Two new species of Hypodontolaiminae (Nematoda, Chromadorida, Chromadoridae) from the Yellow Sea with a phylogenetic analysis in the subfamily.

Two new species of Hypodontolaiminae, Dichromadoramedia sp. nov. and Neochromadoraparabilineata sp. nov. , were isolated and described from the Yellow Sea, China. Dichromadoramedia sp. nov. is characterized by four long cephalic setae, the amphidial fovea transverse oval in the male and slit-shaped in the female, the pharynx with a single posterior bulb, spicules curved and distally bifurcated, gubernaculum jointed, four (1+3) precloacal supplements papilliform, and the tail conical elongated with a short spinneret. Neochromadoraparabilineata sp. nov. is characterized by the buccal cavity with one large hollow dorsal tooth and two small subventral teeth, the pharynx with an obvious posterior bulb, spicules L-shaped and widened medially, gubernaculum boat-shaped, seven cup-shaped and equidistant precloacal supplements, and a long and gradually tapering tail. The phylogenetic analysis of maximum likelihood and Bayesian inference based on rDNA sequences confirmed the taxonomic positions of Neochromadoraparabilineata sp. nov. and Dichromadoramedia sp. nov. within Hypodontolaiminae. Tree topology in Hypodontolaiminae shows the genera Neochromadora , Dichromadora , Ptycholaimellus , and Spilophorella as polyphyletic groups, and the genus Chromadorita as a paraphyletic group.