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Diconodinium arcticum
Diconodinium arcticum Manum and Cookson, 1964
Now Laciniadinium. Originally Diconodinium, subsequently (and now) Laciniadinium.
Tax. sr. synonym of Diconodinium acutum Jain and Millepied, 1973, according to Morgan, 1977.
Lentin and Williams, 1980, transferred this species to Laciniadinium McIntyre, 1975. Ioannides, 1986, retained it in Diconodinium. Harker and Sarjeant in Harker et al., 1990, agreed with Lentin and Williams, 1980.
Holotype: Manum and Cookson, 1964, pl.6, fig.1
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cenomanian
Original description: Manum and Cookson, 1964, p. 18-19
Shell broadly fusiform with one side slightly longer and more convex than the other, almost equally divided by a relatively broad girdle. Apical horn short, truncate and sornetimes toothed, antapical spine 3-6 Ám long, situated obliquely in relation to the longitudinal axis of the theca. Theca-membrane less than 1Á thick, two-layered, as most clearly shown at the apices, ornamented whith minute granules up to 0.5 Ám in diameter. A longitudinal furrow has not been clearly evident.
Dimensions: Holotype: 71x45 Ám. Range: 50-73 Ám long; 32-53 Ám, broad.
Affinities:
Manum and Cookson, 1964, p. 19: The genus Diconodinium is readily recognizable by the more or less fusiform shape of the thin-walled theca, the small median apical process, the short antapical spine, and the absence of a capsule (unless the inner wall is regarded as delimiting a capsule which fills the theca except near both apical and antapical processes). Six species have already been distinguished (Eisenack & Cookson 1960), mainly on the basis of the ornamentation which consists of variously spaced granules or small processes. Of these species D. arcticum comes closest to D. glabrum E. & C., the differences between them being the much lower size-range in D. arcticum (50-73x32-53 Ám as against 62-142x41-72 Ám), its smaller apical and antapical processes, the equal size of the epitheca and hypotheca, and the constant presence of the ornamentation.
Now Laciniadinium. Originally Diconodinium, subsequently (and now) Laciniadinium.
Tax. sr. synonym of Diconodinium acutum Jain and Millepied, 1973, according to Morgan, 1977.
Lentin and Williams, 1980, transferred this species to Laciniadinium McIntyre, 1975. Ioannides, 1986, retained it in Diconodinium. Harker and Sarjeant in Harker et al., 1990, agreed with Lentin and Williams, 1980.
Holotype: Manum and Cookson, 1964, pl.6, fig.1
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cenomanian
Original description: Manum and Cookson, 1964, p. 18-19
Shell broadly fusiform with one side slightly longer and more convex than the other, almost equally divided by a relatively broad girdle. Apical horn short, truncate and sornetimes toothed, antapical spine 3-6 Ám long, situated obliquely in relation to the longitudinal axis of the theca. Theca-membrane less than 1Á thick, two-layered, as most clearly shown at the apices, ornamented whith minute granules up to 0.5 Ám in diameter. A longitudinal furrow has not been clearly evident.
Dimensions: Holotype: 71x45 Ám. Range: 50-73 Ám long; 32-53 Ám, broad.
Affinities:
Manum and Cookson, 1964, p. 19: The genus Diconodinium is readily recognizable by the more or less fusiform shape of the thin-walled theca, the small median apical process, the short antapical spine, and the absence of a capsule (unless the inner wall is regarded as delimiting a capsule which fills the theca except near both apical and antapical processes). Six species have already been distinguished (Eisenack & Cookson 1960), mainly on the basis of the ornamentation which consists of variously spaced granules or small processes. Of these species D. arcticum comes closest to D. glabrum E. & C., the differences between them being the much lower size-range in D. arcticum (50-73x32-53 Ám as against 62-142x41-72 Ám), its smaller apical and antapical processes, the equal size of the epitheca and hypotheca, and the constant presence of the ornamentation.