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Tenua microrobusta

Tenua microrobusta Morgan 1980

Originally Tenua Eisenack, 1958, subsequently Sentusidinium.
Taxonomic senior synonym: Tenua (as Batiacasphaera, now Pilosidinium) aptiensis, according to Backhouse (1988, p.107).

Holotype: Morgan, 1980, pl.29, figs.15-16
Locus typicus: Yantabulla, Australia
Stratum typicum: Late Neocomian-late Aptian

Original description: Morgan, 1980, p. 33
Cyst subspherical with a 1.0-1.5 µm thick rigid endophragm and a thin periphragm drawn up into very many stout (3-4 µm long and 1 µm diameter), hollow, strongly capitate spines: spines non-tabular; archeopyle apical, operculum free or attached; accessory archeopyle sutures indicate six precingular plates.

Affinities:
Morgan, 1980, p. 33: T. microrobusta differs from the strongly ellipsoidal species T. pilosa (Ehrenberg 1843) Sarjeant 1968 and T. capitata (Cookson and Eisenack 1960) Gitmez and Sarjeant 1972. The most similar subcircular Tenua species is T. villersense Sarjeant 1968, which has a dense, even cover of short capitate spines, and may be a senior synonym if interpreted broadly. The Australian specimens described here differ from T. villersense and all other subcircular Tenua species by having fewer more robust spines, and a thicker wall.
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