Back
Laciniadinium arcticum
From Fensome et al., 2019:
Laciniadinium arcticum (Manum and Cookson, 1964, p.18–19, pl.6, figs.1–4) Lentin and Williams, 1980, p.41. Holotype: Manum and Cookson, 1964, pl.6, fig.1. Originally Diconodinium, subsequently (and now) Laciniadinium. Taxonomic junior synonyms: Diconodinium acutum, according to Morgan (1977, p.126); Laciniadinium williamsii, according to Fensome et al. (2016b, p.54). Age: Cenomanian.
---------------------------------------------------------------------------------------------------
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cenomanian
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 µm long, situated obliquely in relation to the longitudinal axis of the theca. Theca-membrane less than 1 µm thick, two-layered, as most clearly shown at the apices, ornamented with minute granules up to 0.5 µm in diameter. A longitudinal furrow has not been clearly evident.
Dimensions: Holotype: 71 x 45 µm. Range: 50-73 µm long; 32-53 µm 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 µm as against 62-142 µm x 41-72 µm), its smaller apical and antapical processes, the equal size of the epitheca and hypotheca, and the constant presence of the ornamentation.
--------------------------------------------------
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.
--------------------------------------------------
Laciniadinium arcticum (Manum and Cookson, 1964, p.18–19, pl.6, figs.1–4) Lentin and Williams, 1980, p.41. Holotype: Manum and Cookson, 1964, pl.6, fig.1. Originally Diconodinium, subsequently (and now) Laciniadinium. Taxonomic junior synonyms: Diconodinium acutum, according to Morgan (1977, p.126); Laciniadinium williamsii, according to Fensome et al. (2016b, p.54). Age: Cenomanian.
---------------------------------------------------------------------------------------------------
Locus typicus: Graham Island, Arctic Canada
Stratum typicum: Cenomanian
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 µm long, situated obliquely in relation to the longitudinal axis of the theca. Theca-membrane less than 1 µm thick, two-layered, as most clearly shown at the apices, ornamented with minute granules up to 0.5 µm in diameter. A longitudinal furrow has not been clearly evident.
Dimensions: Holotype: 71 x 45 µm. Range: 50-73 µm long; 32-53 µm 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 µm as against 62-142 µm x 41-72 µm), its smaller apical and antapical processes, the equal size of the epitheca and hypotheca, and the constant presence of the ornamentation.
--------------------------------------------------
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.
--------------------------------------------------