Oxygen-18 Studies of Recent Planktonic Foraminifera: Comparisons of Phenotypes and of Test Parts

Abstract
Oxygen isotopic comparisons of phenotypes of Recent Planktonic Foraminifera with both normal and diminutive final chambers are compatible with a model in which the latter develop as a response to environmental stress. Isotopic evidence shows that Spheroidinella dehiscens is probably not a late-stage, aberrant form of Globogerinoides sacculifer.