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Amphorosphaeridium almae
From Fensome et al., 2019:
Amphorosphaeridium? almae, Schiøler, 2005, p.28–29, pl.12, figs.11–13; text-figs.5a–h.
Holotype: Schiøler, 2005, pl.12, fig.11.
Questionable assignment: Schiøler (2005, p.28).
Age: middle to late Rupelian.
Horizon: Lark Formation, 5780–5810# (1761.7–1770.9 m).
Stratigraphical range: Middle to upper Rupelian in Alma-1X.
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Original description: [Schiøler, 2005]:
Diagnosis:
Proximochorate, gonyaulacoid cyst with a thick, fibrous wall and numerous apparently non-tabulate, solid, fibrous, flexuous, distally pointed or bifid to licrate, sometimes branched, processes.
Archaeopyle precingular, type P3´´.
Description:
Proximochorate, gonyaulacoid cyst of intermediate size (sensu Evitt, 1985), oval to sub-circular in outline. T
he number of wall layers could not be determined; the cyst probably has an autophragm. The cyst wall is fibrous and thick (3–7 µm), its surface is densely pitted.
Numerous (>60), discrete, solid, fibrous, flexuous to anastomosing processes rise from the surface. The processes appear non-tabulate; however, they are often connected proximally by low ridges to form process rows or groups that may or may not reflect paratabulation. The processes may also be arranged in composite process groups (Figs 5c, d). Most processes have a broad base, but taper at half-length to become slender. Process shape varies on a specimen: ranging from simple and acuminate (Fig. 5a) over bifurcate to trifurcate (Fig. 5b) to licrate (Figs 5d, e, f). Some processes branch at half-length or above to form two or more sets of tips (e.g. Pl. 12, fig. 12 at c. 2 o’clock, fig. 13 at 9 and 10 o’clock; Figs 5e, g, h). The epicystal processes are usually slightly longer than those of the hypocystal area; the longest being those of the apex, the shortest being those in postcingular position. Process length variation may be from 5–15 µm on a specimen. The overall process length is fairly constant in a population.
The archaeopyle is precingular, presumably P3´´, judged from its shape (Pl. 12, figs 11–13).
The paratabulation is difficult to determine and may be indicated only by the archaeopyle and, on some specimens, possibly by rows or groups of processes.
Dimensions:
Fifteen specimens measured (µm): Holotype - Range
Length: 54 - 54 (58) 62
Width: 52 - 50 (54) 58
Process length: 8-13 - 5-15
Affinities/Remarks:
The new species resembles Amphorosphaeridium multispinosum (Davey & Williams, 1966) Sarjeant, 1981 (especially specimens of that species figured by Jan du Chêne & Adediran, 1985, pl. 14, figs 3, 4, 9), but differs by having more and shorter, flexuous processes. Amphorosphaeridium? almae differs from A. multibrevum Davey, 1969, which also has numerous processes (although not as many as the new species), in having solid, flexuous processes that terminate bifid to licrate, sometimes branching, instead of having hollow processes that are spinous distally. Amphorosphaeridium? almae resembles species of Cordosphaeridium and Fibrocysta in its wall structure and in having fibrous processes, but differs from species of Cordosphaeridium in having numerous, non-tabulate processes instead of the much fewer and tabulate processes characteristic of the latter genus. It differs from species of Fibrocysta in lacking polar protrusions, and from species of Exochosphaeridium in having complex process tips instead of the simple process tips typical of the latter genus. Specimens of Amphorosphaeridium typically have hollow processes and possess distinctive polar processes (Davey, 1969). As these characters are not typical for the new species, it is placed in Amphorosphaeridium with some hesitation.
Amphorosphaeridium? almae, Schiøler, 2005, p.28–29, pl.12, figs.11–13; text-figs.5a–h.
Holotype: Schiøler, 2005, pl.12, fig.11.
Questionable assignment: Schiøler (2005, p.28).
Age: middle to late Rupelian.
Horizon: Lark Formation, 5780–5810# (1761.7–1770.9 m).
Stratigraphical range: Middle to upper Rupelian in Alma-1X.
---------------------------------------------------------------------------------------------------
Original description: [Schiøler, 2005]:
Diagnosis:
Proximochorate, gonyaulacoid cyst with a thick, fibrous wall and numerous apparently non-tabulate, solid, fibrous, flexuous, distally pointed or bifid to licrate, sometimes branched, processes.
Archaeopyle precingular, type P3´´.
Description:
Proximochorate, gonyaulacoid cyst of intermediate size (sensu Evitt, 1985), oval to sub-circular in outline. T
he number of wall layers could not be determined; the cyst probably has an autophragm. The cyst wall is fibrous and thick (3–7 µm), its surface is densely pitted.
Numerous (>60), discrete, solid, fibrous, flexuous to anastomosing processes rise from the surface. The processes appear non-tabulate; however, they are often connected proximally by low ridges to form process rows or groups that may or may not reflect paratabulation. The processes may also be arranged in composite process groups (Figs 5c, d). Most processes have a broad base, but taper at half-length to become slender. Process shape varies on a specimen: ranging from simple and acuminate (Fig. 5a) over bifurcate to trifurcate (Fig. 5b) to licrate (Figs 5d, e, f). Some processes branch at half-length or above to form two or more sets of tips (e.g. Pl. 12, fig. 12 at c. 2 o’clock, fig. 13 at 9 and 10 o’clock; Figs 5e, g, h). The epicystal processes are usually slightly longer than those of the hypocystal area; the longest being those of the apex, the shortest being those in postcingular position. Process length variation may be from 5–15 µm on a specimen. The overall process length is fairly constant in a population.
The archaeopyle is precingular, presumably P3´´, judged from its shape (Pl. 12, figs 11–13).
The paratabulation is difficult to determine and may be indicated only by the archaeopyle and, on some specimens, possibly by rows or groups of processes.
Dimensions:
Fifteen specimens measured (µm): Holotype - Range
Length: 54 - 54 (58) 62
Width: 52 - 50 (54) 58
Process length: 8-13 - 5-15
Affinities/Remarks:
The new species resembles Amphorosphaeridium multispinosum (Davey & Williams, 1966) Sarjeant, 1981 (especially specimens of that species figured by Jan du Chêne & Adediran, 1985, pl. 14, figs 3, 4, 9), but differs by having more and shorter, flexuous processes. Amphorosphaeridium? almae differs from A. multibrevum Davey, 1969, which also has numerous processes (although not as many as the new species), in having solid, flexuous processes that terminate bifid to licrate, sometimes branching, instead of having hollow processes that are spinous distally. Amphorosphaeridium? almae resembles species of Cordosphaeridium and Fibrocysta in its wall structure and in having fibrous processes, but differs from species of Cordosphaeridium in having numerous, non-tabulate processes instead of the much fewer and tabulate processes characteristic of the latter genus. It differs from species of Fibrocysta in lacking polar protrusions, and from species of Exochosphaeridium in having complex process tips instead of the simple process tips typical of the latter genus. Specimens of Amphorosphaeridium typically have hollow processes and possess distinctive polar processes (Davey, 1969). As these characters are not typical for the new species, it is placed in Amphorosphaeridium with some hesitation.