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A new cosmocercid nematode species, Cosmocercoides tonkinensis n. sp., is described from the scale-bellied tree lizard (Acanthosaura lepidogaster) in the northern and central parts of Vietnam. The new species is characterized by medium-sized male worms (4.2-5.1 mm in length and 0.34-0.37 mm in width) relative to known members of the genus, with lateral alae, two sharply pointed spicules of equal length (0.22-0.26 mm in length), a gubernaculum (0.113-0.122 mm in length), 16 or 17 pairs of caudal rosettes, and the presence of somatic papillae. Female worms are slightly larger than male worms (5.3-5.5 mm in length and 0.32-0.42 mm in width), with the vulva situated at 3/5 from the anterior end, and elliptical embryonated eggs, 0.064- 0.084 mm long by 0.040-0.048 mm wide. From 19 recorded species of the genus, the morphology of C. tonkinensis n. sp. is closest to C. multipapillata, C. bufonis, and C. pulcher reported from toads and frogs in East Asia. The present new species is differentiated from them by the number of caudal rosettes, tail length relative to body length, presence of somatic papillae and lateral alae, and embryonated eggs. Furthermore, after C. variabilis in North America and C. sauria in Brazil, this new species is only the third species to be recorded from a reptilian host. The 18S ribosomal RNA gene (rDNA) of the new species is almost identical to that of C. dukae infecting land snails and slugs in North America. Between the present new species and C. pulcher from a toad (Bufo japonicus) in Japan, remarkably fewer nucleotide changes were noticed in the 18S to 28S rDNA including the internal transcribed spacer regions. The molecular phylogenetic position of the genus Cosmocercoides is briefly discussed.

A new nematode genus and species associated with terrestrial gastropods from Vietnam is described and illustrated. Partial SSU and ITS rDNA sequences were obtained and subjected to phylogenetic analysis. Both morphologically and molecularly, Neoalloionema tricaudatum gen. n., sp. n. is closest to Alloionema appendiculatum, another gastropod associate. It is differentiated from A. appendiculatum by the presence of an outstretched vs reflexed testis and the absence of denticles in the stoma, by the parasitic juveniles inhabiting the pallial cavity vs the foot of the host and having six vs two lips and large sucker-like phasmids vs pore-like. The most peculiar feature of N. tricaudatum gen. n., sp. n. is the presence of paired, solid appendages located at the mid-tail region of juveniles from the pallial cavity of the host. The nature of the association between N. tricaudatum gen. n., sp. n. and its gastropod host is discussed.

Two species of nematodes, Angiostoma coloaense n. sp. and Aulacnema monodelphis n. g., n. sp. (Angiostomatidae: Rhabditida) are described from terrestrial molluscs of Vietnam. Both species are characterised by a long bowl-shaped buccal cavity and typically angiostomatid male bursal alae, spicules and gubernaculum. The new genus, Aulacnema n. g., is erected for the first reported monodelphic angiostomatid. Angiostoma coloaense n. sp. can be distinguished from other species of Angiostoma Dujardin, 1845 by having a buccal cavity length greater than its width and the absence of tail spikes on both males and females.

A new thelastomatid species, Aoruroides cochinchinensis sp. n., is described from the hindgut of Vietnamese Panesthiinae cockroaches collected in Bi Doup-Nui Ba National Park. It is the first report of nematodes of the genus Aoruroides Travassos & Kloss, 1958 from mainland Asia. Aoruroides cochinchinensis sp. n. males are characterized by thorn-like cuticular projections on the head end, maximal value of de Man index a (19.5) within the genus, and the nerve ring situated on the border of corpus and isthmus. Earlier, only knob-like cervical cuticular projections were described for males of A. queenslandensis Jex, Cribb & Schneider, 2004.