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Leptodinium posterosulcatum
Leptodinium posterosulcatum Snape, 1992
Holotype: Snape, 1992, fig.7i (length 90 Ám, width 72 Ám)
Locus typicus: Sharp Valley, James Ross Island, Antarctica
Stratum typicum: Middle Tithonian
Diagnosis: Snape, 1992, p. 275
Cyst proximate, acavate and subspherical-ovoidal in shape. Paratabulation gonyaulacacean indicated by the low parasutural crests.
Kofoidian formula: 4", 1a, 6"", 6c, 6""", 1p, 1"""". The posterior parasulcal paraplate (ps) is the only paraplate present in the parasulcus. Intratabular areas are smooth. The archaeopyle is precingular, type P.
Description: Snape, 1992, p. 275
The cyst proximate and acavate, subspherical-ovoidal. The autophragm is thin and ornamented with low, smooth parasutural septa, 1-3 Ám in height. Intratabular areas are smooth. The archaeopyle is precingular, type P, formed by loss of the 3"" paraplate. The paracingulum is offset at the parasulcus. One parasulcal paraplate, the posterior parasulcal (ps), is present.
Dimensions ( Ám): MinMeanMax
Overalllength 657097
Overall width 636976
Specimens measured: 20
Affinities; Snape, 1992, p. 275
The subspherical-ovoidal outline, low parasutural crests, smooth intratabular autophragm and the presence of only the posterior parasulcal paraplate in the parasulcus distinguishes L. posterosulcatum from other species of the genus. It is similar to L. mirabile, but the parasulcal paraplates are well defined in L. mirabile. Other similar species are L. freakei and L. millioudi which were described by Sarjeant (1963). The latter species differs from L. posterosulcatum in that the parasulcal areawith six parasulcal paraplates is clearly defined. The illustration of L. freakei shows the same parasulcal arrangement with only the ps paraplate defined. Leptodinium freakei differs from L. posterosulcatum sp. nov. in having moderate to high parasutural septa that are perforate. Leptodinium subtile differs by having high suturocavate parasutural ornament and no parasulcal paraplates.
Holotype: Snape, 1992, fig.7i (length 90 Ám, width 72 Ám)
Locus typicus: Sharp Valley, James Ross Island, Antarctica
Stratum typicum: Middle Tithonian
Diagnosis: Snape, 1992, p. 275
Cyst proximate, acavate and subspherical-ovoidal in shape. Paratabulation gonyaulacacean indicated by the low parasutural crests.
Kofoidian formula: 4", 1a, 6"", 6c, 6""", 1p, 1"""". The posterior parasulcal paraplate (ps) is the only paraplate present in the parasulcus. Intratabular areas are smooth. The archaeopyle is precingular, type P.
Description: Snape, 1992, p. 275
The cyst proximate and acavate, subspherical-ovoidal. The autophragm is thin and ornamented with low, smooth parasutural septa, 1-3 Ám in height. Intratabular areas are smooth. The archaeopyle is precingular, type P, formed by loss of the 3"" paraplate. The paracingulum is offset at the parasulcus. One parasulcal paraplate, the posterior parasulcal (ps), is present.
Dimensions ( Ám): MinMeanMax
Overalllength 657097
Overall width 636976
Specimens measured: 20
Affinities; Snape, 1992, p. 275
The subspherical-ovoidal outline, low parasutural crests, smooth intratabular autophragm and the presence of only the posterior parasulcal paraplate in the parasulcus distinguishes L. posterosulcatum from other species of the genus. It is similar to L. mirabile, but the parasulcal paraplates are well defined in L. mirabile. Other similar species are L. freakei and L. millioudi which were described by Sarjeant (1963). The latter species differs from L. posterosulcatum in that the parasulcal areawith six parasulcal paraplates is clearly defined. The illustration of L. freakei shows the same parasulcal arrangement with only the ps paraplate defined. Leptodinium freakei differs from L. posterosulcatum sp. nov. in having moderate to high parasutural septa that are perforate. Leptodinium subtile differs by having high suturocavate parasutural ornament and no parasulcal paraplates.