Three new species, one new genus and subfamily of Dorylaimida (de Man, 1876) Pearse, 1942, and revisions on the families Tylencholaimellidae Jairajpuri, 1964 and Mydonomidae Thorne, 1964 (Nematoda: Dorylaimida).

Three new species of the order Dorylaimida (de Man, 1876) Pearse, 1942 were identified and described. gen. nov. sp. nov. from Hainan is proposed as a new member of the family Tylencholaimellidae Jairajpuri, 1964. gen. nov. is close to Thorne, 1964 and Jairajpuri & Ahmad, 1992 but can be differentiated mainly by having basal part of odontophore rod-like and without knobs, and basal part of pharynx expanded gradually. sp. nov. from Guangdong and sp. nov. from the Ningxia Hui Autonomous Region are also described herein. Phylogenetic analyses based on the 18S rDNA and the D2-D3 region of the 28S rDNA support that the three new species are valid. The classifications of the families Tylencholaimellidae and Mydonomidae Thorne, 1964 are revised mainly based on the analysis of the morphology of odontostyle and odontophore. After these revisions, Paratylencholaiminae subfam. nov. including gen. nov. and is proposed. and of Tylencholaimellidae are transferred into Mydonomidae, and the subfamily Athernematinae of Tylencholaimellidae is dismissed. The main characteristics of the family Mydonomidae and Tylencholaimellidae are revised. Keys to the genera of Mydomonidae and Tylencholaimellidae are included.