Recommendations for epitypification of dinophytes exemplified by Lingulodinium polyedra and molecular phylogenetics of the Gonyaulacales based on curated rRNA sequence data

•7 lineages at high taxonomic level based on rRNA alignment of curated DNA sequences.•character evolution with loss of X-plate inside Gonyaulacales.•Transformation from sexiform towards quinqueform hypothecal conformation.•Taxonomy of Lingulodinium polyedra clarified by epitypification.•Epitype collected close to the type locality and capturing original author's intent. Gonyaulacales include a considerable number of harmful algae and to understand their origin and rise, knowledge of the evolutionary relationships is necessary. Many scientific names of protists introduced prior to the availability of DNA analytics are ambiguous and impede communication about biological species and their traits in the microbial world. Strains of Lingulodinium polyedra were established from its type locality in the Kiel Fjord (Germany) to clarify its taxonomy. Moreover, the phylogeny of Gonyaulacales was inferred based on 329 rRNA sequence accessions compiled in a curated sequence data base, with as much as possible type material equivalents included. Gonyaulacales were monophyletic and segregated into seven lineages at high systematic level, of which †Lingulodiniaceae constituted the first branch of the Gonyaulacales. Their type species had a plate formula APC (Po, X, cp), 3′, 3a, 6′′ 6c, 6s, 6′′′, 2′′′′ and is taxonomically clarified by epitypification. Recommendations for this important taxonomic tool are provided, with a focus on microorganisms. Most gonyaulacalean taxa established at generic rank are monophyletic, with Alexandrium, Coolia and Gonyaulax as notable exceptions. From an evolutionary perspective, gonyaulacalean dinophytes with quinqueform hypotheca are monophyletic and derive from a paraphyletic group showing the sexiform configuration. [Display omitted]