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Dimidiadinium uncinatum
Dimidiadinium uncinatum Brideaux, 1977
Now Tubotuberella. Originally Dimidiadinium, subsequently (and now) Tubotuberella.
Holotype: Brideaux, 1977, pl.15, figs.2-5; Jan du Chêne et al., 1986, pl.127, figs.1-3
Locus typicus: Richardson Mountains, District of Mackenzie, Canada
Stratum typicum: Hauterivian-Barremian
Original diagnosis: Brideaux, 1977, p. 38
Shape: Pericyst ambitus broadly rhomboidal, the maximum width occurring at the latitude of the paracingulum; epipericyst tapering to form a short apical horn; hypopericyst tapering gently at first but then more abruptly to form a frustum, subquadrate in plan, and open antapically to form an antapical breach.
Endocyst ambitus subcircular to subrhombic. A small pericoel occurs only where the pericyst and endocyst separate to form an apical horn; antapical pericoel formed through the extension of the posterior hypopericyst and its separation from the posterior hypoendocyst; slight dorso-ventral compression.
Phragma: Periphragm thin, about 0.5 Ám thick, of constant thickness; surface sculpture smooth to scabrate; periphragm raised into low, thin parasutural ridges which bear thincolumned trifurcate processes at the junction of parasutural ridges and at the four corners of the quadrate to subquadrate antapical breach; parasutural ridges up to 3 Ám high but typically 1-2 Ám; processes up to 11 Ám, typically 8-10 Ám. Endophragm thin, about 0.5 Ám thick, smooth.
Paratabulation: Paratabulation on the periphragm denoted by parasutural ridges and gonally positioned trifurcate processes, and determined as ?4", 6", xc, 5""", 0-1p, 1"""". Details of apical paraplates difficult to determine because of folding of the periphragm; of the precingular paraplates, 3" is broadly pentagonal; of the post-cingular paraplates, all are broadly pentagonal, elongate and terminate adjacent to the antapical breach; 1""" and 5""" are the smallest; antapical breach occupying the position of the antapical paraplate, quadrate to subquadrate and flanked by four gonal processes. Evidence for paratabulation on endophragm lacking, except at the endoarcheopyle.
Archeopyle/operculum: Periarcheopyle formed by the loss of the third precingular paraplate; perioperculum simple, detached, broad;y pentagonal and elongate in outline. Endoarcheopyle formed by the loss of the third precingular paraplate; endoperculum simple, detached, broadly pentagonal in shape, but slightly smaller in overall dimensions than the perioperculum. Formula P/P.
Percingulum/perisulcus: Parasutural ridges outline the course of the pericingulum on the pericyst; pericingulum slightly or not at all offset; six pairs of gonal trifurcate processes denote the presence of six cingular paraplates, other evidence for cingular paratabulation lacking. Perisulcus present, position outlined by a shallow, elongate depression, more prominent posteriorly, and by parasutural ridges; perisulcus terminated anteriorly against the first apical paraplate, and posteriorly by the antapical breach. Variation. The apex of the pericyst sometimes bears several short spiny projections. Specimens vary greatly in the numbers of trifurcate processes present (possibly because of variable degree of mechanical damage). Along cingular parasutures, trifurcate processes may be reduced to broad-based, distally acuminate projections in gonal position. Occasional specimens, including the holotype, have a broader separation of the pericyst from the endocyst. ln the vicinity of the apical horn.
Affinities:
Brideaux, 1977, p. 39: Dimidiadinium uncinatum is distinguished from other species placed in this genus by possession of smooth parasutures bearing gonal trifurcate processes.
Now Tubotuberella. Originally Dimidiadinium, subsequently (and now) Tubotuberella.
Holotype: Brideaux, 1977, pl.15, figs.2-5; Jan du Chêne et al., 1986, pl.127, figs.1-3
Locus typicus: Richardson Mountains, District of Mackenzie, Canada
Stratum typicum: Hauterivian-Barremian
Original diagnosis: Brideaux, 1977, p. 38
Shape: Pericyst ambitus broadly rhomboidal, the maximum width occurring at the latitude of the paracingulum; epipericyst tapering to form a short apical horn; hypopericyst tapering gently at first but then more abruptly to form a frustum, subquadrate in plan, and open antapically to form an antapical breach.
Endocyst ambitus subcircular to subrhombic. A small pericoel occurs only where the pericyst and endocyst separate to form an apical horn; antapical pericoel formed through the extension of the posterior hypopericyst and its separation from the posterior hypoendocyst; slight dorso-ventral compression.
Phragma: Periphragm thin, about 0.5 Ám thick, of constant thickness; surface sculpture smooth to scabrate; periphragm raised into low, thin parasutural ridges which bear thincolumned trifurcate processes at the junction of parasutural ridges and at the four corners of the quadrate to subquadrate antapical breach; parasutural ridges up to 3 Ám high but typically 1-2 Ám; processes up to 11 Ám, typically 8-10 Ám. Endophragm thin, about 0.5 Ám thick, smooth.
Paratabulation: Paratabulation on the periphragm denoted by parasutural ridges and gonally positioned trifurcate processes, and determined as ?4", 6", xc, 5""", 0-1p, 1"""". Details of apical paraplates difficult to determine because of folding of the periphragm; of the precingular paraplates, 3" is broadly pentagonal; of the post-cingular paraplates, all are broadly pentagonal, elongate and terminate adjacent to the antapical breach; 1""" and 5""" are the smallest; antapical breach occupying the position of the antapical paraplate, quadrate to subquadrate and flanked by four gonal processes. Evidence for paratabulation on endophragm lacking, except at the endoarcheopyle.
Archeopyle/operculum: Periarcheopyle formed by the loss of the third precingular paraplate; perioperculum simple, detached, broad;y pentagonal and elongate in outline. Endoarcheopyle formed by the loss of the third precingular paraplate; endoperculum simple, detached, broadly pentagonal in shape, but slightly smaller in overall dimensions than the perioperculum. Formula P/P.
Percingulum/perisulcus: Parasutural ridges outline the course of the pericingulum on the pericyst; pericingulum slightly or not at all offset; six pairs of gonal trifurcate processes denote the presence of six cingular paraplates, other evidence for cingular paratabulation lacking. Perisulcus present, position outlined by a shallow, elongate depression, more prominent posteriorly, and by parasutural ridges; perisulcus terminated anteriorly against the first apical paraplate, and posteriorly by the antapical breach. Variation. The apex of the pericyst sometimes bears several short spiny projections. Specimens vary greatly in the numbers of trifurcate processes present (possibly because of variable degree of mechanical damage). Along cingular parasutures, trifurcate processes may be reduced to broad-based, distally acuminate projections in gonal position. Occasional specimens, including the holotype, have a broader separation of the pericyst from the endocyst. ln the vicinity of the apical horn.
Affinities:
Brideaux, 1977, p. 39: Dimidiadinium uncinatum is distinguished from other species placed in this genus by possession of smooth parasutures bearing gonal trifurcate processes.