Bd. Ryan et Th. Nash, PLACODIOID TAXA OF LECANORACEAE SENSU ZAHLBR. (LICHENIZED ASCOMYCOTINA) IN NORTH-AMERICA - TAXA EXCLUDED FROM LECANORA SUBG. PLACODIUM, Nova Hedwigia, 64(3-4), 1997, pp. 393-420
This article presents a key to the placodioid (rosulate to lobate, squ
amulose, umbilicate, or dwarf fruticose) taxa of Lecanoraceae sensu Za
hlbr. in North America; and gives an overview of their systematics and
nomenclature, emphasizing the ones presently excluded from Lecanora s
ubg. Placodium sensu Poelt, especially Rhizoplaca Zopf s.l., Squamarin
a Poelt, and Solenopsora Massal. The Rhizoplaca melanophthalma and R.
chrysoleuca/R. subdiscrepans complexes are extremely problematic. Squa
marina and Solenopsora are very different from each other, and probabl
y do not belong in the same family. Lobothallia (Clauz. & Roux) Hafell
ner, Arctopeltis Poelt and Protoparmelia M. Choisy, ''Lecanora'' pring
lei and similar taxa, and ''Lecanora'' demissa are treated briefly. So
me comments are also made on the systematics and nomenclature of the L
ecanoraceae, and the genus Lecanora and its subgenera.