Back
Ynezidinium
From Williams et al., 2017:
[Ynezidinium, Lucas-Clark and Helenes, 2000, p. 114-115.
Type species: Ynezidinium malloyii, Lucas-Clark and Helenes, 2000 (pl.1, figs.1-3)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Lucas-Clark and Helenes, 2000]:
Diagnosis:
Medium size, acavate cysts with parasutural ridges; from spherical to ellipsoidal; circular to ovoidal (dorso-ventrally compressed) in equatorial section; with or without an apical horn. Intratabular areas smooth or with sparse ornamentation of low relief.
Paratabulation gonyaulacacean, 1i/1u, Q/B.
Archeopyle precingular, type P(4); operculum typically reduced, rounded free.
Paratabulation: Indicated by parasutural septa or ridges, usually clear except in sulcal and preapical regions, where parasutural ridges may be absent or reduced. The following paraplates can be observed in most specimens; two preapicals (Q, P), four apicals (A, 1U, B, C), six precingulars (1i, 2-6), six cingulars (au, b-e, fi), two sulcals (ai and Z), one posterior intercalary (X), six postcingulars (Iu, II-VI), and one antapical (Y).
Apical organization: Preapicals sometimes indistinct but, when discernible, Q contacts all four apical paraplates; P contacts Q, B and 1u (Q/B arrangement). Porichnion may be discernable. Dorsal apicals (b and C) wide and quadrangular; ventral apicals (a and 1u) elongate, subparallel, and more or less centered on the ventral side of the cyst. Paraplate A slightly smaller than 1u and separated from this paraplate by a complete or nearly complete septum.
Ventral organization: Paraplates A and 1u contact 1i (1u/1i arrangement), which is pentagonal and may be smaller than other precingulares. Ends of the cingulum offset, not overlapping.
Posterior sulcal organization: pentagonal X, nearly square Z, elongate, rectangular Iu. Sulcal region elongate and at least slightly sigmoidal; some suppression of parasutures confined to the sulcal and preapical regions.
Dorsal organization: Archeopyle usually reduced. Neutral torsion of the hypocyst indicated. Without incidentals or small (K) intercalaries. Hypocystal organization: sexiform, Y slightly asymmetrical with X/Y and III/Y shorter than VI/Y and V/Y respectively. Y positioned antapically or displaced onto the ventrum.
[Ynezidinium, Lucas-Clark and Helenes, 2000, p. 114-115.
Type species: Ynezidinium malloyii, Lucas-Clark and Helenes, 2000 (pl.1, figs.1-3)]
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Lucas-Clark and Helenes, 2000]:
Diagnosis:
Medium size, acavate cysts with parasutural ridges; from spherical to ellipsoidal; circular to ovoidal (dorso-ventrally compressed) in equatorial section; with or without an apical horn. Intratabular areas smooth or with sparse ornamentation of low relief.
Paratabulation gonyaulacacean, 1i/1u, Q/B.
Archeopyle precingular, type P(4); operculum typically reduced, rounded free.
Paratabulation: Indicated by parasutural septa or ridges, usually clear except in sulcal and preapical regions, where parasutural ridges may be absent or reduced. The following paraplates can be observed in most specimens; two preapicals (Q, P), four apicals (A, 1U, B, C), six precingulars (1i, 2-6), six cingulars (au, b-e, fi), two sulcals (ai and Z), one posterior intercalary (X), six postcingulars (Iu, II-VI), and one antapical (Y).
Apical organization: Preapicals sometimes indistinct but, when discernible, Q contacts all four apical paraplates; P contacts Q, B and 1u (Q/B arrangement). Porichnion may be discernable. Dorsal apicals (b and C) wide and quadrangular; ventral apicals (a and 1u) elongate, subparallel, and more or less centered on the ventral side of the cyst. Paraplate A slightly smaller than 1u and separated from this paraplate by a complete or nearly complete septum.
Ventral organization: Paraplates A and 1u contact 1i (1u/1i arrangement), which is pentagonal and may be smaller than other precingulares. Ends of the cingulum offset, not overlapping.
Posterior sulcal organization: pentagonal X, nearly square Z, elongate, rectangular Iu. Sulcal region elongate and at least slightly sigmoidal; some suppression of parasutures confined to the sulcal and preapical regions.
Dorsal organization: Archeopyle usually reduced. Neutral torsion of the hypocyst indicated. Without incidentals or small (K) intercalaries. Hypocystal organization: sexiform, Y slightly asymmetrical with X/Y and III/Y shorter than VI/Y and V/Y respectively. Y positioned antapically or displaced onto the ventrum.