On the identity of Chiloplacus subtenuis Rashid & Heyns, 1990 and C. tenuis Rashid & Heyns, 1990 (Rhabditida: Cephalobidae), with description of C. mysteriosus sp n.

Type material of Chiloplacus subtenuis and C. tenuis was studied and Iberian material originally described as C. tenuis re-examined. The results provided relevant new information to elucidate the identity of these species with more accuracy. On studying their type material, new features and details of C. subtenuis and C. tenuis were observed concerning the nature of the lip margin, morphology of the labial probolae, the lateral field at vulval level, and the orientation of the vulva (ventral or subventral). Re-examination of Iberian material of C. tenuis revealed that it consists of specimens belonging to three taxa: C. tenuis, C. membranifer, and an unknown species described and named herein as C. mysteriosus sp. n. The morphology of lip region in representatives of Chiloplacus is analysed and discussed. Zeldia spannata is transferred to Chiloplacus as C. spannatus comb. n. and Chiloplacus juniperi is regarded as a junior synonym of Nothacrobeles nanocorpus.