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Aptea securigera
From Fensome et al., 2019:
Aptea securigera, Davey and Verdier, 1974, p.642–643, pl.91, figs.2–3; text-fig.5(vii).
Holotype: Davey and Verdier, 1974, pl.91, fig.3.
Originally Aptea, subsequently Pseudoceratium.
Taxonomic senior synonym: Circulodinium distinctum, according to Fensome et al., (2019a, p.37). Fensome et al. based the synonymy on the morphology of the holotype only.
Age: early Aptian.
Locus typicus: La BÚdoule, SE-France
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Original description: Davey and Verdier 1974, p. 642-643
Diagnosis:
The cyst central body is dorso-ventrally flattened and rounded triangular in shape. The left side is strongly, but evenly, convex; the right epitractal and hypotractal sides are slightly convex to straight and meet at approximately right angles in the cingular region. The right hypotractal side often has a medial convexity. The apex and, to a lesser extent, the antapex are developed as protuberances of the central body and are rounded distally. The cyst surface bears numerous short, flattened, solid processes which are concentrated in the circumferential region. A more or less circular area in the centre of the ventral and dorsal surfaces is devoid of, or possesses only rare, processes. The processes are of variable shape but are typically discrete, expanding both distally and proximally, and are flat-topped distally; their length is more than twice as their medial width. The processes are longer and more variable at the cyst apices. Very rarely the cingulum and other tabulation is marked by narrow bands devoid of processes. The archaeopyle is apical and possesses a strongly zigzag margin. The operculum is usually detached.
Description:
The processes characteristically widen both distally and proximally. Very rarely, narrow processes may bifurcate or trifurcate, or neighbouring processes may be linked medially by a crest. Rarely the bases of two or three neighbouring processes may be linked by a low ridge or thickening of the cyst wall. These thickenings tend to parallel the cyst sides, as do the crests in A. polymorpha. Besides the longer processes at the cyst apices, slightly longer ones may also be present on the left side in the cingular region and on the convexity or bulge, if present, of the right hypotractal side. These longer processes were seen to be linked distally in one specimen.
Dimensions:
Central body length: 73-90 µm; Central body width: 69-87 µm; Central body length (operculum detached): 62-73 µm; Height of processes: 2-10 µm.
Affinities:
Aptea securigera is differentiated from Aptea polymorpha by the absence of well-developed crests and from Aptea eisenacki (Davey 1969) by the presence of numerous stout processes. Aptea attadalica (Cookson and Eisenack 1962), from the Apto-?Albian of Australia, is most similar but possesses a wide distinctive cingulum and usually a ventral furrow.
Aptea securigera, Davey and Verdier, 1974, p.642–643, pl.91, figs.2–3; text-fig.5(vii).
Holotype: Davey and Verdier, 1974, pl.91, fig.3.
Originally Aptea, subsequently Pseudoceratium.
Taxonomic senior synonym: Circulodinium distinctum, according to Fensome et al., (2019a, p.37). Fensome et al. based the synonymy on the morphology of the holotype only.
Age: early Aptian.
Locus typicus: La BÚdoule, SE-France
---------------------------------------------------------------------------------------------------
Original description: Davey and Verdier 1974, p. 642-643
Diagnosis:
The cyst central body is dorso-ventrally flattened and rounded triangular in shape. The left side is strongly, but evenly, convex; the right epitractal and hypotractal sides are slightly convex to straight and meet at approximately right angles in the cingular region. The right hypotractal side often has a medial convexity. The apex and, to a lesser extent, the antapex are developed as protuberances of the central body and are rounded distally. The cyst surface bears numerous short, flattened, solid processes which are concentrated in the circumferential region. A more or less circular area in the centre of the ventral and dorsal surfaces is devoid of, or possesses only rare, processes. The processes are of variable shape but are typically discrete, expanding both distally and proximally, and are flat-topped distally; their length is more than twice as their medial width. The processes are longer and more variable at the cyst apices. Very rarely the cingulum and other tabulation is marked by narrow bands devoid of processes. The archaeopyle is apical and possesses a strongly zigzag margin. The operculum is usually detached.
Description:
The processes characteristically widen both distally and proximally. Very rarely, narrow processes may bifurcate or trifurcate, or neighbouring processes may be linked medially by a crest. Rarely the bases of two or three neighbouring processes may be linked by a low ridge or thickening of the cyst wall. These thickenings tend to parallel the cyst sides, as do the crests in A. polymorpha. Besides the longer processes at the cyst apices, slightly longer ones may also be present on the left side in the cingular region and on the convexity or bulge, if present, of the right hypotractal side. These longer processes were seen to be linked distally in one specimen.
Dimensions:
Central body length: 73-90 µm; Central body width: 69-87 µm; Central body length (operculum detached): 62-73 µm; Height of processes: 2-10 µm.
Affinities:
Aptea securigera is differentiated from Aptea polymorpha by the absence of well-developed crests and from Aptea eisenacki (Davey 1969) by the presence of numerous stout processes. Aptea attadalica (Cookson and Eisenack 1962), from the Apto-?Albian of Australia, is most similar but possesses a wide distinctive cingulum and usually a ventral furrow.