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Gardodinium angustum
Gardodinium angustum Riding, Helby and Stevens in Riding and Helby, 2001g, p.204,206, figs.12A-P,13A-P.
Holotype: Riding and Helby, 2001g, figs.12E-H.
Age: Tithonian-earliest Berriasian.
(Riding & Helby, 2001g)
1994 Gardodinium sp. A; Bint & Marshall, fig. 5.3
Previous Australian usage: Gardodinium angustum Stevens & Helby (manuscript name). M.P. 677 (pars) – Helby.
Description: An elongate species of Gardodinium which is intermediate in size. Specimens are not dorsoventrally flattened and are elongate ellipsoidal, with a long, parallel-sides, distally closed, truncate apical horn formed from ectophragm. A small , distally rounded apical protuberance is also present on the autocyst. The antapex of both the autocyst and ectocyst is rounded. The autophrgams is smooth to occasionally microscabrate and 1 µm thick. The ectophargam is smooth to irregularly shagreenate ad <0.5 µm thick. The autophragm bears numerous slender (c. 0.5 µm wide) solid, cylindrical processes which connect to, and support, the ectophragm. They are spaced between 1-3 µm apart and may be slightly distally expanded. These processes, however, do not extent into the distal part of the apical horn and are normally significantly sparser in the precingular and parasulcal regions. These processes are dominantly nontabular. The parastabulationis indicated by extremely thin (up to 1 µm), smooth pandasutural bands, which may be partiallyobscured by overlying parasutural ridges on the ectophragm. Immediately inside the pandasutural bands, serveral parallel penitabular lineations are normally partially developed and occasionally may be entirely absent. They are best observed on the longpercingular and postcingular paraplate series. The standard sexiform gonyaulacacean paratabulation pattern is also expressed on the ectophragm by low, smooth parasutural ridges. Accessory endarcheopyle sutures may be develoed in the precingular paraplate series.. The paracingulam is inserted below the mid-point of the loisthocyst and is indicated by both parasutural ridges on the ectophragm and a marked concavity in the ectophragm. The narrow parasulcus is also indented and surrounded by parasutural ridges. Small (3-5 µm diameter) subspherical accumulation bodies may be present inside the autocyst,
Dimensions: (µm, n=26): Min.(Mean)Max.
Lenth of entire cyst: 61(67)74
Length of entire autocyst : 44(52)62
Length of entire loisthocyst: 46(53)69
Length of autocyst in loisthocyst: 42(48)57
Length of entire operculum: 13(19)26
Length of autocyst in operculum: 10(11)13
Length of apical horn: 8(12)17
Maximum width of entire cyst: 25(31)44
Maximum width of autocyst: 19(26)39
Height of apical ectocoel: 7(11)16
Height of antapical ectocoel: 2(4)6
Width of lateral ectocoel: 1(2.5)4
The measures specimens are from conventional core samples from Lambert-2 well at 3101.00m and Lorikwwt-1 well at 1759.10m, sidewall core samples from Avocet-1A well at 1778.00m and 1771.50m and ditch cuttings samples from Avocet-1 A well at 1780.00m to1775.00m and 1775.00m to 1770.00m and from Broome-1 Bore at 297.79m.
Comments: This species of Gardodinium has a distinctlively elongate outline. There are indications of paratabulation on both the autocyst and ectocysts, The ecophragm bears low, smooth parasutural ridges which indicate a sexiform gonyaulacacean paratabulation pattern; the formula is: ?pr, 4’, 6’’, 6c, 6’’’, 1p, 1’’’’, Xs. Additionally, the autophragm has extremely thin, smooth pandasutural bands and is surmounted by penitabular lineation of ectophragmal processes. These pandasutural bands are almost sufficiently slender enough to be termed parasutural. The paracingulum is low on the loisthocyst and results in the precingular paraplate series being long. The apical ectophragmal horn is somewhat flimsy as it is often distorted or bent.
Comparison: Gardodinium angustum differs from the other species of this genus in its elongate outline. Gordodinium trabeculosum is not elongate and the length and width of the autocyst are normally equal (Gocht, 1959, pl. 4, fig. 5). The Early Cretaceous (Valanginian speices G. attenuatum Stover & Helby 1987 is larger than G. angustum, not as elongate and lacks parasutural ridges on the ectophragm. Like G. angustum, G. lowii Backhouse 1987 is elongate, but the latter is substantially larger and has an extremely large apical horn formed from both autophragm and ectophragm. The European species G. ordinale Daveu 1974 resembles G. angustum in having penitabular rows of processes. However, G. ordinale is squat, has an apical horn formed from both the autocyst and ectocyst and lacks processes in the intratabular areas. Gardodinium angustum also resembles Belodinium dysculum Cookson & Esenack 1960 emend. Stover & Helby 1987 in being elongate and holocavate. However, B. dysculum has highly variable penitabular to nontabular autophragmal processes and a significantly longer antapical ectocoel and has an antapical claustrum representing the 1’’’’ paraplate in the ectophragm, like B. nereidis Stevens & Helby (1987, fig. 5).
Derivation of name: From the Latin angustus, meaning narrow, slender or thin, and referering to the characteristic elongate outline of this species.
Holotype and type locality: Figures 12E-H, CPC 35963, from a sidewall core sample in Avocet-1 A well at 1771.50m.
Stratigraphical distributions: G. angustum ranges from the Tithonian lower Pseudoceratium iehiense Zone (4ciiic) to the lowermost Berriasian upper Pseudoceratium iehiense Zone (4cib) (Foster, this volume; Helby & Partridge, in prep.).
Holotype: Riding and Helby, 2001g, figs.12E-H.
Age: Tithonian-earliest Berriasian.
(Riding & Helby, 2001g)
1994 Gardodinium sp. A; Bint & Marshall, fig. 5.3
Previous Australian usage: Gardodinium angustum Stevens & Helby (manuscript name). M.P. 677 (pars) – Helby.
Description: An elongate species of Gardodinium which is intermediate in size. Specimens are not dorsoventrally flattened and are elongate ellipsoidal, with a long, parallel-sides, distally closed, truncate apical horn formed from ectophragm. A small , distally rounded apical protuberance is also present on the autocyst. The antapex of both the autocyst and ectocyst is rounded. The autophrgams is smooth to occasionally microscabrate and 1 µm thick. The ectophargam is smooth to irregularly shagreenate ad <0.5 µm thick. The autophragm bears numerous slender (c. 0.5 µm wide) solid, cylindrical processes which connect to, and support, the ectophragm. They are spaced between 1-3 µm apart and may be slightly distally expanded. These processes, however, do not extent into the distal part of the apical horn and are normally significantly sparser in the precingular and parasulcal regions. These processes are dominantly nontabular. The parastabulationis indicated by extremely thin (up to 1 µm), smooth pandasutural bands, which may be partiallyobscured by overlying parasutural ridges on the ectophragm. Immediately inside the pandasutural bands, serveral parallel penitabular lineations are normally partially developed and occasionally may be entirely absent. They are best observed on the longpercingular and postcingular paraplate series. The standard sexiform gonyaulacacean paratabulation pattern is also expressed on the ectophragm by low, smooth parasutural ridges. Accessory endarcheopyle sutures may be develoed in the precingular paraplate series.. The paracingulam is inserted below the mid-point of the loisthocyst and is indicated by both parasutural ridges on the ectophragm and a marked concavity in the ectophragm. The narrow parasulcus is also indented and surrounded by parasutural ridges. Small (3-5 µm diameter) subspherical accumulation bodies may be present inside the autocyst,
Dimensions: (µm, n=26): Min.(Mean)Max.
Lenth of entire cyst: 61(67)74
Length of entire autocyst : 44(52)62
Length of entire loisthocyst: 46(53)69
Length of autocyst in loisthocyst: 42(48)57
Length of entire operculum: 13(19)26
Length of autocyst in operculum: 10(11)13
Length of apical horn: 8(12)17
Maximum width of entire cyst: 25(31)44
Maximum width of autocyst: 19(26)39
Height of apical ectocoel: 7(11)16
Height of antapical ectocoel: 2(4)6
Width of lateral ectocoel: 1(2.5)4
The measures specimens are from conventional core samples from Lambert-2 well at 3101.00m and Lorikwwt-1 well at 1759.10m, sidewall core samples from Avocet-1A well at 1778.00m and 1771.50m and ditch cuttings samples from Avocet-1 A well at 1780.00m to1775.00m and 1775.00m to 1770.00m and from Broome-1 Bore at 297.79m.
Comments: This species of Gardodinium has a distinctlively elongate outline. There are indications of paratabulation on both the autocyst and ectocysts, The ecophragm bears low, smooth parasutural ridges which indicate a sexiform gonyaulacacean paratabulation pattern; the formula is: ?pr, 4’, 6’’, 6c, 6’’’, 1p, 1’’’’, Xs. Additionally, the autophragm has extremely thin, smooth pandasutural bands and is surmounted by penitabular lineation of ectophragmal processes. These pandasutural bands are almost sufficiently slender enough to be termed parasutural. The paracingulum is low on the loisthocyst and results in the precingular paraplate series being long. The apical ectophragmal horn is somewhat flimsy as it is often distorted or bent.
Comparison: Gardodinium angustum differs from the other species of this genus in its elongate outline. Gordodinium trabeculosum is not elongate and the length and width of the autocyst are normally equal (Gocht, 1959, pl. 4, fig. 5). The Early Cretaceous (Valanginian speices G. attenuatum Stover & Helby 1987 is larger than G. angustum, not as elongate and lacks parasutural ridges on the ectophragm. Like G. angustum, G. lowii Backhouse 1987 is elongate, but the latter is substantially larger and has an extremely large apical horn formed from both autophragm and ectophragm. The European species G. ordinale Daveu 1974 resembles G. angustum in having penitabular rows of processes. However, G. ordinale is squat, has an apical horn formed from both the autocyst and ectocyst and lacks processes in the intratabular areas. Gardodinium angustum also resembles Belodinium dysculum Cookson & Esenack 1960 emend. Stover & Helby 1987 in being elongate and holocavate. However, B. dysculum has highly variable penitabular to nontabular autophragmal processes and a significantly longer antapical ectocoel and has an antapical claustrum representing the 1’’’’ paraplate in the ectophragm, like B. nereidis Stevens & Helby (1987, fig. 5).
Derivation of name: From the Latin angustus, meaning narrow, slender or thin, and referering to the characteristic elongate outline of this species.
Holotype and type locality: Figures 12E-H, CPC 35963, from a sidewall core sample in Avocet-1 A well at 1771.50m.
Stratigraphical distributions: G. angustum ranges from the Tithonian lower Pseudoceratium iehiense Zone (4ciiic) to the lowermost Berriasian upper Pseudoceratium iehiense Zone (4cib) (Foster, this volume; Helby & Partridge, in prep.).