Acarinina strabocella


Classification: pf_cenozoic -> muricate non-spinose -> Truncorotaloididae -> Acarinina -> Acarinina strabocella
Sister taxa: << < 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, A. topilensis, A. wilcoxensis, A. sp.,

Taxonomy

Citation: Acarinina strabocella (Loeblich and Tappan 1957)
Rank: Species
Basionym: Globorotalia strabocella
Synonyms:
Taxonomic discussion: Shutskaya (1956; see also 1970a, 1970b) described Globorotalia angulata var. praepentacamerata from the lower Paleocene of the northern Caucasus and showed that it had a wide distribution in the southwestern part of the former Soviet Union. Luterbacher (1964:665) suggested that Globorotalia strabocella Loeblich and Tappan may be a junior synonym. We agree with this assessment particularly inasmuch as comparison of our material with the holotype of G. strabocella at the NMNH shows them to be morphologically similar. In view of the fact that there is no original (type) material remaining of Shutskaya's taxon (nor of any other taxa that she described, for that matter, with rare exception), we prefer to use the name strabocella for this taxon because of the fact that there is well-preserved type material at a readily accessible museum (the NMNH in Washington), which aids in stabilizing the nomenclature.
Shutskaya (1970b: 118, 120, fig. 13) showed that A. praepentacamerata is restricted to the A. praepentacamerata Zone and the lower subzone of the overlying A. tadjikistanensis djanensis Zone in the southwestern part of the former Soviet Union [= Zone P3 (middle part) to ? P4 [lower part)]. This is similar to our observations. The forms referred to A. wilcoxensis strabocella from Zones P6-P8b by Blow (1979:970, pis.
114, 129, 132, 251) are considered unrelated to strabocella; they differ in their more evolute coiling, flatter spiral coil, and strongly muricate ornament. They represent a younger, more advanced acarininid morphology than that seen in A. strabocella. In fact, we view A. strabocella as representing the stem form of the acarininid radiation that occurred at the P3-P4 zonal transition. [Olsson et al. 1999]

Catalog entries: Globorotalia angulata praepentacamerata; Globorotalia strabocella;

Type images:

Short diagnosis: 5-6 chambered, nearly circular test with weakly lobulate outline; axial periphery broadly rounded to subangular, chambers on umbilical side moderately convex, early whorls on spiral side elevated above later whorl(s); umbilicus usually broad and open exposing earlier whorls; test weakly pustulose (muricate) over the entire surface of the test, aperture an interiomarginal, umbilical-extraumbilical slit.

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: 5-6 chambered, nearly circular test with weakly lobulate outline; axial periphery broadly rounded to subangular, chambers on umbilical side moderately convex, early whorls on spiral side elevated above later whorl(s); umbilicus usually broad and open exposing earlier whorls; test weakly pustulose (muricate) over the entire surface of the test, aperture an interiomarginal, umbilical-extraumbilical slit. [Olsson et al. 1999]

Character matrix

test outline:Lobatecoiling axis:Lowchamber arrangement:Trochospiralumbilicus:Wide
edge view:Equally biconvexumbilical or test sutures:Strongly depressedspiral sutures:Strongly depressedshell porosity:Finely Perforate: 1-2.5
wall texture:Spinoseaperture:Umb.-extraumbilicalaperture border:N/Aaccessory apertures:None
periphery:N/Aumb chamber shape:Inflatedsp chbr shape:Inflatedperiph margin shape:Broadly rounded
umb depth:Shallowdiameter mm:0.33width mm:-breadth mm:-
final-whorl chambers:5.0-6.0

Biogeography and Palaeobiology


Geographic distribution: Northern middle latitudes to the Southern Ocean (Figure 21). [Olsson et al. 1999]
Aze et al. 2011 summary: Northern middle latitudes to the Southern Ocean; based on Olsson et al. (1999)

Isotope paleobiology: No data available. [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): this study

Phylogenetic relations: The origin of the first Acarinina species is somewhat obscure. The wall surface ofA. strabocella is smooth with simple and coalescent pustules (Plate 5: Figure 1) that become more heavily developed on the older part of the test. The origin of this species may be linked with the moderately pustulose Morozovella praeangulata in the lower part of Zone P3 and may have diverged from early forms of this species. Alternatively, A. strabocella may have evolved from Praemurica inconstans by developing a tighter coil and a lower rate of chamber enlargement. In any case, A. strabocella represents the stem form of the acarininid radiation. Reduction of the number of chambers in the final whorl and the increased development of muricae are seen in the derivation of A. nitida from A strabocella. [Olsson et al. 1999]

Biostratigraphic distribution

Geological Range:
Notes: Zone P3 (lower part) to Zone P4 (lower part). [Olsson et al. 1999]
Last occurrence (top): within P4 zone (57.10-60.73Ma, top in Thanetian stage). Data source: Olsson et al. 1999
First occurrence (base): within P3 zone (60.73-62.29Ma, 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. 50

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 strabocella compiled by the pforams@mikrotax project team viewed: 27-7-2017

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