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Pseudoceratium turneri
From Fensome et al., 2019:
Pseudoceratium turneri Cookson and Eisenack, 1958, p.55, pl.5, figs.2–6. Holotype: Cookson and Eisenack, 1958, pl.5, fig.3; Fensome et al., 2019a, fig.19R. Originally (and now) Pseudoceratium, subsequently Endoceratium. Fensome et al. (2019a, p.53–54) retained this species in Pseudoceratium. Age: Aptian–Albian.
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Original description: Cookson and Eisenack, 1958
Test either subtriangular with an oblique base and convex sides, prolonged into three horns of unequal length, a longer apical horn and two widely separated divergent antapical horns, or with a rounded base and one antapical horn. Frequently the apical of the body becomes detached near the base of the apical horn.
The ornament usually takes the form of narrow lamella-like membranes with irregular, frequently curved outlines of variable lengths fomed by the distal coalescence of short bifurcate processes, the lamellae either remaining free or uniting to form a more or less complete network.
Dimensions: Type - 180 µm x 100 µm overall; apical horn 55 µm.
Supplemental description: Morgan, 1980, p. 31
Single-layered cyst usually subtriangular with convex sides, to subrhombic; autophragm usually drawn into one apical and one antapical subconical horn, with a broadly rounded bulge forming the single lateral horn, arising at the cingulum and pointed antapically; occasionally the second antapical horn, and the second lateral horn are marked by broad bulges, creating a roughly pentagonal cyst body.
Fibrous processes arise from the autophragm, may unite distally to form perforate striate crests, may untie along their whole length to form striate fibrous crests, and may support a complete or incomplete distal ectophragm, usually perforate; proximally the aligned process bases may be parasutural, defining a gonyaulacean tabulation, or may be non-tabular; distally, the supported ectophragm may be discontinuous, resticted to intertabular areas, and absent along the parasutures; fibrous ornament very variable in hight, 5-12 µm over most of the crest surface, but longer at the horns.
Archaeopyle apical, operculum free.
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Comments Fensome et al., 2019a:
In their original description of this species, Cookson & Eisenack (1958, p. 55) noted that: "The ornament usually takes the form of narrow lamella-like membranes with irregular, frequently curved outlines of variable lengths formed by the distal coalescence of short bifurcate processes, the lamellae either remaining free or uniting to form a more or less complete superficial network."
Although not easy to follow, this description and the accompanying illustrations, strongly indicate that this species has a complete or incomplete outer wall layer (“lamella-like membranes”, “superficial network”) and processes connecting it to the autophragm. We thus retain it in Pseudoceratium.
Stratigraphical occurrence. The holotype of Pseudoceratium turneri is from the Albian of Western Australia. Costa & Davey (1992) placed the FAD of this species at the base of the late Aptian, and the LAD at the Albian–Cenomanian boundary.
Pseudoceratium turneri Cookson and Eisenack, 1958, p.55, pl.5, figs.2–6. Holotype: Cookson and Eisenack, 1958, pl.5, fig.3; Fensome et al., 2019a, fig.19R. Originally (and now) Pseudoceratium, subsequently Endoceratium. Fensome et al. (2019a, p.53–54) retained this species in Pseudoceratium. Age: Aptian–Albian.
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Original description: Cookson and Eisenack, 1958
Test either subtriangular with an oblique base and convex sides, prolonged into three horns of unequal length, a longer apical horn and two widely separated divergent antapical horns, or with a rounded base and one antapical horn. Frequently the apical of the body becomes detached near the base of the apical horn.
The ornament usually takes the form of narrow lamella-like membranes with irregular, frequently curved outlines of variable lengths fomed by the distal coalescence of short bifurcate processes, the lamellae either remaining free or uniting to form a more or less complete network.
Dimensions: Type - 180 µm x 100 µm overall; apical horn 55 µm.
Supplemental description: Morgan, 1980, p. 31
Single-layered cyst usually subtriangular with convex sides, to subrhombic; autophragm usually drawn into one apical and one antapical subconical horn, with a broadly rounded bulge forming the single lateral horn, arising at the cingulum and pointed antapically; occasionally the second antapical horn, and the second lateral horn are marked by broad bulges, creating a roughly pentagonal cyst body.
Fibrous processes arise from the autophragm, may unite distally to form perforate striate crests, may untie along their whole length to form striate fibrous crests, and may support a complete or incomplete distal ectophragm, usually perforate; proximally the aligned process bases may be parasutural, defining a gonyaulacean tabulation, or may be non-tabular; distally, the supported ectophragm may be discontinuous, resticted to intertabular areas, and absent along the parasutures; fibrous ornament very variable in hight, 5-12 µm over most of the crest surface, but longer at the horns.
Archaeopyle apical, operculum free.
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Comments Fensome et al., 2019a:
In their original description of this species, Cookson & Eisenack (1958, p. 55) noted that: "The ornament usually takes the form of narrow lamella-like membranes with irregular, frequently curved outlines of variable lengths formed by the distal coalescence of short bifurcate processes, the lamellae either remaining free or uniting to form a more or less complete superficial network."
Although not easy to follow, this description and the accompanying illustrations, strongly indicate that this species has a complete or incomplete outer wall layer (“lamella-like membranes”, “superficial network”) and processes connecting it to the autophragm. We thus retain it in Pseudoceratium.
Stratigraphical occurrence. The holotype of Pseudoceratium turneri is from the Albian of Western Australia. Costa & Davey (1992) placed the FAD of this species at the base of the late Aptian, and the LAD at the Albian–Cenomanian boundary.