Difference between revisions of "Beam"
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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]]. |
