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Fostericysta eclipsiana
Fostericysta eclipsiana (Riding and Helby, 2001e, p.115,117, figs.2A–B,3A–P) Riding, 2005b, p.1091.
Originally Fosteria (generic name illegitimate), subsequently (and now) Fostericysta.
Taxonomic junior synonym: Horologinella eclipsiana (name not validly published), according to Riding and Helby (2001e, p.115).
Holotype: Riding and Helby, 2001e, fig.3I.
Age: Callovian–Oxfordian.
Original description (Riding & Helby, 2001e):
Previous Australian usage: Horologinella eclipsiana
Description: cysts having a rounded subpentangular to subquadrate dorsoventral outline with a deeply incised paracingulum. They are strongly dorsoventrally compressed. Autophragm relatively thick; smooth to microgranulate, occasionally irregularly microreticulate. Paratabulation indicated by low parasutural ridges or low crests, which are surmounted by denticles and/or spines. The parasutural ridges become gradually higher and slightly broader laterally. Lateral parasutural denticles are solid, sharp or bluntdistaly, and are longest on the hypocyst; the density of insertion is also variable. The epicyst is shorter than the hypocyst. Hypocyst is slightly asymmetrical in that the left lateral side is slightly more angular due to the presence of the 1p paraplate. The parasulcus is wide and located midventrally. Similarly, the paracingulum is relatively high and is only slightly laevorotory. A large, dark accumulation body is consistently present in the center of the cyst.
Dimensions (µm; n=34, all loisthocysts), including spines/denticles: Min(Mean)Max.
Length of loisthocysts: 26(30)35
Length of epicyst (i.e. precingular series): 7(10)13
Length of hypocyst: 12(16)20
Height of paracingulum: 4(5)7
Width of epicyst: 20(24)32
Width at paracingulum: 15(21)28
With of hypocyst: 25(31)39
Length of accumulation body: 10(14)17
Widthof accumulation body: 8(12)15
Length of denticles/spines: 1(1.5)7
The measures specimens are from sidewall core at 3221.57m and 3223.20m from Layang-1 well.
Comments: Fosteria eclipsiana is a distinctive small species, and is equant in terms of length and width. The posterior intercalary (1p) paraplate of F. eclipsiana is particaularly slender and is located close to the left lateral side. Its presence makes this side straighter, or more angular than the right lateral side (Figs 2, 3). The species is dorsoventrally flattened. The relatively thick autophragm, which is normally smoothto microgranulate, imparts a dark body colour (Fig. 3). Parasutural ridges emerge in the central area of the cyst, close to the edge of the accumulation body. These ridges become more robust, higher and slightly wider, and the surmounting denticles/spines increase in size proportionally (Figs 2, 3). The denticles are norally evenly inserted, generally taper distally to a sharp point and are most prominent on the hypocyst (Figs 2, 3). However, specimens have been observed where the denticles are relatively sparse and/or are either blunt or extremely wide distally, i.e. crenellare or stauromate (Figs 3O, P). In extreme cases, some specimens are virtually devoid of denticles (Fig. 3K). All the specimens observed have a large, dark, accumulation body in the center if the cyst (Fig. 3). These accumulation bodies frequently lack sharp edges, having a diffuse, vaguely-defined periphery. The paracingulum is only slightly laevorotatory, relatively high and is deeply incised; it is located high on the cyst, normally making the epicyst significantly shorter than the hypocyst. The wide, mid-ventral parasulcus is not obviously subdivided. The Archeopyle represents the loss of the entire apical paraplate series. The operculum is free and no isolated opercula were observed, possibly indicating that it is compound. No attached opercula were found; only loisthocysts were recovered (Fig. 3).
Comparison: Some speices of Horologinella are smaller, have poorly defined paratabulation, and have more deeply incised paracingular regions than F. eclipsiana.These taxa include Horologinella angulate De Coninck 1985 and H. tenuissima He 1984. However, H. oblique Cookson & Eisenack 1962 and H. scabrosa He 1984 are larger than F. eclipsiana, and entirely lack indications of paratabulation.
Derivation of name: From Eclipse-1 well, where we first encountered this species.
Holotype and type locality: Figure 3I, CPC 35537, Layang-1 well, conventional cores at 3221.47m.
Stratigraphical distribution: Fosteria eclipsiana ranges from the Callovian Wannaea digitate Zone (7bi) to the Oxfordian mid Wanaea spectabilis Zone (6cii) in the Timor Sea region. It is most prominent in the lower Rigaudella aemula Zone (7aiia) to lower W. spectabilis Zone (6ciii), but is usually a minor, althoughdistnictive, background component of these dinoflagellate cyst suites (Foster, this volume; Helby & Partrigde, in prep.)
Originally Fosteria (generic name illegitimate), subsequently (and now) Fostericysta.
Taxonomic junior synonym: Horologinella eclipsiana (name not validly published), according to Riding and Helby (2001e, p.115).
Holotype: Riding and Helby, 2001e, fig.3I.
Age: Callovian–Oxfordian.
Original description (Riding & Helby, 2001e):
Previous Australian usage: Horologinella eclipsiana
Description: cysts having a rounded subpentangular to subquadrate dorsoventral outline with a deeply incised paracingulum. They are strongly dorsoventrally compressed. Autophragm relatively thick; smooth to microgranulate, occasionally irregularly microreticulate. Paratabulation indicated by low parasutural ridges or low crests, which are surmounted by denticles and/or spines. The parasutural ridges become gradually higher and slightly broader laterally. Lateral parasutural denticles are solid, sharp or bluntdistaly, and are longest on the hypocyst; the density of insertion is also variable. The epicyst is shorter than the hypocyst. Hypocyst is slightly asymmetrical in that the left lateral side is slightly more angular due to the presence of the 1p paraplate. The parasulcus is wide and located midventrally. Similarly, the paracingulum is relatively high and is only slightly laevorotory. A large, dark accumulation body is consistently present in the center of the cyst.
Dimensions (µm; n=34, all loisthocysts), including spines/denticles: Min(Mean)Max.
Length of loisthocysts: 26(30)35
Length of epicyst (i.e. precingular series): 7(10)13
Length of hypocyst: 12(16)20
Height of paracingulum: 4(5)7
Width of epicyst: 20(24)32
Width at paracingulum: 15(21)28
With of hypocyst: 25(31)39
Length of accumulation body: 10(14)17
Widthof accumulation body: 8(12)15
Length of denticles/spines: 1(1.5)7
The measures specimens are from sidewall core at 3221.57m and 3223.20m from Layang-1 well.
Comments: Fosteria eclipsiana is a distinctive small species, and is equant in terms of length and width. The posterior intercalary (1p) paraplate of F. eclipsiana is particaularly slender and is located close to the left lateral side. Its presence makes this side straighter, or more angular than the right lateral side (Figs 2, 3). The species is dorsoventrally flattened. The relatively thick autophragm, which is normally smoothto microgranulate, imparts a dark body colour (Fig. 3). Parasutural ridges emerge in the central area of the cyst, close to the edge of the accumulation body. These ridges become more robust, higher and slightly wider, and the surmounting denticles/spines increase in size proportionally (Figs 2, 3). The denticles are norally evenly inserted, generally taper distally to a sharp point and are most prominent on the hypocyst (Figs 2, 3). However, specimens have been observed where the denticles are relatively sparse and/or are either blunt or extremely wide distally, i.e. crenellare or stauromate (Figs 3O, P). In extreme cases, some specimens are virtually devoid of denticles (Fig. 3K). All the specimens observed have a large, dark, accumulation body in the center if the cyst (Fig. 3). These accumulation bodies frequently lack sharp edges, having a diffuse, vaguely-defined periphery. The paracingulum is only slightly laevorotatory, relatively high and is deeply incised; it is located high on the cyst, normally making the epicyst significantly shorter than the hypocyst. The wide, mid-ventral parasulcus is not obviously subdivided. The Archeopyle represents the loss of the entire apical paraplate series. The operculum is free and no isolated opercula were observed, possibly indicating that it is compound. No attached opercula were found; only loisthocysts were recovered (Fig. 3).
Comparison: Some speices of Horologinella are smaller, have poorly defined paratabulation, and have more deeply incised paracingular regions than F. eclipsiana.These taxa include Horologinella angulate De Coninck 1985 and H. tenuissima He 1984. However, H. oblique Cookson & Eisenack 1962 and H. scabrosa He 1984 are larger than F. eclipsiana, and entirely lack indications of paratabulation.
Derivation of name: From Eclipse-1 well, where we first encountered this species.
Holotype and type locality: Figure 3I, CPC 35537, Layang-1 well, conventional cores at 3221.47m.
Stratigraphical distribution: Fosteria eclipsiana ranges from the Callovian Wannaea digitate Zone (7bi) to the Oxfordian mid Wanaea spectabilis Zone (6cii) in the Timor Sea region. It is most prominent in the lower Rigaudella aemula Zone (7aiia) to lower W. spectabilis Zone (6ciii), but is usually a minor, althoughdistnictive, background component of these dinoflagellate cyst suites (Foster, this volume; Helby & Partrigde, in prep.)