Two new Species of (Nematoda: Diplogastridae) include the Gonochoristic Sister Species of .

The genus (Kreis, 1932) consists of more than 30 soil nematode species that are often found in association with scarab beetles. Three major radiations have resulted in the " species group" in America, the " species group" in Asia, and the " species group," which contains species from Europe and Asia. Phylogenetic analysis indicates that a group of three species, including the gonochorists and and the hermaphrodite , is basal to the above-mentioned radiations. Two novel species are described here: sp. n. from Taiwan and sp. n. from Japan by means of morphology, morphometrics and genome-wide transcriptome sequence analysis. Previous phylotranscriptomic analysis of the complete genus recognized sp. n. as the sister species of , and thus its importance for macro-evolutionary studies. Specifically, the gonochorist sp. n. and the hermaphrodite form a species pair that is the sister group to all other described species. sp. n. has two distinct mouth forms, supporting the notion that the mouth dimorphism is ancestral in the genus . The genus (Kreis, 1932) consists of more than 30 soil nematode species that are often found in association with scarab beetles. Three major radiations have resulted in the “ species group” in America, the “ species group” in Asia, and the “ species group,” which contains species from Europe and Asia. Phylogenetic analysis indicates that a group of three species, including the gonochorists and and the hermaphrodite , is basal to the above-mentioned radiations. Two novel species are described here: sp. n. from Taiwan and sp. n. from Japan by means of morphology, morphometrics and genome-wide transcriptome sequence analysis. Previous phylotranscriptomic analysis of the complete genus recognized sp. n. as the sister species of , and thus its importance for macro-evolutionary studies. Specifically, the gonochorist sp. n. and the hermaphrodite form a species pair that is the sister group to all other described species. sp. n. has two distinct mouth forms, supporting the notion that the mouth dimorphism is ancestral in the genus .