Diagnosis: Large-sized nematodes ( L = 2.5 - 6.0 mm). Cuticle
thickened especially towards tail, with fine striations, sometimes with
indications of criss-cross lines overlying transverse striations.
Lips fairly distinct, hexagonal in en face view, set off by deep
constriction, and wider than adjoining body. Tooth deltoid, smaller
or longer than lip width. Pharynx nygolaimoid, its walls well sclerotised
in region of tooth. Oesophagus with basal expanded part usually occupying
two-thirds its length. Basal expanded part consisting of three sections,
first and second of which are often separated by constriction, middle and
basal section enclosed in sheath. Hemizonid either opposite or slightly
anterior to nerve ring, appearing as two adjacent notches in sub-cuticle.
Cardiac disc present. Female reproductive system amphidelphic.
Vulva transverse. Spicules with lateral apical thickenings; lateral
guiding pieces and well-developed spaced ventromedian supplements present.
Gubernaculum absent. Tail short, conoid; similar in sexes.
Type species: Nygolaimellus abnormis Loos, 1949.
Specimens from Costa Rica
N. heynsi Ahmad and Jairajpuri, 1982
N. hopperi Heyns, 1968
N. macmacus Heyns, 1968
N. quintus Heyns, 1968
N. rectalus Heyns, 1968