PRESERVING THE EARTH’S EARLIEST-KNOWN GUTS: A GOLDILOCKS MODEL FOR PYRITIZATION IN THE TERMINAL EDIACARAN OF NEVADA (Invited Presentation)

The “cloudinomorph” assemblages of the terminal Ediacaran Period (ca. 551–539 Ma) occupy a unique temporal, and perhaps evolutionary, position between the tail-end of the classic Ediacara biota and the appearance of more recognizable animals in the Cambrian Period. While we have yet to attain a clear picture of the broader relationships of all members of the cloudinomorphs, recent reports of both plausible through-guts (e.g., Schiffbauer et al., 2020, Nature Communications) as well as polytomous branching (e.g., Shore et al., 2020, Geology) from differing members of this morphological guild suggest that they may most likely represent a polyphyletic group.

Several recent reports (e.g., Selly et al., 2020, Journal of Systematic Palaeontology; Smith et al., 2016 and 2017, Geology and Proceedings of the Royal Society of London B) have highlighted the distribution and taxonomy of cloudinomorphs from the Great Basin region, Nevada, USA—most specifically from the Deep Spring and Wood Canyon formations of Esmeralda and Nye counties, respectively. It is from these examples that the aforementioned nephrozoan-like guts were discovered. While generally comparable in pyritization-type preservation to those of the contemporaneous Gaojiashan Lagerstätte in China, the taphonomy of the Nevada cloudinomorphs has not been explored in detail. Here, we will describe our proposed taphonomic model for their fossilization, including the “goldilocks”-scenario that led to the preservation of the internal soft tissues, in comparison with other well-known late Ediacaran through early Paleozoic pyritized fossil deposits.