Updated taxonomy and new insights into the evolutionary relationships of the genus Sporonchulus Cobb, 1917 (Nematoda, Mononchida) after the study of two Vietnamese species

Two known species of the genus Sporonchulus, namely S. ibitiensis and S. vagabundus, collected from natural areas of Vietnam, are characterized, including descriptions and illustrations of both species, as well as SEM observations and molecular (18S-, 28S rDNA) analyses of S. ibitiensis. The identity of the two species is discussed, with detailed comparison with previously known populations. The taxonomy of the genus is updated, presenting a diagnosis, list of species, key to their identification, and a compendium of their main morphometrics. An integrative analysis, combining morphological data with a cladistic approach and the first molecular study for a representative of Sporonchulus, better supports a narrow relationship of this genus with Mononchidae than with Mylonchulidae members, however further research should be conducted to elucidate its phylogeny.