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Antarctissa cylindrica Petrushevskaya, 1975

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Surface nearly spongy (in A. clausa the walls are very thick but the surface nearly smooth). The rounded outline is nearly the same as in A. clausa. The additional lobes are very distinct. It is difficult to formulate the characters of this species but it is very abundant in the Antarctic Pliocene. It might have originated from late Miocene A. capitata (Popofsky) group.The description is based on 67 specimens. Holotype No. 63122 in the Marine Department.
Petrushevskaya 1975
Distinguished by the presence of an internal ring with more than 6 (typically 8 or more) radial connecting bars to the thorax lattice-wall, and by the short, cylindrical thorax. Because the internal structure is difficult to see, identification usually is based on overall shell shape. Specimens with short thoraxes (Pl. 3, Figs. 9, 11) dominate later Plio­cene populations and are easy to identify, but earlier Pliocene popula­tions contain many individuals with longer thoraxes. These specimens are difficult to reliably distinguish from coeval specimens of Antarctissa denticulata (Ehrenberg) Petrushevskaya 1968, which, in the early part of its range, has a similar shell shape. Weaver (1976a) incorrectly gives A. denticulata sensu Chen (1975a) as the equivalent to A. cylindrica. As Chen noted in his thesis (1975b), the correct equivalence is between A. cylindrica Petrushevskaya, 1975 and A. ewingi Chen, 1975a, since the holotype specimen of A. cylindrica (Petrushevskaya, 1975, pl. 11, fig. 19) is clearly equal to Chen's A. ewingi. Petrushevskaya's description of A. cylindrica however does not make any mention of the distinctive in­ternal structure of this species.
Lazarus 1990


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