Back
Ambonosphaera jurassica
Ambonosphaera jurassica, (Gitmez and Sarjeant, 1972), Fensome, 1979; Emendation: Poulsen and Riding, 1992, p.28, as Senoniasphaera jurassica.
NOW Senoniasphaera. Originally Hexagonifera, subsequently (and now) Senoniasphaera, thirdly Ambonosphaera. Taxonomic senior synonym: Meiourogonyaulax (now Lithodinia?) staffinensis, according to Williams et al. (1993, p.32) - however, in the same publication, Williams et al. (1993, p.56) retained Hexagonifera (now Senoniasphaera) jurassica.
Holotype: Gitmez and Sarjeant, 1972, pl.14, fig.5
Locus typicus: H. M. Geol. Surv. Borehole, Warlingham, England
Stratum typicum: Middle Kimmeridgian
Age: Kimmeridgian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Hexagonifera jurassica: [Gitmez and Sarjeant, 1972, p. 240]:
Diagnosis:
A species of Hexagonifera with broadly ovoidal to elongate cyst. The periblast has a blunt, hollow apical projection formed by the periphragm only. The surface of the periblast is delicate, smooth or minutely granular- the endoblast, in contrast, is thick-walled and densely granular, with occasional tubercles. A circular cingulum divides the periblast almost equally, sometimes the epitract is slightly smaller than the hypotract.
There is no definite indication of tabulation or of a sulcus.
An apical archaeopyle is typically developed.
Description:
The subspherical to ovoidal endoblast is completely enclosed by the delicate periblast. The epitract of the periblast is conical, with no apical projection superimposed on the cone shape. The epitract of the endoblast is rounded and dome-shaped. The antapex of both periblast and endoblast is rounded. A polygonal apical archaeopyle is usually present; generally the operculum remains attached to the shell. The tabulation is generally indeterminable, but the dorsal tabulation could be distinguished with difficulty on some specimens two apical, three precingular, three postcingular and one antapical plates were recognized.
Dimensions:
Holotype: overall length 85 µm, breadth 72 µm, endoblast length 73 µm, breadth 66 µm.
NOW Senoniasphaera. Originally Hexagonifera, subsequently (and now) Senoniasphaera, thirdly Ambonosphaera. Taxonomic senior synonym: Meiourogonyaulax (now Lithodinia?) staffinensis, according to Williams et al. (1993, p.32) - however, in the same publication, Williams et al. (1993, p.56) retained Hexagonifera (now Senoniasphaera) jurassica.
Holotype: Gitmez and Sarjeant, 1972, pl.14, fig.5
Locus typicus: H. M. Geol. Surv. Borehole, Warlingham, England
Stratum typicum: Middle Kimmeridgian
Age: Kimmeridgian.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Original description as Hexagonifera jurassica: [Gitmez and Sarjeant, 1972, p. 240]:
Diagnosis:
A species of Hexagonifera with broadly ovoidal to elongate cyst. The periblast has a blunt, hollow apical projection formed by the periphragm only. The surface of the periblast is delicate, smooth or minutely granular- the endoblast, in contrast, is thick-walled and densely granular, with occasional tubercles. A circular cingulum divides the periblast almost equally, sometimes the epitract is slightly smaller than the hypotract.
There is no definite indication of tabulation or of a sulcus.
An apical archaeopyle is typically developed.
Description:
The subspherical to ovoidal endoblast is completely enclosed by the delicate periblast. The epitract of the periblast is conical, with no apical projection superimposed on the cone shape. The epitract of the endoblast is rounded and dome-shaped. The antapex of both periblast and endoblast is rounded. A polygonal apical archaeopyle is usually present; generally the operculum remains attached to the shell. The tabulation is generally indeterminable, but the dorsal tabulation could be distinguished with difficulty on some specimens two apical, three precingular, three postcingular and one antapical plates were recognized.
Dimensions:
Holotype: overall length 85 µm, breadth 72 µm, endoblast length 73 µm, breadth 66 µm.