Fluctus Jin & Zhang 2020, gen. nov.
Creators: name: Jin, Chi
name: Zhang, Feng
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Arachnida
Araneae
Corinnidae
Fluctus

description: Fluctus gen. nov. (dzdzHOE)
Type species: Fluctus bannaensis sp. nov.
Etymology. The generic name is a Latin word “ fluctus ”, meaning “wave”, referring to the particular wave-shaped pattern on abdomen dorsally. The gender is masculine.
Diagnosis. This new genus differs from all other Castianeirinae genera in the combination of the particular wavy pattern on abdomen dorsally of males and females (Figs 1A, 1B, 5E), a paracymbial spine on the cymbium retrobasally of the male palp (Figs 3C, 6C), and the large, smooth, unfolded, spherical spermathecae of the female vulva (Figs 3F, 6F).
Among those Castianeirinae genera distributed in southern Asian, Fluctus gen. nov. most closely resembles the genus Corinnomma in both possessing a paracymbial spine on the male palpal cymbium, but can be distinguished from it by: 1) the anterior edge of abdomen overhanging the posterior of the carapace (Fig. 1 C–D), rather than the gradually sloping anterior abdomen in Corinnomma (Deeleman-Reinhold 2001: fig. 465); 2) the AER in frontal view and PER in dorsal view are obviously procurved (Fig. 2C, D), whereas they are both almost straight in Corinnomma (Raven 2015: fig. 12d); 3) transverse ventral groove present in the male palpal tibia (Figs 3C, 6C), whereas it is absent in Corinnomma (Raven 2015: fig. 13b); 4) secondary spermathecae spherical (Figs 3F, 6F), whereas they are folded in Corinnomma (Deeleman-Reinhold 2001: fig. 468).
Description. Medium sized (7.29–10.23 mm), dark spiders. Carapace dark brown to black, pear-shaped, truncated at posterior margin; arched in lateral view, gently sloping upward from eye area to fovea, highest at fovea, steeply sloping downward posteriorly (Fig. 1C); white feathery hairs form broad longitudinal stripe medially from clypeus to posterior margin of carapace, with narrow arc-shaped stripes at fringe (but are often not obvious in ethanol), longitudinal stripe anteriorly as wide as cephalic region (Fig. 1A, B, D); widest between coxae II and III, gradually narrowing backwards, straight or slightly concave at posterior margin before pedicel; radial and cervical grooves indistinct; fovea longitudinal, located at centre of thoracic region. Ocular area narrow, about 0.6 times CRW; AER procurved in frontal view, PER procurved in dorsal view; AME largest; ALE smallest, oval; with six long curved setae behind PER (Fig. 2G). Clypeus height about 1.5–2 times AME diameter, with three long curved setae arranged in a triangle (Fig. 2H), present in both males and females. Chilum present, single, triangular, weakly sclerotized (Figs 2D, 5H). Chelicerae same color as carapace; fang mound light color, with long curved setae; promargin with three and retromargin with two teeth. Endites, labium and sternum with same color; endites longer than wide, with light-colored inner edges, short and almost triangular in males; labium wider than long, with light-colored apex (Fig. 2B); sternum shield-shaped, longer than wide, precoxal triangles and intercoxal sclerites present. Legs long, with stripes of white hair (Fig. 1A, B); all femora black, other segments dark brown; anterior tibiae with three and metatarsi with two pairs of ventral spines. Patellae I–IV with one proximal and one disto-dorsal trichobothria; tibiae I–II with one disto-dorsal trichobothria. Leg formula 4123. Abdomen long ovoid, dark brown to black; with overhanging edge anteriorly (Fig. 1C); dorsum with one longitudinal wave-shaped band medially formed by white or pale yellow feathery hairs and no other patches (Fig. 1A, B); dorsal scutum in male full length of abdomen, extending onto lateral faces (in F. bannaensis sp. nov.) or even fused to ventral sclerite (in F. tengchongensis sp. nov.) (Fig. 5A, B); dorsal scutum in female weak and small, usually one-third of abdomen length or shorter; epigastric sclerite developed in both sexes, forming tube-like collar wrapping pedicel in males and females (Fig. 5B); postepigastric and ventral sclerites present in males; inframamillary sclerite small and present in both sexes; pairs of lunate patches on lateral faces of abdomen (Fig. 2F); abdomen paler ventrally than dorsally.
Palpal tibia longer than wide, with deep transverse ventral groove (Fig. 3 A–C); RTA absent; prolateral tibial tubercle triangular. Cymbium with one distinct digitiform retrobasal paracymbial spine on low process (Figs 3C, 4C, 6C, 7C), without thick setae on tip. Tegulum pyriform, with thick double-looped sperm duct occupying most area of tegulum. Subtegulum visible on both sides in ventral view, partly membranous (Figs 3 A–B, 6A–B). Embolus short, helically twisted, coiled less than one turn, with a pointed tip (Figs 3D, 6D).
Epigynal region sclerotized, anteriorly with a pair of linear epigynal depression; median plate present, inconspicuous, anterior wide and posterior narrow (Figs 3E, 4D, 6E, 6D). Copulatory openings medially situated, small, with sclerotized crescentic ridges. Copulatory ducts narrow and short, diagonally forward to outer base of secondary spermathecae (Fig. 3F). Primary and secondary spermathecae large, spherical, without wrinkles (Figs 3F, 6F). A V-shaped or Y-shaped fixed sclerite present, connected to dorsal medially of primary spermathecae and posterior margin of epigyne (Figs 3F, 6F).
Composition. Two species: F. bannaensis sp. nov. and F. tengchongensis sp. nov..
Distribution. Known only from Yunnan Province of China (Fig. 8).
Natural history. Active in daytime, wandering on the ground on leaf litter.
description: Published as part of Jin, Chi & Zhang, Feng, 2020, Fluctus gen. nov., a new castianeirine genus from Yunnan, China (Araneae: Corinnidae), pp. 161-172 in Zootaxa 4821 (1) on pages 162-163, DOI: 10.11646/zootaxa.4821.1.9, http://zenodo.org/record/4398352