environment in Osawa-shonyudo Cave, in Niigata Prefecture, Japan. Retreat. Cybaeus eremospelyngus sp. nov. constructs a Y-shaped retreat (Fig. 6); ‘ V-shaped’ retreats were not found in the cave.	en	Matsushita, Eitaro, Ihara, Yoh, Nakano, Takafumi (2025): A New Species of the Genus Cybaeus (Araneae: Cybaeidae) from a Cave in Northeastern Central Honshu, Japan. Species Diversity 30 (1): 49-54, DOI: 10.12782/specdiv.30.49, URL: https://doi.org/10.12782/specdiv.30.49
03C0879CFFFEFFA706CE975933DAB27E.taxon	etymology	Etymology. The specific name is a compound noun in the genitive case derived from the Ancient Greek “ eremos ” (solitary) and “ spelynx ” (cave). It refers to the type locality of this new species, which is isolated from large karst regions. DNA sequences. In total, two sequences were obtained from the subadult specimen (KUZ Z 5088), two sequences, COI (202 bp; INSD accession number, LC 833823) and 28 S (285 bp; LC 833824). Due to the insufficient preservation of the specimen, short fragments only could be determined.	en	Matsushita, Eitaro, Ihara, Yoh, Nakano, Takafumi (2025): A New Species of the Genus Cybaeus (Araneae: Cybaeidae) from a Cave in Northeastern Central Honshu, Japan. Species Diversity 30 (1): 49-54, DOI: 10.12782/specdiv.30.49, URL: https://doi.org/10.12782/specdiv.30.49
03C0879CFFFEFFA706CE975933DAB27E.taxon	discussion	Remarks. Cybaeus eremospelyngus sp. nov. has pale body coloration and relatively small eyes. Therefore, this species is considered to be somewhat adapted to hypogean environments. Female morphological characteristics of the	en	Matsushita, Eitaro, Ihara, Yoh, Nakano, Takafumi (2025): A New Species of the Genus Cybaeus (Araneae: Cybaeidae) from a Cave in Northeastern Central Honshu, Japan. Species Diversity 30 (1): 49-54, DOI: 10.12782/specdiv.30.49, URL: https://doi.org/10.12782/specdiv.30.49
