• 18S rDNA phylogeny;
  • Austrolithoideae;
  • Choreonema;
  • Choreonematoideae;
  • Corallinaceae;
  • Corallinales;
  • Hapalidiaceae;
  • Melobesioideae;
  • Sporolithaceae

Phylogenetic analyses of 18S rDNA gene data for Choreonema thuretii (Corallinales, Rhodophyta) and available data for other coralline red algae indicated that Choreonema belongs to the same lineage as other taxa of Corallinales possessing tetra/bisporangial conceptacles with multiporate plates. These results, when integrated with extant morphological/anatomical data, ultrastructural data, and taxonomic data led to the conclusion that all taxa of Corallinales possessing multiporate conceptacles belong to a distinct family, the Hapalidiaceae. Recognition of the Hapalidiaceae as a distinct family was supported both phylogenetically and phenetically. The Hapalidiaceae includes those taxa of Corallinales whose tetrasporangia produce zonately arranged spores and whose tetra/bisporangia are borne in conceptacles, produce apical plugs, and develop beneath multiporate plates. The Hapalidiaceae includes the subfamilies Choreonematoideae, Melobesioideae, and Austrolithoideae, formerly placed in the Corallinaceae sensu lato. The Choreonematoideae lack cell connections between adjacent vegetative filaments and have a multiporate plate that is acellular at maturity, consisting only of a calcium carbonate matrix. The Austrolithoideae and Melobesioideae both have cellular pore plates; taxa of Melobesioideae have cell fusions between cells of adjacent vegetative filaments, whereas taxa of Austrolithoideae lack cellular connections between adjacent vegetative filaments. Inclusion of the Austrolithoideae in the Hapalidiaceae was based entirely on morphological/anatomical evidence; molecular evidence currently is lacking. Relevant historical and nomenclatural data are included.