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Fibradinium variculum
Fibradinium variculum Stover and Helby, 1987
Holotype: Stover and Helby, 1987, fig.7A-C
Locus typicus: Perth Basin, W Australia
Stratum typicum: Barremian-Early Aptian
Original description: Stover and Helby, 1987, p. 267
Cysts proximate, subspherical; epicysts shorter than hypocysts. Cyst wall of two, distinctly different and appressed layers, an inner dense, apparently featureless autophragm of essentially uniform thickness (about 1.5 Ám), and an outer, fibrous, vacuolate ectophragm of variable thickness (about 1.5-4 Ám). Ectophragm generally thinner in the precingular area, at the base of the paracingulum and probably at the base of the parasulcus, than elsewhere on the cyst. In plan view fibroid structures impart a granular appearance to the ectophragm, with the "granules" being unevenly distributed. Archeopyle apical, type [tA], with a small, circular to slightly angular opening, which is usually small relative to cyst diameter. Operculum normally free. Transverse depression nearer the apex than the antapex, delimited anteriorly and posteriorly by the increased height of the ectophragm, and defining an undivided paracingulum with ends not offset or offset slightly. Parasulcus defined by a longitudinal depression extending from the paracingulum to near the antapex and widening posteriorly. Clear indications of paraplates lacking. Specimens ranging in length from 34-41 Ám, and in width from 32-38 Ám; 25 specimens measured.
Affinities:
Stover and Helby, 1987, p. 267: Fibradinium variculum differs from F. annetorpense Morgenroth 1968 in lacking parasutural features which outline paraplates. Judging from the information in Morgenroth (1968), the size, shape, wall layering, position of the paracingulum, and the archeopyle of the two species appear to be identical, or very similar.
Holotype: Stover and Helby, 1987, fig.7A-C
Locus typicus: Perth Basin, W Australia
Stratum typicum: Barremian-Early Aptian
Original description: Stover and Helby, 1987, p. 267
Cysts proximate, subspherical; epicysts shorter than hypocysts. Cyst wall of two, distinctly different and appressed layers, an inner dense, apparently featureless autophragm of essentially uniform thickness (about 1.5 Ám), and an outer, fibrous, vacuolate ectophragm of variable thickness (about 1.5-4 Ám). Ectophragm generally thinner in the precingular area, at the base of the paracingulum and probably at the base of the parasulcus, than elsewhere on the cyst. In plan view fibroid structures impart a granular appearance to the ectophragm, with the "granules" being unevenly distributed. Archeopyle apical, type [tA], with a small, circular to slightly angular opening, which is usually small relative to cyst diameter. Operculum normally free. Transverse depression nearer the apex than the antapex, delimited anteriorly and posteriorly by the increased height of the ectophragm, and defining an undivided paracingulum with ends not offset or offset slightly. Parasulcus defined by a longitudinal depression extending from the paracingulum to near the antapex and widening posteriorly. Clear indications of paraplates lacking. Specimens ranging in length from 34-41 Ám, and in width from 32-38 Ám; 25 specimens measured.
Affinities:
Stover and Helby, 1987, p. 267: Fibradinium variculum differs from F. annetorpense Morgenroth 1968 in lacking parasutural features which outline paraplates. Judging from the information in Morgenroth (1968), the size, shape, wall layering, position of the paracingulum, and the archeopyle of the two species appear to be identical, or very similar.