Morphology of the ontogenetic stages of the Neotropical oribatid mite Platynothrus altimontanus Hammer, [1958. Investigation on the Oribatid fauna of the Andes Mountains. I. The Argentina and Bolivia. Biol. Skr. Dan. Vid. Selsk. 10(1), 121] is described and illustrated based on specimens from Ecuador and compared with specimens from Venezuela, which is a new record of its distribution. Moreover it is compared with type material and holotype of the most similar species Platynothrus major Hammer, [1966. Investigations on the oribatid fauna of New Zealand. Teil 1. Biol. Skr. Dan. Vid. Selsk.15(2), 108]. On the basis of present studies there is a possibility that P. major is a junior synonym of P. altimontanus or its sibling species.Specimens were found in samples of moss, soil, litter and detritus from forest patch, below trees, near riverbank and of decomposing tree stump, from very wet accumulated litter at the rocks, under paramo grass and pillow-plants. All samples were collected from Ecuador (provinces Pichincha, Illiniza and Cotopaxi, at 2750–4200ma.s.l.) and Venezuela.