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Woodinia bensonii
Woodinia bensonii Riding and Helby, 2001e, p.133,135–136, figs.13A–T.
Holotype: Riding and Helby, 2001e, figs.13A–B.
Age: Oxfordian.
Original description (Riding & Helby, 2001e)
A rounded subtriangular species of Woodinia with two lateral antapical protuberances which often give rise to a prominent antapical concavity. The cyst normally tapers gently apically. Autophragm microreticulate, scabrate or granulate. intratabular areas of low relief ornamentation are variably developed. In some specimens, extremely low relief ornamentation is present in the apical paraplate series. In the short precingular paraplate series, the intratabular ornamentation comprises subrectangular areas ('pads') of differentiated autophragm comprising dense, short, solid processes which may be interconnected by trabeculae. These subrectangular 'pads' of ornamentation occur close to the principal archaeopyle suture, i.e. near to the apex of the cyst. The elongate postcingular paraplates series may also have areas of differntiated autophragm developed. However, most specimens lack positive ornamentation in this area and short, simple, slender, solid spines may occur, somewhat sparsely and irregularly, in the equatorial region of the cyst, i.e. posterior of the paracingulum. The antapical paraplates are characterised by a subcircular or irregularly shaped cover of short processes in the intratabular areas. The style of ornamentation is similar to that developed within the precingular paraplates, i.e. comprising densely inserted short filaments or processes. However, the density of elements is normally markedly less on the antapical paraplates. These elements may coalesce distally, thereby frequently producing a raised reticulum. The paracingulum and the centre of the antapical area are devoid of positive ornamentation, but may be indented. A narrow midventral indented area may be present and represents the parasulcus. The operculum is frequently attached ventrally and folded back inside the epicyst.
Dimensions (µm n=35): Min. (Mean) Max.
Length of cyst body incl. operculum: 29 (36) 44
Length of cyst body excl. operculum: 28 (33) 28
Width of cyst body at antapex: 25 (33) 44
Width of cyst body at equator: 13 (18) 25
Width of cyst body at apex: 11 (15) 22
Length of ornamentation: <0,5 (1) 2
The measured specimens are from sidewall cores from Arunta-1 well at 1805.00m, 1919.00m and 2135.00m; Challis-11 ST-2 well at 1670m; Eclipse-1 well at 2477.00m and Taltarni-1 well at 2950.00m
Comments. Woodinia bensoniii is characterised by its rounded subtriangular dorsoventral outline and an often well developed antapical concavity (Fig. 13.) The overall length of the cyst is normally close to the maximum width (see Dimensions above). The length and shape of the lateral antapical protuberances are variable. The consistent presence of regular subrectangular areas ('pads') of differntiated autophragm in intratabular precingular positions, close to the apical series is also diagnostic. These relatively small 'pads' commonly form an interrupted ring around the principal archaeopyle suture. This is the only area where the intratabular ornamentation is consistent and regular. The elongate postcingular paraplates are normally surmounted by relativerly sparsely occurring short, slender, simple processes equatorially. Differentiated autophragm is also present on the paired antapical paraplates. This ornamentation is often less dense than that developed on the precingular paraplates and frequently has a microreticulate appearance. The antapical ornamentation may coalesce extensively. It is typically concentrated on the distal parts of the lateral antapical lobes and the central antapical area, close to the 1""/2""" paraplate junction and is normally devoid of positive ornamentation. Individual elements of ornamentation at the antapical region may be relatively variable in thickness. Some significant variation in terms of the development of the antapical concavity was observed. Specimens from Taltarni-1 well at 2950.00m are relatively wide antapically , with a consistent prominent antapical concavity. Material from Arunta-1 well between 1805.00 m and 2135.00m and Chalilis-11 ST2 well at 1670.70m, however, includes relatively high proportions of specimens which lack a marked antapical concavity.
Comparison. Woodinia pedis is subrectangular and distinctly flask-shaped, lacking the prominent, large lateral antapical protuberances and the antapical concavity of Woodsonia bensonii. The former species also has thicker and more regular intratabular ornamentation, particularly prominent 'pads' of differentiated autophragm in the postcingular paraplate series immediately posterior of the paracingulum. Furthermore, the antapical ornamentation of Woodonia pedis is more prominent than that in W. bensonii and is normally contiguous, forming a skirt-like flange to the antapex. Some forms of Woodinia bensonii may be superficially similar in outline to representatives of the Late Cretaceous-Palaeogene acritarch genus Paucilobimorpha de Coninck 1986; for example Paucilobimorpha triradiate de Coninck 1986. However, this genus of small acritarchs lacks any indications of paratabulation and an archeopyle.
Derivation of name. Named for Dr. Don G. Benson.
Holotype and type locality. Figures 13A-B, CPC 35596, Taltarni-1 well, sidewall core sample at 2950.00m
Stratigraphical distribution. A notable acme of Woodinia bensonii distinguishes the Oxfordian, upper part of the mid Wanaea spectabilis Zone (6ciia) in wells in the Montara Field and the adjacent Vulcan Subbasin. Rare occurences are recorded in the lower part of the upper Wanaea spectabilis Zone (subzones 6ciib-6ciia)
Holotype: Riding and Helby, 2001e, figs.13A–B.
Age: Oxfordian.
Original description (Riding & Helby, 2001e)
A rounded subtriangular species of Woodinia with two lateral antapical protuberances which often give rise to a prominent antapical concavity. The cyst normally tapers gently apically. Autophragm microreticulate, scabrate or granulate. intratabular areas of low relief ornamentation are variably developed. In some specimens, extremely low relief ornamentation is present in the apical paraplate series. In the short precingular paraplate series, the intratabular ornamentation comprises subrectangular areas ('pads') of differentiated autophragm comprising dense, short, solid processes which may be interconnected by trabeculae. These subrectangular 'pads' of ornamentation occur close to the principal archaeopyle suture, i.e. near to the apex of the cyst. The elongate postcingular paraplates series may also have areas of differntiated autophragm developed. However, most specimens lack positive ornamentation in this area and short, simple, slender, solid spines may occur, somewhat sparsely and irregularly, in the equatorial region of the cyst, i.e. posterior of the paracingulum. The antapical paraplates are characterised by a subcircular or irregularly shaped cover of short processes in the intratabular areas. The style of ornamentation is similar to that developed within the precingular paraplates, i.e. comprising densely inserted short filaments or processes. However, the density of elements is normally markedly less on the antapical paraplates. These elements may coalesce distally, thereby frequently producing a raised reticulum. The paracingulum and the centre of the antapical area are devoid of positive ornamentation, but may be indented. A narrow midventral indented area may be present and represents the parasulcus. The operculum is frequently attached ventrally and folded back inside the epicyst.
Dimensions (µm n=35): Min. (Mean) Max.
Length of cyst body incl. operculum: 29 (36) 44
Length of cyst body excl. operculum: 28 (33) 28
Width of cyst body at antapex: 25 (33) 44
Width of cyst body at equator: 13 (18) 25
Width of cyst body at apex: 11 (15) 22
Length of ornamentation: <0,5 (1) 2
The measured specimens are from sidewall cores from Arunta-1 well at 1805.00m, 1919.00m and 2135.00m; Challis-11 ST-2 well at 1670m; Eclipse-1 well at 2477.00m and Taltarni-1 well at 2950.00m
Comments. Woodinia bensoniii is characterised by its rounded subtriangular dorsoventral outline and an often well developed antapical concavity (Fig. 13.) The overall length of the cyst is normally close to the maximum width (see Dimensions above). The length and shape of the lateral antapical protuberances are variable. The consistent presence of regular subrectangular areas ('pads') of differntiated autophragm in intratabular precingular positions, close to the apical series is also diagnostic. These relatively small 'pads' commonly form an interrupted ring around the principal archaeopyle suture. This is the only area where the intratabular ornamentation is consistent and regular. The elongate postcingular paraplates are normally surmounted by relativerly sparsely occurring short, slender, simple processes equatorially. Differentiated autophragm is also present on the paired antapical paraplates. This ornamentation is often less dense than that developed on the precingular paraplates and frequently has a microreticulate appearance. The antapical ornamentation may coalesce extensively. It is typically concentrated on the distal parts of the lateral antapical lobes and the central antapical area, close to the 1""/2""" paraplate junction and is normally devoid of positive ornamentation. Individual elements of ornamentation at the antapical region may be relatively variable in thickness. Some significant variation in terms of the development of the antapical concavity was observed. Specimens from Taltarni-1 well at 2950.00m are relatively wide antapically , with a consistent prominent antapical concavity. Material from Arunta-1 well between 1805.00 m and 2135.00m and Chalilis-11 ST2 well at 1670.70m, however, includes relatively high proportions of specimens which lack a marked antapical concavity.
Comparison. Woodinia pedis is subrectangular and distinctly flask-shaped, lacking the prominent, large lateral antapical protuberances and the antapical concavity of Woodsonia bensonii. The former species also has thicker and more regular intratabular ornamentation, particularly prominent 'pads' of differentiated autophragm in the postcingular paraplate series immediately posterior of the paracingulum. Furthermore, the antapical ornamentation of Woodonia pedis is more prominent than that in W. bensonii and is normally contiguous, forming a skirt-like flange to the antapex. Some forms of Woodinia bensonii may be superficially similar in outline to representatives of the Late Cretaceous-Palaeogene acritarch genus Paucilobimorpha de Coninck 1986; for example Paucilobimorpha triradiate de Coninck 1986. However, this genus of small acritarchs lacks any indications of paratabulation and an archeopyle.
Derivation of name. Named for Dr. Don G. Benson.
Holotype and type locality. Figures 13A-B, CPC 35596, Taltarni-1 well, sidewall core sample at 2950.00m
Stratigraphical distribution. A notable acme of Woodinia bensonii distinguishes the Oxfordian, upper part of the mid Wanaea spectabilis Zone (6ciia) in wells in the Montara Field and the adjacent Vulcan Subbasin. Rare occurences are recorded in the lower part of the upper Wanaea spectabilis Zone (subzones 6ciib-6ciia)