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Spinidinium uncinatum
Spinidinium uncinatum May, 1980
Holotype: May, 1980, pl.10, figs.5-7
Locus typicus: Atlantic Highlands, New Jersey
Stratum typicum: Campanian-Maastrichtian
Original description: May, 1980, p.85
Periblast pentagonal in dorso-ventral outline; dorso-ventrally flattened; tapering apically from cingulum in near-linear fashion to base of short apical horn; tapering antapically from cingulum in near-linear fashion to truncated antapex bearing 2 reduced antapical horns. Short apical horn projects abruptly from apex, tapering and bluntly terminating, bearing 2 terminal lateral spines. Left antapical horn variable in size, may be slightly shorter or longer than apical horn, is conical, and tapers to a point. Right antapical horn generally appears as oblique deflection at right side of antapex. Periphragm smooth, formed into well-developed sutural folds bearing numerous, short, tapering, distally barbed spines, the sutural folds outlining plate equivalents. Plate equivalents well separated by intercalary areas on ventral and dorsal surfaces (except on dorsal epitract), causing the cingulum to be regularly interrupted. Plate equivalents on dorsal epitract positioned immediately adjacent to each other, lacking intercalary areas. Plate areas triangular on ventral surface, trapezoidal on lateral and dorsal surfaces. Reflected tabulation 4", ?3a, 7", ?c, 5""", 2"""". Endoblast ovoidal, filling central cavity of periblast; anterior pericoel occurring in and a short distance beneath the apical horn; broad posterior pericoel occurring at base of apical region. Endophragm smooth. Cingulum interrupted, except on antero-dorsal side; levorotatory with ca. 1/2 cingulum width offset. Sulcus deep, bordered by sutural folds bearing spines, extends ca. 1 cingulum width above cingulum and broadens posteriorly to antapex, terminating between the antapical horns. Archeopyle intercalary (Type Ia/Ia) and is horshoe-shaped.
Discussion: Diagnostic characteristics of S. uncinatum are the pentagonal outline, extended left antapical horn, separated plate fields, the barbed or hooked sutural spines and peridinioid tabulation. Scanning electron microscopy also shows that the periphragm is smooth between sutures, that the spines are capitate, barbed or hooked, and that small apical and antapical plates exist on the horn areas.
Dimensions: Holotype -- L x W, 56 x 31 µm; posterior pericoel length 10 µm, anterior 11 µm; spine length 1.5 µm maximum. Observed range (16 specimens measured): length 50--75 µm, width 29-47 µm; spine length less than 1.5 µm; wall layers, periphragm ca. 0.5 µm, endophragm ca. 0.5 µm.
Affinities:
May, 1980, p.86: S. uncinatum is similar in morphology to S. clavum Harland 1973, S. styloniferum Cookson and Eisenack 1962, and S. Ianternum Cookson and Eisenack 1970. S. clavum, however, has oblate and acuminate processes along sutural positions, plate fields apparently not separated, and cingulum not interrupted or offset. S. styloniferum differs by having intratabular spines, which are bluntly pointed, and a more expanded outline in dorso-ventral view. S. Ianternum is most similar to S. uncinatum in overall morphology; however, differs by possessing distinctly pointed spines, and an apparently larg
Holotype: May, 1980, pl.10, figs.5-7
Locus typicus: Atlantic Highlands, New Jersey
Stratum typicum: Campanian-Maastrichtian
Original description: May, 1980, p.85
Periblast pentagonal in dorso-ventral outline; dorso-ventrally flattened; tapering apically from cingulum in near-linear fashion to base of short apical horn; tapering antapically from cingulum in near-linear fashion to truncated antapex bearing 2 reduced antapical horns. Short apical horn projects abruptly from apex, tapering and bluntly terminating, bearing 2 terminal lateral spines. Left antapical horn variable in size, may be slightly shorter or longer than apical horn, is conical, and tapers to a point. Right antapical horn generally appears as oblique deflection at right side of antapex. Periphragm smooth, formed into well-developed sutural folds bearing numerous, short, tapering, distally barbed spines, the sutural folds outlining plate equivalents. Plate equivalents well separated by intercalary areas on ventral and dorsal surfaces (except on dorsal epitract), causing the cingulum to be regularly interrupted. Plate equivalents on dorsal epitract positioned immediately adjacent to each other, lacking intercalary areas. Plate areas triangular on ventral surface, trapezoidal on lateral and dorsal surfaces. Reflected tabulation 4", ?3a, 7", ?c, 5""", 2"""". Endoblast ovoidal, filling central cavity of periblast; anterior pericoel occurring in and a short distance beneath the apical horn; broad posterior pericoel occurring at base of apical region. Endophragm smooth. Cingulum interrupted, except on antero-dorsal side; levorotatory with ca. 1/2 cingulum width offset. Sulcus deep, bordered by sutural folds bearing spines, extends ca. 1 cingulum width above cingulum and broadens posteriorly to antapex, terminating between the antapical horns. Archeopyle intercalary (Type Ia/Ia) and is horshoe-shaped.
Discussion: Diagnostic characteristics of S. uncinatum are the pentagonal outline, extended left antapical horn, separated plate fields, the barbed or hooked sutural spines and peridinioid tabulation. Scanning electron microscopy also shows that the periphragm is smooth between sutures, that the spines are capitate, barbed or hooked, and that small apical and antapical plates exist on the horn areas.
Dimensions: Holotype -- L x W, 56 x 31 µm; posterior pericoel length 10 µm, anterior 11 µm; spine length 1.5 µm maximum. Observed range (16 specimens measured): length 50--75 µm, width 29-47 µm; spine length less than 1.5 µm; wall layers, periphragm ca. 0.5 µm, endophragm ca. 0.5 µm.
Affinities:
May, 1980, p.86: S. uncinatum is similar in morphology to S. clavum Harland 1973, S. styloniferum Cookson and Eisenack 1962, and S. Ianternum Cookson and Eisenack 1970. S. clavum, however, has oblate and acuminate processes along sutural positions, plate fields apparently not separated, and cingulum not interrupted or offset. S. styloniferum differs by having intratabular spines, which are bluntly pointed, and a more expanded outline in dorso-ventral view. S. Ianternum is most similar to S. uncinatum in overall morphology; however, differs by possessing distinctly pointed spines, and an apparently larg