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Nyktericysta vitrea
Nyktericysta? vitrea (Duxbury, 1983) Bint, 1986
Originally Australisphaera, subsequently (and now) Nyktericysta?.
At the time of the transfer, Bint, 1986, questionably included this species in Nyktericysta.
Holotype: Duxbury, 1983, pl.2, fig.11, text-fig.8
Locus typicus: Isle of Wight, England
Stratum typicum: Early Aptian
Original diagnosis: Duxbury, 1983, p. 26-27: Australisphaera vitrea
A fairly thick-walled dinoflagellate cyst species bearing two lateral horns and one or two antapical horns. The lateral horns are short and broad and display a paracingular notch at their distal extremes. Short, posteriorly-directed, digitate projections extend from below the lateral post-paracingular margins and these are hollow and taper to sharp points. One large, conical, left antapical horn is always present and a right antapical horn is sometimes indicated by a very low protuberance. The single body layer is glassy in appearance and is covered by granular ornament which is particularly concentrated at the extremes of the horns. In the case of the antapical horns, coarse ornament is present in the position of the right antapical, whether the wall protrudes at that point or not. The archeopyle is apical.
Observed Dimensions: Holotype - 67 x 90 µm. Operculum detached - 75 (64) 55 x 90 (70) 58 µm.
Affinities:
Duxbury, 1983, p. 27: Australisphaera vitrea
The fairly thick, vitreous nature of the wall and the distinctive granular ornament renders A. vitrea an easily recogniseable species. Although Australisphaera verrucosa, the type species, bears low, positive ornament which may include large tubercules restricted to the lateral and antapical regions, the granular body ornament of A. vitrea is more irregularly distributed and attains considerable height at the distal extremes of the horns. Also, the lateral horns of A. verrucosa, when formed, are distally blunt and lack the characteristic hollow,sharply tapering, posteriorly-directed projections so characteristic of A. vitrea.
Originally Australisphaera, subsequently (and now) Nyktericysta?.
At the time of the transfer, Bint, 1986, questionably included this species in Nyktericysta.
Holotype: Duxbury, 1983, pl.2, fig.11, text-fig.8
Locus typicus: Isle of Wight, England
Stratum typicum: Early Aptian
Original diagnosis: Duxbury, 1983, p. 26-27: Australisphaera vitrea
A fairly thick-walled dinoflagellate cyst species bearing two lateral horns and one or two antapical horns. The lateral horns are short and broad and display a paracingular notch at their distal extremes. Short, posteriorly-directed, digitate projections extend from below the lateral post-paracingular margins and these are hollow and taper to sharp points. One large, conical, left antapical horn is always present and a right antapical horn is sometimes indicated by a very low protuberance. The single body layer is glassy in appearance and is covered by granular ornament which is particularly concentrated at the extremes of the horns. In the case of the antapical horns, coarse ornament is present in the position of the right antapical, whether the wall protrudes at that point or not. The archeopyle is apical.
Observed Dimensions: Holotype - 67 x 90 µm. Operculum detached - 75 (64) 55 x 90 (70) 58 µm.
Affinities:
Duxbury, 1983, p. 27: Australisphaera vitrea
The fairly thick, vitreous nature of the wall and the distinctive granular ornament renders A. vitrea an easily recogniseable species. Although Australisphaera verrucosa, the type species, bears low, positive ornament which may include large tubercules restricted to the lateral and antapical regions, the granular body ornament of A. vitrea is more irregularly distributed and attains considerable height at the distal extremes of the horns. Also, the lateral horns of A. verrucosa, when formed, are distally blunt and lack the characteristic hollow,sharply tapering, posteriorly-directed projections so characteristic of A. vitrea.