CHARACTERS OF THE EDIACARAN: IDENTIFYING COMPLEX TRAITS IN EARTH’S EARLIEST FOSSIL ANIMALS

Soft-bodied macrofauna of the Ediacara Biota preserve the oldest definitive fossil evidence for complex animals. While it is widely accepted that derived metazoan groups existed during this time, most taxa remain phylogenetically enigmatic with respect to extant clades. Thus, the diversity of forms with ties to specific animal lineages and the complex traits they contain is likely severely under appreciated. Many have cited this as evidence for a disconnect between the Ediacara Biota and more ‘modern’ animals of the Phanerozoic. This likely results from the emphasis of many paleontological studies on classification over recognition of biologically and ecologically important traits. Recent analyses of both well-known and newly described Ediacaran fossils suggests a variety of metazoan-specific attributes (and their underlying developmental processes) can be recognized within this group. Here we highlight several examples of such traits, primarily among fossils from the Ediacara Member in South Australia. The identification of these characters implies that many taxa from this interval can be confidently assigned to specific metazoan groups and helps to illuminate critical steps in the advent and diversification of complex life.