The morphologically deviating genera Omphalodiella and Placoparmelia belong to Xanthoparmelia (Parmeliaceae)

The monotypic genera Omphalodiella and Placoparmelia were described from Patagonia (Argentina). The latter is characterized by placodioid species, morphologically similar to some subcrustose, brown Xanthoparmelia species, whereas Omphalodiella is a peltate lichen. Analyses of ribosomal DNA sequences supported their placement in the parmelioid clade. Both genera are nested within Xanthoparmelia. Affinites to the latter genus are congruent with the presence of Xanthoparmelia-type lichenan in the hyphal cell walls and an arachiform vacuolar body in the ascospores, two key characters typical of Xanthoparmelia. Consequently we propose to place the generic names in synonymy with Xanthoparmelia and transfer the two species to the latter genus as X. patagonica and X. peltata comb. nov.