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Trinovantedinium harpagonium
Trinovantedinium harpagonium De Verteuil and Norris, 1992
Holotype: De Verteuil and Norris, 1992, pl.4, figs.1-3
Locus typicus: St. Leonard Member ("Bed 18") of the Choptank Formation, north of Scientists Cliffs but below Parker Creek, west shore of Chesapeake Bay, Calvert County Maryland
Stratum typicum: Middle Miocene
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Trinovantedinium harpagonianum Bujak, 1984, emend. de Verteuil and Norris, 1992. Diagnosis from de Verteuil and Norris (1992, p.414-415), proximochorate, intermediate, pigmented, protoperidiniacean cysts compressed dorsoventrally with a rounded pentagonal outline. The wall has a total thickness of less than 0.5 µm and comprises two closely adpressed layers. Periphragm psilate or scabrate, and forms taeniate, tubiform to infundibular, penitabular processes that are distally recurved. Archeopyle 2a, generally iso-thetaform or iso-deltaform but sometimes an angular re-entrant is present on the H3 margin of the free opercular plate. Size: length excluding processes 52-78 µm, width at cingulum excluding processes 48-68 µm, processes 8-16 µm.
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Original diagnosis: De Verteuil and Norris, 1992, p. 414
Proximochorate, intermediate, pigmented, protoperidiniacean cysts compressed dorsoventrally with a rounded pentagonal outline. The wall has a total thickness of less than 0.5 µm and comprises two closely adpressed layers. Periphragm psilate or scabrate, and forms taeniate, tubiform to infundibular, penitabular processes that are distally recurved. Archeopyle 2a, generally iso-thetaform or iso-deltaform, but sometimes an angular re-entrant is present on the H3 margin of the free opercular plate.
Original description: De Verteuil and Norris, 1992, p. 414
The hypocyst may be somewhat less than or equal to the epicyst in height, and the cyst height/width ratio is close to 1. Two moderately developed and symmetrical antapical lobes are generally present, separated by a straight or shallow concave (less than 25% of width) antapical depression. The cyst is widest at the cingulum which is marked with processes but is not indented. The flanks of the epicyst are typically convex and the apex is rounded. In well preserved specimens the two wall layers are always closely adpressed. The processes are taeniate, up to 0.25 times the equatorial radius in length, and are predominantly penitabular. Distally the processes are flared in the plane of flattening and terminate orthogonally or are recurved with finely denticulate margins. The cingulum is 5-7 µm wide and level; it is marked by prominent processes in two discontinuous rows. The sulcus is broad (approximately 40% of its height), straight, without processes, and generally featureless except for the two flagellar scars on the midventral hypocyst. These are elliptical to circular with or without a slightly thickened margin, arranged vertically and about 1-2 µm in diameter. The archeopyle is formed by loss of the large 2a intercalary but the plate margins and their included angles are often rounded. In some specimens the archeopyle is essentially seven sided due to a re-entrant of the H3 margin. (Text-Figures 8-9, Plate 4, figs. 6, 8).
Dimensions. Length, excluding processes, 52(60)78 µm; holotype 52 µm. Width at cingulum, excluding processes, 48(59)68 µm; holotype, 55 µm. Processes, 8-16 µm. Fourteen specimens measured.
Discussion. The presence of two wall layers in this species can be observed in what have been interpreted to be naturally oxidized specimens. These occur infrequently in some samples and are characterized by two non-pigmented or pale wall layers that are loosely adpressed and separated in some areas. In such specimens the cyst shape is generally collapsed or torn and the processes can be observed to be formed solely from the periphragm.
Affinities:
De Verteuil and Norris, 1992, p. 414: T. harpagonium differs from all other species of the genus in the distinctive anvil-like recurved taeniate form of its process terminations. This species is most similar to Trinovantedinium variabile Bujak 1984 in which the process terminations are aculeate.
Holotype: De Verteuil and Norris, 1992, pl.4, figs.1-3
Locus typicus: St. Leonard Member ("Bed 18") of the Choptank Formation, north of Scientists Cliffs but below Parker Creek, west shore of Chesapeake Bay, Calvert County Maryland
Stratum typicum: Middle Miocene
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Trinovantedinium harpagonianum Bujak, 1984, emend. de Verteuil and Norris, 1992. Diagnosis from de Verteuil and Norris (1992, p.414-415), proximochorate, intermediate, pigmented, protoperidiniacean cysts compressed dorsoventrally with a rounded pentagonal outline. The wall has a total thickness of less than 0.5 µm and comprises two closely adpressed layers. Periphragm psilate or scabrate, and forms taeniate, tubiform to infundibular, penitabular processes that are distally recurved. Archeopyle 2a, generally iso-thetaform or iso-deltaform but sometimes an angular re-entrant is present on the H3 margin of the free opercular plate. Size: length excluding processes 52-78 µm, width at cingulum excluding processes 48-68 µm, processes 8-16 µm.
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Original diagnosis: De Verteuil and Norris, 1992, p. 414
Proximochorate, intermediate, pigmented, protoperidiniacean cysts compressed dorsoventrally with a rounded pentagonal outline. The wall has a total thickness of less than 0.5 µm and comprises two closely adpressed layers. Periphragm psilate or scabrate, and forms taeniate, tubiform to infundibular, penitabular processes that are distally recurved. Archeopyle 2a, generally iso-thetaform or iso-deltaform, but sometimes an angular re-entrant is present on the H3 margin of the free opercular plate.
Original description: De Verteuil and Norris, 1992, p. 414
The hypocyst may be somewhat less than or equal to the epicyst in height, and the cyst height/width ratio is close to 1. Two moderately developed and symmetrical antapical lobes are generally present, separated by a straight or shallow concave (less than 25% of width) antapical depression. The cyst is widest at the cingulum which is marked with processes but is not indented. The flanks of the epicyst are typically convex and the apex is rounded. In well preserved specimens the two wall layers are always closely adpressed. The processes are taeniate, up to 0.25 times the equatorial radius in length, and are predominantly penitabular. Distally the processes are flared in the plane of flattening and terminate orthogonally or are recurved with finely denticulate margins. The cingulum is 5-7 µm wide and level; it is marked by prominent processes in two discontinuous rows. The sulcus is broad (approximately 40% of its height), straight, without processes, and generally featureless except for the two flagellar scars on the midventral hypocyst. These are elliptical to circular with or without a slightly thickened margin, arranged vertically and about 1-2 µm in diameter. The archeopyle is formed by loss of the large 2a intercalary but the plate margins and their included angles are often rounded. In some specimens the archeopyle is essentially seven sided due to a re-entrant of the H3 margin. (Text-Figures 8-9, Plate 4, figs. 6, 8).
Dimensions. Length, excluding processes, 52(60)78 µm; holotype 52 µm. Width at cingulum, excluding processes, 48(59)68 µm; holotype, 55 µm. Processes, 8-16 µm. Fourteen specimens measured.
Discussion. The presence of two wall layers in this species can be observed in what have been interpreted to be naturally oxidized specimens. These occur infrequently in some samples and are characterized by two non-pigmented or pale wall layers that are loosely adpressed and separated in some areas. In such specimens the cyst shape is generally collapsed or torn and the processes can be observed to be formed solely from the periphragm.
Affinities:
De Verteuil and Norris, 1992, p. 414: T. harpagonium differs from all other species of the genus in the distinctive anvil-like recurved taeniate form of its process terminations. This species is most similar to Trinovantedinium variabile Bujak 1984 in which the process terminations are aculeate.