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Papuadinium apiculatum
Papuadinium apiculatum (Cookson and Eisenack, 1960b, p.254, pl.39, fig.15) Davey, 1988, p.42. Emendation: Davey, 1988, p.42–43, as Papuadinium apiculatum
Originally Cannosphaeropsis, subsequently Adnatosphaeridium, thirdly Rigaudella, fourthly (and now) Papuadinium.
Holotype: Cookson and Eisenack, 1960, pl.39, fig.15
Locus typicus: Canning Basin, W Australia
Stratum typicum: Probably Tithonian
Original description: Cookson and Eisenack, 1960, p. 254: Cannosphaeropsis apiculata
Shell small, sphaerical with simple network composed of about eight to twelve solid sometimes flattened supporting processes which branch distally and thin connecting threads which bear small spinules.
Dimensions: holotype - shell 40 µm, overall 86 µm; other specimens shell 30-40 µm, overall 55-76 µm.
Emended diagnosis: Davey, 1987, p.42-42
Shape: Cyst skolochorate. Body is spherical to subspherical with possible
dorso-ventral flattening although orientation is difficult.
Wall: Smooth to very lightly scabrate. Acavate.
Processes: The width of the solid processes varies somewhat, the narrowest ones perhaps being in the sulcal region. The length of the processes varies with the longest tending to be in the antapical region and the shortest towards the apical region. The stouter processes tend to trifurcate distally whereas the narrower ones are bifurcate. The trabeculae are well developed, varying in width and regularity, and bearing granules, coni and/or small spines. Cingular processes are only developed on the hypocystal margin of the cingulum.
Archaeopyle: Combination epicystal, Type tAtP. Operculum normally detached and
with a circular outline.
Size: Moderate.
Emended description: Davey, 1987, p. 43:
The wall is thin and is less than 1 µm in thickness. The processes vary from approximately 1 µm to 3 mm in thickness. Small, internal vacuoles may be present in the larger processes. The trabeculae have a rather irregular appearance as they not only vary in width but bear various types or ornamentation. The lowest type of ornamentation may be best described as "bumps" and the most common being small coni. Thin spines, up to 2 µm in length, may also occur.
Affinities:
Davey, 1987, p. 43: As for the genus, P. apiculatum is distinguished from all previously described dinocysts by the combination of epicystal archaeopyle and trabeculae arising frorn gonal processes. The forms described by Below (1982) as Rigaudella apiculata (figs. 7, 24 and 26) from the Callovian and Oxfordian of southern Germany are not considered to be con-specific with the present species.
The specimens of Below are certainly related to the R. aemula complex.
Cannosphaeropsis glabra Cookson & Eisenack 1974, from the middle Cretaceous of Western Australia, is superficially similar although the trabeculae are smooth. A more precise comparision is not possible as the archaeopyle type is not reliably determined in this species.
Originally Cannosphaeropsis, subsequently Adnatosphaeridium, thirdly Rigaudella, fourthly (and now) Papuadinium.
Holotype: Cookson and Eisenack, 1960, pl.39, fig.15
Locus typicus: Canning Basin, W Australia
Stratum typicum: Probably Tithonian
Original description: Cookson and Eisenack, 1960, p. 254: Cannosphaeropsis apiculata
Shell small, sphaerical with simple network composed of about eight to twelve solid sometimes flattened supporting processes which branch distally and thin connecting threads which bear small spinules.
Dimensions: holotype - shell 40 µm, overall 86 µm; other specimens shell 30-40 µm, overall 55-76 µm.
Emended diagnosis: Davey, 1987, p.42-42
Shape: Cyst skolochorate. Body is spherical to subspherical with possible
dorso-ventral flattening although orientation is difficult.
Wall: Smooth to very lightly scabrate. Acavate.
Processes: The width of the solid processes varies somewhat, the narrowest ones perhaps being in the sulcal region. The length of the processes varies with the longest tending to be in the antapical region and the shortest towards the apical region. The stouter processes tend to trifurcate distally whereas the narrower ones are bifurcate. The trabeculae are well developed, varying in width and regularity, and bearing granules, coni and/or small spines. Cingular processes are only developed on the hypocystal margin of the cingulum.
Archaeopyle: Combination epicystal, Type tAtP. Operculum normally detached and
with a circular outline.
Size: Moderate.
Emended description: Davey, 1987, p. 43:
The wall is thin and is less than 1 µm in thickness. The processes vary from approximately 1 µm to 3 mm in thickness. Small, internal vacuoles may be present in the larger processes. The trabeculae have a rather irregular appearance as they not only vary in width but bear various types or ornamentation. The lowest type of ornamentation may be best described as "bumps" and the most common being small coni. Thin spines, up to 2 µm in length, may also occur.
Affinities:
Davey, 1987, p. 43: As for the genus, P. apiculatum is distinguished from all previously described dinocysts by the combination of epicystal archaeopyle and trabeculae arising frorn gonal processes. The forms described by Below (1982) as Rigaudella apiculata (figs. 7, 24 and 26) from the Callovian and Oxfordian of southern Germany are not considered to be con-specific with the present species.
The specimens of Below are certainly related to the R. aemula complex.
Cannosphaeropsis glabra Cookson & Eisenack 1974, from the middle Cretaceous of Western Australia, is superficially similar although the trabeculae are smooth. A more precise comparision is not possible as the archaeopyle type is not reliably determined in this species.