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Octodinium askiniae
Octodinium askiniae Wrenn and Hart, 1988
Holotype: Wrenn and Hart, 1988, fig.29, no.5.
Locus typicus: Seymour Island, Antarctica
Stratum typicum: Eocene
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Octodinium askiniae Wrenn and Hart, 1988, is a subelliptical to subtriangular cornucavate peridinioid cyst with a combination archeopyle, resulting from the loss of 2a, which may be partly or completely detached, and the 4", which is adnate. The 2a is eight-sided. The single apical and two equal antapical horns are long and tapering. The periphragm is smooth, granular or rugulate. Length is
44-57 µm.
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Original diagnosis: Wrenn and Hart, 1988, p.359
A species of Octodinium characterized by long tapering apical and antapical horns and periphragm ornamentation consisting of grana or rugulae.
Original description: Wrenn and Hart, 1988, p.360
Shape: The cornucavate cysts vary in outline from subelliptical to subtriangular. Subelliptical cysts are widest in the paracingular area, whereas subtriangular specimens are as wide or wider antapically than they are in the paracingular region. The cysts are convex between the apical and antapical horns, and straight to convave between the two antapical horns. Relatively long apical and antapical horns arise from the three comers of the central body.
Phragma: The periphragm is smooth, granular, or rugulate. The more elaborate sculpture is fommed by low, discontinuous features of the periphragm. The periphragm gives rise to long tapering homs that are usually hollow, wrinkled to rugulate, and often darker than the rest of the cyst. Some horns appear solid in the most distal three-quarters of their length. The base of the horns are often striate. The apical horn may exceed the length of the central body, whereas the antapical homs are somewhat shorter, although they too are long. The endophragm generally does not extend into the pericoel of the horns, but always fomms a barrier between the endocoel of the central body and pericoel of the horns. This basal barrier is usually quite dark, perhaps due to thickening of the endophragm in this area.
Paratabulation: The only indication of paratabulation is the outline of the combination archeopyle (IPa).
Paracingulum: The paracingulum is not evident on most specimens, although it may be indicated by an unspiraled but distinct fold or by two low ridges.
Parasulcus: Indications of a parasulcus are generally absent, but a shallow depression in the parasulcal area may be present.
Archeopyle: The 2a intercalary and the 4" paraplates are delineated on specimens with a fully developed archeopyle margin. Accessory parasutures around the archeopyle margin may indicate the position of additional paraplates. Specimens with a completely developed or clearly displayed archeopyle are rare. Four types of archeopyles were observed on various specimens: Ia, I, (IP)a and IPa. These are thought to be part of a developmental continuum, culminating in an IPa type archeopyle, with a free 2a paraplate and an adcingular adnate 4" paraplate.
Size: Range of 10 specimens: endocyst length, 44(51)57 µm, pericyst width, 21(27)39 µm, apical hom length up to 54 µm, antapical horn length up to 36 µm, periphragm thickness <0.5 µm, endophragm thickness c. 0.5 µm.
Holotype: Wrenn and Hart, 1988, fig.29, no.5.
Locus typicus: Seymour Island, Antarctica
Stratum typicum: Eocene
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Octodinium askiniae Wrenn and Hart, 1988, is a subelliptical to subtriangular cornucavate peridinioid cyst with a combination archeopyle, resulting from the loss of 2a, which may be partly or completely detached, and the 4", which is adnate. The 2a is eight-sided. The single apical and two equal antapical horns are long and tapering. The periphragm is smooth, granular or rugulate. Length is
44-57 µm.
--------------------------------------------------
Original diagnosis: Wrenn and Hart, 1988, p.359
A species of Octodinium characterized by long tapering apical and antapical horns and periphragm ornamentation consisting of grana or rugulae.
Original description: Wrenn and Hart, 1988, p.360
Shape: The cornucavate cysts vary in outline from subelliptical to subtriangular. Subelliptical cysts are widest in the paracingular area, whereas subtriangular specimens are as wide or wider antapically than they are in the paracingular region. The cysts are convex between the apical and antapical horns, and straight to convave between the two antapical horns. Relatively long apical and antapical horns arise from the three comers of the central body.
Phragma: The periphragm is smooth, granular, or rugulate. The more elaborate sculpture is fommed by low, discontinuous features of the periphragm. The periphragm gives rise to long tapering homs that are usually hollow, wrinkled to rugulate, and often darker than the rest of the cyst. Some horns appear solid in the most distal three-quarters of their length. The base of the horns are often striate. The apical horn may exceed the length of the central body, whereas the antapical homs are somewhat shorter, although they too are long. The endophragm generally does not extend into the pericoel of the horns, but always fomms a barrier between the endocoel of the central body and pericoel of the horns. This basal barrier is usually quite dark, perhaps due to thickening of the endophragm in this area.
Paratabulation: The only indication of paratabulation is the outline of the combination archeopyle (IPa).
Paracingulum: The paracingulum is not evident on most specimens, although it may be indicated by an unspiraled but distinct fold or by two low ridges.
Parasulcus: Indications of a parasulcus are generally absent, but a shallow depression in the parasulcal area may be present.
Archeopyle: The 2a intercalary and the 4" paraplates are delineated on specimens with a fully developed archeopyle margin. Accessory parasutures around the archeopyle margin may indicate the position of additional paraplates. Specimens with a completely developed or clearly displayed archeopyle are rare. Four types of archeopyles were observed on various specimens: Ia, I, (IP)a and IPa. These are thought to be part of a developmental continuum, culminating in an IPa type archeopyle, with a free 2a paraplate and an adcingular adnate 4" paraplate.
Size: Range of 10 specimens: endocyst length, 44(51)57 µm, pericyst width, 21(27)39 µm, apical hom length up to 54 µm, antapical horn length up to 36 µm, periphragm thickness <0.5 µm, endophragm thickness c. 0.5 µm.