Acarinina esnehensis Nakkady 1950 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 esnehensis Nakkady 1950 |
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| Diagnosis / Definition: |
Pearson et al. (2006):
DESCRIPTION.
Type of wall: Muricate, with strong
concentration of muricae around umbilicus.
Test morphology: Low- to moderately high
spired trochoid test; 5 (ranging up to 7) inflated chambers
in last whorl, umbilicus open, deep and generally
relatively wide; aperture low slit extending along margin of last chamber towards, but not reaching, periphery;
no circumumbical muricate rim; sutures incised, radial to only slightly curved on umbilical and spiral sides of test; rounded margin(s) in edge view. Size: Relatively large (to 0.5 mm maximum diameter); maximum diameter of holotype: 0.4 mm; thickness: 0.3 mm (Nakkady, 1950, p. 689). |
| Discussion / Comments: |
Pearson et al. (2006):
DISTINGUISHING FEATURES.-
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 capslbridges 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.
DISCUSSION.-
As the description above indicates,
clear distinction between esnehensis and the related taxa
mckannai, soldadoensis and gravelli is difficult to
achieve. Loeblich and Tappan (1 957) expressed the view
that esnehensis and gravelli are synonymous and junior
synonyms of mckannai. As the result of a comparative
examination of type material of these taxa at the British
Museum (Natural History), London and the U.S.
National Museum, Washington, Blow (1 979, p. 11 27-
1128) agreed with the former view but distinguished
esnehensis from mckannai on the basis of the following
characters observable in mckannai: 1) much tighter
coiling mode; 2) more "globigerine" initial coil; 3)
posteriorly recurved (versus consistently radial) and
more clearly incised dorsal intercameral sutures; 4)
ventral intercameral sutures recurved on earlier part of
last whorl to sinuous in the later part of the last whorl in
addition to distinctly different stratigraphic ranges.
At the same time Blow (1979, p. 1129) was
obviously at pains to distinguish consistently between
esnehensis and soldadoensis, concluding that in view
ofthe long stratigraphic persistence of transitional forms
over the biostratigraphic interval of his Zone P5 (midpart)
to Zone P8b "Muricoglobigerina esnehensis (=
M. gravelli) is little more than an environmentally
induced ecophenotype of a basic soldadoensis genotype". Nevertheless, he distinguished the two forms
as separate species as do we here based on the set of distinguishing characters described above.
PHYLOGENETIC RELATIONSHIPS.-
Acarinina esnehensis probably evolved from A. soldadoensis in (lower) Zone P5.
STRATIGRAPHIC RANGE.-
Zones P5 to Zone E6; particularly common in Zone El in association with the PETM excursion fauna in the Bass River section of coastal New Jersey and Egypt.
GEOGRAPHIC DISTIUBUTI0N.-
Widespread from
(sub)tropical areas (Caribbean, New Jersey, Egypt) to
austral (Hornibroook, 1958) and boreal (Berggrcn,
1960a) regions. Probably lumped with A. soldadoensis
in some studies and thus an understanding of its real
distribution remains muted.
STABLE ISOTOPE PALEOBIOL0GY.-
No data available.
REPOSITORY.-
Holotype and paratypes deposited in
the micropaleontological collections of The Natural
History Museum, London. |
| Systematics: |
35
Ordo Foraminiferida
Superfamilia Globigerinaceae
Familia Truncorotaloididae
Genus Acarinina
Species Acarinina esnehensis
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| Synonym list: |
Pearson et al. (2006):
1952 Globigerina gravelli Brönnimann. - Brönnimann : p.12 pl. 1; fig. 16-18 [Zone P5, lower zone of Lizard Springs Fm.,
Guayaguayare area, South Trinidad]
1957 Globigerina gravelli Brönnimann. - Bolli : p.72 pl. 16; fig. 1-3 [Globorotalia formosa Zone, upper Lizard Springs Fm., Trinidad]
1958 Globigerina gravelli Brönnimann. - Hornibrook : p.21 fig. 21, 25 [uppermost Paleocene, Waipawan Stage, New
Zealand]
1960 Globigerina mckannai White. - Berggren : p.68 pl. 1, fig. 4a-c;
pl. 9, fig. 3a-c [lower Eocene Zone P7, Clay Quany at Hollbecker Berg, north-west Germany];
pl. 9, fig. 2a-c [lower Eocene Zone P7, Clay Quarry at Bessenbecker Berg , north-west Germany];
pl. 9, fig. 4ac;
pl. 10, fig. l a-c, text-fig. 7 [lower Eocene Zone P7, Rosnaes Clay, Rogle Klint, Denmark] [Not White, 1928]
1979 Muricoglobigerina esnehensis Nakkady. - Blow : p.1127 pl. 109; fig. 1-7 [Zone P6 of Blow, 1979;
DSDP 6147.21814, 78-81 cm; Shatsky Rise, northwest
Pacific Ocean]
non 1993 Muricoglobigerina esnehensis Nakkady. - Pearson et al. : pl. 1; fig. 20 [middle Eocene Zone P1 1 -P 12,
DSDP Site 523, Walvis Ridge, South Atlantic Ocean];
(=Acarinina pseudosubsphaerica n. sp.)
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| References: |
Nakkady,S.E. (1950):
A new foraminiferal fauna from the Esna shales and Upper Cretaceous chalk of Egypt . Journal of Paleontology Vol. 24 p. 675-692
Brönnimann,P. (1952):
Trinidad Paleocene and lower Eocene Globigerinidae . Bulletins of American paleontology Vol. 34(143) p. 1-34
Haque,A.F.M.M. (1956):
The Foraminifera of the Ranikot and the Laki of the Nammal Gorge, Salt Range. Pakistan Geological Survey . Paleontologia Pakistanica Vol. 1 p. 1-300
Bolli,H.M. (1957):
The genera Globigerina and Globorotalia in the Paleocene-Lower Eocene Lizard Springs Formation of Trinidad, B.W.I . Bulletin of the U.S. National Museum Vol. 215 p. 61-82
Hornibrook,N.B. (1958):
New Zealand foraminifera: key species in stratigraphy, no. 6 . N.Z.J. Geol. Geophys. Vol. 1
Berggren,W.A. (1960):
Some planktonic Foraminifera from the Lower Eocene (Ypresian) of Denmark and northwestern Germany . Stockholm Contribution in Geology Vol. 5 p. 41-108
Blow,W.H. (1979):
The Cainozoic Globigerinida. 3 Vols p. 1413 pp
Pearson,P.N.; Shackleton,N.J. and Hall,M.A. (1993):
The Stable Isotope Paleoecology of Middle Eocene Planktonic Foraminifera and Multi-species integrated Isotope Stratigraphy . Journal of Foraminiferal Research Vol. 23 p. 123-140
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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