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Tringadinium comptum
From Fensome et al., 2019:
Tringadinium comptum Riding and Helby, 2001e, p.131,133, figs.12A–T.
Holotype: Riding and Helby, 2001e, figs.12P–R.
Age: Callovian–Oxfordian.
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Original description (Riding & Helby, 2001e):
Tringadinium comptum sp.nov. (Figs 12A-T)
1988 Gen. et sp. nov. G (M.P. 618D); Helby et al., fig. 3F,G.
Previous Austrlian usage
M.P. 618D – Helby.
Description: A species of Tringadinium that is rounded subtriangular in outline; a deep equatorial constriction in the paracingular area is commonly developed, imparting an hourglass shape to the cyst. The hypocyst is relatively large and the paracingulum, by contrast, is prominent. The epicyst, however, is relatively small. The autophragm is microgranulate, scabrate and may also be irregularly microreticulate. Fenestrae, where developed, are subcircular to ellipsoidal and 0.5-1.0 µm in diameter. The autophragm is further surmounted by ornament of low relief, which may be bacula, clava, large granules, pila or tubercles. Sculptural elements are mainly intratabular, although some appear to be penitabular. These ornamentational elements are highly variable in form, density and arrangement, but they typically comprise penitabular tubercules and/or clava. Some of the postcingular and antapical paraplates may have circular arrangements of ornamentation in penitabular areas. In forms where the ornamentation is densely inserted, there may be some coalescence of the elements. The ornamentation is usually longest and densest on the hypocyst. A slight medial concavity and/or break in ornament mat be developed at the antapex, refectng a partiform gonyaulacalean paratabulation pattern. The cyst is slightly primarily dorsoventrally flattened and the wide, midventral parasulcus is slightly indented.
Dimensions (µm, n=54 including ornamenta where appropriate) Min.(Mean)Max.
Length of cyst, incl. operculum: 23 (30) 40
Length of loistocyst: 22 (29) 37
Length of epicyst: 5 (7) 11
Length of cyst at parcingulum: 5 (7) 11
Length of hypocyst: 10 (15) 20
Maximum width of epicyst: 15 (19) 27
Width of cyst at paracingulum: 11 (16) 24
Maximum width of hypocyst: 19 (24) 31
Length of ornamentational elements: 1 (1.5) 3
The measures specimens are from sidewall cores from Aruna-1 well at 2135.00m; Challis-11 ST1 well at 1552.50,; Challis-11 ST2 well at 1670.70m and 1842.00m and Taltarni-1 well at 2950.00m.
Marked differences in the development of the paracingular constrictions were observed. For examples, at 1670.70m in Challis-11 ST2 well, the specimens had consistently weakly developed equatorial concavities. At this horizon, the average width of the cyst at the paracingulum was 18 µm. By contrast, in the remainder of the samples studied, the average paracingular width was 15 µm.
Comments: The epicyst and paracinugulum are approximately as long as the remainder of the cyst. Bortg the precingular and apical paraplate series are relatively short in height. On average, the epicyst is only 23% of the overall cyst length. The low, nearly flat, operculum is normally free, but specimens with attaches opercula have been observed. An equatorial constriction may be entirely absent or extremely deep with all intermediate conditions between these extremes. This constriction is at the paracingulum, which is relatively long and a distinctive feature of this species. It is possible that post-depositional flattening of the cyst affects the depth of the equatorial constriction. For example, it was noted that specimens which have been post diagenetically flattened tend to have more strongly developed ‘waist’. The parasulcus is relatively wide and expands markedly antapically. This is typically of the partiform paratabulation style. The cyst is widest across the postcingular paraplate series. The ornamentation of the species is also highly variable and comprises penitabular or penitabular/intratabular elements, which may attain 3 µm in length. In the majority of forms, the paratabulation is indicated by penitabular and/or intratabular tubercules and/or clava. Different ornamentational elements may be present on a single specimen, for example forms with bacula, clava and tubercules have been observed. Furthermore, the density and position of the ornamentation of highly variable from extremlely spars to relatively dense and from strictly penitabular to virtually nontabular. Some coalescence of the ornamentation may occur, giving rise to crest-like features, especially in median view. The genral variability of the penitabular nature of ornamentation means that there is a marked variability in the development of the paratabulation. Thus, the slight medial concavity and/or break in ornament at the antapex may represent the 1’’’’/2’’’’ parasuture. The autophragmal fenestrae vary in the density within the specimens studied. Occasionally, the fenestrae may be arranged in lineation, which may be parasutural or penitabular.
Comparison: Tringadinium comptum differs from T. bjaerkei in lacking intratabular inflations or protuberances and having a rounded subtriangular outline. This species also resembles Woodinia bensonii sp.nov. and Woodinia pedis Riding & Helby (this volume). However, T. comptum lacks the extremely elongate postcingular paraplates and intratabular ‘pads’ of differentatied autophragm which characterize Woodinia. The size and shape of Tringadinium comptum are similar to many members of the Early-earliest Mid Jurassic Parvocysta ‘complex’ of Riding (1984). The most similar species being Susadinium faustum (Bjaerke, 1980) Lentin & Williams 1985, with its intratabular bacula (Bjaerke,1980). The Parvocyata ‘complex’, however, all have interior intercalary archeopyles (Riding et al., 1991).
Derivation of name: From the Latin comptus, meaning ornamented and referring to the low-relief ornamentational elements, which characterize this form.
Holotype and type locality: Figures 12P-R, CPC 35593, Challis-11 ST1 well, sidewall cores sample at 1552.50m.
Stratigraphical distribution: Tringadinium comptum ranges from the Callovian, lower Rigaudella aemula Zone (7aiib) to the Oxfordian, mid Wanaea spectabilis Zone (6cii) in the Timor Sea region (Foster, this volume; Helby and Partridge, in prep.). In New Zealand, this species has been recorded from the Calliovian to Oxfordian Oraka Sandstone (Helby et al., 1988, fig. 23).
Tringadinium comptum Riding and Helby, 2001e, p.131,133, figs.12A–T.
Holotype: Riding and Helby, 2001e, figs.12P–R.
Age: Callovian–Oxfordian.
---------------------------------------------------------------------------------------------------
Original description (Riding & Helby, 2001e):
Tringadinium comptum sp.nov. (Figs 12A-T)
1988 Gen. et sp. nov. G (M.P. 618D); Helby et al., fig. 3F,G.
Previous Austrlian usage
M.P. 618D – Helby.
Description: A species of Tringadinium that is rounded subtriangular in outline; a deep equatorial constriction in the paracingular area is commonly developed, imparting an hourglass shape to the cyst. The hypocyst is relatively large and the paracingulum, by contrast, is prominent. The epicyst, however, is relatively small. The autophragm is microgranulate, scabrate and may also be irregularly microreticulate. Fenestrae, where developed, are subcircular to ellipsoidal and 0.5-1.0 µm in diameter. The autophragm is further surmounted by ornament of low relief, which may be bacula, clava, large granules, pila or tubercles. Sculptural elements are mainly intratabular, although some appear to be penitabular. These ornamentational elements are highly variable in form, density and arrangement, but they typically comprise penitabular tubercules and/or clava. Some of the postcingular and antapical paraplates may have circular arrangements of ornamentation in penitabular areas. In forms where the ornamentation is densely inserted, there may be some coalescence of the elements. The ornamentation is usually longest and densest on the hypocyst. A slight medial concavity and/or break in ornament mat be developed at the antapex, refectng a partiform gonyaulacalean paratabulation pattern. The cyst is slightly primarily dorsoventrally flattened and the wide, midventral parasulcus is slightly indented.
Dimensions (µm, n=54 including ornamenta where appropriate) Min.(Mean)Max.
Length of cyst, incl. operculum: 23 (30) 40
Length of loistocyst: 22 (29) 37
Length of epicyst: 5 (7) 11
Length of cyst at parcingulum: 5 (7) 11
Length of hypocyst: 10 (15) 20
Maximum width of epicyst: 15 (19) 27
Width of cyst at paracingulum: 11 (16) 24
Maximum width of hypocyst: 19 (24) 31
Length of ornamentational elements: 1 (1.5) 3
The measures specimens are from sidewall cores from Aruna-1 well at 2135.00m; Challis-11 ST1 well at 1552.50,; Challis-11 ST2 well at 1670.70m and 1842.00m and Taltarni-1 well at 2950.00m.
Marked differences in the development of the paracingular constrictions were observed. For examples, at 1670.70m in Challis-11 ST2 well, the specimens had consistently weakly developed equatorial concavities. At this horizon, the average width of the cyst at the paracingulum was 18 µm. By contrast, in the remainder of the samples studied, the average paracingular width was 15 µm.
Comments: The epicyst and paracinugulum are approximately as long as the remainder of the cyst. Bortg the precingular and apical paraplate series are relatively short in height. On average, the epicyst is only 23% of the overall cyst length. The low, nearly flat, operculum is normally free, but specimens with attaches opercula have been observed. An equatorial constriction may be entirely absent or extremely deep with all intermediate conditions between these extremes. This constriction is at the paracingulum, which is relatively long and a distinctive feature of this species. It is possible that post-depositional flattening of the cyst affects the depth of the equatorial constriction. For example, it was noted that specimens which have been post diagenetically flattened tend to have more strongly developed ‘waist’. The parasulcus is relatively wide and expands markedly antapically. This is typically of the partiform paratabulation style. The cyst is widest across the postcingular paraplate series. The ornamentation of the species is also highly variable and comprises penitabular or penitabular/intratabular elements, which may attain 3 µm in length. In the majority of forms, the paratabulation is indicated by penitabular and/or intratabular tubercules and/or clava. Different ornamentational elements may be present on a single specimen, for example forms with bacula, clava and tubercules have been observed. Furthermore, the density and position of the ornamentation of highly variable from extremlely spars to relatively dense and from strictly penitabular to virtually nontabular. Some coalescence of the ornamentation may occur, giving rise to crest-like features, especially in median view. The genral variability of the penitabular nature of ornamentation means that there is a marked variability in the development of the paratabulation. Thus, the slight medial concavity and/or break in ornament at the antapex may represent the 1’’’’/2’’’’ parasuture. The autophragmal fenestrae vary in the density within the specimens studied. Occasionally, the fenestrae may be arranged in lineation, which may be parasutural or penitabular.
Comparison: Tringadinium comptum differs from T. bjaerkei in lacking intratabular inflations or protuberances and having a rounded subtriangular outline. This species also resembles Woodinia bensonii sp.nov. and Woodinia pedis Riding & Helby (this volume). However, T. comptum lacks the extremely elongate postcingular paraplates and intratabular ‘pads’ of differentatied autophragm which characterize Woodinia. The size and shape of Tringadinium comptum are similar to many members of the Early-earliest Mid Jurassic Parvocysta ‘complex’ of Riding (1984). The most similar species being Susadinium faustum (Bjaerke, 1980) Lentin & Williams 1985, with its intratabular bacula (Bjaerke,1980). The Parvocyata ‘complex’, however, all have interior intercalary archeopyles (Riding et al., 1991).
Derivation of name: From the Latin comptus, meaning ornamented and referring to the low-relief ornamentational elements, which characterize this form.
Holotype and type locality: Figures 12P-R, CPC 35593, Challis-11 ST1 well, sidewall cores sample at 1552.50m.
Stratigraphical distribution: Tringadinium comptum ranges from the Callovian, lower Rigaudella aemula Zone (7aiib) to the Oxfordian, mid Wanaea spectabilis Zone (6cii) in the Timor Sea region (Foster, this volume; Helby and Partridge, in prep.). In New Zealand, this species has been recorded from the Calliovian to Oxfordian Oraka Sandstone (Helby et al., 1988, fig. 23).