Acarinina pseudotopilensis

Classification: pf_cenozoic -> Truncorotaloididae -> Acarinina -> Acarinina pseudotopilensis
Sister taxa: << < A. cuneicamerata, A. angulosa, A. africana, A. sibaiyaensis, A. esnehensis, A. mckannai, A. subsphaerica ⟩⟨ A. bullbrooki, A. punctocarinata, A. boudreauxi, A. rohri, A. topilensis, A. praetopilensis, A. mcgowrani, A. quetra, A. pseudotopilensis, A. wilcoxensis, A. esnaensis, A. primitiva, A. coalingensis, A. nitida, A. strabocella, A. sp.


Citation: Acarinina pseudotopilensis Subbotina 1953
Rank: Species
Basionym: Acarinina pseudotopilensis
Taxonomic discussion: Acarinina pseudotopilensis was originally described from the Zone of compressed globorotaliids and Zone of conical globorotaliids (roughly equivalent to Zones P4-E6 of this study) in the northern Caucasus (Subbotina, 1953), although all illustrated specimens were from the Eocene part of this range. Test shape/geometry and ornament would seem to place this morphotype between Acarinina wilcoxensis and A. quetra. Blow (1979) indicated a range from Zone P6 to P10 (=E3-E8) but illustrated forms only from (his) Zones P6 to P8b (=Zones E3-E5) and it is in this (bio)stratigraphic interval that this form develops its characteristic morphology. We have not observed morphotypes referable to pseudotopilensis below upper Zone P5 in the course of our studies.
Blow (1979) considered that pseudotopilensis was the stem form of a lineage that led to Acarinina topilensis in the middle Eocene, and he named a new species, praetopilensis, for an intermediate morphology that first appears in Zone P9 (=E7 of this paper) and shows the beginnings of circum-cameral fusion of muricae that is more strongly developed in topilensis. [Berggren et al. 2006]

Catalog entries: Acarinina pseudotopilensis

Type images:

Distinguishing features: Like A. wilcoxensis but with triangular to wedge- or cuneate-shaped chambers in the final whorl, disjunct (separation of) chamber margins and more densely muricate wall.

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.


Wall type: Densely muricate, nonspinose, normal perforate. [Berggren et al. 2006]

Morphology: Subquadrate to suboval, weakly lobulate outline; 4 inflated chambers in last whorl; umbilical sutures distinct, radial, depressed/incised, with result that chamber contact(s) are disjunct along peripheral margin in some individuals; chambers densely muricate (marked by blunt, triangular muricae), concentrated along periphery but not forming a muricocarina; umbilicus small, deep, in many individuals obscured by overhanging, rounded umbilical shoulder; aperture an umbilical-extraumbilical low arch, extending towards the peripheral margin, bordered in most individuals by a thin lip; 10-12 chambers on spiral side disposed in 2 to 3 whorls; early whorl(s) slightly elevated; chambers tangentially longer than radially broad, meeting at nearly right angles, increasing gradually in size, often assuming a subrectangular shape; final chamber strongly inflated in some individuals and assuming a markedly rectangular or even cuneate/trapezoidal shape; murical development highly variable but concentrated generally along the peripheral margin; discrete, sutural openings visible on some individuals (often obscured by muricae on overhanging edges of previous/adjacent chambers); plano-convex in edge view; spiral side slightly elevated); ventral (umbilical) margin(s) rounded to anguloconical. [Berggren et al. 2006]

Character matrix

test outline:Subquadratechamber arrangement:Trochospiraledge view:Planoconvexaperture:Umbilical-extraumbilical
sp chamber shape:Inflatedcoiling axis:Lowperiphery:N/Aaperture border:N/A
umb chbr shape:Inflatedumbilicus:Narrowperiph margin shape:Broadly roundedaccessory apertures:Sutural
spiral sutures:Moderately depressedumb depth:Shallowwall texture:Coarsely muricateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Moderately 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: Widely distributed in (sub)tropical regions (Caribbean, North and South Atlantic, Indo-Pacific Oceans, Tethyan region (East, West and North Africa, North Caucasus). [Berggren et al. 2006]
Aze et al. 2011 summary: Low latitudes; based on Berggren et al. (2006b)

Isotope paleobiology: Boersma and others (1987) record this species with relatively negative ∂18O indicating a shallow water habitat like other acarininids. [Berggren et al. 2006]
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): Boersma et al. (1987)

Phylogenetic relations: Evolved from A. wilcoxensis shortly after the first appearance of that species in the latest Paleocene and was ancestral to A. quetra in the early Eocene and A. boudreauxi and A. mcgowrani in the later part of the early Eocene. [Berggren et al. 2006]

Most likely ancestor: Acarinina wilcoxensis - at confidence level 4 (out of 5). Data source: Berggren et al. (2006) fig9.2.
Likely descendants: Acarinina boudreauxi; Acarinina mcgowrani; Acarinina quetra;

Biostratigraphic distribution

Geological Range:
Last occurrence (top): within E7a subzone (48.31-50.20Ma, top in Ypresian stage). Data source: Eocene Atlas
First occurrence (base): within E1 zone (55.81-55.96Ma, base in Ypresian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Berggren et al. 2006 - Eocene Atlas, chap. 9, p. 305


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Berggren, W. A., Pearson, P. N., Huber, B. T. & Wade, B. S. (2006b). Taxonomy, biostratigraphy, and phylogeny of Eocene Acarinina. In, Pearson, P. N., Olsson, R. K., Hemleben, C., Huber, B. T. & Berggren, W. A. (eds) Atlas of Eocene Planktonic Foraminifera. Cushman Foundation for Foraminiferal Research, Special Publication. 41(Chap 9): 257-326. gs V O

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Acarinina pseudotopilensis compiled by the pforams@mikrotax project team viewed: 21-4-2021

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