Ohbayashinema erbaevae n. sp. (Nematoda, Trichostrongylina, Heligmosomoidea) is described from Ochotona daurica (Rodentia, Ochotonidae) (natural host) from Buriatia and O. rufescens (experimental host). The new species is close to O. ochotonae Durette-Desset, 1974, parasitic in Ochotona macrotis from Nepal and O. abei Fukumoto, Kamyia & Ohbayashi, 1986, parasitic in Ochotona hyperborea from Japan, by its caudal bursal pattern (rays 6 arising from the lateral trident before the separation of rays 5 and 6). It differs from the first species by its asymmetrical synlophe in relation to the axis of orientation of the cuticular ridges. It differs from the second one by a very different ratio of the length of the spicules to the length of the body (5 to 8% in O. erbaevae versus 15, 5 to 16% in O. abei). The definition of the genus Ohbayashinema is emended and a dichotomous key to the species is provided.
Nematoda, Trichostrongylina, Heligmosomoidea, Heligmosomidae, Ohbayashinema erbaevae n. sp., Buriatia, Lagomorpha, Ochotonidae.