The tropical genus Thamnomyces is characterized by having wiry, black, brittle stromata and early deliquescent asci, lacking an amyloid apical apparatus. Thamnomyces is regarded as a member of the Xylariaceae because the morphology of its ascospores and the anamorphic structures are typical for this family. However, its relationship to other xylariaceous genera remained to be clarified. Cultures of three Thamnomyces species were obtained and studied for morphological characters, and their secondary metabolite profiles as inferred from high performance liquid chromatography coupled with mass spectrometric and diode array detection (HPLC-MS/DAD) were also compared. Cultures of Thamnomyces closely resembled those of the genera Daldinia and Phylacia and even produced several secondary metabolite families that are known to be chemotaxonomic markers for the aforementioned genera. These findings were corroborated by a comparison of their 5.8S/ITS nrDNA sequences. We conclude that Thamnomyces, Daldinia, and Phylacia are derived from the same evolutionary lineage, despite these genera differing drastically in their stromatal morphology and anatomy. Along with Entonaema and Rhopalostoma, these fungi comprise an evolutionarily derived lineage of the hypoxyloid Xylariaceae. A new species of Thamnomyces is erected, and preliminary descriptions of three further, potentially new taxa are also provided