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Dryad

The life and times of Pteridinium simplex

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Apr 22, 2022 version files 874.92 KB

Abstract

Pteridinium simplex is an iconic erniettomorph taxon best known from late Ediacaran successions in South Australia, Russia, and Namibia. Despite nearly 100 years of study, there remain fundamental questions surrounding the paleobiology and -ecology of this organism, including it’s life position relative the sediment-water interface, and how it fed and functioned within benthic communities. Here, we combine a re-description of specimens housed at the Senckenberg Forschungsinstitut und Naturmuseum Frankfurt with field observations of fossiliferous surfaces to constrain the life habit of Pteridinium and gain insights into the character of benthic ecosystems shortly before the beginning of the Cambrian. We present paleontological and sedimentological evidence suggesting that Pteridinium was semi-infaunal and lived gregariously in aggregated communities, preferentially adopting an orientation with the long-axis perpendicular to the prevailing current direction. Using computational fluid dynamics simulations, we demonstrate that this life habit could plausibly have led to suspended food particles settling within the organism’s central cavity. This supports interpretation of Pteridinium as a macroscopic suspension feeder that functioned similarly to the coeval erniettomorph Ernietta, emblematic of a broader paleoecological shift towards benthic suspension feeding strategies over the course of the latest Ediacaran. Lastly, we discuss how this new reconstruction of Pteridinium informs on its potential relationships with extant animal groups, and state a case for reconstructing Pteridinium as a colonial metazoan.