Difference between revisions of "Alveole"
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''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. | ''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'' | + | 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. |
