Difference between revisions of "Endoskeleton"
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==Definition== | ==Definition== | ||
*''according to Hottinger (2006):'' | *''according to Hottinger (2006):'' | ||
| − | '''ENDOSKELETON''' - localized thickenings on the inner surface of the chamber wall that partly or totally subdivide the main chamber lumen in the lee of protoplasmic streams according to a pattern produced by the arrangement of intercameral foramina in successive septa. Plate-like elements ([[septula]]), usually perpendicular to the septum, may form more or less complete partitions touching the lateral walls or fusing with elements of the [[exoskeleton]]. Discontinuous, columnar partitions are called [[pillars]] (or interseptal pillars). A third type of endoskeleton is produced by layers of shell deposited on the chamber floor and coating the previously exposed outer shell surface completely ([[basal layer]]) or partially ([[chomata]] and [[parachomata]] of fusulinids). In different taxa, the three endoskeletal types may occur alone or in varying combinations | + | '''ENDOSKELETON''' - localized thickenings on the inner surface of the chamber wall that partly or totally subdivide the main chamber lumen in the lee of protoplasmic streams according to a pattern produced by the arrangement of intercameral foramina in successive septa. Plate-like elements ([[septula]]), usually perpendicular to the septum, may form more or less complete partitions touching the lateral walls or fusing with elements of the [[exoskeleton]]. Discontinuous, columnar partitions are called [[pillars]] (or interseptal pillars). A third type of endoskeleton is produced by layers of shell deposited on the chamber floor and coating the previously exposed outer shell surface completely ([[basal layer]]) or partially ([[chomata]] and [[parachomata]] of fusulinids). In different taxa, the three endoskeletal types may occur alone or in varying combinations. Often, endoskeletal elements appear only in the course of ontogeny, usually later than exoskeletal elements. In agglutinated shells endoskeletal elements include the septum and may be recognized by remarkably coarse and irregularly shaped particles that obscure the genetically fixed pattern in contrast to the more ordered exoskeletal elements of the same specimen. Whether the toothplates and their equivalents in lamellar perforate foraminifera and the secondary septa produced by folds of the inner lamella in orthophragminid lamellar architecture are homologous equivalents of the endoskeletal structures of non-lamellar-imperforate foraminifera remains an open question. |
''Remarks:'' The term endoskeleton was introduced by H. Douvillé (1906, p. 593 and 602) in a key paper comparing the anatomy of imperforate fusiform shells, i.e. fusulinids, loftusiids and alveolinids. Douvillé had already recognized the close morphological relationship between apertural and endoskeletal patterns. In his monograph on alveolinids, M. Reichel (1936-1937) adopted the term endoskeleton to designate the structural elements subdividing the chamber in contrast to a so-called exoskeleton comprising the lateral and frontal chamber walls including the apertural face. The strict correspondence between the pattern of distribution of the foramina on the septal face and the patterns produced by the endoskeletal elements (in the alveolinids by the septula) were clearly demonstrated by models of the shell cavities and their connections through the septum as if they were a cast of the shell cavities (Reichel, 1936-1937, fig. 27). These patterns are still used today as diagnostic features for the definition of alveolinid genera. | ''Remarks:'' The term endoskeleton was introduced by H. Douvillé (1906, p. 593 and 602) in a key paper comparing the anatomy of imperforate fusiform shells, i.e. fusulinids, loftusiids and alveolinids. Douvillé had already recognized the close morphological relationship between apertural and endoskeletal patterns. In his monograph on alveolinids, M. Reichel (1936-1937) adopted the term endoskeleton to designate the structural elements subdividing the chamber in contrast to a so-called exoskeleton comprising the lateral and frontal chamber walls including the apertural face. The strict correspondence between the pattern of distribution of the foramina on the septal face and the patterns produced by the endoskeletal elements (in the alveolinids by the septula) were clearly demonstrated by models of the shell cavities and their connections through the septum as if they were a cast of the shell cavities (Reichel, 1936-1937, fig. 27). These patterns are still used today as diagnostic features for the definition of alveolinid genera. | ||
Hottinger (1967) modified and extended (1978) Douvillé's term to include all structures subdividing the chamber lumen and linked to the patterns of intralocular protoplasmic streaming in contrast to exoskeletal partitions that are not affected by such patterns. Thus, the originally descriptive term is expanded to include a functional meaning and extended to all corresponding features in imperforate shells. In some lamellar-perforate foraminifera, comparatively rare structures (such as the hollow pillars in Chapmanina) correspond in shape and position to the definition of endoskeletal features. There is no reason to interpret their function otherwise. So such features may be called endoskeletal without hesitation. They may lead the way to clarify, by comparisons, the significance of true [[toothplate]] structures. | Hottinger (1967) modified and extended (1978) Douvillé's term to include all structures subdividing the chamber lumen and linked to the patterns of intralocular protoplasmic streaming in contrast to exoskeletal partitions that are not affected by such patterns. Thus, the originally descriptive term is expanded to include a functional meaning and extended to all corresponding features in imperforate shells. In some lamellar-perforate foraminifera, comparatively rare structures (such as the hollow pillars in Chapmanina) correspond in shape and position to the definition of endoskeletal features. There is no reason to interpret their function otherwise. So such features may be called endoskeletal without hesitation. They may lead the way to clarify, by comparisons, the significance of true [[toothplate]] structures. | ||
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==See also== | ==See also== | ||
| − | *[[ | + | *[[basal layer]] |
| + | *[[choma]] | ||
*[[exoskeleton]] | *[[exoskeleton]] | ||
*[[parachomata]] | *[[parachomata]] | ||
*[[pillars]] | *[[pillars]] | ||
*[[septula]] | *[[septula]] | ||
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==References== | ==References== | ||
| − | Hottinger (2006), [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Illustrated glossary of terms used in foraminiferal research]. [http://paleopolis.rediris.es/cg/uk-index.html Carnets de Géologie], [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Memoir 2], ISSN 1634-0744 | + | Douvillé(1906), Évolution et enchaînement des Foraminifères, Bulletin de la Société géologique de France, Paris, (4ème série), tome 6ème, p. 588-602 + pl. XVIII. |
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| + | Hottinger (1967), Foraminifères imperforés du Mésozoïque marocain, Notes et Mémoires du Service géologique, Rabat, N° 209, p. 5-168 | ||
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| + | Hottinger (1978), Comparative anatomy of elementary shell structures in selected larger Foraminifera. In: Hedley R.H. & Adams C.G. (eds.), Foraminifera. Volume 3, Academic Press, London, p. 203-266. | ||
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| + | Hottinger (2006), [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Illustrated glossary of terms used in foraminiferal research]. [http://paleopolis.rediris.es/cg/uk-index.html Carnets de Géologie], [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Memoir 2], ISSN 1634-0744 | ||
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| + | Reichel (1936-1937), Étude sur les Alvéolines.- Mémoires de la Société paléontologique Suisse, Bâle, vols. LVII & LIX, 147 p. + 11 pls. | ||
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