Caloplaca fuscorufa H. Magn. is a poorly known species that for a long time was known only from a single locality in Jämtland, northern Sweden, where it was collected in 1910. It has been suggested to be synonymous with C. crenularia (With.) J. R. Laundon, but has also been confused with C. exsecuta (Nyl.) Dalla Torre & Sarnth. We have compared the isotype of C. fuscorufa and material collected in Sweden, Norway and Svalbard, with presumably related species, using morphology, anatomy and chemistry as well as molecular data. The results show that C. fuscorufa is a distinct species, differing from C. crenularia mainly in its somewhat larger spores with wider septa, different colour of the apothecia and a more northern distribution. It differs from C. exsecuta mainly in its chemistry and smaller spores with smaller septa. Caloplaca crenularia is shown to have a more southern distribution in Sweden than previously understood. Chemical data and a molecular analysis based on ITS data show that C. fuscorufa is related to C. crenularia and C. ammiospila, but clearly separated from these species.