Lower Cambrian Anemone Burrows From the Upper Member of the Wood Canyon Formation, Death Valley Region, United States: Paleoecological and Paleoenvironmental Significance

A mixed Ediacaran-metazoan assemblage from the Zaris Sub-basin, Namibia

“…In addition, similar burrows assigned to Conichnus were described by Jensen and Runnegar (2005) from the southern Witputs sub-basin known to be latest Ediacaran, stratigraphically below sediments preserving Pteridinium Gürich, 1930 and the frondose taxon Swartpuntia Narbonne et al, (Darroch et al, 2015), confirming stratigraphic overlap between these trace fossil structures and soft-bodied Ediacara biota in southern Namibia as well. Burrows with similar morphology (albeit larger) are known from lowermost Cambrian rocks in Death Valley (Mata et al, 2012), and have a fossil record that extends throughout much of the Phanerozoic (Abad et al, 2006;Curran, 2007). Menon et al (2013) described similar structures showing upward movement in much older Ediacaran sections from Newfoundland; however, those structures are much larger than the burrows described here, and apparently terminate in Aspidella holdfast-type structures usually interpreted as belonging to frondose Ediacaran organisms.…”

“…Although it is notoriously hard to reliably match trace fossils with specific tracemakers, Conichnus-type burrows are almost universally attributed to anthozoan cnidarians, including sea anemones (Actinaria) and tube anemones (Ceriantharia) (Bromley, 1996;Abad et al, 2006;Buatois and Mangano, 2011;Mata et al, 2012;Menon et al, 2013;Desai and Saklani, 2015), in part through observation of living individuals in box cores (Gingras et al, 2008). Further support for inferring the existence of anthozoan cnidarians in Ediacaran ecosystems comes from divergence time estimates from molecular data, which suggest a split between Cnidaria and Bilateria in the Cryogenian, and the divergence of Medusozoa from (ancestral) anthozoans sometime in the Ediacaran Park et al, 2012).…”

Trace fossils from the Desejosa Formation (Schist and Greywacke Complex, Douro Group, NE Portugal):

“…socialis. The Rosselia in Figure 4 D, F and G shows some similarity with burrows that Mata et al (2012) interpreted as equilibrichnia behavior of sea anemones. Because the studied material always presents multiple concentric laminations with a mud or sandy central shaft and not a simple cylindrical burrow with a central shaft, the Desejosa material is better assigned to Rosselia than to plug-shaped burrows such as Bergaueria, Conichnus, or Dolopichnus.…”

Geobiology and palaeogenomics

“…Although the priapulids are the first organisms to exhibit a vertical component to their burrowing behavior, they were soon joined by other Cambrian benthic organisms which show vertical bioturbation (e.g., Mata et al 2012). The geobiological effects of this biological innovation of vertical bioturbation are very significant.…”

“…The addition of vertical bioturbation into the suite of processes resulting in deposition of sediments led to mixing of sediments after deposition and production of three-dimensional trace fossils, all resulting in the biogenic fabric termed ichnofabric. An environmental component in the evolution of deep vertical bioturbation has been documented, with its initial appearance in earliest Cambrian nearshore environments before expanding offshore (Mata et al 2012). Increase in bioturbation through time led to the increasing dominance of burrowing processes on the fabric seen in sedimentary rocks (e.g., Tarhan et al, 2015), with a concomitant reduction of the microbial processes that result in fabrics such as stromatolites or microbially-induced sedimentary structures (MISS) (e.g., Bottjer et al 2000).…”