Dual nomenclature in dinoflagellates is supported under the current nomenclatural code for algae, fungi and plants and allows a fossil-defined (usually cyst) species to bear a name other than that of its equivalent non-fossil species, as established for example by incubation experiments. Two names can then apply to the same cyst morphotype, reflecting the separate concepts and criteria used for fossil- and non-fossil taxa. Fossil-species are normally and logically assigned to fossil-genera and non-fossil species to non-fossil genera, a practice that facilitates dual nomenclature. Inconsistencies and ambiguities arise when binomials combine the names of fossil- with non-fossil taxa. Examples of this hybridized nomenclature and its consequences are examined, with problems identified and potential solutions discussed. Accordingly, a new non-fossil genus Lingulaulax is proposed with Lingulaulax polyedra (von Stein 1883) comb. nov. as its type and equivalent to the fossil-species Lingulodinium machaerophorum (Deflandre and Cookson 1955) Wall 1967, along with the new combination Lingulaulax milneri (Murray and Whitting 1899); the genus Lingulodinium Wall 1967 is retained in its exclusively fossil status. The non-fossil name Gonyaulax ellegaardiae Mertens et al. 2015 is validly published herein