Acarinina mckannai


Classification: pf_cenozoic -> muricate non-spinose -> Truncorotaloididae -> Acarinina -> Acarinina mckannai
Sister taxa: A. africana, A. alticonica, A. angulosa, A. aspensis, A. boudreauxi, A. bullbrooki, A. coalingensis, A. collactea, A. cuneicamerata, A. echinata, A. esnaensis, A. esnehensis, A. interposita, A. mcgowrani, A. mckannai, A. medizzai, A. nitida, A. pentacamerata, A. praetopilensis, A. primitiva, A. pseudosubsphaerica, A. pseudotopilensis, A. punctocarinata, A. quetra, A. rohri, A. sibaiyaensis, A. soldadoensis, A. strabocella, A. subsphaerica, > >>

Taxonomy

Citation: Acarinina mckannai (White 1928)
Rank: Species
Basionym: Globigerina mckannai
Synonyms:
Taxonomic discussion: Acarinina mckannai is one of the most common and broadly distributed upper Paleocene acarininids and is easily recognized by its large, globular, muricate test with generally 5 to 6 chambers in the final whorl. This species is closely allied with A. subsphaerica, and, indeed, complete intergradation exists between them in spire height, umbilical size, and the number of chambers in the final whorl. Shutskaya (1958, 1970a) figured a large number of specimens as A. subsphaerica, some of which are clearly referable to A. mckannai due to their low spire height. [Olsson et al. 1999]

Catalog entries: Globigerina mckannai;

Type images:

Short diagnosis: Large, 4.5 to 6 chambers in final whorl, moderate to low spired, final chamber often curving partly over the umbilicus in high-spired variants; strongly muricate on the umbilical surface with deep, funnel-shaped entrances to the pores over the rest of the test; chambers slowly increasing in size in the final whorl; peripheral margin rounded with chambers elongate parallel to the coiling axis as well as elongate in the direction of coiling; sutures deep, straight, and incised on the umbilical surface, gently depressed on the spiral side and slightly curved; umbilicus deep and large; aperture interiomarginal, umbilical-extraumbilical without a 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: Large, 4.5 to 6 chambers in final whorl, moderate to low spired, final chamber often curving partly over the umbilicus in high-spired variants; strongly muricate on the umbilical surface with deep, funnel-shaped entrances to the pores over the rest of the test; chambers slowly increasing in size in the final whorl; peripheral margin rounded with chambers elongate parallel to the coiling axis as well as elongate in the direction of coiling; sutures deep, straight, and incised on the umbilical surface, gently depressed on the spiral side and slightly curved; umbilicus deep and large; aperture interiomarginal, umbilical-extraumbilical without a lip. [Olsson et al. 1999]

Character matrix

test outline:Circularchamber arrangement:Trochospiraledge view:Inequally biconvexaperture:Interiomarginal
umb chamber shape:Inflatedcoiling axis:Lowperiphery:N/Aaperture border:Thin lip
sp chbr shape:Inflatedumbilicus:Wideperiph margin shape:Moderately roundedaccessory apertures:None
umbilical or test sutures:Strongly depressedumb depth:Deepwall texture:Moderately muricateshell porosity:-
spiral sutures:Weakly depresseddiameter mm:0.4width mm:0.3breadth mm:-
final-whorl chambers:4.5-6.0

Biogeography and Palaeobiology


Geographic distribution: Acarinina mckannai is a broadly distributed species in the tropical to subtropical oceans. Specimens have been reported from the high southern latitudes (Huber, 1991b), although these are neither as coarsely muricate nor as inflated as typical low-latitude representatives of the species (Figure 19). [Olsson et al. 1999]
Aze et al. 2011 summary: Low latitudes; based on Olsson et al. (1999)

Isotope paleobiology: Acarinina mckannai has ∂18O slightly more negative than coexisting morozovellids, such as M. velascoensis, and shows no size related trends in ∂18O (Shackleton et al., 1985). The ∂13C of A. mckannai is much more positive than that of Subbotina and is similar to, or slightly more negative than, that of Morozovella and Igorina (Shackleton et al., 1985). [Olsson et al. 1999]
Aze et al. 2011 ecogroup 1 - Open ocean mixed-layer tropical/subtropical, with symbionts. Based on very heavy δ13C and relatively light δ18O. Sources cited by Aze et al. 2011 (appendix S3): Shackleton et al. (1985)

Phylogenetic relations: Acarinina mckannai evolved from A. subsphaerica by a reduction in spire height and an increase in whorl expansion rate. These taxa are the first acarininds to acquire a coarsely pustulose (muricate) ornamentation on the umbilical surface. Acarinina subsphaerica appears before A. mckannai in our material and retains the slightly anguloconic test shape of A. nitida, suggesting that A. subsphaerica is more primitive than A. mckannai. [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Zone P4a to lower Zone P4c. [Olsson et al. 1999]
Last occurrence (top): within P4c subzone (57.10-57.79Ma, top in Thanetian stage). Data source: Olsson et al. 1999
First occurrence (base): within P4b subzone (57.79-60.52Ma, base in Selandian 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. 48

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.


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Acarinina mckannai compiled by the pforams@mikrotax project team viewed: 21-8-2017

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