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Spinidinium clavus
Spinidinium? clavus Harland, 1973
Originally (and now), Spinidinium, subsequently Spinidinium?, thirdly Volkheimeridium. Questionable assignment: Stover and Evitt (1978, p.125). Sluijs et al. (2009, p.47) questionably retained this species in Spinidinium.
Holotype: Harland, 1973, pl.84, fig.6
Locus typicus: Southern Alberta, Canada
Stratum typicum: Campanian
Original diagnosis: Harland, 1973, p. 674
Cavate cyst, fusiform in shape, made up of two wall layers closely adpressed except at the apex and antapex where pericoels may be evident. Test usually smooth with the presence of occasional discrete granules. Epitract slightly more conical than the hypotract. Prominent apical horn, tapering with a bifid tip; antapical horns acuminate. Sutural ridges, up to 5 µm tall, carry short oblate and acuminate processes. Certain plate areas of the tabulation may be delimited due to sutural development. A tabulation ?4", 1a, ?7", ?4c, 5-6""", ?2"""" indicated. Cingulum planar, sulcus conspicuous extending on to both the epitract and hypotract. Archeopyle indeterminate, but it is almost certain that loss of the conspicuous intercalary plate forms the archeopyle.
Original description: Harland, 1973, p. 675
Cavate cyst often appears proximate because of poor pericoel development. The apex appears to be made up of four apical plates which are separated by large sutural ridges, characteristic of this species. These ridges add to the prominence of the apex. The crests of the ridges carry small oblate and acuminate processes. The precingular plate series appears to consist of five to seven plates, of which plate 4" is conspicuous and polygonal in shape; directly above this plate there is a single rectangular anterior intercalary plate. The cingulum is often the focus for folding and crumpling of the cyst. The post-cingular plate series appears to comprise five or six plates but only certain indeterminate plate boundaries were seen. The hypotract is more rounded than the epitract. The sutural crests are better developed on the epitract than on the hypotract. The range of variation of this species is seen in Plate 84. The most variable feature is the size of the endoblast in relation to periblast.
Dimensions: Holotype: Length 51.0 µm; breadth 29.0 µm. Range: Length 40.0 (45.3) 60.0 µm; breadth 20.0 (26.0) 35.0 µm. Seventeen specimens observed.
Affinities:
Harland, 1973, p. 675: This species is characterized by the nature of the large sutural ridges. It is similar to Palaeoperidinium caulleryi Deflandre 1934 which Deflandre (1966) considers to be a member of the genus Diconodinium. It was not, however, formally combined (re Article 33 of I.C.B.N.). It has peridiniacean affinities with the deflandreoid lineage.
Originally (and now), Spinidinium, subsequently Spinidinium?, thirdly Volkheimeridium. Questionable assignment: Stover and Evitt (1978, p.125). Sluijs et al. (2009, p.47) questionably retained this species in Spinidinium.
Holotype: Harland, 1973, pl.84, fig.6
Locus typicus: Southern Alberta, Canada
Stratum typicum: Campanian
Original diagnosis: Harland, 1973, p. 674
Cavate cyst, fusiform in shape, made up of two wall layers closely adpressed except at the apex and antapex where pericoels may be evident. Test usually smooth with the presence of occasional discrete granules. Epitract slightly more conical than the hypotract. Prominent apical horn, tapering with a bifid tip; antapical horns acuminate. Sutural ridges, up to 5 µm tall, carry short oblate and acuminate processes. Certain plate areas of the tabulation may be delimited due to sutural development. A tabulation ?4", 1a, ?7", ?4c, 5-6""", ?2"""" indicated. Cingulum planar, sulcus conspicuous extending on to both the epitract and hypotract. Archeopyle indeterminate, but it is almost certain that loss of the conspicuous intercalary plate forms the archeopyle.
Original description: Harland, 1973, p. 675
Cavate cyst often appears proximate because of poor pericoel development. The apex appears to be made up of four apical plates which are separated by large sutural ridges, characteristic of this species. These ridges add to the prominence of the apex. The crests of the ridges carry small oblate and acuminate processes. The precingular plate series appears to consist of five to seven plates, of which plate 4" is conspicuous and polygonal in shape; directly above this plate there is a single rectangular anterior intercalary plate. The cingulum is often the focus for folding and crumpling of the cyst. The post-cingular plate series appears to comprise five or six plates but only certain indeterminate plate boundaries were seen. The hypotract is more rounded than the epitract. The sutural crests are better developed on the epitract than on the hypotract. The range of variation of this species is seen in Plate 84. The most variable feature is the size of the endoblast in relation to periblast.
Dimensions: Holotype: Length 51.0 µm; breadth 29.0 µm. Range: Length 40.0 (45.3) 60.0 µm; breadth 20.0 (26.0) 35.0 µm. Seventeen specimens observed.
Affinities:
Harland, 1973, p. 675: This species is characterized by the nature of the large sutural ridges. It is similar to Palaeoperidinium caulleryi Deflandre 1934 which Deflandre (1966) considers to be a member of the genus Diconodinium. It was not, however, formally combined (re Article 33 of I.C.B.N.). It has peridiniacean affinities with the deflandreoid lineage.