In situ filamentous communities from the Ediacaran (~563 Ma) of Brazil

Precambrian filamentous microfossils are common and diverse. Nevertheless, their taxonomic assignment can be difficult due to their overall simple shapes typically lacking in diagnostic features. Here, we report in situ communities of well-preserved, large filamentous impressions from the Ediacaran Itajaí Basin (ca. 563 Ma) of Brazil. The filaments are uniserial (unbranched) and can reach up to 200 µm in width and up to 44 mm in length. They occur as both densely packed or sparsely populated surfaces, and typically show a consistent orientation. Although simple in shape, their preferred orientation suggests they were tethered to the seafloor, and their overall flexibility (e.g. bent, folded, and twisted) supports a biological (rather than sedimentary) affinity. Biometric comparisons with modern filamentous groups further support their biological affinity, suggesting links with either large sulphide-oxidizing bacteria (SOB) or eukaryotes. Other morphological and palaeoecological characte...