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Stephanelytron redcliffense
Stephanelytron *redcliffense Sarjeant, 1961a, p.109–110, pl.15, fig.11; text-fig.10. Emendation: Stover et al., 1977, p.331–332; Fauconnier and Masure, 2004, pl.73, fig.3.
Holotype: Sarjeant, 1961a, pl.15, fig.11; text-fig.10; Fensome et al., 1995, figs.1–4 — p.1731.
Age: early Oxfordian.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999
Stephanelytron redcliffense Sarjeant, 1961a, emend. Stover et al., 1977. According to Stover et al. (1977, p.331-332), the tabulation is indicated by parasutural alignment of processes. There is a single process occurs at or near the centre of the operculum. Base of corona may have scattered longer setae or spinules. Processes tubiform, normally expanded slightly proximally, more so distally, smooth 5-9 µm long and 1-4 µm wide at midpoint. Distal tips of adjacent processes may be connected. S. caytonense is gradational to this species. S. caytonense differs in having a more nearly circular outline and processes that are commonly perforate.
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Sarjeant 1961, p.109-110
Original diagnosis: A species of Stephanelytron having an oval shell, neither granular nor perforate, bearing six rows of tubular processes extending from the apex to the corona, a transverse row of tubular processes extending arouns the apex in a broad circle, and a further row of processes, incomplete in all specimens seen, surrounding the antapex close to the base of the corona. The processes have everted lips and their walls are not perforate. All specimens seen had a single corona, broad-based and bearing striations.
Original description: The surrounding membrane of the corona seems to show a somewhat thickened lip on to which the striations do not extend. The matted fibers within seem to vary in length, with those ate the center longer than those at the fringes, but this appearance may result entirely from the curvature of the shell surface from which they arise.
Emended description: Stover et al. 1977, p.331-332
Cysts proximochorate, subellipsoidal; outline tends to be roundly polygonal. Autophragm up to 1 µm thick, smooth to faintly granulate, from which arise parasutural rows of processes. Processes tubiform, normally expanded slightly proximally, more so distally, smooth, 5-9 µm long and from 1 to about 4 mm diameter at midlength; distal tips of adjacent processes may be connected. Processes and intervening areas covered by ectophragm that is laevigate, thin (<0.5 µm), commonly wrinkled and may be incomplete or even lacking; distance between autophragm and ectophragm essentially uniform. Paratabulation indicated by parasutural alignment of processes, formula: 1', 5'', Xc, 5''', 1'''', 2s. Precingular and postcingular paraplates large and with more or less rectangular outlines, although their exact shapes are difficult to verify because of folding and compression. A paracingulum is expressed only by the transverse alignment of groups of processes at about midlegth. Archaeopyle apical, operculum normally free. Archaeopyle outline and shape of operculum unknown; however, a single process (often wider than others on the cyst) occurs apparently at or near the center of the operculum; hence the designation of 1' in the paratabulation formula. Smooth-walled corona situated within antapical paraplate and covered by ectophragm; outline of corona in apical-antapical view subcircular to subquadrabgular, distal diameter greater than proximal diameter; base of corona relatively thick, convex antapically, composed of compact mass of setae, and may have scattered longer setae or spinules. Overall length 40-75 µm without opercula.
Remarks: the distal rim of the corona may be thickened slightly, and on some specimens the proximal diameter of the corona may approximate the distal diameter.
Affinities:
Stover et al. 1977, p.333: 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, 1961a, pl.15, fig.11; text-fig.10; Fensome et al., 1995, figs.1–4 — p.1731.
Age: early Oxfordian.
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999
Stephanelytron redcliffense Sarjeant, 1961a, emend. Stover et al., 1977. According to Stover et al. (1977, p.331-332), the tabulation is indicated by parasutural alignment of processes. There is a single process occurs at or near the centre of the operculum. Base of corona may have scattered longer setae or spinules. Processes tubiform, normally expanded slightly proximally, more so distally, smooth 5-9 µm long and 1-4 µm wide at midpoint. Distal tips of adjacent processes may be connected. S. caytonense is gradational to this species. S. caytonense differs in having a more nearly circular outline and processes that are commonly perforate.
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Sarjeant 1961, p.109-110
Original diagnosis: A species of Stephanelytron having an oval shell, neither granular nor perforate, bearing six rows of tubular processes extending from the apex to the corona, a transverse row of tubular processes extending arouns the apex in a broad circle, and a further row of processes, incomplete in all specimens seen, surrounding the antapex close to the base of the corona. The processes have everted lips and their walls are not perforate. All specimens seen had a single corona, broad-based and bearing striations.
Original description: The surrounding membrane of the corona seems to show a somewhat thickened lip on to which the striations do not extend. The matted fibers within seem to vary in length, with those ate the center longer than those at the fringes, but this appearance may result entirely from the curvature of the shell surface from which they arise.
Emended description: Stover et al. 1977, p.331-332
Cysts proximochorate, subellipsoidal; outline tends to be roundly polygonal. Autophragm up to 1 µm thick, smooth to faintly granulate, from which arise parasutural rows of processes. Processes tubiform, normally expanded slightly proximally, more so distally, smooth, 5-9 µm long and from 1 to about 4 mm diameter at midlength; distal tips of adjacent processes may be connected. Processes and intervening areas covered by ectophragm that is laevigate, thin (<0.5 µm), commonly wrinkled and may be incomplete or even lacking; distance between autophragm and ectophragm essentially uniform. Paratabulation indicated by parasutural alignment of processes, formula: 1', 5'', Xc, 5''', 1'''', 2s. Precingular and postcingular paraplates large and with more or less rectangular outlines, although their exact shapes are difficult to verify because of folding and compression. A paracingulum is expressed only by the transverse alignment of groups of processes at about midlegth. Archaeopyle apical, operculum normally free. Archaeopyle outline and shape of operculum unknown; however, a single process (often wider than others on the cyst) occurs apparently at or near the center of the operculum; hence the designation of 1' in the paratabulation formula. Smooth-walled corona situated within antapical paraplate and covered by ectophragm; outline of corona in apical-antapical view subcircular to subquadrabgular, distal diameter greater than proximal diameter; base of corona relatively thick, convex antapically, composed of compact mass of setae, and may have scattered longer setae or spinules. Overall length 40-75 µm without opercula.
Remarks: the distal rim of the corona may be thickened slightly, and on some specimens the proximal diameter of the corona may approximate the distal diameter.
Affinities:
Stover et al. 1977, p.333: 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.