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Cribroperidinium echinatum
From Fensome et al., 2019:
Cribroperidinium echinatum Duxbury, 2019, p.184, pl.7, figs.5,9; pl.8, figs.10–11,15–16. Holotype: Duxbury, 2019, pl.7, figs.5,9. Age: middle? Aptian.
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Holotype: Plate 7, Figures 5, 9.
Type Locality: Heslerton No. 2 at 11.50 m (core chip), “mid” Aptian. Holotype: E.F. T55.4.
Derivation of Name: From the Latin echinatus, prickly - in reference to the spiny nature of this species.
Diagnosis: A thick-walled, spheroidal to ovoidal proximate cyst, autophragm only, the epicyst slightly shorter than the
hypocyst. Prominent slender, tapering, acuminate spines cover the cyst and a tabulation typical of the genus is outlined by low,
spiny ridges. Some intratabular alignment of spines is apparent. No clear apical projection. The archeopyle is formed by loss of
a single precingular plate (3''), operculum free.
Dimensions: Holotype: 51 × 48 μm.
Overall: 66 (56) 51 μm × 61 (52) 43 μm.
Specimens Measured: 8.
Remarks: This distinctive, small species of Cribroperidinium is characterised mainly by its spiny nature and usually clear tabulation, marked by spiny ridges. Its secondary, intratabular spine alignment is again typical of the genus. The presence of overt tabulation precludes the inclusion of this species in Elimatia Duxbury n. gen., the last being characterised by evenly distributed spines which can be reduced or absent in “bald” areas, but without clear tabulation.
Although Heilmann-Clausen and Thomsen (1995, p. 292) stated that Sarjeant’s (1985) emendation of Cribroperidinium aceras (Eisenack 1958) Sarjeant 1985 had allowed them to firmly identify specimens from the Ahlum-1 borehole as C. aceras, their illustrations (op. cit., Plate 6, figures 1 - 5) do not support this, and their material is here included within Cribroperidinium echinatum n. sp. Sarjeant re-studied and re-illustrated Eisenack’s type material (Eisenack 1958, Plate 21, Figures 1, 2) and Sarjeant (1985, Plate IV, Figures 1, 2 and Plate V, Figures 5, 6, text-fig. 2), accepting and describing C. aceras as a valid species, but this is difficult to support. The similarity of Eisenack’s C. aceras type material to Cribroperidinium orthoceras (Eisenack 1958) Davey 1969 is inescapable (see Eisenack 1958, Plate 21, Figures 3–11 and Plate 24, Figure 1, and Sarjeant 1985, Plate I, Figures 1, 4, Plate II, Figures 1, 2, Plate III, Figures 1, 4 and text-fig. l). This might suggest that Eisenack’s C. aceras type specimens are physically damaged C. orthoceras (i.e., lacking the apical horn), in which case Eisenack’s original and Sarjeant’s subsequent illustrations of the holotype appear to show an inverted specimen (well-illustrated in Sarjeant 1985, Plate IV, Figures 1, 2). In the current study, Cribroperidinium orthoceras, and possibly C. aceras, are considered taxonomic junior synonyms of Cribroperidinium edwardsii (Cookson and Eisenack 1958) Davey 1969, the first synonymy following Davey and Verdier (1971).
Cribroperidinium echinatum Duxbury, 2019, p.184, pl.7, figs.5,9; pl.8, figs.10–11,15–16. Holotype: Duxbury, 2019, pl.7, figs.5,9. Age: middle? Aptian.
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Holotype: Plate 7, Figures 5, 9.
Type Locality: Heslerton No. 2 at 11.50 m (core chip), “mid” Aptian. Holotype: E.F. T55.4.
Derivation of Name: From the Latin echinatus, prickly - in reference to the spiny nature of this species.
Diagnosis: A thick-walled, spheroidal to ovoidal proximate cyst, autophragm only, the epicyst slightly shorter than the
hypocyst. Prominent slender, tapering, acuminate spines cover the cyst and a tabulation typical of the genus is outlined by low,
spiny ridges. Some intratabular alignment of spines is apparent. No clear apical projection. The archeopyle is formed by loss of
a single precingular plate (3''), operculum free.
Dimensions: Holotype: 51 × 48 μm.
Overall: 66 (56) 51 μm × 61 (52) 43 μm.
Specimens Measured: 8.
Remarks: This distinctive, small species of Cribroperidinium is characterised mainly by its spiny nature and usually clear tabulation, marked by spiny ridges. Its secondary, intratabular spine alignment is again typical of the genus. The presence of overt tabulation precludes the inclusion of this species in Elimatia Duxbury n. gen., the last being characterised by evenly distributed spines which can be reduced or absent in “bald” areas, but without clear tabulation.
Although Heilmann-Clausen and Thomsen (1995, p. 292) stated that Sarjeant’s (1985) emendation of Cribroperidinium aceras (Eisenack 1958) Sarjeant 1985 had allowed them to firmly identify specimens from the Ahlum-1 borehole as C. aceras, their illustrations (op. cit., Plate 6, figures 1 - 5) do not support this, and their material is here included within Cribroperidinium echinatum n. sp. Sarjeant re-studied and re-illustrated Eisenack’s type material (Eisenack 1958, Plate 21, Figures 1, 2) and Sarjeant (1985, Plate IV, Figures 1, 2 and Plate V, Figures 5, 6, text-fig. 2), accepting and describing C. aceras as a valid species, but this is difficult to support. The similarity of Eisenack’s C. aceras type material to Cribroperidinium orthoceras (Eisenack 1958) Davey 1969 is inescapable (see Eisenack 1958, Plate 21, Figures 3–11 and Plate 24, Figure 1, and Sarjeant 1985, Plate I, Figures 1, 4, Plate II, Figures 1, 2, Plate III, Figures 1, 4 and text-fig. l). This might suggest that Eisenack’s C. aceras type specimens are physically damaged C. orthoceras (i.e., lacking the apical horn), in which case Eisenack’s original and Sarjeant’s subsequent illustrations of the holotype appear to show an inverted specimen (well-illustrated in Sarjeant 1985, Plate IV, Figures 1, 2). In the current study, Cribroperidinium orthoceras, and possibly C. aceras, are considered taxonomic junior synonyms of Cribroperidinium edwardsii (Cookson and Eisenack 1958) Davey 1969, the first synonymy following Davey and Verdier (1971).