Eoglobigerina spiralis


Classification: pf_cenozoic -> spinose -> Globigerinidae -> Eoglobigerina -> Eoglobigerina spiralis
Sister taxa: E. edita, E. eobulloides, E. spiralis,

Taxonomy

Citation: Eoglobigerina spiralis (Bolli 1957)
Rank: Species
Basionym: Globigerina spiralis
Synonyms:
Taxonomic discussion: Bolli (1957a) regarded E. spiralis as the immediate ancestor of Igorina pusilla (Bolli). Although Blow (1979) agreed with Bolli, he noted that the transition from spiralis to pusilla involved the loss of a porticus as well as the extraumbilical extension of the aperture. Blow placed great emphasis on the importance of the porticus as distinct from an apertural lip. The study of Olsson et al. (1992) on the wall texture of Danian globigerinids and globorotaliids, however, showed that the separation of these two kinds of apertural apparatuses is erroneous, as the apparent differences noted by Blow are due to ontogenetic and gametogenetic calcification. The fact that Blow (1979:1223) regarded the spiralis -pusilla -albeari lineage as "so remarkably taxonomically and stratigraphically isolated" indicates that he considered the morphological change involved in the origin of pusilla (i.e., Igorina) as quite distinct from the mainstream globigerinacean evolutionary history. His belief holds true to some degree in regards to the origin of the Igorina lineage (see "Discussion" under this genus). The ancestral relationship of spiralis to pusilla must be ruled out, however, because the former species has a spinose wall texture whereas the latter has a nonspinose, praemuricate wall texture. Eoglobigerina spiralis is the end member of the eobulloides-edita -spiralis lineage, which terminated in Zone P2 (see also Pearson, 1993).
Our work has revealed a spinose wall texture in E. spiralis and suggests that these spinose forms are unrelated to the nonspinose igorinids; however, we have recognized an apparently nonspinose wall texture in some specimens that we have initially attributed to E. spiralis. Indeed, the holotype of E. spiralis is too poorly preserved to verify the original presence or absence of spines. Consequentially, we are not completely sure of the generic designation of this species. Should the paratypes of E. spiralis prove to have a nonspinose wall texture, we would be forced to consider this taxon as a possible ancestor to I. pusilla as originally suggested by Bolli (1957a) and to regard the spinose homeomorphs as derivatives of Eoglobigerina edita. [Olsson et al. 1999]

Catalog entries: Globigerina spiralis;

Type images:

Short diagnosis: This spinose species has a distinct elevated spire and 4½ to 5½ chambers in the ultimate whorl. The chambers are closely appressed with an umbilically directed aperture. The radially directed intercameral sutures on the umbilical side appear as distinct valleys when surrounded by gametogenetic calcification. A thin discontinuous lip borders the aperture. The wall texture is more strongly developed than in the ancestral species, E. edita. The umbilicus is very small and is often overlapped by the ultimate chamber. The spine holes which are set along the cancellate ridges appear not to be as numerous as in E. edita.

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: This spinose species has a distinct elevated spire and 4½ to 5½ chambers in the ultimate whorl. The chambers are closely appressed with an umbilically directed aperture. The radially directed intercameral sutures on the umbilical side appear as distinct valleys when surrounded by gametogenetic calcification. A thin discontinuous lip borders the aperture. The wall texture is more strongly developed than in the ancestral species, E. edita. The umbilicus is very small and is often overlapped by the ultimate chamber. The spine holes which are set along the cancellate ridges appear not to be as numerous as in E. edita. [Olsson et al. 1999]

Character matrix

test outline:Lobatecoiling axis:Moderate-highchamber arrangement:Trochospiralumbilicus:Narrow
edge view:Inequally biconvexumbilical or test sutures:Moderately depressedspiral sutures:Moderately depressedshell porosity:Finely Perforate: 1-2.5
wall texture:Smoothaperture:Umb.-extraumbilicalaperture border:Thin lipaccessory apertures:None
periphery:N/Aumb chamber shape:Inflatedsp chbr shape:Inflatedperiph margin shape:Broadly rounded
umb depth:Deepdiameter mm:0.28width mm:-breadth mm:-
final-whorl chambers:5.0-6.0

Biogeography and Palaeobiology


Geographic distribution: Apparently worldwide in high to
low latitudes (Figure 9). [Olsson et al. 1999]
Aze et al. 2011 summary: Cosmopolitan; based on Olsson et al. (1999)

Isotope paleobiology: No data available. [Olsson et al. 1999]
Aze et al. 2011 ecogroup 3 - Open ocean thermocline. Based on light δ13C and relatively heavy δ18O. Sources cited by Aze et al. 2011 (appendix S3): this study

Phylogenetic relations: This species evolved from E. edita
near the base of Zone P2 by the development of a tighter coil, a distinct elevated early coil of chambers, and a more strongly cancellate test wall. [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Zone P2; ? uppermost Zone Pic. [Olsson et al. 1999]
Last occurrence (top): within P2 zone (62.29-62.60Ma, top in Danian stage). Data source: Olsson et al. 1999
First occurrence (base): within P1c subzone (62.60-63.90Ma, base in Danian stage). Data source: Olsson et al. 1999

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 22

References:

Olsson, R.K.; Hemleben, C.; Berggren, W.A. & Huber, B.T., (1999). Atlas of Paleocene Planktonic Foraminifera. Smithsonian Contributions to Paleobiology. Smithsonian Institution Press, Washington, DC, 1-252 pp.


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

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