Emendation of the genus Streptochilus (Foraminifera) and new species from the lower Miocene of the Atlantic and Indian Oceans

Smart, Christopher; Thomas, Ellen

doi:10.2113/gsmicropal.53.1-2.73

Cited by 22 publications

(10 citation statements)

References 65 publications

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“…Small, smooth-walled species of the genus "Bolivina" (called Streptochilus by Smart & Thomas 2006 reached extremely high relative abundances in the open-ocean (Thomas 1987;Smart & Ramsay 1995;Smart & Thomas 2007).…”

Section: Discussion and Interpretationmentioning

confidence: 99%

“…According to Brönnimann & Resig (1971) and Smart & Thomas (2007), the genus Streptochilus has particular morphological features compared to Bolivina: a loop-shaped aperture bordered by a high, collar-like projection, except for an inturned portion at the inner margin. The internal plate that connects succeeding apertural borders does not project freely into the aperture as a tooth plate (as in the case of Bolivinitidae).…”

Section: Biserial Foraminiferal Assemblagesmentioning

confidence: 99%

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An Early Miocene biserial foraminiferal event in the Transylvanian Basin (Romania)

Beldean¹,

Filipescu²,

Bălc³

2010

Geologica Carpathica

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Abstract:Investigations of the Lower Miocene of the Transylvanian Basin reveal particularly high abundances ( > 90 % of total foraminifera) of small sized biserial foraminifera (Bolivina/Streptochilus). This biotic event has not been noticed in the Transylvanian Basin so far probably owing to the facies misinterpretation and the small size of the specimens. SEM investigations allow more precise identification of biserial planktonic taxa and more accurate taxonomic interpretations. The high abundance of Bolivina/Streptochilus assemblages provide evidence for paleogeographic connections to the IndoPacific area and support new paleoenvironmental interpretations at the transition from the Early to Middle Miocene in relation to the paleoceanographic events. Both planktonic foraminifera and calcareous nannoplankton suggest a late Burdigalian age. A new Bolivina/Streptochilus Abundance Biozone is proposed just below the Early/Middle Miocene boundary.

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Section: Discussion and Interpretationmentioning

confidence: 99%

Section: Biserial Foraminiferal Assemblagesmentioning

confidence: 99%

An Early Miocene biserial foraminiferal event in the Transylvanian Basin (Romania)

Beldean¹,

Filipescu²,

Bălc³

2010

Geologica Carpathica

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“…Gallitellia is a surface-dweller known as a tracer of high runoff, environmental unstability and upwelling conditions (e. g., Kroon and Nederbragt, 1990;Kimoto et al, 2009). Recently, Smart andThomas (2006, 2007) interpreted the Miocene Streptochilus as an opportunist form with a similar ecological behaviour. In addition, Pseudoglobigerinella bolivarina is exclusively found in high-productivity/upwelling areas (Pearson et al, 2006).…”

Section: Eutrophication and Lowered Oxygenation Of The Upper Water Comentioning

confidence: 99%

Ecological and evolutionary response of Tethyan planktonic foraminifera to the middle Eocene climatic optimum (MECO) from the Alano section (NE Italy)

Luciani

Giusberti

Agnini

et al. 2010

Palaeogeography, Palaeoclimatology, Palaeoecology

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a b s t r a c t a r t i c l e i n f oThe enigmatic middle Eocene climatic optimum (MECO) is a transient (∼ 500 kyr) warming event that significantly interrupted at ∼ 40 Ma the long-term cooling through the middle and late Eocene, eventually resulting in establishment of permanent Antarctic ice-sheet. This event is still poorly known and data on the biotic response are so far scarce. Here we present a detailed planktonic foraminiferal analysis of the MECO interval from a marginal basin of the central-western Tethys (Alano section, northeastern Italy). The expanded and continuous Alano section provides an excellent record of this event and offers an appealing opportunity to better understand the role of climate upon calcareous plankton evolution. A sapropel-like interval, characterized by excursions in both the carbon and oxygen bulk-carbonate isotope records, represents the lithological expression of the post-MECO event in the study area and follows the δ 18 O negative shift, interpreted as representing the MECO warming. High-resolution quantitative analysis performed on both N38 μm and N 63 μm fractions reveals pronounced and complex changes in planktonic foraminiferal assemblages indicating a strong environmental perturbation that parallels the variations of the stable isotope curves corresponding to the MECO and post-MECO intervals. These changes consist primarily in a marked increase in abundance of the relatively eutrophic subbotinids and of the small, low-oxygen tolerant Streptochilus, Chiloguembelina and Pseudohastigerina. At the same time, the arrival of the abundant opportunist eutrophic Jenkinsina and Pseudoglobigerinella bolivariana, typical species of very high-productivity areas, also occurs. The pronounced shift from oligotrophic to more eutrophic, opportunist, low-oxygen tolerant planktonic foraminiferal assemblages suggests increased nutrient input and surface ocean productivity in response to the environmental perturbation associated with the MECO. Particularly critical environmental conditions have been reached during the deposition of the sapropel-like beds as testified by the presence of common giant and/or odd morphotypes. This is interpreted as evidence of transient alteration in the ocean chemistry. The enhanced surface water productivity inferred by planktonic foraminiferal assemblages at the onset of the event should have resulted in heavier δ 13 C values. The recorded lightening of the carbon stable isotope preceding the maximum warmth therefore represents a robust indication that it derives principally by a conspicuous increase of pCO 2 . The increased productivity of surface waters, also supported by geochemical data, may have acted as mechanism for pCO 2 reduction and returned the climate system to the general Eocene cooling trend. The oxygen-depleted deep waters and the organic carbon burial following the peak of the MECO event represent the local response to the MECO warming and suggest that high sequestration of organic matter, if representing a widespread response to this event, m...

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“…Such a lifestyle is known from diatoms, but until now has never been documented for foraminifera. Tychopelagic forms may well evolve into true pelagic forms: The fossil record shows convincingly that biserials are particularly abundant in the planktic foraminiferal assemblage at some time intervals, with isotopic as well as distributional evidence suggesting that they were truly pelagic forms, reproducing in situ (8,9,(28)(29)(30)(31). The tychopelagic mode of life differs fundamentally from that of the few documented meroplanktic benthics such as Tretomphalus (32), a generic name used for individuals of the genus Rosalina, which at a specific, late stage in their life cycle form a floating chamber containing gametes (32,33).…”

Section: Resultsmentioning

confidence: 99%

Surviving mass extinction by bridging the benthic/planktic divide

Darling

Thomas

Kasemann

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Evolution of planktic organisms from benthic ancestors is commonly thought to represent unidirectional expansion into new ecological domains, possibly only once per clade. For foraminifera, this evolutionary expansion occurred in the Early-Middle Jurassic, and all living and extinct planktic foraminifera have been placed within 1 clade, the Suborder Globigerinina. The subsequent radiation of planktic foraminifera in the Jurassic and Cretaceous resulted in highly diverse assemblages, which suffered mass extinction at the end of the Cretaceous, leaving an impoverished assemblage dominated by microperforate triserial and biserial forms. The few survivor species radiated to form diverse assemblages once again in the Cenozoic. There have, however, long been doubts regarding the monophyletic origin of planktic foraminifera. We present surprising but conclusive genetic evidence that the Recent biserial planktic Streptochilus globigerus belongs to the same biological species as the benthic Bolivina variabilis, and geochemical evidence that this ecologically flexible species actively grows within the open-ocean surface waters, thus occupying both planktic and benthic domains. Such a lifestyle (tychopelagic) had not been recognized as adapted by foraminifera. Tychopelagic are endowed with great ecological advantage, enabling rapid recolonization of the extinction-susceptible pelagic domain from the benthos. We argue that the existence of such forms must be considered in resolving foraminiferal phylogeny.end-Cretaceous ͉ foraminifera ͉ Mg/Ca ͉ plankton evolution ͉ SSU rRNA

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Emendation of the genus Streptochilus (Foraminifera) and new species from the lower Miocene of the Atlantic and Indian Oceans

Cited by 22 publications

References 65 publications

An Early Miocene biserial foraminiferal event in the Transylvanian Basin (Romania)

An Early Miocene biserial foraminiferal event in the Transylvanian Basin (Romania)

Ecological and evolutionary response of Tethyan planktonic foraminifera to the middle Eocene climatic optimum (MECO) from the Alano section (NE Italy)

Surviving mass extinction by bridging the benthic/planktic divide

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