Morphological variability of menardiform globorotalids in the Atlantic Ocean during Mid-Pliocene

Mary, Yannick and Knappertsbusch, Michael. (2013) Morphological variability of menardiform globorotalids in the Atlantic Ocean during Mid-Pliocene. Marine Micropaleontology, Vol. 101, S. 180–193.

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Official URL: http://edoc.unibas.ch/dok/A6093995

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The morphological variation of the planktonic foraminifera plexus of Globorotalia (Menardella) (Bandy 1972) has been studied in a Pliocene time-slice at 3.2 Ma. Using a combination of size, linear shell measurements and shape factors analysis, an extended morphological protocol is explored in order to define morphological subgroups within the Menardella subgenus (Bandy 1972). Isochronous samples at 3.2 Ma have been selected at five ODP/IODP sites in the low latitude Atlantic Ocean, in which up to 600 specimens per sample have been oriented, imaged and analyzed using a new automated prototype for morphological analysis called AMOR. Multimodal size frequency distribution is related to the occurrence of several distinct populations. Three main ubiquitous populations of such menardellids are isolated, next to two additional biogeographically limited subgroups. These populations strongly differ in abundance and size. Using morphological classifiers,subpopulations are distinguished among these populations, leading to the establishment of seven different morphotypes informally named: MA, MB, MC1, MC2, MC3, SH1 and SH2.These morphotypes are assigned to formal species, i.e., MA corresponds to Globorotalia(Menardella) menardii, MB to G.(M.) limbata, SH1 to G.(M.) exilis, and SH2 to G. (M.)pertenuis. In contrast, the species G. (M.) multicamerata is interpreted as being composed of three distinct morphotypes, sharing a similar size range, but differing in shell morphology. Morphotype MC1 shows thin and elongated chambers, whereas morphotype MC2 is characterized by a thick and robust test. MC3 is inflated with a distinct flexure in the final chamber. Size differences are linked to variations in habitat temperature and oxygenation,with the exception of G.(M). multicamerata morphotypes, that are probably adapted to a productivity gradient.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Ehemalige Einheiten Umweltwissenschaften > Paläontologie (Meyer)
UniBasel Contributors:Knappertsbusch, Michael W. and Mary, Yannick
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:21 Jun 2013 12:29
Deposited On:21 Jun 2013 12:27

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