Alternate Title

Platoma chrysymenoides sp. nov. (Schizymeniaceae), and Sebdenia integra sp. nov. (Sebdeniaceae), Two New Red Algal Species from the Northwestern Gulf of Mexico, with a Phylogenetic Assessment of the Cryptonemiales Complex (Rhodophyta)


Recent collecting cruises conducted in the Northwestern Gulf of Mexico at 40- to 90-m depth revealed a diverse deepwater flora that is dominated by members of the Cryptonemiales complex. In this article, we describe two species new to science, Platoma chrysymenioides sp. nov. (Schizymeniaceae) and Sebdenia integra sp. nov. (Sebdeniaceae). Chloroplast-encoded rbcL sequence analyses corroborate morphological and nuclear small subunit ribosomal RNA gene data that the red algal orders Cryptonemiales and Rhodymeniales are closely related. The allied order Nemastomatales is strongly supported to include the Nemastomataceae and Schizymeniaceae, but the phylogenetic position of the Sebdeniaceae and Tsengiaceae remains equivocal. The Cryptonemiales, Rhodymeniales, Nemastomatales, Sebdeniaceae, and Tsengiaceae form a well-supported monophyletic assemblage—the Cryptonemiales complex—within the Rhodophyta.