Difference between revisions of "Beam"
(Created page with "thumb|<font size="2"> '''Fig. 1.''' The structure of ''Orbitopsella'': a simple [[exoskeleton and a pillared endoskeleton in a discoidal shell: ''Orbit...") |
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[[File:Fig 45.jpg|thumb|<font size="2">'''Fig. 2.''' Alveolar exoskeleton and polygonal network. | [[File:Fig 45.jpg|thumb|<font size="2">'''Fig. 2.''' Alveolar exoskeleton and polygonal network. | ||
'''A-C:''' simple alveolar layer in ''Everticyclammina virguliana'' (Koechlin), Mechra Klila, Northeastern Morocco, Uppermost Jurassic. '''A:''' stereograph, schematic, not to scale. '''B:''' tangential section. Note the large size of the alveoles in a postseptal position. '''C:''' para-equatorial, non-centered section showing septa and the basal coat at the bottom of the chamber, resembling a basal layer. '''E-G:''' polygonal network in ''Spirocyclinidae''. '''E:''' ''Choffatella tingitana'' Hottinger, megalospheric generation, in tangential section near to the equatorial plane. Note the clear differentiation of beams and rafters. '''D:''' stereograph of spirocyclinid polygonal network. Note the curved pigeon holes in preseptal position which in axial section might be mistaken for foramina. '''F-G:''' extension of beams into a corrugated sheet that replaces endoskeletal pillars in ''Hottingertidae''. '''F:''' stereograph representing a part of an axial section. Not to scale. '''G:''' ''Alveosepta powersi'' (Redmond), Northeastern Morocco, Upper Jurassic. Equatorial section of megalospheric specimen. | '''A-C:''' simple alveolar layer in ''Everticyclammina virguliana'' (Koechlin), Mechra Klila, Northeastern Morocco, Uppermost Jurassic. '''A:''' stereograph, schematic, not to scale. '''B:''' tangential section. Note the large size of the alveoles in a postseptal position. '''C:''' para-equatorial, non-centered section showing septa and the basal coat at the bottom of the chamber, resembling a basal layer. '''E-G:''' polygonal network in ''Spirocyclinidae''. '''E:''' ''Choffatella tingitana'' Hottinger, megalospheric generation, in tangential section near to the equatorial plane. Note the clear differentiation of beams and rafters. '''D:''' stereograph of spirocyclinid polygonal network. Note the curved pigeon holes in preseptal position which in axial section might be mistaken for foramina. '''F-G:''' extension of beams into a corrugated sheet that replaces endoskeletal pillars in ''Hottingertidae''. '''F:''' stereograph representing a part of an axial section. Not to scale. '''G:''' ''Alveosepta powersi'' (Redmond), Northeastern Morocco, Upper Jurassic. Equatorial section of megalospheric specimen. | ||
| − | '''alv:''' alveoles; '''b:''' [[beam]]; '''bl:''' [[basal layer]]; '''corr:''' corrugated median extension of beams; '''f:''' [[foramen]]; '''ph:''' pigeon holes; '''s:''' [[septum]]; '''sf:''' supplementary foramina; '''sph:''' [[sphaeroconch]]; '''ssut:''' [[septal suture]]. Arrows: direction of growth. After Hottinger, 1967.; (Hottinger, 2006; fig. 45 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]] | + | '''alv:''' alveoles; '''b:''' [[beam]]; '''bl:''' [[basal layer]]; '''corr:''' corrugated median extension of beams; '''f:''' [[foramen]]; '''ph:''' pigeon holes; '''s:''' [[septum]]; '''sf:''' supplementary foramina; '''sph:''' [[sphaeroconch]]; '''ssut:''' [[septal suture]]. '''Arrows:''' direction of growth. After Hottinger, 1967.; (Hottinger, 2006; fig. 45 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]] |
[[File:Fig 19.gif|thumb|<font size="2">'''Fig. 3.''' Henson's "subepidermal partitions" (1948, text-figs. 6-7). | [[File:Fig 19.gif|thumb|<font size="2">'''Fig. 3.''' Henson's "subepidermal partitions" (1948, text-figs. 6-7). | ||
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==Definition== | ==Definition== | ||
*''according to Hottinger (2006):'' | *''according to Hottinger (2006):'' | ||
| − | '''BEAM''' - an [[exoskeletal]] main partition of the chamber lumen, perpendicular to the chamber septum and to the lateral chamber wall. In discoidal shells often separated from an [[endoskeleton]] by an empty space in the chamber ([[annular passage]]). May fuse with endoskeletal elements such as [[septula]], particularly in verbeekinids, orbitolinids and cuneolinids. May occur as unique exoskeletal element (Orbitopsella, Fig. 1 ) or in combination with minor, shorter exoskeletal elements producing a subepidermal polygonal network (Spirocyclinidae, Fig. 2 ). | + | '''BEAM''' - an [[exoskeletal]] main partition of the chamber lumen, perpendicular to the chamber septum and to the lateral chamber wall. In discoidal shells often separated from an [[endoskeleton]] by an empty space in the chamber ([[annular passage]]). May fuse with endoskeletal elements such as [[septula]], particularly in verbeekinids, orbitolinids and cuneolinids. May occur as unique exoskeletal element (Orbitopsella, Fig. 1.) or in combination with minor, shorter exoskeletal elements producing a subepidermal polygonal network (Spirocyclinidae, Fig. 2.). |
| − | ''Remarks:'' Davies (1930) distinguished "primary" or "major" (1939) partitions in the description of orbitolinids in opposition to "secondary" or "minor" elements. Henson (1948) separated "subepidermal plates" from main partitions (the latter being of endoskeletal nature and therefore to be called septula nowadays; compare Henson's fig. 7, reproduced here as Fig. 3 . Henson's (1948) subepidermal plates, synonymous with Silvestri's "trabecole perpendicolari" (1932), were subdivided again into "transverse" and "parallel" partitions corresponding to Davies' major and minor elements. Henson's general term "subepidermal partition" may include main partitions (= [[septula]]), transverse partitions (= [[beams]]) and parallel partitions (= [[rafters]]), where septula and beams fuse to produce (mostly radial) chamber compartments. In order to distinguish partitions according to their origin, Hottinger (1967) introduced particular terms for partitions exclusively of exoskeletal origin, i.e. "poutre" for major and "poutrelle" for minor partitions, translated into English in 1978 as "beam" and "rafter" (Balken and Bälkchen in German). For illustration see [[exoskeleton]]. | + | ''Remarks:'' Davies (1930) distinguished "primary" or "major" (1939) partitions in the description of orbitolinids in opposition to "secondary" or "minor" elements. Henson (1948) separated "subepidermal plates" from main partitions (the latter being of endoskeletal nature and therefore to be called septula nowadays; compare Henson's fig. 7, reproduced here as Fig. 3. Henson's (1948) subepidermal plates, synonymous with Silvestri's "trabecole perpendicolari" (1932), were subdivided again into "transverse" and "parallel" partitions corresponding to Davies' major and minor elements. Henson's general term "subepidermal partition" may include main partitions (= [[septula]]), transverse partitions (= [[beams]]) and parallel partitions (= [[rafters]]), where septula and beams fuse to produce (mostly radial) chamber compartments. In order to distinguish partitions according to their origin, Hottinger (1967) introduced particular terms for partitions exclusively of exoskeletal origin, i.e. "poutre" for major and "poutrelle" for minor partitions, translated into English in 1978 as "beam" and "rafter" (Balken and Bälkchen in German). For illustration see [[exoskeleton]]. |
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* [[septula]] | * [[septula]] | ||
==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 | + | Davies (1930), The genus Dictyoconus and its allies: a review of the group, together with a description of three new species from the lower Eocene beds of northern Baluchistan, Transactions of the Royal Society of Edinburgh, vol. 56, p. 485-505. |
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| + | Davies (1939), An early Dictyoconus and the genus Orbitolina: their contemporaneity, structural distinction and respective natural allies, Transactions of the Royal Society of Edinburgh, vol. 59, p. 773-790. | ||
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| + | Henson(1948), Larger imperforate Foraminifera of south-western Asia, Families Lituolidae, Orbitolinidae and Meandrosipinidae, British Museum (Natural History), London, 127 p. + 16 pls. | ||
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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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| + | Silvestri (1932), Foraminiferi del Cretaceo della Somalia, Paleontographica Italica, Pisa, vol. XXXII (1931, Nuova Serie, vol. II), p. 143-204. | ||
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