Surfing in and on microbial mats: Oxygen-related behavior of a terminal Ediacaran bilaterian animal

Shuhai Xiao,Xunlai Yuan,Zhe Chen,Chuanming Zhou

doi:10.1130/g46474.1

Shuhai Xiao, Xunlai Yuan + Show 2 more

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https://doi.org/10.1130/g46474.1

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Abstract

AbstractGeochemical evidence suggests that terminal Ediacaran (ca. 551–539 Ma) oceans experienced expansive anoxia and dynamic redox conditions, which are expected to have impacted animal distribution and behaviors. However, fossil evidence for oxygen-related behaviors of terminal Ediacaran animals is poorly documented. Here, we report a terminal Ediacaran trace fossil that records redox-regulated behaviors. This trace fossil, Yichnus levis new ichnogenus and new ichnospecies, consists of short and uniserially aligned segments of horizontal burrows that are closely associated with microbial mats. Thin-section analysis shows that the trace-making animal moved repeatedly in and out of microbial mats, with mat-burrowing intervals interspersed by epibenthic intermissions. This animal is hypothesized to have been a bilaterian exploring an oxygen oasis in microbial mats. Such intermittent burrowing behavior reflects challenging and dynamic redox conditions in both the water column and microbial mats, highlighting the close relationship between terminal Ediacaran animals and redox dynamics.

Highlights

Emerging geochemical data indicate an episode of expansive oceanic anoxia in the terminal Ediacaran Period (Evans et al, 2018; Tostevin et al, 2018; Wei et al, 2018; Zhang et al, 2018), with spatially and temporally dynamic redox conditions in shallow oceans (Wood et al, 2015)
We describe a new trace fossil that bears on the behavior of terminal Ediacaran bilaterian animals in response to redox dynamics
Y. levis is the only trace fossil far found at the lower horizon, but it co-occurs with other as-yet-undescribed ichnotaxa at the upper horizon

Summary

Introduction

Emerging geochemical data indicate an episode of expansive oceanic anoxia in the terminal Ediacaran Period (Evans et al, 2018; Tostevin et al, 2018; Wei et al, 2018; Zhang et al, 2018), with spatially and temporally dynamic redox conditions in shallow oceans (Wood et al, 2015). We describe a new trace fossil that bears on the behavior of terminal Ediacaran bilaterian animals in response to redox dynamics. Y. levis is preserved in limestone of the terminal Ediacaran Shibantan Member of the Dengying Formation at Wuhe in the Yangtze Gorges area of South China (Fig. 1; Fig. DR1 in the Data Repository).

Results

Conclusion