Author	Fensome, R.A., Taylor, F.J.R., Norris, G., Sarjeant, W.A.S., Wharton, D.I. and Wil
Year	1993a
Journal	Micropaleontology Press, Special Publication Number 7.
Title	A classification of living and fossil dinoflagellates.

Abstract Fensome, R.A., Taylor, F.J.R., Norris, G., Sarjeant, W.A.S., Wharton, D.I. and Williams, G.L., 1993: A classification of living and fossil dinoflagellates; Micropaleontology Press, Special Publication Number 7. Abstract Dinoflagellates (division Dinoflagellata) constitute a group of primarily single-celled organisms (protists) which have two flagella: a transverse flagellum which is ribbon-like with multiple waves and beats to the cell"s left; and a longitudinal flagellum which beats posteriorly and has only one or a few waves. In all dinoflagellates, the nuclear membrane does not break down during mitosis, which is thus said to be "closed", the mitotic spindle being extranuclear; in most other eukaryotes, the nuclear membrane breaks down during mitosis (which is thus "open") and the mitotic spindle enters the nucleus. All dinoflagellates, except members of the subdivision Syndinea, have a dinokaryon - a nucleus characterized by chromosomes which remain condensed between cell divisions and by a lack of histones. Molecular and ultrastructural comparisons indicate that dinoflagellates are most closely related to ciliates and apicocomplexans (sporozoans) and, together with these groups of protists, constitute a sister clade to the chromopyyte algae (diatoms, silicoflagellates and others). Living dinoflagellates are found in most aqueous environments. Fossil dinoflagellates are widespread in Mesozoic-Cenozoic marine sedimentary rocks and also occur in some strata of nonmarine origin. They are a prominent cause of red tides and paralytic shellfish poisoning and their cysts are of value as biostratigraphic index fossils. Exchange of ideas between dinoflagellate neontologists and paleontologists has been made difficult because of the lack of a comprehensive evolutionary hypothesis or its corollary, a phylogenetically-based classification scheme treating extant and fossil taxa equally. To this end, we have produced a scheme in which the division Dinoflagellata is divided into: two subdivisions and three classes, primarily on the basis of nuclear strategy (i.e. whether the nucleus is a dinokaryon or of a more conventional eukaryotic type and, if a dinokaryon, whether it occurs throughout the life-cycle or only during part of it); five subclasses on the basis of general tabulation type; fourteen orders, ten suborders and fifty-six families, on the basis primarily of distinctive differences in tabulation pattern; and twenty-two subfamilies, on the basis of less distinctive differences in tabulation pattern and also distinctive differences in the general morphology of the cell or cyst. The classification, and the phylogenetic hypothesis that derives from it, supports the following premises: 1) that below the rank of class, amphiesmal structure, especially tabulation, is the most valuable and meaningful criterion in classifying dinoflagellates; 2) that the use of cell or cyst habit (i.e. general shape or morphology) in classifying dinoflagellates should be restricted in its use primarily to subfamily and, less commonly, higher rank; 3) that, although incomplete and despite the sporadic evidence of Paleozoic dinoflagellates, the fossil record supports a major adaptive radiation of dinoflagellates during later Triassic and earlier Jurassic times; 4) that the majority of living thecate dinoflagellate can be interpreted as having either a peridinialean or gonyaulacalean tabulation, and that these tabulations, and hence the orders Gonyaulacales and Peridiniales, have been separate since at least the Early Jurassic. The following taxa are new or are validated herein: subdivision Dinokaryota; classes Blastodiniphyceae and Noctiluciphyceae; subclasses Dinophysiphycidae, Gymnodiniphycidae, Peridiniphycidae and Prorocentrophycidae; orders Ptychodiscales and Suessiales; suborders Ceratiineae, Cladopyxiineae, Glenodiniineae, Goniodomineae and Heterocapsineae; families Amphitholaceae, Dicroerismaceae, Dollidiniaceae, Heterocapsaceae, Lotharingiaceae, Mancodiniaceae, Suessiaceae and Symbiodiniaceae; and subfamilies Calciodinelloideae, Cribroperidinioideae, Gambierdiscoideae, Helgolandinioideae, Leptodinioideae, Lithoperidinioideae, Luehndeoideae and Pyrodinioideae. The following names are at revised rank: division Dinoflagellata; suborder Actiniscineae; and subfamilies Broomeoideae and Dinogymnioideae. The generic name Damassadinium is proposed as a substitute for Danea Morgenroth non Danaea Smith. As a result, the following combinations are new: Damassadinium abbreviatum, Damassadinium californicum, Damassadinium chibane, Damassadinium crassimuratum, Damassadinium fibrosum, Damassadinium heterospinum, Damassadinium impages and Damassadinium manicatum. Several new terms are proposed. The terrn "climactal" is applied to thecal plates anterior to the precingular series, outside the sulcus and excluding the apical pore complex. The term "fundital" is applied to thecal plates posterior to the postcingular series and outside the sulcus. "Dextral torsion" is a term applied to gonyaulacalean tabulations in which the boundary between the fourth and fifth postcingulars (4""/5"") approaches a middorsal position and thus lies proximal of the boundary between the third and fourth precingulars (3"/4"), as in cribroperidinioideans. "Sinistral torsion" is the term applied when the boundary 4""/5"" lies significantly distal of the boundary 3"/4", as in some leptodinioideans. The intermediate situation is termed "neutral torsion" and occurs in other leptodinioideans. The term "Eaton series" is introduced for one of the successive latitudinal series of plates in a sequence from the cingulum to the pole.