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Heslertonia teichophera
Heslertonia teichophera (Sarjeant, 1961a, p.107–108, pl.15, fig.9; text-figs.9a–b) Sarjeant, 1976c, p.8. Emendation: Below, 1990, p.42–43, as Arkellea teichophera
Now Arkellea. Originally Cymatiosphaera, subsequently Heslertonia, thirdly (and now) Arkellea.
Holotype: Sarjeant, 1961, pl.15, fig.9; text-figs.9a-b; Sarjeant, 1976, pl.6, fig.3
Age: Oxfordian
Original diagnosis: Sarjeant 1961, p. 107-108: Cymatiosphaera teichophera
Species of Cymatiosphaera having a broadly ellipsoidal shell divided into a low number (12-16) of polygonal fields. The membranes delimiting fields are high, their height equal to about one-third of the short diameter; they bear striations normal to the shell surfaces.
Original description: Sarjeant, 1961, p. 108: Cymatiosphaera teichophera
Shell walls of moderate thickness and of brownish-yellow colour. Fields vary considerably in size; their separating membranes are thin and relatively readily crumpled, lacking supporting spines at the junctions but having a distinct outer edge on to which striations do not extend. Dimensions: holotype: overall long diameter 50 µm. overall short diameter 40 µm, crests around 9 µm high.
Sarjeant 1971, p. 8: Compared to C. teichophera, four known species have crests of similar proportional height. All are very much smaller in size than C. teichophera, lack striations on their crests, and also differ as follows: Cymatiosphaera eupeplos Valensi, from the Middle Jurassic of France (1948), has membranes supported by spines at their junction. The other three comparable species have been described by Deunff from the Devonian of Canada. C. cornifera (1955) has fields with a short spine at their centre, C. cubus (1954) has a distinctly cubic outline and fewer fields. C. prismatica (1954) has a prismatic outline.
Now Arkellea. Originally Cymatiosphaera, subsequently Heslertonia, thirdly (and now) Arkellea.
Holotype: Sarjeant, 1961, pl.15, fig.9; text-figs.9a-b; Sarjeant, 1976, pl.6, fig.3
Age: Oxfordian
Original diagnosis: Sarjeant 1961, p. 107-108: Cymatiosphaera teichophera
Species of Cymatiosphaera having a broadly ellipsoidal shell divided into a low number (12-16) of polygonal fields. The membranes delimiting fields are high, their height equal to about one-third of the short diameter; they bear striations normal to the shell surfaces.
Original description: Sarjeant, 1961, p. 108: Cymatiosphaera teichophera
Shell walls of moderate thickness and of brownish-yellow colour. Fields vary considerably in size; their separating membranes are thin and relatively readily crumpled, lacking supporting spines at the junctions but having a distinct outer edge on to which striations do not extend. Dimensions: holotype: overall long diameter 50 µm. overall short diameter 40 µm, crests around 9 µm high.
Sarjeant 1971, p. 8: Compared to C. teichophera, four known species have crests of similar proportional height. All are very much smaller in size than C. teichophera, lack striations on their crests, and also differ as follows: Cymatiosphaera eupeplos Valensi, from the Middle Jurassic of France (1948), has membranes supported by spines at their junction. The other three comparable species have been described by Deunff from the Devonian of Canada. C. cornifera (1955) has fields with a short spine at their centre, C. cubus (1954) has a distinctly cubic outline and fewer fields. C. prismatica (1954) has a prismatic outline.