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Origin of the Eocene planktonic foraminifer Hantkenina by gradual evolution:
Stockholm University, Faculty of Science, Department of Geological Sciences. Cardiff University, UK.
2014 (English)In: Palaeontology, ISSN 0031-0239, E-ISSN 1475-4983, Vol. 57, no 2, 243-267 p.Article in journal (Refereed) Published
Abstract [en]

Hantkenina is a distinctive planktonic foraminiferal genus characterized by the presence of tubulospines (robust hollow projections) on each adult chamber, from Middle and Upper Eocene marine sediments worldwide. Here we illustrate its evolutionary origin using c. 150 specimens from 30 stratigraphic intervals in two sediment cores from Tanzania. The specimens, which span an estimated time interval of 300 ka, show four intermediate steps in the evolution of the tubulospines that amount to a complete intergradation from Clavigerinella caucasica, which does not possess them, to Hantkenina mexicana, which does. Stable isotope analyses indicate that the transitional forms evolved in a deep planktonic habitat not occupied at that time by other species of planktonic foraminifera. We discuss the morphogenetic constraints involved in the evolutionary transition and propose an ecological/adaptive model for the selective pressures that resulted in the evolution of tubulospines. We compare our record with similar, recently described assemblages from Austria and Italy, and we update the biostratigraphy and systematic taxonomy of the key morphospecies involved in the transition.

Place, publisher, year, edition, pages
2014. Vol. 57, no 2, 243-267 p.
Keyword [en]
Hantkenina singanoae, evolution, foraminifera, Eocene, Tanzania
National Category
URN: urn:nbn:se:su:diva-98034DOI: 10.1111/pala.12064ISI: 000332776600002OAI: diva2:682222
Available from: 2013-12-25 Created: 2013-12-25 Last updated: 2014-04-22Bibliographically approved

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Coxall, Helen K.
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