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Impagidinium ordocaviopse
Impagidinium ordocaviopse Iosifova 1996
Holotype: Iosifova 1996: Plate I, 2a-c; Fig. 7C,D
Isotypes: Iosifova 1996: Plate I, 5a-c, Fig. 7A,B; Plate I, la-cPlate I, 4a-c
Locus typicus: Tchernaya Retchka outcrop, the Ryazan district, Russia.
Stratum typicum: deposits of probable Hauterivian age.
Diagnosis: Iosifova 1996, p. 219, 221
Proximate gonyaulacoid cysts with impagidinioid ventral paratabulation. Suture 1"/4" generally absent. Suture 6"/as absent or more rarely reduced. Ridges relatively high with large perforations aligned strictly in one row.
Dimensions: Length (without horns): holotype: 42 µm, range: 40-44µm; width (without ridges): holotype: 37µm, range: 35-38µm; length of ridges (max): holotype: 5µm, range: up to 11µm. Ten specimens measured.
Description: Iosifova 1996, p. 219, 221
Proximate gonyaulacoid cysts, subspherical to rounded pentagonal and with a very short apical horn. Surface of the cyst smooth to scabrate. Blunt apical horn (length 4-5.5 Ám) is formed by junction of gonal processes of apical paraplates. Paratabulation gonyaulacoid, 4", 6", 6c, 5"", lp, 1"". Paraplate 6" narrow and triangular. Suture 6"/as absent or more rarely reduced. The sutural crests are high in the gonal positions and slightly lower in the middle of sutures. Strong gonal projections are developed. Distal margins of crests are smooth or wavy. Relatively large perforations are present near the distal margins of the crests. The holes (diameter 1-2 Ám) are evenly aligned. Paracingulum (width 4Ám) helicoidal, laevorotatory, its ends offset by approximately twice the width of paracingulum. Sulcal paraplates absent. Archeopyle precingular, Type 3".
Variability: Most of the variability is in the development of the crests. Sutural crest 6"/as is often absent; it is absent in the holotype and strongly reduced in the isotype (Plate I, 4a-c; Fig. 7C,D). In another isotype (Plate I, 5a-c; Fig. 7A,B) it is well developed. The perforation of the crests also varies. The holes may be present along the entire length of the crests, or only at its gonal margins. Not all the crests of the one specimen are perforated.
Comparison: Iosifova 1996, p. 219, 221
This species resembles Impagidinium waipawaense Wilson, 1988, I. fenestroseptatum Head, Norris and Mudie, 1989 and I. margaritifera (Cookson and Eisenack, 1960a) Stover and Evitt, 1978 by its strongly perforated crests. It differs from I. waipawaense Wilson, 1988 by its much shorter smooth horn and by the absence of suture 6"/as and parasutural paraplates. It differs from I. margaritifera (Cookson and Eisenack, 1960a) Stover and Evitt, 1978 by the character of its ventral paratabulation: reduction of suture 6"/as and by the more elongate shape of paraplate 6". I. fenestroseptatum Head, Norris and Mudie, 1989 has crests, which are T-shaped in cross-section.
Occurrence: Tchernaya Retchka outcrop, deposits of probable Hauterivian age.
Holotype: Iosifova 1996: Plate I, 2a-c; Fig. 7C,D
Isotypes: Iosifova 1996: Plate I, 5a-c, Fig. 7A,B; Plate I, la-cPlate I, 4a-c
Locus typicus: Tchernaya Retchka outcrop, the Ryazan district, Russia.
Stratum typicum: deposits of probable Hauterivian age.
Diagnosis: Iosifova 1996, p. 219, 221
Proximate gonyaulacoid cysts with impagidinioid ventral paratabulation. Suture 1"/4" generally absent. Suture 6"/as absent or more rarely reduced. Ridges relatively high with large perforations aligned strictly in one row.
Dimensions: Length (without horns): holotype: 42 µm, range: 40-44µm; width (without ridges): holotype: 37µm, range: 35-38µm; length of ridges (max): holotype: 5µm, range: up to 11µm. Ten specimens measured.
Description: Iosifova 1996, p. 219, 221
Proximate gonyaulacoid cysts, subspherical to rounded pentagonal and with a very short apical horn. Surface of the cyst smooth to scabrate. Blunt apical horn (length 4-5.5 Ám) is formed by junction of gonal processes of apical paraplates. Paratabulation gonyaulacoid, 4", 6", 6c, 5"", lp, 1"". Paraplate 6" narrow and triangular. Suture 6"/as absent or more rarely reduced. The sutural crests are high in the gonal positions and slightly lower in the middle of sutures. Strong gonal projections are developed. Distal margins of crests are smooth or wavy. Relatively large perforations are present near the distal margins of the crests. The holes (diameter 1-2 Ám) are evenly aligned. Paracingulum (width 4Ám) helicoidal, laevorotatory, its ends offset by approximately twice the width of paracingulum. Sulcal paraplates absent. Archeopyle precingular, Type 3".
Variability: Most of the variability is in the development of the crests. Sutural crest 6"/as is often absent; it is absent in the holotype and strongly reduced in the isotype (Plate I, 4a-c; Fig. 7C,D). In another isotype (Plate I, 5a-c; Fig. 7A,B) it is well developed. The perforation of the crests also varies. The holes may be present along the entire length of the crests, or only at its gonal margins. Not all the crests of the one specimen are perforated.
Comparison: Iosifova 1996, p. 219, 221
This species resembles Impagidinium waipawaense Wilson, 1988, I. fenestroseptatum Head, Norris and Mudie, 1989 and I. margaritifera (Cookson and Eisenack, 1960a) Stover and Evitt, 1978 by its strongly perforated crests. It differs from I. waipawaense Wilson, 1988 by its much shorter smooth horn and by the absence of suture 6"/as and parasutural paraplates. It differs from I. margaritifera (Cookson and Eisenack, 1960a) Stover and Evitt, 1978 by the character of its ventral paratabulation: reduction of suture 6"/as and by the more elongate shape of paraplate 6". I. fenestroseptatum Head, Norris and Mudie, 1989 has crests, which are T-shaped in cross-section.
Occurrence: Tchernaya Retchka outcrop, deposits of probable Hauterivian age.