Diversity and Morphology of Planktonic Species of the Order Dinophysales (Dinoflagellata) from the Tropical Mexican Pacific and the Gulf of Mexico

There has been an increasing interest in studying species of the thecate dinophysoid dinoflagellates, especially the genera Dinophysis and Phalacroma, all around the world. Abundant net phytoplankton material collected from coasts of the western coast of Baja California, the central Mexican Pacific (including the Gulf of California), and the Gulf of Mexico was analyzed, and the diversity and morphology of planktonic species of dinophysoids were studied in certain detail by LM and SEM. Particular morphological characteristics, which can be critical, such as the structure of the cingulum and cingular lists, union of sulcal lists, and theca ornamentation, were observed using SEM. Seventy-five (75) taxa (73 species and two varieties) were found and identified, which belong to the following 10 genera: Amphisolenia, Citharistes, Dinofurcula, Dinophysis, Histioneis, Metaphalacroma, Ornithocercus, Oxyphysis, Phalacroma, and Pseudophalacroma. We also included the following four new records: three for the Mexican Pacific (Amphisolenia brevicauda, A. deltiana, and Phalacroma stenopterygium) and one for the Gulf of Mexico (Phalacroma ornamentatum). Descriptions, illustrations, measurements, and distribution data are provided for each species. Taxonomical remarks concerning synonymies of species of the genus Phalacroma were added. Phalacroma whittingiae (Balech) Esqueda-Lara et Hernández-Becerril nov. comb. is a new taxonomic proposal.