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Leptodinium acneum
Leptodinium acneum (Snape, 1992)
Holotype: Snape, 1992, figs.7L-M (length 108 μm, width 85 μm, apical horn 2 μm)
Locus typicus: Sharp Valley, James Ross Island, Antarctica
Stratum typicum: Middle Tithonian
Diagnosis: Snape, 1992, p. 275
Cyst proximate, acavate and polygonal in outline with a short apical horn. Paratabulation gonyaulacacean indicated by high parasutural crests. Kofoidian formula: 4", 2a, 6"", 6c, 6""", lp, 1"". There are no parasulcal paraplates. Intratabular areas are granulate. The archaeopyle is precingular, type P.
Description: Snape, 1992, p. 275
The cyst is proximate? acavate, polygonal in outline in dorso-ventral view and has a short apical horn 2-5 μm in length (B type ambitus of Jan du Chêne et al. 1986). The autophragm has an ornament of high parasutural crests up to 5 μm high and evenly spaced grana of c. 1 μm diameter and 1 μm high. The archaeopyle is precingular, type P, formed by the loss of the 3"" paraplate. The paracingulum is offset at the parasulcus and there are no parasulcal paraplates.
Dimiensions (μ m): Min-Mean-Max:
Overall length: 97-101-110
Overall width 70-79-89
Apical horn length2-3-5
Specimens measured: 20
Affinities: Snape, 1992, p. 275
This species is characterized by its elongate polygonal outline, short apical horn, tall smooth parasutural crests, granulate intratabular ornament and the non-paratabulate parasulcal area. Morphologically similar species are L. hyalodermopse and L. setcheyense. The former has no intratabular ornament. The latter does possess intratabular ornament, but differs in the apical and parasulcal regions, where the apical horn is considerably longer and parasulcal paraplates are delineated by parasutural septa.
Holotype: Snape, 1992, figs.7L-M (length 108 μm, width 85 μm, apical horn 2 μm)
Locus typicus: Sharp Valley, James Ross Island, Antarctica
Stratum typicum: Middle Tithonian
Diagnosis: Snape, 1992, p. 275
Cyst proximate, acavate and polygonal in outline with a short apical horn. Paratabulation gonyaulacacean indicated by high parasutural crests. Kofoidian formula: 4", 2a, 6"", 6c, 6""", lp, 1"". There are no parasulcal paraplates. Intratabular areas are granulate. The archaeopyle is precingular, type P.
Description: Snape, 1992, p. 275
The cyst is proximate? acavate, polygonal in outline in dorso-ventral view and has a short apical horn 2-5 μm in length (B type ambitus of Jan du Chêne et al. 1986). The autophragm has an ornament of high parasutural crests up to 5 μm high and evenly spaced grana of c. 1 μm diameter and 1 μm high. The archaeopyle is precingular, type P, formed by the loss of the 3"" paraplate. The paracingulum is offset at the parasulcus and there are no parasulcal paraplates.
Dimiensions (μ m): Min-Mean-Max:
Overall length: 97-101-110
Overall width 70-79-89
Apical horn length2-3-5
Specimens measured: 20
Affinities: Snape, 1992, p. 275
This species is characterized by its elongate polygonal outline, short apical horn, tall smooth parasutural crests, granulate intratabular ornament and the non-paratabulate parasulcal area. Morphologically similar species are L. hyalodermopse and L. setcheyense. The former has no intratabular ornament. The latter does possess intratabular ornament, but differs in the apical and parasulcal regions, where the apical horn is considerably longer and parasulcal paraplates are delineated by parasutural septa.