Theissenia reconsidered, including molecular phylogeny of the type species T. pyrenocrata and a new genus Durotheca (Xylariaceae, Ascomycota)

The genus Durotheca is introduced with D. depressa sp. nov., as type. Hypoxylon comedens is transferred to Durotheca, based on its morphology with further evidence from molecular phylogenetic studies; a combined β-tubulin and α-actin gene dataset. Theissenia cinerea is synonymized with D. comedens, and the type of Theissenia, T. pyrenocrata, is shown to occupy a basal, rather distant position in a monotypic clade in relation to sequenced taxa of Durotheca. This clade has an unresolved position in relation to the two informal subfamilies “Xylarioideae” and “Hypoxyloideae” within the Xylariaceae. New distributional data for D. comedens and T. pyrenocrata are presented, with the former found to be widespread in South-East Asia and the latter is reported as new from western Amazonia (Ecuador). One further species described in Theissenia, T. rogersii, is transferred to Durotheca, whilst T. eurima is accepted in Theissenia.