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Apteodinium monacanthum
Apteodinium monacanthum, (Deflandre, 1935), Helenes, 1984
Originally Palaeoperidinium, subsequently Gonyaulacysta, thirdly Millioudodinium, fourthly (and now) Apteodinium. Questionable assignment: Jan du Chêne et al. (1986a, p.48), as a problematic species.
Jan du Chêne et al. (1986a, p.48) recommended that the name be restricted to the holotype.
The name Palaeoperidinium monacanthum was not validly published in Deflandre (1935) since the generic name Palaeoperidinium was not validly published until 1967. Williams et al. (1998, p.49) accepted Sarjeant's (1967b) indirect reference to Deflandre (1935) as indication of a type (I.C.N. Article 40.1)
Holotype: Deflandre, 1935, pl.6, fig.1; Deflandre, 1936b, pl.5, fig.10; lost according to Jan du Chêne et al. (1986a, p.48).
Age: Senonian
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Original description: [Sarjeant, 1967]:
Description:
Based on a single specimen. Shell almost ellipsoidal, with a strongly marked apical horn (placed antapically in Deflandre's figure).
Cingulum modernly broad, laevo-rotatory: sulcus also broad, running from apex to antapex.
Cingulum and sulcus edged by well-marked crests: sutures between plates less well marked.
Tabulation not determined in detail.
Dimensions:
Overall length 112 μm, breadth 88 μm.
Affinities/Remarks:
In size and proportions and in what little can be seen of the tabulation, the holotype resembles closely several Lower and Middle Cretaceous species of the genera Gonyaulacysta Deflandre 1965 emend. Sarjeant, 1966, and Cribroperidinium Neale and Sarjeant 1962, emend. Davey, 1967. The position of the horn must certainly be taken as apical: the relatively flattened form of the antapex then suggests the presence of a single antapical plate, indicating an affinity to the former, rather than to the latter, genus. This condition agrees with Deflandre's earlier suggestion of an affinity to Gonyaulax (1036 c, p. 176). It is therefore proposed that this species be re-designated Gonyaulacysta monacantha (Delfandre, 1035a), comb. nov.
Originally Palaeoperidinium, subsequently Gonyaulacysta, thirdly Millioudodinium, fourthly (and now) Apteodinium. Questionable assignment: Jan du Chêne et al. (1986a, p.48), as a problematic species.
Jan du Chêne et al. (1986a, p.48) recommended that the name be restricted to the holotype.
The name Palaeoperidinium monacanthum was not validly published in Deflandre (1935) since the generic name Palaeoperidinium was not validly published until 1967. Williams et al. (1998, p.49) accepted Sarjeant's (1967b) indirect reference to Deflandre (1935) as indication of a type (I.C.N. Article 40.1)
Holotype: Deflandre, 1935, pl.6, fig.1; Deflandre, 1936b, pl.5, fig.10; lost according to Jan du Chêne et al. (1986a, p.48).
Age: Senonian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Sarjeant, 1967]:
Description:
Based on a single specimen. Shell almost ellipsoidal, with a strongly marked apical horn (placed antapically in Deflandre's figure).
Cingulum modernly broad, laevo-rotatory: sulcus also broad, running from apex to antapex.
Cingulum and sulcus edged by well-marked crests: sutures between plates less well marked.
Tabulation not determined in detail.
Dimensions:
Overall length 112 μm, breadth 88 μm.
Affinities/Remarks:
In size and proportions and in what little can be seen of the tabulation, the holotype resembles closely several Lower and Middle Cretaceous species of the genera Gonyaulacysta Deflandre 1965 emend. Sarjeant, 1966, and Cribroperidinium Neale and Sarjeant 1962, emend. Davey, 1967. The position of the horn must certainly be taken as apical: the relatively flattened form of the antapex then suggests the presence of a single antapical plate, indicating an affinity to the former, rather than to the latter, genus. This condition agrees with Deflandre's earlier suggestion of an affinity to Gonyaulax (1036 c, p. 176). It is therefore proposed that this species be re-designated Gonyaulacysta monacantha (Delfandre, 1035a), comb. nov.