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Luxadinium
From Williams et al., 2017:
[Luxadinium, Brideaux and Mclntyre, 1975, p. 36
Type species: Luxadinium primulum, Brideaux and McIntyre, 1975 (pl.12, fig.9)]
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Original description: [Brideaux and McIntyre, 1975]:
Description:
Cavate peridinioid dinoflagellate cyst. Periblast broadly pentagonal, generally as long or longer than broad; possessing an apical horn or prominence and one or two antapical prominences, of which the left one is the longer; the periphragm thin, often much thinner than the endophragm, smooth, or with minor and variable ornamentation that may or may not be related to reflected tabulation. Endoblast subcircular or distinctly longer than broad; the apex rounded or with a distinct apical prominence which projects into the apical pericoel; the antapex flattened to rounded, rarely extended to form a left antapical prominence; the endophragm smooth, or with minor and variable sculpture that may or may not be related to reflected tabulation. Periphragm and endophragm not in contact and forming a single pericoel; or in contact at the mid-region of the cyst and forming an apical pericoel, a right antapical pericoel and, occasionally, a much reduced left antapical pericoel.
Periarcheopyle and endarcheopyle formed by the loss of three reflected intercalary plates(1a to 3a) and three reflected precingular plates (3`` to 5``). Endoperculum simple or compound and, where compound, composed of up to six endopercular pieces; perioperculum simple or compound, and presumably paralleling the endoperculum for the particular species; opercula not attached.
Reflected tabulation distinct or poorly developed to absent; where distinct, indicated by the shape of the archeopyle, intertabular growth areas and/or intratabular ornamentation; reflected tabulation scheme, 4`, 3a, 7``, Oc, 5```, 2````.
Cingulum distinct and displaced from one-half to two cingular widths; sulcus generally distinct, extending onto the epitract anteriorly and widening slightly posteriorly.
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Modified description:
Stover and Evitt, 1978, p. 212:
Synopsis:
Cysts proximate, generally bicavate or circumcavate, compressed, roundly peridinioid to subcircular; paratabulation peridiniacean, distinct, poorly developed, or absent; when present expressed by pandasuturate areas and intratabular ornamentation; combination archeopyle, Types "tl3P" or tl3P.
Description:
Shape: Compressed, roundly peridinioid to nearly subcircular in outline; apical and one or two antapical horns, typically short.
Wall relationships: Cysts bicavate or circumcavate, possibly cornucavate.
Wall features: Endophragm smooth, faintly ornamented, or with apiculate intratabular areas separated by smooth pandasuturate bands. Periphragm generally smooth or faintly ornamented.
Paratabulation: Expressed by archeopyle only or by archeopyle plus intratabular and pandasuturate features; peridiniacean, formula: 4`,3a, 7``,
Xc, 5```, 2````.
Archeopyle: Combination, Types "tl3P" or tl3P; when latter, composed of up to six opercular pieces; operculum free.
Paracingulum: Indicated by low to prominent parallel, transverse, equatorial ridges.
Parasulcus: Expressed by poorly delimited shallow depression, mainly on hypocyst.
Size: Intermediate.
Affinities:
Luxadinium differs from Laciniadinium in having a free operculum, whereas in the latter, the operculum is attached along its antapical margin. Luxadinium differs from Palaeoperidinium and Saeptodinium in that the third apical paraplate is not involved in archeopyle formation.
[Luxadinium, Brideaux and Mclntyre, 1975, p. 36
Type species: Luxadinium primulum, Brideaux and McIntyre, 1975 (pl.12, fig.9)]
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Original description: [Brideaux and McIntyre, 1975]:
Description:
Cavate peridinioid dinoflagellate cyst. Periblast broadly pentagonal, generally as long or longer than broad; possessing an apical horn or prominence and one or two antapical prominences, of which the left one is the longer; the periphragm thin, often much thinner than the endophragm, smooth, or with minor and variable ornamentation that may or may not be related to reflected tabulation. Endoblast subcircular or distinctly longer than broad; the apex rounded or with a distinct apical prominence which projects into the apical pericoel; the antapex flattened to rounded, rarely extended to form a left antapical prominence; the endophragm smooth, or with minor and variable sculpture that may or may not be related to reflected tabulation. Periphragm and endophragm not in contact and forming a single pericoel; or in contact at the mid-region of the cyst and forming an apical pericoel, a right antapical pericoel and, occasionally, a much reduced left antapical pericoel.
Periarcheopyle and endarcheopyle formed by the loss of three reflected intercalary plates(1a to 3a) and three reflected precingular plates (3`` to 5``). Endoperculum simple or compound and, where compound, composed of up to six endopercular pieces; perioperculum simple or compound, and presumably paralleling the endoperculum for the particular species; opercula not attached.
Reflected tabulation distinct or poorly developed to absent; where distinct, indicated by the shape of the archeopyle, intertabular growth areas and/or intratabular ornamentation; reflected tabulation scheme, 4`, 3a, 7``, Oc, 5```, 2````.
Cingulum distinct and displaced from one-half to two cingular widths; sulcus generally distinct, extending onto the epitract anteriorly and widening slightly posteriorly.
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Modified description:
Stover and Evitt, 1978, p. 212:
Synopsis:
Cysts proximate, generally bicavate or circumcavate, compressed, roundly peridinioid to subcircular; paratabulation peridiniacean, distinct, poorly developed, or absent; when present expressed by pandasuturate areas and intratabular ornamentation; combination archeopyle, Types "tl3P" or tl3P.
Description:
Shape: Compressed, roundly peridinioid to nearly subcircular in outline; apical and one or two antapical horns, typically short.
Wall relationships: Cysts bicavate or circumcavate, possibly cornucavate.
Wall features: Endophragm smooth, faintly ornamented, or with apiculate intratabular areas separated by smooth pandasuturate bands. Periphragm generally smooth or faintly ornamented.
Paratabulation: Expressed by archeopyle only or by archeopyle plus intratabular and pandasuturate features; peridiniacean, formula: 4`,3a, 7``,
Xc, 5```, 2````.
Archeopyle: Combination, Types "tl3P" or tl3P; when latter, composed of up to six opercular pieces; operculum free.
Paracingulum: Indicated by low to prominent parallel, transverse, equatorial ridges.
Parasulcus: Expressed by poorly delimited shallow depression, mainly on hypocyst.
Size: Intermediate.
Affinities:
Luxadinium differs from Laciniadinium in having a free operculum, whereas in the latter, the operculum is attached along its antapical margin. Luxadinium differs from Palaeoperidinium and Saeptodinium in that the third apical paraplate is not involved in archeopyle formation.