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Lejeunecysta rotunda
Lejeunecysta rotunda Clowes et al., 2016, p.77–78, figs.9a–l.
Holotype: Clowes et al., figs.9a–c.
Age: Oligocene.
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Original description (Clowes et al., 2016):
Lejeunecysta rotunda n. sp. Fig. 9a–l
1999 Lejeunecysta sp. 5; Cape Roberts Science Team, table 5.8, fig. 5.8c
2000a Lejeunecysta sp. 5; Cape Roberts Science Team, p. 155, table 5.4, fig.5.7f–g
2000 Lejeunecysta sp. 5; Hannah et al., fig.2, 4f–g
2001 Lejeunecysta sp. 5; Hannah, Wilson & Wrenn, fig. 1
2001 Lejeunecysta sp. 5; Hannah, Wrenn & Wilson, table 1
Description: Shape: Subcircular to elliptical or sub-pentagonal. Epicyst sides are convex, whereas those of the hypocyst are slightly concave to convex. Phragma: The thin autophragm (<1.0 μm) is scabrate to verrucate, with sculptural elements ranging in size from 1 to 2 μm both in diameter and elevation above the cyst surface. Subcircular sculptural elements appear postulate on some specimens. Horns: Short, well rounded, and broad-based apical and antapical horns are usually present, but may be so poorly developed that the cysts are nearly circular in shape. Dark papilla may be present on tip of each horn. Archeopyle: Intercalary, 2a, iso- to slightly eurydeltaform. The operculum may be free but is commonly present, often only slightly displaced from the archeopyle. Tabulation: Indicated only by the archeopyle, cingulum, and sometimes a visible sulcus. Cingulum: Partially delineated by aligned sculptural elements and short folds in the cyst wall. Sulcus: The margin of the sulcus is marked by folds in the autophragm, a shallow antapical concavity between the antapical horns, and a shallow depression on the ventral surface of the hypocyst. A comma- or loop-shaped flagellar scar may be evident on the sulcus.
Dimensions: Length 60 (80) 95 μm, width 65 (78) 90 μm; archeopyle length 12–15 μm, width 19–27 μm (range of 13 specimens).
Comparison: The species is characterised by its generally well rounded, rotund outline, poorly developed apical and antapical horns, and distinctive scabrate to verrucate or pustulate surface sculpture. Lejeunecysta rotunda is similar in shape to Lejeunecysta epidoma Matsuoka 1987 in that both have a dome-shaped epicyst and a trapezoidal hypocyst that tapers posteriorly. It differs from the latter species in having distinctive scabrate to verrucate or pustulate sculpturing on the autophragm. The species also bears a superficial resemblance to Lejeunecysta diversiforma (Bradford 1977) Artzner and Dörhöfer, 1978 and Lejeunecysta hyalina (Gerlach, 1961) Artzner and Dörhöfer, 1978, but its granulate to verrucate or pustulate sculpturing differs from these species. Lejeunecysta diversiforma has a smooth to microgranular or striate autophragm. Lejeunecysta hyalina bears distinctive thin vertical folds and fine granules.
Reported Stratigraphic Occurrence at Cape Roberts: 190.79 mbsf in CRP-3 to 307.12 mbsf in CRP-2A; 857.56 m to 352.54 m in the composite section; Lejeunecysta katatonos Zone to Cymatiosphaera robertsii Zone; Oligocene. The base of ‘Zone B’ of Hannah et al. (2001a) is defined by the first appearance of Lejeunecysta sp. 5 = Lejeunecysta rotunda, and the top of ‘Zone D’ by its last appearance.
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Holotype: Clowes et al., figs.9a–c.
Age: Oligocene.
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Original description (Clowes et al., 2016):
Lejeunecysta rotunda n. sp. Fig. 9a–l
1999 Lejeunecysta sp. 5; Cape Roberts Science Team, table 5.8, fig. 5.8c
2000a Lejeunecysta sp. 5; Cape Roberts Science Team, p. 155, table 5.4, fig.5.7f–g
2000 Lejeunecysta sp. 5; Hannah et al., fig.2, 4f–g
2001 Lejeunecysta sp. 5; Hannah, Wilson & Wrenn, fig. 1
2001 Lejeunecysta sp. 5; Hannah, Wrenn & Wilson, table 1
Description: Shape: Subcircular to elliptical or sub-pentagonal. Epicyst sides are convex, whereas those of the hypocyst are slightly concave to convex. Phragma: The thin autophragm (<1.0 μm) is scabrate to verrucate, with sculptural elements ranging in size from 1 to 2 μm both in diameter and elevation above the cyst surface. Subcircular sculptural elements appear postulate on some specimens. Horns: Short, well rounded, and broad-based apical and antapical horns are usually present, but may be so poorly developed that the cysts are nearly circular in shape. Dark papilla may be present on tip of each horn. Archeopyle: Intercalary, 2a, iso- to slightly eurydeltaform. The operculum may be free but is commonly present, often only slightly displaced from the archeopyle. Tabulation: Indicated only by the archeopyle, cingulum, and sometimes a visible sulcus. Cingulum: Partially delineated by aligned sculptural elements and short folds in the cyst wall. Sulcus: The margin of the sulcus is marked by folds in the autophragm, a shallow antapical concavity between the antapical horns, and a shallow depression on the ventral surface of the hypocyst. A comma- or loop-shaped flagellar scar may be evident on the sulcus.
Dimensions: Length 60 (80) 95 μm, width 65 (78) 90 μm; archeopyle length 12–15 μm, width 19–27 μm (range of 13 specimens).
Comparison: The species is characterised by its generally well rounded, rotund outline, poorly developed apical and antapical horns, and distinctive scabrate to verrucate or pustulate surface sculpture. Lejeunecysta rotunda is similar in shape to Lejeunecysta epidoma Matsuoka 1987 in that both have a dome-shaped epicyst and a trapezoidal hypocyst that tapers posteriorly. It differs from the latter species in having distinctive scabrate to verrucate or pustulate sculpturing on the autophragm. The species also bears a superficial resemblance to Lejeunecysta diversiforma (Bradford 1977) Artzner and Dörhöfer, 1978 and Lejeunecysta hyalina (Gerlach, 1961) Artzner and Dörhöfer, 1978, but its granulate to verrucate or pustulate sculpturing differs from these species. Lejeunecysta diversiforma has a smooth to microgranular or striate autophragm. Lejeunecysta hyalina bears distinctive thin vertical folds and fine granules.
Reported Stratigraphic Occurrence at Cape Roberts: 190.79 mbsf in CRP-3 to 307.12 mbsf in CRP-2A; 857.56 m to 352.54 m in the composite section; Lejeunecysta katatonos Zone to Cymatiosphaera robertsii Zone; Oligocene. The base of ‘Zone B’ of Hannah et al. (2001a) is defined by the first appearance of Lejeunecysta sp. 5 = Lejeunecysta rotunda, and the top of ‘Zone D’ by its last appearance.
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