Figure F17. Photomicrographs of exceptionally well preserved planktonic foraminifers from the upper middle Eocene, Site U1408. A. Hantkenina compressa, Hantkenina dumblei, and Hantkenina liebusi reveal a glassy, transparent taphonomy, particularly in their final few chambers, and intact tubulospines, a rarity in typical pelagic deep-sea sequences (Sample 342-U1408A-6H-CC). B. Globigerinatheka index displaying semiglassy taphonomy and the presence of relict spines within the apertural opening. C, D. Orbulinoides superbeckmanni, characterized by a completely spherical test, which likely marks the acme of the Middle Eocene Climatic Optimum (MECO). E–G. Orbulinoides beckmanni (ancestor of C, D), which has a comparatively short (~1.6–1.0 m.y.) total range concurrent with the MECO (Edgar et al., 2010).
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