Three-dimensional reconstructions of the putative metazoan Namapoikia show that it was a microbial construction
Abstract
Strata from the Ediacaran Period (635 million to 538 million years ago [Ma]) contain several examples of enigmatic, putative shell-building metazoan fossils. These fossils may provide insight into the evolution and environmental impact of biomineralization on Earth, especially if their biological affinities and modern analogs can be identified. Recently, apparent morphological similarities with extant coralline demosponges have been used to assign a poriferan affinity to Namapoikia rietoogensis, a modular encrusting construction that is found growing between (and on) microbial buildups in Namibia. Here, we present three-dimensional reconstructions of Namapoikia that we use to assess the organism's proposed affinity. Our morphological analyses, which comprise quantitative measurements of thickness, spacing, and connectivity, reveal that Namapoikia produced approximately millimeter-thick meandering and branching/merging sheets. We evaluate this reconstructed morphology in the context of poriferan biology and determine that Namapoikia likely is not a sponge-grade organism.
Additional Information
© 2020 National Academy of Sciences. Published under the PNAS license. Edited by Andrew H. Knoll, Harvard University, Cambridge, MA, and approved June 23, 2020 (received for review May 12, 2020). PNAS first published August 3, 2020. We thank C. Husselmann for granting us access to Driedoornvlakte Farm. At the Geological Survey of Namibia, G. Schneider and J. Eiseb granted us permits for working in Namibia and assisted us with the export permitting process, respectively. At MIT, B. Ren performed grinding and imaging, and T. Mason created an early reconstruction, of sample B. All of Situ Studio, but especially B. Samuels, were instrumental in the development of GIRI. A. Tasistro Hart and R. Bartolucci provided invaluable assistance in the field. At the Smithsonian, M. Florence dedicated his time to help locate Inozoan specimens for study, while D. Erwin kindly gave permission to destructively analyze the A. perforata sample. R. Shapiro generously provided us with a sample of F. cooperi for reconstruction. Our morphological analyses benefited from discussions with A. Getraer, B. Howes, R. Manzuk, and E. Geyman. We thank J. Strauss for feedback on the manuscript and A. Knoll and two anonymous reviewers for their thoughtful critique and input. This work was supported by NSF Earth Sciences Grant 1028768 to A. Maloof and by funding from the Princeton Tuttle Invertebrate Fund. All raw image data are available upon request. The computational source code used to process data in this paper is located in a public repository at https://github.com/giriprinceton/namapoikia. Author contributions: A.M., W.A.W., J.P.G., and A.C.M. designed research; A.M. performed research; A.M. and A.C.M. analyzed data; and A.M. and A.C.M. wrote the paper. The authors declare no competing interest. This article is a PNAS Direct Submission. Data deposition: The computational source code used in this paper is available in GitHub at https://github.com/giriprinceton/namapoikia. This article contains supporting information online at https://www.pnas.org/lookup/suppl/doi:10.1073/pnas.2009129117/-/DCSupplemental.Attached Files
Published - 19760.full.pdf
Supplemental Material - pnas.2009129117.sapp.pdf
Supplemental Material - pnas.2009129117.sm01.mp4
Supplemental Material - pnas.2009129117.sm02.mp4
Supplemental Material - pnas.2009129117.sm03.mp4
Supplemental Material - pnas.2009129117.sm04.mp4
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Additional details
- PMCID
- PMC7443946
- Eprint ID
- 104714
- Resolver ID
- CaltechAUTHORS:20200804-071748120
- EAR-1028768
- NSF
- Princeton University
- Created
-
2020-08-04Created from EPrint's datestamp field
- Updated
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2022-02-09Created from EPrint's last_modified field
- Caltech groups
- Division of Geological and Planetary Sciences