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Palaeocystodinium hampdenense
Palaeocystodinium hampdenense (Wilson, 1977) Wrenn and Hart, 1988
Originally Svalbardella, subsequently (and now) Palaeocystodinium.
Holotype: Wilson, 1977, figs.1-3
Locus typicus: Hampden Formation, Hampden Beach North Otago, New Zealand
Stratum typicum: Bartonian, Middle Eocene
Original diagnosis: Wilson, 1977, p.564: Svalbardella hampdenensis
A relatively elongate Svalbardella with gently tapering horns, distally subrounded, the apical horn always being the longer of the two; there is no sharp division between the horns and the remainder of the pericyst. Periphragm thin, microreticulate, sometimes feebly striate, with cingulum and sulcus typically visible. Archeopyle hexa intercalary, attenuated in pericyst; operculum free.
Dimensions: Holotype: overall length 207 µm, breadth 42 µm, length of endocyst 58 µm, breadth 40 µm; length of apical horn 91 µm, antapical horn 58 µm. Range of 10 complete specimens; overall length 184(209)234 µm, breadth 33(39)44 µm; length of endocyst 55(63)72 µm, breadth 31(37)42 µm; length of apical horn 69(84)91 µm, antapical horn 50(62)77 µm.
Original description: Wilson, 1977, p.564: Svalbardella hampdenensis
The epipericyst is longer and narrower, especially in the distal part, than the hypopericyst and the apical horn is typically about 30% longer than the antapical horn. A pericingulum is consistently present and is represented by faint parallel lines enclosing a smooth area (breadth 4-5 µm) which is more firmly apparent on the dorsal surface than the ventral; the pericingulum is normally planar or occasionally slightly helicoidal. A narrow sulcus is normally present on the hypopericyst and does not extend to the epipericyst. The archeopyle is fairly large, attenuated in the pericyst (holotype: length 30 µm, breadth 19 µm); much less attenuated in endocyst (holotype: length 19 µm, breadth 19 µm); the endoperculum is correspondingly shorter than the perioperculum and is closely attached to it only in the lower part. The endocyst is broadly elongate ovoidal with relatively flat polar margins; the endophragm is typically denser and thicker than the periphragm. Both the periphragm and endophragm are microreticulate, and the reticulation pattern, particularly on the proximal part of the horns, sometimes suggests a longitudinal striation. No definite signs of a tabulation were observed.
Affinities:
Wilson, 1977, p.566: Svalbardella hampdenensis
Svalbardella hampdenensis differs from the type species, S. cooksoniae Manum, in being more elongate and in having narrower unequal horns. Furthermore, the suggestion of paratabulation present in S. cooksoniae was not observed in any of the specimens of S. hampdenensis.
The overall morphology of S. hampdenensis is intermediate between the genera Svalbardella and Palaeocystodinium as redefined by Lentin and Williams (1975). In particular the blunt horns, lack of sharp division between the horns and the rest of the pericyst, and the constant presence of a cingulum are typical of Svalbardella, whereas the relatively long, distally narrow horns and the lack of any paratabulation are more typically associated with Palaeocystodinium. The distinctions between the two genera have never been very marked nor well established, despite the detailed review by Lentin and Williams (1975), and the existence of an intermediate species strengthens the case for discarding Palaeocystodinium (see Evitt 1967, p. 37).
Originally Svalbardella, subsequently (and now) Palaeocystodinium.
Holotype: Wilson, 1977, figs.1-3
Locus typicus: Hampden Formation, Hampden Beach North Otago, New Zealand
Stratum typicum: Bartonian, Middle Eocene
Original diagnosis: Wilson, 1977, p.564: Svalbardella hampdenensis
A relatively elongate Svalbardella with gently tapering horns, distally subrounded, the apical horn always being the longer of the two; there is no sharp division between the horns and the remainder of the pericyst. Periphragm thin, microreticulate, sometimes feebly striate, with cingulum and sulcus typically visible. Archeopyle hexa intercalary, attenuated in pericyst; operculum free.
Dimensions: Holotype: overall length 207 µm, breadth 42 µm, length of endocyst 58 µm, breadth 40 µm; length of apical horn 91 µm, antapical horn 58 µm. Range of 10 complete specimens; overall length 184(209)234 µm, breadth 33(39)44 µm; length of endocyst 55(63)72 µm, breadth 31(37)42 µm; length of apical horn 69(84)91 µm, antapical horn 50(62)77 µm.
Original description: Wilson, 1977, p.564: Svalbardella hampdenensis
The epipericyst is longer and narrower, especially in the distal part, than the hypopericyst and the apical horn is typically about 30% longer than the antapical horn. A pericingulum is consistently present and is represented by faint parallel lines enclosing a smooth area (breadth 4-5 µm) which is more firmly apparent on the dorsal surface than the ventral; the pericingulum is normally planar or occasionally slightly helicoidal. A narrow sulcus is normally present on the hypopericyst and does not extend to the epipericyst. The archeopyle is fairly large, attenuated in the pericyst (holotype: length 30 µm, breadth 19 µm); much less attenuated in endocyst (holotype: length 19 µm, breadth 19 µm); the endoperculum is correspondingly shorter than the perioperculum and is closely attached to it only in the lower part. The endocyst is broadly elongate ovoidal with relatively flat polar margins; the endophragm is typically denser and thicker than the periphragm. Both the periphragm and endophragm are microreticulate, and the reticulation pattern, particularly on the proximal part of the horns, sometimes suggests a longitudinal striation. No definite signs of a tabulation were observed.
Affinities:
Wilson, 1977, p.566: Svalbardella hampdenensis
Svalbardella hampdenensis differs from the type species, S. cooksoniae Manum, in being more elongate and in having narrower unequal horns. Furthermore, the suggestion of paratabulation present in S. cooksoniae was not observed in any of the specimens of S. hampdenensis.
The overall morphology of S. hampdenensis is intermediate between the genera Svalbardella and Palaeocystodinium as redefined by Lentin and Williams (1975). In particular the blunt horns, lack of sharp division between the horns and the rest of the pericyst, and the constant presence of a cingulum are typical of Svalbardella, whereas the relatively long, distally narrow horns and the lack of any paratabulation are more typically associated with Palaeocystodinium. The distinctions between the two genera have never been very marked nor well established, despite the detailed review by Lentin and Williams (1975), and the existence of an intermediate species strengthens the case for discarding Palaeocystodinium (see Evitt 1967, p. 37).