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ABSTRACT

The taxonomy, phylogeny and biostratigraphy of Eocene microperforate taxa classified under Jenkinsina, Cassigerinelloita, Chiloguembelina, Zeauvigerina, Tenuitella, and Cassigerinella is presented. A total of 20 microperforate species are recognized in Eocene planktonic foraminifer assemblages, namely: Jenkinsina columbiana (Howe), Jenkinsina triseriata (Terquem), Cassigerinelloita amekiensis Stolk, Chiloguembelina crinita (Glaessner), Chiloguembelina cubensis (Palmer), Chiloguembelina ototara (Finlay), Chiloguembelina parallela Beckmann, Chiloguembelina trinitatensis (Cushman and Renz), Chiloguembelina wilcoxensis (Cushman and Ponton), Streptochilus martini (Pijpers), Zeauvigerina aegyptiaca Said and Kenawy, Zeauvigerina lodoensis Martin, Zeauvigerina parri Finlay, Zeauvigerina zelandica Finlay, Tenuitella gemma (Jenkins), Tenuitella insolita (Jenkins), Tenuitella patefacta Li, Tenuitella praegemma Li, Cassigerinella chipolensis (Cushman and Ponton), and Cassigerinella eocaenica Cordey.

Two species are placed in Problematica pending clarification of their taxonomic position. These are Dipsidripella danvillensis (Howe and Wallace) and Dipsidripella liqianyui Huber and Pearson n. sp. Oxygen isotope signatures of D. danvillensis are more similar to co-occurring benthic species than to planktonic species, and carbon isotope ratios are significantly more negative than co-occurring benthic and planktonic species. Identification of a monolamellar wall microstructure in D. danvillensis indicates that this species is unrelated to the Globigerinaceae or Hetero-helicacea, and its restricted occurrence in neritic biofacies suggests that it lived part or most of its life below the thermocline. The wall microstructure and habitat preference of D. liqianyui n.sp. cannot be determined because of the inadequate preservation and limited distribution of specimens studied thus far. Observation of a monolamellar wall structure in J. columbiana, T. praegemma, T. gemma, and T. insolita indicates that the Eocene microperforate species may share a common ancestor.

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