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Glossary of Terms used in Foraminiferal Research

(Preliminary Version 1997)

Lukas Hottinger and Verena Scheuring

Geological Institute, Basel University, Switzerland

The final and updated GLOSSARY is already available from:

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



The terminology used by various authors in describing the morphological features of the foraminiferal test is far from being unified and varies greatly from case to case (compare e.g. Reiss, 1963, Hottinger, 1978, Hottinger et al., 1990, 1993, Loeblich and Tappan, 1964, 1987). The reasons for the variety of terms for the same feature are in most cases not at all formal, but due to differences of opinion with regard to the significance of features, concerning homologies and analogies, to differences in levels of accuracy, as well as due to different methods of observation (Hottinger, 1978).

The terms listed in the following Glossary, are accompanied [in square brackets] by alternative terms used and (in round brackets) by terms considered to be synonymous, partially synonymous, unclear or for other reasons to be avoided.

Numbers following the definitions refer to selected Plate/Figures in Hottinger et al.1993 where the respective feature is illustrated.

For comments or suggestions, please fax Professor Lukas Hottinger at 41-61-267 3613.



  • Abaxial - directed away from or far from shell axis.
  • Aboral - opposite to apertural [oral] end.
  • Accessory aperture (infralaminal aperture, auct.) - opening that does not lead directly into the main chamber lumen, but extends beneath accessory structures (e.g. in bullae). 100/7,8.
  • Acicular - needle-shaped.
  • Acicular spine - see spine.
  • Acuminate - tapering, i.e. getting thinner or pointed; conical.
  • Acute - shape with acute or sharp angles.
  • Adapertural depression (periapertural depression; cavity; apertural fissure, auct.) - space formed by a toothplate and separated by the latter partly or completely from the main chamber lumen. Interconnected adapertural depressions produce a canal. 115/4. 119/15. 120/7. 124/7.
  • Adaxial - directed towards or positioned near the shell axis.
  • Advolute chamber arrangement - in spirally coiled forms where chamber lumina in whorl cover laterally those of the preceding whorl to a considerable extent, but not entirely, on one or both sides. Compare: evolute, involute. 2/5,6.
  • Acervuline - chambers in irregular, clustered arrangement, as in Acervulina.
  • Adauxiliary chamber - chamberlet arising from single radial stolon (additional in respect to apertures between proto- and deuteroconch) in the embryonic wall of orbitoidiform shells. Adventitious]] - produced by or with the help of foreign particles such as those forming an agglutinated test.
  • Agamogony - asexual reproduction within the reproduction cycle, from the first mitotic division of the zygote to meiosis.
  • Agamont - specimen grown from the zygote, producing either gamonts or schizonts in an asexual process involving apogamous nuclear divisions and/or meiosis. Foraminiferal agamonts, produced by a sexual reproduction, are microspheric (B]] - form).
  • Agglutinated - shell texture characterized by components gathered in the ambient environment and bound by organic or biomineralized cements produced by the cell. Particles may be selected according to size and shape to form a closefitting mosaic. Often, the agglutination in the external and internal parts of the wall is differentiated without sharp boundaries: external agglutination is finer-grained and better organized than internal parts. 1/1. 12/1. 29/4,10.
  • Alar prolongation - winglike extension of umbilico-lateral portions of involute chambers on lateral surfaces of previous whorls in lenticular tests. May be meandering. 182/1. 224/6.
  • Allopatric speciation - emergence of species by geographic isolation of populations for sufficient time to alter the genome of the populations involved to mutual reproductive incompatibility.
  • Alternation of generations - see life cycle.
  • Alveolar layer - layer of alveoles in lateral chamber walls forming diagnostic exoskeletal structures lacking a differentiation of beams and rafters as well as polygonal subepidermal patterns, as in opposition to subepidermal, polygonal networks or keriothecal textures.
  • Alveole (alveolus, pl. alveoli) - recess of varying depth coated by the organic lining in lateral chamber walls, blindly ending with a rounded contour below an epiderm or some equivalent outer layer of the wall and opening into the chamber lumen. May be branching towards the outer part of the wall, each generation of branches forming layers within the wall.
Remarks: The term alveole is used here exclusively for exoskeletal structures, i.e. for subepidermal, tiny compartments of the chamber cavity coated by organic lining. Alveoles must be distinguished from paraporous or keriothecal cavities belonging to the wall texture. The latter are (by definititon) not filled with living chamber plasm nor coated by the organic lining. The simultaneous presence of both alveolar structures and keriothecal wall texture in the fusulinid Verbeekina and its relatives, the combination of an alveolar exoskeleton with a paraporous external wall in Dicyclina or with a bilamellar perforate wall in Fabiania supports a consequent restriction of the term's use to exoskeletal structures, never to textures.
Layers of alveoles coating the lateral chamber wall are present in various agglutinated groups of which Cyclammina is the most prominent while Everticyclammina is an early extinct representative of an exoskeletal layer of exclusively undivided, shallow alveoles. The Neogene group of Textulariella (GrÚnhagen and Luterbacher, 1966) has branching alveoles. Among the porcelaneous foraminifera, Austrotrillina may be an unique group. In this genus, species with deep and branching alveoles (A. howchini, Adams, 1968) are said to evolve from earlier forms with layers of shallow, undivided alveoles.
The term alveole is also used for rows of blind recesses in postseptal position over supplementary apertures in the previous septal face as in Subalveolina or Bullalveolina. We do not yet know, how to interpret (in terms of exo- or endoskeletal elements) these alveoles nor what might be their biological meaning.
  • Annular canal - free space between endo- and exoskeletal structures in spirocyclinids.
Remarks: Unrelated to canal systems in lamellar perforate foraminifera. The term should not be used but replaced by annular space. Annular chamber]] - ring-shaped. May be subdivided. 82/1,4. 226/5. 227/5.
  • Annular passage - see preseptal passage.
  • Annulus - ring-shaped chamber, wich may be subdivided, or ring-shaped cycle of chamberlets.
  • Anterior - directed to or positioned near or on frontal part of chamber, usually enclosing main aperture, distal in respect to direction of growth.
  • Antetheca - apertural face in fusulinids.
  • Apertural axis - see milioline coiling.
  • Apertural chamberlet - cavity in preseptal position below radiate aperture in Lenticulina and related forms. Lamellar nature of septal wall between main chamber and apertural chamberlet unclear.
  • Apertural face - surface of chamber-wall comprizing the main cameral aperture.
  • Apertural flange - see lip.
  • Apertural lip - see lip.
  • Apertural plate /basal plate/ - a plate-like structure along the base of an interiomarginal aperture and restricting the latter. 147/6,9.
  • Apertural tooth - see miliolid tooth and valvular tooth.
  • Aperture - primary opening within the test or between test elements, putting into communication intrathalamous with extrathalamous cytoplam. May be single or multiple. (See cameral aperture; foliar aperture; supplementary aperture; labial aperture).
  • Apex - initial portion of trochospiral or conical test.
  • Apical - referring to initial part of trochospiral or conical test.
  • Apogamy - reproduction process where the offspring has the same number of chromosomes than the parent cell.
  • Arborescent - branching growth-pattern in tree-like manner of permanently attached tests. 176/1.
  • Areal - aperture and/or intercameral foramen: position of aperture(s) and/or foramina within apertural face, not at its base nor at the shell margin.
  • Areal aperture - cameral aperture in distal wall, not at suture. May be single or multiple. 2/14,16. 79/15. 129/6.
  • Arenaceous - see agglutinated.
  • Areolate - chamber wall subdivided into more or less equal surfaces (areoli) as in Homotrema.175/7,8.
  • Astral fissure - see folium, foliar aperture, foliar suture.
  • Astral furrow - see foliar suture.
  • Astral lobe - see folium.
  • Attics (French: mansardes) - outermost lateral or abaxial chamberlet layer in multiple-layered endoskeletal chamber structures of porcelaneous shells distinguished from less lateral or adaxial ones by its comparatively small caliber and its higher number per unit chamber wall surface.
  • Autogamy - sexual reproduction process where amoeboid gametes from the same gamont mate (in foraminifera within the mother shell) to form a zygote. May be combined with gamontogamy.
  • Auxilliary tunnel - coalescence of several cuniculi as in Polydiexodina.
  • Axial filling - secondary deposits in narrow spaces around the axial columella in fusulinids and pfenderinids. Axial section]] - slice bisecting test in plane coinciding with axis of coiling and intersecting proloculus. 82/1. 75/5. 214/1.
  • Axial septulum (in verbeekinid fusulinids) - exoskeletal structural element parallel to septum and consequently corresponding to the rafter in other exoskeletons of agglutinated foraminifera.
  • Axis of coiling - imaginary line around which spiral test is coiled.