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Spinidinium colemanii
Spinidinium colemanii Wrenn and Hart, 1988, p.366–367, fig.36, nos.1–2; fig.39, no.2.
Holotype: Wrenn and Hart, 1988, fig.36, nos.1–2.
Age: late Paleocene–Eocene.
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Original description: [Wrenn and Hart, 1988]:
Spinindinium colemanii sp. nov.
Figures 36.1-2, 39.2
Deflandrea macmurdoensis Wilson 1967 sensu Kemp, 1975, Plate 2.
Figures 1-3.
Diagnosis. A species of Spinidinium characterized by its capitate, penitabular spines, small size, unequal hypo- and epicysts, and its posteriorly
adnate 2a intercalary archeopyle.
Description.
Shape: Cornucavate, subpentagonal to subelliptical dinocysts bearing one hundred or more penitabular spines. The paracingulum separates
the epicyst from the hypocyst; the former is usually two to three times the length of the hypocyst. The paracingular area may bulge laterally, giving the dinocyst a subpentagonal shape.
Phragma: Both the endophragm and the periphragm are smooth.
The wall layers are appressed except in the basal regions of the horns.
The periphragm gives rise to capitate spines, whereas the endophragm lacks projections. The short apical horn is capped by two or more capitate spines. The right antapical horn is rarely evident, whereas the left horn is a long, spike-shaped projection bearing one or more accessory spines.
Paratabulation: A paratabulation of x', 3a, 7", xc, 5"', ?2"" is delineated by penitabular capitate spines. The distribution and number of paraplates is obscured by the abundance of the closcly spaced spines and by the presence of accessory rows of spines. The paracingulum and the parasulcus are not divided by rows of spines.
Paracingulum: Low folds capped with short capitate spines delimit the shallow excavation of the paracingulum. Paraplate divisions within the paracingulum were not observed.
Parasulcus: A broad, bare area bordered by rows of spines indicates the location of the parasulcus. Spines are usually absent within the parasulcal arca, although isolated spincs occur on some specimens.
Archeopyle: The archeopyle is formed by the partial detachment of the 2a paraplate, and occasionally by the partial detachment of the 4"
paraplate. The operculum is adnate along the H4 parasuture. A row of penitabular capitate spines occurs on each side of all archeopyle parasu-
tures, except the H4 parasuture. The rows of spines along the H2-H3 and the H5-H6 parasutures of the 2a intercalary paraplate continue below the base of that paraplate and along the margins of the 4 paraplate to the anterior margin of the paracingulum.
Dimensions. Observed range (10 specimens): pericyst length, 42 to 57 μm (mean, 50 μm); pericyst width, 36 to 45 μm (mean, 41 μm); endocyst length, 32 to 40 μm (mean, 37 μm); endocyst width, 30 to 41 μm (mean, 34 μm): process length, 3 to 8 μm; left antapical horn, to 10 μm; apical horn, to 8 μm.
Discussion and Comparison with Similar Species. The capitate spines and their distribution on the pericyst are reminiscent of Spinidinium
macmurdoense. However, the overall shape, much smaller size, more numerous spines, more complete paratabulation, and unequal division of
the dinocyst by the paracingulum differentiate S. colemanii sp. nov. from S. macmurdoense. The dense spinosity of the pericyst of S. colemanii sp. nov. is similar to a specimen of Vozzhennikovia apertura illustrated by Haskell and Wilson (1975; Plate 1, Fig. 6). However, the spines on the
latter are more numerous, smaller, and generally nontabular, rather than penitabular.
Holotype. Slide 8496, W/8, 134.66 x 12.5 (M40). Sample 496, Section 15, Cross Valley Formation, carly late Paleocene, Seymour Island, Antarctica.
Derivation of Name. Named after James M. Coleman, in recognition of his contributions to the study of deltaic processes and deposits.
Stratigraphic Occurrence. Cross Valley Formation (Section 12-13, Eocene, see discussion of age determinations for this section; Section 15 and
16, carly late Paleocene); La Meseta Formation (Section 3, Eocenc and reworked into Holocene beach deposits). The sparse Eocene occurrences
noted above may be due to reworking.
Holotype: Wrenn and Hart, 1988, fig.36, nos.1–2.
Age: late Paleocene–Eocene.
------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Wrenn and Hart, 1988]:
Spinindinium colemanii sp. nov.
Figures 36.1-2, 39.2
Deflandrea macmurdoensis Wilson 1967 sensu Kemp, 1975, Plate 2.
Figures 1-3.
Diagnosis. A species of Spinidinium characterized by its capitate, penitabular spines, small size, unequal hypo- and epicysts, and its posteriorly
adnate 2a intercalary archeopyle.
Description.
Shape: Cornucavate, subpentagonal to subelliptical dinocysts bearing one hundred or more penitabular spines. The paracingulum separates
the epicyst from the hypocyst; the former is usually two to three times the length of the hypocyst. The paracingular area may bulge laterally, giving the dinocyst a subpentagonal shape.
Phragma: Both the endophragm and the periphragm are smooth.
The wall layers are appressed except in the basal regions of the horns.
The periphragm gives rise to capitate spines, whereas the endophragm lacks projections. The short apical horn is capped by two or more capitate spines. The right antapical horn is rarely evident, whereas the left horn is a long, spike-shaped projection bearing one or more accessory spines.
Paratabulation: A paratabulation of x', 3a, 7", xc, 5"', ?2"" is delineated by penitabular capitate spines. The distribution and number of paraplates is obscured by the abundance of the closcly spaced spines and by the presence of accessory rows of spines. The paracingulum and the parasulcus are not divided by rows of spines.
Paracingulum: Low folds capped with short capitate spines delimit the shallow excavation of the paracingulum. Paraplate divisions within the paracingulum were not observed.
Parasulcus: A broad, bare area bordered by rows of spines indicates the location of the parasulcus. Spines are usually absent within the parasulcal arca, although isolated spincs occur on some specimens.
Archeopyle: The archeopyle is formed by the partial detachment of the 2a paraplate, and occasionally by the partial detachment of the 4"
paraplate. The operculum is adnate along the H4 parasuture. A row of penitabular capitate spines occurs on each side of all archeopyle parasu-
tures, except the H4 parasuture. The rows of spines along the H2-H3 and the H5-H6 parasutures of the 2a intercalary paraplate continue below the base of that paraplate and along the margins of the 4 paraplate to the anterior margin of the paracingulum.
Dimensions. Observed range (10 specimens): pericyst length, 42 to 57 μm (mean, 50 μm); pericyst width, 36 to 45 μm (mean, 41 μm); endocyst length, 32 to 40 μm (mean, 37 μm); endocyst width, 30 to 41 μm (mean, 34 μm): process length, 3 to 8 μm; left antapical horn, to 10 μm; apical horn, to 8 μm.
Discussion and Comparison with Similar Species. The capitate spines and their distribution on the pericyst are reminiscent of Spinidinium
macmurdoense. However, the overall shape, much smaller size, more numerous spines, more complete paratabulation, and unequal division of
the dinocyst by the paracingulum differentiate S. colemanii sp. nov. from S. macmurdoense. The dense spinosity of the pericyst of S. colemanii sp. nov. is similar to a specimen of Vozzhennikovia apertura illustrated by Haskell and Wilson (1975; Plate 1, Fig. 6). However, the spines on the
latter are more numerous, smaller, and generally nontabular, rather than penitabular.
Holotype. Slide 8496, W/8, 134.66 x 12.5 (M40). Sample 496, Section 15, Cross Valley Formation, carly late Paleocene, Seymour Island, Antarctica.
Derivation of Name. Named after James M. Coleman, in recognition of his contributions to the study of deltaic processes and deposits.
Stratigraphic Occurrence. Cross Valley Formation (Section 12-13, Eocene, see discussion of age determinations for this section; Section 15 and
16, carly late Paleocene); La Meseta Formation (Section 3, Eocenc and reworked into Holocene beach deposits). The sparse Eocene occurrences
noted above may be due to reworking.