View source for Corona

[[File:Fig 41.jpg|thumb|<font size="2">'''Fig. 1.''' Embryonic apparatus.
'''A:''' ''Discocyclina'', stereograph after Ferràndez (1999), modified. Schema, not to scale. '''B:''' ''Discocyclina sp.'', equatorial section, showing corona. Transmitted light micrograph. '''C:''' ''Amphisorus sp.'' Stereograph, schema, not to scale. '''D:''' ''Amphisorus hemprichii'' Ehrenberg from the Gulf of Aqaba, Red Sea. Recent. Equatorial section, transmitted light micrograph, showing flexostyle and forecourt. '''E:''' ''Orbitolites sp.'', stereograph after Lehmann, 1961, redrawn. Note the shape like a dumb-bell of the proloculus. '''F-G:''' ''Orbitolites sp.'', Lower Eocene, Pakistan, Allemann collection. Oblique-centered sections, in approximately equatorial and axial direction, showing flexostyle constricting the proloculus. Transmitted light micrographs. '''H:''' ''Orbitopsella sp.'', stereograph showing sphaeroconch with its exoskeleton. Schema, not to scale, after Hottinger, 1967. Note the appearance of endoskeletal pillars not before the third chamber. '''I:''' ''Orbitopsella praecursor'' (Gümbel), Middle Lias, Morocco, equatorial section showing the thin proloculus wall and the sphaeroconch with its simple exoskeleton consisting of beams only. Transmitted light micrograph. '''J:''' Advanced orbitoliniform embryo, schematic, not to scale. Note the apex that is directed downwards (arrows) to facilitate the comparison with Hofker's drawings (1963). '''K-L:''' embryos of ''Karsella hottingeri'' Sirel, a Upper Paleocene form that exhibits an architecture strikingly similar to the one of Mid-Cretaceous orbitolinids. Pakistan, Allemann collection. Transmitted light micrographs. '''M:''' ''Sabaudia minuta'' Hofker Jr, embryo followed by three agglutinated chambers of the same series and presenting a simple exoskeleton. Lower Cretaceous. Note the hyaline embryo wall. The embryos are known to be formed within the mother shell and seem to have no access to grains in the environment to build their agglutinated walls.
'''achl:''' auxilliary chamberlet; '''ap:''' [[annular passage]]; '''ast:''' annular stolon; '''b:''' [[beam]]; '''d:''' [[deuteroconch]]; '''ecr:''' [[equatorial crest]]; '''fl:''' [[flexostyle]]; '''il:''' [[inner lamella]]; '''lchl:''' [[lateral chamberlet]]; '''mchl:''' main chamberlets; '''ol:''' [[outer lamella]]: '''ost:''' oblique stolon; '''ost(d):''' oblique stolon of deuteroconch; '''p:''' [[pore]]; '''pap:''' papilla; '''peri:''' periembryonal chamberlets; '''pi:''' [[pillar]]; '''pr:''' [[proloculus]]; '''rst:''' radial stolon; '''rst(d):''' radial stolon of deuteroconch; '''s:''' [[septum]]; '''sc:''' [[sphaeroconch]]; '''sl:''' [[septulum]]; '''sub:''' subembryonic chamber (=deuteroconch); '''supra:''' [[supraembryonic chamber]]; (Hottinger, 2006; fig. 41 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]]
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==Definition==
*''according to Hottinger (2006):''
'''CORONA''' -  first cycle of chamberlets enveloping an embryonal apparatus completely, at least in one plane of sectionning, as in ''Discocyclina''. 


''Remarks'': The term may be useful in biometry when describing the relation between the diameter of the embryonic apparatus and the number of chamberlets in the immediately succeeding growth stage. See also: [[periembryonic chamberlets]].





==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                                                              
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