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Lejeunecysta acuminata
Lejeunecysta acuminata Clowes et al., 2016, p.72, figs.5a–l.
Holotype: Clowes et al., figs.5a–c.
Age: Oligocene.
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Original description: Clowes et al., 2016:
Lejeunecysta acuminata n. sp. Fig. 5a–l
1975 Lejeunia sp.; Kemp, p. 606, pl. 4, fig. 10–11
1999 Lejeunecysta sp. 6; Cape Roberts Science Team, table 5.8, fig.5.8b
2000a Lejeunecysta sp. 6; Cape Roberts Science Team, p. 155, table 5.4, fig.5.7c
2000a Lejeunecysta cf. sp. 6; Cape Roberts Science Team, table 5.4, fig.5.7d
2000 Lejeunecysta sp. 6; Hannah et al., fig.2, 5a
2001 Lejeunecysta sp. 6; Hannah, Wilson & Wrenn, fig. 1
2001 Lejeunecysta sp. 6; Hannah, Wrenn & Wilson, table 1
2001 Lejeunecysta cf. sp. 6; Hannah, Wrenn & Wilson, table 1
2011 Lejeunecysta sp. A (large); Expedition 318 Scientists, pl. P3.6; P9.4–5
Description: Shape: Sub-pentagonal with a very angular aspect. The sides of the epicyst are slightly convex to slightly concave; those of the hypocyst are straight to concave. Phragma: The thin autophragm (b1.0 μm) has a distinctive granulate texture. Strong, straight, longitudinal thickenings run from the cingulum to the apex and to the antapex on both the dorsal and ventral surfaces of the cyst. These do not coincide with any known dinoflagellate tabulation and are not considered to be sutural. Horns: The apex is capped by a short (c. 5–8 μm), blunt horn, formed at least in part from coalescence of the thickened longitudinal thickenings (Fig. 5j). The short (c. 8 μm), acuminate antapical horns terminate in sharp, solid tips (Fig. 5k), sometimes dark brown in colour (Fig. 5d–f). Archeopyle: Intercalary, 2a, isodeltaform. The operculum is almost always attached at the posterior edge, being only slightly dislodged within the archeopyle margin. Tabulation: Indicated only by the archeopyle, cingulum, and sometimes a visible sulcus. Cingulum: Delineated by well-developed and aligned folds in the cyst wall. Not excavated. Sulcus: The location of the sulcus is often marked by a shallow depression on the ventral surface of the hypocyst. Its posterior margin is marked by a shallow to deep, non-angular concavity between the antapical horns (Fig. 5c).
Dimensions: Length 53 (85) 116 μm, width 61 (80) 109 μm; archeopyle length 15–36 μm, width 22–41 μm (range of 25 specimens).
Comparison: This species is characterised by its very angular, pentagonal shape, acuminate antapical horns with solid tips, granulate sculpturing, and strong, straight folds, apparently non-sutural in position, running from the apex and from the antapex to the cingulum. Lejeunecysta acuminata resembles Lejeunecysta fallax (Morgenroth, 1966) Artzner and Dörhöfer, 1978 in general shape and the presence of longitudinal folds running from the cingulum to the apex and antapex. Lejeunecysta acuminata differs, though, in having a granulate autophragm, a more sharply acute apical horn, better developed spines on the antapical horns, and in being generally larger than Lejeunecysta fallax (although the size ranges do overlap). It is distinguished from Lejeunecysta oliva (Reid, 1977) Turon & Londeix 1988 in possessing better developed horns, longer solid tips to the antapical horns, and a generally less convex outline.
Reported Stratigraphic Occurrence at Cape Roberts: 324.41 mbsf in CRP-3 to 464.98 mbsf in CRP-2A; 991.18 m to 510.40 m in the composite section; Cymatiosphaera cf. invaginata Zone to Cymatiosphaera robertsii Zone; Oligocene.
Remarks: An apparently similar form from DSDP sites 270 and 274, of late Oligocene age, is described and illustrated by Kemp. (1975).
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Holotype: Clowes et al., figs.5a–c.
Age: Oligocene.
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Original description: Clowes et al., 2016:
Lejeunecysta acuminata n. sp. Fig. 5a–l
1975 Lejeunia sp.; Kemp, p. 606, pl. 4, fig. 10–11
1999 Lejeunecysta sp. 6; Cape Roberts Science Team, table 5.8, fig.5.8b
2000a Lejeunecysta sp. 6; Cape Roberts Science Team, p. 155, table 5.4, fig.5.7c
2000a Lejeunecysta cf. sp. 6; Cape Roberts Science Team, table 5.4, fig.5.7d
2000 Lejeunecysta sp. 6; Hannah et al., fig.2, 5a
2001 Lejeunecysta sp. 6; Hannah, Wilson & Wrenn, fig. 1
2001 Lejeunecysta sp. 6; Hannah, Wrenn & Wilson, table 1
2001 Lejeunecysta cf. sp. 6; Hannah, Wrenn & Wilson, table 1
2011 Lejeunecysta sp. A (large); Expedition 318 Scientists, pl. P3.6; P9.4–5
Description: Shape: Sub-pentagonal with a very angular aspect. The sides of the epicyst are slightly convex to slightly concave; those of the hypocyst are straight to concave. Phragma: The thin autophragm (b1.0 μm) has a distinctive granulate texture. Strong, straight, longitudinal thickenings run from the cingulum to the apex and to the antapex on both the dorsal and ventral surfaces of the cyst. These do not coincide with any known dinoflagellate tabulation and are not considered to be sutural. Horns: The apex is capped by a short (c. 5–8 μm), blunt horn, formed at least in part from coalescence of the thickened longitudinal thickenings (Fig. 5j). The short (c. 8 μm), acuminate antapical horns terminate in sharp, solid tips (Fig. 5k), sometimes dark brown in colour (Fig. 5d–f). Archeopyle: Intercalary, 2a, isodeltaform. The operculum is almost always attached at the posterior edge, being only slightly dislodged within the archeopyle margin. Tabulation: Indicated only by the archeopyle, cingulum, and sometimes a visible sulcus. Cingulum: Delineated by well-developed and aligned folds in the cyst wall. Not excavated. Sulcus: The location of the sulcus is often marked by a shallow depression on the ventral surface of the hypocyst. Its posterior margin is marked by a shallow to deep, non-angular concavity between the antapical horns (Fig. 5c).
Dimensions: Length 53 (85) 116 μm, width 61 (80) 109 μm; archeopyle length 15–36 μm, width 22–41 μm (range of 25 specimens).
Comparison: This species is characterised by its very angular, pentagonal shape, acuminate antapical horns with solid tips, granulate sculpturing, and strong, straight folds, apparently non-sutural in position, running from the apex and from the antapex to the cingulum. Lejeunecysta acuminata resembles Lejeunecysta fallax (Morgenroth, 1966) Artzner and Dörhöfer, 1978 in general shape and the presence of longitudinal folds running from the cingulum to the apex and antapex. Lejeunecysta acuminata differs, though, in having a granulate autophragm, a more sharply acute apical horn, better developed spines on the antapical horns, and in being generally larger than Lejeunecysta fallax (although the size ranges do overlap). It is distinguished from Lejeunecysta oliva (Reid, 1977) Turon & Londeix 1988 in possessing better developed horns, longer solid tips to the antapical horns, and a generally less convex outline.
Reported Stratigraphic Occurrence at Cape Roberts: 324.41 mbsf in CRP-3 to 464.98 mbsf in CRP-2A; 991.18 m to 510.40 m in the composite section; Cymatiosphaera cf. invaginata Zone to Cymatiosphaera robertsii Zone; Oligocene.
Remarks: An apparently similar form from DSDP sites 270 and 274, of late Oligocene age, is described and illustrated by Kemp. (1975).
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