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Lejeunecysta interrupta
Lejeunecysta interrupta Head and Norris, 2003, p.6,8, fig.6, nos.1-20.
Holotype: Head and Norris, 2003, fig.6, nos.14-17.
Age: Late Miocene-earliest Pliocene.
Origianal description (Head and Norris, 2003):
Ljeunecysta Interrupta new species Figures 5, 6
Diagnosis - Cyst surface smooth to shagreenate, apical horn forms truncated point, symmetrical antapical horns taper to solid points. Cingular margins marked by low, thickened crests bearing spinules, indentations, and/or irregular serrations; crests nearly continuous on anterior margin but restricted to middorsal and lateral locations on posterior margin. Several sutural ridges, which may or may not bear spinules/coni, present on epi- and hypocyst where they converge generally towards horn tips. Archeopyle 2a intercalary, iso-deltaform linteloid with rounded angles; operculum free.
Description - Cysts have peridinioid outline, moderate dorsoventral compression, light brown wall with smooth to shagreenate surface. Apical horn forms truncated point usually bearing two spinules/coni. Antapical horns symmetrically located and taper to solid points. Cingulum nearly planar. Anterior cingular margin marked by almost continuous, low (ca. 1.0 μm), thickened crest bearing spinules, indentations, and/or irregular serrations, although there may be short breaks indicating tabulation (e.g., Fig. 6.5); and ornament is reduced or not present in mid-ventral position (e.g., Fig. 6.4). Posterior cingular margin marked by same ornament but restricted to three distinct crests, again reflecting tabulation: a linear crest positioned mid dorsally, and an arcuate crest located at each lateral margin (e.g., Fig. 6.1). These crests variable in length but usually less than 10 μm long. Middorsal crest occasionally very short (ca. 2 μm long on holotype). Epicyst has three long, low (less than 1.0 μm high) sutural ridges. Two, approximately lateral in position, converge apon apex and usually bear low spinules/coni (e.g., Fig. 6.16a and 6.16c). Third ridge positioned to right of archeopyle on dorsal surface usually bears one prominent spinule although other spinules may also be present (e.g., two on holotype; see Fig. 6.16b). Antapical horns each have two low sutural ridges that converge upon horn tips and may or may not bear spinules/coni; one ridge follows lateral margin of horn, the other the posterior margin. Scattered spinules/coni, sometimes aligned, may also occur on hypocyst. Archeopyle 2a intercalary, iso-deltaform linteloid with rounded angles, as shown by specimens in Figure 6.4 and 6.15. Archeopyle slightly offset to left of dorsoventral midline on holotype (6.15).
Etymology - Latin, interruptus, broken apart, interrupted; with reference to the discontinuous expression of the posterior cingular margin.
Type - Holotype, sample DSDP 603C-37-5, 20–22 cm; slide 2 (ROM 55088); England Finder reference W46/2. Upper Miocene. Figure 6.14–6.17.
Measurements - Holotype: length 37 μm; breadth, including spinules/serrations 35 μm. Range: length 36(42.5)49 μm, standard deviation 4.5 μm; breadth, including spinules/serrations 32(40.3)55 μm, standard deviation 5.2 μm. Spinules/serrations generally up to ca. 1.0 μm in length. Twenty-six specimens measured. See also Figure 5.
Occurrence - Upper Miocene through lowermost Pliocene of DSDP Hole 603C. A single questionable specimen in the lower Upper Pliocene of this hole is possibly reworked.
Comparison - Lejeunecysta interrupta differs from L. cinctoria (see above) in having its posterior cingular margin always indicated by just three short rows of spinules/serrations, this margin being more continuous in L. cinctoria. Also the anterior cingular margin is more continuously delineated in Lejeunecysta interrupta than in L. cinctoria.
Holotype: Head and Norris, 2003, fig.6, nos.14-17.
Age: Late Miocene-earliest Pliocene.
Origianal description (Head and Norris, 2003):
Ljeunecysta Interrupta new species Figures 5, 6
Diagnosis - Cyst surface smooth to shagreenate, apical horn forms truncated point, symmetrical antapical horns taper to solid points. Cingular margins marked by low, thickened crests bearing spinules, indentations, and/or irregular serrations; crests nearly continuous on anterior margin but restricted to middorsal and lateral locations on posterior margin. Several sutural ridges, which may or may not bear spinules/coni, present on epi- and hypocyst where they converge generally towards horn tips. Archeopyle 2a intercalary, iso-deltaform linteloid with rounded angles; operculum free.
Description - Cysts have peridinioid outline, moderate dorsoventral compression, light brown wall with smooth to shagreenate surface. Apical horn forms truncated point usually bearing two spinules/coni. Antapical horns symmetrically located and taper to solid points. Cingulum nearly planar. Anterior cingular margin marked by almost continuous, low (ca. 1.0 μm), thickened crest bearing spinules, indentations, and/or irregular serrations, although there may be short breaks indicating tabulation (e.g., Fig. 6.5); and ornament is reduced or not present in mid-ventral position (e.g., Fig. 6.4). Posterior cingular margin marked by same ornament but restricted to three distinct crests, again reflecting tabulation: a linear crest positioned mid dorsally, and an arcuate crest located at each lateral margin (e.g., Fig. 6.1). These crests variable in length but usually less than 10 μm long. Middorsal crest occasionally very short (ca. 2 μm long on holotype). Epicyst has three long, low (less than 1.0 μm high) sutural ridges. Two, approximately lateral in position, converge apon apex and usually bear low spinules/coni (e.g., Fig. 6.16a and 6.16c). Third ridge positioned to right of archeopyle on dorsal surface usually bears one prominent spinule although other spinules may also be present (e.g., two on holotype; see Fig. 6.16b). Antapical horns each have two low sutural ridges that converge upon horn tips and may or may not bear spinules/coni; one ridge follows lateral margin of horn, the other the posterior margin. Scattered spinules/coni, sometimes aligned, may also occur on hypocyst. Archeopyle 2a intercalary, iso-deltaform linteloid with rounded angles, as shown by specimens in Figure 6.4 and 6.15. Archeopyle slightly offset to left of dorsoventral midline on holotype (6.15).
Etymology - Latin, interruptus, broken apart, interrupted; with reference to the discontinuous expression of the posterior cingular margin.
Type - Holotype, sample DSDP 603C-37-5, 20–22 cm; slide 2 (ROM 55088); England Finder reference W46/2. Upper Miocene. Figure 6.14–6.17.
Measurements - Holotype: length 37 μm; breadth, including spinules/serrations 35 μm. Range: length 36(42.5)49 μm, standard deviation 4.5 μm; breadth, including spinules/serrations 32(40.3)55 μm, standard deviation 5.2 μm. Spinules/serrations generally up to ca. 1.0 μm in length. Twenty-six specimens measured. See also Figure 5.
Occurrence - Upper Miocene through lowermost Pliocene of DSDP Hole 603C. A single questionable specimen in the lower Upper Pliocene of this hole is possibly reworked.
Comparison - Lejeunecysta interrupta differs from L. cinctoria (see above) in having its posterior cingular margin always indicated by just three short rows of spinules/serrations, this margin being more continuous in L. cinctoria. Also the anterior cingular margin is more continuously delineated in Lejeunecysta interrupta than in L. cinctoria.