A phylogenetic and taxonomic study of the Physconia distorta morphotype complex was undertaken using ITS nu-rDNA as a molecular marker to re-evaluate this group. The analysis incorporated several samples of European P. distorta and also of American and European populations, recently named as P. americana. The phylogenetic analysis revealed that P. distorta and the European population of P. americana form two monophyletic and partially sympatric species and that both are distinct from the American species P. americana. Because differences in upper cortex anatomy had been used in establishing P. americana as distinct from P. distorta, the anatomy of the upper cortex was restudied in all three of these taxa, and notable differences were revealed. Our study confirmed that the upper cortex of P. distorta is prosoplectenchymatous with thick hyphal cell walls and narrow lumina, and that American specimens of P. americana have a typical paraplectenchymatous upper cortex. The cortex anatomy of both of these looks essentially the same in both longitudinal and transverse sections. Conversely, the European specimens that have been called P. americana are different from both of these. The cells of the upper cortex are rather thin walled, and in transverse lobe sections the cortex closely resembles a paraplectenchyma. However, in longitudinal lobe sections these thin walled cells can be seen to be elongate and ramified, obviously hyphal in nature, and better meeting the criteria of a prosoplectenchyma. The results confirmed the evolutionary pattern and taxonomic assessment of the anatomy of the upper cortex in the genus Physconia and revealed a common undescribed species (P. thorstenii sp. nov.) that can be added to the North African and Southern Euro-Asiatic lichen flora.