Epeus taybac Vu & Pham sp. nov. Materials Type status: Holotype. Occurrence: catalogNumber: TBU-ARA-SAL-003-1; individualCount: 1; sex: 1 male; lifeStage: adult; occurrenceID: EE56D8CD-D43D-5C2B-AAFB-4E5F20090640; Taxon: scientificName: Epeus taybac sp. nov.; order: Araneae; family: Salticidae; genus: Epeus; Location: country: Vietnam; countryCode: VN; stateProvince: Son La; locality: Muong La Commune, Pieng Village; verbatimElevation: 680 m; verbatimLatitude: 21°34′57″N; verbatimLongitude: 104°04′58″E; verbatimCoordinateSystem: WGS 84; Event: eventDate: 22 May 2024; eventRemarks: collected by Duc-Toan Vu Type status: Paratype. Occurrence: catalogNumber: TBU-ARA-SAL-003-2; individualCount: 1; sex: female; lifeStage: adult; occurrenceID: 068C9472-D849-5CDA-A0AD-6111C93FF431; Taxon: scientificName: Epeus taybac sp. nov.; order: Araneae; family: Salticidae; genus: Epeus; Location: country: Vietnam; countryCode: VN; stateProvince: Son La; locality: Muong La Commune, Pieng Village; verbatimElevation: 680 m; verbatimLatitude: 21°34′57″N; verbatimLongitude: 104°04′58″E; verbatimCoordinateSystem: WGS 84; Event: eventDate: 22 May 2024; eventRemarks: collected by Duc-Toan Vu Type status: Other material. Occurrence: catalogNumber: TBU-ARA-SAL-003-3; individualCount: 1; sex: 1 male; lifeStage: adult; occurrenceID: 6B109DDB-74B5-5ED6-B4F2-CEE7CE57FC12; Taxon: scientificName: Epeus taybac sp. nov.; order: Araneae; family: Salticidae; genus: Epeus; Location: country: Vietnam; countryCode: VN; stateProvince: Son La; locality: Chieng Coi Ward, Na Phum Village; verbatimElevation: 875 m; verbatimLatitude: 21°18′23″N; verbatimLongitude: 103°51′03″; verbatimCoordinateSystem: WGS 84; Event: eventDate: 11 March 2025; eventRemarks: collected by Duc-Toan Vu Description Male. Total length 7.74. Carapace 2.84 long, 2.33 wide. Abdomen 3.62 long, 1.48 wide. Eye sizes and interdistances: AME 0.72, ALE 0.32, PME 0.09, PLE 0.33, ALE-PME 0.34, ALE-PLE 0.81. Legs measurements: I 9.76 (2.81, 1.34, 2.79, 2.01, 0.81), II 7.72 (2.28, 1.12, 2.04, 1.58, 0.70), III 9.04 (2.95, 1.10, 1.91, 2.18, 0.90), IV 7.95 (2.35, 1.00, 1.77, 1.85, 0.98). The carapace is high and elevated, with a posterior slope, exhibiting a colouration ranging from yellow-brown to dark brown (Fig. 3 A). A crest of erect hairs is present along the carapace (Fig. 3 C). The sternum is oval, slightly wider posteriorly, brown with a lighter margin. The clypeus is dark brown, covered with brown and white hairs and bristles. Chelicerae, endites and labium are dark brown, chelicerae with two promarginal teeth and one retromarginal tooth (Fig. 3 D). Legs are long and slender; legs I, II and III are dark brown and covered with setae, except for the metatarsus and tarsus, which are yellowish-brown, while leg IV is entirely yellowish-brown. The abdomen is slender and cylindrical, with a dark brown dorsum featuring two light-coloured lateral stripes and a dark brown ventral surface. The male palpal organ (Fig. 4) exhibits a filiform embolus that is long and arises at the 6: 00 o’clock position, coiling approximately 180 °. A well-developed, tongue-like flap is present at a 90 ° angle on the tegular bump. The proximal tegular apophysis is slender, sharp and curved (Fig. 4 A, B and E). In dorsal view, the cymbium is nearly triangular, with the retrolateral edge concave, tapering anteriorly and covered with long white setae. The cymbial apophysis is elongate and slender, with its distal end slightly curved. The retrolateral tibial apophysis is stout, slightly blunt and directed anterodorsally (Fig. 4 C and F). Female. Total length 5.50. Carapace 2.62 long, 1.48 wide. Abdomen 2.87 long, 1.32 wide. Eye sizes and interdistances: AME 0.52, ALE 0.16, PME 0.06, PLE 0.21; ALE – PME 0.25, ALE – PLE 0.62. Legs measurements: I 5.58 (1.70, 0.81, 1.57, 1.01, 0.49), II 5.47 (1.69, 0.78, 1.31, 1.08, 0.61), III 6.13 (1.93, 0.68, 1.34, 1.53, 0.65), IV 5.91 (1.78, 0.52, 1.44, 1.46, 0.71). The carapace is similar in shape to that of the male, exhibiting a pale yellow to yellow-orange colouration. The anterior half of the carapace is covered with colourless and white setae (Fig. 5 A). The area surrounding the anterior median eyes is yellow, while the regions around the other eyes are dark brown to black-brown, interspersed with white setae. The clypeus is densely covered with white setae (Fig. 5 C). Chelicerae are yellow, whereas the endites, labium and sternum are pale yellow. Legs and palps are predominantly pale yellow, with the exception of the metatarsi and tarsi, which exhibit a yellow-orange hue. The abdomen is slender and dorsally pale yellow, adorned with clusters of white spots arranged along the lateral margins. The ventral surface is pale yellow. The epigynal plate is longer than wide (Fig. 6 A), featuring cup-shaped copulatory openings. The internal copulatory ducts are long and expansive, forming numerous loops. Diagnosis The male genitalia of Epeus taybac sp. nov. resemble those of E. albus, E. daiqini and E. glorius. However, E. taybac sp. nov. can be distinguished by the following characters: the presence of a proximal tegular apophysis (PTA), which is long, curved and located posterior to the tegular bump (TB) on the patella side (Fig. 4 A, B and E); the cymbial apophysis (CA) is long and pointed when viewed ventrally, with the tip slightly curved outwards (Fig. 4 B), in contrast to the blunt tip observed in E. albus (Tam and Thuy 2025) and considerably longer than the CA of E. daiqini (Patoleta et al. 2020), lacking the small serrated apophyses present in E. glorius (Zabka 1985). The retrolateral tibial apophysis (RTA) is approximately one-third the length of the tibia, stout, slightly blunt and directed anterodorsally (Fig. 4 C and F). Females of the new species are morphologically similar to E. albus, sharing wide copulatory openings and a comparable copulatory duct arrangement when viewed ventrally (Fig. 6 A). However, E. taybac sp. nov. can be differentiated by the more compact arrangement of the copulatory ducts (CD), which form an oval shape in dorsal view (Fig. 6). Etymology The species is named after its type locality: taybac refers to “ Tây B ắc, ” the Vietnamese name for the north-western region of Vietnam.

Published as part of Vu, Duc-Toan, Duong, Van-Tang & Pham, Dinh-Sac, 2025, First records of Epeus bicuspidatus and description of a new species of Epeus (Araneae, Salticidae) from Vietnam, pp. e 172899 in Biodiversity Data Journal 13 on page e172899, DOI: 10.3897/BDJ.13.e172899