Tabulation in Dinoflagellates

Mona Hoppenrath and Juan F. Saldarriaga

The patterns formed by alveolae and the thecal plates sometimes contained in them (tabulation) have been used in the taxonomy of dinoflagellate motile stages for more than 100 years. Six fundamental types of tabulation can be recognized (Figs A-E):

Fig. A. Gymnodinoid tabulation Fig. B. Suessoid tabulation Fig. C. Peridinoid / gonyaulacoid tabulation Fig. D. Dinophysoid tabulation Fig. E. Prorocentroid tabulation. Periflagellar area with tiny platelets (in pink)
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Drawings modified after Fensome et al. 1993. © Mona Hoppenrath

A convention, the “Kofoid System” of tabulation, is currently in universal use (Fig. F). The plates in each latitudinal series are numbered from the cell’s left to right, beginning with the plate closest to the midventral position. It also uses a notation to designate the series, using primes to indicate the apical ('), precingular (''), postcingular ('''), and antapical ('''') plates, both when labelling plates on figures and when producing a plate formula. The latter is a listing of the total number of plates in each series for a species or genus. Thus Peridinium is represented by APC, 4', 3a, 7'', 5C + t, 6S, 5''', 2'''' and Gonyaulax by APC 3', 2a, 6'', 6C + t, 6S, 6''', 1p, 1''''. Cingulars (C), sulcals (S), anterior intercalaries (a), and posterior intercalaries (p) are designated by letters. The t plate is a small transitional plate between the cingulars and the sulcals at the proximal end of the girdle in peridinioids and at the distal end in gonyaulacoids. Other distinctions between peridinioids and gonyaulacoids include the common occurrence of 2–3a, 7'', 5''', 2'''' in the former and 6'', 6''', 1p, 1'''' in the latter (exceptions being due to apparent suture loss or plate subdivisions). Basic symmetry: the former tending to bilateral symmetry, the latter showing evident torsion.

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Fig. F. Kofoid system of tabulation. © Mona Hoppenrath

Although the Kofoid System is usually easy to apply, ambiguities in the attribution of some plates to one series or another can cause problems. This, combined with the mechanical, consecutive numbering, renders the system poor for intergeneric comparisons. Taylor (1980) introduced an alternative model of plate nomenclature (Figs will be added), elaborated on by Evitt (1985). It consists of three epithecal polar (A–C), six pre-equatorial (1–6), six equatorial (a–f), six postequatorial (I–VI), and three hypothecal polar (X–Z) sectors, which represent hypothetical primary plates from which homologous plates can be recognized by assuming subdivisions, suture losses, and plate size and position changes. The first step is to normalize the cell to a sphere, removing obvious plate distortions. Then the primary plates and their sutures are determined by studying the relationships of the plates to each other (see examples given by Evitt 1985).

The cingulum divides the cell into an anterior body portion, the episome (epicone, epitheca) and a posterior hyposome (hypocone, hypotheca). If the distal and proximal ends of the cingulum do not meet at an equal level at the sulcus they are said to be displaced. Displacement may be left-handed (the most common condition), in which the proximal (left) end is more anterior, or right-handed. The degree of displacement is measured in cingular-widths, given from the upper edges. The sulcus can extend on the episome and stops at the posterior of the cell. In athecate (wall-less<) cells there is a thin anterior groove, the acrobase, which reaches the cell’s apex. Acrobases can be straight, sigmoid, or form loops around the apex of the cell.

During cytokinesis the plane of cell cleavage is typically oblique. In thecate species the theca may be shared by the daughter cells, with synthesis of the missing components (desmoschisis), or the parent theca may be cast off, each daughter cell forming a complete new theca (eleutheroschisis).


Evitt, W. R. 1985. Sporopollenin Dinoflagellate Cysts: Their Morphology and Interpretation. American Association Stratigraphic Palynologists Monograph Ser. 1.

Fensome R. A., F. J. R. Taylor, G. Norris, W. A. S. Sarjeant, D. I. Wharton, and G. L. Williams. 1993. A classification of living and fossil dinoflagellates. Micropaleontology Special Publication 7, Sheridan Press, Hanover, Pennsylvania, USA.

Taylor, F. J. R. 1980. On dinoflagellate evolution. BioSystems 13:65-108.

About This Page

Mona Hoppenrath
Forschungsinstitut Senckenberg, German Centre for Marine Biodiversity Research, Wilhelmshaven, Germany

University of British Columbia, Vancouver, British Columbia, Canada

Correspondence regarding this page should be directed to Mona Hoppenrath at and Juan F. Saldarriaga at

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