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Diconodinium cristatum
Diconodinium cristatum Cookson and Eisenack, 1974; emend. Morgan, 1977
Holotype: Cookson and Eisenack, 1974, pl.24, fig.3
Locus typicus: Moora Bore, Gingin, Australia
Stratum typicum: Albian-Cenomanian
Translation Cookson and Eisenack, 1974: GSC, courtesy R. Fensome
Original diagnosis: Cookson and Eisenack, 1974, p.77
A Diconodinium the antapex of which, at about half the length of the antapical spine, bears a sharp list (crista), which slants toward the left (ventral [side on] top) and which, after a short stretch, becomes confluent with the left edge or ridge of the ventral area.
Number of available specimens and dimensions: More than 12 specimens (8 of which were measured). Type: 90x42 Ám. The length of the remaining specimens lies between 76 and 104 Ám, the breadth approximately between 40 and 60 Ám.
Age and occurrence: Moora bore, at 86-170 ft. (frequent) and in Balcatta bore at 170 ft. (2 specimens) [age not given].
Emended description: Morgan, 1977, p. 126
Ambitus rhomboidal to fusiform, prolonged into a truncate apical horn and a sharp antapical horn located close to the midline. Apparent autophragm mostly thin, but distinctly thickened at the apex (forming a partly or wholly solid apical horn) and at the antapex (forming a distinctive solid "keel" 2-3 Ám deep along its entire length and extending from the solid sharp antapical horn to the bulge of the undeveloped second antapical horn, as in Pl. 1, fig. 3). Ornamentation absent, or consisting of granules or spinules, usually uniform in size on individual specimens. Slightly longer aligned spines may incompletely reflect paratabulation on the cyst. Slightly raised parasutural ridges and aligned ornamentation outline the paracingulum and parasulcus (see Pl. 1, fig. 3), but individual paraplates not yet distinguished. Archeopyle la or (IP)a.
Dimensions: 76-104 Ám long and 40-60 Ám broad.
Affinities:
Cookson and Eisenack, 1974, p.77
The species is closely related to the D. ,glabrum with which it can be easily confused if, in the case of slanted position, the list can not be recognised. As in the case of the D. glabrum, the envelope is very delicate and occasionally folded; at times it bears more or less distinct small punctae which can be arranged in form of longitudinal rows.
The antapical spine is slightly shifted toward the right side and, at the antapex, the boundary of the internal area is of a rounded form.
Morgan, 1977, p. 126: The antapical thickening of the autophragm distinguishes D. cristatum from other Diconodinium species. For a more detailed discussion. see treatment of D. arcticum.
Holotype: Cookson and Eisenack, 1974, pl.24, fig.3
Locus typicus: Moora Bore, Gingin, Australia
Stratum typicum: Albian-Cenomanian
Translation Cookson and Eisenack, 1974: GSC, courtesy R. Fensome
Original diagnosis: Cookson and Eisenack, 1974, p.77
A Diconodinium the antapex of which, at about half the length of the antapical spine, bears a sharp list (crista), which slants toward the left (ventral [side on] top) and which, after a short stretch, becomes confluent with the left edge or ridge of the ventral area.
Number of available specimens and dimensions: More than 12 specimens (8 of which were measured). Type: 90x42 Ám. The length of the remaining specimens lies between 76 and 104 Ám, the breadth approximately between 40 and 60 Ám.
Age and occurrence: Moora bore, at 86-170 ft. (frequent) and in Balcatta bore at 170 ft. (2 specimens) [age not given].
Emended description: Morgan, 1977, p. 126
Ambitus rhomboidal to fusiform, prolonged into a truncate apical horn and a sharp antapical horn located close to the midline. Apparent autophragm mostly thin, but distinctly thickened at the apex (forming a partly or wholly solid apical horn) and at the antapex (forming a distinctive solid "keel" 2-3 Ám deep along its entire length and extending from the solid sharp antapical horn to the bulge of the undeveloped second antapical horn, as in Pl. 1, fig. 3). Ornamentation absent, or consisting of granules or spinules, usually uniform in size on individual specimens. Slightly longer aligned spines may incompletely reflect paratabulation on the cyst. Slightly raised parasutural ridges and aligned ornamentation outline the paracingulum and parasulcus (see Pl. 1, fig. 3), but individual paraplates not yet distinguished. Archeopyle la or (IP)a.
Dimensions: 76-104 Ám long and 40-60 Ám broad.
Affinities:
Cookson and Eisenack, 1974, p.77
The species is closely related to the D. ,glabrum with which it can be easily confused if, in the case of slanted position, the list can not be recognised. As in the case of the D. glabrum, the envelope is very delicate and occasionally folded; at times it bears more or less distinct small punctae which can be arranged in form of longitudinal rows.
The antapical spine is slightly shifted toward the right side and, at the antapex, the boundary of the internal area is of a rounded form.
Morgan, 1977, p. 126: The antapical thickening of the autophragm distinguishes D. cristatum from other Diconodinium species. For a more detailed discussion. see treatment of D. arcticum.