Back
Luxadinium primulum
Luxadinium primulum Brideaux and McIntyre, 1975
Holotype: Brideaux and McIntyre, 1975, pl.12, fig.9
Locus typicus: Horton River Formation, Mackenzie District, Canada.
Stratum typicum: Middle Albian
Age: Middle Albian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Luxadinium primulum Brideaux and McIntyre, 1975. According to Brideaux and McIntyre (1975, p.37), Luxadinium primulum has a pentagonal pericyst, with an apical and one left antapical prominence. Endophragm closely appressed to periphragm but lacking apical and antapical extensions, bearing intratabular apiculae delimiting reflected tabulation of 4', 3a, 7", 0c, 5"’, 2"”. Archeopyle formed by loss of three intercalary and three precingular plates. Endo- and perioperculum compound and composed of the six plates. Cingulum distinct and displaced by one to one and one-half cingular widths. Sulcus generally well defined, wider posteriorly. Size: pericyst length 50-70 µm, width 43-62 µm, endocyst 42-62 µm, width 43-62 µm.
--------------------------------------------------
Original diagnosis: Brideaux and McIntyre 1975, p. 37-38
Peridinioid cavate cyst; the periphragm thin, of pentagonal outline, and with an apical and one left antapical prominence. Endophragm slightly thicker, closely appressed to periblast but lacking apical and antapical extensions, bearing intratabular apiculae delimiting reflected tabulation of 4', 3a, 7", Oc, 5"', 2"". Archeopyle in both layers, formed by loss of three reflected intercalaries and three precingular plates. Endoperculum and? Perioperculum compound, and composed of six reflected plates la to 3a and 3" to 5". Cingulum distinct and displaced up to one and one-half cingular widths; sulcus generally well defined, wider posteriorly.
Original description: Brideaux and McIntyre 1975, p. 37-38
The basic outline of the pericyst is pentagonal with well-rounded corners. The cyst length is always greater than the width, with the maximum width occurring at the cingulum. The periblast tapers apically to a well-rounded prominence. The left side of the periblast is produced antapically to form a small, pointed prominence; the right side is rounded or, occasionally, is produced to form a much-reduced right antapical prominence. The endoblast is similar in shape and outline, but is not extended apically, and is almost completely flattened antapically.
The periphragm is smooth, very thin, almost veil-like, and is often stripped away. The endophragm is thicker, about 1.011 thick in optical section, with intratabular apiculae, 0.25 to 0.5Á high and wide. The apiculae are absent in the intertabular regions and their absence marks the position of reflected sutural lines. The periphragm and endophragm are in contact except at the apical prominence and where antapical prominences occur. There exist, therefore, an apical pericoel, a smaller left antapical pericoel and, occasionally, a much reduced right antapical pericoel.
The archeopyle is formed by the loss of three intercalary and three precingular reflected plates (la to 3a and 3" to 5") in the periphragm and endophragm. No specimen has been observed in which the archeopyle is developed only in the periphragm. The sweeping arc of the anterior margin of the archeopyle is broken only by the characteristic "tongue" of the margin of reflected plate 3' projecting into the opening. The operculum is compound and has been observed, in most cases, as group of disconnected reflected plates. Most common is the association of the large reflected plate 2a together with one or more of the reflected precingular plates 3" to 5". Several specimens have the intercalaries missing with the detached precingular group intact within the endocoel. Rare specimens, including the holotype, show only incipient principal sutural breaks between reflected plates forming the opercula. It is probable that all six plates separate along principal sutures although, occasionally, some may remain attached. Presumably, the respective reflected plates of both wall layers separate as units.
Reflected tabulation is defined on the endophragm by intratabular clusters of apiculate sculpture separated by smooth intertabular regions. The latter mark the reflected courses of the probable growth areas between plates of the thecal stage. The reflected tabulation scheme can be summarized as 4', 7", 0c, 5", 2"". The two reflected antapical plates are discernable only on a few specimens. Reflected tabulation is not exhibited on the periphragm.
The cingulum is outlined on the endophragm by two low parallel ridges which may or may not bear apiculae or, more rarely, by rows of discrete apiculae. The cingulum is displaced from one to one and one-half cingular widths. On the periphragm, two low folds, identical in position to the ridges or apiculate rows of the endophragm, outline the cingulum.
The sulcus is reflected on the endophragm by a shallow indentation, narrower anteriorly, and widening osteriorly to meet the antapical reflected plates. The course of the sulcus also is defined by the sharp borders of the intratabular apiculae outlining reflected plates 1"' and 5"'. On the periphragm, the sulcus is reflected as a similarly shaped shallow depression flanked by folds of the periphragm that parallel the edges of the sulcus on the endophragm. On one specimen, the reflected position of the flagellar pore is well preserved.
Dimensions: Periblast, 70µx 62µ endoblast, 61µx 62µ Range (40 measured specimens) - Periblast length, 50-70µ periblast width, 43-62µendoblast length, 42-62µ endoblast width, 43-62µ
Comparison. Luxadininium primulum sp. nov. is distinguished from Luxadinium propatulum sp. nov., nom.
nov. by possession of a distinctive intratabular apiculate ornament on the endophragm and smooth periphragm, and by the lack of a distinct apical prominence developed on the endoblast.
Ocurrence. Horton River Formation, lower part (Middle Albian).
Holotype: Brideaux and McIntyre, 1975, pl.12, fig.9
Locus typicus: Horton River Formation, Mackenzie District, Canada.
Stratum typicum: Middle Albian
Age: Middle Albian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Luxadinium primulum Brideaux and McIntyre, 1975. According to Brideaux and McIntyre (1975, p.37), Luxadinium primulum has a pentagonal pericyst, with an apical and one left antapical prominence. Endophragm closely appressed to periphragm but lacking apical and antapical extensions, bearing intratabular apiculae delimiting reflected tabulation of 4', 3a, 7", 0c, 5"’, 2"”. Archeopyle formed by loss of three intercalary and three precingular plates. Endo- and perioperculum compound and composed of the six plates. Cingulum distinct and displaced by one to one and one-half cingular widths. Sulcus generally well defined, wider posteriorly. Size: pericyst length 50-70 µm, width 43-62 µm, endocyst 42-62 µm, width 43-62 µm.
--------------------------------------------------
Original diagnosis: Brideaux and McIntyre 1975, p. 37-38
Peridinioid cavate cyst; the periphragm thin, of pentagonal outline, and with an apical and one left antapical prominence. Endophragm slightly thicker, closely appressed to periblast but lacking apical and antapical extensions, bearing intratabular apiculae delimiting reflected tabulation of 4', 3a, 7", Oc, 5"', 2"". Archeopyle in both layers, formed by loss of three reflected intercalaries and three precingular plates. Endoperculum and? Perioperculum compound, and composed of six reflected plates la to 3a and 3" to 5". Cingulum distinct and displaced up to one and one-half cingular widths; sulcus generally well defined, wider posteriorly.
Original description: Brideaux and McIntyre 1975, p. 37-38
The basic outline of the pericyst is pentagonal with well-rounded corners. The cyst length is always greater than the width, with the maximum width occurring at the cingulum. The periblast tapers apically to a well-rounded prominence. The left side of the periblast is produced antapically to form a small, pointed prominence; the right side is rounded or, occasionally, is produced to form a much-reduced right antapical prominence. The endoblast is similar in shape and outline, but is not extended apically, and is almost completely flattened antapically.
The periphragm is smooth, very thin, almost veil-like, and is often stripped away. The endophragm is thicker, about 1.011 thick in optical section, with intratabular apiculae, 0.25 to 0.5Á high and wide. The apiculae are absent in the intertabular regions and their absence marks the position of reflected sutural lines. The periphragm and endophragm are in contact except at the apical prominence and where antapical prominences occur. There exist, therefore, an apical pericoel, a smaller left antapical pericoel and, occasionally, a much reduced right antapical pericoel.
The archeopyle is formed by the loss of three intercalary and three precingular reflected plates (la to 3a and 3" to 5") in the periphragm and endophragm. No specimen has been observed in which the archeopyle is developed only in the periphragm. The sweeping arc of the anterior margin of the archeopyle is broken only by the characteristic "tongue" of the margin of reflected plate 3' projecting into the opening. The operculum is compound and has been observed, in most cases, as group of disconnected reflected plates. Most common is the association of the large reflected plate 2a together with one or more of the reflected precingular plates 3" to 5". Several specimens have the intercalaries missing with the detached precingular group intact within the endocoel. Rare specimens, including the holotype, show only incipient principal sutural breaks between reflected plates forming the opercula. It is probable that all six plates separate along principal sutures although, occasionally, some may remain attached. Presumably, the respective reflected plates of both wall layers separate as units.
Reflected tabulation is defined on the endophragm by intratabular clusters of apiculate sculpture separated by smooth intertabular regions. The latter mark the reflected courses of the probable growth areas between plates of the thecal stage. The reflected tabulation scheme can be summarized as 4', 7", 0c, 5", 2"". The two reflected antapical plates are discernable only on a few specimens. Reflected tabulation is not exhibited on the periphragm.
The cingulum is outlined on the endophragm by two low parallel ridges which may or may not bear apiculae or, more rarely, by rows of discrete apiculae. The cingulum is displaced from one to one and one-half cingular widths. On the periphragm, two low folds, identical in position to the ridges or apiculate rows of the endophragm, outline the cingulum.
The sulcus is reflected on the endophragm by a shallow indentation, narrower anteriorly, and widening osteriorly to meet the antapical reflected plates. The course of the sulcus also is defined by the sharp borders of the intratabular apiculae outlining reflected plates 1"' and 5"'. On the periphragm, the sulcus is reflected as a similarly shaped shallow depression flanked by folds of the periphragm that parallel the edges of the sulcus on the endophragm. On one specimen, the reflected position of the flagellar pore is well preserved.
Dimensions: Periblast, 70µx 62µ endoblast, 61µx 62µ Range (40 measured specimens) - Periblast length, 50-70µ periblast width, 43-62µendoblast length, 42-62µ endoblast width, 43-62µ
Comparison. Luxadininium primulum sp. nov. is distinguished from Luxadinium propatulum sp. nov., nom.
nov. by possession of a distinctive intratabular apiculate ornament on the endophragm and smooth periphragm, and by the lack of a distinct apical prominence developed on the endoblast.
Ocurrence. Horton River Formation, lower part (Middle Albian).