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[[File:Fig 14.jpg|thumb|<font size="2">'''Fig. 1.'''  Attics and floors in ''Alveolinella borneensis'' Tan Sin Hok, Molukkas, Miocene. Transmitted light micrographs. '''A:''' Transverse section. Position in respect to B: double arrow A. '''B:''' axial section.
'''at:''' attics; '''cl:''' [[chamberlets]]; '''f1:''' [[foramen]] (basal row): '''f2:''' foramen (second row); '''f3:''' supplementary foramina corresponding to the attics; '''flo:''' floors; '''s:''' [[septum]]; (Hottinger, 2006; fig. 14 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]]

[[File:Fig.70G-H.png|thumb|<font size="2">'''Fig. 2.''' Odd association and polar structures in ''Praealveolina tenuis'' Reichel. From Alcantara, Lisbon; Cenomanian. Transmitted light micrographs; '''G:''' model of two subsequent chambers near their polar ends where the first floors in the basement appear. '''H:''' model of the protoplasmic body filling the cavities in G. Both models schematic, not to scale, after Reichel, 1933; '''a:''' [[aperture]]: '''af:''' [[apertural face]]; '''bchl:''' basement chamberlets; '''bl:''' [[basal layer]]; '''chl:''' (main) [[chamberlets]]; '''fl:''' [[floor]]; '''prp:''' [[preseptal passage]]; '''rp:''' (incipient) residual pillar; '''s:''' [[septum]]; '''sa:''' [[supplementary aperture]]; '''sh:''' [[shaft]]; '''sl:''' [[septulum]]; '''sut:''' cameral suture; (Hottinger, 2006; fig. 70 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]]
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==Definition==
*''according to Hottinger (2006):''
'''FLOOR''' - (French: plancher; German: Boden); part of [[endoskeleton]]: wall parallel to basal layer separating superposed, regular [[chamberlet layers]] in alveolinids. 


''Remarks:'' Advances in the comparative anatomy of alveolinids and miliolids requires that superposed regular layers of chamberlets separated by floors (= planchers, Reichel, 1936-1937) as in ''Praealveolina'' or ''Alveolinella'' be distinguished from irregular, tubular, supplementary chamberlets present in a thickened basal layer as in ''Alveolina'' or ''Subalveolina''. Both regular supplementary chamberlets and irregular, tubular chamberlets appear as soon as the fusiform shell reaches a specific minimum elongation (Hottinger, 1962). In particular the irregular chamberlets of ''Alveolina'' appear during ontogeny, at first in very low numbers, in shells where the polar thickening of the basal layer has produced an elongation of 1.4 : 1 in axial length versus equatorial diameter. A relationship between elongation index and polar structure is observed also in the parallel phyletic lineages. However, the difference between regular supplementary chamberlets and irregular-tubular passages in the polar columella is as diagnostic as all other structural features.
When Hamaoui and Fourcade (1973) were revising the axially compressed relatives of the classical alveolinids, they described the basal layer pierced by tubular supplementary passages as "central thickening". Reichel (1984, fig. 3, p. 530) established the homology of the thickened basal layer in the polar area of ''Subalveolina'' with the "central thickening" of ''Rhapydionia''. ''Chubbina'' was described by Robinson (1968) as having tubular passages in a basal layer, while De Castro established (1990) ''Pseudochubbina'' as the taxon for a compressed alveolinid "with floors". In published illustrations, the ''Chubbina'' endoskeleton rather resembles that of an advanced ''Praealveolina'' with floors while ''Pseudochubbina'' has, particularly in adult growth stages, very irregular tubular passages in a massive basal layer. Thus, the unfortunate current use of the term floor is synonymous with basal layer. A detailed structural analysis of laterally compressed alveolinids (Fleury & Fourcade, 1990) will be necessary to distinguish precisely the two kinds of endoskeleton.



















==References==
De Castro (1990), Osservazioni paleontologiche sul Cretacio della località-tipo di ''Raadshovenia salentina'' e su ''Pseudochubbina'' n. gen.- Quaderni dell' accademia pontaniana, Napoli, N° 10, 116 p. + 41 pls.

Fleury & Fourcade (1990), La superfamille Alveolinacea (Foraminifères): Systématique et essai d'interprétation phylogénétique, Revue de Micropaléontologie, Paris, vol. 33, N° 3-4, p. 241-268.

Hamaoui & Fourcade (1973), Révision des Rhapydionininae (Alveolinidae, Foraminifères), Bulletin du Centre de Recherche Pau- SNPA, vol. 7, N° 2, p. 361-435.

Hottinger (1962), Recherches sur les Alvéolines du Paléocène et de l'Éocène, Schweizerische Paläontologische Abhandlungen, Basel, N° 75/76, 243 p. + 18 pls.

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   

Reichel (1933),Sur une alvéoline cénomanienne du Bassin du Beausset, Eclogae geologicae Helvetiae, Basel, vol. 26, N° 2, p. 269-280.

Reichel (1936-1937), Étude sur les Alvéolines, Mémoires de la Société paléontologique Suisse, Bâle, vols. LVII & LIX, 147 p. + 11 pls.

Reichel (1984), Le crible apertural de Rhapydionina liburnica STACHE from the Vremski-Britof Maastrichtian, Yugoslavia. In: Benthos'83, 2nd International Symposium on Benthic Foraminifera (Pau, 1983), Bulletin des Centres de Recherches Exploration-Production Elf-Aquitaine, Pau, Mémoire 6, p. 525-532.

Robinson (1968), Some larger Foraminifera from the Eocene Limestones at Red Gal Ring, Jamaica, Verhandlungen Naturforschende Gesellschaft in Basel, vol. 84, N° 1, p. 281-292.




   
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