Two species of the operculate rugose coral genus Rhizophyllum from Ludlovian beds on Gotland

Two species of the operculate and calceoloid rugose coral Rhizophyllum Lindström, mainly from Ludlovian beds on Gotland, are revised and redescribed. The species treated are Rhizophyllum gotlandicum (Roemer) – type species of Rhizophyllum – and R. elongatum Lindström; the latter species is endemic to Gotland. Ontogenetic development, in particular, has been studied. Both species are rhizosessile and exhibit internal tabulated tubes (= vertical tube–channels) which are connected to the attachment structures; in R. elongatum the intracalicular offsets are connected to the attachment structures via these internal tube–channels. The septa are multitrabeculate. Platyphyllum Lindström and Rhizophylloides Spassky, Kravtsov and Tsyganko are interpreted as junior synonyms of Rhizophyllum. The morphological differences between Rhizophyllum and Calceola Lamarck are discussed. Both genera are members of the subfamily Calceolinae King.