Tenuitella praegemma Li 1987 from: Pearson, P.N.Olsson, R.K.Hemleben, C.Huber, B.T.Berggren, W.A. (2006): Atlas of Eocene Planktonic Foraminifera. p. 1-513 | . |
Notice: This catalogue page may contain unedited data.
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Species Tenuitella praegemma Li 1987 |
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| Diagnosis / Definition: |
Pearson et al. (2006):
DESCRIPTION.
Type of wall: Microperforate, surface smooth to
finely pustulose, pustules irregularly scattered on
umbilical and spiral sides of test.
Test morphology: Test small, lobate, circular in
equatorial outline, equatorial periphery rounded;
chambers globular, coiled in a low trochospire,
increasing gradually in size, 4-5 in the final whorl,
subcrescentic on spiral side, final chamber may be
narrow, asymmetrical and pendulous; sutures depressed,
curved on the spiral side, radial on umbilical side;
umbilicus narrow, deep; aperture a low extraumbilical-umbilical
arch bordered by a narrow, equidimensional
lip that may extends to the spiral side, and may be
accompanied by a secondary aperture or apertural lip
along the spiral suture.
Size: Holotype maximum diameter: 0.16 mm. |
| Discussion / Comments: |
Pearson et al. (2006):
DISTINGUISHING FEATURES.-
Distinguished
from other tenuitellids by having either a low, interiomarginal aperture that extends from near the
umbilicus to the spiral side or by presence of a low,
narrow extraumbilical aperture accompanied by a
supplementary aperture (or apertural lip) on or near the
peripheral margin of the spiral suture; it further differs
from Tenuitella gemma by having a more lobate
equatorial outline.
DISCUSSION-
The holotype of T. praegemma is reillustrated
on Plate 16.6, Figs. 1-3 along with specimens
from the upper Eocene of the New Jersey coastal margin,
including specimens previously designated as
Globorotalia gemma by Poore and Bybell (1988) (Pl.
16.6, Figs. 4, 5, 14) and P. praegemma forma
pendulocamerata by Poag and Commeau (1 995) (Pl.
16.6, Figs. 15- 19). The very elongate interiomarginal
apertural slit that extends from an extraumbilical position
across the periphery and sometiyes to the spiral side is
a characteristic feature of this species. Some forms are
biapertural (Pl. 16.6, Figs. 1 1, 16, 18) and others show
presence of a secondary apertural lip on the spiral suture
(Pl. 16.6, Figs. 12, 13).
A monolamellar microstructure in T. praegemma
is revealed from SEM observation (Pl. 16.6, Fig.
9) and is also suggested that T. praegemma descended
from T. insolita during the late Eocene. It is also possible
that it descended from T. patefacta since there is greater
similarity in the apertures of praegemma and patefacta
than that of insolita.
STRATIGRAPHIC RANGE.-
Upper Eocene to
lowermost Oligocene; Zones E1 5-01.
GEOGRAPHIC DISTRIBUTION.-
North Atlantic
margin.
STABLE ISOTOPE PALEOBIOLOGY-
Oxygen and
carbon isotope data obtained for T. praegemma (Fig. 16.3) demonstrate that this species has very similar
values as the co-occurring benthic Cibicidoides spp. and
is 1.32‰ more positive in δ 18O and l.32‰ more negative
in δ 13C than the co-occurring planktonic species
Turborotalia ampliapertura. These results suggest that
T. praegemma was a relatively deep dwelling planktoilic
species that either preferred living within the oxygen
minimum zone of the water column or had a considerable
vital effect causing preferential fractionation of the
lighter carbon isotope.
REPOSITORY.-
Holotype and paratypes deposited in
the British Museum of Natural History, London. |
| Systematics: |
35
Ordo Foraminiferida
Superfamilia Globigerinaceae
Familia Cassigerinellidae
Genus Tenuitella
Species Tenuitella praegemma
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| Synonym list: |
Pearson et al. (2006):
1987 Praetenuitella praegemma Li. - Li : p.309 pl. 1; fig. 11-22 [upper Eocene, Zone P15-17, Cocoa Sand, Jackson
Group, Choctaw County, Alabama, and Jackson Group,
Wayne County, Mississippi, USA]
1995 Praetenuitella praegemma Li. - Poag & Commeau : pl. 9; fig. 3-4, 7-10 [upper Eocene,
Zone P15, U. S. Geological Survey Exmore Core,
Virginia Coastal Plain]
2006 Tenuitella praegemma Li. - Pearson et al. : p.494 pl. 16.6; fig. 1-19 (Pl. 16.6, Figs. 1-3: SEMs of holotype of
Praetenuitella praegemma Li)
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| References: |
Li,Q. (1987):
Origin, phylogenetic development and systematic taxonomy of the Tenuitella plexus (Globigerinitidae Globigerininina) . Journal of Foraminiferal Research Vol. 17 p. 298-320
Poag,C.W.. and Commeau,J.A.. (1995):
Paleocene to middle Miocene planktic foraminifera of the southwestern Salisbury Embayment, Virginia and Maryland: biostratigraphy, allostratigraphy, and sequence stratigraphy . Journal of Foraminiferal Research Vol. 25 p. 134-155
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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