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Cribroperidinium robustum
Plate 14, Figures 1, 2, 5, 6, 9, 10, 13, 14
Holotype: Plate 14, Figures 5, 9, 13
Paratype: Plate 14, Figures 1, 2
Type Locality: Speeton Clay Formation, late Hauterivian. Bed C3, marginatus ammonite Zone. Holotype: Slide C3(3), E.F. M43.0. Paratype: Slide C3(2), E.F. T53.4.
Derivation of Name: From the Latin robustus, firm, solid, robust- in reference to the nature of this species.
Diagnosis: An intermediate to large species, thick-walled and ovoidal, with a long, tapering and flat-ended apical horn. The epicyst and hypocyst are of approximately equal length. The autophragm is fibro-perforate and typical gonyaulacacean paratabulation is outlined by high crests of even height, which are characteristically microperforate and distally entire or with broad crenellations. Secondary crests of similar height are clearly defined. A small number of verrucae or short coni are distributed over the cyst surface, and some mesotabular grouping is common. The archeopyle is formed by detachment of plate 3".
Dimensions: Holotype: Length - 99 μm. Width - 73 μm.
Paratype: Length - 99 μm. Width - 71 μm. Overall: 101 (98) 89 μm × 84 (75) 71 μm.
Specimens Measured: 9.
Remarks: This is a thick-walled and robust species characterised particularly by its high, distally entire, microperforate sutural and secondary crests. In transmitted light, the gonal areas appear particularly pronounced, imparting a “pseudospinose” effect. The combination of high crests and sharp gonal contacts produces a distinct angularity to this species. Cribroperidinium robustum n. sp. has several characteristics in common with Cribroperidinium edwardsii (Cookson and Eisenack 1958) Davey 1969, including its size and the presence of a long, flat-ended apical horn but it differs in being more angular and in having a thicker wall with much higher crests.
Neale and Sarjeant (1962, p. 443) described Cribroperidinium sepimentum with, “an antapical process formed by an outgrowth of crests at the antapex” and crests which, “show lines of perforations sometimes intersecting the outer margin to form slits; these produce a fibrous appearance”. None of these characteristics were observed in C. robustum.
Cribroperidinium robustum was recorded from Speeton Bed C4C (late Hauterivian, gottschei ammonite Zone) to the top of the studied section. Because of the wide sampling gap between Beds C6 and C4C, its FAD is assumed to be deeper, although by at most one ammonite zone, and still within the late Hauterivian.
Holotype: Plate 14, Figures 5, 9, 13
Paratype: Plate 14, Figures 1, 2
Type Locality: Speeton Clay Formation, late Hauterivian. Bed C3, marginatus ammonite Zone. Holotype: Slide C3(3), E.F. M43.0. Paratype: Slide C3(2), E.F. T53.4.
Derivation of Name: From the Latin robustus, firm, solid, robust- in reference to the nature of this species.
Diagnosis: An intermediate to large species, thick-walled and ovoidal, with a long, tapering and flat-ended apical horn. The epicyst and hypocyst are of approximately equal length. The autophragm is fibro-perforate and typical gonyaulacacean paratabulation is outlined by high crests of even height, which are characteristically microperforate and distally entire or with broad crenellations. Secondary crests of similar height are clearly defined. A small number of verrucae or short coni are distributed over the cyst surface, and some mesotabular grouping is common. The archeopyle is formed by detachment of plate 3".
Dimensions: Holotype: Length - 99 μm. Width - 73 μm.
Paratype: Length - 99 μm. Width - 71 μm. Overall: 101 (98) 89 μm × 84 (75) 71 μm.
Specimens Measured: 9.
Remarks: This is a thick-walled and robust species characterised particularly by its high, distally entire, microperforate sutural and secondary crests. In transmitted light, the gonal areas appear particularly pronounced, imparting a “pseudospinose” effect. The combination of high crests and sharp gonal contacts produces a distinct angularity to this species. Cribroperidinium robustum n. sp. has several characteristics in common with Cribroperidinium edwardsii (Cookson and Eisenack 1958) Davey 1969, including its size and the presence of a long, flat-ended apical horn but it differs in being more angular and in having a thicker wall with much higher crests.
Neale and Sarjeant (1962, p. 443) described Cribroperidinium sepimentum with, “an antapical process formed by an outgrowth of crests at the antapex” and crests which, “show lines of perforations sometimes intersecting the outer margin to form slits; these produce a fibrous appearance”. None of these characteristics were observed in C. robustum.
Cribroperidinium robustum was recorded from Speeton Bed C4C (late Hauterivian, gottschei ammonite Zone) to the top of the studied section. Because of the wide sampling gap between Beds C6 and C4C, its FAD is assumed to be deeper, although by at most one ammonite zone, and still within the late Hauterivian.