Parasubbotina variospira


Classification: pf_cenozoic -> Globigerinidae -> Parasubbotina -> Parasubbotina variospira
Sister taxa: P. griffinae, P. eoclava, P. hagni, P. prebetica, P. inaequispira, P. pseudowilsoni, P. variospira, P. varianta, P. pseudobulloides, P. aff. pseudobulloides, P. sp.,

Taxonomy

Citation: Parasubbotina variospira (Belford 1984)
Rank: Species
Basionym: Globorotalia (Turborotalia) variospira
Synonyms:
Taxonomic discussion: Although described a decade ago, this species has been overlooked in studies of Paleocene planktonic foraminiferal faunas. This absence of attention is surprising because P. variospira is large and homeomorphic with the Neogene species Neogloboquardina dutertrei (d'Orbigny). Van Eijden and Smith (1992) drew attention to the distinct features of this large mid-Paleocene taxon and noted its globoquadrinid-like umbilical "teeth" that are unique among Paleocene species. Parasubbotina variospira overlaps for a short stratigraphic interval with Globanomalina pseudomenardii and early members of the acarininid radiation (nitida, mckannai, subsphaerica) within the lowermost part of Zone P4. [Olsson et al. 1999]

Catalog entries: Globorotalia (Turborotalia) variospira

Type images:

Distinguishing features: Test large (0.4-0.7 mm), loosely coiled, with strongly lobulate outline. Any or all of the last 3-4 chambers with inwardly projecting umbilical teeth. Aperture interiomarginal, umbilical-extraumbilical arch; occasional secondary spiral apertures. Wall spinose and distinctly cancellate with large pore pits.

NB These concise distinguishing features statements are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus.
They are being edited as the site is developed and comments on them are especially welcome.

Description


Diagnostic characters: Large ( 0.4 to 0.7 mm in diameter), low to (less frequent) moderately high, loosely coiled trochospiral test with strongly lobulate outline; any or all of the last 3-4 chambers with inwardly projecting umbilical teeth, aperture an interiomarginal, umbilical-extraumbilical arch; loose coiling between chambers in the final whorl occasionally produces secondary spiral apertures with apertural lips, wall texture spinose and distinctly cancellate with large pore pits. [Olsson et al. 1999]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Planoconvexaperture:Umbilical-extraumbilical
sp chamber shape:Globularcoiling axis:Moderateperiphery:N/Aaperture border:Teeth
umb chbr shape:Inflatedumbilicus:Wideperiph margin shape:Broadly roundedaccessory apertures:None
spiral sutures:Strongly depressedumb depth:Shallowwall texture:Cancellateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Strongly depressedfinal-whorl chambers:4.0-4.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology


Geographic distribution: This species has been observed at (sub)tropical sites in the Atlantic, Indian, and Pacific oceans. [Olsson et al. 1999]
Aze et al. 2011 summary: Low latitudes; based on Olsson et al. (1999)

Isotope paleobiology: Parasubbotina variospira has a ∂13C and ∂18O signature similar to P. pseudobulloides, P. varianta, Subbotina triloculinoides, and Globanomalina compressa, but it typically has a heavier ∂18O and more negative ∂13C than coexisting Morozovella. [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): Olsson et al. (1999); Pearson et al. (2001a)

Phylogenetic relations: This species evolved from P. varianta by the development of a more loosely coiled test and inflated chambers. Both P. varianta and P. variospira share enlarged apertural flaps. These structures are restricted to the final chamber of P. varianta but are found on the last 3-4 chambers in the final whorl of P. variospira. [Olsson et al. 1999]

Most likely ancestor: Parasubbotina varianta - at confidence level 4 (out of 5). Data source: Olsson et al. 1999 f.5.

Biostratigraphic distribution

Geological Range:
Notes: Zone P3a to Zone P4 (lower part). [Olsson et al. 1999]
The LAD of Parasubbotina variospira marks the base of zone P4b / top of P4a (Wade et al. 2011)
Last occurrence (top): at top of P4a subzone (100% up, 60.5Ma, in Selandian stage). Data source: zonal marker (Wade et al. 2011)
First occurrence (base): at base of P3a subzone (0% up, 62.3Ma, in Danian stage). Data source: zonal marker (Wade et al. 2011)

Plot of occurrence data:

Primary source for this page: Olsson et al. 1999 - Atlas of Paleocene Planktonic Foraminifera, p. 28

References:

Belford, D. J. (1984). Tertiary foraminifera and age of sediments, Ok Tedi-Wabag, Papua New Guinea. Bureau of Mineral Resources, Australia, Bulletin. 216: 1-52. gs

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

van Eijden, A. J. M. & Smit, J. (1992). Eastern Indian Ocean Cretaceous and Paleogene Quantitative Biostratigraphy. Proceedings of the Ocean Drilling Program, Scientific Results. 121: 77-124. gs


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Parasubbotina variospira compiled by the pforams@mikrotax project team viewed: 22-10-2019

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