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Endoscrinium prolatum
Endoscrinium prolatum (Stevens, 1987) Lentin and Williams, 1989
NOW Scriniodinium. Originally (and now) Scriniodinium, subsequently Endoscrinium.
Riding and Fensome (2003, p.18) retained this species in Scriniodinium.
Holotype: Stevens, 1987, fig.9A-C
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Early Berriasian
Original description: Stevens, 1987, p. 193-194: Scriniodinium prolatum
Cysts proximate, bicavate to circumcavate, roundly kite-shaped, with a long, broad, apical horn. Apical horn generally one quarter to one third the cyst length, consisting of a truncate, distally open perihorn and a rounded, closed endohorn extending one half to three quarters the length of the perihorn. Periphragm and endophragm both less than 1 Ám thick, may be appressed in part, or separated by a 1-4 Ám wide pericoel over much of the cyst, except at the apex and antapex, where the pericoel is 5-18 Ám and 2-8 Ám wide, respectively. Periphragm scabrate, ornamented by irregularly shaped verrucate processes (1-1.5 Ám high and wide), or by perforations which are circular to oval in outline, 1 to 4 Ám in diameter, and commonly concentrated at the apical horn. Endophragm smooth. Archeopyle precingular, type P (3"" only), endo- and periarcheopyles similar in size. Operculum 26-46 Ám long, free, the endo- and periopercula remaining attached after dehiscence.
Paratabulation incomplete, indicated by the archeopyle, the paracingulum and some parasutural folds, formula unknown. Parasutural folds in the periphragm up to 1.5 Ám in height and width, delineating only a few sutures, mainly on the epicyst. Paracingulum expressed by folds in the periphragm up to 3 Ám high and up to 1.5 Ám wide along which verrucae, when present, may be aligned. The 4-6 Ám wide paracingulum offset by 1-2 Ám paracingulum widths, dividing the cyst unequally (epicyst longer than hypocyst) and may be subdivided. Parasulcus expressed by a smooth, deep depression on the hypocyst, extending posteriorly from the paracingulum two thirds the length of the hypocyst, and which may contain an elongate flagellar scar (5-14 Ám long, 2-4 Ám wide). Measurements. Pericyst length 124(142)174 Ám, width 80(94)107 Ám, endocyst length 109(126)153 Ám, width 80(92)106 Ám (38 specimens).
Variability. Cyst size and shape are fairly constant with pericoels at the apices and a narrow pericoel over much of the cyst; only a few specimens are distinctly circumcavate. The parasutural folds delineate many of the epicystal sutures (Fig.9A,E), but are less common on the hypocyst. The periphragm may be densely or sparsely ornamented by irregularly shaped verrucate processes (Fig.9B), except at the apical horn where perforations are common and are generally densely spaced.
Affinities:
Stevens, 1987, p. 194: Scriniodinium prolatum
Scriniodinium prolatum and S. pharo (Duxbury) Davey 1982 both have an elongate, apical perihorn and some parasutural features; however the latter is circumcavate, lacks any periphragm ornamentation and has a short, apical endohorn which extends anteriorly only one quarter to one third the length of the perihorn. S. ceratophorum Cookson & Eisenack 1960 has an elongate, apical perihorn and narrow lateral pericoels; however it has a bluntly rounded, apical endohorn and an extremely short, bluntly rounded hypocyst. Conyaulacysta? Iongicornis (Downie) Sarjeant 1969 has an elongate, apical horn, however it has an autophragm only, the horn is solid and paratabulation is distinct.
NOW Scriniodinium. Originally (and now) Scriniodinium, subsequently Endoscrinium.
Riding and Fensome (2003, p.18) retained this species in Scriniodinium.
Holotype: Stevens, 1987, fig.9A-C
Locus typicus: Exmouth Plateau, W Australia
Stratum typicum: Early Berriasian
Original description: Stevens, 1987, p. 193-194: Scriniodinium prolatum
Cysts proximate, bicavate to circumcavate, roundly kite-shaped, with a long, broad, apical horn. Apical horn generally one quarter to one third the cyst length, consisting of a truncate, distally open perihorn and a rounded, closed endohorn extending one half to three quarters the length of the perihorn. Periphragm and endophragm both less than 1 Ám thick, may be appressed in part, or separated by a 1-4 Ám wide pericoel over much of the cyst, except at the apex and antapex, where the pericoel is 5-18 Ám and 2-8 Ám wide, respectively. Periphragm scabrate, ornamented by irregularly shaped verrucate processes (1-1.5 Ám high and wide), or by perforations which are circular to oval in outline, 1 to 4 Ám in diameter, and commonly concentrated at the apical horn. Endophragm smooth. Archeopyle precingular, type P (3"" only), endo- and periarcheopyles similar in size. Operculum 26-46 Ám long, free, the endo- and periopercula remaining attached after dehiscence.
Paratabulation incomplete, indicated by the archeopyle, the paracingulum and some parasutural folds, formula unknown. Parasutural folds in the periphragm up to 1.5 Ám in height and width, delineating only a few sutures, mainly on the epicyst. Paracingulum expressed by folds in the periphragm up to 3 Ám high and up to 1.5 Ám wide along which verrucae, when present, may be aligned. The 4-6 Ám wide paracingulum offset by 1-2 Ám paracingulum widths, dividing the cyst unequally (epicyst longer than hypocyst) and may be subdivided. Parasulcus expressed by a smooth, deep depression on the hypocyst, extending posteriorly from the paracingulum two thirds the length of the hypocyst, and which may contain an elongate flagellar scar (5-14 Ám long, 2-4 Ám wide). Measurements. Pericyst length 124(142)174 Ám, width 80(94)107 Ám, endocyst length 109(126)153 Ám, width 80(92)106 Ám (38 specimens).
Variability. Cyst size and shape are fairly constant with pericoels at the apices and a narrow pericoel over much of the cyst; only a few specimens are distinctly circumcavate. The parasutural folds delineate many of the epicystal sutures (Fig.9A,E), but are less common on the hypocyst. The periphragm may be densely or sparsely ornamented by irregularly shaped verrucate processes (Fig.9B), except at the apical horn where perforations are common and are generally densely spaced.
Affinities:
Stevens, 1987, p. 194: Scriniodinium prolatum
Scriniodinium prolatum and S. pharo (Duxbury) Davey 1982 both have an elongate, apical perihorn and some parasutural features; however the latter is circumcavate, lacks any periphragm ornamentation and has a short, apical endohorn which extends anteriorly only one quarter to one third the length of the perihorn. S. ceratophorum Cookson & Eisenack 1960 has an elongate, apical perihorn and narrow lateral pericoels; however it has a bluntly rounded, apical endohorn and an extremely short, bluntly rounded hypocyst. Conyaulacysta? Iongicornis (Downie) Sarjeant 1969 has an elongate, apical horn, however it has an autophragm only, the horn is solid and paratabulation is distinct.