Late Neoproterozoic Metazoa: Weird, Wonderful and Ghostly

Abstract

The Late Neoproterozoic or Ediacaran biota contains a variety of enigmatic fossils of uncertain, but likely metazoan, affinities. The protistan group Choanoflagellata and Metazoa share a common ancestor predating the first fossils by perhaps 100's of millions of years. Sponge choanocytes closely resemble choanoflagellates, establishing a morphologic similarity as well. Fossils in the late Neoproterozoic may represent stem or early groups of cnidarians, while others resemble eumetazoans and bilaterians. These organisms occurred on all continents except Antarctica, and occupied four major habitats from prodeltaic to deep slope environments in each area. Their paleoecology was complex but similar to modern soft-bodied slope organisms. Ediacaran trophic structures were complex as well and included a wide variety of feeding types from detritovores, herbivores on microbial mats, filter-feeders, and predators. Ediacaran assemblages thus constitute the evolutionary and ecological precursors of later Phanerozoic and modern biotas.