The evolution of Eocene planktonic foraminifera Dentoglobigerina

Abstract

Dentoglobigerina is a diverse genus of planktonic foraminifera ranging from the Eocene to Recent. However, the ancestry of Dentoglobigerina has been controversial. A growing body of evidence indicates that the genus Dentoglobigerina was spinose in life and evolved from Eocene Subbotina, whilst others have suggested its origins stem from Acarinina. Here we explore whether Subbotina or Acarinina is the ancestor of Dentoglobigerina by examining 35 specimens, evaluating their morphology and their occurrences through the middle to late Eocene, from localities worldwide. We find that Dentoglobigerina evolved ∼4 million years earlier than previously documented, with the species Dentoglobigerina pseudovenezuelana and ‘Dentoglobigerina’ eotripartita recorded in middle Eocene, Zone E9. Morphological convergences between Dentoglobigerina and Subbotina were found with D. galavisi and D. pseudovenezuelana, and between Dentoglobigerina and Acarinina with ‘D.’ eotripartita. Spine holes were observed in D. galavisi and D. pseudovenezuelana, though not uniformly found in all forms. Our findings suggest that there are two distinct lineages: (1) Dentoglobigerina, encompassing the species D. pseudovenezuelana and D. galavisi as a descendant of Subbotina; and (2) ‘Dentoglobigerina’ (including ‘D.’ eotripartita) as a descendant of Acarinina. Our results contribute to a better understanding of Dentoglobigerina biostratigraphy, phylogeny and evolution, and have implications for taxonomy.