Dentoglobigerina tripartita


Classification: pf_cenozoic -> muricate non-spinose -> Globoquadrinidae -> Dentoglobigerina -> Dentoglobigerina tripartita
Sister taxa: D. galavisi, D. pseudovenezuelana, D. tripartita,

Taxonomy

Citation: Dentoglobigerina tripartita (Koch 1926)
Rank: Species
Basionym: Globigerina bulloides tripartita
Synonyms:
Taxonomic 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 are 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 misshapen”. 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 cap-like 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 Dentoglobigerina praedehiscens (Blow and Banner) and then to Globoquadrina dehiscens Finlay. Kennett and Srinivasan (1983) 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. [Olsson et al. 2006]

Catalog entries: Globigerina bulloides tripartita;

Type images:

Short diagnosis: 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.

NB The short diagnoses are used in the tables of daughter-taxa to act as quick summaries of the differences between e.g. species of one genus. They have initially been copied from the diagnostic characters/distinguishing features sections of the Eocene and Paleocene Atlases, they will be edited as the site is developed.

Description


Diagnostic characters: 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. [Olsson et al. 2006]

Biogeography and Palaeobiology


Geographic distribution: Known from low and mid latitude locations. [Olsson et al. 2006]

Isotope paleobiology: Oligocene specimens from ODP Hole 758A registered among the heaviest ∂18O of planktonic assemblages indicating a deep habitat, although earliest Oligocene specimens may have had a shallower water preference (Van Eijden and Ganssen, 1995). [Olsson et al. 2006]

Phylogenetic relations: 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. [Olsson et al. 2006]

Biostratigraphic distribution

Geological Range:
Notes: Zone E13? to Zone O6 (=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. [Olsson et al. 2006]
Last occurrence (top): within O6 zone (25.21-26.93Ma, top in Chattian stage). Data source: Eocene Atlas
First occurrence (base): within E13 zone (37.99-39.97Ma, base in Bartonian stage). Data source: Eocene Atlas

Plot of occurrence data:

Primary source for this page: Olsson et al. 2006 - Atlas of Eocene Planktonic Foraminifera, chapter 13, p. 408

References:

Blow, W.H. & Banner, F.T., (1962). The mid-Tertiary (Upper Eocene to Aquitanian) Globigerinaceae. In: Eames, F.E. et al. (Editors), Fundamentals of mid-Tertiary Stratigraphical Correlation. Cambridge University Press, Cambridge, pp. 61-151.

Blow, W.H., (1969). Late middle Eocene to Recent planktonic foraminiferal biostratigraphy. In: Bronnimann, P. and Renz, H.H. (Editors), Proceedings of the First International Conference on Planktonic Microfossils, Geneva, 1967, Leiden, Netherlands, pp. 380-381.

Blow, W.H., (1979). The Cainozoic Globigerinida: A study of the morphology, taxonomy, evolutionary relationships and stratigraphical distribution of some Globigerinida (mainly Globigerinacea). E. J. Brill, Leiden, 1413 pp.

Bolli, H.M. & Saunders, J.B., (1985). Oligocene to Holocene low latitude planktic foraminifera. In: Bolli, H.M., Saunders, J.B. and Perch-Neilsen, K. (Editors), Plankotn Stratigraphy. Cambridge University Press, Cambridge, UK, pp. 155-262.

Eijden & Ganssen 1995 [sorry, not in our bibliography yet]

Fleisher, R.L., (1974). Cenozoic planktonic foraminifera and biostratigraphy, Arabian Sea, Deep Sea Drilling Project, Leg 23A. Initial Reports of the Deep Sea Drilling Project, 23: 1001-1072.

Kennett, J.P. & Srinivasan, M.S., (1983). Neogene Planktonic Foraminifera. Hutchinson Ross Publishing Co., Stroudsburg, Pennsylvania, 1-265 pp.

Koch, R., (1926). Mitteltertiare Foraminiferen aus Bulongan, Ost-Borneo. Eclogae Geologicae Helvetiae, 19: 207-213.

Olsson, R.K.; Hemleben, C. & Pearson, P.N., (2006). Taxonomy, biostratigraphy, and phylogeny of Eocene Dentoglobigerina. In: Pearson, P.N. et al. (Editors), Atlas of Eocene Planktonic Foraminifera, Cushman Foundation Special Publication 41. Cushman Foundation Special Publication. Allen Press, Lawrence, Kansas, pp. 401-412.

Spezzaferri, S., (1994). Planktonic foraminiferal biostratigraphy and taxonomy of the Oligocene and lower Miocene in the oceanic record. An overview. Palaeontographia Italica, 81: 1-187.


Dentoglobigerina tripartita compiled by the pforams@mikrotax project team viewed: 29-4-2017

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