Redescription of , a Tadpole-Endoparasitic Nematode from Japan, with Resurrection of the Family Gyrinicolidae (Nematoda: Oxyurina).

The taxonomic account of the tadpole-parasitic nematode Yamaguti, 1938, which is the type species of the genus, was reassessed based on syntypes and newly-collected specimens from the type locality. Our redescription of addresses the erroneous original description of a spicule in this nematode, and emends the diagnosis of the species. Additionally, molecular phylogenetic trees based on nuclear 18S and 28S rDNA sequences revealed that forms a distinctive lineage within the suborder Oxyurina, and this tadpole-specialist is phylogenetically close to the lizard-parasitic nematodes that belong to the family Pharyngodonidae. The results of morphological examination with the aid of molecular phylogenetic trees highlight the systematic uniqueness of this tadpole-parasitic group within Oxyurina, and Gyrinicolidae is accordingly resurrected as a distinctive oxyurinan family, with redefinition of the family and the genus .