Operculina and Neoassilina: A Revision of Recent Nummulitid Genera Based on Molecular and Morphological Data Reveals a New Genus

Maria Holzmann, Johann Hohenegger, Laure Apothéloz-Perret-Gentil, Raphael Morard, Sigal Abramovich, Danna Titelboim, Jan Pawlowski

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


The genus Operculina, a large symbiont-bearing benthic foraminifer, is characterized by high morphological variability showing thick involute to intermediate semi-involute to flat evolute tests. Different morphotypes are either considered as ecophenotypes or distinct species. In order to test the hypothesis of ecophenotypes versus different species, a single cell high throughput sequencing approach was applied to assess the interspecific diversity of Operculina. This results in two groups of ribotypes, one corresponding to Operculina ammonoides/Operculina discoidalis, the other containing Operculina complanata/Operculina elegans. These groups can also be separated morphologically. Therefore, O. complanata and O. elegans represent a single species and the latter can be regarded as a junior synonym of O. complanata. Operculina ammonoides and O. discoidalis also form a single species, which makes the latter a junior synonym of O. ammonoides. Because generic differences in Operculina species are manifested in morphology and molecular genetics, the genus Neoassilina with the designated species Neoassilina ammonoides is installed. Additional analysis of ribosomal SSU rDNA data of eight recent nummulitid genera confirms the obtained high troughput sequencing results and further shows that Palaeonummulites venosus builds a clade with O. complanata that branches at the base of other Nummulitidae containing Planostegina, Planoperculina, Cycloclypeus, Heterostegina, Operculinella and Neoassilina.

Original languageEnglish
Pages (from-to)1411-1424
Number of pages14
JournalJournal of Earth Science
Issue number6
StatePublished - 1 Dec 2022


  • Neoassilina
  • Nummulitidae
  • Operculina
  • SSU rDNA
  • interspecific diversity
  • morphology

ASJC Scopus subject areas

  • General Earth and Planetary Sciences


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