Abstract
Gloiosaccion Harvey, with type G. brownii (Rhodymeniaceae, Rhodymeniales), is a red algal genus characterized by the presence of large, hollow and saccate vesicle-shaped thalli arising from small solid axes. Whereas Gloiosaccion has traditionally been viewed as being closely related to Botryocladia (Agardh) Kylin, a multi-marker phylogenetic analysis based on chloroplast-encoded rbcL and UPA and nuclear LSU rDNA sequences instead places Gloiosaccion brownii and G. pumila in the Chrysymenia clade that includes the generitype C. ventricosa (Lamouroux) J. Agardh. Gloiosaccion is reduced to synonymy with Chrysymenia J. Agardh, a taxonomic move first advocated by De Toni in 1900. In addition to C. brownii (Harvey) De Toni, “Gloiosaccion” brownii var. firmum Harvey and “G.” pumilum J. Agardh are recognized as the distinct species Chrysymenia coriacea comb. et stat. nov. and C. pumila (J. Agardh) Weber-van Bosse, respectively. A new species, C. pseudoventricosa sp. nov. is proposed to accommodate specimens going under the name C. ventricosa (J.V. Lamouroux) J. Agardh from the Gulf of Mexico and Caribbean Sea.