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      TAXONOMY AND EVOLUTIONARY RELATIONSHIPS WITHIN THE CALCAREOUS NANNOFOSSIL GENUS <em>ERICSONIA</em> IN THE UPPER PALEOCENE

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          Abstract

          Detailed distribution ranges of the genus Ericsonia were obtained in the upper Paleocene interval from two deep-sea sections, ODP Site 1262 (South Eastern Atlantic Ocean) and Site 1215 (Eastern Equatorial Pacific Ocean), and were complemented with morphometric analyses with the purpose of clarifying the taxonomy of the Paleocene species ascribed to genus. The analysis on a high-resolution sampling set at ODP Site 1262 permitted to add information about the evolutionary relationship among the taxa included in the Ericsonia lineage, whose evolutionary emergence characterize the Paleocene nannofossil assemblages. Two taxonomic units have been validated in the Paleocene, Ericsonia subpertusa and Ericsonia robusta and they turned out to not have any evolutionary link. E. robusta shows substantial morphologic variability at cross-polarized light resulting in two endmember morphotypes, E. robusta morphotype A and E. robusta morphotype B. When observed at S.E.M., the two morphotypes have placoliths with a similar structure, therefore they document intra-specific variability. This is corroborated by the presence of specimens with intermediate morphologic features between the two endmembers, throughout the distribution range. E. robusta increases in abundance concomitantly with the sharp decline of E. subpertusa in mid Chron C25n. Subsequently, the highest occurrence of E. robusta morphotype B provides a distinct biohorizon coeval to the general decline of E. robusta within the upper Paleocene nannofossil assemblage.

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          Author and article information

          Journal
          Rivista Italiana di Paleontologia e Stratigrafia
          Università degli Studi di Milano
          01 January 2018
          : 124
          : 1
          Article
          145915bc5453401ebb00af0da4f6e794
          10.13130/2039-4942/9750
          41fdea0f-a464-44c5-b2eb-36e46ee97d43

          RIPS is published under a Creative Commons Attribution-NonCommercial-NoDerivatives Licence 4.0 International (CC BY-NC-ND 4.0). The journal allows the author(s) to hold the copyright without restrictions. To view a copy of this license, visit https://creativecommons.org/licenses/by-nc-nd/4.0/

          History
          Categories
          Geology
          QE1-996.5
          Paleontology
          QE701-760

          Geology & Mineralogy,General geosciences,General earth science,Paleontology,Geosciences
          upper Paleocene,calcareous nannofossils,morphometry,Ericsonia.

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