Evolutionary Trends in Bolivina From Maastrichtian to Eocene, Nigeria

SEM study of Maastrichtian to Eocene bolivinids shows evolutionary trends of biocharacters in recognized lineage leading from Afrobolivina afra to Bolivina ignara. The foremost trends is the reduction in size of the Afrobolivina afra to Bolivina ignara. Other trends are: increased flare of chambers (B. ignara), development of coarser and more widely set pores (B. striatella, B. ottaensis and B. ignara), more closely set pores (Afrobolivina afra and B. africana), development of costae and sutural lobes that became less prominent from Afrobolivina afra to B. ignara. Two phylogenetic lineages are proposed based on evolutionary trends that have allowed the linkage of related forms: Afrobolivina afra, Bolivina africana, B. striatella and B. ottaensis, and Afrobolivina afra, B. africana and B. ignara.