Fig. 1. Henson's "zonation" of discoidal chambers in uniserial-conical shells, namely the marginal, radial and reticulate zones. Compare Fig. 2 From Henson, 1948; (Hottinger, 2006; fig. 20) CC/BY-NC-SA)
Fig. 2. The structure of Orbitolina.A-D: Oblique and vertical views of the cone base. These plasticine models sculptured in the years around 1955 by M. Richel (* 1896 - † 1984) were never published. E-F: Details of a septulum in the radial zone of the discoidal chamber. In model E the septulum is cut below the roof and above the bottom of the chambers. The apparent folding of the section results from the adjustment of the endoskeletal structure to the crosswise-oblique arrangement of the stolon axes (arrows) that produce so-called ramps. In model F the septulum is cut in the middle of the chamber and shows a part of the chamber bottom with the face of the previous chamber. In the middle of the chamber, the section of the septulum appears unfolded. Compare Fig. 3 and Fig. 4 G-H: Random thinsections of Orbitolina sp. from Southwestern France, Albian. Transmitted light micrographs. In Fig. G the approximate positions of sections H-K are indicated. Note the inverse orientation: the sections face downward. G-K: Random sections of Orbitolina sp. from Southwestern France, Albian. Transmitted light micrographs. The approximate position of sections H-K are indicated in section G that is very close to the axial plane. For Henson's zonation of the chamber see Fig. 1. Section H demonstrates details of the reticular zone, section I details of the marginal zone and section J details of the radial zone. The transverse section K shows the ramps produced by the crosswise-oblique stolon system. a: aperture; af: apertural face; b: beam; cl: chamberlet; e: epiderm; f: foramen; gr: coarse grains in the septum that obscure the structural pattern; hor: horizontal section in the plasticine model; marg: marginal zone; r: rafter; ra: ramp; rad: radial zone; ret: reticular zone; s: septum; sf: septal face; sl: septulum; sut: suture of the chambers. Double arrows in E and F: crosswise oblique foraminal axes; (Hottinger, 2006; fig. 71) CC/BY-NC-SA)
Fig. 3. Endoskeletal patterns in discoidal shells (after Hottinger, 1967) H1-2: Orbitolites spp. from the region of Tremp, Lerida prov., Northern Spain. Pyrenean Lower Eocene (Ilerdian). H1: the comparatively regular disposition of the ramps in sections parallel to the equatorial plane reveals their superposition in consecutive stolon planes. H2: in the transverse section parallel to the axis of the shell this superposition is clearly visible where the section is tangential to an annular septum. Abbreviations:f: foramen; ra: ramp; s: septum; sl: septulum; (Hottinger, 2006; fig. 47  CC/BY-NC-SA)
Fig. 4. Stolon planes and foramenal axes in discoidal-annular and conical-uniserial shells. Schematic, not to scale. Arrangement of stolon axes on cone mantles in the so-called radial zone of the cone is in accordance with the four basic patterns that govern discoidal structures. In conical shells, however, the stolon planes are replaced by cone mantles. As the cone increases in radius during growth, new stolon axes are intercalated in the cone mantles (arrows). G: crosswise-oblique arrangement of stolon axes in line on a shell radius on subsequent cone mantles. This structure is a characteristic of Orbitolina; (Hottinger, 2006; fig. 80  CC/BY-NC-SA)
- according to Hottinger (2006):
CENTRAL COMPLEX - see reticular zone. Adaxial cone in conical agglutinated forms where radial septula are fused to an irregular pattern of meshes. In contrast to radial zone and marginal zone.
Henson (1948), Larger imperforate Foraminifera of south-western Asia, Families Lituolidae, Orbitolinidae and Meandrosipinidae, British Museum (Natural History), London, 127 p. + 16 pls.
Hottinger (1967), Foraminifères imperforés du Mésozoïque marocain, Notes et Mémoires du Service géologique, Rabat, N° 209, p. 5-168
Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744
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