Two new species of genus Labronema Thorne, 1939 (Nematoda, Dorylaimidae) from natural parks of Vietnam with an identification key to the species with a medium-sized odontostyle.

Labronema Thorne, 1939 is a large and diverse dorylaimid genus with complicated taxonomy. Two new species, Labronemaporosum sp. nov. and Labronemabidoupense sp. nov. from natural habitats in Vietnam were characterised both morphologically and molecularly (18S rDNA and 28 rDNA), and line drawings and microphotographs are provided. Phylogenetic analyses showed that the new species clustered together with Labronemaferox Thorne, 1939, the type species of the genus. The two new taxa belong to a group of Labronema species with medium body (L = 1.5-2.5 mm) and odontostyle (31-39 μm) length, and a lip region offset by a constriction. Based on morphological and molecular evidence, this study shows that the populations from Vietnam previously identified as L.glandosum Rahman, Jairajpuri, Ahmad & Ahmad, 1986 in fact represent L.porosum sp. nov. Evolutionary relationships of Labronema species are discussed. A key to the species of Labronema with a medium-sized odontostyle (31-39 μm) is provided as well as a list of the species of the genus considered valid.