Classification: pf_cenozoic -> muricate non-spinose -> Truncorotaloididae -> Acarinina
Sister taxa: Acarinina, Astrorotalia, Igorina, Morozovella, Morozovelloides, Planorotalites, Praemurica,
Daughter taxa (blue => in age window 0-300Ma)
soldadoensis group
Differs from A. collactea by its smaller size and smaller, often indistinct aperture; differs from A. echinata by absence of a bulla and by presence of an umbilicus; differs from
Dipsidripella danvillensis (Howe and Wallace) in presence of a bilamellar, rather than monolamellar, wall and more densely muricate surface ornamentation.
This taxon is distinguished by its small size (~0.25-0.30 mm in maximum diameter), 5-chambered and compact (involute) test. Acarinina medizzai is morphologically similar to, and probably descended from, A. collactea. The moderately muricate medizzai may be distinguished from collactea in having a smaller (generally less than 0.2 mm in diameter), lower trochospiral test and more restricted aperture.
Compact, strongly muricate test with 5 globular, inflated chambers in last whorl.
This taxon is distinguished by its large and widely open umbilicus and high but variable number (6-8; rarely to 10) of chambers in the last whorl.
Characterized by its compact coiling, muricate surface texture, and presence of a kummerform or bullate final chamber and/ or sutural bullae. Differs from Acarinina medizzai by lacking a visible umbilicus and presence of kummerform or bullate final chamber.
Acarinina pseudosubsphaerica n. sp. is distinguished from all other middle Eocene acarininids by its high spire, small size and subspherical shape. It is similar in morphology to the Paleocene species, A. subsphaerica (Subbotina), but differs from that form and A. alticonica Fleisher by having less closely appressed chambers and a broader umbilicus.
This form is distinguished by its strongly muricate test with a high trochospire and closely appressed, angular chambers. It is distinguished from A. subsphaerica and A. pseudosubsphaerica n. sp. by having more compressed, angular chambers and a less high-spired test.
Low trochoid, moderately evolute test of 4-5, moderately to strongly muricate, rounded chambers distinctly elongated in the axis of coiling; final chamber often reduced in size; lobulate periphery; deep and relatively wide umbilicus revealing (in some individuals) earlier chambers and their arcuate foramina; sutures on spiral side deep and curved and/or tangential in direction of coiling, chambers often overlapping.
This taxon is distinguished by its 4-4½ chambers (in the final whorl), planoconvex, distinctly muricate, test with umbilically inflated (globular) chambers; umbilical side of test distinctly inflated, accompanied by loose arrangement of chambers resulting in scalloped, lobulate peripheral margin.
This form is distinguished by its combination of subtriangular to wedge-shaped (cuneiform) and lunate chambers, tendency to develop laterally angulate and peripherally disjunct terminal chambers, widely open umbilicus, and densely muricate umbilical side and only weakly muricate spiral side.
The diagnostic features of Acarinina angulosa are the strongly angular disposition of the chambers of the last whorl and the strongly lobulate peripheral outline.
Acarinina africana is distinguished from A. sibaiyaensis by its axially-compressed test, strongly lobulate peripheral margin, and manner in which its chambers change ontogenetically from globular to more lenticular shapes.
Diagnostic characteristics are the relatively large (5-9) number of chambers in final whorl, and the test coiled in a very low trochospiral (approaching planispiral) mode.
This taxon is characterized by a muricate test of 5-6 (rarely 7) chambers arranged in a relatively loose (lax) coil resulting in an open and deep umbilicus, and moderate to strong lateral chamber compression (giving a subangulate appearance to the peripheral margin of some chambers). Muricae are well developed on the umbilical side but only weakly expressed (blunted) on the spiral side, the test being strongly cancellate. A small, weakly muricate chamber usually caps/bridges the junction between the first and last chambers of the final whorl and on the spiral side a smooth, virtually imperforate band (which appears to be a consistent distinguishing characteristic of this taxon) runs along the lower part of this diminutive chamber. This taxon is distinguished from Acarinina soldadoensis by having a greater number (5-7 vs 4) of globular (as opposed to tangentially elongate) chambers in the final whorl, straighter, radial sutures on both sides of the (generally higher spired) test and a larger, deeper umbilicus.
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.
This species is characterized by its strongly elevated spire and the tightly coiled, small test which gives it a sphaerical, globular shape. The umbilicus is narrow and deep and is surrounded by coarse pustules (muricae). Specimens usually have a diminutive final chamber with an arched aperture.
esnaensis-wilcoxensis group
Acarinina bullbrooki is distinguished by its (sub)quadrate test, closely appressed and embracing chambers, rounded to subangular periphery, and weak to moderate murical concentration on the periphery. It differs from A. praetopilensis and related forms in having less incised sutures, generally smaller muricae, and by populations generally being approximately randomly coiled.
This taxon is distinguished from bullbrooki in the tangential elongation of its chambers (giving the test a semi- rectangular vs. (sub)quadrate shape), development of wedge-shaped chambers on the umbilical side, generally more angulo-conical umbilical profile and distinct punctate pseudocarina formed by peripheral concentration of blunt, thick muricae.
Acarinina boudreauxi 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. Acarinina boudreauxi 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.
Acarinina rohri is distinguished by its strongly muricate test, particularly the concentration of muricae on the umbilical shoulders, and around the peripheral margin, the tendency to develop disjunct separation of chambers in stratigraphically younger forms and by the development of raised imperforate rims surrounding supplementary apertures on the later chambers on the spiral side.
Distinguished by its distinctly inflated, anguloconical, ‘truncorotaloid’ chambers and strongly compressed, angulate and disjunct (ante)penultimate chamber(s) rimmed by thick, blunt circum-cameral muricocarinae and sutural “supplementary” apertures on spiral side.
Distinguished by its strongly muricate, subquadrate test, disjunct, cuneate to mitriform last chamber which bears heavy circum-peripheral concentration of partially fused muricae.
Acarinina mcgowrani n.sp. is closely related to the middle Eocene species A. praetopilensis and the early Eocene species A. pseudotopilensis. It is distinguished from both species by its more compact test, which is densely muricate, and by having more incised sutures. Unlike A. praetopilensis it does not show circum-cameral fusion of muricae into an incipient circum-cameral muricocarina, and the chamber periphery is usually more rounded. The muricae are typically more conical than in other acarininids and long, slender muricae intrude into the sutures and fringe the primary and supplementary apertures. Sutures are distinct and deeply incised on both the umbilical and spiral sides, a feature that distinguishes the pseudotopilensismcgowranipraetopilensis lineage from the co-occurring Acarinina bullbrooki group. Small bullae are frequently present (see holotype), and are more common than in most other acarininids.
Distinguished from Acarinina esnaensis and A. wilcoxensis by its triangular to wedge- or cuneate-shaped chambers in the final whorl, disjunct (separation of) chamber margins and more densely muricate wall; from A. quetra by its less anguloconical test and lack of muricocarina.
This taxon is distinguished by its angular test whose chambers are loosely disposed sequentially to each other at ~ 90° and with a distinct, but discontinuous, peripheral muricocarina.
This taxon is distinguished by its (sub)quadrate, 4-chambered (in the final whorl), planoconvex, distinctly muricate, test with subrounded to (later) subacute axial outline.
This taxon is distinguished by its generally elongate-oval shape, with 4 rounded to subangulate, closely appressed, embracing chambers in the final whorl, narrow umbilicus, with the later chambers on the spiral side tangentially longer than radially broad.
Distinguished by triangular (broadly wedge-shaped) chambers; asymmetrically situated aperture resulting in distinct projection of umbilical face of last chamber over the umbilicus. Acarinina coalingensis has more rounded, inflated chambers than A. primitiva and lacks the straight, incised intercameral sutures on the umbilical side.
Robust test, 3-4 chambered final whorl, compact, subquadrate (primitiva morphotype) to subtriangular (coalingensis morphotype), strongly and bluntly muricate test; peripheral margin broadly rounded, less commonly subangular in edge view; chambers are arranged at distinct right angles to each other and usually separated by deep, incised sutures (particularly between preantepenultimate and antepenultimate chambers) on umbilical side, and increase rapidly in size; aperture interiomarginal, umbilical-extraumbilical.
Compact, small, trochospiral, subcircular to subquadrate test with 4 (rarely 5) rounded, tightly packed, radially compressd and axially elongate chambers; early whorls raised above surface of last whorl; surface moderately muricate, particularly on umbilical side, with deep, funnel-shaped entrances to the pores.
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.
Specimens which cannot be assigned to established species


Citation: Acarinina Subbotina, 1953
Rank: Genus
Type species: Acarinina acarinata Subbotina, 1953 (=junior subjective synonym of Globigerina nitida Martin, 1943; see Olsson and others, 1999).
Taxonomic discussion: The genus Acarinina was erected by Subbotina (1953) to include Paleogene taxa exhibiting morphologic features intermediate between Globigerina and Globorotalia, such as species with rounded chambers, spinose (muricate) test, and an umbilical-extraumbilical aperture. Three groups were originally distinguished:
1. Acarininids with angular chambers (e.g., A. crassaformis);
2. Acarininids with rounded chambers (e.g., A. acarinata);
3. Intermediate acarininids (e.g., A. conicotruncata).
Subsequent authors have questioned the inherent morphological homogeneity of this group by considering Acarinina to be a synonym for taxa as phylogenetically distinct as Turborotalia and Globorotalia. As conceived herein, Acarinina is characterized by rounded to subangular, unkeeled chambers that are covered with coarse pustules (muricae), which become dense, enlarged, and spike-like on the umbilical surface around the aperture. The heavy growth of pustules form deep funnel-shaped entrances to the pores and may also partially or completely close the pores. In Paleocene forms, the aperture has a very thin lip or none at all. [Olsson et al. 1999]

A particular issue of discussion within the Working Group has been the status of the genus Truncorotaloides. Blow (1979, p. 1033-1034) gave a comprehensive overview of the morpho- and phylogenetic trends which he viewed as definitive in delineating the genus Truncorotaloides and its differentiation from Acarinina. Primary among these was the development of “raised, imperforate (in the sense that normal mural-pores are absent), non-muricate narrow areas of test material usually around the distal (outer) margins of the sutural margins adjacent to the supplementary apertures”. These true supplementary apertures were considered functional in life for the extrusion of protoplasm in much the same manner as among the species of modern Globigerinoides. The dorsal/spiral apertures seen on Acarinina were considered as secondary openings (lacking raised imperforate rims) formed by late stage calcification over previously calcified strongly muricate edges leaving apparent “gaps” in the chamber junctions. Other important aspects of the Truncorotaloides stage of evolution included: lateral angulation of the chambers; in advanced (end) members strongly disjunct chambers that bear circumcameral muricocarinae.
Blow (1979, p. 1034) recognized three lineages in which these morphogenetic trends were said to have been iteratively produced:
1) Truncorotaloides quetra (evolved from Acarinina pseudotopilensis) in his Zone P7 (=Zone E4 of this
2). Truncorotaloides rohri s.l (supposedly evolved from Acarinina bullbrooki via the Acarinina pseudodubia-
piparoensis group in Zone E10/11);
3). Truncorotaloides topilensis (evolved from Acarinina praetopilensis in uppermost Zone E7).
While we agree with Blow (1979) on the potential significance of supplementary apertures as adaptive features, and agree that in principle they might be used to delimit genera (as in Neogene Globigerinoides) we cannot sustain his generic concept of Truncorotaloides because it is demonstrably polyphyletic on Blow’s original terms and also according to the modified phylogeny presented here. To recognize rohri in a monospecific Truncorotaloides would also compel us to name a new genus for quetra, which seems unnecessary. Similarly, Blow (1979) included various globular forms in his genus Muricoglobigerina that are not closely related according to our researches; hence his concept of that genus is not workable either.
With regard to the validity of the Family Truncorotaloididae Loeblich and Tappan, 1961, the International Code of Zoological Nomenclature, Chapter 8, Article 39 states that the family name is invalid only in cases of homonymy or if the type species is found to be invalid. In this case Article 40 applies: “When the name of a type genus of a nominal family-group taxon is considered to be a junior synonym of the name of another nominal genus, the family-group name is not to be replaced on that account alone”. The description of the family remains that of the Truncorotaloididae. [Berggren et al. 2006]

Catalog entries: Acarinina;

Type images:

Short diagnosis: Test, a moderate to low trochospire; chambers ovoid shaped, generally with 4-6 chambers in final whorl, occasionally 7 or more; wall moderately to strongly muricate with moderate to strong pustule growth on umbilical shoulders surrounding aperture; aperture interiomarginal, umbilical-extraumbilical, with or without thin 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.


Diagnostic characters: Test, a moderate to low trochospire; chambers ovoid shaped, generally with 4-6 chambers in final whorl, occasionally 7 or more; wall moderately to strongly muricate with moderate to strong pustule growth on umbilical shoulders surrounding aperture; aperture interiomarginal, umbilical-extraumbilical, with or without thin lip. [Olsson et al. 1999]

Biogeography and Palaeobiology

Most likely ancestor: Morozovella - at confidence level 0 (out of 5). Data source: Olsson et al. 1999.

Biostratigraphic distribution

Geological Range:
Last occurrence (top): in lower part of Rupelian Stage (31% up, 32.1Ma, in Rupelian stage). Data source: Total of range of species in this database
First occurrence (base): near top of Danian Stage (85% up, 62.3Ma, in Danian stage). Data source: Total of range of species in this database

Plot of occurrence data:

Primary source for this page: Berggren et al. 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 9, p. 261


Berggren, W.A.; Pearson, P.N.; Huber, B.T. & Wade, B.S., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Acarinina. In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Allen Press, Lawrence, Kansas, pp. 257-326.

Bermudez 1953 [sorry, not in our bibliography yet]

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, 1413 pp.

Jenkins, D.G., (1965). A re-examination of Globorotalia collactea Finlay, 1939. New Zealand Journal of Geology and Geophysics, 8: 843-848.

Jenkins, D.G., (1965). Planktonic Foraminiferal zones and new taxa from the Danian to lower Miocene of New Zealand. New Zealand Journal of Geology and Geophysics, 8(6): 1088-1126.

Loeblich, A.R., Jr. & Tappan, H., (1961). Cretaceous planktonic foraminifera: Part I-Cenomanian. Micropaleontology, 7: 257-304.

Martin, L.T., (1943). Eocene foraminifera from the type Lodo Formation, Fresno County, California. Stanford University Publications, University Series, Geological Sciences, 3. Stanford University Press, Stanford University, CA, 1-35 pp.

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.

Subbotina, N., (1953). Foraminiferes fossiles d'URSS Globigerinidae, Globorotaliidae, Hantkeninidae. Bureau de Recherches Geologiques et Minieres, 2239: 1-144.


Acarinina compiled by the pforams@mikrotax project team viewed: 23-1-2018

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