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Lejeunecysta attenuata
Lejeunecysta attenuata Clowes et al., 2016, p.72–75, figs.6a–l.
Holotype: Clowes et al., figs.6a–c.
Age: Oligocene.
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Original description (Clowes et al., 2016):
Lejeunecysta attenuata n. sp. Fig. 6a-l
?1975 cf. Muderongia sp.; Kemp, p. 605, pl. 4, fig. 13
1999 Lejeunecysta sp. 7; Cape Roberts Science Team, table 5.8, fig. 5.8g
2000 Lejeunecysta sp. 7; Hannah et al., fig.2, 5b–c
2000a Lejeunecysta sp. 7; Cape Roberts Science Team, p. 155, table 5.4
2001 Lejeunecysta sp. 7; Hannah, Wilson & Wrenn, fig. 1
2001 Lejeunecysta sp. 7; Hannah, Wrenn & Wilson, table 1
Description: Shape: Elongate pentagonal with epicyst generally somewhat longer than hypocyst. The sides of the epicyst and hypocyst are concave. The apex is pointed whereas the antapex is blunt with a relatively narrow flat base. The ambitus broadens steeply at the cingulum. Phragma: Autophragm thin, pale, smooth, usually with scattered folds, wrinkles, or lineations. Horns: The apical horn is relatively long and tapered whereas the antapical horns are scarcely developed and represented usually by a solid papilla at each end of the flat base approximately 20 μm wide. Archeopyle: Intercalary, 2a, difficult to observe in our specimens; apparently narrow and elongate, assumed to be stenodeltaform. Operculum usually in place. Tabulation: Indicated only by the archeopyle, cingulum, and sometimes a visible sulcus. Cingulum: Fairly prominent and marked by a somewhat smooth membranous fold or folds in the autophragm on both the dorsal and ventral surfaces. Sulcus: Marked on the ventral surface by a break in the cingular fold and usually bordered by a faint lineation (e.g., Fig. 6b-c).
Dimensions: Length 103–127 μm, width 46–78 μm (range of 6 specimens).
Comparison: This species is distinguished from other described species chiefly by its elongate attenuated shape, concave margins, and narrow blunt antapex.
Reported Stratigraphic Occurrence at Cape Roberts: 16.81 mbsf in CRP-3 to 464.98 mbsf (not 575.36 mbsf as reported, e.g., in Cape Roberts Science Team, 1999) in CRP-2A; 683.58 m to 510.40 m in the composite section; Cymatiosphaera robertsii Zone; Oligocene. The base of ‘Zone C′ of Hannah et al. (2001a) is defined by the first appearances of Lejeunecysta sp. 7 (= Lejeunecysta attenuata) and Lejeunecysta sp. 9 (= Lejeunecysta katatonos) which are depicted (on their fig. 1) as appearing together at the base of CRP-2A. The published data used herein, however, indicates that the two taxa first appear in CRP-3, some 200 m apart.
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Holotype: Clowes et al., figs.6a–c.
Age: Oligocene.
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Original description (Clowes et al., 2016):
Lejeunecysta attenuata n. sp. Fig. 6a-l
?1975 cf. Muderongia sp.; Kemp, p. 605, pl. 4, fig. 13
1999 Lejeunecysta sp. 7; Cape Roberts Science Team, table 5.8, fig. 5.8g
2000 Lejeunecysta sp. 7; Hannah et al., fig.2, 5b–c
2000a Lejeunecysta sp. 7; Cape Roberts Science Team, p. 155, table 5.4
2001 Lejeunecysta sp. 7; Hannah, Wilson & Wrenn, fig. 1
2001 Lejeunecysta sp. 7; Hannah, Wrenn & Wilson, table 1
Description: Shape: Elongate pentagonal with epicyst generally somewhat longer than hypocyst. The sides of the epicyst and hypocyst are concave. The apex is pointed whereas the antapex is blunt with a relatively narrow flat base. The ambitus broadens steeply at the cingulum. Phragma: Autophragm thin, pale, smooth, usually with scattered folds, wrinkles, or lineations. Horns: The apical horn is relatively long and tapered whereas the antapical horns are scarcely developed and represented usually by a solid papilla at each end of the flat base approximately 20 μm wide. Archeopyle: Intercalary, 2a, difficult to observe in our specimens; apparently narrow and elongate, assumed to be stenodeltaform. Operculum usually in place. Tabulation: Indicated only by the archeopyle, cingulum, and sometimes a visible sulcus. Cingulum: Fairly prominent and marked by a somewhat smooth membranous fold or folds in the autophragm on both the dorsal and ventral surfaces. Sulcus: Marked on the ventral surface by a break in the cingular fold and usually bordered by a faint lineation (e.g., Fig. 6b-c).
Dimensions: Length 103–127 μm, width 46–78 μm (range of 6 specimens).
Comparison: This species is distinguished from other described species chiefly by its elongate attenuated shape, concave margins, and narrow blunt antapex.
Reported Stratigraphic Occurrence at Cape Roberts: 16.81 mbsf in CRP-3 to 464.98 mbsf (not 575.36 mbsf as reported, e.g., in Cape Roberts Science Team, 1999) in CRP-2A; 683.58 m to 510.40 m in the composite section; Cymatiosphaera robertsii Zone; Oligocene. The base of ‘Zone C′ of Hannah et al. (2001a) is defined by the first appearances of Lejeunecysta sp. 7 (= Lejeunecysta attenuata) and Lejeunecysta sp. 9 (= Lejeunecysta katatonos) which are depicted (on their fig. 1) as appearing together at the base of CRP-2A. The published data used herein, however, indicates that the two taxa first appear in CRP-3, some 200 m apart.
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