Pseudeuchaeta Sars, 1905
Taxonomic description:
Female. Total length 4.8-10.5 mm. Cephalothorax 2.8-4.0 longer than abdomen. Crest absent. Rostrum strongly reduced, like blunt rounded plate. Cephalon and Th1, as well as Th4-Th5 partly or completely fused, line of fusion usually well visible. Posterior Th5 corners symmetrical, rounded, or with slight triangular tops, or prolonged into short points directed straight backwards, or to back side of specimen (lateral view). Posterior borders of abdominal segments with minute thin spinules. Genital segment symmetrical, nearly as long as 2 following abdominal segments. Distal parts of spermatheca small, rising duct rather narrow. A1 24-segmented, usually shorter than cephalothorax, but sometimes of the same length, or slightly longer. Re and Ri A2 of about the same length, coxopodite with 1 seta, basipodite with 1-2 setae (sometimes absent); Re1 and Re2 A2 with 2 setae, Re3-Re6 with 1 long, robust seta each, Re7 with 3 terminal setae. Ri1 A2 lacking setae (Sars (1924) figured 1 seta), Ri2 A2 with 12-13 (6 on external and 6-7 on internal lobes). Md palp base with 1 seta, Ri1 Md with 1 seta, Ri2 Md with 4-8 setae, Ri less than half as long as Re. Mx1 gnathobase small, with 11-13 setae, 7-8 of them usually more sclerotized; second and third internal Mx1 lobes with 2-4 and 3-4 setae respectively, protopodite near Ri base with 5 setae, Ri with 14-16 setae, Re with 11 setae, external lobe with 8-9 setae. Mx2 fifth endite longer than others, all endites with bushes of spinules; Ri with 6 robust, strongly sclerotized setae. Mxp large with robust setae on Ri segments, setae with crescent-like sensitive bodies. Proximal part of Mxp protopodite with 1 seta, then groups of 2, 3 and 3 setae, in distal part of protopodite in addition to group of 3 setae there is 1 digital appendage, it may be shorter or longer than setae of distal group. P1 with 3-segmented Re, Re1 P1 lacking spine (in P. spinata spine present), Re2-Re3 P1 with spines, Ri with well developed lobe, with thin long hairs (not with spinules as in the majority of Aetideidae) along external margin apically. Ri P2 2-segmented, all other swimming leg rami 3-segmented.
Male. Total length 5.9-8.8 mm. Cephalothorax 3.1-3.8 times longer than abdomen. Rostrum rudimentary cone-like. Posterior Th5 corners rounded (lateral view) and slightly elongated (dorsal view). Abd2 is the longest and widest abdominal segment. Abd2-4 covered with minute spinules along posterior border. A1 nearly as long as cephalothorax, or reaching Abd3. Ri A2 longer than Re A2. A2 coxopodite and basipodite with 1 seta each; Re1 A2 lacking seta, Re2 A2 with small projection, or setae on proximal edge (or they are absent), in other features limb setation as in female. Ri2 Md with 8-9 setae, in other characters limb as in female, gnathobase strongly reduced. Mx1 and Mx2 setation reduced. Near the base of distal group of setae on Mxp protopodite sensitive appendage may be present. P1-P4 as in females. P5 biramous with one-segmented Ri and 3-segmented left Re, right Re 3-segmented. Left Re3 P5 with spinules along internal border.
Type species: Pseudeuchaeta brevicauda Sars, 1905, by monotypy.
The genus Pseudeuchaeta includes 6 species:
Pseudeuchaeta arctica Markhaseva, 1986
Pseudeuchaeta brevicauda Sars, 1905
Pseudeuchaeta flexuosa Bradford, 1969 (male unknown)
Pseudeuchaeta magna Bradford, 1969 (male unknown)
Pseudeuchaeta major Wolfenden, 1911 (male unknown)
Pseudeuchaeta spinata Markhaseva, 1986 (male unknown)