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Ellipsoidictyum fenestellum
From Fensome et al., 2019:
Ellipsoidictyum fenestellum Mantle, 2009b, p.105,106, pl.11, figs.2–4; text-fig.3. Holotype: Mantle, 2009b, pl.11, fig.2. Age:
Callovian–Oxfordian.
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Original description (Mantle, 2009b):
Ellipsoidictyum fenestellum sp. nov.
Plate 11, Figs 2-4; Text-fig. 3
Diagnosis: Cysts proximate-proximochorate, acavate, ovoidal to subpolygonal. Cyst wall 2-layered; autophragm microreticulate; ectophragm reticulate, supported by numerous short, solid processes. Paratabulation expressed by archeopyle margin, laevorotatory paracingulum, and narrow incised parasulcus. Archeopyle apical; operculum free.
Description: Ovoidal to subpolygonal dinoflagellate cyst with a gently rounded antapex and angular archeopyle margin. A thin ectophragm, consisting of a finely divided, open reticulum, is supported by short, solid processes and is typically separated from the autophragm by 2-4 μm; this may increase to 6-8 μm at the antapex and the along the paracingulum. The distal one-third of these processes are flared or furcate, branching up to 4 times before coalescing with branches from adjacent processes. The reticulum is composed of subcircular to subovoidal lumina (2-8 μm in diameter) that cover most of the otherwise laevigate ectophragm (Text-fig. 3). The ectophragm is raised slightly to form narrow crests or ridges along the edges of the paracingulum and parasulcus. The laevorotatory paracingulum is offset by its entire width, whilst the parasulcus is particularly distinctive, being deeply incised into the ectophragm and narrow (2-4 μm wide). The apical archeopyle has an angular margin and distinct parasulcal notch and tab. The operculum was not observed.
Dimensions (16 specimens): Length of cyst (excluding operculum and ectophragm) 49 (58) 66 μm; width of cyst (excluding ectophragm) 40 (48) 63 μm; length of processes 2 (4) 8 μm; thickness of cyst wall 0.5-1.5 μm.
HoIotype: SGM H34, EF 137 /3. CPC no. 39213; Pl. 1 1, Frg. 2. Length of cyst (excluding operculum and ectophragm) 55 pm; width of cyst (excluding ectophragm) 43 μm; length of processes 1.5-3 μm; thickness of autophragm 1 μm.
Typ. locality: Timor Sea, Bayu-Undan Field, Challis-l1 ST1, sidewall core at 1552.5 m (Elang Formation).
Etymology: Lat, fenestra (window); with reference to the rounded lumina forming the reticulate ectophragm.
Comparison: Ellipsoidictyum cinctun Klement 1960 (pp. 78-80; pl. 6, figs 75,16; pl. Z, figs 1, 2; text figs 36, 37) is similar to E. fenestellum sp. nov. in size and overallshape, but differs considerably in bearing a more open reticulum with broader, less regulaq smoothly rounded lumina and more clearly expressed paratabulation. Furthermore, the processes supporting the reticulum are commonly longer and more robust than those of E. fenestellum and the parasulcus is shallower and less prominent. The reticulum of the new species is structurally similar to those developed on some species of Valensiella Eisenack emend. Courtinat 1989 (p. 182). However, all members of that genus may be distinguished by their lack of paratabulation other than the archeopyle margin. Valensiella ovula (Deflandre) Eisenack emend. Courtinat 1989, which is common in the Elang Formation, is further distinguished by its smaller size and broader lumina.
Local occurrence: Elang Formation; Voodooia tabwlata Interval Zone (Subzone VT3) through Wanaea spectabilis Interval Zone; rare.
Ellipsoidictyum fenestellum Mantle, 2009b, p.105,106, pl.11, figs.2–4; text-fig.3. Holotype: Mantle, 2009b, pl.11, fig.2. Age:
Callovian–Oxfordian.
---------------------------------------------------------------------------------------------------
Original description (Mantle, 2009b):
Ellipsoidictyum fenestellum sp. nov.
Plate 11, Figs 2-4; Text-fig. 3
Diagnosis: Cysts proximate-proximochorate, acavate, ovoidal to subpolygonal. Cyst wall 2-layered; autophragm microreticulate; ectophragm reticulate, supported by numerous short, solid processes. Paratabulation expressed by archeopyle margin, laevorotatory paracingulum, and narrow incised parasulcus. Archeopyle apical; operculum free.
Description: Ovoidal to subpolygonal dinoflagellate cyst with a gently rounded antapex and angular archeopyle margin. A thin ectophragm, consisting of a finely divided, open reticulum, is supported by short, solid processes and is typically separated from the autophragm by 2-4 μm; this may increase to 6-8 μm at the antapex and the along the paracingulum. The distal one-third of these processes are flared or furcate, branching up to 4 times before coalescing with branches from adjacent processes. The reticulum is composed of subcircular to subovoidal lumina (2-8 μm in diameter) that cover most of the otherwise laevigate ectophragm (Text-fig. 3). The ectophragm is raised slightly to form narrow crests or ridges along the edges of the paracingulum and parasulcus. The laevorotatory paracingulum is offset by its entire width, whilst the parasulcus is particularly distinctive, being deeply incised into the ectophragm and narrow (2-4 μm wide). The apical archeopyle has an angular margin and distinct parasulcal notch and tab. The operculum was not observed.
Dimensions (16 specimens): Length of cyst (excluding operculum and ectophragm) 49 (58) 66 μm; width of cyst (excluding ectophragm) 40 (48) 63 μm; length of processes 2 (4) 8 μm; thickness of cyst wall 0.5-1.5 μm.
HoIotype: SGM H34, EF 137 /3. CPC no. 39213; Pl. 1 1, Frg. 2. Length of cyst (excluding operculum and ectophragm) 55 pm; width of cyst (excluding ectophragm) 43 μm; length of processes 1.5-3 μm; thickness of autophragm 1 μm.
Typ. locality: Timor Sea, Bayu-Undan Field, Challis-l1 ST1, sidewall core at 1552.5 m (Elang Formation).
Etymology: Lat, fenestra (window); with reference to the rounded lumina forming the reticulate ectophragm.
Comparison: Ellipsoidictyum cinctun Klement 1960 (pp. 78-80; pl. 6, figs 75,16; pl. Z, figs 1, 2; text figs 36, 37) is similar to E. fenestellum sp. nov. in size and overallshape, but differs considerably in bearing a more open reticulum with broader, less regulaq smoothly rounded lumina and more clearly expressed paratabulation. Furthermore, the processes supporting the reticulum are commonly longer and more robust than those of E. fenestellum and the parasulcus is shallower and less prominent. The reticulum of the new species is structurally similar to those developed on some species of Valensiella Eisenack emend. Courtinat 1989 (p. 182). However, all members of that genus may be distinguished by their lack of paratabulation other than the archeopyle margin. Valensiella ovula (Deflandre) Eisenack emend. Courtinat 1989, which is common in the Elang Formation, is further distinguished by its smaller size and broader lumina.
Local occurrence: Elang Formation; Voodooia tabwlata Interval Zone (Subzone VT3) through Wanaea spectabilis Interval Zone; rare.