THE FIRST DISASTER TAXA: VENDOTAENIDS AND THE EDIACARAN EXTINCTION

The Ediacaran-Cambrian boundary was a time of significant biological and geochemical change. This interval includes the first documented mass extinction on Earth with the disappearance of the Ediacara biota. Soon after this extinction, the oceans were populated with a diversity of crown-group metazoans during the Cambrian Explosion. However, in fossil records across the world, there is a noticeable gap between these two assemblages. This gap is critical to understanding what drove the extinction of the Ediacara biota and the diversification of crown-group metazoans.

In this study, we document abundant filamentous fossils of various taphonomic modes from the Ediacaran-Cambrian interval in passive margin sequences around the world. We describe these fossils, termed vendotaenid algae, from NW Canada, SW Mongolia, and Namibia. Morphological analysis of these newly documented fossils suggest that multiple algal taxa dominated the oceans in the aftermath of the Ediacaran-Cambrian Extinction before animals diversified. These filaments are preserved as carbonaceous compressions, in clay minerals, and through pyritization. The variety of preservational modes suggest that this is not an artifact resulting from an anomalous taphonomic window, and that these fossils were abundant for a short period between the Ediacara biota and the radiation of crown-group metazoans. These algae were able to thrive while many other eukaryotes perished, suggesting a general reduction in trophic levels in the global marine ecosystem. Similar to disaster taxa in the aftermath of Phanerozoic mass extinctions, vendotaenids can provide crucial clues to how the environment changed and the role it may have played in the extinction of the Ediacara biota and the subsequent diversification of metazoans. Further study of fossils that fill this gap will inform us of the circumstances that lead to the radiation of animal life.