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Jansonia jurassica
Jansonia jurassica Pocock, 1972, p.97-98, pl.29, figs.8-9; text-figs.14-15.
Holotype: Pocock, 1972, pl.29, fig.8; Jansonius, 1986, pl.3, figs.4-6
Locus typicus: Tidewater Eastern Crown, W Canada
Stratum typicum: Late Bajocian
Original description: Pocock, 1972, p.97
Vesicle small; more or less isodiametric; pear-shaped in outline; epitheca terminated by a smoothly rounded hollow apical horn about 10.0 Ám long which is only very rarely preserved (seen on only one of over two hundred specimens examined); hypotheca hemispherical; smooth; no antapical processes developed; transverse furrow about 6.0 Ám wide; parallel-sided; slightly helicoidal; longitudinal furrow rarely seen; sutures reflected onto surface of vesicle of some specimens as very faint lines of minute granules; invisible on others; tabulation impossible to determine from any one specimen; partial tabulation, determined from several grains, appears to be (?"), 6", 6g, 6""", 1P, 1""""; archeopyle apical with simple free operculum; vesicle two-layered; capsule less than 0.25 Ám thick; smooth; tightly appressed to outer layer; outer layer 0.5--1.0 Ám thick; surface finely and closely granulose; colour brown; length 25.0 (33.0) 40.0 Ám (excluding apical horn); width 23.0 (33.0) 43.0 Ám.
Supplemental description: Jansonius, 1986, p.211
(Holotype) 37 x 37 Ám, dorsal side up (4" in the center); characteristically brown and leathery in appearance, wall thinning and becoming nearly colorless along the apical archeopyle; often darker in the region of the cingulum. The cingulum (6-8 Ám wide) is distinctly delineated by two ridges; the displacement of the cingulum on the ventral side is very slight. Precingular plates are indicated by small acccessory sutures; however, it is difficult to discern their number (apparently six). No more than a few vague ridges delineating postcingulars can be observed. The whole surface of the grain is covered with a sculpture of low, often interrupted, wandering ridges that form a shallow incomplete reticulum; muri, and grooves (or brochi) between them, about 0.4-0.5 Ám wide; wall, including sculpture, about 0.8-0.9 Ám thick (thinner near apex). At low power the sculpture appears as granulation, possibly because the muri are uneven in height and bulk. (In other specimens the sculpture actually may be reduced to scattered granules.) It is characteristic of the preservation that many random cracks occur in the cyst, especially in the hypocyst, which do not seem to coincide with any paratabulation.
Remarks. Some hundred specimens have been seen by me, and a few appear to have a small thin apical operculum attached to one of the precingulars. No specimens have been observed showing the apical horn mentioned by Pocock. The one specimen from which it was described is lost, and was not photographed; thus it seems possible that abnormal development, or extraneous matter, may have been responsible for this appearance. The absence of paratabulation (other than incipient accessory precingular sutures and the distinct cingulum) is characteristic.
Holotype: Pocock, 1972, pl.29, fig.8; Jansonius, 1986, pl.3, figs.4-6
Locus typicus: Tidewater Eastern Crown, W Canada
Stratum typicum: Late Bajocian
Original description: Pocock, 1972, p.97
Vesicle small; more or less isodiametric; pear-shaped in outline; epitheca terminated by a smoothly rounded hollow apical horn about 10.0 Ám long which is only very rarely preserved (seen on only one of over two hundred specimens examined); hypotheca hemispherical; smooth; no antapical processes developed; transverse furrow about 6.0 Ám wide; parallel-sided; slightly helicoidal; longitudinal furrow rarely seen; sutures reflected onto surface of vesicle of some specimens as very faint lines of minute granules; invisible on others; tabulation impossible to determine from any one specimen; partial tabulation, determined from several grains, appears to be (?"), 6", 6g, 6""", 1P, 1""""; archeopyle apical with simple free operculum; vesicle two-layered; capsule less than 0.25 Ám thick; smooth; tightly appressed to outer layer; outer layer 0.5--1.0 Ám thick; surface finely and closely granulose; colour brown; length 25.0 (33.0) 40.0 Ám (excluding apical horn); width 23.0 (33.0) 43.0 Ám.
Supplemental description: Jansonius, 1986, p.211
(Holotype) 37 x 37 Ám, dorsal side up (4" in the center); characteristically brown and leathery in appearance, wall thinning and becoming nearly colorless along the apical archeopyle; often darker in the region of the cingulum. The cingulum (6-8 Ám wide) is distinctly delineated by two ridges; the displacement of the cingulum on the ventral side is very slight. Precingular plates are indicated by small acccessory sutures; however, it is difficult to discern their number (apparently six). No more than a few vague ridges delineating postcingulars can be observed. The whole surface of the grain is covered with a sculpture of low, often interrupted, wandering ridges that form a shallow incomplete reticulum; muri, and grooves (or brochi) between them, about 0.4-0.5 Ám wide; wall, including sculpture, about 0.8-0.9 Ám thick (thinner near apex). At low power the sculpture appears as granulation, possibly because the muri are uneven in height and bulk. (In other specimens the sculpture actually may be reduced to scattered granules.) It is characteristic of the preservation that many random cracks occur in the cyst, especially in the hypocyst, which do not seem to coincide with any paratabulation.
Remarks. Some hundred specimens have been seen by me, and a few appear to have a small thin apical operculum attached to one of the precingulars. No specimens have been observed showing the apical horn mentioned by Pocock. The one specimen from which it was described is lost, and was not photographed; thus it seems possible that abnormal development, or extraneous matter, may have been responsible for this appearance. The absence of paratabulation (other than incipient accessory precingular sutures and the distinct cingulum) is characteristic.