Dentoglobigerina


Classification: pf_cenozoic -> muricate non-spinose -> Globoquadrinidae -> Dentoglobigerina
Sister taxa: Dentoglobigerina,
Daughter taxa (blue => in age window 0-300Ma)
The species is characterized by its oval-shaped chambers that surround the umbilicus, the bending and flattening of the ultimate chamber into the umbilicus, and the umbilically confined aperture with an irregular, triangular-shaped lip that projects over the umbilical opening.
The species is characterized by its compact, subcircular to subquadrate test, embracing chambers, and umbilically centered aperture that is bordered by an irregular, subtriangular-shaped lip that projects over the umbilicus, and concentration of pustules in the apertural area. Its test is more compact and the chambers are more flattened than in D. galavisi. Note that the holotype is slightly aberrant in having a final chamber that is about the same size as the penultimate chamber. More regular specimens with proportionally large final chambers are more globular in shape (see Plate 13.2).
The species is characterized by its compact, subcircular to subquadrate test, embracing chambers, a cap-like ultimate chamber that extends over the umbilicus, and an umbilically centered aperture that is bordered by an irregular, subtriangular-shaped lip that projects over the umbilicus.

Taxonomy

Citation: Dentoglobigerina Blow, 1979
Rank: Genus
Type species: Globigerina galavisi Bermúdez, 1961
Taxonomic discussion: Dentoglobigerina was erected by Blow (1979) with Globigerina galavisi Bermúdez as the type species. We operate a modified concept of the genus because we exclude from it many of Blow’s hypotype specimens of galavisi (which we regard as subbotinids). In erecting the genus, Blow (1979) emphasized the taxonomic importance of the apertural apparatus, which he termed a “portical umbilical-tooth”. He believed that this was a feature that was added onto the chamber wall after the formation of the chamber in contrast to the apertural lip, which was formed as part of the wall during the development of the chamber. Little was known about the ontogeny of planktonic foraminifera at the time that Blow proposed this hypothesis but numerous subsequent studies have shown that apertural apparatuses are features that develop during chamber formation and are part of the chamber wall, not an addition to it. Consequently, the term “portical umbilical-tooth” has no taxonomic validity, although we do consider the umbilical tooth as a diagnostic feature of the genus.
Blow (1979) thought that Dentoglobigerina was derived from Subbotina and separated it from that genus on the basis of an apertural lip (referred to as a porticus by Blow, p. 1247) that extended “across the width of the aperture without distinct variation in the width” (p. 1247) and by “not having its aperture directed into the umbilicus” (p. 1247). The distinction of an umbilically restricted aperture is useful in distinguishing morphotypes of Dentoglobigerina from Subbotina, which differs by having an asymmetrically umbilical-extraumbilical aperture. The two genera are, however, fundamentally different in that one is spinose (Subbotina) and the other nonspinose (Dentoglobigerina). Blow (1979) separated Dentoglobigerina from Globoquadrina on the basis of the ontogenetic development of the aperture. The aperture in Globoquadrina (using the morphology of the type species G. dehiscens) was said to develop from an umbilical position to a more extraumbilical position whereas Dentoglobigerina retained an umbilical position. The seemingly extraumbilical position of the aperture in dehiscens is more a result of the flattening of the umbilical face that makes the aperture appear slightly extraumbilical. Despite this, we recognize the acute bending of the ultimate chamber over the umbilicus, the smooth umbilical face, and the symmetrical umbilical tooth as features that separate Globoquadrina from Dentoglobigerina.
The first appearance of Dentoglobigerina has not been clearly defined, although Berggren and others (1995) note its presence in Zone E14, which straddles the middle/upper Eocene boundary. We believe that Dentoglobigerina may have descended from an acarininid ancestor. The nonspinose Dentoglobigerina may have adapted to a deeper habitat (possibly around the nutricline) in the water column than the shallow-dwelling acarininids. This seems to be the case for all the subsequently evolved species of the genus. The wall became less pustulose, with pustules clustering around the aperture, and more cancellate. A distinctive high porosity honeycomb wall texture developed which has been termed Globoquadrina-type (Hemleben and others, 1991). Once the morphology of Dentoglobigerina became stabilized it became an easily recognized taxon due to its distinctive triangular umbilical tooth and the bending of the chamber into the umbilicus, thereby confining the tooth to the umbilicus.
[Olsson et al. 2006]

Catalog entries: Dentoglobigerina;

Type images:

Short diagnosis: The genus is characterized by a trochospirally coiled test, normal perforate, cancellate, nonspinose Globoquadrina-type wall texture, with an umbilical aperture bordered by an asymmetrically triangular lip (umbilical tooth). The number of chambers in the final whorl varies from 3½-6. The chambers are subglobular and slightly compressed and are in varying degrees bent into the umbilical depression along with the apertural lip.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: The genus is characterized by a trochospirally coiled test, normal perforate, cancellate, nonspinose Globoquadrina-type wall texture, with an umbilical aperture bordered by an asymmetrically triangular lip (umbilical tooth). The number of chambers in the final whorl varies from 3½-6. The chambers are subglobular and slightly compressed and are in varying degrees bent into the umbilical depression along with the apertural lip.
[Olsson et al. 2006]

Wall type: Cancellate, Globoquadrina-type honeycomb wall texture, nonspinose. [Olsson et al. 2006]

Test morphology: Trochospiral, globular, slightly lobate in outline, ultimate chamber slightly bent towards the umbilicus, forming an ill-defined apertural face; weakly pustulose except in the apertural area which is more heavily pustulose; primary aperture umbilical with an asymmetrical triangular tooth.
[Olsson et al. 2006]

Biogeography and Palaeobiology


Phylogenetic relations: Dentoglobigerina evolved in Zone E13 (possible earlier) by the development of asymmetrical triangular umbilical lips which project into the umbilicus due to a bending of the chamber into the umbilicus and a honeycomb wall texture. Its ancestor has not been established, although an acarininid ancestor is possible.
[Olsson et al. 2006]

Biostratigraphic distribution

Geological Range:
Notes: Zone E13 to the middle Pliocene.
[Olsson et al. 2006]
Last occurrence (top): within Chattian Stage (23.03-28.09Ma, top in Chattian stage). Data source: Total of range of species in this database
First occurrence (base): within Bartonian Stage (37.75-41.15Ma, base in Bartonian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Olsson et al. 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 13, p. 401

References:

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden, 1413 pp.

Hemleben, C.; Mhlen, D.; Olsson, R.K. & Berggren, W.A., (1991). Surface texture and the first occurrence of spines in planktonic foraminfera from the early Tertiary. Geologisch Jarhbuch, 128: 117-146.

Olsson, R.K.; Hemleben, C. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Dentoglobigerina. In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Cushman Foundation Special Publication. Allen Press, Lawrence, Kansas, pp. 401-412.


Dentoglobigerina compiled by the pforams@mikrotax project team viewed: 29-5-2017

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