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Lagenadinium scarburghense
Lagenadinium scarburghense (Sarjeant, 1961a, p.111, pl.15, figs.12–13) Piel, 1985, p.112. Emendation: Stover et al., 1977, p.333, as Stephanelytron scarburghense.
Now Stephanelytron. Originally (and now) Stephanelytron, subsequently Lagenadinium. Riding, 1987, retained this species in Stephanelytron Sarjeant, 1961.
Holotype: Sarjeant, 1961, pl.15, figs.12-13
Age: Early Oxfordian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Stephanelytron scarburghense Sarjeant, 1961a, emend. Stover et al., 1977. As emended by Stover et al. (1977, p.333), cysts proximochorate, spheroidal to broadly ovoidal body two-layered; autophragm smooth, up to 1 µm thick, and forming numerous nontabular processes. Processes tubiform, normally expanded proximally and more so distally, smooth, 5-8 µm long, 1um to about 2 µm wide at midlength, tips of adjacent processes frequently connected distally. Processes and intervening areas covered by a thin (<0.5 µm), smooth ectophragm whose distance from underlying autophragm is essentially uniform. Paratabulation not expressed. Archeopyle apical, outline of archeopyle and shape of operculum unknown. Operculum apparently has many nontabular processes (exact number uncertain). Antapical area with one, or occasionally two, coronas; base of corona thicker than autophragm, densely setate, and convex distally; walls smooth, rim commonly thickened distally, distal diameter greater than proximal diameter. On forms with two coronas, the antapical corona is generally the larger. Size; overall length 41-60 µm.
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Original diagnosis: Sarjeant 1961, p. 111
A species of Stephanelytron having a spherical to oval shell, not granular or punctate, bearing tubes similar in character and distribution to those of S. redcliffense but with in addition further tubes of similar character distributed in an irregular scatter within the fields delimited by these tube rows. The everted lips of the tubes in the rows overlap to some extent, giving an appearance of linkage. The corona or coronas have a surrounding membrane striated in similar fashion to that of S. redcliffense: however, the membrane slopes regularly outwards instead of having a distinctly everted lip.
Original description: Sarjeant 1961, p. 111
Whereas a11 other specimens seen of this genus have a single large corona, as does the type of S. scarburghense, one specimen seen (SC2/33/6) has two smaller coronas. situated together on the antapical surface. In the character of these coronas and in the type and distribution of tubes this specimen corresponds to S. scarburghense and it has therefore been attributed to this species, the drawing of a varietal distinction not being considered warranted in view of the absence of knowledge of the character and functions of the corona.
Dimensions. Holotype: overall length 4Á, overall breadth 30Á (oblique view). Specimen SC2/31/12, seen in lateral view, gives more satisfactory dimensions (overall length 45Á, breadth 40Á, corona 12Á high and 28Á in outer diameter, tubes about 5Á in length) but was unfortunately damaged. These dimensions appear typical.
Remarks: Sarjeant 1961, p. 111
This species, typical of the lowest Oxford Clay, is proportionately more abundant than the species of Stephanelytron of the higher horizons. Broken specimens are relatively numerous, an estimated thirty to fifty being seen, but only five relatively complete specimens were noted. The character of the corona and tubes suggests a closer relation to S. redcliffense than to S. caytonense, so that no evolutionary sequence can be postulated satisfactorily.
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Emended description: Stover et al 1977, p. 333
Cysts proximochorate, spheroidal to broadly ovoidal, body two-layered; autophragm smooth, up to 1,L thick, and forming numerous nontabular processes. Processes tubiform, normally expanded proximally and more so distally, smooth, 5Á to 8Á long, 1Á to about 2Á wide at midlength, tips of adjacent processes frequently connected distally. Processes and intervening areas covered by a thin (<0.5Á), smooth ectophragm whose distance from underlying autophragm is essentially uniform. Paratabulation not expressed. Archeopyle apical. outline of archeopyle and shape of operculum unknown; operculum apparently has many nontabular processes (exact number uncertain). Antapical area with one, or occasionally two, coronas; base of corona thicker than autophragm, densely setate, and convex distally; walls smooth, rim commonly thickened distally, distal diameter
greater than proximal diameter. On forms with two coronas, the antapical corona is generally the larger. Overall length 41Á to 60Á.
Now Stephanelytron. Originally (and now) Stephanelytron, subsequently Lagenadinium. Riding, 1987, retained this species in Stephanelytron Sarjeant, 1961.
Holotype: Sarjeant, 1961, pl.15, figs.12-13
Age: Early Oxfordian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Stephanelytron scarburghense Sarjeant, 1961a, emend. Stover et al., 1977. As emended by Stover et al. (1977, p.333), cysts proximochorate, spheroidal to broadly ovoidal body two-layered; autophragm smooth, up to 1 µm thick, and forming numerous nontabular processes. Processes tubiform, normally expanded proximally and more so distally, smooth, 5-8 µm long, 1um to about 2 µm wide at midlength, tips of adjacent processes frequently connected distally. Processes and intervening areas covered by a thin (<0.5 µm), smooth ectophragm whose distance from underlying autophragm is essentially uniform. Paratabulation not expressed. Archeopyle apical, outline of archeopyle and shape of operculum unknown. Operculum apparently has many nontabular processes (exact number uncertain). Antapical area with one, or occasionally two, coronas; base of corona thicker than autophragm, densely setate, and convex distally; walls smooth, rim commonly thickened distally, distal diameter greater than proximal diameter. On forms with two coronas, the antapical corona is generally the larger. Size; overall length 41-60 µm.
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Original diagnosis: Sarjeant 1961, p. 111
A species of Stephanelytron having a spherical to oval shell, not granular or punctate, bearing tubes similar in character and distribution to those of S. redcliffense but with in addition further tubes of similar character distributed in an irregular scatter within the fields delimited by these tube rows. The everted lips of the tubes in the rows overlap to some extent, giving an appearance of linkage. The corona or coronas have a surrounding membrane striated in similar fashion to that of S. redcliffense: however, the membrane slopes regularly outwards instead of having a distinctly everted lip.
Original description: Sarjeant 1961, p. 111
Whereas a11 other specimens seen of this genus have a single large corona, as does the type of S. scarburghense, one specimen seen (SC2/33/6) has two smaller coronas. situated together on the antapical surface. In the character of these coronas and in the type and distribution of tubes this specimen corresponds to S. scarburghense and it has therefore been attributed to this species, the drawing of a varietal distinction not being considered warranted in view of the absence of knowledge of the character and functions of the corona.
Dimensions. Holotype: overall length 4Á, overall breadth 30Á (oblique view). Specimen SC2/31/12, seen in lateral view, gives more satisfactory dimensions (overall length 45Á, breadth 40Á, corona 12Á high and 28Á in outer diameter, tubes about 5Á in length) but was unfortunately damaged. These dimensions appear typical.
Remarks: Sarjeant 1961, p. 111
This species, typical of the lowest Oxford Clay, is proportionately more abundant than the species of Stephanelytron of the higher horizons. Broken specimens are relatively numerous, an estimated thirty to fifty being seen, but only five relatively complete specimens were noted. The character of the corona and tubes suggests a closer relation to S. redcliffense than to S. caytonense, so that no evolutionary sequence can be postulated satisfactorily.
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Emended description: Stover et al 1977, p. 333
Cysts proximochorate, spheroidal to broadly ovoidal, body two-layered; autophragm smooth, up to 1,L thick, and forming numerous nontabular processes. Processes tubiform, normally expanded proximally and more so distally, smooth, 5Á to 8Á long, 1Á to about 2Á wide at midlength, tips of adjacent processes frequently connected distally. Processes and intervening areas covered by a thin (<0.5Á), smooth ectophragm whose distance from underlying autophragm is essentially uniform. Paratabulation not expressed. Archeopyle apical. outline of archeopyle and shape of operculum unknown; operculum apparently has many nontabular processes (exact number uncertain). Antapical area with one, or occasionally two, coronas; base of corona thicker than autophragm, densely setate, and convex distally; walls smooth, rim commonly thickened distally, distal diameter
greater than proximal diameter. On forms with two coronas, the antapical corona is generally the larger. Overall length 41Á to 60Á.