The evolution of Eocene planktonic foraminifera <i>Dentoglobigerina</i>

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