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Laciniadinium arcticum
Laciniadinium arcticum (Manum and Cookson, 1964) Lentin and Williams, 1980
Originally Diconodinium, subsequently (and now) Laciniadinium.
Tax. sr. synonym of Diconodinium acutum Jain and Millepied, 1973, according to Morgan, 1977.
Ioannides, 1986, retained this species in Diconodinium Eisenack and Cookson, 1960. Harker and Sarjeant in Harker et al., 1990, retained it in Laciniadinium.
Holotype: Manum and Cookson, 1964, pl.6, fig.1
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cenomanian
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G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Laciniadinium arcticum (Manum and Cookson, 1964) Lentin and Williams, 1980, is broadly fusiform, almost equally divided by a relatively broad cingulum. Apical horn short, truncate and sometimes toothed. Antapical spine 3-6 µm long, situated obliquely. Wall minutely granulate. Archeopyle combination, type (AIP)@, resulting from loss of 3', 1-3a, and 3-5". Size: Length 50-73 µm, width 32-53 µm.
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Original description: Manum and Cookson, 1964, p. 18-19: Diconodinium arcticum
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 1Ám 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: 71 x 45 Ám. Range: 50-73 Ám long; 32-53 Ám broad.
Affinities:
Manum and Cookson, 1964, p. 19: Diconodinium arcticum
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 (50-73 x 32-53 Ám as against 62-142 Ám x 41-72 Ám), its smaller apical and antapical processes, the equal size of the epitheca and hypotheca, and the constant presence of the ornamentation.
Originally Diconodinium, subsequently (and now) Laciniadinium.
Tax. sr. synonym of Diconodinium acutum Jain and Millepied, 1973, according to Morgan, 1977.
Ioannides, 1986, retained this species in Diconodinium Eisenack and Cookson, 1960. Harker and Sarjeant in Harker et al., 1990, retained it in Laciniadinium.
Holotype: Manum and Cookson, 1964, pl.6, fig.1
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cenomanian
--------------------------------------------------
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999 - LPP VIEWER CD-ROM 99.5.
Laciniadinium arcticum (Manum and Cookson, 1964) Lentin and Williams, 1980, is broadly fusiform, almost equally divided by a relatively broad cingulum. Apical horn short, truncate and sometimes toothed. Antapical spine 3-6 µm long, situated obliquely. Wall minutely granulate. Archeopyle combination, type (AIP)@, resulting from loss of 3', 1-3a, and 3-5". Size: Length 50-73 µm, width 32-53 µm.
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Original description: Manum and Cookson, 1964, p. 18-19: Diconodinium arcticum
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 1Ám 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: 71 x 45 Ám. Range: 50-73 Ám long; 32-53 Ám broad.
Affinities:
Manum and Cookson, 1964, p. 19: Diconodinium arcticum
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 (50-73 x 32-53 Ám as against 62-142 Ám x 41-72 Ám), its smaller apical and antapical processes, the equal size of the epitheca and hypotheca, and the constant presence of the ornamentation.