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Bonbonadinium granulatum
Bonbonadinium granulatum, Helby and Partridge, 2001, p.221, 223-224, figs.1A-N.
Helby and Partridge (2001, p.223) attributed this name to an unpublished thesis by F.M. Parker.
Holotype: Helby and Partridge, 2001, figs.1K-L.
Type locality: Esso Jurabi-1 well, sidewall core at 1140.0m.
Stratigraphic range: Bonbonadinium granulatum is confined to the Tithonian upper Dingodiniumjurassicum Zone (5aiia-5aid) on the North West Shelf. Warren's specimen was from the upper Tithonian Belodinium dysculum Zone in the Sacramento Valley, California.
Age: Tithonian.
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Original description: [Helby & Partridge, 2001]:
Description:
Small to intermediate sized, elongate ellipsoidal cyst. The polar extremities of the cyst are rounded and each is generally obscured by a single, relatively large corona.
The cyst wall is two layered with the endophragm and periphragm closely appressed except at locations close to the apical and antapical extremities where the periphragm is extended to form the distinctive coronas. The cyst wall is about 1 μm thick. The surface of the periphragm is smooth, microgranulate, microreticulate to finely scabrate. There is a tendency for the size of the elements in this low relief ornamentation to diminish slightly towards the paracingular area.
Archaeopyle apical, type tA. Operculum bears distinctive periphragmal corona, which separates from the endophragm marginally above the lower extremity of the apical paraplates.
The periphragm of each of the coronas is about 0.5 μm thick, transparent to translucent and may bear radial folds/thickenings. The distal edge of the corona is essentially smooth, but may be disrupted by the radial folds/thickenings. The periphragm which forms the antapical corona separates near the apical extremities of the antapical paraplate but occasionally on the lower limits of the postcingular paraplates. The coronas commonly obscure most of apical paraplate series and the antapical extremity of the cyst.
Paratabulation is generally not evident apart from the archaeopyle, relatively short accessory archaeopyle sutures and the parasulcal notch. The archaeopyle margin suggests 4 apical and six precingular paraplates. Rare specimens exhibit parasutural, periphragmal ridges on lower,longitudinal margins of the postcingular paraplates.
Paracingulum not delineated; parasulcus not delineated, although its location is expressed by a well-developed parasulcal notch.
Dimensions (μm; n=38):
Min. (Mean) Max.
Length of loisthocyst ( excl. coronas): 37 ( 46) 55
Maximum width of cyst: 17 (24.4) 34
Length of entire cyst (9 specimens with both coronas): 45 (58.3) 70
Width of apical corona: 11 (18. 8) 32
Width of antapical corona: 11 (17 .6) 32
Length of apical corona: 9 ( 17) 30
Length of antapical corona: 7 (11.3) 28
The measured specimens are from sidewall core samples in Jurabi-1 well at 1140.0m, Macedon-3 at 223 1134.5m and 1146.0m, Pyrenees-2 at 1657.0m, Torres-I at 1058.0m and Wanaea-1at3014.0m.
Remarks:
The coronas vary significantly in shape, length and width. They range from flat, dish-like flanges to distinctly cylindrical funnels, paralleling the sides of the cyst. The coronal membranes often exhibit thickened radial elements which result in a striate appearance and can cause some crenulation of the distal margin. The zone of detachment of the periphragm forming the coronas is often difficult to detect. However, in rare specimens (Figs IA, C) the separation appears to have started along the parasutures on the lower part of the longitudinal sides of the apical and postcingular paraplates, resulting in low, parasutural crests that merge into the corona. In some specimens (Figs lA-E) there is a suggestion that distinct thickening and 'node' development on the distal edge of the antapical corona reflects the shape of the antapical paraplate. The antapical corona is occasionally slightly offset, possibly reflecting a marginal ventral positioning of the antapical paraplate. The random positioning of the parasulcal notch indicates that there has been no preferential compression and suggests that in the living cyst there was no significant dorso-ventral flattening. There is moderate variation in the size range of this species. Parker ( 1986, p.44) recorded significantly larger loisthocysts 45-l 12μm (mean 56μm) long; these measurements include the antapical corona. However, the cyst width of Parker's specimens (18 to 26 μm [mean 22μm ]) was distinctly less than in the specimens we measured.
Affinities/Comparison:
Warren (1967, pl.26, fig. 8) illustrated a specimen of comparable age, which appears identical to B. granulatum, as Ancepitodinium typicum. However, A. typicum includes at least two morphotypes and the designated type lacks an antapical corona but has a low, discontinuous, antapical ring, bearing short processes and also displays paracingular processes. Paracingular processes have not been recorded on B. granulatum. Warren recorded both morphotypes in the same sample (1537, Belodinium dysculum Zone, McCarty Creek). The Cenomanian acritarch Bipatellifera clathrata Singh 1983, has polar "dish-like structures" (Singh, 1983, p.168, pl.62 figs 5-9) consisting of a proximal, low, circular ridge bearing numerous, well-spaced, short processes which are connected distally by a trabeculate rim. The polar coronas in B. granulatum comprise a continuous, funnel-shaped, periphragmal membrane which is slightly flared, generally expanding away from the cyst body. Bipatellifera clathrata is much smaller than B. granulatum and apparently lacks an archaeopyle.
Helby and Partridge (2001, p.223) attributed this name to an unpublished thesis by F.M. Parker.
Holotype: Helby and Partridge, 2001, figs.1K-L.
Type locality: Esso Jurabi-1 well, sidewall core at 1140.0m.
Stratigraphic range: Bonbonadinium granulatum is confined to the Tithonian upper Dingodiniumjurassicum Zone (5aiia-5aid) on the North West Shelf. Warren's specimen was from the upper Tithonian Belodinium dysculum Zone in the Sacramento Valley, California.
Age: Tithonian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description: [Helby & Partridge, 2001]:
Description:
Small to intermediate sized, elongate ellipsoidal cyst. The polar extremities of the cyst are rounded and each is generally obscured by a single, relatively large corona.
The cyst wall is two layered with the endophragm and periphragm closely appressed except at locations close to the apical and antapical extremities where the periphragm is extended to form the distinctive coronas. The cyst wall is about 1 μm thick. The surface of the periphragm is smooth, microgranulate, microreticulate to finely scabrate. There is a tendency for the size of the elements in this low relief ornamentation to diminish slightly towards the paracingular area.
Archaeopyle apical, type tA. Operculum bears distinctive periphragmal corona, which separates from the endophragm marginally above the lower extremity of the apical paraplates.
The periphragm of each of the coronas is about 0.5 μm thick, transparent to translucent and may bear radial folds/thickenings. The distal edge of the corona is essentially smooth, but may be disrupted by the radial folds/thickenings. The periphragm which forms the antapical corona separates near the apical extremities of the antapical paraplate but occasionally on the lower limits of the postcingular paraplates. The coronas commonly obscure most of apical paraplate series and the antapical extremity of the cyst.
Paratabulation is generally not evident apart from the archaeopyle, relatively short accessory archaeopyle sutures and the parasulcal notch. The archaeopyle margin suggests 4 apical and six precingular paraplates. Rare specimens exhibit parasutural, periphragmal ridges on lower,longitudinal margins of the postcingular paraplates.
Paracingulum not delineated; parasulcus not delineated, although its location is expressed by a well-developed parasulcal notch.
Dimensions (μm; n=38):
Min. (Mean) Max.
Length of loisthocyst ( excl. coronas): 37 ( 46) 55
Maximum width of cyst: 17 (24.4) 34
Length of entire cyst (9 specimens with both coronas): 45 (58.3) 70
Width of apical corona: 11 (18. 8) 32
Width of antapical corona: 11 (17 .6) 32
Length of apical corona: 9 ( 17) 30
Length of antapical corona: 7 (11.3) 28
The measured specimens are from sidewall core samples in Jurabi-1 well at 1140.0m, Macedon-3 at 223 1134.5m and 1146.0m, Pyrenees-2 at 1657.0m, Torres-I at 1058.0m and Wanaea-1at3014.0m.
Remarks:
The coronas vary significantly in shape, length and width. They range from flat, dish-like flanges to distinctly cylindrical funnels, paralleling the sides of the cyst. The coronal membranes often exhibit thickened radial elements which result in a striate appearance and can cause some crenulation of the distal margin. The zone of detachment of the periphragm forming the coronas is often difficult to detect. However, in rare specimens (Figs IA, C) the separation appears to have started along the parasutures on the lower part of the longitudinal sides of the apical and postcingular paraplates, resulting in low, parasutural crests that merge into the corona. In some specimens (Figs lA-E) there is a suggestion that distinct thickening and 'node' development on the distal edge of the antapical corona reflects the shape of the antapical paraplate. The antapical corona is occasionally slightly offset, possibly reflecting a marginal ventral positioning of the antapical paraplate. The random positioning of the parasulcal notch indicates that there has been no preferential compression and suggests that in the living cyst there was no significant dorso-ventral flattening. There is moderate variation in the size range of this species. Parker ( 1986, p.44) recorded significantly larger loisthocysts 45-l 12μm (mean 56μm) long; these measurements include the antapical corona. However, the cyst width of Parker's specimens (18 to 26 μm [mean 22μm ]) was distinctly less than in the specimens we measured.
Affinities/Comparison:
Warren (1967, pl.26, fig. 8) illustrated a specimen of comparable age, which appears identical to B. granulatum, as Ancepitodinium typicum. However, A. typicum includes at least two morphotypes and the designated type lacks an antapical corona but has a low, discontinuous, antapical ring, bearing short processes and also displays paracingular processes. Paracingular processes have not been recorded on B. granulatum. Warren recorded both morphotypes in the same sample (1537, Belodinium dysculum Zone, McCarty Creek). The Cenomanian acritarch Bipatellifera clathrata Singh 1983, has polar "dish-like structures" (Singh, 1983, p.168, pl.62 figs 5-9) consisting of a proximal, low, circular ridge bearing numerous, well-spaced, short processes which are connected distally by a trabeculate rim. The polar coronas in B. granulatum comprise a continuous, funnel-shaped, periphragmal membrane which is slightly flared, generally expanding away from the cyst body. Bipatellifera clathrata is much smaller than B. granulatum and apparently lacks an archaeopyle.