Gammanema Cobb 1920

Genus Gammanema Cobb, 1920 = Trogolaimus Cobb, 1920 Type species Gammanema ferox Cobb, 1920. Diagnosis (from Tchesunov et al. 2020) Cuticle with homogenous annulations, without longitudinal ridges or lateral differentiation. Six inner and six outer labial sensilla, either setose or papillose; four cephalic setae, often slender and longer; outer labial and cephalic sensilla often combined in common circle of 10, with dorso- and ventrosublateral sensilla arranged in four pairs with cephalic sensilla. Amphidial fovea spiral or loop-shaped, usually noticeably larger in males than in females. Somatic setae in irregular longitudinal rows; anterior cervical setae may be as long as cephalic setae. Mouth opening surrounded by partly fused lips shaping a circumoral membrane with fine longitudinal striation. Twelve projections, from small and inconspicuous to prominent and elaborate, at rim of mouth opening. Buccal cavity (pharyngostome) with two chambers, anterior cup-shaped and posterior cylindrical; walls of each chamber strengthened with three cuticularized rhabdions; rhabdions of anterior chamber terminate posteriorly in minute denticles. Pharynx cylindroids, evenly muscular and devoid of terminal bulb.Alimentary tract terminates by rectum and anus. Precloacal midventral supplementary organs sucker-like, cup-shaped, tubular, or absent. Tail short, conical, cuticle of its terminal cone levigated or smooth. Remarks The genus was revised by Tchesunov et al. (2020), who also provided a pictorial key to valid species. Prior to this study, 14 species were considered valid, while three (G. ferox Cobb, 1920, G. menzelii (Ditlevsen, 1918) Gerlach, 1964 and G. rapax (Ssaweljev, 1912) Gerlach 1964) are considered species inquirendae (Tchesunov et al. 2020). Gammanema rapax was considered as dubious by Murphy (1965) because the original description lacks illustrations and type specimens are evidently lacking. This decision was ignored or overlooked in some subsequent taxonomic publications (e.g., Platt & Warwick 1988; Okhlopkov 2002; Ahmed et al. 2020) but was accepted in the recent review of Tchesunov et al. (2020).