Description of two new species, Sphaerolaimus obesus sp. nov. and Pseudosteineria articulata sp. nov. (Nematoda, Sphaerolaimoidea) from the Yellow Sea, China and phylogenetic analysis within superfamily Sphaerolaimoidea with combined ribosome DNA sequences

Two new species of superfamily Sphaerolaimoidea: Sphaerolaimus obesus sp. nov. and Pseudosteineria articulata sp. nov. are described from the Yellow Sea. Sphaerolaimus obesus sp. nov. is characterized by body stout, cuticle finely striated with lateral alae, outer labial sensilla and cephalic sensilla papilliform, eight bunches of subcephalic setae different in length, amphidial fovea situated at the level of buccal cavity, spicules arcuated with proximal end cephalated, gubernaculum with dorsal-caudal directed apophysis different in shape, seven precloacal papilliform supplements, tail conico-cylindrical with three terminal setae. Pseudosteineria articulata sp. nov. is characterized by cuticle distinctly annulated with lateral alae, six outer labial setae jointed, eight rows of subcephalic setae present, two rows of long somatic setae scattered along lateral alae, amphidial fovea posterior to subcephalic setae, spicules curved and jointed with proximal end with large manubrium, gubernaculum slightly funnel-shaped, tail conico-cylindrical. Phylogenetic analysis based on combined rDNA sequences place Sphaerolaimus obesus sp. nov. and Pseudosteineria articulata sp. nov. within family Sphaerolaimidae and Xyalidae, respectively. Relationships analysis within the superfamily Sphaerolaimoidea shows Sphaerolaimidae as a sister clade to Xyalidae and genera of Xyalidae as paraphyletic clades.