Lecanoraceae is the fifth largest family in the lichenized fungi, and many phylogenetic and taxonomic issues remain unresolved in the family. In this study, a phylogenetic framework of Lecanoraceae is reconstructed using a concatenated matrix of ITS, nuLSU, RPB1, RPB2 and mtSSU DNA sequences. The results show that Rhizoplaca and seven monophyletic genus-level clades, including five already named genera (Lecanoropsis, Myriolecis, Protoparmeliopsis, Sedelnikovaea, and Straminella) and two newly proposed genera, Genus 1 (formerly Lecanora polytropa group) and Genus 2 (formerly Lecanora subgenus Placodium section Dactylon), are clustered together in a highly supported clade, distant from Lecanora s. str. in Lecanoraceae. The phylogenetic relationships between these genera are clearly resolved here. A taxonomic revision on the two new genera is provided. The genus Rhizoplaca is also re-circumscribed based on the molecular phylogeny. The results show that the genus in its original circumscription, with an umbilicate thallus, is non-monophyletic. However, the core groups of the former genus and some species of Lecanora and Squamarina formed a monophyletic clade, including the Rhizoplaca chrysoleuca, R. melanophthalma, R. phaedrophthalma, R. marginalis, Lecanora valesiaca and Squamarina callichroa group. Consequently, three squamulose and lobate species, Lecanora valesiaca, Squamarina degelii and S. scopulorum, are transferred to Rhizoplaca, R. maheui and R. bullata are proved as species of Straminella, and R. macleanii is confirmed sister to the genus Lecanoropsis and only distantly related to Rhizoplaca. Therefore, the growth form should not be used as a key character in genus classification of Rhizoplaca and its related genera. Furthermore. Sixteen undescribed species were discovered in this study.
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