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Trithyrodinium partridgei
From Fensome et al., 2019:
Trithyrodinium partridgei Willumsen and Vajda 2010, p.529,531; figs.5A–F.
Holotype: Willumsen and Vajda 2010, figs.5A–B.
Age: Early Paleocene.
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Original description (Willumsen and Vajda 2010):
Trithyrodinium partridgei sp. nov. (Fig. 5A–F)
Diagnosis. Circumcavate, ovoid peridinioid cyst with short apical horn and two antapical horns of unequal length. Wall consisting of three layers that are most distinguishable in apical and antapical areas where the walls are less appressed. Periphragm and mesophragm thin and appressed to each other except in apical and antapical areas; mesophragm foveolate. Paratabulation indicated by intercalary archeopyle of type 3I/3I. Paracingulum represented by a bulge in the cingular area on ventral surface of cyst. From a mid-dorsal view the right antapical horn is larger and more pointed than the left antapical horn. Operculum consisting of three intercalary plates that are generally attached.
Description. Circumcavate, ovoid, dorsoventrally compressed peridinioid cyst, with one short conical and distally rounded apical horn (Fig. 5E). The two antapical horns are of unequal lengths but in a middorsal view the left antapical horn is smaller and less pointed than the right antapical horn (Fig. 5F). The total cyst length is 70(79)90 µm and total width is 60(65)70 µm (eight specimens measured). The cyst wall comprises three layers: peri-, meso- and endophragm. The periphragm is thin, smooth and closely appressed to the mesophragm. The mesophragm is relatively thin, transparent and foveolate. Foveolae are ca 0.5–1.0 µm in diameter and most recognizable in the apical and antapical areas where the wall layers are less compressed. The pericoel is fully developed only in the apical and antapical areas. The endocyst is ovoid, longer than broad, relatively thick and brown. The paratabulation is indicated by an intercalary (type 3I/ 3I) archeopyle. A bulge in the cingular area indicates the paracingulum of the cyst. This protrusion is best developed on the ventral surface of the cyst. The operculum consists of three intercalary plates and is commonly in place or partly attached (Fig. 5A–E).
Remarks. The foveolate mesophragm differentiates Trithyrodinium partridgei from all other Trithyrodinium species. The brown colour of the endocyst, also evident in other Trithyrodinium species, is easily destroyed if the kerogen is extensively oxidized (see also Nøhr-Hansen & Dam 1999). Variations in the standard paraplate configuration such as a reduced 2a paraplate were not observed (May & Benson 1979). Trithyrodinium partridgei has so far been recorded only in Fairfield Quarry, Dunedin.
Trithyrodinium partridgei Willumsen and Vajda 2010, p.529,531; figs.5A–F.
Holotype: Willumsen and Vajda 2010, figs.5A–B.
Age: Early Paleocene.
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Original description (Willumsen and Vajda 2010):
Trithyrodinium partridgei sp. nov. (Fig. 5A–F)
Diagnosis. Circumcavate, ovoid peridinioid cyst with short apical horn and two antapical horns of unequal length. Wall consisting of three layers that are most distinguishable in apical and antapical areas where the walls are less appressed. Periphragm and mesophragm thin and appressed to each other except in apical and antapical areas; mesophragm foveolate. Paratabulation indicated by intercalary archeopyle of type 3I/3I. Paracingulum represented by a bulge in the cingular area on ventral surface of cyst. From a mid-dorsal view the right antapical horn is larger and more pointed than the left antapical horn. Operculum consisting of three intercalary plates that are generally attached.
Description. Circumcavate, ovoid, dorsoventrally compressed peridinioid cyst, with one short conical and distally rounded apical horn (Fig. 5E). The two antapical horns are of unequal lengths but in a middorsal view the left antapical horn is smaller and less pointed than the right antapical horn (Fig. 5F). The total cyst length is 70(79)90 µm and total width is 60(65)70 µm (eight specimens measured). The cyst wall comprises three layers: peri-, meso- and endophragm. The periphragm is thin, smooth and closely appressed to the mesophragm. The mesophragm is relatively thin, transparent and foveolate. Foveolae are ca 0.5–1.0 µm in diameter and most recognizable in the apical and antapical areas where the wall layers are less compressed. The pericoel is fully developed only in the apical and antapical areas. The endocyst is ovoid, longer than broad, relatively thick and brown. The paratabulation is indicated by an intercalary (type 3I/ 3I) archeopyle. A bulge in the cingular area indicates the paracingulum of the cyst. This protrusion is best developed on the ventral surface of the cyst. The operculum consists of three intercalary plates and is commonly in place or partly attached (Fig. 5A–E).
Remarks. The foveolate mesophragm differentiates Trithyrodinium partridgei from all other Trithyrodinium species. The brown colour of the endocyst, also evident in other Trithyrodinium species, is easily destroyed if the kerogen is extensively oxidized (see also Nøhr-Hansen & Dam 1999). Variations in the standard paraplate configuration such as a reduced 2a paraplate were not observed (May & Benson 1979). Trithyrodinium partridgei has so far been recorded only in Fairfield Quarry, Dunedin.