Pleuroxus smirnovi sp. nov. (Cladocera: Chydoridae) is found in a temporary freshwater body near Lake Zor-Kul, the Pamirs (territory of Tajikistan). This large, brownish chydorine, with especially high body compressed laterally and supplied with a sharp dorsal keel, "untypical" of the genus Pleuroxus, at the same time, has the number of setae in filter plates of gnathobases II-V typical of this genus, namely 8-8-6-4. My finding of P. smirnovi sp. nov. is a new evidence of an incomplete faunistic coverage and an imperfect state of today's systematics of the subfamily Chydorinae, because this new species has a set of characters apparently intermediate between the genera Pleuroxus BAIRD, 1843, Plurispina FREY, 1991 and Planicirculus FREY, 1991. Previously, large, compressed, and keeled chydorines were regarded as exclusively Australian, agreeing with ideas on a high endemism of the Australian cladoceran fauna. But after my finding of P. smirnovi sp. nov. we can speak only on "a predominantly Australian" distribution of such forms.