Morphology and Molecular Phylogeny of a New Marine, Sand-dwelling Dinoflagellate Genus, Pachena (Dinophyceae), with Descriptions of Three New Species

20 pages, 10 figures, 1 table, supporting information https://doi.org/10.1111/jpy.12984Marine benthic dinoflagellates are interesting not only because some epiphytic genera can cause harmful algal blooms but also for understanding dinoflagellate evolution and diversification. Our understanding of their biodiversity is far from complete, and many thecate genera have unusual tabulation patterns that are difficult to relate to the diverse known phytoplankton taxa. A new sand-dwelling genus, Pachena gen. nov., is described based on morphological and DNA sequence data. Three species were discovered in distant locations and are circumscribed, namely, P. leibnizii sp. nov. from Canada, P. abriliae sp. nov. from Spain, and P. meriddae sp. nov. from Italy. All species are tiny (about 9–23 μm long) and heterotrophic. Species are characterized by their tabulation (APC 4′ 3a 6′′ 5c 5s 5′′′ 2′′′′), an apical hook covering the apical pore, an ascending cingulum, and a sulcus with central list. The first anterior intercalary plate is uniquely “sandwiched” between two plates. The species share these features and differ in the relative sizes and arrangements of their plates, especially on the epitheca. The ornamentation of thecal plates is species-specific. The new molecular phylogenies based on SSU and LSU rDNA sequences contribute to understanding the evolution of the planktonic relatives of Pachena, the ThoracosphaeraceaeThis work was supported by a postdoctoral research salary to MH and AY from the Assembling the Tree of Life grant (NSF #EF‐0629624) and operating funds to BSL from the National Science and Engineering Research Council of Canada (NSERC 2019‐03986); AR thanks R. Gallisai (ICM‐CSIC) and T. Slámová (Univ. Prague, Czech Republic) for their help during samplings and samples processing. AR was funded by a MECD grant “Estancia de Movilidad en el extranjero José Castillejo” (CAS17/00237), a “Senckenberg Taxonomy Grant 2017″, and a DAAD “Research Stays for University Academics and Scientists 2018” Grant (91644317). CTS thanks Prof. Antonella Lugliè for the continuous and important economic and scientific support. CTS was funded by a DAAD Grant within the “Research Stays for University Academics and Scientists 2014” Grant (A/14/01530)With the funding support of the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S), of the Spanish Research Agency (AEI