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Lejeunecysta adeliense
Original description: [Bijl et al., 2018, p.114, 116]:
Species Lejeunecysta adeliensis sp. nov. (Plate 2)
Diagnosis. Psilate species of Lejeunecysta with two distinct, isolated, slender, distally tapering antapical horns. The cyst has an exaggerated pentagonal outline due to the strong widening towards the cingulum of both the epicyst and the hypocyst. The cingulum itself is only expressed at both lateral sides, while barely visible on the dorsal and ventral sides.
Holotype. Integrated Ocean Drilling Program Hole U1356A, Core 95R section 1W, interval 64–68 cm, Slide 2; England Finder Coordinates (EFC) Q34; Plate 2K.
Paratype. Integrated Ocean Drilling Program Hole U1356A, Core 95R, Section 2W, interval 24–28 cm, Slide 2; EFC H33; Plate 2L.
Stratum typicum. Lower Oligocene of IODP Hole U1356A, Wilkes Land margin, Antarctica.
Etymology. Named after the type locality of the species, close to the Adélie Coast.
Description. An acavate cyst with a strong pentagonal outline. Both the epicyst and the hypocyst widen strongly towards the cingulum. The phragm is thin (< 1 µm) and psilate. The apex has straight lateral sides extending to a solid apical horn tip. The antapex is characterised by two separate, relatively long, slender horns that distally taper into a pointed tip. The wall of these pointed tips is thicker, resulting in solid ends of the horns. The archeopyle involves an iso- to slightly lati-deltaform second intercalary plate (2a) that is often adnate. The tabulation is only indicated by the archeopyle. The cingulum is marked by a set of parallel flanges along the lateral sides of the cyst, yet is absent on the dorsal and ventral sides. The cyst widens strongly from the anterior and posterior ends towards the cingulum, almost to form lateral horns. The sulcus is indiscernible on the specimens observed.
Dimensions. Holotype: 120 × 114 µm (w × l). Paratype: 140 × 157 µm (w × l). Average dimensions (n = 6): 130 µm (SD 14 µm) × 129 µm (SD 17 µm) (w × l).
Stratigraphic distribution. During the first 1.5 million years following the Rupelian Oi-1 isotope excursion.
Geographic distribution. To date, Lejeunecysta adeliensis sp. nov. has only been recognised in the type section.
Affinities. Lejeunecysta adeliensis sp. nov. is different from all other Lejeunecysta species found at Site U1356 (see, e.g. Fig. 5). It most closely resembles L. katatonos, but differs from that species by having antapical horns that are completely separated rather than closely connected as
in L. katatonos. The antapical horns of L. adeliensis sp. nov. are similar to those of L. pulchra, but the taxa differ in (i) their overall outline, which is rounded in L. pulchra and more angular in L. adeliensis sp. nov., and (ii) the presence of parallel folds marking the cingulum on the lateral ends, which is typical for L. adeliensis sp. nov., but does not occur in L. pulchra.
Species Lejeunecysta adeliensis sp. nov. (Plate 2)
Diagnosis. Psilate species of Lejeunecysta with two distinct, isolated, slender, distally tapering antapical horns. The cyst has an exaggerated pentagonal outline due to the strong widening towards the cingulum of both the epicyst and the hypocyst. The cingulum itself is only expressed at both lateral sides, while barely visible on the dorsal and ventral sides.
Holotype. Integrated Ocean Drilling Program Hole U1356A, Core 95R section 1W, interval 64–68 cm, Slide 2; England Finder Coordinates (EFC) Q34; Plate 2K.
Paratype. Integrated Ocean Drilling Program Hole U1356A, Core 95R, Section 2W, interval 24–28 cm, Slide 2; EFC H33; Plate 2L.
Stratum typicum. Lower Oligocene of IODP Hole U1356A, Wilkes Land margin, Antarctica.
Etymology. Named after the type locality of the species, close to the Adélie Coast.
Description. An acavate cyst with a strong pentagonal outline. Both the epicyst and the hypocyst widen strongly towards the cingulum. The phragm is thin (< 1 µm) and psilate. The apex has straight lateral sides extending to a solid apical horn tip. The antapex is characterised by two separate, relatively long, slender horns that distally taper into a pointed tip. The wall of these pointed tips is thicker, resulting in solid ends of the horns. The archeopyle involves an iso- to slightly lati-deltaform second intercalary plate (2a) that is often adnate. The tabulation is only indicated by the archeopyle. The cingulum is marked by a set of parallel flanges along the lateral sides of the cyst, yet is absent on the dorsal and ventral sides. The cyst widens strongly from the anterior and posterior ends towards the cingulum, almost to form lateral horns. The sulcus is indiscernible on the specimens observed.
Dimensions. Holotype: 120 × 114 µm (w × l). Paratype: 140 × 157 µm (w × l). Average dimensions (n = 6): 130 µm (SD 14 µm) × 129 µm (SD 17 µm) (w × l).
Stratigraphic distribution. During the first 1.5 million years following the Rupelian Oi-1 isotope excursion.
Geographic distribution. To date, Lejeunecysta adeliensis sp. nov. has only been recognised in the type section.
Affinities. Lejeunecysta adeliensis sp. nov. is different from all other Lejeunecysta species found at Site U1356 (see, e.g. Fig. 5). It most closely resembles L. katatonos, but differs from that species by having antapical horns that are completely separated rather than closely connected as
in L. katatonos. The antapical horns of L. adeliensis sp. nov. are similar to those of L. pulchra, but the taxa differ in (i) their overall outline, which is rounded in L. pulchra and more angular in L. adeliensis sp. nov., and (ii) the presence of parallel folds marking the cingulum on the lateral ends, which is typical for L. adeliensis sp. nov., but does not occur in L. pulchra.