The genus Entonaema comprises Xylariaceae with hollow, gelatinous stromata that accumulate liquid. Some of its species, including the type species, appear related to Daldinia from a polyphasic approach, comprising morphological studies, comparisons of ribosomal DNA sequences, and high performance liquid chromatography (HPLC) profiles with diode array and mass spectrometric detection (HPLC-DAD-MS). This methodology was used to study Entonaema pallidum. Its major stromatal constituent was identified as xylaral, a secondary metabolite known from Xylaria polymorpha. This compound was detected in several Xylaria spp., including the tropical X. telfairii and morphologically similar taxa, whose stromata may also become hollow and filled with liquid. Cultures of E. pallidum resembled those of Xylaria, substantially differing from other Entonaema spp., in their morphology, 5.8S/ITS nrDNA sequences, and HPLC profiles. The type specimen of E. mesentericum was located in the spirit collection of the herbarium B and found to agree morphologically with the nomenclatorily younger E. pallidum. Traces of xylaral were even detected by HPLC-DAD-MS in the spirit in which the fungus had been preserved. Entonaema pallidum is thus regarded as a later synonym of E. mesentericum. Therefore, the latter name is transferred to Xylaria. A key to entonaemoid Xylariaceae is provided. Colour reactions (NH3, KOH) of the ectostroma were applied to a limited number of Xylaria spp., but metabolite profiles of cultures appear more promising as chemotaxonomic traits to segregate this genus. As xylaral was also found in Nemania and Stilbohypoxylon spp., while being apparently absent in Hypoxylon and allied genera, it may be a chemotaxonomic marker for Xylariaceae with Geniculosporium-like anamorphs