Columella

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Fig. 1. Columellas. Transmitted light micrographs. A-D: Kurnubia palastiniensis Henson. Upper Jurassic, Northeastern Morocco. A: transverse section near and almost parallel to the axis of coiling; B: axial section; C-D: oblique sections. Position of sections relative to the axial section marked by red lines. E: Borelis schlumbergeri (Reichel), axial section. Gulf of Aqaba. Recent. Note double columella in planispiral-fusiform shells. b: beam; bl: basal layer; col: columella; f: foramina; prp: preseptal passage; r: rafter; s: septum; sl: septulum; t: tunnel; wsut: whorl suture; (Hottinger, 2006; fig. 32 [1] CC/BY-NC-SA)


Definition

  • according to Hottinger (2006):

COLUMELLA - the solid, trochospiral structure formed by the basal walls of spiral chambers coalescing around the coiling axis, as in many gastropod shells, or symmetrically poleward in planispiral - fusiform shells. May be thickened by secondary deposits or by an extensive thickening of a basal layer in the polar realm of the shell (alveolinids).


References

Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744

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