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Stephanelytron caytonense
Stephanelytron caytonense Sarjeant, 1961a, p.110, pl.15, fig.16; text-fig.11. Emendation: Stover et al., 1977, p.332.
Holotype: Sarjeant, 1961, pl.15, fig.16, text-fig.11
Locus typicus: Cayton Bay, Yorkshire, England.
Stratum typicum: Oxford Clay of High Red Cliff, 25 feet above top of the underlying Hackness Rock, Jurassic (Oxfordian; Cardioceras cordatum Zone).
Age: Early Oxfordian
Original diagnosis: Sarjeant 1961a, p. 110
A species of Stephanelytron having a spherical to oval shell, not granular or punctate, bearing rows of tubes similar in distribution to those of S. redcliffense but with lips less pronouncedly everted and having about eight to ten rows of perforations aligned parallel to the length of the tube and quite closely spaced. The corona has a relatively small base and flares out widely; its membrane is somewhat folded, with a coarsely granular surface and a distinct outer lip devoid of granulation.
Dimensions. The holotype has a somewhat damaged shell: its overall dimensions, Length 65 µm and breadth 60 µm, probably do not therefore reflect its true shape. The corona is 17 µm high, its outer diameter is 25 µm, its basal diameter about 14 µm. The tubes are around 8 µm in length.
Remarks. The single specimen found of this species was the only representative of the genus noted at this horizon However, its perforate tubes and the character of its corona afford a ready distinction from all other specimens of the genus and warrant specific status.
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Emended description: Stover et al. 1977, p. 332-333
Cysts proximochorate, subspherical to broadly ellipsoidal, outline may be roundly angular. Autophragm up to 1µ thick, smooth, and forming relatively few processes arranged in ill-defined rows. Processes tubiform, normally expanded proximally and distally, commonly finely perforate, 6 µm to 11 µm long, from 1 µm to nearly 2 µm wide at midlength, and tips of adjacent processes rarely connected. Processes, corona, and intervening areas covered by thin (<0.5µm) ectophragm that is smooth, generally entire, whose distance above underlying autophragm is essentially constant. Paratabulation usually not expressed (due to scarcity of processes) or, at best, vaguely indicated: paracingulum not indicated. Archeopyle apical, outline of archeopyle and shape of operculum unknown; the latter appears to bear a single, wider-than-usual process. Antapical corona with thick, densely setate, antapically convex base and smooth walls; distal diameter slightly to much greater than proximal diameter. Overall length 41 µm to 66 µm.
Remarks: Stephanelytron caytonense seems to be intergradational with S. redcliffense. However, they do not always occur together and their total ranges differ; consequently, both species are retained.
Holotype: Sarjeant, 1961, pl.15, fig.16, text-fig.11
Locus typicus: Cayton Bay, Yorkshire, England.
Stratum typicum: Oxford Clay of High Red Cliff, 25 feet above top of the underlying Hackness Rock, Jurassic (Oxfordian; Cardioceras cordatum Zone).
Age: Early Oxfordian
Original diagnosis: Sarjeant 1961a, p. 110
A species of Stephanelytron having a spherical to oval shell, not granular or punctate, bearing rows of tubes similar in distribution to those of S. redcliffense but with lips less pronouncedly everted and having about eight to ten rows of perforations aligned parallel to the length of the tube and quite closely spaced. The corona has a relatively small base and flares out widely; its membrane is somewhat folded, with a coarsely granular surface and a distinct outer lip devoid of granulation.
Dimensions. The holotype has a somewhat damaged shell: its overall dimensions, Length 65 µm and breadth 60 µm, probably do not therefore reflect its true shape. The corona is 17 µm high, its outer diameter is 25 µm, its basal diameter about 14 µm. The tubes are around 8 µm in length.
Remarks. The single specimen found of this species was the only representative of the genus noted at this horizon However, its perforate tubes and the character of its corona afford a ready distinction from all other specimens of the genus and warrant specific status.
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Emended description: Stover et al. 1977, p. 332-333
Cysts proximochorate, subspherical to broadly ellipsoidal, outline may be roundly angular. Autophragm up to 1µ thick, smooth, and forming relatively few processes arranged in ill-defined rows. Processes tubiform, normally expanded proximally and distally, commonly finely perforate, 6 µm to 11 µm long, from 1 µm to nearly 2 µm wide at midlength, and tips of adjacent processes rarely connected. Processes, corona, and intervening areas covered by thin (<0.5µm) ectophragm that is smooth, generally entire, whose distance above underlying autophragm is essentially constant. Paratabulation usually not expressed (due to scarcity of processes) or, at best, vaguely indicated: paracingulum not indicated. Archeopyle apical, outline of archeopyle and shape of operculum unknown; the latter appears to bear a single, wider-than-usual process. Antapical corona with thick, densely setate, antapically convex base and smooth walls; distal diameter slightly to much greater than proximal diameter. Overall length 41 µm to 66 µm.
Remarks: Stephanelytron caytonense seems to be intergradational with S. redcliffense. However, they do not always occur together and their total ranges differ; consequently, both species are retained.