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Laciniadinium biconiculum
Laciniadinium biconiculum McIntyre, 1975
Holotype: McIntyre, 1975, pl.4, fig.5-6
Locus typicus: Horton River, N.W.T., Canada
Stratum typicum: Campanian
Original description: McIntyre, 1975, p. 71
Cyst proximate, biconical in dorsoventral view; epitract and hypotract of approximately equal size. Apical projection is short with a blunt top and 2 short papillae. The 1 antapical horn (left?) is about 8 Ám long and sharp pointed.
Cingulum 4-6 Ám wide, with its edges marked by low ridges. Sulcus rarely clearly seen. The archeopyle is of the 313P type formed by the 3 intercalary and the precingular reflected plates 3"", 4"", 5"". Operculum remains attached at cingulum as a flap, which is usually folded. The intercalary reflected plates are small because of the conical nature of the epitract. No other visible indications of tabulation. One wall layer (autophragm), about 1/2 Ám thick, is present. Ornamentation consists of small granules less than lum in size and ridges of the same width and height as the granules, but of varying lengths. Granules and ridges often arranged in rows and give cyst a somewhat striate appearance.
Size: Holotype, 78 Ám long, 53 Ám wide; range, 55-85 Ám long, 34-53 Ám wide.
Affinities:
McIntyre, 1975, p. 71: L. biconiculum differs from L. orbiculatum in having a smaller
size and conical shape. L. biconiculum has the same shape as some species of Diconodinium, but an archeopyle has been reported in only one species of Diconodinium. D. firmum was considered by Harland (1973) to have a precingular archeopyle, but his illustrations suggest that the archeopyle for this species could be of the 313P type. Specimens of D. firmum seen in the Horton River section did not possess an obvious archeopyle. D. rhombiformi Vozzhennikova (1967) is imilar to L. biconiculum in shape, but it is smaller and has well-defined areas that are divided by smooth or finely serrated ridges. No obvious pattern of areas on epitract and hypotract can be seen in L. biconiculum.
Holotype: McIntyre, 1975, pl.4, fig.5-6
Locus typicus: Horton River, N.W.T., Canada
Stratum typicum: Campanian
Original description: McIntyre, 1975, p. 71
Cyst proximate, biconical in dorsoventral view; epitract and hypotract of approximately equal size. Apical projection is short with a blunt top and 2 short papillae. The 1 antapical horn (left?) is about 8 Ám long and sharp pointed.
Cingulum 4-6 Ám wide, with its edges marked by low ridges. Sulcus rarely clearly seen. The archeopyle is of the 313P type formed by the 3 intercalary and the precingular reflected plates 3"", 4"", 5"". Operculum remains attached at cingulum as a flap, which is usually folded. The intercalary reflected plates are small because of the conical nature of the epitract. No other visible indications of tabulation. One wall layer (autophragm), about 1/2 Ám thick, is present. Ornamentation consists of small granules less than lum in size and ridges of the same width and height as the granules, but of varying lengths. Granules and ridges often arranged in rows and give cyst a somewhat striate appearance.
Size: Holotype, 78 Ám long, 53 Ám wide; range, 55-85 Ám long, 34-53 Ám wide.
Affinities:
McIntyre, 1975, p. 71: L. biconiculum differs from L. orbiculatum in having a smaller
size and conical shape. L. biconiculum has the same shape as some species of Diconodinium, but an archeopyle has been reported in only one species of Diconodinium. D. firmum was considered by Harland (1973) to have a precingular archeopyle, but his illustrations suggest that the archeopyle for this species could be of the 313P type. Specimens of D. firmum seen in the Horton River section did not possess an obvious archeopyle. D. rhombiformi Vozzhennikova (1967) is imilar to L. biconiculum in shape, but it is smaller and has well-defined areas that are divided by smooth or finely serrated ridges. No obvious pattern of areas on epitract and hypotract can be seen in L. biconiculum.