New observations on Thornedia opisthodelphis (Jairajpuri, 1968) Siddiqi, 1982 (Dorylaimida, Leptonchidae) from Vietnam, with discussion on the identity of the genus

Thornedia opisthodelphis from a natural forest in northern Vietnam is described and illustrated. It is characterized by its body 0.50-0.57 mm long, lip region almost continuous and 5 μ m broad, odontostyle attenuate and 21 μ m long or 4.2 times the lip region width, odontophore linear, neck 148-155 μ m long, pharyngeal expansion 38-45 μ m long or 25-29% of total neck length, female genital system mono-opisthodelphic, prevulval sac totally absent, pars refringens vaginae also absent, V = 45-51, tail cylindrical (18-24 μ m, c = 23.5-31.7, c = 1.5-2.2), and male unknown. The identity of Thornedia is discussed in depth, including a historical outline, morphological characterization and its taxonomy. Because of the tylencholaimid cuticle and short pharyngeal expansion, it is transferred from Nordiidae to Leptonchidae. An emended diagnosis as well as a compendium of their species are also provided.