Bysmatrum biechelerae Haifeng Gu & K. N. Mertens 2025, sp. nov.

Bysmatrum biechelerae Haifeng Gu & K.N.Mertens, sp. nov. Synonym: Peridinium sociale Biecheler, 1952, p. 59, figs XXXIII–XXXV, nom. illeg. Holotype (icon!): Biecheler (1952: fig. XXXIV, illustrating the plate tabulation). Type locality: Étang de Thau, Occitania, Mediterranean France. Description: Thecate dinoflagellate with a pentagonal cell-shape, 45–60 μm in length. Yellow-green elongate chloroplasts. Eyespot present. Hypothecal, sausage-shaped nucleus. Reticulated thecal plates. Growth bands can be present. Trapezoidal shape of apical pore complex. Kofoidian plate formula is Po, X, 4ʹ, 3a, 7ʹʹ,?C,?S, 5ʹʹʹ, 2ʹʹʹʹ. Second anterior intercalary plate does not contact third anterior intercalary plate, as for the genus. First anterior intercalary plate quadrangular, second anterior intercalary plate hexagonal, and third anterior intercalary plate pentagonal. Two to three antapical spines present on 1ʹʹʹ, 5ʹʹʹ, 2ʹʹʹʹ. Cingular displacement 1.5–2.0. Sulcus widens towards the antapex. Based upon Biecheler (1952: 59–63). Etymology: named for Berthe Biecheler (1901–1939) of the Station Biologique de l’Université de Montpellier à Sète, France; see Moestrup & Enevoldsen (2019) for an account of her life and premature demise. Her thesis work was published posthumously in 1952 (Biecheler, 1952). Registration: http://phycobank.org/105199