Abstract Several brachiopods which belong to the same genus Horridonia of late Early and early Late Permian age in Spitsbergen and Poland, respectively, have been petrographically and geochemically analysed to verify seasonal variation in stable carbon and oxygen isotope values for palaeoclimatological implications. The specimens of Horridonia timanica from Spitsbergen show distinct cyclicity reflective of seasonal pattern, while those of Horridonia horrida from Poland do not. These differences are explained by the fact that the former lived at high palaeolatitudes at the northern margin of the supercontinent Pangaea where the seawater temperature differences between winter and summer seasons were greater, as expressed in the isotopic composition of the skeletal materials. In contrast, the shell growth of Horridonia horrida was subjected to strong evaporative influence by climatic variations in the eastern area of Pangaea.