Sematophyllum substrumulosum (Hampe) E. Britton found as a new species record for Russia in Zabaikalsky Territory in Eastern Siberia, ca. 8 000 km from its nearest localities in Southern Europe. This is the first record of the genus, as well as the family Sematophyllaceae, s. str. (excluding Pylaisiadelphaceae) from Russia. Interestingly, this species known in the Mediterranean region in temperate climate is found in Russia in mountain tundra in extremely cold environment. Description, illustrations and phytogeographical considerations are given.