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Achomosphaera triangulata
Williams, Lentin and Fensome 1998 - Lentin and Williams Index of Fossil Dinoflagellates
[Achomosphaera triangulata, (Gerlach, 1961, p. 194-195, pl.29, fig.1), Davey and Williams, 1969, p.4; Emendation: Sarjeant, 1984b, p.82-83
Originally Baltisphaeridium, subsequently (and now) Achomosphaera.
Holotype: Gerlach, 1961, pl.29, fig.1; Sarjeant, 1984b, pl.1, figs.4-5]
Locus typicus: Emsbüren, NW Germany
Stratum typicum: Middle Miocene
Age: mid Oligocene-mid Miocene
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Original description as Baltisphaeridium triangulatum: [Gerlach, 1961, p. 194] (Translation: Sarjeant, 1984):
Diagnosis:
Theca in outline oval to circular. Processes numerous, massive, divided into three branches, which bear at their ends two hooklets. Processes two-and three-rooted [lit. "footed"]. Pylome trapezoidal. Membrane granulate.
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Emended description:
Sarjeant, 1984, p. 82:
Diagnosis:
Proximochorate, spiniferate cysts, hercotabulate. Ambitus ovoidal, with epitract somewhat larger than hypotract. Epitract in the form of a broad hemiellipsoid, hypotract almost hemispheroidal. Processes gonal and intergonal in situation, varying in length according to position on the cyst from about 25% to 28% of the cyst breadth, sometimes appearing longer because of distortions in the orientation of their branches. Gonal processes slender, arising from broad bases but of very constant thickness between the base and the position of branching; trifurcate, their branches long and directed almost parallel (or at only a low angle) to the phragma surface, with bifid terminations, the branchlets typically recurved. Intergonal processes present in situations corresponding to the sutures between precingular and between postcingular plates; slimmer than the gonal processes and bifurcate, with extremely slender branches that may be simple or bifid. Paratabulation not directly indicated. Surface of phragma coarsely granulate to shagreenate or verrucate.
Archaeopyle single-plate precingular (type P), formed by loss of a portion of the cyst wall corresponding to plate 3". Operculum shield-shaped, free or attached.
Dimensions:
Holotype: length of central body 58 µm, breadth 53 µm, length of processes c. 12-15 µm.
Paratype A: length of central body 60 µm, breadth 48 µm, length of processes c. 12-14 µm.
Paratype B: length of central body 53 µm, breadth 42 µm, length of processes c.9-11 µm.
Range of dimensions: length of central body 36-60 µm (mean 53 µm), breadth 33-48 µm (mean 44 µm).
12 specimens measured (material 36 specimens).
[Achomosphaera triangulata, (Gerlach, 1961, p. 194-195, pl.29, fig.1), Davey and Williams, 1969, p.4; Emendation: Sarjeant, 1984b, p.82-83
Originally Baltisphaeridium, subsequently (and now) Achomosphaera.
Holotype: Gerlach, 1961, pl.29, fig.1; Sarjeant, 1984b, pl.1, figs.4-5]
Locus typicus: Emsbüren, NW Germany
Stratum typicum: Middle Miocene
Age: mid Oligocene-mid Miocene
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Baltisphaeridium triangulatum: [Gerlach, 1961, p. 194] (Translation: Sarjeant, 1984):
Diagnosis:
Theca in outline oval to circular. Processes numerous, massive, divided into three branches, which bear at their ends two hooklets. Processes two-and three-rooted [lit. "footed"]. Pylome trapezoidal. Membrane granulate.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Emended description:
Sarjeant, 1984, p. 82:
Diagnosis:
Proximochorate, spiniferate cysts, hercotabulate. Ambitus ovoidal, with epitract somewhat larger than hypotract. Epitract in the form of a broad hemiellipsoid, hypotract almost hemispheroidal. Processes gonal and intergonal in situation, varying in length according to position on the cyst from about 25% to 28% of the cyst breadth, sometimes appearing longer because of distortions in the orientation of their branches. Gonal processes slender, arising from broad bases but of very constant thickness between the base and the position of branching; trifurcate, their branches long and directed almost parallel (or at only a low angle) to the phragma surface, with bifid terminations, the branchlets typically recurved. Intergonal processes present in situations corresponding to the sutures between precingular and between postcingular plates; slimmer than the gonal processes and bifurcate, with extremely slender branches that may be simple or bifid. Paratabulation not directly indicated. Surface of phragma coarsely granulate to shagreenate or verrucate.
Archaeopyle single-plate precingular (type P), formed by loss of a portion of the cyst wall corresponding to plate 3". Operculum shield-shaped, free or attached.
Dimensions:
Holotype: length of central body 58 µm, breadth 53 µm, length of processes c. 12-15 µm.
Paratype A: length of central body 60 µm, breadth 48 µm, length of processes c. 12-14 µm.
Paratype B: length of central body 53 µm, breadth 42 µm, length of processes c.9-11 µm.
Range of dimensions: length of central body 36-60 µm (mean 53 µm), breadth 33-48 µm (mean 44 µm).
12 specimens measured (material 36 specimens).