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Sentusidinium pelionense
Sentusidinium pelionense Fensome, 1979
Now Barbatacysta. Originally Sentusidinium, subsequently (and now) Barbatacysta.
Holotype: Fensome 1979, pl.1, fig.5,7; text-fig. 5B
Locus typicus: between GÕseleev and Hareelev, Greenland
Stratum typicum: Bajocian-Bathonian
Original diagnosis: Fensome, 1979, p. 13-14
A species of dinoflagellate with an ovoidal, thin-walled cyst, of which the breadth is usually or constantly greater than the length. The antapex is gently rounded. The apex is usually or constantly lost in archeopyle formation. The archeopyle margin is usually, but not consistently deeply notched by accessory archeopyle sutures at the parasulcus and at the parasutures between six precingular paraplates. The paracingulum is weakly to moderately well indicated by slight depressions in the cyst surface, or by lines or clumps of granules which may be coarser than those elsewhere on the cyst wall. There is no other indication of paratabulation on the cyst surface. The general ornamentation of the cyst wall usually consists of a very sparse scatter of tubercles or verrucae of variable size; between verrucae the cyst surface is granular, the granules being variable in size and irregular in distribution. The granules may line up or join to produce low narrow ridges of variable length which. in extreme cases, produce a continuous reticulum. The archeopyle margin tends to have fewer accessory archeopyle sutures in specimens with a reticulate surface ornament.
Dimensions: Holotype; length 48 µm, breadth 60 µm. Paratypes; (i) length 56 µm, breadth 78 µm; (ii) length 49 µm, breadth 69 µm. Range; length 39(51)60 µm, breadth 52(63)78 µm.
Affinities:
Fensome, 1979, p. 14-15: S. pelionense is distinguished from all other species of Sentusidinium by the nature of its ornamentation. Most species of Sentusidinium possess spines. S. verrucosum (Sarjeant, 1968) is much more densely verrucate and S? atlanticum (Habib, 1972) is smaller and minutely granular. In the low relief of its ornamentation S. pelionense also resembles species of the genus Chytroeisphaeridia. However, no species of Chytroeisphaeridia possess verrucae. Because of its possession of verrucae, an often relatively distinct paracingulum and usually, deep accessory archeopyle sutures, this species was allocated to Sentusidinium rather than to Chytroeisphaeridia.
The holotype possesses the irregularly granular surface ornamentation which is typical for this species. Paratype (i) has a reticulate pattern on its cyst wall; paratype (ii) possesses an intermediate type of ornamentation. Both paratypes possess fewer accessory archeopyle sutures than is typical for the species.
Apart from the variation of its general surface ornamentation, this species is characterized by a thin, often folded cyst wall and the consistent occurrence of sparsely distributed, very coarse granules or verrucae which stand out clearly from the general ornamentation of the cyst wall. A close-up of the cyst surface of the holotype showing several verrucae is shown in Plate 1, fig. 7.
Now Barbatacysta. Originally Sentusidinium, subsequently (and now) Barbatacysta.
Holotype: Fensome 1979, pl.1, fig.5,7; text-fig. 5B
Locus typicus: between GÕseleev and Hareelev, Greenland
Stratum typicum: Bajocian-Bathonian
Original diagnosis: Fensome, 1979, p. 13-14
A species of dinoflagellate with an ovoidal, thin-walled cyst, of which the breadth is usually or constantly greater than the length. The antapex is gently rounded. The apex is usually or constantly lost in archeopyle formation. The archeopyle margin is usually, but not consistently deeply notched by accessory archeopyle sutures at the parasulcus and at the parasutures between six precingular paraplates. The paracingulum is weakly to moderately well indicated by slight depressions in the cyst surface, or by lines or clumps of granules which may be coarser than those elsewhere on the cyst wall. There is no other indication of paratabulation on the cyst surface. The general ornamentation of the cyst wall usually consists of a very sparse scatter of tubercles or verrucae of variable size; between verrucae the cyst surface is granular, the granules being variable in size and irregular in distribution. The granules may line up or join to produce low narrow ridges of variable length which. in extreme cases, produce a continuous reticulum. The archeopyle margin tends to have fewer accessory archeopyle sutures in specimens with a reticulate surface ornament.
Dimensions: Holotype; length 48 µm, breadth 60 µm. Paratypes; (i) length 56 µm, breadth 78 µm; (ii) length 49 µm, breadth 69 µm. Range; length 39(51)60 µm, breadth 52(63)78 µm.
Affinities:
Fensome, 1979, p. 14-15: S. pelionense is distinguished from all other species of Sentusidinium by the nature of its ornamentation. Most species of Sentusidinium possess spines. S. verrucosum (Sarjeant, 1968) is much more densely verrucate and S? atlanticum (Habib, 1972) is smaller and minutely granular. In the low relief of its ornamentation S. pelionense also resembles species of the genus Chytroeisphaeridia. However, no species of Chytroeisphaeridia possess verrucae. Because of its possession of verrucae, an often relatively distinct paracingulum and usually, deep accessory archeopyle sutures, this species was allocated to Sentusidinium rather than to Chytroeisphaeridia.
The holotype possesses the irregularly granular surface ornamentation which is typical for this species. Paratype (i) has a reticulate pattern on its cyst wall; paratype (ii) possesses an intermediate type of ornamentation. Both paratypes possess fewer accessory archeopyle sutures than is typical for the species.
Apart from the variation of its general surface ornamentation, this species is characterized by a thin, often folded cyst wall and the consistent occurrence of sparsely distributed, very coarse granules or verrucae which stand out clearly from the general ornamentation of the cyst wall. A close-up of the cyst surface of the holotype showing several verrucae is shown in Plate 1, fig. 7.