Dentoglobigerina tripartita Koch 1926 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 Dentoglobigerina tripartita Koch 1926 |
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| Diagnosis / Definition: |
Pearson et al. (2006):
DESCRIPTION.-
Type of wall: Cancellate, normal perforate, nonspinose,
Globoquadrina-type wall texture.
Test moyphology: Test trochospiral, compact,
globular, subcircular to subquadrate in outline, chambers
ovoid; in spiral view 3-3 ovoid chambers in ultimate
whorl, increasing rapidly in size, ultimate chamber often
a low, elongate oval shape ("cap-like") that projects or
hangs over the umbilicus, sutures moderately depressed,
slightly curved; in umbilical view 3-3 1/2 ovoid chambers increasing rapidly 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; in edge view oval in outline, chambers ovoid
in shape, embracing, ultimate chamber extends over the
umbilicus,.
Size: Maximum diameter of holotype 0.47 mm,
thickness 0.42 mm. |
| Discussion / Comments: |
Pearson et al. (2006):
DISTINGUISHING FEATURES.-
The species is
characterized by its compact, subcircular to subquadrate
test, embracing chambers, a cap-like ultimate chamber
that extends over the umbilicus, and an umbilically
centered aperture that is bordered by an irregular,
subtriangular-shaped lip that projects over the umbilicus.
DISCUSSION.- Blow (1979) included tripartita in a
group of related taxa that he derived from galavisi in
his new genus Dentoglobigerina. He characterized (p.
1310) the development of D. tripartita from D. galavisi "by increasing tightness of the trochospiral coiling-mode,
increasing tangential lengthening of the later chambers
combined with some increased degree of appression of
these ontogenetically later chambers". Blow and Banner
(1962) refigured the holotype of Globigerina bulloides
var. tripartita (here reproduced on Pl. 13.3, Figs. 1-3)
and noted that the ultimate chamber was "misshapen" .
In their study of populations of this taxon they noted (p.
97) "large numbers of specimens with aborted end-
chambers. These aborted final chambers usually retain
their normal position in the progression of the spire but
reduced in volume, are variable in shape....". The
Use of the term "misshapen" applied to the holotype of
tripartita apparently was referring to what they regarded
as an aborted end-chamber. Blow (1979) later added
(p. 1311) 'the last chamber is somewhat deformed and
mishapen". Blow and Banner (1962) and Blow (1979) selected specimens (here reproduced on Pl. 13.3, Figs.
5,6) that they believed showed normal last chambers. It
is now well known that during the adult and
gametogenetic stages of the life cycle of modern
planktonic foraminifera the final chamber may be
reduced in size and variable in shape, but is not aborted.
In the case of D. tripartita the final chamber of the
holotype would appear to be a full expression of the
morphology of this taxon. The final chamber has a caplike
shape and projects over or hangs over the umbilicus.
Specimens with a similar although somewhat less
extreme morphology are shown on Plate 13.3, Figs. 4
and 15. Other specimens on Plate 13.3 compare with
Blow and Banner's and Blow's concept of this taxon.
Figure 13 on Plate 13.3 illustrates a specimen with a
reduced final chamber, the so-called "aborted end-chamber".
Blow (1969) suggested that D. tripartita was
the ancestor of a number of important Oligocene and
lower Miocene species. Fleisher (1974) referred
tripartita to the genus Globoquadrina because he
regarded it as ultimately ancestral to the type species of
the genus, Globoquadrina dehiscens (Chapman, Parr and
Collins). Blow (1979) placed tripartita in
Dentoglobigerina in a lineage leading to
Dentoglohigerina praedehiscens (Blow and Banner) and
then to Globoquadrina dehiscens Finlay. Kennett and
Srinivasan (1 983) rejected Blow's placement of tripartita
in Dentoglobigerina because they believed that there
were two distinct lineages, one leading to G. dehiscens
and the other to D. altispira (Cushman and Jarvis). They
placed tripartita in the Globoquadrina lineage but they
were uncertain of the taxonomic status of this taxon,
grouping it with G. sellii (Borsetti), written as Gq.
tripartita/sellii (p. 178). However, Bolli and Saunders
(1985) clearly separated the two species as
morphologically distinct taxa. The Globoquadrina
lineage according to Kennett and Srinivasan began with
Gq. tripartita/sellii, but no indication was made of an
ancestor species. As discussed above the ancestor species
is D. galavisi and we agree that there may be two separate lineages, as partly outlined by Kennett and Srinivasan
and followed by Spezzaferri (1994), but we accept
Blow's placement of tripartita in Dentoglobigerina
because it lacks the distinctive morphology exemplified
in Globoquadrina.
PHYLOGENETIC RELATIONSHIPS.-
Dentoglobigerina
tripartita developed from D. galavisi by the
development of more embracing, elongate ovoid
chambers and, in some specimens, a cap-like final
chamber that overhangs the umbilicus in adult
specimens.
STRATIGRAPHIC RANGE.-
Zone E13? to Zone 06
(=P22). Banner and Blow (1962) and Fleisher (1974)
suggested that the first occurrence of tripartita was in
the Truncorotaloides rohri Zone and Zone P14
respectively, which correlate to Zone E13 of this study.
Pearson and others (2001) also recorded it from this level
in the upper part of the middle Eocene of Tanzania and
the Adriatic Sea. According to Spezzaferri (1994), the
species persists into the lower Miocene.
GEOGRAPHIC DISTRIBUTION.-
Known from low
and mid latitude locations.
STABLE ISOTOPE PALEOBIOLOGY.-
Oligocene
specimens from ODP Hole 758A registered among the
heaviest ò18O of planktonic assemblages indicating a
deep habitat, although earliest Oligocene specimens may
have had a shallower water preference (Van Eijden and
Ganssen, 1995). |
| Systematics: |
35
Ordo Foraminiferida
Superfamilia Globigerinaceae
Familia Globoquadrinidae
Genus Dentoglobigerina
Species Dentoglobigerina tripartita
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| Synonym list: |
Pearson et al. (2006):
1962 Globigerina tripartita Koch. - Blow & Banner : p.96 pl. 10; fig. A-C (reillustration of holotype), fig. D-F [upper Eocene Cribrohantkenina danvillensis Zone,
Sample FRCM 1923, Lindi area, Tanzania]
1969 Globigerina tripartita Koch. - Blow : p.322 pl. 16; fig. 6 [upper Eocene Zone El4, Sample FRCM 1645, Lindi,
Tanzania]
1979 Dentoglobigerina tripartita Koch. - Blow : p.1310 pl. 244; fig. 3, 4 [upper Eocene Zone E15/16, Sample FCRM 1923, Lindi, Tanzania]
1985 Globigerina tripartita Koch. - Bolli & Saunders : p.181 fig. 14.13a-c (reillustration of holotype by Blow and Banner,
1962, pl. 10, figs. A-C)
2006 Dentoglobigerina tripartita Koch. - Pearson et al. : p.409 pl. 13.3; fig. 1-16 (Pl. 13.3, Figs. 1-3; reillustration of holotype of
Globigerina bulloides var. tripartita Koch)
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| Specimen: |
National Museum of Natural History, Basel, Inventory number: slide 59
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| References: |
Koch,R. (1926):
Mitteltertiäre aus Bulongan, Ost-Borneo . Ecoglae geologicae Helvetiae Vol. 19(3)
Blow,W.H. and Banner,F.T. (1962):
The Mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae.
In: Fundamentals of Mid‑Tertiary Stratigraphical Correlation Eds: Eames, F.E.Banner, F.T.Blow, W.H.Clarke, W.J. p. 61‑151
Blow,W.H. (1969):
Late middle Eocene to Recent planktonic foraminiferal biostratigraphy.
In: Proceedings of the First International Conference on Planktonic Microfossils, Geneva 1967 Vol. 1 Eds: Bronnimann, P.Renz, H.H. p. 199-422
Blow,W.H. (1979):
The Cainozoic Globigerinida. 3 Vols p. 1413 pp
Bolli,H.M. and Saunders,J.B. (1985):
Oligocene to Holocene low latitude planktic foraminifers.
In: Plankton Stratigraphy Eds: Bolli, H.M.Saunders, J.B. p. 155-262
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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