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Millioudodinium birkelundii
Millioudodinium birkelundii (Fensome, 1979) Lentin and Williams, 1981
Now Cribroperidinium?. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium?.
Holotype: Fensome, 1979, pl.5, figs.5,8,11, text-figs.14A-B; Jan du Chêne et al., 1986, pl.24, figs. 1-3
Locus typicus: Aucellaelv, Greenland
Stratum typicum: Portlandian
Original diagnosis: Fensome, 1979, p. 38: Gonyaulacysta birkelundii
A species of Gonyaulacysta with an ovoidal ambitus. The apical horn is distinctly differentiated from the rest of the cyst; it is usually narrow and of variable length. The cyst wall is composed of two layers closely appressed over the whole surface. It is granular and possesses numerous irregularly distributed short spines.
Parasutures are marked by spinose thickenings of the cyst wall or by ragged, irregularly shaped crests. They mark a paratabulation of 4", ?1a, 6", ?c, 7""", 1p, 1"""", 6+s. The paracingulum is weakly laevorotatory. The parasulcus is broad and straight. situated principally on the hypocyst; it is sparsely ornamented and is subdivided into several small paraplates. The archeopyle is precingular. formed by the loss of paraplate 3", the operculum typically being detached.
Dimensions: Holotype; length 91 Ám, breadth 69 Ám, Iength of apical horn 14 Ám. Range; length 74 (83) 91 Ám, breadth 51 (63) 69 Ám, length of apical horn 14 (19) 33 Ám.
Original description: Fensome, 1979, p. 38-40: Gonyaulacysta birkelundii
A species of dinoflagellate with a usually subovoidal, dorso-ventrally compressed cyst, surmounted by a distinct apical horn which varies from one seventh to one third of the overall cyst length (see fig. 14 c). The spine cover appears to be less dense on the ventral surface than on the dorsal surface, and is almost totally absent from the parasulcus. The parasutures are less clearly marked on the ventral surface; they are especially difficult to perceive towards the margins of the cyst because of the combined effects of spine cover and oblique orientation of the wall as presented to the viewer. In plan view the spines, because of their broad bases, often resemble verrucae. The parasutures are marked by thickenings of the cyst wall surmounted by low ragged crests. by rows of spines slightly longer than those of the general ornament or by linear zones of such spines. There are four apical paraplates of which 1" is elongate, extending from the horn towards the parasulcus. Paraplates 2" and 3" also extend to the distal tip of the horn but 4" impinges only onto the base of the horn. A possible small anterior intercalary paraplate at the anterior end of 6" was present on the holotype, but was not seen with certainty on any other specimen. There are six precingular paraplates, of which 6" is slightly smaller than the others. Paraplate 3" is usually lost in archeopyle formation.
The paracingulum is narrow, laevorotatory, its ends being displaced at the parasulcus by approximately one paracingulum width. Parasutures within the paracingulum are rarely clearly visible, especially on the dorsal surface, but there appear to be at least five paraplates present. The parasulcus is depressed; it is subdivided into at least five paraplates, including one large paraplate on the epicyst. The central part of the parasulcus is depressed relative to the rest of the parasulcus; this area usually possesses two flagellar markings which may develop into grooves. There are seven postcingular paraplates, paraplate 1""" being small and projecting into the parasulcus beyond the end of the paracingulum. Paraplate 2""" is also small, but larger than 1""".Parasutures on the dorsal surface of the hypocyst are indistinct, but there appear to be four large postcingular paraplates (3""" to 6""") on the dorsal and lateral surfaces. Ventrally situated paraplate 7""" is smaller than these but significantly larger than 1""" and 2""". There is a single, pentagonal, elongate posterior intercalary paraplate inserted between 1""", 2""" ,3""" and the parasulcus. The structure of the antapex is not clear, but it appears that at least one antapical paraplate is present.
Affinities:
Fensome, 1979, p. 40: Gonyaulacysta birkelundii
Although G. birkelundii possesses a general spine cover, the presence of a strong apical horn and the nature of its parasutures indicate that it is more allied with the genus Gonyaulacysta than with Acanrhaulax Sarjeant, 1968. A combination of a distinct apical horn, a general spine cover and a characteristic paratabulation distinguishes G. birkelundii from most other forms of Gonyaulacysta and Acanthaulax. Most similar is Gonyaulacysta sp. A of Gitmez & Sarjeant, 1972; this form has a similar shape and paratabulation, especially in the shape of paraplates 1""", 2""", 1p and 4" (1a of Gitmez & Sarjeant). However, the spines of the generalc ornament of Gonyaulacysta sp. A are much sparser than those of G. birkelundii. Nevertheless, these two taxa appear to be closely related.
Now Cribroperidinium?. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly (and now) Cribroperidinium?.
Holotype: Fensome, 1979, pl.5, figs.5,8,11, text-figs.14A-B; Jan du Chêne et al., 1986, pl.24, figs. 1-3
Locus typicus: Aucellaelv, Greenland
Stratum typicum: Portlandian
Original diagnosis: Fensome, 1979, p. 38: Gonyaulacysta birkelundii
A species of Gonyaulacysta with an ovoidal ambitus. The apical horn is distinctly differentiated from the rest of the cyst; it is usually narrow and of variable length. The cyst wall is composed of two layers closely appressed over the whole surface. It is granular and possesses numerous irregularly distributed short spines.
Parasutures are marked by spinose thickenings of the cyst wall or by ragged, irregularly shaped crests. They mark a paratabulation of 4", ?1a, 6", ?c, 7""", 1p, 1"""", 6+s. The paracingulum is weakly laevorotatory. The parasulcus is broad and straight. situated principally on the hypocyst; it is sparsely ornamented and is subdivided into several small paraplates. The archeopyle is precingular. formed by the loss of paraplate 3", the operculum typically being detached.
Dimensions: Holotype; length 91 Ám, breadth 69 Ám, Iength of apical horn 14 Ám. Range; length 74 (83) 91 Ám, breadth 51 (63) 69 Ám, length of apical horn 14 (19) 33 Ám.
Original description: Fensome, 1979, p. 38-40: Gonyaulacysta birkelundii
A species of dinoflagellate with a usually subovoidal, dorso-ventrally compressed cyst, surmounted by a distinct apical horn which varies from one seventh to one third of the overall cyst length (see fig. 14 c). The spine cover appears to be less dense on the ventral surface than on the dorsal surface, and is almost totally absent from the parasulcus. The parasutures are less clearly marked on the ventral surface; they are especially difficult to perceive towards the margins of the cyst because of the combined effects of spine cover and oblique orientation of the wall as presented to the viewer. In plan view the spines, because of their broad bases, often resemble verrucae. The parasutures are marked by thickenings of the cyst wall surmounted by low ragged crests. by rows of spines slightly longer than those of the general ornament or by linear zones of such spines. There are four apical paraplates of which 1" is elongate, extending from the horn towards the parasulcus. Paraplates 2" and 3" also extend to the distal tip of the horn but 4" impinges only onto the base of the horn. A possible small anterior intercalary paraplate at the anterior end of 6" was present on the holotype, but was not seen with certainty on any other specimen. There are six precingular paraplates, of which 6" is slightly smaller than the others. Paraplate 3" is usually lost in archeopyle formation.
The paracingulum is narrow, laevorotatory, its ends being displaced at the parasulcus by approximately one paracingulum width. Parasutures within the paracingulum are rarely clearly visible, especially on the dorsal surface, but there appear to be at least five paraplates present. The parasulcus is depressed; it is subdivided into at least five paraplates, including one large paraplate on the epicyst. The central part of the parasulcus is depressed relative to the rest of the parasulcus; this area usually possesses two flagellar markings which may develop into grooves. There are seven postcingular paraplates, paraplate 1""" being small and projecting into the parasulcus beyond the end of the paracingulum. Paraplate 2""" is also small, but larger than 1""".Parasutures on the dorsal surface of the hypocyst are indistinct, but there appear to be four large postcingular paraplates (3""" to 6""") on the dorsal and lateral surfaces. Ventrally situated paraplate 7""" is smaller than these but significantly larger than 1""" and 2""". There is a single, pentagonal, elongate posterior intercalary paraplate inserted between 1""", 2""" ,3""" and the parasulcus. The structure of the antapex is not clear, but it appears that at least one antapical paraplate is present.
Affinities:
Fensome, 1979, p. 40: Gonyaulacysta birkelundii
Although G. birkelundii possesses a general spine cover, the presence of a strong apical horn and the nature of its parasutures indicate that it is more allied with the genus Gonyaulacysta than with Acanrhaulax Sarjeant, 1968. A combination of a distinct apical horn, a general spine cover and a characteristic paratabulation distinguishes G. birkelundii from most other forms of Gonyaulacysta and Acanthaulax. Most similar is Gonyaulacysta sp. A of Gitmez & Sarjeant, 1972; this form has a similar shape and paratabulation, especially in the shape of paraplates 1""", 2""", 1p and 4" (1a of Gitmez & Sarjeant). However, the spines of the generalc ornament of Gonyaulacysta sp. A are much sparser than those of G. birkelundii. Nevertheless, these two taxa appear to be closely related.