Two new thermotolerant species of Thielavia were isolated from Easter Island and India, after treating soil samples with 65% (v/v) ethyl alcohol: T. intermedia sp. nov. characterized by large, obovate, dark brown ascospores with a terminal germ pore; and T. arxii sp. nov. distinguished by the large, ellipsoidal to fusiform, brown ascospores with a prominent, lateral to medial germ pore. A phylogenetic study of the ITS-5.8S rDNA sequences of 18 species of Thielavia and Melanocarpus thermophilus was performed. This analysis revealed that T. intermedia could be the ancestor of the remaining species and that all the species tested were genetically closely related.