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Acarinina interposita Subbotina 1953 from: Pearson, P.N.Olsson, R.K.Hemleben, C.Huber, B.T.Berggren, W.A. (2006): Atlas of Eocene Planktonic Foraminifera. p. 1-513
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Species Acarinina interposita Subbotina 1953



Diagnosis / Definition:
Pearson et al. (2006):
DESCRIPTION.- Type ofwall: Densely muricate on both sides, non-spinose; normal perforate. Test morphology: Low-trochospiral; relatively large, robust, test with embracing, appressed chambers; planoconvex, weakly lobate, circular outline, rounded periphery in edge view; 4-4 1/2 chambers in final whorl, increasing slowly in size, generally globular; sutures depressed, radial, weakly curved; muricae more strongly developed on umbilical than on spiral side, short, thick muricae concentrated around umbilicus, which is narrow, deep; about 10- 12 chambers in 2-3 whorls on spiral side; early chambers obscured by muricate texture, chambers of final whorl increasing slowly in size, essentially equidimensional; sutures radial, straight, only slightly depressed; muricae tend to concentrate along peripheral margin; in edge view planoconvex; profile of early chambers rounded, with flattening of ante- and/or penultimate chamber resulting in rounded margin; peripheral margin; aperture an umbilical-extraumbilical arch, bordered by thin lip, extending almost to peripheral margin. Size: Diameter 0.35-0.55 mm, thickness 0.20- 0.25 mm.
Discussion / Comments:
Pearson et al. (2006):
DISTINGUISHING FEATURES.- This taxon is distinguished by its 4-4 1/2 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. DISCUSSION.- This distinctly inflated (globular) form is characteristic of lower Eocene assemblages; it is predominantly dextrally coiled throughout its range. We have observed it to appear in Zone E4 in Egypt and to grade into A. pentacamerata at stratigraphically higher/ younger levels. We question the high latitude records of forms cited under this name (see synonymy listing above); they do not appear to display the robust, inflated morphology characteristic of low latitude representatives, and indeed some of the forms are recorded from distinctly lower stratigraphic levels (Zone AP5 [which approximately correlates with Zone E21) and contain only 3 chambers in the final whorl (Lu and Keller, 1993). PHYLOGENETIC RELATIONSHIPS.- This taxon seems to have been derived from A. soldadoensis and evolved into A. pentacamerata by an increase in the number of chambers in the whorl and a change in the spire height. STRATIGRAPHIC RANGE.- Zone E4 to Zone E6. GEOGRAPHIC DISTRIBUTION.- Occurs commonly in the Tethys (Egypt) and in the northern Caucasus. STABLE ISOTOPE PALEOBIOL0GY.- No data available.
Systematics:

35
 Ordo Foraminiferida
  Superfamilia Globigerinaceae
   Familia Truncorotaloididae
    Genus Acarinina
     Species Acarinina interposita
Synonym list:
Pearson et al. (2006):
1953 Acarinina interposita Subbotina. - Subbotina : p.231 pl. 23, fig. 6a-c [holotype, lower Eocene Zone of conical globorotaliids, Khieu River section, Nal'chik region, northern Caucasus]; fig. 7a-c [lower Eocene Zone of conical globorotaliids, Kuban River section, northern Caucasus]
1979 Globorotalia (Acarinina) interposita Subbotina. - Blow : p. 931-933 pl. 156; fig. 7-9 [Zone P10, piston core Kane 9-C, North Atlantic Ocean]
1988 Acarinina interposita Subbotina. - Krasheninnikov et al. : p.96 pl. 8; fig. 4-6 [G. aragonensis Zone, DSDP Site 277, Campbell Plateau]
? 1990 Acarinina interposita Subbotina. - Stott & Kennett : p.559 pl. 6; fig. 3, 4 [Zone AP9, ODP Hole 689B, Maud Rise, southern South Atlantic Ocean]
? 1991 Acarinina interposita Subbotina. - Huber : p.439 pl. 2; fig. 13-15 [Zone AP7, ODP Site 738, Kerguelen Plateau, southern Indian Ocean]
? 1993 Acarinina interposita Subbotina. - Lu & Keller : p.119 pl. 2; fig. 9, 11 [Zone AP5, ODP Hole 738C, Kerguelen Plateau, southern Indian Ocean]
2006 Acarinina interposita Subbotina. - Pearson et al. : p.285 pl. 9.11; fig. 13-19 (Pl. 9.1 1, Figs. 13-15: new SEMs of paratype of Acarinina interposita Subbotina)
Specimen:
VNIGRI collections, St. Petersburg, Inventory number: 4140
VNIGRI collections, St. Petersburg, Inventory number: 4141
References:

Subbotina,N.N. (1953):
Iskopaemye foraminifery SSSR (Globigerinidy, Khantkenininidy i Globorotaliidy) . Trudy Vsesoyznogo Nauchno-Issledovatel'skogo Geologo-razvedochnogo Instituta (VNIGRI) Vol. 76 p. 296

Blow,W.H. (1979):
The Cainozoic Globigerinida. 3 Vols p. 1413 pp

Krasheninnikov,V.A.; Serova,M.Y.A.. and Basov,I.A. (1988):
Stratigrafiya I planktonnyic foraminiferyi paleogena: vyisokikh shirot Tikhogo okeana . Akademiya Nauk SSSR, Trudy Vol. 429 p. 120

Stott,L.D. and Kennett,J.P. (1990):
Antarctic Paleogene planktonic foraminifer biostratigraphy: ODP Leg 113, Sites 689 and 690.
In: Proceedings of the Ocean Drilling Program Vol. 113 p. 549-569

Huber,B.T. (1991):
Paleogene and early Neogene planktonic foraminifer biostratigraphy of Sites 738 and 744, Kerguelen Plateau (southern Indian Ocean).
In: Proceedings of the Ocean Drilling Program, Scientific Results Vol. 119 Eds: Leckie, R.M.Sigurdsson, H.Acton, G.D.Draper, G. p. 427-449

Lu,G. and Keller,G. (1993):
The Paleocene-Eocene Transition in the Antarctic Indian Ocean: Inference from Planktic Foraminifera . Marine Micropaleontology Vol. 21 p. 101-142

Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006):
Atlas of Eocene Planktonic Foraminifera. p. 1-513

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