Two new species of the genus Daptonema Cobb, 1920 (Nematoda: Xyalidae) found in an intertidal seagrass bed on the coast of the Andaman Sea, Thailand, with reference to the taxonomic status of the genus Trichotheristus Wieser, 1956.

Daptonema chonispiculum sp. n. and D. phuketense sp. n. are described from the Ban Pa Khlok seagrass bed, Phuket Province, Thailand. Daptonema chonispiculum sp. n. is characterized by spicules with funnel-shaped proximal ends, and D. phuketense sp. n. is unique in having the third caudal gland filled with fibrous contents. Each new species also differs from most related species in body length, de Man's indices, length of the cephalic setae and somatic/cervical setae, distance of the amphids from the anterior of the body, and length of the spicules. The new species most closely resemble D. hirsutum, D. platonovae, and D. robustum, with similar body lengths, long cervical setae located in the anterior pharyngeal region, small amphids, L-shaped spicules and a gubernaculum with a long dorso-caudal apophysis. Regarding the taxonomic status of Daptonema and Trichotheristus, we agree with the synonymization of Trichotheristus with Daptonema by Tchesunov (1990), based on taxonomic review of Trichotheristus and a comparison of the diagnostic features separating the genera. We propose a new combination, Daptonema galeatum comb. n., and a new name, Daptonema nearticulatum sp. n. for Trichotheristus articulatus Huang Zhang, 2006.