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Hystrichodinium polycheirum
From Fensome et al., 2019:
Hystrichodinium polycheirum Heilmann-Clausen in Heilmann-Clausen and Thomsen, 1995, p.297–298, pl.11, figs.6–12; text-fig.16. Holotype: Heilmann-Clausen and Thomsen, 1995, pl.11, figs.7–8; text-fig.16. Age: late Barremian.
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Original Diagnosis: Heilmann-Clausen and Thomsen 1995, p. 297-298
A skolochorate dinoflagellate cyst. The central body is rounded-biconical or eggshaped. The periphragm is almost smooth, sometimes ornamented with hollow tubercles. A narrow cingulum bordered by low, simple septa is present in an equatorial position. Other paraplate boundaries are occasionally marked by indistinct, low ridges. The processes are situated in polar positions; 3-7 processes occur anterior to the precingular paraplates and between 4 and 11 processes occur posterior to the postcingular paraplates. They appear to be placed in parasutural positions. Rarely a single reduced process has been seen ventrally, near the posterior margin of the paracingulum. The processes are flat and ribbonlike. The breadth may exceed 10 µm. Distally the processes split into 4-11 blunt-tipped fingers of almost equal length. Most of the processes may thereby resemble arms with hands. The archaeopyle is precingular, type P (3").
Dimensions of holotype: Central body length 48 µm, breadth 50 µm, length of pericyst 86 µm.
Dimensions of measured specimens: Central body length: 48 (52) 54 µm Central body breadth: 36 (48) 55 µm Length of pericyst: 86 (92) 101 µm Length of processes: 16-31 µm, (6 specimens measured)
Comparison: The flexible, ribbon-like process-shafts in H. polycheirum show that it is phylogenetically related to other species in the genus Hystrichodinium. H. oligacanthum DEFLANDRE & COOKSON, 1955 and H. ? amphiacanthum COOKSON & EISENACK, 1958 have a similar distribution of the processes, but their processes are simple, without "fingers". The occasionally occurring hollow tubercles on the central body resemble those in Hystrichodinium pulchrum.
Hystrichodinium polycheirum Heilmann-Clausen in Heilmann-Clausen and Thomsen, 1995, p.297–298, pl.11, figs.6–12; text-fig.16. Holotype: Heilmann-Clausen and Thomsen, 1995, pl.11, figs.7–8; text-fig.16. Age: late Barremian.
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Original Diagnosis: Heilmann-Clausen and Thomsen 1995, p. 297-298
A skolochorate dinoflagellate cyst. The central body is rounded-biconical or eggshaped. The periphragm is almost smooth, sometimes ornamented with hollow tubercles. A narrow cingulum bordered by low, simple septa is present in an equatorial position. Other paraplate boundaries are occasionally marked by indistinct, low ridges. The processes are situated in polar positions; 3-7 processes occur anterior to the precingular paraplates and between 4 and 11 processes occur posterior to the postcingular paraplates. They appear to be placed in parasutural positions. Rarely a single reduced process has been seen ventrally, near the posterior margin of the paracingulum. The processes are flat and ribbonlike. The breadth may exceed 10 µm. Distally the processes split into 4-11 blunt-tipped fingers of almost equal length. Most of the processes may thereby resemble arms with hands. The archaeopyle is precingular, type P (3").
Dimensions of holotype: Central body length 48 µm, breadth 50 µm, length of pericyst 86 µm.
Dimensions of measured specimens: Central body length: 48 (52) 54 µm Central body breadth: 36 (48) 55 µm Length of pericyst: 86 (92) 101 µm Length of processes: 16-31 µm, (6 specimens measured)
Comparison: The flexible, ribbon-like process-shafts in H. polycheirum show that it is phylogenetically related to other species in the genus Hystrichodinium. H. oligacanthum DEFLANDRE & COOKSON, 1955 and H. ? amphiacanthum COOKSON & EISENACK, 1958 have a similar distribution of the processes, but their processes are simple, without "fingers". The occasionally occurring hollow tubercles on the central body resemble those in Hystrichodinium pulchrum.