Umbilical plate

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Fig. 1. Alar prolongations and involuteness in lamellar foraminifers; A-B: Involuteness and evoluteness in lamellar foraminifers: an accurate definition is whether or not perforate walls (double arrow) cover the next whorl. Axial section, schematic, not to scale. Note the numerous, outer lamellas (green) enveloping the total exposed surface of the previous shell (compare "lamellation"). The distribution of the inner lamella (red) covering the previous whorl hasno significance in the definition of involuteness. Red: lumen of alar prolongation, yellow: lumen of equatorial chamber. alp: alar prolongation; il: inner lamella; mc: marginal cord; ol: (numerous) outer lamellas; p: pore; sulc: sulcus; (Hottinger, 2006; fig. 7; [1] CC/BY-NC-SA)
Fig. 2. Comparison of foraminiferal skeletons. Schematic, not to scale. Lamellation, perforation and canal orifices omitted. D: a spiral shell with a supplemental skeleton restricted to the periphery of the shell, as in nummulitids with a marginal cord; ch: chamber; lh: loophole; mc: marginal cord; pr: proloculus; s: septum; spc: spiral canal; spsut: spiral suture; sulc: sulcus; t: tunnel; up: umbilical plate; (Hottinger, 2006; fig. 63; [2] CC/BY-NC-SA)
Fig. 3. Fossette, parafossette, ponticulus and retral process in advanced elphidiids from the Gulf of Aqaba, Red Sea. Recent; H: axial section of megalospheric specimen. Transmitted light micrograph. Note the single row of foramina at the bottom of the chamber and the broad umbilical pile with its funnels; f: foramen; suc: spiral umbilical canal; vc: vertical canal (funnel); Scale bars: 0.1 mm, double scale bars: 0.05 mm.; (Hottinger, 2006; fig. 54; [3] CC/BY-NC-SA)


  • according to Hottinger (2006):

UMBILICAL PLATE (foramenal plate; umbilical flap; murus reflectus; toothplate; paries proximus, pars auct.) - a more or less contorted plate-like test element, extending between distal and proximal chamber walls and joined to both, attached to the intercameral foramen and to the main aperture, but not protruding into the latter. Separates the main chamber lumen from a primary umbilical-spiral canal. Between plate and adjacent coil or within the plate itself an opening provides connection between chamber and foliar chamberlet, wherever present.This opening may remain open in all chambers or it may be closed in all but the ultimate chamber by a sealing plate. An umbilical plate may be single or composed of two symmetrical branches in some planispiral genera, thereby producing one or two umbilical-spiral canals between plate and adjacent coil.


Hottinger (2006), Illustrated glossary of terms used in foraminiferal research. Carnets de Géologie, Memoir 2, ISSN 1634-0744

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