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Micracanthodinium setiferum is a very distinctive but poorly known dinophyte with characteristically delicate, unbranched, filiform and pointed setae. A recent study by Mertens et al. (2022, Palynology 46: 1934908) aims to clarify the taxonomy of the species and to introduce two new formae acknowledging the presence or absence of setae in environmentally collected cells. We assert that the epitype choice of illustrations by these authors is inappropriate, but also not achieved following the rules of the International Code of Nomenclature for algae, fungi, and plants (ICN). Additionally, the two new formae are not described in accordance with the rules of the ICN. A more suitable epitype may therefore be chosen, once corresponding physical material from the type locality off Sicily is at hand. The taxonomic identity of M. setiferum meanwhile remains elusive.

The contemporary occurrence of dinophytes at their type localities has not been intensely studied so far, despite the type locality's crucial importance for any reliable scientific name application. The microscopist and phycologist Ch.G. Ehrenberg described a number of dinophyte species more than 150 years ago, many of which are currently taxonomically ambiguous. We collected water tow and sediment samples at those same localities in Berlin that Ch.G. Ehrenberg may have visited as well. We isolated and established several strains of Glenodinium apiculatum that we investigated by applying contemporary microscopic and molecular methods. The plate formula of the species was 4′, 2a, 7″, 6c, 5s, 5′″, 2″″, without an apical pore complex, and the most distinctive morphological trait of Glenodinium apiculatum was the spiny hypotheca. The spines were irregularly scattered over hypothecal plate surface and arranged in raised edges between thecal plates. As inferred from molecular phylogenetics, Glenodinium apiculatum is assigned to Palatinus, which is an element of the Peridiniopsidaceae as a part of the Peridiniales. For taxonomic purposes, we epitypified Ch.G. Ehrenberg's taxon with newly collected material to ensure a reliable determination in the future. Palatinus apiculatus is not a fleeting star, and a number of dinophytes show a remarkably high fidelity to the sites from which they were originally described, even if the description was carried out a long time ago.

The taxonomy of Gymnodinium and the Gymnodiniaceae is inconsistent, because the systematic position of the type species, G. fuscum, is elusive at present. Historical names of microscopic species are frequently ambiguous, making reliable determination difficult, although it is crucial to fully explore the biology of the organisms. We collected material at the type locality of a historical variety, namely Gymnodinium fuscum var. rubrum, var. nov., and established a strain for morphological and molecular studies. The motile cells showed a characteristically obovate shape in outline, with acute antapex, and a horseshoe-shaped apical structure complex, which is characteristic for many Gymnodiniaceae. Older cultivated material further exhibited red granules in the cell, being the name-giving diagnostic character of the variety. In a molecular phylogeny, monophyletic Gymnodiniaceae segregated into seven clades at high taxonomic level. The phylogenetic resolution of the molecular DNA-tree provides evidence for a dynamic evolutionary scenario of Gymnodiniaceae and might prove helpful for an improved classification of the group. As the taxonomic result, we validate and epitypify the historical name, G. fuscum var. rubrum, var. nov., showing diagnostic traits such as a descending (but not straight) cingulum and a reciprocal size ratio between episome and hyposome in comparison to the regular form of G. fuscum.

Peridinium cinctum is a common freshwater dinophyte with a long history of research. Erich Lindemann was the first to assess intraspecific variability in this species focusing on plate pattern variation. Since then, this issue has been neglected but with the application of DNA sequence diagnostics, a combination of morphological and molecular characters may enable taxonomic delimitations. Our aim was to identify distinct morphotypes using plate pattern as the main characteristic and then compare them to the geographic occurrence of particular ribotypes (as inferred from sequences of the Internal Transcribed Spacer: ITS) in samples from Central Europe. Approximately 200 observations were carried out under the inverse light microscope for each of a total of 15 strains. We observed two main variations from the abundant plate pattern in P. cinctum, namely an unusual position of the 2a plate and the irregular shape of the 1a plate. In 88 (predominantly clonal) strains, we identified five different ribotypes (submitted as 71 new GenBank entries) which had no clear correlation to the defined morphotypes and/or spatial occurrences. In four cases, we detected two distinct ribotypes at the same locality. However, samples collected south of the Danube River presented a different predominant morphotype from the rest of the samples, thus implying a potential biogeographic signal as inferred from morphology. In general, there is morphological and molecular variability in P. cinctum, which is under-studied and which may uncover geographic or ecological correlations or even the existence of cryptic species.

The Scrippsiella trochoidea species complex (Thoracosphaeraceae, Peridiniales) consists of a cryptic diversity and multiple species, for which established scientific names are not available at present. Previously, the name Scrippsiella trochoidea has been taxonomically clarified, leaving a reliable determination of morphologically similar, but only distantly related species impossible. We isolated and cultivated Scrippsiella erinaceus comb. nov. (strains GeoM*533 and GeoM*534) from material collected near the type locality off Rovinj, Republic of Croatia (Adriatic Sea). We barcoded the species of the Thoracosphaeraceae using rRNA sequences (including 22 new sequences) and investigated the morphology of the strains using light and electron microscopy. The Scrippsiella trochoidea species complex was composed of three primary clades, and the Adriatic strains were reliably assigned to one of them being distinct from the true Scrippsiella trochoidea. We designate an epitype for the basionym Rhabdosphaera erinaceus prepared from the strain GeoM*534. The unambiguous links between a scientific species name, its protologue, genetic characterization and spatial distribution have particular importance for character-poor, unicellular organisms such as the Dinophyceae.

Bauer, Wolfgang, Gottschling, Marc, Keupp, Helmut, Kusber, Wolf-Henning, Mertens, Kenneth N. (2021): Validation of the calcareous dinophyte Wallidinellum (Peridiniales), with notes on the status of fossils in the Code. Phytotaxa 520 (3): 296-300, DOI: 10.11646/phytotaxa.520.3.9, URL: http://dx.doi.org/10.11646/phytotaxa.520.3.9

Amphidoma is an old though poorly studied thecate dinophyte that has attracted attention recently as a potential producer of azaspiracids (AZA), a group of lipophilic phycotoxins. A new species, Amphidoma parvula, sp. nov. is described from the South Atlantic shelf of Argentina. With a Kofoidean thecal plate pattern Po, cp, X, 6′, 6′′, 6C, 5S, 6′′′, 2′′′′, the cultivated strain H-1E9 (from which the type material of Am. parvula, sp. nov. was prepared) shared the characteristic plate arrangement of Amphidoma each with six apical, precingular and postcingular plates. Amphidoma parvula, sp. nov. differs from other species of Amphidoma by a characteristic combination of small size (10.7–13.6 µm in length), ovoid shape, high length ratio between epitheca and hypotheca, and small length ratio between apical and precingular plates. Other morphological details, such as the number and arrangement of sulcal plates and the fine structure of the apical pore complex support the close relationship between Amphidoma and the other known genus of Amphidomataceae, Azadinium. However, Am. parvula, sp. nov. lacks a ventral pore, a characteristically structured pore found in all contemporary electron microscopy studies of Amphidoma and Azadinium. As inferred from liquid chromatography coupled with tandem mass spectrometry, Am. parvula, sp. nov. did not produce AZA in measurable amounts. Molecular phylogenetics confirmed the systematic placement of Am. parvula, sp. nov. in Amphidoma (as sister species of Amphidoma languida) and the Amphidomataceae. The results of this study have improved the knowledge of Amphidomataceae biodiversity. Fil: Tillmann, Urban. Alfred Wegener Institut; Alemania Fil: Gottschling, Marc. Universität München; Alemania Fil: Guinder, Valeria Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Argentino de Oceanografía. Universidad Nacional del Sur. Instituto Argentino de Oceanografía; Argentina Fil: Krock, Bernd. Alfred Wegener Institut; Alemania