Acarinina medizzai

Classification: pf_cenozoic -> Truncorotaloididae -> Acarinina -> Acarinina medizzai
Sister taxa: A. medizzai, A. collactea, A. pentacamerata, A. aspensis, A. interposita, A. echinata, A. pseudosubsphaerica, A. alticonica, A. soldadoensis, A. cuneicamerata, A. angulosa, A. africana, A. sibaiyaensis, A. esnehensis, A. mckannai, A. subsphaerica ⟩⟨> >>


Citation: Acarinina medizzai (Toumarkine & Bolli 1975)
Rank: Species
Basionym: Globigerina medizzai
Taxonomic discussion:

This species is closely related to, and possibly synonymous with, Acarinina rugusoaculeata Subbotina. The latter was distinguished from A. medizzai by Toumarkine and Bolli (1975) on having a more umbilically positioned aperture and based on the presence of a final chamber that is larger and less detached from the previous chambers. Although Subbotina described her species as having a slit-like aperture that extends along the sutural margin, the apertural position in the holotype is not apparent from the illustration (e.g., Subbotina, 1953, pl. XXV: figs. 4a, b), and one of the other illustrated specimens that clearly does have an extraumbilical aperture and was designated as A. rugosoaculeata by Subbotina (1953, pl. XXV: figs. 6a, b) lacks a muricate wall texture and therefore should not be included in Acarinina. This ambiguity cannot be cleared up from study of Subbotina’s collection since the holotype and other specimens originally assigned to A. rugosoaculeata have been lost (E .M. Bugrova, pers. comm., 2003). Until specimens from the type level of the A. rugosoaculeata holotype can be studied and compared with A. medizzai we have chosen to suppress A. rugosoaculeata in favor of recognition of the better-documented species A. medizzai. [Berggren et al. 2006]

Catalog entries: Globigerina medizzai, Acarinina rugosoaculeata

Type images:

Distinguishing features: Like A. collactea but smaller (<0.2 mm), lower trochospiral, test; and with smaller, often indistinct aperture

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: Moderately to coarsely muricate, normal perforate, nonspinose. [Wade & Kucenjak 2018]

Morphology: Test relatively small, biconvex, quadrate to subcircular in outline, weakly to moderately lobate with a rounded periphery; chambers globular, 8-12 arranged in a low trochospire of 3-4 whorls, increasing moderately in size, 4-6 in the final whorl, rarely kummerform; umbilicus narrow in more compact specimens, shallow and broad in more evolute forms; sutures weakly depressed, radial on both sides; aperture a small and often indistinct low umbilical to slightly extraumbilical arch (modified from Berggren and others, 2006). [Wade & Kucenjak 2018]

Size: Maximum diameter of holotype 0.19 mm; test sizes range from 0.16 to 0.20 mm. [Wade & Kucenjak 2018]

Character matrix

test outline:Lobatechamber arrangement:Trochospiraledge view:Equally biconvexaperture:Umbilical
sp chamber shape:Inflatedcoiling axis:Lowperiphery:N/Aaperture border:N/A
umb chbr shape:Inflatedumbilicus:Wideperiph margin shape:Moderately roundedaccessory apertures:None
spiral sutures:Moderately depressedumb depth:Shallowwall texture:Finely muricateshell porosity:Finely Perforate: 1-2.5µm
umbilical or test sutures:Moderately depressedfinal-whorl chambers:4.0-6.0 N.B. These characters are used for advanced search. N/A - not applicable

Biogeography and Palaeobiology

Geographic distribution: This species has a cosmopolitan distribution but is often unreported, perhaps because of its small size and/or incorrect identification. [Berggren et al. 2006] In the Oligocene we have recorded this species from the Adriatic Sea and western Indian Ocean. [Wade & Kucenjak 2018]

Isotope paleobiology: No data available. [Wade & Kucenjak 2018]
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 - i.e. inferred from closely-related species.

Phylogenetic relations: Probably descended from Acarinina collactea. [Wade & Kucenjak 2018]

Most likely ancestor: Acarinina collactea - at confidence level 3 (out of 5). Data source: Berggren et al. (2006) fig9.2; Wade & Kucenjak 2018.

Biostratigraphic distribution

Geological Range:
Notes: The range is poorly constrained. Acarinina medizzai evolved in middle Eocene Zone E10 (Berggren and others, 2006). Our youngest recorded occurrences are from Zone O4. [Wade & Kucenjak 2018]
Last occurrence (top): within O4 zone (28.09-29.18Ma, top in Rupelian stage). Data source: Wade & Kucenjak 2018
First occurrence (base): in upper part of E10 zone (80% up, 42.2Ma, in Lutetian stage). Data source: Berggren et al. 2006

Plot of occurrence data:

Primary source for this page: Wade & Kucenjak 2018 - Olig Atlas chap.13 p.397; Berggren et al. 2006 - Eocene Atlas, chap. 9, p. 292


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Acarinina medizzai compiled by the pforams@mikrotax project team viewed: 19-4-2021

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