Notes: This genus appears heterogeneous even after the segregation of Durotheca by Læssøe et al. (2013) with respect to both teleomorph and anamorph morphology. The phylogeny of Ju et al. (2007) based on protein coding genes suggests affinities to both Biscogniauxia (Graphostromataceae) and Whalleya (Lopadostomataceae). Further studies will show whether Theissenia, which has been regarded as a basal or even doubtful member of the Xylariaceae s. lat., can be assigned to one of the aforementioned families or whether the genus and the related Durotheca will have to be elevated to a family of their own. From a phylogenetic point of view, it cannot be retained in the Xylariaceae and was also found to be quite distant to the taxa that are here regarded as Hypoxylaceae.