Back
Endoscrinium rostratum
Endoscrinium rostratum (Brideaux and McIntyre, 1975) Below, 1981
Originally Scriniodinium, subsequently (and now) Endoscrinium.
Jan du Chene et al., 1986, retained this species in Scriniodinium Klement, 1957. Lentin and Williams, 1989, retained it in Endoscrinium.
Holotype: Brideaux and McIntyre, 1975, pl.10, figs.12-14; Jan du Chene et al., 1986, pl.111, figs.2-4.
Locus typicus: Horton River Formation, Section CR14A-68, District of Mackenzie, Canada
Stratum typicum: Middle Albian. Periblast
Age: Middle Albian
Original diagnosis: Brideaux and McIntyre 1975, p. 33-34: Scriniodinium rostratum
Periblast outline ovoid, with a distinctive, beak-like, apical prominence, and flattened antapically; wall two layered, with a precingular archeopyle developed in both layers; cingulum off-set one cingular width; reflected tabulation outlined by low sutural ridges and corresponding to the scheme, lpr, ?4", 6", 6c, 5""-?6"", 1"", ?lp.
Original description: Brideaux and McIntyre 1975, p. 33-34: Scriniodinium rostratum
The periblast is ovoid, the length greater than the width. The epitract and hypotract are of equal or approximately equal size. The apical region tapers rapidly to form a shoulder-like outline, but is prolonged into an apical prominence. The prominence is slightly thickened at the apex and is distinctively "beak-like" in appearance (Pl. 10, fig. 13). The antapex is flattened. The periphragm is thin, less than 0.5Á thick in optical section, often strongly folded, finely granulose, and bears low, narrow sutural ridges which often are obscured by folding. The endoblast is ovoid, the length greater than the width. The endophragm is smooth and does not appear to be in close contact with the periphragm. The peri-archeopyle is precingular and formed by the loss of reflected plate 3". The peri-operculum is free. The endarcheopyle is similar to the peri-archeopyle in shape and position and probably is also precingular. On one specimen the peri-operculum is still partially attached but, where observed in several other specimens, the peri-operculum is free. The periphragm bears evidence of reflected tabulation in the form of sutural ridges, less than 0.5Á wide and high, which outline a reflected tabulation determined as lpr, ?4", 6", 6c, 5-?6"", 1"", ?lp. The tabulation scheme is difficult to determine accurately because the periphragm tends to fold along the sutural ridges and secondarily across the reflected plates. This is the case particularly for the apical region, where reflection tabulation has been observed only imperfectly on a few specimens. The small depression at the apex, surrounded by the thickened apical prominence is interpreted as a reflected pre-apical plate (pr). rhe endophragm shows no signs of tabulation other than presence of an archeopyle. Ridges similar to the sutural ridges outline a cingulum and its six reflected plates. The cingulum, where visible, is 5 to 7Á wide and offset about one cingulum width. A sulcal area is indistinctly visible on several specimens, but folds obscure its course. rhe sulcus appears to follow a slightly sinuous path and extends a short distance onto the epitract.
Dimensions: holotype: length, 65Á; periblast-width, 55Á; endoblast length, 50Á; endoblast width 51Á. Range (35 measured specimens): Periblast length, 53-75Á; periblast width, 50-65Á; endoblast length, 45-60Á; endoblast width, 38-50Á.
Occurrence. Horton River Formation (Middle Albian).
Originally Scriniodinium, subsequently (and now) Endoscrinium.
Jan du Chene et al., 1986, retained this species in Scriniodinium Klement, 1957. Lentin and Williams, 1989, retained it in Endoscrinium.
Holotype: Brideaux and McIntyre, 1975, pl.10, figs.12-14; Jan du Chene et al., 1986, pl.111, figs.2-4.
Locus typicus: Horton River Formation, Section CR14A-68, District of Mackenzie, Canada
Stratum typicum: Middle Albian. Periblast
Age: Middle Albian
Original diagnosis: Brideaux and McIntyre 1975, p. 33-34: Scriniodinium rostratum
Periblast outline ovoid, with a distinctive, beak-like, apical prominence, and flattened antapically; wall two layered, with a precingular archeopyle developed in both layers; cingulum off-set one cingular width; reflected tabulation outlined by low sutural ridges and corresponding to the scheme, lpr, ?4", 6", 6c, 5""-?6"", 1"", ?lp.
Original description: Brideaux and McIntyre 1975, p. 33-34: Scriniodinium rostratum
The periblast is ovoid, the length greater than the width. The epitract and hypotract are of equal or approximately equal size. The apical region tapers rapidly to form a shoulder-like outline, but is prolonged into an apical prominence. The prominence is slightly thickened at the apex and is distinctively "beak-like" in appearance (Pl. 10, fig. 13). The antapex is flattened. The periphragm is thin, less than 0.5Á thick in optical section, often strongly folded, finely granulose, and bears low, narrow sutural ridges which often are obscured by folding. The endoblast is ovoid, the length greater than the width. The endophragm is smooth and does not appear to be in close contact with the periphragm. The peri-archeopyle is precingular and formed by the loss of reflected plate 3". The peri-operculum is free. The endarcheopyle is similar to the peri-archeopyle in shape and position and probably is also precingular. On one specimen the peri-operculum is still partially attached but, where observed in several other specimens, the peri-operculum is free. The periphragm bears evidence of reflected tabulation in the form of sutural ridges, less than 0.5Á wide and high, which outline a reflected tabulation determined as lpr, ?4", 6", 6c, 5-?6"", 1"", ?lp. The tabulation scheme is difficult to determine accurately because the periphragm tends to fold along the sutural ridges and secondarily across the reflected plates. This is the case particularly for the apical region, where reflection tabulation has been observed only imperfectly on a few specimens. The small depression at the apex, surrounded by the thickened apical prominence is interpreted as a reflected pre-apical plate (pr). rhe endophragm shows no signs of tabulation other than presence of an archeopyle. Ridges similar to the sutural ridges outline a cingulum and its six reflected plates. The cingulum, where visible, is 5 to 7Á wide and offset about one cingulum width. A sulcal area is indistinctly visible on several specimens, but folds obscure its course. rhe sulcus appears to follow a slightly sinuous path and extends a short distance onto the epitract.
Dimensions: holotype: length, 65Á; periblast-width, 55Á; endoblast length, 50Á; endoblast width 51Á. Range (35 measured specimens): Periblast length, 53-75Á; periblast width, 50-65Á; endoblast length, 45-60Á; endoblast width, 38-50Á.
Occurrence. Horton River Formation (Middle Albian).