Siskiyu Hedin, Ramírez & Monjaraz-Ruedas, 2025, gen. nov.

GenusSiskiyugen. nov. Figs 1, 6, 7 Etymology. A modification of siskiyou, from the Klamath-Siskiyou Mountains that encompass much of the known distribution of this genus. The etymology of siskiyou, possibly indigenous, remains uncertain. Grammatical gender treated as feminine. Diagnosis. With a conspicuous fracture line near the base of patellae I – IV, like close relatives Calymmaria and Willisus (Roth 1981: fig. 1; Heiss and Draney 2004: fig. 3). The male palp of Siskiyu gen. nov. is diagnosed from Calymmaria in possessing a dorsal tegular process, a thinner embolus with the distal tip projecting ventrally, associated with a trilobed conductor (Fig. 6 A, B). Calymmaria palps lack a tegular process, have generally thicker (or sometimes forked) emboli, with conductors that lack dorsal processes (Heiss and Draney 2004: figs 6, 7). Siskiyu gen. nov. male palps are most like those of Willisus but differ in the condition of the dorsal tegular process (more robust and toothed in Willisus), shape of the embolus (sinuate in Willisus), and shapes of both the conductor and RTA lobes (Roth 1981: figs 3–5). Siskiyu gen. nov. female genitalia differ from Calymmaria in possessing subequal, bilobed spherical spermathecae (Fig. 7 D, E), in contrast to the simple paired spherical spermathecae of most Calymmaria (Heiss and Draney 2004: figs 4, 5), and different from the distinctive C. alleni epigynum; Heiss and Draney 2004: figs 8, 9). Siskiyu gen. nov. female genitalia are distinguished from those of Willisus which include short copulatory ducts and oblique kidney-bean shaped spermathecae (Roth 1981: figs 6, 7). Description. Adults 2–3 mm in length. Dorsal carapace mostly bare and lacking pigmentation, longitudinal fovea ~ 2 × length of PME diameter. Eight eyes, anterior eye row slightly recurved, posterior eye row slightly procurved. AMEs smallest, ~ ¼ diameter of ALEs, separated by diameter. Lateral eyes approximately contiguous, approximately equal in size; PMEs ½ diameter of PLEs, slightly closer to PLEs. Clypeus as high as ALEs. Chelicerae straight, longer than width of cephalic region, lateral boss present; anterior margin with three teeth, posterior margin with five or six teeth. Labium nearly square, narrowing slightly anteriorly. Endites slightly convergent, ~ 2 × as long as wide, with serrula. Sternum approximately heart-shaped but with truncated anterior edge, narrowed posteriorly, ending at posterior edge of hind coxae; sparsely covered with fine hairs. Trochanters without notches. Legs with fine hairs, mostly unmarked. Leg formula 1, 4, 2, 3. Patella-tibia I 1.6–2 × longer than carapace. Femurs lacking macrosetae; patellar, tibial, and metatarsal macrosetae restricted to posterior legs. Leg patellae with conspicuous cleavage plane basally at ⅕ of patella length (Fig. 7 C). Tarsi and metatarsi with dorsal rows of 3–6 long trichobothria. Paired tarsal claws with ten teeth, median claw very small, semicircular hairs between claws not obvious. Abdomen with scattered simple hairs, more ventrally than dorsally. Colulus inconspicuous, with six setae. Anterior spinnerets are stout, conical, separated by basal width, distal segment hemispherical. Posterior spinnerets longer than anterior with wedge-shaped distal segments ~ 1.3 × longer than length of basal segment, pointed medially. Median spinnerets lying directly posterior and approximately equal in height to anterior spinnerets, closely adjacent. Female palp with tibial and tarsal macrosetae, clothed with fine hairs. Female genitalia with paired lateral openings, elongate copulatory ducts, bilobed spermathecae. Male palp with distal patellar apophysis; tibia with basal and distal processes. Bulb with small tegular process, slender embolus protected by beak-like ventral process of triangular conductor.