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Biorbifera ferox
Biorbifera ferox, Riding and Helby, 2001g, p.197,199, figs.9A-T.
Holotype: Riding and Helby, 2001g, figs.9I-L.
Holotype and type locality: Figures 9I-L, CPC 35934, from a sidewall core sample in Avocet-1A well at 1771.50m.
Stratigraphical distribution: confined to the Tithonian, ranging from the upper Dingodinium jurassicum Zone (5aia) to the mid Pseudoceratium iehiense Zone (4ciia) (Foster, this volume; Helby&Partridge, in prep.)
Age: Tithonian.
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Original description: [Riding and Helby, 2001g]:
Description:
A species of Biorbifera with a small, elongate ellipsoidal outline, which is slightly dorsoventrally compressed. The autophragm is microreticulate and robust, between 1-1.5µm thick.
The prominent paracingulum, which may be slightly incised, bears reduced ornamentation. The paracingulum is slightly displaced anteriorly, thereby making the hypocyst consistently larger than the epicyst.
The hypocyst is normally wider than long and has a flattened to angular antapex. The epicyst is flattened or rounded apically.
A partiform gonyaulacalean paratabulation pattern is indicated by thick, low, smooth parasutural ridges.
The parasutural ridges vary from 1 to 1.5 µm in width and height and indicate a paratabulation fromular of ?pr, 4', ?2a, 6", ?6c, 6"', 2"", Xs.
Slender, solid, distally pointed processes are concentrated at the polar areas. They are mainly parasutural (gonal and intergonal), but nontabular processes are also present.
The parasulcus is narrow and not obviously subdivided.
Dimensions: (µm, n=35) excl. processes where appropriate: Min. (Mean) Max.
Length of entire cyst: 19 (24) 33
Length of epicyst*: 6 (8) 11
Length of paracingulum: 2 (2.5) 4
Length of hypocyst* : 11 (14) 20
Equatorial width of cyst: 16 (21) 26
Length of spines: 3 (4) 6
* measured dorsally
The measured specimens are from conventional core samples in Lorikeet-1 well at 1761.20m and Mutineer-1B well at 3132.25m, sidewall core samples from Avocet-1A well at 1771.50m and 1778.00m and ditch cuttings samples from Avocet-1A well at between 1770.00m and 1775.00m and Broome-1 Bore at 297.79m.
Comments/Remarks:
Biobifera ferox is a distinctive small cyst readily identifiable by the epicystal archaeopyle, thick autophragm, well marked paratabulation, particularly on the hypocyst and the apparent concentration of spines at the poles. In poorly preserved material, these processes may be lost. The processes on the precingular paraplates appear to be especially susceptible to damage. Processes have not been observed on the postcingular paraplates apart from the antapical margins. The parasutural ridges suggest a partiform gonyalacalean paratabulation pattern with a formula of ?pr, 4', ?2a, 6",?6c, 6"', 2"",Xs (fig. 9). The paired antapical paraplates are the most characteristic feature of this pattern (Figs. 9O, T). No well preserved isolated epicysts were encountered, therefore the number and configuration of preapical and anterior intercalary paraplates could not be precisely determined. At least two anterior intercalary paraplates appear to be present (Fig. 9L). Furthermore, the paratabulation of the paracingulum and parasulcus was not determined with certainty. In poorly preserved material, the epicyst commonly collapses into the hypocyst.
Affinities:
Biorbifera ferox differs from the genus type, B. johnewingii, in being slightly smaller, having prominent parasutural ridges and much fewer, but longer, robust spines which are largely confined to the polar areas. An unpublished Tithonian species of Biorbifera, recorded in both Australia and New Zealand, is characterised by small processes and a prominent inflation on each of the major paraplates.
Holotype: Riding and Helby, 2001g, figs.9I-L.
Holotype and type locality: Figures 9I-L, CPC 35934, from a sidewall core sample in Avocet-1A well at 1771.50m.
Stratigraphical distribution: confined to the Tithonian, ranging from the upper Dingodinium jurassicum Zone (5aia) to the mid Pseudoceratium iehiense Zone (4ciia) (Foster, this volume; Helby&Partridge, in prep.)
Age: Tithonian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Riding and Helby, 2001g]:
Description:
A species of Biorbifera with a small, elongate ellipsoidal outline, which is slightly dorsoventrally compressed. The autophragm is microreticulate and robust, between 1-1.5µm thick.
The prominent paracingulum, which may be slightly incised, bears reduced ornamentation. The paracingulum is slightly displaced anteriorly, thereby making the hypocyst consistently larger than the epicyst.
The hypocyst is normally wider than long and has a flattened to angular antapex. The epicyst is flattened or rounded apically.
A partiform gonyaulacalean paratabulation pattern is indicated by thick, low, smooth parasutural ridges.
The parasutural ridges vary from 1 to 1.5 µm in width and height and indicate a paratabulation fromular of ?pr, 4', ?2a, 6", ?6c, 6"', 2"", Xs.
Slender, solid, distally pointed processes are concentrated at the polar areas. They are mainly parasutural (gonal and intergonal), but nontabular processes are also present.
The parasulcus is narrow and not obviously subdivided.
Dimensions: (µm, n=35) excl. processes where appropriate: Min. (Mean) Max.
Length of entire cyst: 19 (24) 33
Length of epicyst*: 6 (8) 11
Length of paracingulum: 2 (2.5) 4
Length of hypocyst* : 11 (14) 20
Equatorial width of cyst: 16 (21) 26
Length of spines: 3 (4) 6
* measured dorsally
The measured specimens are from conventional core samples in Lorikeet-1 well at 1761.20m and Mutineer-1B well at 3132.25m, sidewall core samples from Avocet-1A well at 1771.50m and 1778.00m and ditch cuttings samples from Avocet-1A well at between 1770.00m and 1775.00m and Broome-1 Bore at 297.79m.
Comments/Remarks:
Biobifera ferox is a distinctive small cyst readily identifiable by the epicystal archaeopyle, thick autophragm, well marked paratabulation, particularly on the hypocyst and the apparent concentration of spines at the poles. In poorly preserved material, these processes may be lost. The processes on the precingular paraplates appear to be especially susceptible to damage. Processes have not been observed on the postcingular paraplates apart from the antapical margins. The parasutural ridges suggest a partiform gonyalacalean paratabulation pattern with a formula of ?pr, 4', ?2a, 6",?6c, 6"', 2"",Xs (fig. 9). The paired antapical paraplates are the most characteristic feature of this pattern (Figs. 9O, T). No well preserved isolated epicysts were encountered, therefore the number and configuration of preapical and anterior intercalary paraplates could not be precisely determined. At least two anterior intercalary paraplates appear to be present (Fig. 9L). Furthermore, the paratabulation of the paracingulum and parasulcus was not determined with certainty. In poorly preserved material, the epicyst commonly collapses into the hypocyst.
Affinities:
Biorbifera ferox differs from the genus type, B. johnewingii, in being slightly smaller, having prominent parasutural ridges and much fewer, but longer, robust spines which are largely confined to the polar areas. An unpublished Tithonian species of Biorbifera, recorded in both Australia and New Zealand, is characterised by small processes and a prominent inflation on each of the major paraplates.