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Renidinium rigidum
Renidinium rigidum Prince et al., 1999, p.163–164, pl.1, figs.13–15,17–19. Holotype: Prince et al., 1999, pl.1, figs.13,17–19. Age: early middle Santonian.
Original description (Prince et al., 1999)
Holotype: Slide PRC 1485, sample JBY 4 (collected 1 m above Whitaker's 3-inch Flint, at Joss Bay, east Kent), E/F ref. S42/2.
Paratype: Slide PRC 3922, sample WCI 75, E/F ref. F35/4.
Repository: Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Wales, UK.
Type localities: Joss Bay, east Kent and Whitecliff, Isle of Wight.
Stratigraphic horizon: low middle Santonian.
Etymology: Latin, rigidus, stiff, with reference to the stiffened outer body.
Diagnosis: A globular Renidinium with two short, blunt antapical horns, no lateral horns and an outer body that is stiffened by thickened bars and slabs. The two wall layers are closely appressed in the mid-ventral area giving rise to a thickened slab which has small perforations or hollows. Either side of the mid-ventral area are two thin elongated areas which are in fact two pericoels. On the dorsal surface, the thickened bars form circular areas. No paratabulation is observed although areas delineated by stiffened bars may approximate to certain paraplates. The two wall layers are separated but connected by relatively broad pillars, except along the mid-ventral and mid-dorsal areas where they are appressed.
Description: The inner body is round to oval, with no antapical or lateral horns, and is connected to the outer body by a few relatively broad pillars. These pillars narrow towards their mid-point and broaden towards their tips, giving the cavities between pillars a circular outline in cross section. The pillars may appear anchor-shaped at their tips.
The outer body is globular and the scarcity of pillars results in an undulating outline; it may possess two well-developed, lobe-shaped antapical horns. The outer body has many large round to sub-angular areas delineated by thickened bars which are closely spaced and of highly variable size. The largest of these areas are located over reflected plates 111–1111 and 611–6111 (assuming a gonyaulacoid paratabulation pattern). The mid-ventral area (sulcus?) between these two large areas has smaller hollows or perforations which are widely spaced, giving rise to a thickened slab between the archaeopyle and the antapical hollows on the ventral surface. The outer body is minutely perforate/scabrate on both the hollows and the thickened slabs. The archaeopyle is apical, type tA, the operculum is invariably separated and has not been identified.
Dimensions: Holotype: inner body (width × length) 58 × 62 μm; outer body (width × length) 73 × 86 μm; hollows (maximum diameter) 2–40 μm. Range of 25 measured specimens: inner body 30–80 μm (average 53 μm) wide × 36–64 μm (average 53 μm) long; outer body 42–96 μm (average 75 μm) wide × 50–102 μm (average 67 μm) long; hollows 1–44 μm.
Comparison: Differs from all other species of Renidinium and Senoniasphaera by the thickened slab which is located over the reflected sulcul area. The areas that are delineated by thickened bars are extremely variable in size with the largest located over reflected plates 111–1111 and 611–6111. The most similar species is R. membraniferum Morgenroth, 1968 which possesses dorsal paratabulation. Senoniasphaera edenensis Marshall, 1990 has more pillars, is more perforate and lacks the thickened slab.
Range at Whitecliff: The complete range of Renidinium rigidum marks the basal middle Santonian (upper M. coranguinum Zone).
Original description (Prince et al., 1999)
Holotype: Slide PRC 1485, sample JBY 4 (collected 1 m above Whitaker's 3-inch Flint, at Joss Bay, east Kent), E/F ref. S42/2.
Paratype: Slide PRC 3922, sample WCI 75, E/F ref. F35/4.
Repository: Institute of Geography and Earth Sciences, University of Wales, Aberystwyth, Wales, UK.
Type localities: Joss Bay, east Kent and Whitecliff, Isle of Wight.
Stratigraphic horizon: low middle Santonian.
Etymology: Latin, rigidus, stiff, with reference to the stiffened outer body.
Diagnosis: A globular Renidinium with two short, blunt antapical horns, no lateral horns and an outer body that is stiffened by thickened bars and slabs. The two wall layers are closely appressed in the mid-ventral area giving rise to a thickened slab which has small perforations or hollows. Either side of the mid-ventral area are two thin elongated areas which are in fact two pericoels. On the dorsal surface, the thickened bars form circular areas. No paratabulation is observed although areas delineated by stiffened bars may approximate to certain paraplates. The two wall layers are separated but connected by relatively broad pillars, except along the mid-ventral and mid-dorsal areas where they are appressed.
Description: The inner body is round to oval, with no antapical or lateral horns, and is connected to the outer body by a few relatively broad pillars. These pillars narrow towards their mid-point and broaden towards their tips, giving the cavities between pillars a circular outline in cross section. The pillars may appear anchor-shaped at their tips.
The outer body is globular and the scarcity of pillars results in an undulating outline; it may possess two well-developed, lobe-shaped antapical horns. The outer body has many large round to sub-angular areas delineated by thickened bars which are closely spaced and of highly variable size. The largest of these areas are located over reflected plates 111–1111 and 611–6111 (assuming a gonyaulacoid paratabulation pattern). The mid-ventral area (sulcus?) between these two large areas has smaller hollows or perforations which are widely spaced, giving rise to a thickened slab between the archaeopyle and the antapical hollows on the ventral surface. The outer body is minutely perforate/scabrate on both the hollows and the thickened slabs. The archaeopyle is apical, type tA, the operculum is invariably separated and has not been identified.
Dimensions: Holotype: inner body (width × length) 58 × 62 μm; outer body (width × length) 73 × 86 μm; hollows (maximum diameter) 2–40 μm. Range of 25 measured specimens: inner body 30–80 μm (average 53 μm) wide × 36–64 μm (average 53 μm) long; outer body 42–96 μm (average 75 μm) wide × 50–102 μm (average 67 μm) long; hollows 1–44 μm.
Comparison: Differs from all other species of Renidinium and Senoniasphaera by the thickened slab which is located over the reflected sulcul area. The areas that are delineated by thickened bars are extremely variable in size with the largest located over reflected plates 111–1111 and 611–6111. The most similar species is R. membraniferum Morgenroth, 1968 which possesses dorsal paratabulation. Senoniasphaera edenensis Marshall, 1990 has more pillars, is more perforate and lacks the thickened slab.
Range at Whitecliff: The complete range of Renidinium rigidum marks the basal middle Santonian (upper M. coranguinum Zone).