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Sentusidinium myriatrichum
Sentusidinium myriatrichum Fensome, 1979
Now Pilosidinium. Originally Sentusidinium, subsequently (and now) Pilosidinium.
Holotype: Fensome 1979, pl.2, fig.7; text-fig.5A
Locus typicus: Hareelv Formation, south side of Langryggen, Greenland
Stratum typicum: Oxfordian-Kimmeridgian
Original diagnosis: Fensome, 1979, p. 12-13
A species of Sentusidinium myriatrichum a spheroidal to subspheroidal cyst covered with very numerous (about 1000) fine, simple hairs which are approximately one fiftieth of the cyst breadth in length. Distribution of the ornament is continuous. giving no indication of furrows or paratabulation. The cyst ¿ all is thin and often appears to be densely granular. the true nature of the hairs being apparent only at the margin of the cyst.
Dimensions: Holotype: Iength including attached operculum 55 µm, Iength excluding operculum 4 2 µm breadth 48 µm. Range: Iength including perculum 55-59 µm. Iength without or excluding operculum 42 (48) 49 µm, breadth 45 (51) 59 µm.
Original description: Fensome, 1979, p. 13
S. myriatrichum is characterized by its dense covering of very short, fine hairs. The nature of the ornament can be seen clearly only at the margin of the specimen; in plan view the ornament often resembles a dense granulation. The distal ends of most of the hairs appear to be simple. although some may have expanded tips; this feature is difficult to discern with the light microscope owing to their small size. The hairs have bulbous bases. The ornament is continuous and regularly distributed over the cyst surface; there is no indication of furrows or a paratabulation except at the archeopyle margin, which is deeply notched along the parasutures of the parasulcus and six precingular paraplates. The operculum of the holotype remains attached, probably at the parasulcus; however, in the majority of the specimens observed the operculum was completely detached. The cyst wall is thin and thus tends to be folded. The ambitus is ovoidal to subspheroidal and, when the operculum is detached, the cyst breadth is greater than its length.
Affinities:
Fensome, 1979, p. 13: In its possession of abundant short hairs S. myriatrichum is unlike any previously described species of Sentusidinium. Sentusidinium sp. A. of Fensome, herein, and Sentusidinium sp. B of Fensome, herein, also possess numerous very short appendages. Sentusidinium sp. A is much smaller, however, and the morphology of its archeopyle is very different from that of S. myriatrichum. Sentusidinillm sp. B is more similar in shape and size, but has a very thick, rigid cyst wall and is thus readily differentiated from S. myriatrichum.
Now Pilosidinium. Originally Sentusidinium, subsequently (and now) Pilosidinium.
Holotype: Fensome 1979, pl.2, fig.7; text-fig.5A
Locus typicus: Hareelv Formation, south side of Langryggen, Greenland
Stratum typicum: Oxfordian-Kimmeridgian
Original diagnosis: Fensome, 1979, p. 12-13
A species of Sentusidinium myriatrichum a spheroidal to subspheroidal cyst covered with very numerous (about 1000) fine, simple hairs which are approximately one fiftieth of the cyst breadth in length. Distribution of the ornament is continuous. giving no indication of furrows or paratabulation. The cyst ¿ all is thin and often appears to be densely granular. the true nature of the hairs being apparent only at the margin of the cyst.
Dimensions: Holotype: Iength including attached operculum 55 µm, Iength excluding operculum 4 2 µm breadth 48 µm. Range: Iength including perculum 55-59 µm. Iength without or excluding operculum 42 (48) 49 µm, breadth 45 (51) 59 µm.
Original description: Fensome, 1979, p. 13
S. myriatrichum is characterized by its dense covering of very short, fine hairs. The nature of the ornament can be seen clearly only at the margin of the specimen; in plan view the ornament often resembles a dense granulation. The distal ends of most of the hairs appear to be simple. although some may have expanded tips; this feature is difficult to discern with the light microscope owing to their small size. The hairs have bulbous bases. The ornament is continuous and regularly distributed over the cyst surface; there is no indication of furrows or a paratabulation except at the archeopyle margin, which is deeply notched along the parasutures of the parasulcus and six precingular paraplates. The operculum of the holotype remains attached, probably at the parasulcus; however, in the majority of the specimens observed the operculum was completely detached. The cyst wall is thin and thus tends to be folded. The ambitus is ovoidal to subspheroidal and, when the operculum is detached, the cyst breadth is greater than its length.
Affinities:
Fensome, 1979, p. 13: In its possession of abundant short hairs S. myriatrichum is unlike any previously described species of Sentusidinium. Sentusidinium sp. A. of Fensome, herein, and Sentusidinium sp. B of Fensome, herein, also possess numerous very short appendages. Sentusidinium sp. A is much smaller, however, and the morphology of its archeopyle is very different from that of S. myriatrichum. Sentusidinillm sp. B is more similar in shape and size, but has a very thick, rigid cyst wall and is thus readily differentiated from S. myriatrichum.