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Exiguisphaera plectilis
Exiguisphaera plectilis Duxbury, 1980; emend. Jan du Chene et al., 1986
Holotype: Duxbury, 1980, pl.3, figs.5, 8; Jan du Chene et al., 1986(1), pl.35, figs.10-12; Jan du Chene et al., 1986(2), pl.28, figs.5-9
Paratype: Duxbury, 1980, pl.3, fig.11
Locus typicus: Speeton Clay, Speeton, England
Stratum typicum: Barremian
Translation Jan du Chene et al., 1986: LPP
Original diagnosis: Duxbury, 1980, p.118-119
A thick-walled, spheroidal dinoflagellate cyst whose surface is distinctly microperforate. Paratabulation typical for the genus is outlined by fairly high parasutural crests. These crests are distally entire, widely fenestrate and composed of single, solid strands which furcate and fuse between the proximal
and distal crestal margins in a complicated manner. Slender, intratabular spines are usually present and are equal in height to the parasutural crests. The archeopyle is dorsal in position and formed by detachment of two precingular paraplates.
Observed Dimensions: Holotype 64x67 Ám. Overall 81(69)61x81(70)61 Ám.
Emended description: Jan du Chene et al., 1986, p. 12
Cyst proximochorate, acavate, subspherical and without apical protrusion. The paratabulation, probably gonyaulacoid, is difficult to discern because it is accentuated by composite parasutural septa of an alignment of solid processes, irregularly interconnected at the proximal and distal extremities. The autophragm shows a vacuolar structure which is expressed on the surface by very fine punctuations. Spines, as high as the parasutural septa, are irregularly distributed on the intratabular areas. The archaeopyle is precingular, type 2P (3""+4""). The operculum is free and composite.
Affinities:
Duxbury, 1980, p. 119: This is a very distinctive species which differs from Exiguisphaera phragma Duxbury (1979) in several respects. The body wall of E. plectilis is much thicker and less prone to folding than that of E. phragma. Also, E. plectilis bears the higher and more complex parasutural crests and is generally larger than E. phragma. Due to the spheroidal shape of E. plectilis and the consequent random orientation of observed specimens, it is rare to see the two-paraplate precingular archeopyle as well displayed as it is in the holotype. Never-theless, the other characteristics of this species render it easily recognisable.
Jan du Chene et al., 1986: This species differs from E. phragma in the height and complexity of the parasutural septa.
Holotype: Duxbury, 1980, pl.3, figs.5, 8; Jan du Chene et al., 1986(1), pl.35, figs.10-12; Jan du Chene et al., 1986(2), pl.28, figs.5-9
Paratype: Duxbury, 1980, pl.3, fig.11
Locus typicus: Speeton Clay, Speeton, England
Stratum typicum: Barremian
Translation Jan du Chene et al., 1986: LPP
Original diagnosis: Duxbury, 1980, p.118-119
A thick-walled, spheroidal dinoflagellate cyst whose surface is distinctly microperforate. Paratabulation typical for the genus is outlined by fairly high parasutural crests. These crests are distally entire, widely fenestrate and composed of single, solid strands which furcate and fuse between the proximal
and distal crestal margins in a complicated manner. Slender, intratabular spines are usually present and are equal in height to the parasutural crests. The archeopyle is dorsal in position and formed by detachment of two precingular paraplates.
Observed Dimensions: Holotype 64x67 Ám. Overall 81(69)61x81(70)61 Ám.
Emended description: Jan du Chene et al., 1986, p. 12
Cyst proximochorate, acavate, subspherical and without apical protrusion. The paratabulation, probably gonyaulacoid, is difficult to discern because it is accentuated by composite parasutural septa of an alignment of solid processes, irregularly interconnected at the proximal and distal extremities. The autophragm shows a vacuolar structure which is expressed on the surface by very fine punctuations. Spines, as high as the parasutural septa, are irregularly distributed on the intratabular areas. The archaeopyle is precingular, type 2P (3""+4""). The operculum is free and composite.
Affinities:
Duxbury, 1980, p. 119: This is a very distinctive species which differs from Exiguisphaera phragma Duxbury (1979) in several respects. The body wall of E. plectilis is much thicker and less prone to folding than that of E. phragma. Also, E. plectilis bears the higher and more complex parasutural crests and is generally larger than E. phragma. Due to the spheroidal shape of E. plectilis and the consequent random orientation of observed specimens, it is rare to see the two-paraplate precingular archeopyle as well displayed as it is in the holotype. Never-theless, the other characteristics of this species render it easily recognisable.
Jan du Chene et al., 1986: This species differs from E. phragma in the height and complexity of the parasutural septa.