Back
Leptodinium cristatum
Leptodinium cristatum May, 1980
Now Impagidinium. Originally Leptodinium, subsequently (and now) Impagidinium.
Sr. homonym of Leptodinium cristatum (Riley in Fisher and Riley, 1980) Lentin and Williams, 1981.
Holotype: May, 1980, pl.5, fig.16-20
Locus typicus: Atlantic Highlands, New Jersey, U.S.A.
Stratum typicum: Campanian-Maastrichtian
Original description: May, 1980, p.57
Spheroidal cysts, circular in equatorial section. Bilayered; endophragm smooth; periphragm smooth, formed into sutural folds at plate boundaries, which generally appear as high, thin, uneven crests, and are generally higher at gonal positions. Crests often incompletely developed in the apical and sulcal series: boundary between 1" and 4" not evident; boundary between as and ms weakly developed. Reflected tabulation 3--4", 6", 6c, 5""", 1p, 1"""", as, ms, ps. Cingular plates hexagonal on dorsal surface, more quadrolateral on ventral surface; cingulum levorotatory, ca. one cingulum width offset. Sulcus begins ca. one cingulum width above 1c, extends to 1"""", and is 1--2 cingulum widths wide, widening antapically. Archeopyle precingular (Pype P). Sutural folds of 3""" offset to left of those of 3", giving asymmetrical appearance to dorsal surface.
Discussion: Tabulation is probably standard Gonyaulax-type tabulation; however, four apical plates have not yet been observed. Because other sutural folds in the apical series are occasionally incompletely developed, and because the as--ms is incompletely developed, it is assumed that the 1"--4" boundary is likely also undeveloped in this species, but does exist.
Dimensions: Holotype--L x W 43 x 40 Ám Observed range (18 specimens measured): length 37--50 Ám, width 31--49 Ám; crest height 3--7 Ám; wall layers ca. 2 Ám, endophragm thicker than periphragm.
Affinities:
May, 1980, p.57: Leptodinium victorianum Cookson and Eisenack 1965 is similar to L. cristatum in overall construction, plate shape and arrangement. L. victorianum differs by lacking the lower sutural folds of the 1c and 6c plate equivalents, being about twice as large, and generally displaying four apical plates, although the ventrally directed 1"--4" boundary may also occasionally be lacking. L. patulum Wall (1967) is also similar to L. cristatum in overall construction, plate-shape and arrangement, size range, and has complete or incomplete suture development in the apical and sulcal series. L. patulum, however, lacks the lower sutural folds on the 1c and 6c, and lacks a sutural fold on the sulcal-side of the 6". Because L. cristatum has complete sutural fold development on all ventral plates of the precingular, cingular, and postcingular series, and 1p, it is apparently distinctive. Considering the close relationships with the above compared species a lineage is suggested. The more complete tabulation of L. cristatum being ancestral (Campanian-Maestrichtian), the slightly less complete ventral tabulation of L. victorianum Cookson and Eisenack being somewhat younger (Eocene), and the much less complete ventral tabulation of L. patulum Wall being youngest (Miocene-Holocene) (Text-fig. 11).
Now Impagidinium. Originally Leptodinium, subsequently (and now) Impagidinium.
Sr. homonym of Leptodinium cristatum (Riley in Fisher and Riley, 1980) Lentin and Williams, 1981.
Holotype: May, 1980, pl.5, fig.16-20
Locus typicus: Atlantic Highlands, New Jersey, U.S.A.
Stratum typicum: Campanian-Maastrichtian
Original description: May, 1980, p.57
Spheroidal cysts, circular in equatorial section. Bilayered; endophragm smooth; periphragm smooth, formed into sutural folds at plate boundaries, which generally appear as high, thin, uneven crests, and are generally higher at gonal positions. Crests often incompletely developed in the apical and sulcal series: boundary between 1" and 4" not evident; boundary between as and ms weakly developed. Reflected tabulation 3--4", 6", 6c, 5""", 1p, 1"""", as, ms, ps. Cingular plates hexagonal on dorsal surface, more quadrolateral on ventral surface; cingulum levorotatory, ca. one cingulum width offset. Sulcus begins ca. one cingulum width above 1c, extends to 1"""", and is 1--2 cingulum widths wide, widening antapically. Archeopyle precingular (Pype P). Sutural folds of 3""" offset to left of those of 3", giving asymmetrical appearance to dorsal surface.
Discussion: Tabulation is probably standard Gonyaulax-type tabulation; however, four apical plates have not yet been observed. Because other sutural folds in the apical series are occasionally incompletely developed, and because the as--ms is incompletely developed, it is assumed that the 1"--4" boundary is likely also undeveloped in this species, but does exist.
Dimensions: Holotype--L x W 43 x 40 Ám Observed range (18 specimens measured): length 37--50 Ám, width 31--49 Ám; crest height 3--7 Ám; wall layers ca. 2 Ám, endophragm thicker than periphragm.
Affinities:
May, 1980, p.57: Leptodinium victorianum Cookson and Eisenack 1965 is similar to L. cristatum in overall construction, plate shape and arrangement. L. victorianum differs by lacking the lower sutural folds of the 1c and 6c plate equivalents, being about twice as large, and generally displaying four apical plates, although the ventrally directed 1"--4" boundary may also occasionally be lacking. L. patulum Wall (1967) is also similar to L. cristatum in overall construction, plate-shape and arrangement, size range, and has complete or incomplete suture development in the apical and sulcal series. L. patulum, however, lacks the lower sutural folds on the 1c and 6c, and lacks a sutural fold on the sulcal-side of the 6". Because L. cristatum has complete sutural fold development on all ventral plates of the precingular, cingular, and postcingular series, and 1p, it is apparently distinctive. Considering the close relationships with the above compared species a lineage is suggested. The more complete tabulation of L. cristatum being ancestral (Campanian-Maestrichtian), the slightly less complete ventral tabulation of L. victorianum Cookson and Eisenack being somewhat younger (Eocene), and the much less complete ventral tabulation of L. patulum Wall being youngest (Miocene-Holocene) (Text-fig. 11).