Alveole

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Fig. 1. Alveoles. A-D: model (schematic, not to scale) of the genus Malatyna Sirel, subaxial, subequatorial and tangential sections. Igualada, North-Eastern Spain. Uppermost Middle Eocene. E-F: Globoreticulina iranica Rahaghi, tangential and axial sections. Shiraz, Iran. Middle-Upper Eocene. G-H: Bullalveolina bulloides Reichel, axial and subequatorial sections. Peribetics, South-Eastern Spain. Lower Oligocene. I: Austrotrillina striata Adams, sections perpendicular to apertural axis and tangential sections. Kirkuk, Iraq. Oligocene. J-K: Everticyclammina virguliana (Koechlin), equatorial sections. Mechra Klila, North-Eastern Morocco, Uppermost Jurassic. All sections transmitted light micrographs. a: (main) aperture; al: alveole; bl: basal layer; f: (main) foramen; pr: proloculus; prp: preseptal passage (in these cases extending over most of the chamber lumen); s: septum; sa: supplementary aperture; sl: septular ridges (incomplete septula); (Hottinger, 2006; fig. 9 [1] CC/BY-NC-SA)

Definition

  • according to Hottinger (2006):

ALVEOLE (alveolus, pl. alveoli) - a recess of varying depth in lateral walls, coated by the organic lining, blindly ending with a rounded contour below an epiderm or some equivalent outer layer of the wall and opening into the chamber lumen. May branch towards the outer part of the wall, each generation of branches forming layers within the wall.


Remarks: The term alveole is used here exclusively for exoskeletal structures, i.e. for subepidermal, tiny compartments of the chamber cavity coated by an organic lining. Alveoles are supposedly filled with chamber plasm. Alveoles must be distinguished from paraporous or parakeriothecal cavities that are an adjunct of wall texture. Like true pores, these cavities are (by definititon) neither filled with living chamber plasm nor coated by the organic lining. The simultaneous presence of both alveolar structures and keriothecal wall texture in the fusulinid Verbeekina and its relatives, the combination of an alveolar exoskeleton with a paraporous external wall in Dicyclina or with a bilamellar perforate wall in Fabiania supports a consequent restriction of the term's use to exoskeletal structures, never to textures. Layers of alveoles coating the lateral chamber wall are present in various agglutinated groups of which Cyclammina is the most prominent while Everticyclammina is an early extinct representative of an exoskeletal layer of exclusively undivided, shallow alveoles. The Neogene group of Textulariella Cushman (Grönhagen & Luterbacher, 1966) has branching alveoles. Among the porcelaneous foraminifera with alveoles, Austrotrillina is a prominent group. In this genus, species with deep and branching alveoles - A. howchini (Schlumberger) - are said to evolve from earlier forms with layers of shallow, undivided alveoles (Adams, 1968). The term alveole is also used for rows of blind recesses in postseptal position over supplementary apertures in the previous septal face as in Subalveolina or Bullalveolina. We do not yet know, how to interpret (in terms of exo- or endoskeletal elements) these alveoles nor what might be their biological meaning.


See also

References

Adams (1968), A revision of the foraminiferal genus Austrotrillina PARR.- Bulletin of the British Museum (Natural History), London, (Geology series), vol. 16, N° 2, p. 71-97.

Grönhagen & Luterbacher (1966), Beobachtungen an den Foraminiferen-Gattungen Pseudotextulariella und Textulariella sowie verwandten Formen. Eclogae geologicae Helvetiae, Basel, vol. 59, N° 1, p. 235-246.

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

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