Residual pillar

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Fig. 1. Trematophores. A: stereograph of the trematophore of Lacazinella supported by a single residual pillar in axial position. Schema, not to scale. B-F: Lacazinella wichmanni (Schlumberger) from the Vogelkop, New Guinea. Middle-Upper Eocene. Transmitted light micrographs. All specimens are megalospheric. B: sections tangential to a septal face. C: a section perpendicular to the apertural axis reveals the concentric growth of the chambers from their beginning. D: section in the apertural axis. Note the alternation of the trematophore on opposite poles of the shell in successive chambers. E: oblique section cutting the apertural axis in a pillar supporting the trematophore. F: oblique section not cutting the apertural axis within the shell. Note the interruption of the septula below the equatorial roof of the chambers; a: aperture; af: apertural face; apax: apertural axis; bl: basal layer; f: foramen; pi: pillar; psp: preseptal space; s: septum by transformation of the outer chamber wall that is totally covered by a new concentric chamber; sf: septal face; sl: septulum; (Hottinger, 2006; fig. 82)[1] CC/BY-NC-SA)
Fig. 2 Odd association and polar structures in Praealveolina tenuis Reichel.From Alcantara, Lisbon; Cenomanian. Transmitted light micrographs; G: model of two subsequent chambers near their polar ends where the first floors in the basement appear; a: aperture: af: apertural face; bl: basal layer; chl: (main) chamberlets; fl: floor; prp: preseptal passage; rp: (incipient) residual pillar; s: septum; sa: supplementary aperture; sh: shaft; sl: septulum; sut: cameral suture; Hottinger, 2006; fig. 70)[2] CC/BY-NC-SA)


Definition

  • according to Hottinger (2006):

RESIDUAL PILLAR - an endoskeletal pillar supporting a frontal wall that spans a large preseptal space, frequent in trematophores. Where septula and floors are interrupted by a preseptal space, residual pillars may remain between (horizontal) preseptal passages and (vertical) shafts in support of the frontal chamber wall, as in elongate Praealveolina.




See also


References

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

Reichel (1933), Sur une alvéoline cénomanienne du Bassin du Beausset, Eclogae geologicae Helvetiae, Basel, vol. 26, N° 2, p. 269-280.

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