Contributions to the genus Synarthonia (lichenized Ascomycota, Arthoniaceae)

The type specimens of Synarthonia bicolor and S. stigmatidialis were examined, leading the authors to revise their descriptions as well as the generic description. Also, two new species of Synarthonia, viz. S. psoromica and S. sikkimensis are described from India. Synarthonia psoromica, collected from the Nilgiri Hills of Tamil Nadu, is characterized by immersed synascomata and the presence of psoromic acid. Synarthonia sikkimensis, collected from Sikkim-Himalaya, is characterized by the sorediate thallus with a rhizomorph-like prothallus. These distinguishing characters are observed for the first time in Synarthonia. After considering the protologue of the recently described S. sarcographoides, a comprehensive account of this genus is made. In addition, a world key to all known species of Synarthonia is provided.