Trefusioidea Gerlach, 1966
Xennellidae De Coninck, 1965 (also as Xenellidae, De Coninck, 1965)
Free-living marine nematodes.
As of 2020, the family Xennellidae comprises two genera, Xennella Cobb, 1920 and Porocoma Cobb, 1920.
Nematodes have a cephalic capsule and an annulated cuticle with longitudinal ridges ; but similar to most Trefusiina in having outer labial and cephalic setae in separate circles and pocket-shaped amphideal fovea, as well as lacking metanemes (Lorenzen 1981)..
Cuticle annulated except in X. cephalata Cobb, 1920 where it is apparently smooth; longitudinal ridges on cuticle usually present.
Amphideal fovea pocket-shaped, horseshoe-shaped or circular.
Anterior sensilla arranged in a 6 + 6 + 4 pattern; long, setose outer labial and cephalic sensilla of similar length.
Tapering cephalic capsule present (Xennella) or absent (Porocoma); when present, cephalic capsule offset from rest of body by constriction, cuticular discontinuity and/or thickened cuticle.
Buccal cavity minute, tubular, without teeth.
Female reproductive system monodelphic (Xennella) or didelphic (Porocoma).
Male reproductive system monorchic (at least in Xennella suecica Allgén, 1935); spicules short, arcuate; gubernaculum present or absent, precloacal supplements present or absent.
Type genus Xennella Cobb, 1920..
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Andrassy, I. 2009. Free-living Nematodes of Hungary (Nematoda Errantia) Vol. 111. Humgarian Natural History Museum, Budapest. 508p.
Golden, A.M. and D.G. Murphy, 1967. Encholaimoidea (Nematoda: Dorylaimida), a new superfamily representing dorylaimid specimens with cephalic setae. Proc. Helmith Soc Washington. 34:94-98
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