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Orobodinium tantillum
Holotype: Plate XIV, 3, 4
Diagnosis: A species of Orobodinium with a microgranulate autophragm, non-tabulate to weakly tabulate of gonyaulacacean type; inferred combination archeopyle, operculum attached or free.
Etymology: From‘tantillus’ (Latin), meaning “so little, so small”, inrelation to the very small size of the cyst.
Material: Palynological strew samples; 2842 m Io-1; 2810 m, 2861 m, Jansz-3; 3074.9 m Pyxis-1
Age: Callovian–Oxfordian (C. ancorum–W. spectabilis zones; Fig. 5).
Lithostratigraphic occurrence: The Laminaria, Elang, Frigate, Montara and lower Vulcan fms of the Bonaparte Basin. The Calypso Fm, Dingo Claystone, Jansz Sandstone and Eliassen Fm of the Northern Carnarvon Basin.
Description: A small, spherical to subspherical, proximate dinoflagellate cyst with a thin, <1 μm-thick, autophragm, densely covered in rounded to irregularly shaped microgranulae, rarely aligned along sutural margins, especially along the cingulum and hypocystal plate boundaries. Sulcal notch often visible or ventral attachment of the operculum. Characteristic heptagonal to octagonal archeopyle shape suggests the presence of multiple anterior intercalary plates. Inferred gonyaulacacean tabulation of formula:?pr,?4′,?3–5a, 7″,?c,?”’, 1p, 1″”,? s. Archeopyle likely combination apical and anterior intercalary, type (tAtI); operculum attached or free.
Dimensions: (102 specimens measured)
Length without opercula: 18 (22) 33
Width: 17 (21) 30
Comparison and remarks: The small size, distinctive archeopyle configuration and general lack of tabulation support an assignment to Orobodinium rather than Microdinium, while the nature of the autophragm prevents attribution to Fostericysta and Jansonia. The presence of seven precingular plates and faint tabulation prevents an attribution to Sentusidinium. Orobodinium tantillum differs from other species of the genus in having a granulate autophragm. The archeopyle is inferred to include some small anterior intercalary plates based on the precingular arrangement, and the tendency for the operculum to sometimes remain attached.Weakly tabulate specimens are rare.
Diagnosis: A species of Orobodinium with a microgranulate autophragm, non-tabulate to weakly tabulate of gonyaulacacean type; inferred combination archeopyle, operculum attached or free.
Etymology: From‘tantillus’ (Latin), meaning “so little, so small”, inrelation to the very small size of the cyst.
Material: Palynological strew samples; 2842 m Io-1; 2810 m, 2861 m, Jansz-3; 3074.9 m Pyxis-1
Age: Callovian–Oxfordian (C. ancorum–W. spectabilis zones; Fig. 5).
Lithostratigraphic occurrence: The Laminaria, Elang, Frigate, Montara and lower Vulcan fms of the Bonaparte Basin. The Calypso Fm, Dingo Claystone, Jansz Sandstone and Eliassen Fm of the Northern Carnarvon Basin.
Description: A small, spherical to subspherical, proximate dinoflagellate cyst with a thin, <1 μm-thick, autophragm, densely covered in rounded to irregularly shaped microgranulae, rarely aligned along sutural margins, especially along the cingulum and hypocystal plate boundaries. Sulcal notch often visible or ventral attachment of the operculum. Characteristic heptagonal to octagonal archeopyle shape suggests the presence of multiple anterior intercalary plates. Inferred gonyaulacacean tabulation of formula:?pr,?4′,?3–5a, 7″,?c,?”’, 1p, 1″”,? s. Archeopyle likely combination apical and anterior intercalary, type (tAtI); operculum attached or free.
Dimensions: (102 specimens measured)
Length without opercula: 18 (22) 33
Width: 17 (21) 30
Comparison and remarks: The small size, distinctive archeopyle configuration and general lack of tabulation support an assignment to Orobodinium rather than Microdinium, while the nature of the autophragm prevents attribution to Fostericysta and Jansonia. The presence of seven precingular plates and faint tabulation prevents an attribution to Sentusidinium. Orobodinium tantillum differs from other species of the genus in having a granulate autophragm. The archeopyle is inferred to include some small anterior intercalary plates based on the precingular arrangement, and the tendency for the operculum to sometimes remain attached.Weakly tabulate specimens are rare.