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Leptodinium tenuicornutum
Leptodinium? tenuicornutum Cookson and Eisenack, 1962
Originally Leptodinium, subsequently Gonyaulacysta, thirdly (and now) Leptodinium?.
Sarjeant, 1969, transferred this species to Gonyaulacysta Deflandre, 1964. Stover and Evitt, 1978, p.160) retained it in Leptodinium and considered it to be a provisionally accepted species of this genus.
The species is based on a single specimen.
Holotype: Cookson and Eisenack, 1962, pl.3, figs. 12-13, text-figs.1a-b
Locus typicus: Australia, Perth Basin, Regan"s Ford on Moore River
Stratum typicum: Albian
Original diagnosis: Cookson and Eisenack, 1962, p.487
Shell small, broadly oval, divided by a relatively broad, strongly helicoid girdle with low borders into a somewhat conical epitheca and a nearly hemispherical hypotheca. Epitheca provided with a hollow membranous horn. Longitudinal furrow rather broad. Plates finely dotted, bordered bylow membranous ledges which are more pronounced in the median plane, especially at the antapex. Pylome formed by the detachment of plate 3". Tabulation: 3"?, 6", 5""", 1"""".
Dimensions: Holotype: 55 Ám long, 48 Ám broad.
Affinities:
Cookson and Eisenack, 1962, p.487: The single specimen agrees with Klement" s genus Leptodinium in having only five postequatorial plates and an undivided longitudinal furrow which extends from plate 1" to plate 1"""" . However, it differs from Leptodinium in having a membranous horn and higher borders to the plates, especially those of the antapical region, than allowed for in the generic description. Also plate 1p seems to be missing.
Since the closely related genus Gonyaulax contains species both with and without apical horns, there seems no reason why the genus Leptodinium should not be enlarged to include horned forms. However, with only one available specimen, this idea cannot, at present, be prosecuted further.
Originally Leptodinium, subsequently Gonyaulacysta, thirdly (and now) Leptodinium?.
Sarjeant, 1969, transferred this species to Gonyaulacysta Deflandre, 1964. Stover and Evitt, 1978, p.160) retained it in Leptodinium and considered it to be a provisionally accepted species of this genus.
The species is based on a single specimen.
Holotype: Cookson and Eisenack, 1962, pl.3, figs. 12-13, text-figs.1a-b
Locus typicus: Australia, Perth Basin, Regan"s Ford on Moore River
Stratum typicum: Albian
Original diagnosis: Cookson and Eisenack, 1962, p.487
Shell small, broadly oval, divided by a relatively broad, strongly helicoid girdle with low borders into a somewhat conical epitheca and a nearly hemispherical hypotheca. Epitheca provided with a hollow membranous horn. Longitudinal furrow rather broad. Plates finely dotted, bordered bylow membranous ledges which are more pronounced in the median plane, especially at the antapex. Pylome formed by the detachment of plate 3". Tabulation: 3"?, 6", 5""", 1"""".
Dimensions: Holotype: 55 Ám long, 48 Ám broad.
Affinities:
Cookson and Eisenack, 1962, p.487: The single specimen agrees with Klement" s genus Leptodinium in having only five postequatorial plates and an undivided longitudinal furrow which extends from plate 1" to plate 1"""" . However, it differs from Leptodinium in having a membranous horn and higher borders to the plates, especially those of the antapical region, than allowed for in the generic description. Also plate 1p seems to be missing.
Since the closely related genus Gonyaulax contains species both with and without apical horns, there seems no reason why the genus Leptodinium should not be enlarged to include horned forms. However, with only one available specimen, this idea cannot, at present, be prosecuted further.