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Phelodinium boldii
Phelodinium boldii Wrenn and Hart, 1988
Holotype: Wrenn and Hart, 1988, figs.33.1,4
Age: Late Paleocene-Eocene
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Original description: [Wrenn and Hart, 1988]:
Phelodinium boldii sp. nov.
Figure 33.1,4
Diagnosis. A species of Phelodinium characterized by large angular, peridinioid cysts that are as wide as they are long. The periphragm
surface may be longitudinally granulate to rugulate. Very short apical and antapical horns. Distinct flagcllar scar in the midparasulcal area.
Intercalary (2a) archeopyle.
Description.
Shape: Most specimens are squat, slightly cornucavate peridinioid dinocysts whose breadth generally exceeds their length. The short antapical horns are approOximately the same length. The short apical horn is usually flat or slightly concave distally. None of the horns are pointed or
solid. Each of the two epicystal sides are slightly longer than any of the three sides of the hypocyst.
Phragma: The thin (<0.5 μm) endoprahgm is smooth to finely granulate. The periphragm is smooth, scabbrate, or rugulate, and is less than 0.5 μm thick. Rugulate ornamentation is longitudinally distributed.
Paratabulation: Paratabulation is assumed to be peridinioid, as suggested by parasutures delimiting a 2a intercalary archeopyle.
Paracingulum: The paracingulum is narrow, planar, and bordered by low folds in the periphragm.
Parasulcus: The location of the parasulcus is suggested by two low folds on the hypocyst that diverge posteriorly. This feature is not always evident. A flagellar scar is evident in the central parasulcul area.
Archeopyle: The 2a intercalary archeopyle is often difficult to detect because the operculum usually remains in place and the parasutures around the operculum may not gape open. The presence and location of the archeopyle may be indicated only by occasional open parasutures.
Dimensions. Observed range (10 specimens): length, 63 to 130 μm (mean, 88 μm); width, 61 to 129 μm (mean, 88 μm): periphragm and
endophragm, each less than 0.5 μm thick.
Discussion and Comparison with Similar Species. Phelodinium boldii sp. nov. resembles P. pumilum Liengjaren et al. (1980) in that the antapical
horns of both are rather short. P. boldii differs from the latter by being much larger, being generally as broad or broader than long, having an
angular to subangular outline, and having scabbrate to rugulate surface sculpture.
Phelodinium boldii sp. nov. is superficially similar to Palaeoperidinium pyrophorum, but differs from that species by having a 2a intercalary
archeopyle, granulate to longitudinally rugulate ornamentation and by lacking pandasutural striae.
Holotype. Slide 8476, W/10, 121.3 x 11.9 (M27). Sample 8476, Section 3, La Meseta Formation, late early Eocene, Seymour Island, Antarctica.
Derivation of Name. Named after Willem van den Bold, in recognition of his significant contributions to micropalaeontology.
Stratigraphic Occurrence. La Meseta Formation (Section 3, Eocene and reworked into Holocene beach deposits; Sections 17, 18, and 19, Eocene); Cross Valley Formation (Section 15, early late Paleocene).
Holotype: Wrenn and Hart, 1988, figs.33.1,4
Age: Late Paleocene-Eocene
------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Wrenn and Hart, 1988]:
Phelodinium boldii sp. nov.
Figure 33.1,4
Diagnosis. A species of Phelodinium characterized by large angular, peridinioid cysts that are as wide as they are long. The periphragm
surface may be longitudinally granulate to rugulate. Very short apical and antapical horns. Distinct flagcllar scar in the midparasulcal area.
Intercalary (2a) archeopyle.
Description.
Shape: Most specimens are squat, slightly cornucavate peridinioid dinocysts whose breadth generally exceeds their length. The short antapical horns are approOximately the same length. The short apical horn is usually flat or slightly concave distally. None of the horns are pointed or
solid. Each of the two epicystal sides are slightly longer than any of the three sides of the hypocyst.
Phragma: The thin (<0.5 μm) endoprahgm is smooth to finely granulate. The periphragm is smooth, scabbrate, or rugulate, and is less than 0.5 μm thick. Rugulate ornamentation is longitudinally distributed.
Paratabulation: Paratabulation is assumed to be peridinioid, as suggested by parasutures delimiting a 2a intercalary archeopyle.
Paracingulum: The paracingulum is narrow, planar, and bordered by low folds in the periphragm.
Parasulcus: The location of the parasulcus is suggested by two low folds on the hypocyst that diverge posteriorly. This feature is not always evident. A flagellar scar is evident in the central parasulcul area.
Archeopyle: The 2a intercalary archeopyle is often difficult to detect because the operculum usually remains in place and the parasutures around the operculum may not gape open. The presence and location of the archeopyle may be indicated only by occasional open parasutures.
Dimensions. Observed range (10 specimens): length, 63 to 130 μm (mean, 88 μm); width, 61 to 129 μm (mean, 88 μm): periphragm and
endophragm, each less than 0.5 μm thick.
Discussion and Comparison with Similar Species. Phelodinium boldii sp. nov. resembles P. pumilum Liengjaren et al. (1980) in that the antapical
horns of both are rather short. P. boldii differs from the latter by being much larger, being generally as broad or broader than long, having an
angular to subangular outline, and having scabbrate to rugulate surface sculpture.
Phelodinium boldii sp. nov. is superficially similar to Palaeoperidinium pyrophorum, but differs from that species by having a 2a intercalary
archeopyle, granulate to longitudinally rugulate ornamentation and by lacking pandasutural striae.
Holotype. Slide 8476, W/10, 121.3 x 11.9 (M27). Sample 8476, Section 3, La Meseta Formation, late early Eocene, Seymour Island, Antarctica.
Derivation of Name. Named after Willem van den Bold, in recognition of his significant contributions to micropalaeontology.
Stratigraphic Occurrence. La Meseta Formation (Section 3, Eocene and reworked into Holocene beach deposits; Sections 17, 18, and 19, Eocene); Cross Valley Formation (Section 15, early late Paleocene).