Back
Phelodinium harringtonii
Phelodinium harringtonii Levy and Harwood, 2000, p.212,214, pl.8, figs.a–d.
Holotype: Levy and Harwood, 2000, pl.8, fig.a.
Age: middle-late Eocene.
Original description (Levy and Harwood, 2000)
Derivation of name. Named in recognition of the contributions made to the study of Antarctic geology by H.J. Harrington.
Holotype. Plate 8, Figure a. UNSM PB99-03: Sample MTD 42, slide 2, middle to upper Eocene erratic, McMurdo Sound, Antarctica.
Diagnosis. A species of Phelodinium characterized by a hypocyst with concave lateral and posterior margins and a short round apical horn on the pericyst and endocyst. The cyst is usually longer than it is wide. The wall layers are smooth and are commonly closely appressed.
Description. Shape. A cornucavate peridinioid dinoflagellate cyst. The lateral margins of the epicyst are typically straight to convex, whereas the lateral margins of the hypocyst are concave. The epicyst and hypocyst are joined across a broad equatorial region. A short, rounded apical horn is present on both the pericyst and endocyst. Two antapical horns are present and may be pointed. The posterior margin is usually concave. Phragma. The wall layers consist of an endophragm and periphragm that are thin and smooth. The two wall layers are typically closely appressed. Separation between the periphragm and endophragm is only evident in the region of the apical and antapical horns. Paratabulation. Peridinioid paratabulation is indicated only by the presence of an intercalary archeopyle. Paracingulum. The position of the paracingulum is delineated by straight longitudinal lateral margins in the equatorial region. On several specimens the paracingulum is indicated by faint paracingular folds that occur in the periphragm.
Parasulcus. In specimens that possess paracingular folds the parasulcus is indicated by a longitudinal break in the folds. Otherwise, the parasulcus is not indicated. Archeopyle. The intercalary archeopyle is formed by the complete removal of the broad hexa 2a paraplate. The AR ranges from 0.5 to 1.2 (mean 0.7).
Dimensions. Observed range (five specimens): pericyst length - 60 to 93μm (mean 80μm), pericyst width - 57 to 77 μm (mean 68μm).
Comments/comparison. Phelodinium harringtonii has a similar shape to P. magnificum (Stanley) Stover and Evitt, 1978, but is smaller and lacks the frilled paracingular borders. P. harringtonii differs from P.
boldii Wrenn and Hart (1988), P. nigericum Biffi and Grignani (1983) and P. africanum Biffi and Grignani (1983) by having a hypocyst with concave lateral margins, a length to width ratio greater than one, and poorly developed paracingular folds or ridges. P. harringtonii superficially resembles Lejeunecysta hyalina in specimens where the pericyst and endocyst are closely appressed. However, most specimens are cornucavate (Plate 8, fig. d). Stratigraphic Occurrence. Middle to upper Eocene erratics, McMurdo Sound, Antarctica.
Holotype: Levy and Harwood, 2000, pl.8, fig.a.
Age: middle-late Eocene.
Original description (Levy and Harwood, 2000)
Derivation of name. Named in recognition of the contributions made to the study of Antarctic geology by H.J. Harrington.
Holotype. Plate 8, Figure a. UNSM PB99-03: Sample MTD 42, slide 2, middle to upper Eocene erratic, McMurdo Sound, Antarctica.
Diagnosis. A species of Phelodinium characterized by a hypocyst with concave lateral and posterior margins and a short round apical horn on the pericyst and endocyst. The cyst is usually longer than it is wide. The wall layers are smooth and are commonly closely appressed.
Description. Shape. A cornucavate peridinioid dinoflagellate cyst. The lateral margins of the epicyst are typically straight to convex, whereas the lateral margins of the hypocyst are concave. The epicyst and hypocyst are joined across a broad equatorial region. A short, rounded apical horn is present on both the pericyst and endocyst. Two antapical horns are present and may be pointed. The posterior margin is usually concave. Phragma. The wall layers consist of an endophragm and periphragm that are thin and smooth. The two wall layers are typically closely appressed. Separation between the periphragm and endophragm is only evident in the region of the apical and antapical horns. Paratabulation. Peridinioid paratabulation is indicated only by the presence of an intercalary archeopyle. Paracingulum. The position of the paracingulum is delineated by straight longitudinal lateral margins in the equatorial region. On several specimens the paracingulum is indicated by faint paracingular folds that occur in the periphragm.
Parasulcus. In specimens that possess paracingular folds the parasulcus is indicated by a longitudinal break in the folds. Otherwise, the parasulcus is not indicated. Archeopyle. The intercalary archeopyle is formed by the complete removal of the broad hexa 2a paraplate. The AR ranges from 0.5 to 1.2 (mean 0.7).
Dimensions. Observed range (five specimens): pericyst length - 60 to 93μm (mean 80μm), pericyst width - 57 to 77 μm (mean 68μm).
Comments/comparison. Phelodinium harringtonii has a similar shape to P. magnificum (Stanley) Stover and Evitt, 1978, but is smaller and lacks the frilled paracingular borders. P. harringtonii differs from P.
boldii Wrenn and Hart (1988), P. nigericum Biffi and Grignani (1983) and P. africanum Biffi and Grignani (1983) by having a hypocyst with concave lateral margins, a length to width ratio greater than one, and poorly developed paracingular folds or ridges. P. harringtonii superficially resembles Lejeunecysta hyalina in specimens where the pericyst and endocyst are closely appressed. However, most specimens are cornucavate (Plate 8, fig. d). Stratigraphic Occurrence. Middle to upper Eocene erratics, McMurdo Sound, Antarctica.