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Saeptodinium skipseaense
Saeptodinium skipseaense Hunt in Hunt et al., 1985
Holotype: Hunt et al., 1985, pl.1, figs.2,5,8
Age: Late Quaternary
Diagnosis. Large proximate dinoflagellate cysts exhibiting varying degrees of cavation. Pericyst rounded peridinioid, with a rounded epicyst and two blunt antapical horns. Endocyst rounded peridinioid to ovoid.
Periphragm psilate, thin (0.1 μ.m on SEM). Endophragm psilate to faintly scabrate, thin (0.3 μ,m on SEM). Tabulation 4' 3i 5" 7'" 21111, indicated by very narrow, shallow (0 .1 μ,m on SEM) grooves on the outer surface of the endophragm, occasionally also by irregular cracks on the periphragm (seen only in SEM). Cingulum laevorotary, displaced one or two times its breadth, 6-11 μ,m broad, often bordered by small pericoels, occasionally by very low, (0.2 μ,m on SEM) smooth topped ridges on the periphragm. ?Flagellar slit 7-15 μ,m long, 1-2 μ,m wide, with a slightly thickened edge, lies on the sulcus between the ends of the cingulum. Sulcus broad, short and straight sided. Archaeopyle hemiepicystal, opening by a transapical suture and a suture at the anterior edge of the cingulum. Operculum usually free, plates 3' 1-3i 3-5".
Dimensions (in μ,m) Minimum, Mean, Maximum
Pericyst length 58, 91, 150
Pericyst breadth 50, 69, 120
Endocyst length 54, 75, 135
(15 specimens measured).
Holotype. Slide SK39.1 England Finder reference D24.2. Pl. 1, figs. 2, 5, 8. Skipsea Whittow, Skipsea,
East Yorkshire. (TA 184546), Late Devensian silts, Unit 3a of Gilbertson et al. (1984), 2.75 m below ground.
Remarks. This species is attributed to Saeptodinium Harris 1973 on the basis of its hemiepicystal archaeopyle and cavate, peridinioid morphology. It differs from S. gravattense Harris, S. tasmaniense Harris, S. eurypylum (Manum & Cookson) Stover & Evitt and S. hansonianum (Traverse) Stover & Evitt by having a complete tabulation of grooves on the outside of the endocyst. It differs from the rather similar Type D cysts of Norris & McAndrews (1970) by being larger and having a visible tabulation and in lacking the microreticulate ornament on the endophragm of that species It differs from the similar Type C cysts of Norris & McAndrews (1970), which are identical in morphology and tabulation, by being larger and by having the tabulation on the outside, rather than the inside of the endophragm. It lacks the areolate ornament on the inside of the endophragm characteristic of Type C cysts. The bipesoid tabulation (Fig. 2) and general morphology of Saeptodinium skipseaense suggests that it has close affinities with the Peridinium bipes group. Distribution. Saeptodinium skipseaense is known from Late Devensian deposits at Skipsea Whittow, Early Holocene deposits at Hazleslack and Late Holocene deposits at Fiskerton.
Holotype: Hunt et al., 1985, pl.1, figs.2,5,8
Age: Late Quaternary
Diagnosis. Large proximate dinoflagellate cysts exhibiting varying degrees of cavation. Pericyst rounded peridinioid, with a rounded epicyst and two blunt antapical horns. Endocyst rounded peridinioid to ovoid.
Periphragm psilate, thin (0.1 μ.m on SEM). Endophragm psilate to faintly scabrate, thin (0.3 μ,m on SEM). Tabulation 4' 3i 5" 7'" 21111, indicated by very narrow, shallow (0 .1 μ,m on SEM) grooves on the outer surface of the endophragm, occasionally also by irregular cracks on the periphragm (seen only in SEM). Cingulum laevorotary, displaced one or two times its breadth, 6-11 μ,m broad, often bordered by small pericoels, occasionally by very low, (0.2 μ,m on SEM) smooth topped ridges on the periphragm. ?Flagellar slit 7-15 μ,m long, 1-2 μ,m wide, with a slightly thickened edge, lies on the sulcus between the ends of the cingulum. Sulcus broad, short and straight sided. Archaeopyle hemiepicystal, opening by a transapical suture and a suture at the anterior edge of the cingulum. Operculum usually free, plates 3' 1-3i 3-5".
Dimensions (in μ,m) Minimum, Mean, Maximum
Pericyst length 58, 91, 150
Pericyst breadth 50, 69, 120
Endocyst length 54, 75, 135
(15 specimens measured).
Holotype. Slide SK39.1 England Finder reference D24.2. Pl. 1, figs. 2, 5, 8. Skipsea Whittow, Skipsea,
East Yorkshire. (TA 184546), Late Devensian silts, Unit 3a of Gilbertson et al. (1984), 2.75 m below ground.
Remarks. This species is attributed to Saeptodinium Harris 1973 on the basis of its hemiepicystal archaeopyle and cavate, peridinioid morphology. It differs from S. gravattense Harris, S. tasmaniense Harris, S. eurypylum (Manum & Cookson) Stover & Evitt and S. hansonianum (Traverse) Stover & Evitt by having a complete tabulation of grooves on the outside of the endocyst. It differs from the rather similar Type D cysts of Norris & McAndrews (1970) by being larger and having a visible tabulation and in lacking the microreticulate ornament on the endophragm of that species It differs from the similar Type C cysts of Norris & McAndrews (1970), which are identical in morphology and tabulation, by being larger and by having the tabulation on the outside, rather than the inside of the endophragm. It lacks the areolate ornament on the inside of the endophragm characteristic of Type C cysts. The bipesoid tabulation (Fig. 2) and general morphology of Saeptodinium skipseaense suggests that it has close affinities with the Peridinium bipes group. Distribution. Saeptodinium skipseaense is known from Late Devensian deposits at Skipsea Whittow, Early Holocene deposits at Hazleslack and Late Holocene deposits at Fiskerton.