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Caspidinium
From Williams et al., 2017:
[Caspidinium, Marret et al., 2004, p. 7-9.
Type species: Caspidinium rugosum, Marret et al., 2004 (pl.1, figs. 1-5)]
Type locality: Recent sediments from the Southern Caspian
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Original description: [Marret et al., 2004]:
Diagnosis:
Proximate cyst with ventral S-type gonyaulacacean paratabulation, dextral torsion and low, coarse intratabular ornamentation. Cyst ambitus subspherical, slightly cruciform, and reniform in apical view. Epicyst smaller than the hypocyst. Endophragm and periphragm appressed. Sulcal paratabulation is indistinguishable. Archeopyle is precingular (3″) with free operculum.
Second diagnosis:
Proximate gonyaulacacean cyst with S-type ventral paratabulation expressed by low and broad parasutural septa and dextral torsion. Subspherical to slightly cruciform cyst ambitus, and reniform shape in apical view. Epicyst smaller than the hypocyst. The endophragm and periphragm are appressed to form a relatively thick wall layer (1.5 µm). Low parasutural septa and a coarsely rugulate to papillate intratabular ornamentation. Precingular archeopyle (3'') of iso-camerate shape and free operculum.
Description:
In equatorial view, the cyst has a subspherical to slightly cruciform shape with the epicyst being smaller and more conical than the hypocyst and more conical. In apical view, the cyst is reniform, with a concave ventral region. The epicyst has a rounded apex, with no apical horn or boss and the hypocyst has a flat antapex. In lateral view, the hypocyst is more expanded in the ventral region (Plate 1: 8-9). Ornamentation on the wall surface is highly variable, from coarsely papillate, verrucate to rugulate.
Endophragm and periphragm are appressed and form a relatively thick wall layer (ca 1.5 µm).
The S-type gonyaulacacean paratabulation (4', 6'', 6c, ?6''', 1p, 1'''') is expressed by low and pronounced parasutural septa formed by a thickening of the periphragm but differs in having dextral torsion (Plate 1: 5, 8; Fig. 3A). The plates marked by * (Fig. 3A-C) are considered as homologues of the standard gonyaulacacean paratabulation (Fensome et al., 1993). The coarse papillate to rugulate ornamentation in the ventral region obscures the sulcal and lateral paratabulation (Plate 1: 1-2). Paraplate 2' is smaller than paraplate 3', and the junction of paraplates 1'' and 2'' is a third along the boundary with paraplate 1' (Fig. 3C). The contact between paraplates 4' and 6'' is short.
The archeopyle is precingular (3''), broad, iso-camerate shape and always free.
Most specimens are transparent to yellow in light microscopic observation. There is a high variability in the ornamentation of Caspidinium rugosum and some specimens are characterised by very coarse rugulation and low intratabular relief with indistinct parasutural septa. The only clear characteristic of the paratabulation is the precingular archeopyle (3'') and paraplate 4'''. These specimens were counted apart as it is possible that this morphological variation could relate to particular environmental conditions (see Table 2).
Dimensions:
Holotype (Plate 1:1-5): body length = 48 µm; body width = 43 µm; thickness of the cyst wall = 1.5 µm.
Average measurements on 8 specimens: body length = 45–(52)–60 µm; body width = 45–(52)– 60 µm.
Due to poorly orientation, and often broken specimens but few complete specimens, it was not possible to obtain extensive measurements.
Remarks:
The number (4) and arrangement of apical plates, together with a S-type paratabulation may indicate a gonyaulacoidean affiliation, although the dextral torsion suggests a possible affinity with the Cribroperidinoideae.
Affinities/Comments and comparisons:
In the ventral region, the parasutural septa and surface relief merge, which obscures the sulcal and lateral paratabulation. Furthermore, specimens were often broken, or not well oriented for studying the sulcal area. Caspidinium rugosum differs from species of Impagidinium and Corrudinium species by its characteristic dextral torsion, and from Cribroperidinium species by the S-type paratabulation. The species differs from Gonyaulax apiculata (Evitt et al., 1985) in having 6 precingular paraplates so that the dextral torsion differs. In Gonyaulax apiculata, the 3c/4c suture is below paraplate 3" whereas it is situated under paraplate 4" in Caspidinium rugosum. Furthermore, in the apex region, Caspidinium rugosum has no apical boss and has a marked suture between paraplates 1' and 2'.
[Caspidinium, Marret et al., 2004, p. 7-9.
Type species: Caspidinium rugosum, Marret et al., 2004 (pl.1, figs. 1-5)]
Type locality: Recent sediments from the Southern Caspian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Marret et al., 2004]:
Diagnosis:
Proximate cyst with ventral S-type gonyaulacacean paratabulation, dextral torsion and low, coarse intratabular ornamentation. Cyst ambitus subspherical, slightly cruciform, and reniform in apical view. Epicyst smaller than the hypocyst. Endophragm and periphragm appressed. Sulcal paratabulation is indistinguishable. Archeopyle is precingular (3″) with free operculum.
Second diagnosis:
Proximate gonyaulacacean cyst with S-type ventral paratabulation expressed by low and broad parasutural septa and dextral torsion. Subspherical to slightly cruciform cyst ambitus, and reniform shape in apical view. Epicyst smaller than the hypocyst. The endophragm and periphragm are appressed to form a relatively thick wall layer (1.5 µm). Low parasutural septa and a coarsely rugulate to papillate intratabular ornamentation. Precingular archeopyle (3'') of iso-camerate shape and free operculum.
Description:
In equatorial view, the cyst has a subspherical to slightly cruciform shape with the epicyst being smaller and more conical than the hypocyst and more conical. In apical view, the cyst is reniform, with a concave ventral region. The epicyst has a rounded apex, with no apical horn or boss and the hypocyst has a flat antapex. In lateral view, the hypocyst is more expanded in the ventral region (Plate 1: 8-9). Ornamentation on the wall surface is highly variable, from coarsely papillate, verrucate to rugulate.
Endophragm and periphragm are appressed and form a relatively thick wall layer (ca 1.5 µm).
The S-type gonyaulacacean paratabulation (4', 6'', 6c, ?6''', 1p, 1'''') is expressed by low and pronounced parasutural septa formed by a thickening of the periphragm but differs in having dextral torsion (Plate 1: 5, 8; Fig. 3A). The plates marked by * (Fig. 3A-C) are considered as homologues of the standard gonyaulacacean paratabulation (Fensome et al., 1993). The coarse papillate to rugulate ornamentation in the ventral region obscures the sulcal and lateral paratabulation (Plate 1: 1-2). Paraplate 2' is smaller than paraplate 3', and the junction of paraplates 1'' and 2'' is a third along the boundary with paraplate 1' (Fig. 3C). The contact between paraplates 4' and 6'' is short.
The archeopyle is precingular (3''), broad, iso-camerate shape and always free.
Most specimens are transparent to yellow in light microscopic observation. There is a high variability in the ornamentation of Caspidinium rugosum and some specimens are characterised by very coarse rugulation and low intratabular relief with indistinct parasutural septa. The only clear characteristic of the paratabulation is the precingular archeopyle (3'') and paraplate 4'''. These specimens were counted apart as it is possible that this morphological variation could relate to particular environmental conditions (see Table 2).
Dimensions:
Holotype (Plate 1:1-5): body length = 48 µm; body width = 43 µm; thickness of the cyst wall = 1.5 µm.
Average measurements on 8 specimens: body length = 45–(52)–60 µm; body width = 45–(52)– 60 µm.
Due to poorly orientation, and often broken specimens but few complete specimens, it was not possible to obtain extensive measurements.
Remarks:
The number (4) and arrangement of apical plates, together with a S-type paratabulation may indicate a gonyaulacoidean affiliation, although the dextral torsion suggests a possible affinity with the Cribroperidinoideae.
Affinities/Comments and comparisons:
In the ventral region, the parasutural septa and surface relief merge, which obscures the sulcal and lateral paratabulation. Furthermore, specimens were often broken, or not well oriented for studying the sulcal area. Caspidinium rugosum differs from species of Impagidinium and Corrudinium species by its characteristic dextral torsion, and from Cribroperidinium species by the S-type paratabulation. The species differs from Gonyaulax apiculata (Evitt et al., 1985) in having 6 precingular paraplates so that the dextral torsion differs. In Gonyaulax apiculata, the 3c/4c suture is below paraplate 3" whereas it is situated under paraplate 4" in Caspidinium rugosum. Furthermore, in the apex region, Caspidinium rugosum has no apical boss and has a marked suture between paraplates 1' and 2'.