The Palaeobiology of Two Crown Group Cnidarians: Haootia quadriformis and Mamsetia manunis gen. et sp. nov. from the Ediacaran of Newfoundland, Canada

The Ediacaran of eastern Newfoundland preserves the world's oldest known eumetazoan body fossils, as well as the earliest known record of fossilized muscular tissue. Re-examination of the holotype of the eight-armed <i>Haootia quadriformis</i> in terms of its morphology, the arrangement of its muscle filament bundles, and hitherto undescribed aspects of its anatomy support its interpretation as a crown staurozoan. We also document several new fossils preserving muscle tissue with a different muscular architecture to <i>Haootia</i>, but with only four arms. This new material allows us to describe a new crown group staurozoan, <i>Mamsetia manunis</i> gen. et sp. nov. This work confirms the presence of crown group medusozoan cnidarians of the Staurozoa in the Ediacaran of Newfoundland circa 565 Ma.