Back
Conicoidium
From Fensome et al., 2019:
"Conicoidium", Jiabo, 1978, p.45–46.
Emendation Xu Jinli and Mao Shaozhi, 1989, p.302.
Taxonomic senior synonym: Parabohaidina, according to Sun Xuekun (1994, p.80).
He Chengquan et al. (2009, p.465) considered this taxon to be a subgenus of Parabohaidina, Parabohaidina subgenus Conicoidium, which see. Chen et al. (1988, p.15) and Fensome et al. (1990, p.153) included this genus in the acritarchs; however, Xu Jinli and Mao Shaozhi (1989, p.302) showed that it is a dinoflagellate.
Type: Jiabo, 1978, pl.18, fig.7, as Conicoidium tuberculatum.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Jiabo, 1978]: (Translation: Chen et al., 1988, p. 15):
Description:
Cyst broadly conical, outline oblate quadrangular to subtriangular. There are one or two folds in the equatorial area, but no indications of equatorial prominences, a paracingulum, a parasulcus, an archaeopyle, or an endocyst. Nor is there usually an apical protrusion. Surface smooth, granulate, rugulate or tuberculate, variable from species to species. A nucleus-like spot is often visible.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Chen et al., 1988, p. 15:
Remarks:
Features indicative of dinoflagellate affinity such as the archeopyle, paracingulum, parasulcus, or peridinioid outline, are lacking in this genus. Therefore, we regard it as an acritarch.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Xu Jinli and Mao Shaozhi, 1989: (Provisional translation by GSC: courtesy R. Fensome)
Diagnosis:
Cyst broad conical to subspherical, with a rounded apex and an almost degenerated hypotract. Girdle projections obscure or absent completely. One to two pieces of girdle folds generally developed. No indications of cingulum, sulcus and central body. Wall autophragm, about 1 µm thick, its surface smooth or ornamented with granules, rugae or verrucae of non-tabular arrangement. Archeopyle probably combination of tAa+3Ia type (Fig. 7), opercula compound. Cysts small in size.
Affinities:
In most specimens observed sutures between apical and precingular series, and between neighbouring intercalary plates distinctly show, but all of apical and intercalary plates keep attached to the cyst. In such case 3I archeopyle type may be interpreted for this genus. However, its close relationship to Parabohaidina and its co-occurrence with both Parabohaidina and Bohaidina suggest its similar archeopyle type to the latter two genera.
Conicoidium differs from Prominangularia in being broad conical to subspherical in shape with convex posterior edge while in Prominangularia the cyst shape is subtriangular with concave posterior edge, and the girdle projections are better developed than in the present genus.
"Conicoidium", Jiabo, 1978, p.45–46.
Emendation Xu Jinli and Mao Shaozhi, 1989, p.302.
Taxonomic senior synonym: Parabohaidina, according to Sun Xuekun (1994, p.80).
He Chengquan et al. (2009, p.465) considered this taxon to be a subgenus of Parabohaidina, Parabohaidina subgenus Conicoidium, which see. Chen et al. (1988, p.15) and Fensome et al. (1990, p.153) included this genus in the acritarchs; however, Xu Jinli and Mao Shaozhi (1989, p.302) showed that it is a dinoflagellate.
Type: Jiabo, 1978, pl.18, fig.7, as Conicoidium tuberculatum.
---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Jiabo, 1978]: (Translation: Chen et al., 1988, p. 15):
Description:
Cyst broadly conical, outline oblate quadrangular to subtriangular. There are one or two folds in the equatorial area, but no indications of equatorial prominences, a paracingulum, a parasulcus, an archaeopyle, or an endocyst. Nor is there usually an apical protrusion. Surface smooth, granulate, rugulate or tuberculate, variable from species to species. A nucleus-like spot is often visible.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Chen et al., 1988, p. 15:
Remarks:
Features indicative of dinoflagellate affinity such as the archeopyle, paracingulum, parasulcus, or peridinioid outline, are lacking in this genus. Therefore, we regard it as an acritarch.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Xu Jinli and Mao Shaozhi, 1989: (Provisional translation by GSC: courtesy R. Fensome)
Diagnosis:
Cyst broad conical to subspherical, with a rounded apex and an almost degenerated hypotract. Girdle projections obscure or absent completely. One to two pieces of girdle folds generally developed. No indications of cingulum, sulcus and central body. Wall autophragm, about 1 µm thick, its surface smooth or ornamented with granules, rugae or verrucae of non-tabular arrangement. Archeopyle probably combination of tAa+3Ia type (Fig. 7), opercula compound. Cysts small in size.
Affinities:
In most specimens observed sutures between apical and precingular series, and between neighbouring intercalary plates distinctly show, but all of apical and intercalary plates keep attached to the cyst. In such case 3I archeopyle type may be interpreted for this genus. However, its close relationship to Parabohaidina and its co-occurrence with both Parabohaidina and Bohaidina suggest its similar archeopyle type to the latter two genera.
Conicoidium differs from Prominangularia in being broad conical to subspherical in shape with convex posterior edge while in Prominangularia the cyst shape is subtriangular with concave posterior edge, and the girdle projections are better developed than in the present genus.