After a short introduction on the reef development during the Late Palaeozoic, the tectono-stratigraphic history of the Cantabrian Mountains (northern Spain) during the Carboniferous is discussed, with an emphasis on the tectonically active Pennsylvanian (i.e., Late Carboniferous). The reef-bearing Valdeteja, San Emiliano, and Cuera formations are briefly described, and their brachiopod faunas are discussed with special emphasis on adaptations to a reef environment. The brachiopod faunas are compared with similar faunas from carbonate-platform deposits with reef structures of Mississippian (i.e., Early Carboniferous) age from Northwest Europe (the British Isles in particular), with Pennsylvanian-Permian faunas from the Alps, Urals, Spitsbergen and Arctic Canada, and with Permian reef faunas from Texas (USA). The Bashkirian brachiopod faunas of the Valdeteja Formation resemble the similarly aged Hare Fiord fauna from Arctic Canada most. This makes one wonder whether the connection between the Palaeotethys and Arctic Canada was through the Urals sea and Arctic, as generally believed, or whether there was another connection from the Cantabrian Mountains to the north along eastern North America.