Ornamental polymorphism and morphological integration in Brizalina mandoroveensis (Miocene, Cameroun)

Abstract

The Miocene foraminiferal species Brizalina mandoroveensis (Graham, deKlasz, Rérat) from the Early to Middle Miocene of the Gulf of Guinea, West Africa, displays polymorphism in its pattern of ribbing, such that the normal form is ornamented with longitudinal riblets and the subordinate morph with a ladderlike pattern of struts joined in parallel to riblets. Multivariate statistical analyses based on size variables disclose subtle differences in the variability of the tests, which may be correlated with the frequencies of the two morphs in a particular sample. The relationship between sets constituted by morphological size variables, on the one hand, weighed against measures of shape, on the other, shows a significant relaxation in the level of morphological integration between sets over time.