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Antarctissa deflandrei (Petrushevskaya, 1975)

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Antarctissa conradae
Cephalis thick-walled, ovate, with scatteres, small, subcircular pores. Specimens from younger sediments have conical spines on the apex of the cephalis, and cephalis pores become progressiveley larger and more irregular during the evolutionary changes of the species.
Thorax cylindrical, slightly tapering at base in some specimens, seperated from the cephalis by a distinct collar constriction. Thoracic pores circular to subcircular, scattered and about the same size as those of the cephalis. In specimens from younger sediments, the dorsal and two lateral spines constrict the wall of the thorax and form longitudinal furrows, and thoracic pores become larger and more abundant.
Based on 35 specimens from 266-11, CC; 266.10, CC; and 267B, CC. Length of cephalis 27-36 µ, width of thorax 35-54 µ.
This species evolved into Antarctissica longa (Popofsky) in the Lower Pliocene. The distinction between these two species is made by an arbitrary size limit of the thorax; i. e., specimens haing a thorax less than 54 µ in width will be assigned to Antarctissica conradae, other specimens to A. longa. A. conradae is named after the research vessel Robert D. Conrad.
Chen 1975
Botryopera deflandrei
The ratio of the breadths of the eucephalic lobe and the thorax is about 1:1.5, the same as in B. triloba, gr. The shell dimensions and the pore arrangement are also nearly the same. The walls are thicker and smooth. The whole skeleton is less variable. The distinguishing characteristic is the outline of the upper part of the eucephalic lobe: it is elongated into a peak. This formation is known for Trisulcus sp. and for T. boldyrae (Petrushevskaya, 1971b, pi. 46, fig. 6-11). B. deflandrei is very similar to these two species, especially to the tropical Oligocene Trisulcus sp. (but B. deflandrei is larger). This apical peak is un- connected with the apical spine A, but it is possible that it represents the rudiment of the central position of the spine A (known in Lithomelissa where the spine A forms columella in the eucephalic lobe, and forms apical horn on the top of the shell, Petrushevskaya, 1971b, pl. 44, 45).
Antarctic Miocene.
The description is based on 26 specimens from Site 278 (Cores 14- 20). Holotype No. 63119 in the Marine Department. Species is named after the reknowned micropaleontologist George Deflandre.
Petrushevskaya 1975











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