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Dickinsonia is one of the oldest macroscopic metazoans in the fossil record. Determining the biological characters of this extinct taxon is critical to our understanding of the early evolution of life. Preservation of abundant specimens from the Ediacara Member (Rawnsley Quartzite), South Australia, in a variety of taphonomic states allows the unparalleled opportunity to compare the biomechanical responses of Dickinsonia tissue to various forces with those typical of modern organisms. Dickinsonia are found as lifted, transported, folded, rolled, ripped, and expanded or contracted individuals, while maintaining diagnostic morphology. This suite of characters indicates that Dickinsonia was composed of material that was flexible, difficult to rip, and capable of elastic and plastic deformation. While none of these traits are diagnostic of a single biomaterial component, we find many similarities with modern biopolymers, particularly collagen, keratin, and elastin. Maintenance of significant relief following complete tearing suggests that Dickinsonia was composed of relatively thick tissues, signifying higher oxygen requirements than previously hypothesized. The ability to be transported and still be preserved as recognizable fossils is unique amongst the Ediacara Biota and demonstrates that Dickinsonia was a taphonomic elite. Combined with discovery in multiple environmental settings, this indicates that the absence of Dickinsonia represents the likely extinction of this organism prior to the Nama assemblage, possibly due to a decrease in the global availability of oxygen in the latest Ediacaran.

Patterns of origination, evolution, and extinction of early animal life on this planet are largely interpreted from the fossils of the Precambrian soft-bodied Ediacara Biota, spanning nearly 40 m.y. of the terminal Ediacaran period. Localities containing these fossils are loosely considered as part of either the Avalon, White Sea, or Nama Associations. These associations have been interpreted to have temporal, paleobiogeographic, preservational, and/or paleoenvironmental significance. Surprisingly, elements of all three associations occur within the Ediacara Member of the Rawnsley Quartzite of South Australia. An analysis of over 5000 specimens demonstrates that fossil distribution is strongly controlled by facies and taphonomy rather than time or biogeography and that individual taxa vary considerably in their environmental tolerance and taphonomic integrity. The recognition that these taxa represent organisms living in various distinct environments, both juxtaposed and shared, holds strong implications for our interpretation of the record of early animal life on this planet and questions the biostratigraphic utility of the three associations. Furthermore, although in situ soft-bodied preservation provides a unique perspective on composition of benthic fossil assemblages, the record should not be interpreted as a simple “snapshot”. Fossil beds represent a range of preservational modifications varying from current winnowed census samples of benthic communities at different depths and ecological maturity, to entirely transported assemblages. Unless the appropriate environments and taphonomic conditions are present for certain taxa, the absence of a particular taxon may or may not indicate its extinction in space or time.

The apparent lack of taxonomic continuity between the Precambrian and Cambrian fossil records has led to controversial and conflicting interpretations about the Ediacara biota and their place in the evolution of metazoan life on this planet. This has been further complicated by the absence of similar modes of construction between these faunas and the rarity of Precambrian skeletonized fossils. We describe a new Ediacaran organism that represents the oldest multielement organism with structural support through either biomineralization or chitin. Coronacollina acula gen. et sp. nov. from the Ediacara Member (Rawnsley Quartzite) was constructed from a framework of rigid and brittle elements that disarticulated after death. It reveals a constructional mode not recognized previously among members of this assemblage, but one that was prevalent among Cambrian organisms. Coronacollina consists of a truncated cone associated with spicules, up to 37 cm in length, diverging radially from the cone. This constructional morphology is similar to the Cambrian Choia , a low conical demosponge with a corona of long spicules, providing a long-predicted constructional link between the Ediacara biota and the Cambrian fossil record.

The Ediacara Biota, Earth’s earliest fossilized ecosystem of complex, macroscopic, multicellular organisms, occurs in terminal Ediacaran strata worldwide, yet how the fossils are preserved remains controversial. Ediacara assemblages consist of exceptionally preserved soft-bodied forms of enigmatic morphology and phylogenetic affinity. Many of these fossil assemblages are anactualistically preserved as casts and molds in sandstones (“Ediacara-style” preservation). Here we present evidence from the Ediacara Member of South Australia that Ediacara-style preservation was due to rapid, early-stage precipitation of silica cements, facilitated by the high silica saturation state of the oceans prior to the appearance of prolific silica biomineralizers. An early silicification model provides a coherent, mechanistic and empirically supported explanation for the widespread preservation of soft-bodied organisms of Ediacaran–early Paleozoic age as sandstone casts and molds. The prevalence of early silicification confirms that Ediacara-style fossil assemblages can provide an accurate window into life on the Ediacaran seafloor that can be used to reconstruct critical steps in the development and diversification of early animal ecosystems.

We report the preservation of the eight-armed Ediacara fossil Eoandromeda octobrachiata as carbonaceous compressions in the Doushantuo black shale of south China and as casts and molds in the Rawnsley Quartzite in South Australia. The contrasting preservational styles in two taphonomic windows indicate that E. octobrachiata may have had a relatively recalcitrant organic integument, which rules out its close comparison with giant agglutinated foraminifers such as xenophyophores. Its octaradial symmetry and dextrally spiraling arms suggest that it may be a diploblastic-grade animal sharing some features with cnidarians and ctenophores, although its phylogenetic affinity remains open. It is the first and only unambiguously identified Ediacaran macrofossil that occurs in two drastically different taphonomic windows, thus bridging the conventional biological and taxonomic gaps between the Ediacara and Miaohe biotas, which collectively record the earliest known macroscopic and complex life.

Newly discovered fronds of the Ediacaran index fossil Charnia from the Drook Formation of southeastern Newfoundland are the oldest large, architecturally complex fossils known anywhere. Two species are present: Charnia masoni , originally described from Charnwood Forest in central England and now known worldwide, may have ranged through as much as 30 m.y. of Ediacaran time, and C. wardi sp. nov., a new species of Charnia that consists of slender fronds to nearly 2 m in length, is the longest Ediacaran fossil yet described anywhere. These fossils, which are present midway between the glacial diamictites of the Gaskiers Formation (ca. 595 Ma) and the classic Ediacaran assemblage of the Mistaken Point Formation (565 ± 3 Ma) 1500 m higher in the same section, provide our first glimpse of complex megascopic life after the meltdown of the “snowball Earth” glaciers.

We document for the first time the occurrence of the complex trace fossil Treptichnus from the terminal Proterozoic Nama Group, Namibia. These traces differ in detail from the Cambrian index fossil Treptichnus pedum , but document precursors with the same basic behavior. The producer of the trace is not known. In its complexity, however, this trace fossil provides strong evidence for advanced latest Proterozoic bilaterians.

Studies of sedimentary fabrics and trace fossils across the Precambrian-Cambrian interval in South Australia demonstrate that the appearance of Treptichnus pedum , which defines the base of the Cambrian, also marks the initial development of preservable infaunal activity. There is a significant shift in the amount and nature of bioturbation at this time. These results support the broad-scale utility of T. pedum as the indicator of the base of the Cambrian.