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Palleodinium
Type species: Palleodinium digitatum n. sp.
Derivation of Name: From the Latin palleo, to be pale – in reference to its characteristic delicate, thin-walled nature.
Diagnosis: Small, pear-shaped to elongate ovoidal dinocysts bearing a small number of long, solid spines restricted to circum- polar areas. The surface is smooth to very finely granular and the spines are produced into fine, complexly-ramifying distal terminations. No clear archeopyle but common breakage suggests that it is apical. Minor concavity might suggest the position of an otherwise undefined cingulum. No tabulation is expressed.
Remarks: This genus is so far represented by a single, essentially featureless species which is distinguished by its pear-shaped body and circum-polar distribution of the small number of solid spines. Some breakage at the apex is assumed to represent the archeopyle, but because of the tapering epicyst of most specimens of this very small form, this has proved impossible to fully interpret in transmitted light.
Nohr-Hansen (1993, p. 47-50) emended the description of the prolate genus Bourkidinium Morgan 1985, citing, "long, hollow, tubular processes which are restricted to the apex (reflecting apical, or apical and precingular plate-series) and antapex (reflecting antapical, or maybe antapical, postcingular and sulcal plate-series). The equatorial zone is wide and devoid of processes". This differs from Palleodinium since the latter has primary spines only on what are assumed to be the precingular and postcingular series. Also, the spines of Palleodinium are solid and distally ramify into a complex network whereas the processes of Bourkidinium are hollow and distally flared with entire margins.
Derivation of Name: From the Latin palleo, to be pale – in reference to its characteristic delicate, thin-walled nature.
Diagnosis: Small, pear-shaped to elongate ovoidal dinocysts bearing a small number of long, solid spines restricted to circum- polar areas. The surface is smooth to very finely granular and the spines are produced into fine, complexly-ramifying distal terminations. No clear archeopyle but common breakage suggests that it is apical. Minor concavity might suggest the position of an otherwise undefined cingulum. No tabulation is expressed.
Remarks: This genus is so far represented by a single, essentially featureless species which is distinguished by its pear-shaped body and circum-polar distribution of the small number of solid spines. Some breakage at the apex is assumed to represent the archeopyle, but because of the tapering epicyst of most specimens of this very small form, this has proved impossible to fully interpret in transmitted light.
Nohr-Hansen (1993, p. 47-50) emended the description of the prolate genus Bourkidinium Morgan 1985, citing, "long, hollow, tubular processes which are restricted to the apex (reflecting apical, or apical and precingular plate-series) and antapex (reflecting antapical, or maybe antapical, postcingular and sulcal plate-series). The equatorial zone is wide and devoid of processes". This differs from Palleodinium since the latter has primary spines only on what are assumed to be the precingular and postcingular series. Also, the spines of Palleodinium are solid and distally ramify into a complex network whereas the processes of Bourkidinium are hollow and distally flared with entire margins.