DEVELOPING A PICTURE OF EARLY ANIMAL EVOLUTION: IDENTIFYING REGULATORY ELEMENTS IN THE EDIACARA BIOTA (Invited Presentation)

The Ediacara Biota represents the oldest macroscopic fossil evidence for animals in the geologic record. Although commonly regarded as an enigmatic assemblage with little relationship to modern taxa, investigations focused on the paleobiology and paleoecology of these ancient organisms reveal a variety of distinct characters. At the same time, studies of developmental processes uncover highly conserved genetic controls responsible for producing particular traits in living organisms. Here, we combine these methods to identify developmentally relevant features in fossil taxa from the Ediacara Biota and their likely underlying regulatory elements. This demonstrates that a number of metazoan specific gene regulatory networks were present in multiple, morphologically disparate Ediacaran taxa and helps refine our understanding of their phylogenetic relationships. The morphology of such fossils suggests an increase in the extent of cellular differentiation and body regionalization through the Ediacaran and into the Cambrian. This may reflect an increase in the complexity of interactions between existing transcription factors in these early animals. We also find evidence for rudimentary nervous systems in Ediacaran bilaterians lacking a head or ventral nerve chord. This supports previous suggestions that these evolved independently in unrelated bilaterian clades and that there was a significant period between the advent of sensory machinery and the development of a central nervous system.