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Talladinium
From Williams et al., 2017:
[Talladinium, Williams, Damassa, Fensome and Guerstein in Fensome et al., 2009, p. 61–62.
Type species: as Charlesdowniea wulagenensis, Mao Shaozhi and Norris, 1988 (pl.13, fig.6)], NOW Talladinium wulagenense.
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Original description [Fensome et al., 2009]:
Diagnosis:
Peridiniacean (wetzelielloidean) cysts that are proximate and dorsoventrally compressed; the pericyst is typically subrounded to subpentagonal in outline, with or without polar and lateral horns. Cavate and holocavate: periphragm bearing processes that are distally united to form a discontinuous ectophragm. The processes and ectophragm form simulate complexes that delineate the tabulation.
Archaeopyle intercalary, involving 2a plate that is quadra, length and width approximately equal; operculum soleiform.
Description:
The dorso-ventrally compressed, subrounded to subrhomboidal to subpentagonal pericyst usually has one apical, two lateral and one or two antapical horns that are generally of reduced length. If there are two antapical horns, the left is invariably the longer. In dorso-ventral view, the endocyst is usually rhomboidal. Cavation (between endophragm and periphragm) ranges from being narrowly circumcavate to cornucavate. The periphragm is generally thin, smooth and bears processes that are distally united by a discontinuous ectophragm, which delineates and replicates the tabulation. Because of the presence of an ectophragm as well as the separated endophragm and periphragm the morphology can be described as both cavate and holocavate. Generally, the processes (between periphragm and ectophragm) are contabular to penicontabular, but are not sutural. Some processes form 'lists' or narrow strips that parallel the plate boundaries, but are often absent from the margin towards the cingulum. A single row of processes usually delineates the cingulum and these processes are distally united by 'lists' or membranous ribbons of ectophragm to form linear complexes. The sulcus is delineated by three to four process complexes. The endophragm is invariably thin. Talladinium has a soleiform archaeopyle, with a periand endoarchaeopyle of similar size: the shape varies from elongate to subrounded, when the length and width are approximately equal. The two opercula are always attached anteriorly. When the archaeopyle is not visible, we consider that this usually indicates that the two opercula have fallen back into their original position. In most circumcavate specimens, the periarchaeopyle does not extend into the anterior part of the pericoel; in cornucavate specimens the periarchaeopyle does not extend into the apical pericoel.
Remarks:
The diagnosis can also serve as a synopsis. Mao Shaozhi & Norris (1988) described the species Charlesdowniea wulagenensis, which they compared to Charlesdowniea clathrata and Charlesdowniea coleothrypta. In their diagnosis for Charlesdowniea wulagenensis, Mao Shaozhi & Norris stated that the operculum remained attached anteriorly. This is confirmed in their illustration of the holotype (Mao Shaozhi & Norris, 1988: pl. 13, fig. 6) and two other specimens (Mao Shaozhi & Norris, 1988: pl.13, figs 5, 7). Thus, the species has a soleiform archaeopyle. Lentin & Vozzhennikova (1989) designated the holotype of Charlesdowniea coleothrypta as the type of the genus Charlesdowniea. This species has an equi-epeliform archaeopyle in which the perioperculum is detached, as shown by the holotype (Williams & Downie 1966b: pl. 18, fig. 8). Consequently, we consider Charlesdowniea to have an equiepeliform archaeopyle. To accommodate species formerly in Charledowniea that have soleiform archaeopyles, we (Williams, Damassa, Fensome & Guerstein, unpublished results) are erecting the genus Talladinium. It is not possible to be certain of the archaeopyle in Charlesdowniea clathrata (now Talladinium? clathratum) but from the outline of the pericyst, the reduced horns and the late Eocene age, it should be soleiform. As noted for Rhombodinium, the soleiform archaeopyle is common in the Bartonian and, in our view, becomes exclusive among wetzelielloids in the Priabonian and Oligocene. Talladinium shows many of the morphological features of Wetzeliella — the development of pericoel(s), the length of horns, and thickness of the periphragm and endophragm. It differs from Wetzeliella in the connection of the processes distally and strong indications of tabulation reflected by the complexes. Rhombodinium lacks processes.
[Talladinium, Williams, Damassa, Fensome and Guerstein in Fensome et al., 2009, p. 61–62.
Type species: as Charlesdowniea wulagenensis, Mao Shaozhi and Norris, 1988 (pl.13, fig.6)], NOW Talladinium wulagenense.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description [Fensome et al., 2009]:
Diagnosis:
Peridiniacean (wetzelielloidean) cysts that are proximate and dorsoventrally compressed; the pericyst is typically subrounded to subpentagonal in outline, with or without polar and lateral horns. Cavate and holocavate: periphragm bearing processes that are distally united to form a discontinuous ectophragm. The processes and ectophragm form simulate complexes that delineate the tabulation.
Archaeopyle intercalary, involving 2a plate that is quadra, length and width approximately equal; operculum soleiform.
Description:
The dorso-ventrally compressed, subrounded to subrhomboidal to subpentagonal pericyst usually has one apical, two lateral and one or two antapical horns that are generally of reduced length. If there are two antapical horns, the left is invariably the longer. In dorso-ventral view, the endocyst is usually rhomboidal. Cavation (between endophragm and periphragm) ranges from being narrowly circumcavate to cornucavate. The periphragm is generally thin, smooth and bears processes that are distally united by a discontinuous ectophragm, which delineates and replicates the tabulation. Because of the presence of an ectophragm as well as the separated endophragm and periphragm the morphology can be described as both cavate and holocavate. Generally, the processes (between periphragm and ectophragm) are contabular to penicontabular, but are not sutural. Some processes form 'lists' or narrow strips that parallel the plate boundaries, but are often absent from the margin towards the cingulum. A single row of processes usually delineates the cingulum and these processes are distally united by 'lists' or membranous ribbons of ectophragm to form linear complexes. The sulcus is delineated by three to four process complexes. The endophragm is invariably thin. Talladinium has a soleiform archaeopyle, with a periand endoarchaeopyle of similar size: the shape varies from elongate to subrounded, when the length and width are approximately equal. The two opercula are always attached anteriorly. When the archaeopyle is not visible, we consider that this usually indicates that the two opercula have fallen back into their original position. In most circumcavate specimens, the periarchaeopyle does not extend into the anterior part of the pericoel; in cornucavate specimens the periarchaeopyle does not extend into the apical pericoel.
Remarks:
The diagnosis can also serve as a synopsis. Mao Shaozhi & Norris (1988) described the species Charlesdowniea wulagenensis, which they compared to Charlesdowniea clathrata and Charlesdowniea coleothrypta. In their diagnosis for Charlesdowniea wulagenensis, Mao Shaozhi & Norris stated that the operculum remained attached anteriorly. This is confirmed in their illustration of the holotype (Mao Shaozhi & Norris, 1988: pl. 13, fig. 6) and two other specimens (Mao Shaozhi & Norris, 1988: pl.13, figs 5, 7). Thus, the species has a soleiform archaeopyle. Lentin & Vozzhennikova (1989) designated the holotype of Charlesdowniea coleothrypta as the type of the genus Charlesdowniea. This species has an equi-epeliform archaeopyle in which the perioperculum is detached, as shown by the holotype (Williams & Downie 1966b: pl. 18, fig. 8). Consequently, we consider Charlesdowniea to have an equiepeliform archaeopyle. To accommodate species formerly in Charledowniea that have soleiform archaeopyles, we (Williams, Damassa, Fensome & Guerstein, unpublished results) are erecting the genus Talladinium. It is not possible to be certain of the archaeopyle in Charlesdowniea clathrata (now Talladinium? clathratum) but from the outline of the pericyst, the reduced horns and the late Eocene age, it should be soleiform. As noted for Rhombodinium, the soleiform archaeopyle is common in the Bartonian and, in our view, becomes exclusive among wetzelielloids in the Priabonian and Oligocene. Talladinium shows many of the morphological features of Wetzeliella — the development of pericoel(s), the length of horns, and thickness of the periphragm and endophragm. It differs from Wetzeliella in the connection of the processes distally and strong indications of tabulation reflected by the complexes. Rhombodinium lacks processes.