Morphology and taxonomy of Corallinaceae with special reference to Clathromorphum, Mesophyllum, and Neopolyporolithon gen nov. (Rhodophyceae, Cryptonemiales)

Abstract

Three species of crustose coralline algae growing almost exclusively on articulated corallines on the west coast of North America have been grouped together in the genus Polyporolithon (Mason, 1953). However, studies of their anatomy and reproduction reveal that they belong to different genera, and they are herein treated as Clathromorphum parcum, Mesophyllum conchatum, and Neopolyporolithon reclinatum, Neopolyporolithon being newly described in this paper.The morphology of these three taxa is described with emphasis on epithallia, host-epiphyte development, and conceptacle formation. Notable are the way in which early development of C. parcum is related to the growth of its host and the manner in which spermatangial conceptacles originate in C. parcum and N. reclinatum.A new tribe in the Melobesioideae, Phymatolitheae, is described. The presence or absence of genicula, of tetrasporangial plugs, and of secondary pit-connections are important characteristics distinguishing the seven subfamilies in the Corallinaceae. In addition to structure, geographic distribution and geological ages are used in gaining insight into possible phylogenetic trends in the crustose coralline algae.