When colonizing stone monuments, microcolonial black fungi are considered one of the most severe and resistant groups of biodeteriorating organisms, posing a very difficult challenge to conservators and biologists working with cultural heritage preservation. During an experimental survey aimed to isolate fungi from a biodeteriorated limestone art piece in the Old Cathedral of Coimbra, Portugal (a UNESCO World Heritage Site), an unknown microcolonial black fungus was retrieved. The isolated fungus was studied through a complete examination based on multilocus phylogeny of a combined dataset of ITS rDNA, LSU and rpb2, in conjunction with morphological, physiological, and ecological characteristics. This integrative analysis allows for the description of a new family, Aeminiaceae fam. nov., a new genus Aeminium gen. nov., and a new species, Aeminiumludgeri sp. nov., in the order Capnodiales.