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Astrocysta cretacea
Astrocysta cretacea, (Pocock, 1962); Emendation: Davey, 1970
NOW Palaeoperidinium. Originally Palaeoperidinium (name not validly published), subsequently Astrocysta, thirdly Lejeunia? (combination illegitimate), fourthly Subtilisphaera, fifthly (and now) Palaeoperidinium.
Taxonomic junior synonyms: Lejeunia (as Palaeoperidinium) ampla, according to Harker and Sarjeant in Harker et al. (1990, p.128); and Astrocysta (subsequently Palaeoperidinium) manumcooksonii, according to Lentin and Williams (1976, p.110).
The name Palaeoperidinium cretaceum was not validly published in Pocock (1962) since the generic name Palaeoperidinium was not validly published until 1967. The name Astrocysta cretacea was not validly published in Sarjeant (1967b, p.243) since the generic name Astrocysta was not validly published until 1970. Davey (1970, p.359), while validating this name, proposed an "emended diagnosis".
Age: Albian-Aptian
Holotype: Pocock, 1962, pl.14, figs.219-221
Paratype: Pocock, 1963
Locus typicus: Imperial Murrey Test Hole No.6, W Canada
Stratum typicum: Aptian-Albian
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Original description as Palaeoperidinium cretaceum: [Pocock 1962, p. 80]:
Diagnosis:
Theca longer than it is broad, ellipsoidal; epitheca long, conical tapering to a point and may or may not be surmounted by a solid apical horn; equatorial girdle well developed, helicoid; hypotheca more or less dome shaped, terminated by two hypothecal spines, one always being longer than the other. Thecal wall thin and transparent, pale yellow or colourless, with no visible system of plates; theca is either scabrate or finely granulose and, in well preserved specimens, usually contains yellow green rounded crystalline bodies; spherical cysts have been observed with the theca of some specimens.
Dimensions:
Range: Length: 81-95 µm; Breadth: 50-69 µm; Length of longer hypothecal spine: 12-25 µm; Length of shorter hypothecal spine: 4-10 µm.
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Emended descriptions:
Davey, 1970, p.359-360:
Diagnosis:
Shell pentagonal; epitract triangular, with broadly conical apical horn; hypotract bearing two conical antapical horns of unequal length. Outer membranes thin, enclosing inner body of similar shape.
Cingulum marked by low ridges.
Weak tabulation sometimes developed, marked by low thickenings of periphragm.
Outline of anterior intercalary plate 2a usually present, but in plate typically in place.
Dimensions:
Range: Overall length: 86-118 µm; Overall width: 57-82 µm. Number of specimens measured: 8.
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Davey, 1970, p.360:
Description:
The apical and two antapical horns are well developed, the latter differing in size from one another. The outer membrane is extremely thin, wrinkled and often possess slight thickenings which occasionally bear small pointed spines. These thickenings partially outline a tabulation which resembles the Peridinium-type tabulation described by Manum (1963). The cingulum is bordered by two low ridges and is only slightly laevo-rotatory. An archaeopyle has never been observed but the outline of paraplate 2a is usually present.
NOW Palaeoperidinium. Originally Palaeoperidinium (name not validly published), subsequently Astrocysta, thirdly Lejeunia? (combination illegitimate), fourthly Subtilisphaera, fifthly (and now) Palaeoperidinium.
Taxonomic junior synonyms: Lejeunia (as Palaeoperidinium) ampla, according to Harker and Sarjeant in Harker et al. (1990, p.128); and Astrocysta (subsequently Palaeoperidinium) manumcooksonii, according to Lentin and Williams (1976, p.110).
The name Palaeoperidinium cretaceum was not validly published in Pocock (1962) since the generic name Palaeoperidinium was not validly published until 1967. The name Astrocysta cretacea was not validly published in Sarjeant (1967b, p.243) since the generic name Astrocysta was not validly published until 1970. Davey (1970, p.359), while validating this name, proposed an "emended diagnosis".
Age: Albian-Aptian
Holotype: Pocock, 1962, pl.14, figs.219-221
Paratype: Pocock, 1963
Locus typicus: Imperial Murrey Test Hole No.6, W Canada
Stratum typicum: Aptian-Albian
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Palaeoperidinium cretaceum: [Pocock 1962, p. 80]:
Diagnosis:
Theca longer than it is broad, ellipsoidal; epitheca long, conical tapering to a point and may or may not be surmounted by a solid apical horn; equatorial girdle well developed, helicoid; hypotheca more or less dome shaped, terminated by two hypothecal spines, one always being longer than the other. Thecal wall thin and transparent, pale yellow or colourless, with no visible system of plates; theca is either scabrate or finely granulose and, in well preserved specimens, usually contains yellow green rounded crystalline bodies; spherical cysts have been observed with the theca of some specimens.
Dimensions:
Range: Length: 81-95 µm; Breadth: 50-69 µm; Length of longer hypothecal spine: 12-25 µm; Length of shorter hypothecal spine: 4-10 µm.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended descriptions:
Davey, 1970, p.359-360:
Diagnosis:
Shell pentagonal; epitract triangular, with broadly conical apical horn; hypotract bearing two conical antapical horns of unequal length. Outer membranes thin, enclosing inner body of similar shape.
Cingulum marked by low ridges.
Weak tabulation sometimes developed, marked by low thickenings of periphragm.
Outline of anterior intercalary plate 2a usually present, but in plate typically in place.
Dimensions:
Range: Overall length: 86-118 µm; Overall width: 57-82 µm. Number of specimens measured: 8.
---------------------------------------
Davey, 1970, p.360:
Description:
The apical and two antapical horns are well developed, the latter differing in size from one another. The outer membrane is extremely thin, wrinkled and often possess slight thickenings which occasionally bear small pointed spines. These thickenings partially outline a tabulation which resembles the Peridinium-type tabulation described by Manum (1963). The cingulum is bordered by two low ridges and is only slightly laevo-rotatory. An archaeopyle has never been observed but the outline of paraplate 2a is usually present.