A Gordian knot: Nomenclature and taxonomy of Heterocapsatriquetra (Peridiniales: Heterocapsaceae)

Abstract

In the course of polyphasic taxonomic work in the dinophytes, we became aware of a fundamental misapplication of the name Glenodinium triquetrum (now represented conceptually by a species of Kryptoperidinium), when Stein assigned it to Heterocapsa. Possible solutions involve a conflict between retaining Ehrenberg’s epithet in its correct application in the interest of priority and preserving current usage of Heterocapsa. However, we do not achieve a consensus on how to disentangle this Gordian knot, underlining that this is not a regular case of taxonomic confusion. We intend to stimulate a more general discussion about best practices in such cases, balancing between the interest of nomenclatural practicability and the respectful acknowledgement of scientific work, even if it was conducted many years ago.

Glenodinium triquetrum Ehrenb. is a species not of Heterocapsa F.Stein but of Kryptoperidinium Er.Lindem. (Kryptoperidiniaceae, Peridiniales)

“…are linked in a unfortunate way: The type of Heterocapsa, namely the well-established Heterocapsa triquetra (Ehrenb.) F.Stein, is demonstrably an element of Kryptoperidinium in its current circumscription (Gottschling et al 2018b). This was uncovered 130 years after the combination from Glenodinium Ehrenb.…”

“…This was uncovered 130 years after the combination from Glenodinium Ehrenb. to Heterocapsa was made (Stein 1883: 13), and we aim at overcoming the severe nomenclatural and taxonomical consequences (Gottschling et al 2018b) by the proposal to conserve the type of Heterocapsa (Gottschling et al 2018a) with Heterocapsa steinii Tillmann, Gottschling, Hoppenrath, Kusber & Elbr. (Tillmann et al 2017).…”

“…Corresponding water-colour drawings ( Fig. 1 in Gottschling et al 2018b) show yellow-green dinophyte cells that are ovate through elliptical in dorsal or ventral view and have an eyespot (the reason why the species was initially described under Glenodinium). The epithet refers to the diagnostic triangular outline in lateral view, a result of ventral (and concave) flattening of the cell, doubtlessly assigning the taxon to Kryptoperidinium in its accepted concept.…”

“…Kryptoperidinium circumscribes very peculiar dinophytes, last but not least because of the characteristic ventral flattening of the cell (Ehrenberg 1840, Stein 1883, Lindemann 1924, Gottschling et al 2018b. In molecular trees, two distinct ribotypes of Kryptoperidinium can be distinguished (Gottschling & McLean 2013Fig.…”

“…nov.) should be clarified with priority. As first step, a lectotype was designated for G. triquetrum in Gottschling et al (2018b;see below).…”