A modern account of the South African non-geniculate Lithophylloideae (Corallinales, Corallinophycidae, Rhodophyta)

• Within the Lithophylloideae the genera Lithophyllum and Titanoderma are contentious.
• We present descriptions with new data of South African taxa ascribed to the Lithophylloideae.
• Comparisons with specimens from other geographical locations are provided.
• A key for identifying South African specimens of Lithophylloideae is included.
• Our data support the separation of the genus Titanoderma from Lithophyllum.

Of the genera within the coralline algal subfamily Lithophylloideae, the genera Lithophyllum and Titanoderma have probably been the most contentious in recent years. Two opposing taxonomic views currently exist. One view considers Titanoderma to be a heterotypic synonym of Lithophyllum, arguing that the morphological criteria proposed to separate the two genera do not stand up to rigorous testing. The other view, which is increasingly being supported by molecular data, considers Titanoderma and Lithophyllum to be distinct genera. Based on our study of numerous recently collected specimens and of detailed published accounts on the genera, we support the separation of Titanoderma from Lithophyllum as we found no difficulty in assigning species to either genus on the basis of the characters proposed to separate them. Three species of Lithophyllum (L. acrocamptum, L. incrustans, L. neoatalayense) and three species of Titanoderma (T. corallinae, T. polycephalum, T. pustulatum) are currently reported to occur in South Africa. Here we present detailed illustrated accounts of the species, including: first time detailed descriptions for South African T. corallinae and T. pustulatum; new data on female and carposporangial conceptacles; and comparisons from other geographical locations where the same species have been described in detail. A key for identifying South African specimens is included. Our data support the characterisation of the genus Titanoderma separate from Lithophyllum.