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Dapcodinium
From Fensome et al., 2019:
Dapcodinium, Evitt, 1961a, p.996.
Emendations: Dörhöfer and Davies, 1980, p.23; Below, 1987a, p.141.
Taxonomic junior synonyms: Opaeopsomus, Mancodinium and Maturodinium, all according to Dörhöfer and Davies (1980, p.23) -- however, Lentin and Williams (1985, p.230–231) retained Mancodinium and Maturodinium.
Type: Evitt, 1961a, pl.119, figs.1–2; text-figs.10–11, as Dapcodinium priscus.
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Original description: [Evitt, 1961]: (Translation: Bureau of Translation, Secretary of State Canada, 1988, p. 361-363)
Diagnosis:
Thecate and distinctly tabulate Peridiniales with a tabulation of 4`, 4a, 7``, 6g, 6```, 2p, 1```` and a large ventral area, mostly on the epitheca. Rupture of the thecal wall appears to be by opening of sutures between plates in the apical region.
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Modified descriptions:
Stover and Evitt 1978, p. 36-37:
Synopsis:
Cysts proximate, generally subspherical; paratabulation indicated by low sutural ridges, formula: 4`, 4a, 7``, 6c, 7```, 2p, 1````; archeopyle formed apparently by rupture along sutures in apical area.
Description:
Shape: Subspherical with obtusely pointed apex.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges low, and at least distinct apically; autophragm smooth.
Paratabulation: Indicated by low parasutural ridges; formula: 4`, 4a, 7``, 6c, 7```, 2p, 1````; first postcingular paraplate incompletely outlined and not counted in formula as presented originally.
Archeopyle: Formed apparently by rupture along sutures in apical area, involving mainly apical paraplates, but also, in part, anterior intercalary paraplates, and followed by in-folding or wrinkling of partially detached paraplates.
Paracingulum: indicated by six rectangular paraplates.
Parasulcus: Relatively wide area confined mainly to hypocyst; faint parasutural features may be present.
Size: Small.
Affinities:
No similar-appearing small dinoflagellate cyst with a comparable paratabulation known.
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Emended descriptions:
Dörhöfer and Davies, 1980
Description:
Proximate dinoflagellate cysts with circular to ovoidal ambitus; apex occasionally slightly pointed. Tabulation is variably expressed (sutural crests, faint sutures, alignment of ornament): 4`, 4-5a, 7``, 6-7c, 6-7```, 1-4p, 1````. Disintegration archeopyle 4A + 4-5I + 7P initiating mid-dorsally between the apical and intercalary series. Ornament, if present, is low.
Affinities:
Pocock (1972: 96-97) vaguely described the new genus Opaeopsomus and attributed it to Evitt. Because the type species O. wapellensis Pocock 1972 falls within the diagnosis of Dapcodinium, it is here transferred. Opaeopsomus, therefore, becomes redundant. The disintegration archeopyle of Dapcodinium is apparent from our own observations, but was also illustrated by Evitt (1961, p. 100, text-fig. 12, 18-20, pl. 119, fig. 6). Slight differences in archeopyle development between Mancodinium and Maturodinium represent various stages of the disintegration archeopyle. Both "genera" were encountered in our arctic material. Besides minute differences regarding expressions of plate boundaries, they are identical in tabulation and overall morphology and appear synonymous with Dapcodinium.
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Below, 1987:
Description:
Arrangement of vesicles/plates of the dinoflagellate amphiesma PR, 5`, 4a-6a, 7``, 8c, 8```-7```-6```, 3````, ns; as connected dextrally only with 7``.
Cystic habit proximate, proximochorate, chorate, cavate, acavate, spheroidal, ovoidal, ovaloidal, ellipsoidal, polyhedral, with or without apical protuberances, of variable size; wall composed of pedium, also additional luxuria, surface smooth or ornamented, areate or nonareate; areation marked by finate ornaments or limbi, areation formula NR PR/PR, NR`/5`, NRa/4a-6a, NR``/7``, NRc/8c, NR```/8```-7```-6```, NR````/3````, NRs/ns/as, y, z, ps; archeopyle apical and anterior intercalary, PR + 2` + 3` + 4` + 1a + 2a + 3a + 4a or 3` + 4` + 2a + 3a; operculum solvate, secate, general opercular formula PRs + s`s + 3`s + 4`s + 1as + 2as + 3as + 4as or 3`s + 4`s + 2as + 3as or mediodorsal pylome.
Affinities:
Compared to the original diagnosis, the emendation is justified by the number and especially the arrangement of the apical and intercalary areas. Because of the different coding (1```` corresponds to Evitt`s [1961] 2```) also the number of postcingular areae is increased to seven in all. This applies also to the cingulum with eight areae. The type of thecal-plate growth has not yet been determined for any species, because growth structures are not reflected on the cysts investigated for this study. The emendation by Dörhöfer and Davies (1980) is rejected. The alleged variation of anterior intercalaries, cingulars, postcingulars, and posterior intercalaries could not be verified. But more importantly, Dapcodinium does not form an epicystal archeopyle. Consequently, Mancodinium Morgenroth, 1970 and Maturodinium Morgenroth, 1970, which do form epicystal exit holes, are maintained, in opposition to the view of Dörhöfer and Davies (1980), as independent genera in the family Cladopyxiaceae. They also show a completely different areation. The synonymy of the genus Opaeopsomus Pocock, 1972 is not given at least with Dapcodinium. Therefore all new combinations proposed by Dörhöfer and Davies (1980) are rejected.
Dapcodinium, Evitt, 1961a, p.996.
Emendations: Dörhöfer and Davies, 1980, p.23; Below, 1987a, p.141.
Taxonomic junior synonyms: Opaeopsomus, Mancodinium and Maturodinium, all according to Dörhöfer and Davies (1980, p.23) -- however, Lentin and Williams (1985, p.230–231) retained Mancodinium and Maturodinium.
Type: Evitt, 1961a, pl.119, figs.1–2; text-figs.10–11, as Dapcodinium priscus.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Evitt, 1961]: (Translation: Bureau of Translation, Secretary of State Canada, 1988, p. 361-363)
Diagnosis:
Thecate and distinctly tabulate Peridiniales with a tabulation of 4`, 4a, 7``, 6g, 6```, 2p, 1```` and a large ventral area, mostly on the epitheca. Rupture of the thecal wall appears to be by opening of sutures between plates in the apical region.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified descriptions:
Stover and Evitt 1978, p. 36-37:
Synopsis:
Cysts proximate, generally subspherical; paratabulation indicated by low sutural ridges, formula: 4`, 4a, 7``, 6c, 7```, 2p, 1````; archeopyle formed apparently by rupture along sutures in apical area.
Description:
Shape: Subspherical with obtusely pointed apex.
Wall relationships: Autophragm only.
Wall features: Parasutural ridges low, and at least distinct apically; autophragm smooth.
Paratabulation: Indicated by low parasutural ridges; formula: 4`, 4a, 7``, 6c, 7```, 2p, 1````; first postcingular paraplate incompletely outlined and not counted in formula as presented originally.
Archeopyle: Formed apparently by rupture along sutures in apical area, involving mainly apical paraplates, but also, in part, anterior intercalary paraplates, and followed by in-folding or wrinkling of partially detached paraplates.
Paracingulum: indicated by six rectangular paraplates.
Parasulcus: Relatively wide area confined mainly to hypocyst; faint parasutural features may be present.
Size: Small.
Affinities:
No similar-appearing small dinoflagellate cyst with a comparable paratabulation known.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Dörhöfer and Davies, 1980
Description:
Proximate dinoflagellate cysts with circular to ovoidal ambitus; apex occasionally slightly pointed. Tabulation is variably expressed (sutural crests, faint sutures, alignment of ornament): 4`, 4-5a, 7``, 6-7c, 6-7```, 1-4p, 1````. Disintegration archeopyle 4A + 4-5I + 7P initiating mid-dorsally between the apical and intercalary series. Ornament, if present, is low.
Affinities:
Pocock (1972: 96-97) vaguely described the new genus Opaeopsomus and attributed it to Evitt. Because the type species O. wapellensis Pocock 1972 falls within the diagnosis of Dapcodinium, it is here transferred. Opaeopsomus, therefore, becomes redundant. The disintegration archeopyle of Dapcodinium is apparent from our own observations, but was also illustrated by Evitt (1961, p. 100, text-fig. 12, 18-20, pl. 119, fig. 6). Slight differences in archeopyle development between Mancodinium and Maturodinium represent various stages of the disintegration archeopyle. Both "genera" were encountered in our arctic material. Besides minute differences regarding expressions of plate boundaries, they are identical in tabulation and overall morphology and appear synonymous with Dapcodinium.
-----------------------------------------
Below, 1987:
Description:
Arrangement of vesicles/plates of the dinoflagellate amphiesma PR, 5`, 4a-6a, 7``, 8c, 8```-7```-6```, 3````, ns; as connected dextrally only with 7``.
Cystic habit proximate, proximochorate, chorate, cavate, acavate, spheroidal, ovoidal, ovaloidal, ellipsoidal, polyhedral, with or without apical protuberances, of variable size; wall composed of pedium, also additional luxuria, surface smooth or ornamented, areate or nonareate; areation marked by finate ornaments or limbi, areation formula NR PR/PR, NR`/5`, NRa/4a-6a, NR``/7``, NRc/8c, NR```/8```-7```-6```, NR````/3````, NRs/ns/as, y, z, ps; archeopyle apical and anterior intercalary, PR + 2` + 3` + 4` + 1a + 2a + 3a + 4a or 3` + 4` + 2a + 3a; operculum solvate, secate, general opercular formula PRs + s`s + 3`s + 4`s + 1as + 2as + 3as + 4as or 3`s + 4`s + 2as + 3as or mediodorsal pylome.
Affinities:
Compared to the original diagnosis, the emendation is justified by the number and especially the arrangement of the apical and intercalary areas. Because of the different coding (1```` corresponds to Evitt`s [1961] 2```) also the number of postcingular areae is increased to seven in all. This applies also to the cingulum with eight areae. The type of thecal-plate growth has not yet been determined for any species, because growth structures are not reflected on the cysts investigated for this study. The emendation by Dörhöfer and Davies (1980) is rejected. The alleged variation of anterior intercalaries, cingulars, postcingulars, and posterior intercalaries could not be verified. But more importantly, Dapcodinium does not form an epicystal archeopyle. Consequently, Mancodinium Morgenroth, 1970 and Maturodinium Morgenroth, 1970, which do form epicystal exit holes, are maintained, in opposition to the view of Dörhöfer and Davies (1980), as independent genera in the family Cladopyxiaceae. They also show a completely different areation. The synonymy of the genus Opaeopsomus Pocock, 1972 is not given at least with Dapcodinium. Therefore all new combinations proposed by Dörhöfer and Davies (1980) are rejected.