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Diconodinium multispinum
Diconodinium multispinum (Deflandre and Cookson, 1955) Eisenack and Cookson, 1960; emend. Morgan, 1977
Originally Palaeohystrichophora, subsequently (and now) Diconodinium.
Taxonomic junior synonyms: Palaeohystrichophora (as Diconodinium) dispersa, according to Stover and Helby (1987a, p.103); Diconodinium pusillum, according to Morgan (1977, p.127) - however, Below (1981a, p.124) retained Diconodinium pusillum.
Holotype: Deflandre and Cookson, 1955, pl.1, fig.5; Morgan, 1977, pl.1, figs.1a-b
Locus typicus: Gingin, W Australia
Stratum typicum: Santonian
Original description: Deflandre and Cookson, 1955, p.257: Palaeohystrichophora multispina
Theca biconical with an approximately median, straight, probably helicoidal girdle. The portion taken as the epitheca is terminated by a short truncate process, the hypotheca being prolonged into a short, stout point. The membrane, which shows no trace of plates, is entirely covered with short spines.
Dimensions: Length 56 µm, breadth 38 µm.
Extended diagnosis: Cookson and Eisenack, 1958, p. 38: Palaeohystrichophora multispina
The theca is broadly fusiform and has straight to convex sides; the "epitheca" is terminated by a shortly bifid process and the "hypotheca" by a sharply pointed spine. The transverse furrow is approximately equatorial but is covered by short, fine spines which are sometimes so small as to give the surface a granular appearence.
Dimensions: Range in new material 62-100x43-71 µm.
Emended description: Morgan, 1977, p. 127-128
Ambitus rhomboidal to fusiform, prolonged into a truncate apical horn of variable length, and into a single, sharp antapical horn located close to the midline. Epicyst and hypocyst of approximately equal size, or hypocyst slightly larger.
Apparent autophragm mostly thin, but may thicken to form wholly or partly solid apical and antapical horns. Surface densely covered with ornamentation, which is homogeneous on individual specimens but in populations varies from fine granules to 1.0 µm long weakly capitate spines. Paratabulation may be weakly discernible over the cyst, especially the epicyst, by slightly larger parasutural ornamentation, or fusing of adjacent ornamentation elements to form discontinuous parasutural ridges (Pl. 1, figs. 6, 8). Paracingulum defined by two slightly raised ridges bearing aligned ornamentation, individual paraplates not discernible. Parasulcus may be incompletely outlined by larger parasutural ornamentation, individual paraplates not discernible. Archeopyle la or IPa.
Dimensions: 40-100 µm long and 28-71 µm broad.
Affinities:
Morgan, 1977, p. 128: Ornamentation ranging from fine granules to 1.0µm long weakly capitate spines is characteristic of D. multispinum. For discussion of other species, see treatment of D. arcticum.
Originally Palaeohystrichophora, subsequently (and now) Diconodinium.
Taxonomic junior synonyms: Palaeohystrichophora (as Diconodinium) dispersa, according to Stover and Helby (1987a, p.103); Diconodinium pusillum, according to Morgan (1977, p.127) - however, Below (1981a, p.124) retained Diconodinium pusillum.
Holotype: Deflandre and Cookson, 1955, pl.1, fig.5; Morgan, 1977, pl.1, figs.1a-b
Locus typicus: Gingin, W Australia
Stratum typicum: Santonian
Original description: Deflandre and Cookson, 1955, p.257: Palaeohystrichophora multispina
Theca biconical with an approximately median, straight, probably helicoidal girdle. The portion taken as the epitheca is terminated by a short truncate process, the hypotheca being prolonged into a short, stout point. The membrane, which shows no trace of plates, is entirely covered with short spines.
Dimensions: Length 56 µm, breadth 38 µm.
Extended diagnosis: Cookson and Eisenack, 1958, p. 38: Palaeohystrichophora multispina
The theca is broadly fusiform and has straight to convex sides; the "epitheca" is terminated by a shortly bifid process and the "hypotheca" by a sharply pointed spine. The transverse furrow is approximately equatorial but is covered by short, fine spines which are sometimes so small as to give the surface a granular appearence.
Dimensions: Range in new material 62-100x43-71 µm.
Emended description: Morgan, 1977, p. 127-128
Ambitus rhomboidal to fusiform, prolonged into a truncate apical horn of variable length, and into a single, sharp antapical horn located close to the midline. Epicyst and hypocyst of approximately equal size, or hypocyst slightly larger.
Apparent autophragm mostly thin, but may thicken to form wholly or partly solid apical and antapical horns. Surface densely covered with ornamentation, which is homogeneous on individual specimens but in populations varies from fine granules to 1.0 µm long weakly capitate spines. Paratabulation may be weakly discernible over the cyst, especially the epicyst, by slightly larger parasutural ornamentation, or fusing of adjacent ornamentation elements to form discontinuous parasutural ridges (Pl. 1, figs. 6, 8). Paracingulum defined by two slightly raised ridges bearing aligned ornamentation, individual paraplates not discernible. Parasulcus may be incompletely outlined by larger parasutural ornamentation, individual paraplates not discernible. Archeopyle la or IPa.
Dimensions: 40-100 µm long and 28-71 µm broad.
Affinities:
Morgan, 1977, p. 128: Ornamentation ranging from fine granules to 1.0µm long weakly capitate spines is characteristic of D. multispinum. For discussion of other species, see treatment of D. arcticum.