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Origin of the Eocene planktonic foraminifer Hantkenina by gradual evolution

Pearson, Paul Nicholas and Coxall, Helen Kathrine 2014. Origin of the Eocene planktonic foraminifer Hantkenina by gradual evolution. Palaeontology 57 (2) , pp. 243-267. 10.1111/pala.12064

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Abstract

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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Earth and Ocean Sciences
Subjects: Q Science > QE Geology
Uncontrolled Keywords: Hantkenina singanoae; evolution; foraminifera; Eocene; Tanzania
Publisher: Wiley-Blackwell
ISSN: 0031-0239
Funders: NERC
Date of First Compliant Deposit: 30 March 2016
Date of Acceptance: 3 June 2013
Last Modified: 26 Feb 2019 14:19
URI: http://orca-mwe.cf.ac.uk/id/eprint/52626

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