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Antarctissa (?) robusta Petrushevskaya, 1975

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Thick-walled nearly cylindrical shell. Cephalis and thorax nearly equal. Pores are few, axobat is well developed. Mouth closed by flat plate, very similar to A. denticulata. Different from A. denticulata in smaller dimensions and in cylindrical (not triangular or pyramidal) shell oitline. Different from A. cylindrica in surface smoothness and in shell mouth. The name means solid, hard, robust. The description is based on 28 specimens from Site 278 (Core 12 and some others). Holotype No. 63636 in the Marine Department.
The species is typical for the late Miocene in the Antarctic, but in upper Oligocene deposits (Sample 278-31-3, 40cm) some specimens with the same cephalis and thorax were found.They differ by the presence of abdomen the same size as the thorax seperated by inner septa. It is possible that two-segmented A. (?) robusta descended from three-segmented ancestors.
Petrushevskaya 1975











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