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Cribroperidinium episomum
From Fensome et al., 2019:
Cribroperidinium episomum (Sarjeant, 1966b, p.118–119, pl.13, figs.9–10; text-fig.27) Duxbury, 2019, p.184. Emendation: Duxbury (2019, p.184), as Cribroperidinium. Holotype: Sarjeant, 1966b, pl.13, figs.9–10; text-fig.27; Jan du Chêne et al., 1986a, pl.67, figs.15–16. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly Rhynchodiniopsis, fourthly Leptodinium, fifthly (and now) Cribroperidinium. Taxonomic junior synonym: Cribroperidinium boreas, according to Duxbury (2019, p.184). Age: late Barremian.
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Original description Sarjeant, 1966b
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Emended description Duxbury 2019
Emended Diagnosis: A spheroidal to ovoidal dinocyst with a broad apical horn. The cyst wall is of moderate thickness and fibroperforate, free of ornament or bearing intratabular, lightly-striate spines or tubercles. Sutural crests are relatively high, narrow and markedly fenestrate; individual fenestrations can be large, are generally oval and can extend from the cyst wall to the crestal margin, which is smooth. The cingulum divides the cyst into approximately equal halves; the displacement of the cingulum along the sulcus approximates the cingulum width. The reflected tabulation is 4', 6'', ?c, 6''', 1p, 1p.v., 1''''. A precingular archeopyle is formed by the detachment of plate 3''.
Remarks: Very similar descriptions of this species were offered by Sarjeant (1966a, p. 118, 119 - as Gonyaulacysta episoma) and Davey (1974, p. 52, 53 - as Gonyaulacysta boreas), with both authors emphasising the importance of the distinctive overall shape, tabulation and type of sutural crests. Remarkably, both authors also cited the similar crests of Cribroperidinium? scottii (Cookson and Eisenack 1958) Stover and Evitt 1978 and further similarities exhibited by Tehamadinium tenuiceras (Eisenack 1958) Jan du Chêne et al. 1986b. However, Davey (op. cit.) did not discuss C. episomum per se. The sutural crests of this species are particularly characteristic and were well illustrated by Davey (1974, Plate 4, Figure 4). Davey (op. cit., p. 53) described crestal perforations as, “so large that often the crests appear to consist of small membranous processes which are linked distally by trabeculae”, and Sarjeant (1966a, p. 118) described, “Crests consisting of rows of thin spinelets connected distally by trabeculum”. The size ranges quoted for this species by Sarjeant (op. cit., p. 118) and Davey (op. cit., p. 52) are very similar. Towards the top of its range, this species can be larger and more ornate than older material, although still with characteristically entire distal margins to the crests.
Cribroperidinium episomum was described by Sarjeant (op. cit.) from the late Barremian of the West Heslerton No. 1 borehole, where it was abundant and Davey (op. cit.) described it, as Gonyaulacysta boreas, from the late Barremian of the Speeton Clay outcrop. It was restricted to the late Barremian to early Aptian interval in the present study, ranging as young as palynofloral Zone LKP25.
Cribroperidinium episomum (Sarjeant, 1966b, p.118–119, pl.13, figs.9–10; text-fig.27) Duxbury, 2019, p.184. Emendation: Duxbury (2019, p.184), as Cribroperidinium. Holotype: Sarjeant, 1966b, pl.13, figs.9–10; text-fig.27; Jan du Chêne et al., 1986a, pl.67, figs.15–16. Originally Gonyaulacysta, subsequently Millioudodinium, thirdly Rhynchodiniopsis, fourthly Leptodinium, fifthly (and now) Cribroperidinium. Taxonomic junior synonym: Cribroperidinium boreas, according to Duxbury (2019, p.184). Age: late Barremian.
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Original description Sarjeant, 1966b
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Emended description Duxbury 2019
Emended Diagnosis: A spheroidal to ovoidal dinocyst with a broad apical horn. The cyst wall is of moderate thickness and fibroperforate, free of ornament or bearing intratabular, lightly-striate spines or tubercles. Sutural crests are relatively high, narrow and markedly fenestrate; individual fenestrations can be large, are generally oval and can extend from the cyst wall to the crestal margin, which is smooth. The cingulum divides the cyst into approximately equal halves; the displacement of the cingulum along the sulcus approximates the cingulum width. The reflected tabulation is 4', 6'', ?c, 6''', 1p, 1p.v., 1''''. A precingular archeopyle is formed by the detachment of plate 3''.
Remarks: Very similar descriptions of this species were offered by Sarjeant (1966a, p. 118, 119 - as Gonyaulacysta episoma) and Davey (1974, p. 52, 53 - as Gonyaulacysta boreas), with both authors emphasising the importance of the distinctive overall shape, tabulation and type of sutural crests. Remarkably, both authors also cited the similar crests of Cribroperidinium? scottii (Cookson and Eisenack 1958) Stover and Evitt 1978 and further similarities exhibited by Tehamadinium tenuiceras (Eisenack 1958) Jan du Chêne et al. 1986b. However, Davey (op. cit.) did not discuss C. episomum per se. The sutural crests of this species are particularly characteristic and were well illustrated by Davey (1974, Plate 4, Figure 4). Davey (op. cit., p. 53) described crestal perforations as, “so large that often the crests appear to consist of small membranous processes which are linked distally by trabeculae”, and Sarjeant (1966a, p. 118) described, “Crests consisting of rows of thin spinelets connected distally by trabeculum”. The size ranges quoted for this species by Sarjeant (op. cit., p. 118) and Davey (op. cit., p. 52) are very similar. Towards the top of its range, this species can be larger and more ornate than older material, although still with characteristically entire distal margins to the crests.
Cribroperidinium episomum was described by Sarjeant (op. cit.) from the late Barremian of the West Heslerton No. 1 borehole, where it was abundant and Davey (op. cit.) described it, as Gonyaulacysta boreas, from the late Barremian of the Speeton Clay outcrop. It was restricted to the late Barremian to early Aptian interval in the present study, ranging as young as palynofloral Zone LKP25.