PRIAPULID TRACE FOSSILS FROM THE LATE EDIACARAN OF NAMIBIA

Latest Ediacaran to earliest Cambrian trace fossils preserve evidence for the early evolution of metazoan complexity and behaviors, as well as the onset of critical geobiological changes that continued into the Paleozoic (the ‘agronomic revolution’). Here we present an unusual suite of trace fossils from the late Ediacaran Nasep-Huns transition (Nama Group, Namibia) potentially referable to Archaeichnium haughtoni Glaessner 1963, and which bear strong resemblance to priapulid burrows from the lower Cambrian Haidar Formation of Sweden. Of particular note are the two distinct surface patterns present on this material, exhibiting both distal longitudinal striations consistent with scalidophoran probiscides, as well as transversely-annulated proximal sections reminiscent of priapulid caudal anatomy. Furthermore, these traces appear to dip below the sediment surface and reemerge consistent with the directions of motion, similar to modern priapulid burrows produced under experimental conditions. Attribution of these traces to priapulids would thus represent among the oldest records of crown-group Ecdysozoa, pushing their first appearance beneath the base of the Cambrian. Furthermore, this finding would illustrate that complex bioturbative -- and perhaps predatory -- animal behaviors evolved prior to the Ediacaran-Cambrian boundary, and may have played a prominent role in structuring benthic communities over the Ediacaran-Cambrian transition.