What are they? Ediacarans are a highly distinctive assemblage of fossil organisms, apparently all marine. Most typical are frondose, discoidal and segmented forms. Their overall taxonomic diversity is modest, but there is considerable disparity and they include one rather bizarre group with prominent three-fold body symmetry. A striking feature of many forms is their modular construction and their sometimes fractal growth pattern. Ediacarans appear in the latest Precambrian, towards the end of the Neoproterozoic, ranging between ca. 570–550 million years ago, but some of them even trickle into the Cambrian. You said organisms, why not animals? That is the problem; exactly what are the Ediacarans? Preconceptions, wild imagining and special pleading litter the field. The majority view regards them as metazoans, but the assignments to known animals can be a pretty procrustean procedure. Some of the fronds are probably sea-pens, but the jellyfish-like discs are more likely to be the holdfasts of fronds. Through some eyes the Ediacaran sea-floor was also host to molluscs and arthropods, but none of these interpretations looks quite ‘right’. So what are the alternatives? There are some pretty radical proposals on the table. Bizarre, mattress-like forms, the so-called vendobionts, are probably giant syncitial protistans. Maybe the Ediacarans were a parallel attempt at achieving a metazoan grade of organization, but where they fit into eukaryote phylogeny is largely guesswork. Other ideas? Even fungi and lichens have been suggested as possible homes. Do you begin to see the problem? Did they live in communities? One careful study of Ediacarans from Newfoundland demonstrated both a community structure and an ecological succession. This in turn was used to support the idea of Ediacarans as Metazoa. Hang on, not so fast! Remember, there are universals of biological scaling, including energy flow. So an alternative is that Ediacarans built analogous ‘para-communities’. Any other problems? Yes. Ediacarans lack hard skeletons, yet the fossil preservation of their soft-parts has almost no counterpart to the classic examples of soft body fossils, such as those found in the Burgess Shale. One important factor was the presence of abundant microbial mats that covered the seafloor. These acted as ‘death-masks’, trapping the Ediacarans and facilitating very fast fossilization. But that cannot be the entire story. At least the vendobionts may have had a more robust composition than once thought. Where are Ediacaran fossils found? Practically everywhere. Children sliding down the outcrops in Charnwood Forest in England are polishing Ediacarans. About 570 Mya this locality was next door to eastern Newfoundland, where spectacular bedding planes reveal seafloors frozen in time, buried by volcanic ash, a bit like Pompeii. Otherwise Ediacaran tourists should head for such classic localities as the Flinders Ranges (Australia) or White Sea (Russia). Did they evolve? What a strange question! Clearly they evolved from something, but from what? In addition, the idea that there is an evolutionary succession is now under scrutiny. What is clear is that there are three principal Ediacaran assemblages, and each is controlled by specific environmental conditions. However, when you track each assemblage through geological time there is effectively no change within it. Another puzzle is that there is little evidence for species diversity changing along latitudinal gradients. Once again, the Ediacarans don't readily fit into pre-conceived moulds. Should we care? Very much; Ediacarans are an enigma. Overall, it looks like they were multiple experiments in multi-cellularity, and interestingly all occurred at about the same time. Some are presumably protistans, others probably metazoans. Amongst the latter, there may be stem-group cnidarians and triploblasts. Much is uncertain, so there is plenty to play for. Ediacarans are quite different from what we expected. The moral is simple: trust nature rather than textbooks.