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Impagidinium multiplex
Impagidinium multiplexum (Wall and Dale, 1968) Lentin and Williams, 1981
Originally Leptodinium, subsequently (and now) Impagidinium.
Holotype: Wall and Dale, 1968, pl.1, figs.1-6; Jan du Chene et al., 1986, pl.54, figs.7-9
Locus typicus: Ludhan Crag, Royal Society Borehole, Norfolk
Stratum typicum: Ludhamian, Early Pleistocene
Age: Early Pleistocene
Original description: Wall and Dale 1968, p. 318-319
The test is two-layered with an outer microgranular layer forming a series of sultural septa which give an almost perfect reflected tabulation of 3", Oa, 6", ?6g, 5 6"", Ip, 1"", 3 s.p. The arrangement of plate-areas is identical with that found in the modern Gonyaulax spinifera-group (Fig. 1). The archeopyle is simple and precingular (3"). The sutural septa are of low, more or less concordant height over most of the test and do not exceed one-third of the test diameter. The bases of septa are detached from the inner wall layer (as in Pentadinium Ger.) but their distal edges are acute. Peculiarities of this species include a very weakly developed septum between plate-area 6" and the longitudinal furrow and a general reduction of all septa in the furrow region which incorporates three platelets (anterior, median, posterior) of almost equal size. There is usually only a single ventral apical plate-area (I") and the posterior intercalary is large. The cingulum is well developed but transverse septa dividing it into plates are not. Many cells include one to three small waxy globules (around 5µ). The colour is pale brown.
Dimensions: The size range was length 46-62µ, transdiameter 37-53µ and the height of the septa from 3 to 8µ for fifty specimens from 126 ft 9 in. below the borehole surface (Ludhamian).
Comparisons: Leptodinium multiplexum strongly resembles the Oligocene species Pterodinium circumsutum Morg. and Pentadinium laticinctumGer. in general appearance but differs in that these Tertiary species have one large undivided apical plate-area and very incomplete ventral tabulation. In Pterodinium circumsutum Morg. the septa also are higher and weakly serrated. Other Pleistocene species of Leptodinium are readily separable from L. multiplexum.
Originally Leptodinium, subsequently (and now) Impagidinium.
Holotype: Wall and Dale, 1968, pl.1, figs.1-6; Jan du Chene et al., 1986, pl.54, figs.7-9
Locus typicus: Ludhan Crag, Royal Society Borehole, Norfolk
Stratum typicum: Ludhamian, Early Pleistocene
Age: Early Pleistocene
Original description: Wall and Dale 1968, p. 318-319
The test is two-layered with an outer microgranular layer forming a series of sultural septa which give an almost perfect reflected tabulation of 3", Oa, 6", ?6g, 5 6"", Ip, 1"", 3 s.p. The arrangement of plate-areas is identical with that found in the modern Gonyaulax spinifera-group (Fig. 1). The archeopyle is simple and precingular (3"). The sutural septa are of low, more or less concordant height over most of the test and do not exceed one-third of the test diameter. The bases of septa are detached from the inner wall layer (as in Pentadinium Ger.) but their distal edges are acute. Peculiarities of this species include a very weakly developed septum between plate-area 6" and the longitudinal furrow and a general reduction of all septa in the furrow region which incorporates three platelets (anterior, median, posterior) of almost equal size. There is usually only a single ventral apical plate-area (I") and the posterior intercalary is large. The cingulum is well developed but transverse septa dividing it into plates are not. Many cells include one to three small waxy globules (around 5µ). The colour is pale brown.
Dimensions: The size range was length 46-62µ, transdiameter 37-53µ and the height of the septa from 3 to 8µ for fifty specimens from 126 ft 9 in. below the borehole surface (Ludhamian).
Comparisons: Leptodinium multiplexum strongly resembles the Oligocene species Pterodinium circumsutum Morg. and Pentadinium laticinctumGer. in general appearance but differs in that these Tertiary species have one large undivided apical plate-area and very incomplete ventral tabulation. In Pterodinium circumsutum Morg. the septa also are higher and weakly serrated. Other Pleistocene species of Leptodinium are readily separable from L. multiplexum.