Acarininaboudreauxi Fleisher, 1974:1112, pl. 1: figs. 2-5 [lower middle Eocene Zone P11, DSDP Site 219, Arabian Sea].
Taxonomic discussion: This taxon has rarely been used, but is nevertheless a distinctive form. Originally described from Zones P9 to P11 in the Arabian Sea area, it has recently been found at the same levels in Tanzanian drill cores (Pl.9.5, Figs. 13-16). Acarininaboudreauxi is clearly related to the A. bullbrooki group, particularly the matthewsae morphotype described by Blow (1979) (here considered conspecific with bullbrooki) but appears lower/earlier in the record, and provides a possible evolutionary link for that group with lower Eocene Acarininapseudotopilensis. [Berggren et al. 2006]
Distinguishing features: Parent taxon (Acarinina): Moderate to low trochospire; chambers ovoid, usually 4-6 in final whorl. Wall muricate with pustules on umbilical shoulders; This taxon: Test anguloconical, tightly coiled with 4½-5 compressed chambers in fine whorl; straight radial sutures on the umbilical side; no muricocarina.
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: Acarininaboudreauxi is distinguished from A. interposita by the much tighter coil and more compressed chambers, and by having straight radial sutures on the umbilical side and an anguloconical test. Acarininaboudreauxi differs from A. punctocarinata by lacking a discontinuous muricocarina and typically being smaller; it differs from A. bullbrooki by its rounded profile and more slowly expanding chambers and the 4½-5 (as opposed to 4) chambers in the final whorl. [Berggren et al. 2006] Morphology: Subcircular planconvex test, coiled in a low trochospiral with 4½ to 5 chambers in the final whorl. Chambers radially compressed and appressed with flat or slightly depressed sutures on a flat spiral side. Aperture umbilical-extraumbilical, a low arch. Ventral sutures straight, radial and depressed converging on a narrow, deep umbilicus. Periphery subacute. [Berggren et al. 2006] Wall type: Robust, heavily calcified, wall with blocky fused muricae. [Berggren et al. 2006] Size: Maximum diameter of holotype 0.28 mm; thickness 0.21 mm. [Berggren et al. 2006]
Character matrix
test outline:
Subcircular
chamber arrangement:
Trochospiral
edge view:
Planoconvex
aperture:
Umbilical-extraumbilical
sp chamber shape:
Crescentic
coiling axis:
Low
periphery:
N/A
aperture border:
N/A
umb chbr shape:
Subtriangular
umbilicus:
Narrow
periph margin shape:
Subangular
accessory apertures:
None
spiral sutures:
Weakly depressed
umb depth:
Deep
wall texture:
Coarsely muricate
shell porosity:
Finely Perforate: 1-2.5µm
umbilical or test sutures:
Moderately depressed
final-whorl chambers:
4.5-5
N.B. These characters are used for advanced search. N/A - not applicable
Biogeography and Palaeobiology
Geographic distributionProbably widespread; currently known only from the Indian Ocean. [Berggren et al. 2006]
Aze et al. 2011 summary: Probably widespread currently only known from Indian Ocean; based on Berggren et al. (2006b) Isotope paleobiologyNo data available. [Berggren et al. 2006] Aze et al. 2011 ecogroup 1 - Open ocean mixed-layer tropical/subtropical, with symbionts; based on comparison with other species of the genus. Phylogenetic relationsPossibly evolved from Acarininapseudotopilensis and was ancestral to A. punctocarinata and A. bullbrooki. [Berggren et al. 2006]
Geological Range: Notes: Ranges from the lower Part of Zone E7 to within Zone E9. [Berggren et al. 2006] Last occurrence (top): within E9 zone (43.23-43.85Ma, top in Lutetian stage). Data source: Eocene Atlas First occurrence (base): in lower part of E7a subzone (20% up, 49.8Ma, in Ypresian stage). Data source: Eocene Atlas
Plot of occurrence data:
Range-bar - range as quoted above, pink interval top occurs in, green interval base occurs in.
Triangles indicate an event for which a precise placement has been suggested.
Grey shading between taxa indicates intergrading species within an anagenetic lineage (data from
Lamyman et al. 2026).
(NB There is no histogram as there are no occurrence records for the taxon in the Neptune database) Parent: Acarinina
Primary source for this page: Berggren et al. 2006 - Eocene Atlas, chap. 9, p. 266
References:
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. gsO
Blow, W. H. (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden. 2: 1-1413. gs
Fleisher, R. L. (1974a). Cenozoic planktonic foraminifera and biostratigraphy, Arabian Sea, Deep Sea Drilling Project, Leg 23A. Initial Reports of the Deep Sea Drilling Project. 23: 1001-1072. gsO
Acarinina boudreauxi compiled by the pforams@mikrotax project teamviewed: 13-7-2026
Eocene_Atlas_pl09-5_fig13-16.jpg
Eocene_Atlas_pl09-5_fig13-16A.jpg
Eocene_Atlas_pl09-5_fig12.jpg
Eocene_Atlas_pl09-5_fig13-16.jpg
Eocene_Atlas_pl09-5_fig13-16A.jpg
Eocene_Atlas_pl09-5_fig12.jpg
holotype: A. boudreauxi
holotype: A. boudreauxi
paratypes: A. boudreauxi
