Back
Spongodinium obscurum
From Fensome et al., 2019:
Spongodinium obscurum (Manum and Cookson, 1964, p.21–22, pl.4, figs.5–6) Fensome et al. 2016b, p.69. Holotype: Manum and Cookson, 1964, pl.4, fig.6. Originally Scriniodinium, subsequently Scriniodinium?, thirdly Endoscrinium, fourthly (and now) Spongodinium. Age: Late Cretaceous.
---------------------------------------------------------------------------------------------------
Original description: Manum and Cookson, 1964, p. 21-22
Theca roughly quadrangular in outline, w ith a short, broad, and blunt apical projection, divided by an indistinct, equatorial girdle which is best seen as broad prominences at the lateral margins. The theca contains a large capsule of circular outline. The theca-membrane and the wall of the capsule are separated by a space of varying width, in some places they are closely opposed, in others, particularly at the apex and antapex, and the equator, widely separated.
The theca-membrane is very thin, indistinctly dotted, and much folded. There are no distinct connections running between the capsule and the theca, but fine, irregular lines, the true nature of which is obscured by the many folds, may possibly represent supporting fibrils. The wall of the capsule is up to 1 Ám thick and sometimes indistinctly dotted. A large precingular archeopyle has been observed.
Dimensions: Holotype: 137 x 117 Ám. Range: length 122-137 Ám, width 104-124 Ám.
Affinities:
Manum and Cookson, 1964, p. 21: Scriniodinium obscurum has been a constantly recurring form in the Graham Island preparations. Most of the specimes are Iying sideways but the few seen in dorsoventral view seem to come closest to S. playfordi Cookson and Eisenack (1960) from the Upper Jurassic of Western Australia. However, S. obscurum appears to be distinct from that species in its wider and more folded theca-membrane, the variation in the width of the space separating the theca from the capsule, the more circular outline of the capsule and its lack of a distinct surface pattern.
---------------------------------------------------------------------------------------------------
Remarks Fensome et al., 2016b:
Remarks. As demonstrated by Ioannides (1986, plates 5–8), intergradation exists between Spongodinium (as Endoscrinium) obscurum, Spongodinium grossum (as Chlamydophorella grossa) and a taxon that he called Spongodinium sp. In their description of Endoscrinium obscurum, Manum & Cookson (1964, p. 21) stated: “There are no distinct connections running between the capsule and the theca, but fine, irregular lines, the true nature of which is obscured by the many folds, may possibly represent supporting fibrils. The wall of the capsule is up to 1 μm thick and sometimes indistinctly dotted.” The comments of Manum & Cookson (1964) and Ioannides (1986), together with observations in this study, indicate that the species should be assigned to Spongodinium, and that the wall is best considered a complex autophragm, rather than being holocavate.
Spongodinium obscurum (Manum and Cookson, 1964, p.21–22, pl.4, figs.5–6) Fensome et al. 2016b, p.69. Holotype: Manum and Cookson, 1964, pl.4, fig.6. Originally Scriniodinium, subsequently Scriniodinium?, thirdly Endoscrinium, fourthly (and now) Spongodinium. Age: Late Cretaceous.
---------------------------------------------------------------------------------------------------
Original description: Manum and Cookson, 1964, p. 21-22
Theca roughly quadrangular in outline, w ith a short, broad, and blunt apical projection, divided by an indistinct, equatorial girdle which is best seen as broad prominences at the lateral margins. The theca contains a large capsule of circular outline. The theca-membrane and the wall of the capsule are separated by a space of varying width, in some places they are closely opposed, in others, particularly at the apex and antapex, and the equator, widely separated.
The theca-membrane is very thin, indistinctly dotted, and much folded. There are no distinct connections running between the capsule and the theca, but fine, irregular lines, the true nature of which is obscured by the many folds, may possibly represent supporting fibrils. The wall of the capsule is up to 1 Ám thick and sometimes indistinctly dotted. A large precingular archeopyle has been observed.
Dimensions: Holotype: 137 x 117 Ám. Range: length 122-137 Ám, width 104-124 Ám.
Affinities:
Manum and Cookson, 1964, p. 21: Scriniodinium obscurum has been a constantly recurring form in the Graham Island preparations. Most of the specimes are Iying sideways but the few seen in dorsoventral view seem to come closest to S. playfordi Cookson and Eisenack (1960) from the Upper Jurassic of Western Australia. However, S. obscurum appears to be distinct from that species in its wider and more folded theca-membrane, the variation in the width of the space separating the theca from the capsule, the more circular outline of the capsule and its lack of a distinct surface pattern.
---------------------------------------------------------------------------------------------------
Remarks Fensome et al., 2016b:
Remarks. As demonstrated by Ioannides (1986, plates 5–8), intergradation exists between Spongodinium (as Endoscrinium) obscurum, Spongodinium grossum (as Chlamydophorella grossa) and a taxon that he called Spongodinium sp. In their description of Endoscrinium obscurum, Manum & Cookson (1964, p. 21) stated: “There are no distinct connections running between the capsule and the theca, but fine, irregular lines, the true nature of which is obscured by the many folds, may possibly represent supporting fibrils. The wall of the capsule is up to 1 μm thick and sometimes indistinctly dotted.” The comments of Manum & Cookson (1964) and Ioannides (1986), together with observations in this study, indicate that the species should be assigned to Spongodinium, and that the wall is best considered a complex autophragm, rather than being holocavate.