| abstract | The morphological ontogeny of Cosmochthonius oralensis sp. nov. from West Kazakhstan is described and illustrated. The adult of this species has thin cerotegument and microfoveae on the pygidium, as has C. minifoveolatus Gil et al., 1991, but the latter species is smaller than C. oralensis and its basal cilia on erected setae of f-series are distinctly longer than on setae of e-series; in C. oralensis these cilia are of similar length. The juveniles of both species are similar to adults, except for smaller body size and more delicate cuticle of juveniles. These species also differ from each other by the number of cilia on erected setae, both in the juveniles and adults. The morphology of C. oralensis is compared with congeners. |