TRI-AL AND ERROR: THREE-FOLD SYMMETRY IN THE EDIACARAN OF SOUTH AUSTRALIA

The Ediacara Biota, which represents the first macroscopic, multicellular complex communities on Earth, is composed of organisms with a wide range of morphologies, many of which are so unusual that the taxonomic affinities of these organisms remain largely enigmatic. One of the most distinctive body plans in the Ediacaran is tri-radial symmetry. There are multiple tri-radially symmetric taxa amongst the Ediacara Biota, but the tri-radial body plan is unique to this time. Although abundant and diverse in the Ediacaran, representing ~12-15% of the taxonomic diversity of the White Sea assemblage; today, there are no organisms with completely tri-radial body plans, nor is there evidence in the fossil record for them after the Ediacaran. Many tri-radial taxa have been included in a morphogroup referred to as Trilobozoa or Triradialomorpha, that has been defined solely on symmetry. Many specimens of these tri-radial taxa exist at the Nilpena National Heritage Ediacara fossil site and at other sites throughout Australia, and the diversity and abundances of these taxa in South Australia provide a unique venue for research investigating the relationships among these Ediacaran taxa. By analyzing the occurrence and diversity of tri-radial genera from the Australian Ediacaran, including Tribrachidium, Rugoconites, Albumares, Anfesta, Coronacollina, Hallidaya, and Skinnerawe can evaluate the possibility that their shared symmetry unites them phylogenetically. With the exception of Coronacollina, we find that these taxa are morphologically similar enough to support the possibility that these fossils represent a single clade of related organisms.