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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
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Species Tenuitella praegemma Li 1987



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
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]
1995 Praetenuitella praegemma forma pendulocamerata Poag & Commeau. - Poag & Commeau : p.155 pl. 9; fig. 11-15 [upper Eocene, Zone P1 5, 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)
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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