Maripelta rotata (E.Y. Dawson) E.Y. Dawson, the type species of the genus, is a deep-water marine red alga with a distinctive morphology, presently referred to the Rhodymeniaceae. Analyses of rbcL sequences were used to clarify the taxonomic position of M. rotata. The molecular analyses placed M. rotata within the Rhodymeniaceae with robust support. This and previous studies suggest that, among the four peltate bladeforming genera of the Rhodymeniales, Maripelta and Asteromenia belong to the Rhodymeniaceae and Halichrysis and Sciadophycus to the Faucheaceae. These investigations show that vegetative morphological features are of little taxonomic utility within the Rhodymeniales and greater importance should be attached to reproductive characters.