20 December 2011

Hippler and colleagues, 2011

Hippler D, Hu N, Steiner M, Scholtz G, Franz G. 2011. Experimental mineralization of crustacean eggs leads to surprising tissue conservation: new implications for the fossilization of Precambrian-Cambrian embryos. Biogeosciences Discussions 8: 12051-12077. http://dx.doi.org/10.5194/bgd-8-12051-2011


Phosphatized globular microfossils from the Ediacaran and Lower Cambrian of South China represent an impressive record of early animal evolution and development, however their affinity based on putative embryonic metazoan, bacterial and inorganic features is strongly debated. Understanding key processes and conditions that cause exceptional egg and embryo preservation and fossilization are therefore crucial for a reliable interpretation of their phylogenetic position. Taphonomic experiments on eggs of the marbled crayfish indicate a close link between early mineralization and rapid anaerobic decay of the endochorional envelope, producing different preservational stages of degradation resembling the various decay stages observed in the fossil record. Stabilization of the spherical morphology was achieved by pre-heating of the eggs. Complete surface mineralization occurred under reduced conditions within one to two weeks, with fine-grained brushite (CaHPO4·2H2O) over calcite as the dominating mineral phase. Although the endochorional envelope was not preserved, experiments resulted in exceptional preservation of the embryonic tissue at the cellular level. Thus our findings suggest that the mechanisms of decay, preservation of surface structures, and mineral replacement in the experiment and during fossilization of Cambrian embryos were likely operating at a similar rationale.

Keywords: None provided.

Note: This discussion paper is under review for the journal Biogeosciences. This journal has an editorial policy that differs from many other journals, described as “innovative two-stage publication process with Public Peer-Review & Interactive Public Discussion.” The paper is initially published – permanently archived – in Biogeosciences Discussions, to receive comments (which are also archived). If the paper is accepted by the editors of Biogeosciences, the final version appears in that journal as the “copy of record.” If not, the paper remains in Biogeosciences Discussions, does not contribute to the Biogeosciences’ Impact Factor, etc.

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