Back
Arachnodinium
From Fensome et al., 2019:
Arachnodinium, Wilson and Clowes, 1982, p.97–98.
Type: Wilson, 1967a, fig.37, as Aiora fenestrata.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Wilson and Clowes, 1982]:
Diagnosis:
Trabeculate two-layered cysts comprising a spheroidal or ovoidal central body, with intratabular precingular processes which reflex towards the antapex, bifurcate, and coalesce distally to form an entirely encircling trabecular network. A single prominent, hollow, antapical process is present. Archeopyle apical, type (tA); operculum free. Paratabulation apparently gonyaulacacean.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Williams, 1987, p. 21:
Synopsis:
Cyst body subspherical to ellipsoidal with a prominent antapical process and seven intratabular processes (6" + as); a complex, trabecular network, which extends posteriorly from the distal ends of the seven intratabular processes, encircles the body but fails to enclose the antapical process; archeopyle apical, type [4A], operculum free.
Description:
Shape: Outline in equatorial views variable owing to irregular folding of trabecular network; apicalantapical outline in polar views more or less circular in undistorted specimens. Cyst body subspherical to ellipsoidal.
Wall features: These include: 1. a broadly conical to tubular antapical process, 2. seven intratabular processes arranged in a transverse row near the archeopyle margin, and 3. an exterior, trabecular network with mostly large, open areas. Body, processes and trabeculae smooth, processes
and some trabeculae may be striate (usually discernible only under the SEM); parts of trabeculum may be denticulate and others may be irregularly perforate.
Wall relationships: Endophragm and periphragm virtually indistinguishable on cyst body; processes and trabeculae formed by the periphragm.
Archeopyle: Apical, type [4A], operculum free and without processes according to J. Wrenn (pers. comm., 1984).
Paratabulation: Indicated by archeopyle margin and by intratabular processes; both reflect six precingular paraplates (6") and one anterior
sulcal paraplate (as). Antapical processes interpreted as representing paraplate 1````.
Paracingulum: Not indicated.
Parasulcus: Anterior position shown by anterior sulcal process, other indications of the parasulcus are lacking.
Size: Intermediate to large, approximately 75 to 140 µm.
Affinities:
Arachnodinium differs from Rigaudella Below 1982 in not having postcingular processes and in possessing a simple antapical process. In apical antapical view, Arachnodinium resembles Balteocysta Stover and Evitt 1978. However, Balteocysta has equatorial processes and a precingular rather than an apical archeopyle.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Arachnodinium Wilson and Clowes, 1962. Stover and Williams (1987, p.21). Cyst body subspherical to ellipsoidal with a prominent antapical process and seven intratabular processes (6" + as); a complex, trabecular network, which extends posteriorly from the distal ends of the seven intratabular processes, encircles the body but fails to enclose the antapical process; archeopyle apical, type [4A], operculum free.
Arachnodinium, Wilson and Clowes, 1982, p.97–98.
Type: Wilson, 1967a, fig.37, as Aiora fenestrata.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Wilson and Clowes, 1982]:
Diagnosis:
Trabeculate two-layered cysts comprising a spheroidal or ovoidal central body, with intratabular precingular processes which reflex towards the antapex, bifurcate, and coalesce distally to form an entirely encircling trabecular network. A single prominent, hollow, antapical process is present. Archeopyle apical, type (tA); operculum free. Paratabulation apparently gonyaulacacean.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Modified description:
Stover and Williams, 1987, p. 21:
Synopsis:
Cyst body subspherical to ellipsoidal with a prominent antapical process and seven intratabular processes (6" + as); a complex, trabecular network, which extends posteriorly from the distal ends of the seven intratabular processes, encircles the body but fails to enclose the antapical process; archeopyle apical, type [4A], operculum free.
Description:
Shape: Outline in equatorial views variable owing to irregular folding of trabecular network; apicalantapical outline in polar views more or less circular in undistorted specimens. Cyst body subspherical to ellipsoidal.
Wall features: These include: 1. a broadly conical to tubular antapical process, 2. seven intratabular processes arranged in a transverse row near the archeopyle margin, and 3. an exterior, trabecular network with mostly large, open areas. Body, processes and trabeculae smooth, processes
and some trabeculae may be striate (usually discernible only under the SEM); parts of trabeculum may be denticulate and others may be irregularly perforate.
Wall relationships: Endophragm and periphragm virtually indistinguishable on cyst body; processes and trabeculae formed by the periphragm.
Archeopyle: Apical, type [4A], operculum free and without processes according to J. Wrenn (pers. comm., 1984).
Paratabulation: Indicated by archeopyle margin and by intratabular processes; both reflect six precingular paraplates (6") and one anterior
sulcal paraplate (as). Antapical processes interpreted as representing paraplate 1````.
Paracingulum: Not indicated.
Parasulcus: Anterior position shown by anterior sulcal process, other indications of the parasulcus are lacking.
Size: Intermediate to large, approximately 75 to 140 µm.
Affinities:
Arachnodinium differs from Rigaudella Below 1982 in not having postcingular processes and in possessing a simple antapical process. In apical antapical view, Arachnodinium resembles Balteocysta Stover and Evitt 1978. However, Balteocysta has equatorial processes and a precingular rather than an apical archeopyle.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Arachnodinium Wilson and Clowes, 1962. Stover and Williams (1987, p.21). Cyst body subspherical to ellipsoidal with a prominent antapical process and seven intratabular processes (6" + as); a complex, trabecular network, which extends posteriorly from the distal ends of the seven intratabular processes, encircles the body but fails to enclose the antapical process; archeopyle apical, type [4A], operculum free.