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Suessia disintegra
Suessia disintegra sp. nov., Mantle et al. 2020, p. 33
Holotype: Mantle et al. 2020, Plate III, 12a, b
Type locality: Northern Carnarvon Basin
Local stratigraphical range: Late Triassic (Norian - Rhaetian)
Original description: Mantle et al. 2020:
Description:
Small to medium, proximate, broadly ellipsoidal, or subspherical dinoflagellate cysts with approximately equant epicysts and hypocysts.
Wall: thin, smooth to scabrate, membranous periphragm separated by 1–4 μm from the thicker endophragm, is only rarely preserved. In most specimens the periphragm is either not preserved or is too closely appressed to the microgranulate, scabrate, or smooth endophragm to be observable. The endophragm varies from moderately rigid (on thicker walled specimens) to comprehensively folded (often with sub-concentric folds around the margin of the cyst).
Tabulation: Other than the archaeopyle margins and the opercular plates, the suessioid tabulation is unexpressed or is indicated only by thin, very low sutural ridges. Thus, the full tabulation formula is unknown, but involves at least nine latitudinal series and appears in full agreement with typical Suessiacean formula.
Tabulation formula (sensu Below, 1987): 1–?2n 3 , ?4–6n 2 , 6–8n a, 12–14n1, 12–15c, 12±n1, 10+n2, ?6–8n3, ?2–3n4
Tabulation formula (sensu Morbey, 1975): 1–?2′, ?4–6a, 6–8ap, 12–14′′, 12–15c, 12+′′′, 10+p, ?6–8pa, ?2–3′′′′
Archaeopyle: disintegration, one of the most distinctive features of this species, and commonly forms by the loss of a small number of apical, anterior intercalary, and postapical plates, though it may progress to the loss of all the climactal plates.
Operculum: compound. Many specimens contain a sub-rounded red-brown accumulation body, 5–13 μm in diameter, close to the cingulum.
Dimensions:
Overall length (including apical plates) 27 μm (40 μm) 56 μm; maximum width 24 μm
(34 μm) 43 μm.
25 measured specimens
Remarks:
The darker and thicker-walled specimens of Suessia disintegra sp. nov. are slightly larger than their thinner-walled, commonly folded counterparts (8 μm longer and 5 μm wider on average, although there is overlap). The former group is commoner in the R. rhaetica Zone and the latter in the H. balmei and W. listeri zones. However, because there is substantial overlap in the sizes, and there are no major morphological differences, these two forms are considered to be within the limits of intraspecific variation.
Examination of further well-preserved material may reveal specimens with a greater number of plates for each latitudinal series than is noted herein.
Affinities/Comparison:
Suessia disintegra sp. nov. is marginally smaller than Suessia swabiana and is readily distinguished in lacking the well-developed sutural ridges in the latter, often surmounted by grana or small spines. Both taxa have similar archaeopyle types (typically losing a subset of the anterior intercalary and postapical plates), however the apical plates are more regularly detached during excystment in Suessia disintegra sp. nov. than by Suessia swabiana. Suessia disintegra sp. nov. is larger than Suessia? scabrata sp. nov., with a more complete expression of the tabulation. It differs from all species of Wanneria by having a compound disintegration style archaeopyle that commonly involves only a small subset of the apical, anterior intercalary, and postapical plates, rather than a simple opercular piece formed from the loss of all the climactal plates.
Holotype: Mantle et al. 2020, Plate III, 12a, b
Type locality: Northern Carnarvon Basin
Local stratigraphical range: Late Triassic (Norian - Rhaetian)
Original description: Mantle et al. 2020:
Description:
Small to medium, proximate, broadly ellipsoidal, or subspherical dinoflagellate cysts with approximately equant epicysts and hypocysts.
Wall: thin, smooth to scabrate, membranous periphragm separated by 1–4 μm from the thicker endophragm, is only rarely preserved. In most specimens the periphragm is either not preserved or is too closely appressed to the microgranulate, scabrate, or smooth endophragm to be observable. The endophragm varies from moderately rigid (on thicker walled specimens) to comprehensively folded (often with sub-concentric folds around the margin of the cyst).
Tabulation: Other than the archaeopyle margins and the opercular plates, the suessioid tabulation is unexpressed or is indicated only by thin, very low sutural ridges. Thus, the full tabulation formula is unknown, but involves at least nine latitudinal series and appears in full agreement with typical Suessiacean formula.
Tabulation formula (sensu Below, 1987): 1–?2n 3 , ?4–6n 2 , 6–8n a, 12–14n1, 12–15c, 12±n1, 10+n2, ?6–8n3, ?2–3n4
Tabulation formula (sensu Morbey, 1975): 1–?2′, ?4–6a, 6–8ap, 12–14′′, 12–15c, 12+′′′, 10+p, ?6–8pa, ?2–3′′′′
Archaeopyle: disintegration, one of the most distinctive features of this species, and commonly forms by the loss of a small number of apical, anterior intercalary, and postapical plates, though it may progress to the loss of all the climactal plates.
Operculum: compound. Many specimens contain a sub-rounded red-brown accumulation body, 5–13 μm in diameter, close to the cingulum.
Dimensions:
Overall length (including apical plates) 27 μm (40 μm) 56 μm; maximum width 24 μm
(34 μm) 43 μm.
25 measured specimens
Remarks:
The darker and thicker-walled specimens of Suessia disintegra sp. nov. are slightly larger than their thinner-walled, commonly folded counterparts (8 μm longer and 5 μm wider on average, although there is overlap). The former group is commoner in the R. rhaetica Zone and the latter in the H. balmei and W. listeri zones. However, because there is substantial overlap in the sizes, and there are no major morphological differences, these two forms are considered to be within the limits of intraspecific variation.
Examination of further well-preserved material may reveal specimens with a greater number of plates for each latitudinal series than is noted herein.
Affinities/Comparison:
Suessia disintegra sp. nov. is marginally smaller than Suessia swabiana and is readily distinguished in lacking the well-developed sutural ridges in the latter, often surmounted by grana or small spines. Both taxa have similar archaeopyle types (typically losing a subset of the anterior intercalary and postapical plates), however the apical plates are more regularly detached during excystment in Suessia disintegra sp. nov. than by Suessia swabiana. Suessia disintegra sp. nov. is larger than Suessia? scabrata sp. nov., with a more complete expression of the tabulation. It differs from all species of Wanneria by having a compound disintegration style archaeopyle that commonly involves only a small subset of the apical, anterior intercalary, and postapical plates, rather than a simple opercular piece formed from the loss of all the climactal plates.