Heterodea Nyl.
Thallus foliose, lobate, becoming erect, or spreading irregulary on the substrate. Lobes flat to moderately ascending, sometimes strongly recurved. Upper surface smooth, without isidia or soredia, maculae or pseudocyphellae. Photobiont green, protococcoid, in a ± continuous layer below upper cortex. Lower surface lacking a cortex, felt-like, sometimes veined, sparsely to moderately rhizinate. Apothecia marginal. Ascospores simple, ellipsoid, colourless, 8 per ascus. Pycnidia marginal, sessile, subspherical.
Heterodea is best developed in Australia and contains two species one of which, H. beaugleholei Filson, is endemic there. H. muelleri, the more common of the two, is found in all southern regions and along the east coast of Australia as well as in New Caledonia and New Zealand. The genus has morphological affinities with the family Parmeliaceae although studies of the fruits have suggested links with the family Cladoniaceae. Filson [ Lichenologist 10: 13-25 (1978)] proposed the monogeneric family Heterodeaceae to accommodate Heterodea.
