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Charlesdowniea variabilis
Charlesdowniea variabilis, (Bujak in Bujak et al., 1980), Lentin and Vozzhennikova, 1989
Originally Kisselevia, subsequently Charlesdowniea, thirdly (and now) Michouxdinium.
Holotype: Bujak et al., 1980, pl.17, figs.1-3.
Locus typicus: Barton, Hamshire, England
Stratum typicum: Late Eocene
Age: Mid Eocene (see Aubry, 1986).
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Original description as Kisselovia variabilis: [Bujak in Bujak et al., 1980, p. 67]:
Diagnosis:
Pericyst ambitus rhomboidal. Epicyst commonly shorter than the hypocyst.
Apical horn indistinct, poorly developed, sometimes with a distal tubercle. Pericingular horns poorly to well developed, causing fluctuations in length: breadth ratio of 1: 0,8 to 1:1,1. Antapex prolonged into a small left horn, the right being absent or reduced to a slight swelling of the pericyst. Endocyst ambitus circular, oval, or rounded rhomboidal with a length:breadth ratio of 1:0 8 to 1:12. Cornucavate pericoels are connected by a narrow ambital pericoel.
The processes are arranged in simulate complexes and within the complexes are united distally by a trabeculate network of variable interconnection and complexity. The networks may be single trabeculae between processes of a simulate complex or a complexly interconnected network of trabeculae uniting all the processes of a paraplate. All morphological intergradations may be present on individual specimens. Endophragm surface smooth, may be granulate near the horns. Process complexes reflect a paratabulation of 4', 3a, 7", xc, 5''', 2'''', xs, with paraplate 4" being extremely broad relative to 2a.
Pericingulum and perisulcus delineated by process complexes.
Periarchaeopyle quadra intercalary, formed by the detachment of paraplate 2a. Perioperculum free. Endoarchaeopyle adjacent to the periarchaeopyle and of the same size and shape. Endoperculum detached.
Dimensions:
Pericyst length=80-117 µm, breadth=82-124 µm. Endocyst length=65 92 µm, breadth=66-100 µm. Process length up to 10 µm.
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Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999
Charlesdowniea variabilis (Bujak in Bujak et al., 1980) Lentin and Vozzhennikova, 1989. This species, according to Bujak (1980, p.67), has a poorly developed apical horn. Pericingular horns poorly to well developed, antapex prolonged into a short left horn, the right being absent or reduced. Cornucavate with narrow ambital pericoel. Processes forming simulate complexes and united within by a trabeculate network of variable interconnection and complexity. The networks may be single trabeculae between processes or simulate complex or a complexly interconnected network of trabeculae uniting all the processes of a paraplate. Perioperculum free. It is intermediate between C.tenuivirgula and C.reticulata.
Size: pericyst length 80-117 µm, width 82-124 µm, endocyst length 65-92 µm, width 66-100 µm, process length up to 10 µm.
Originally Kisselevia, subsequently Charlesdowniea, thirdly (and now) Michouxdinium.
Holotype: Bujak et al., 1980, pl.17, figs.1-3.
Locus typicus: Barton, Hamshire, England
Stratum typicum: Late Eocene
Age: Mid Eocene (see Aubry, 1986).
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Kisselovia variabilis: [Bujak in Bujak et al., 1980, p. 67]:
Diagnosis:
Pericyst ambitus rhomboidal. Epicyst commonly shorter than the hypocyst.
Apical horn indistinct, poorly developed, sometimes with a distal tubercle. Pericingular horns poorly to well developed, causing fluctuations in length: breadth ratio of 1: 0,8 to 1:1,1. Antapex prolonged into a small left horn, the right being absent or reduced to a slight swelling of the pericyst. Endocyst ambitus circular, oval, or rounded rhomboidal with a length:breadth ratio of 1:0 8 to 1:12. Cornucavate pericoels are connected by a narrow ambital pericoel.
The processes are arranged in simulate complexes and within the complexes are united distally by a trabeculate network of variable interconnection and complexity. The networks may be single trabeculae between processes of a simulate complex or a complexly interconnected network of trabeculae uniting all the processes of a paraplate. All morphological intergradations may be present on individual specimens. Endophragm surface smooth, may be granulate near the horns. Process complexes reflect a paratabulation of 4', 3a, 7", xc, 5''', 2'''', xs, with paraplate 4" being extremely broad relative to 2a.
Pericingulum and perisulcus delineated by process complexes.
Periarchaeopyle quadra intercalary, formed by the detachment of paraplate 2a. Perioperculum free. Endoarchaeopyle adjacent to the periarchaeopyle and of the same size and shape. Endoperculum detached.
Dimensions:
Pericyst length=80-117 µm, breadth=82-124 µm. Endocyst length=65 92 µm, breadth=66-100 µm. Process length up to 10 µm.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Notes:
G.L. Williams short notes on species, Mesozoic-Cenozoic dinocyst course, Urbino, Italy, May 17-22, 1999
Charlesdowniea variabilis (Bujak in Bujak et al., 1980) Lentin and Vozzhennikova, 1989. This species, according to Bujak (1980, p.67), has a poorly developed apical horn. Pericingular horns poorly to well developed, antapex prolonged into a short left horn, the right being absent or reduced. Cornucavate with narrow ambital pericoel. Processes forming simulate complexes and united within by a trabeculate network of variable interconnection and complexity. The networks may be single trabeculae between processes or simulate complex or a complexly interconnected network of trabeculae uniting all the processes of a paraplate. Perioperculum free. It is intermediate between C.tenuivirgula and C.reticulata.
Size: pericyst length 80-117 µm, width 82-124 µm, endocyst length 65-92 µm, width 66-100 µm, process length up to 10 µm.