Research Article| December 01, 2011 Putative Cryogenian ciliates from Mongolia T. Bosak; T. Bosak 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar F. Macdonald; F. Macdonald 2Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA Search for other works by this author on: GSW Google Scholar D. Lahr; D. Lahr 3Graduate Program in Organismic and Evolutionary Biology, University of Massachusetts, Amherst, Massachusetts 01003, USA Search for other works by this author on: GSW Google Scholar E. Matys E. Matys 1Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Search for other works by this author on: GSW Google Scholar Geology (2011) 39 (12): 1123–1126. https://doi.org/10.1130/G32384.1 Article history received: 25 Apr 2011 rev-recd: 05 Jul 2011 accepted: 07 Jul 2011 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation T. Bosak, F. Macdonald, D. Lahr, E. Matys; Putative Cryogenian ciliates from Mongolia. Geology 2011;; 39 (12): 1123–1126. doi: https://doi.org/10.1130/G32384.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Major lineages of modern eukaryotes, represented primarily by microscopic taxa, are thought to have originated during the Neoproterozoic, but microfossils older than 635 Ma rarely have unambiguous relationships to modern microscopic eukaryotes. Here we report exceptionally preserved 715–635 m.y. old eukaryotic tests in limestone strata of Mongolia. The ∼100-μm-long organic-rich three-dimensional tests have flask-like shapes, constricted necks, distinct and often thickened collars, and flexible walls composed of densely packed alveolar structures. The combined morphological and ultrastructural characters of these Cryogenian tests are remarkably similar to the tests of tintinnids, modern planktonic ciliates. Eukaryotes forming recalcitrant organic or mineral-rich tests before 635 Ma may have increased export and burial fraction of organic carbon, driving an increase in atmospheric oxygen and the subsequent radiation of metazoans. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.