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Chichaouadinium davidii
Chichaouadinium davidii, (Morgan, 1975), Bujak and Davies, 1983
Now Diconodinium. Originally (and now) Diconodinium, subsequently Chichaouadinium.
Stover and Williams, 1987, retained this species in Diconodinium Eisenack and Cookson, 1960.
Holotype: Morgan, 1975, pl.1, figs.1a-b
Locus typicus: Great Australian Basin, Australia
Stratum typicum: Aptian-Albian
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Original description as Diconodinium davidii: [Morgan, 1975, p. 157-158]:
Description:
Cyst consists of a broadly subtriangular epitract bearing a long steeply conical, distally truncate apical horn, and a broadly rounded hypotract bearing a single strong, sharply pointed antapical horn slightly offset from the longitudinal axis.
The cingulum is about 5 µm wide, and offset slightly at the sulcus.
The autophragm bears a moderately dense cover of small solid spinulae or clavae about 1.0-1.5 µm high and about 1.0 µm thick. These are absent from the cingulum and rare on the sulcus area, but otherwise cover the entire autophragm. The spinulae or clavae may be randomly distributed but are more often, at least partly, aligned in rows to reveal traces of tabulation, and are always aligned in two rows along the margins of the cingulum. If aligned, the peritabular spinulae or clavae are larger and stouter than the intratabular ones. On some specimens, most of the clavae are peritabular with few or none intratabular.
The archeopyle is type (Ia) or (IPa). The former type results when only the lateral and apical sutures of the reflected 2a plate open, and the plate remains attached antapically to the 4" reflected plate. Commonly, the lateral sutures of plate 4"" at least partly open, so that the operculum consists of a single piece (comprising plates 2a and 4") that remains attached at, or close to, the cingulum.
Dimensions:
72(83)96 µm long and 41(50)57 µm broad (10 specimens measured).
Affinities: (p. 158-159):
This species is similar to Diconodinium arcticum Manum and Cookson which has shorter horns, less dense and finer ornament (minute granules up to 0-5 µm in diameter rather than spinulae or clavae 1.0-1.5 µm high and about 1 µm in diameter) and is smaller (50-73 µm long, 32-53 µm broad rather than 12-96 µm long and 41-57 µm broad). D. pusillum Singh (1971) differs from the new species by having shorter horns, finer, sharply pointed spines 0.5 µm long and by being smaller (40(47)54 µm long and 28(36.5)43 µm broad). D. firmum Harland (1973) can be distinguished by its small size (36.0(42.7)50.0 µm long and 18.0(29.3)30 µm broad), solid (not hollow) apical horn, fine granulation (no size given), thin wall and broad cingulum. A precingular archeopyle may be present in D. firmum. Diconodinium pelliferum (Cookson and Eisenack, 1958) (85 µm long and 59 µm broad) and Diconodinium dispersum (Cookson and Eisenack, 1958) (64-90 µm long and 38-62 µm broad) are similar in size to D. davidii (72-96 µm long and 41-57 µm broad). Surface ornament in D. pelliferum consists of long (1.0-2.5 µm) sharply pointed spines, and in D. dispersum of long (2.0-3.0 µm) strongly capitate spines, while the new species has blunt non-capitate spinulae or clavae (1.0-1.5 µm long).
Now Diconodinium. Originally (and now) Diconodinium, subsequently Chichaouadinium.
Stover and Williams, 1987, retained this species in Diconodinium Eisenack and Cookson, 1960.
Holotype: Morgan, 1975, pl.1, figs.1a-b
Locus typicus: Great Australian Basin, Australia
Stratum typicum: Aptian-Albian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Diconodinium davidii: [Morgan, 1975, p. 157-158]:
Description:
Cyst consists of a broadly subtriangular epitract bearing a long steeply conical, distally truncate apical horn, and a broadly rounded hypotract bearing a single strong, sharply pointed antapical horn slightly offset from the longitudinal axis.
The cingulum is about 5 µm wide, and offset slightly at the sulcus.
The autophragm bears a moderately dense cover of small solid spinulae or clavae about 1.0-1.5 µm high and about 1.0 µm thick. These are absent from the cingulum and rare on the sulcus area, but otherwise cover the entire autophragm. The spinulae or clavae may be randomly distributed but are more often, at least partly, aligned in rows to reveal traces of tabulation, and are always aligned in two rows along the margins of the cingulum. If aligned, the peritabular spinulae or clavae are larger and stouter than the intratabular ones. On some specimens, most of the clavae are peritabular with few or none intratabular.
The archeopyle is type (Ia) or (IPa). The former type results when only the lateral and apical sutures of the reflected 2a plate open, and the plate remains attached antapically to the 4" reflected plate. Commonly, the lateral sutures of plate 4"" at least partly open, so that the operculum consists of a single piece (comprising plates 2a and 4") that remains attached at, or close to, the cingulum.
Dimensions:
72(83)96 µm long and 41(50)57 µm broad (10 specimens measured).
Affinities: (p. 158-159):
This species is similar to Diconodinium arcticum Manum and Cookson which has shorter horns, less dense and finer ornament (minute granules up to 0-5 µm in diameter rather than spinulae or clavae 1.0-1.5 µm high and about 1 µm in diameter) and is smaller (50-73 µm long, 32-53 µm broad rather than 12-96 µm long and 41-57 µm broad). D. pusillum Singh (1971) differs from the new species by having shorter horns, finer, sharply pointed spines 0.5 µm long and by being smaller (40(47)54 µm long and 28(36.5)43 µm broad). D. firmum Harland (1973) can be distinguished by its small size (36.0(42.7)50.0 µm long and 18.0(29.3)30 µm broad), solid (not hollow) apical horn, fine granulation (no size given), thin wall and broad cingulum. A precingular archeopyle may be present in D. firmum. Diconodinium pelliferum (Cookson and Eisenack, 1958) (85 µm long and 59 µm broad) and Diconodinium dispersum (Cookson and Eisenack, 1958) (64-90 µm long and 38-62 µm broad) are similar in size to D. davidii (72-96 µm long and 41-57 µm broad). Surface ornament in D. pelliferum consists of long (1.0-2.5 µm) sharply pointed spines, and in D. dispersum of long (2.0-3.0 µm) strongly capitate spines, while the new species has blunt non-capitate spinulae or clavae (1.0-1.5 µm long).