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Species Dentoglobigerina pseudovenezuelana Blow & Banner 1962 | ||||||
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| Diagnosis / Definition: | ||||||
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Pearson et al. (2006): DESCRIPTION. Type of wall: Cancellate, normal perforate, nonspinose, Globoquadrina-type wall texture. Test morphology: Test trochospiral, compact, globular, subcircular to subquadrate in outline, chambers ovoid; in spiral view 3 1/2 ovoid chambers in ultimate whorl, increasing moderately in size, sutures moderately depressed, straight; in umbilical view 3-3 1/2 ovoid chambers increasing moderately in size, sutures deeply depressed, straight, umbilicus moderate in size, sometimes overlapped by ultimate chamber, aperture centered over the umbilicus, bordered by a thin irregular, subtriangular-shaped lip that projects over the umbilicus, pustules are concentrated in the apertural area; in edge view chambers ovoid in shape, embracing, ultimate chamber extends over the umbilicus, oval to subcircular in outline. Size: Maximum diameter of holotype 0.5 1 mm, thickness 0.34 mm. |
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| Discussion / Comments: | ||||||
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Spezzaferri & Silva (1990): Very rare. Pearson et al. (2006): DISTINGUISHING FEATURES.- The species is characterized by its compact, subcircular to subquadrate test, embracing chambers, and umbilically centered aperture that is bordered by an irregular, subtriangular-shaped lip that projects over the umbilicus, and concentration of pustules in the apertural area. Its test is more compact and the chambers are more flattened than in D. galavisi. Note that the holotype is slightly aberrant in having a final chamber that is about the same size as the penultimate chamber. More regular specimens with proportionally large final chambers are more globular in shape (see Plate 13.2). DISCUSSION.- Blow (1 979) included pseudovenezuelana in his new genus Dentoglobigerina and noted that the increased appression and embrace of the chambers in the ultimate whorl of pseudovenezuelana leads to a test whose equatorial outline becomes less lobulate and more circular. He derived D. pseudovenezuelana from Dentoglobigerina yeguaensis (=Subbotina yeguaensis) and, in turn, derived yeguaensis from D. galavisi (= Globoquadvina galavisi), based essentially on middle Eocene morphotypes identified by him as galavisi. As noted above in the discussion of G. galavisi, he based his conclusion on a concept of a "central type" for galavisi that differs considerably from the holotype. Having derived yeguaensis from galavisi, it appears that yeguaensis was chosen as the ancestor of pseudovenezuelana. This scenario is rejected because yeguaensis is a spinose subbotinid. It is more likely that D. pseudovenezuelana evolved from D. galavisi, in an evolutionary transition that partially mirrored the earlier origin of Dentoglobigerina tripartita from D. galavisi. PHYLOGENETIC RELATIONSHIPS.- Dentoglobigerina pseudovenezelelana evolved from D. galavisi in the middle/late Eocene by developing more embracing chambers, which led to a compact, subcircular or subquadrate test. STRATIGRAPHIC RANGE.- Zone E14 to Zone 05? (=P2 l b). GEOGRAPHIC DISTRIBUTION.- Known only from a few low latitude locations. STABLE ISOTOPE PALEOBI0LOGY.- Recorded by Poore and Matthews (1984) and Pearson and others (200 1) with relatively positive ò18O and negative ò13C indicating a deep planktonic habitat. |
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| Systematics: | ||||||
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22 Genus Dentoglobigerina Species Dentoglobigerina pseudovenezuelana 35 Ordo Foraminiferida Superfamilia Globigerinaceae Familia Globoquadrinidae Genus Dentoglobigerina Species Dentoglobigerina pseudovenezuelana |
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| Synonym list: | ||||||
| Spezzaferri & Silva (1990): 1957 Globigerina venezuelana Hedberg. - Bolli :
1962 Globigerina venezuelana Hedberg. - Blow & Banner : pl. XI; fig. J-L, N, O
1990 Dentoglobigerina pseudovenezuelana Blow & Banner. - Spezzaferri & Silva : p.240 pl. III; fig. 5a-b
Pearson et al. (2006): 1962 Globigerina yeguaensis pseudovenezuelana Blow & Banner. - Blow & Banner : p.100 pl. 11, fig. S-L (holotype)[upper Eocene
Cribrohantkenina danvillensis Zone, Lindi area, Tanzania];
fig. N, O (paratype)[lower Oligocene Globigerina oligocaenica Zone O1, Lindi Area, Tanzania,
Sample FCRM 1965]
1969 Globigerina pseudovenezuelana Blow & Banner. - Blow : p.321 pl. 19; fig. 1, 2 [upper Eocene Zone E15/16,
Lindi area, Tanzania]
1979 Dentoglobigerina pseudovenezuelana Blow & Banner. - Blow : p.1307 pl. 244; fig. 5, 6 [upper Eocene Zone
E 15/16, Lindi area, Tanzania]
1985 Globigerina pseudovenezuelana Blow & Banner. - Bolli & Saunders : p.180 fig. 13.22a-c (reillustration of holotype)
non 1991 Dentoglobigerina pseudovenezuelana Blow & Banner. - Spezzaferri & Premoli Silva : p.243 pl. 3; fig. 5a, b
2006 Dentoglobigerina pseudovenezuelana Blow & Banner. - Pearson et al. : p.407 pl. 13.2; fig. 1-16 (Pl. 13.2, Figs. 1-5: new SFMs of holotype of
Globigerina yeguaensis pseudovenezuelana Blow and
Banner)
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| Specimen: | ||||||
| Natural History Museum, London, Inventory number: P.44524 Natural History Museum, London, Inventory number: P.44526 |
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| References: | ||||||
Bolli,H.M. (1957): Blow,W.H. and Banner,F.T. (1962): Blow,W.H. (1969): Blow,W.H. (1979): Bolli,H.M. and Saunders,J.B. (1985): Spezzaferri,S. and Silva,I.S.. (1990): Spezzaferri,S. and Premoli Silva,I. (1991): Pearson,P.N.; Olsson,R.K.; Hemleben,C.; Huber,B.T. and Berggren,W.A. (2006): |
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| Anonymous: Unedited TaxonConcept data | ||||||
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