Chamberlainium (Corallinales, Rhodophyta) in South Africa, an exemplar for the study of coralline algae, description of C. tenue sp. nov., biogeography of the genus, and species keys

•South African Chamberlainium, an exemplar for the study of coralline algal systematics•Description of Chamberlainium tenue, a new cryptic/pseudocryptic species of coralline algae•Integrated taxonomic approach using DNA sequences from historical and field specimens•Keys to all Chamberlainium species in South Africa•Biogeographic considerations