Interesting article on the Ediacaran biota. “The Ediacaran period, from 635 million to 541 million years ago, was a time of immense geological and evolutionary change. It witnessed the transition out of an ice-house climate, the break–up of one supercontinent (Rodinia) and the assembly of another (Gondwana), a major meteorite impact (the Acraman event) and unprecedented shifts in global ocean chemistry that included a significant rise in oxygen concentrations. Rocks from the Ediacaran also record the appearance of a diverse (species-rich) group of large, morphologically complex lifeforms: the Ediacaran biota. These organisms were globally abundant from about 571 million to 541 million years ago. To our modern eyes, many Ediacaran fossils look strange and unfamiliar, and they have puzzled palaeontologists for decades. Determining the position of these organisms in the tree of life is one of the biggest unresolved challenges in palaeobiology.
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Fossils of the Ediacaran biota preserve a record of large (up to 2 metres), biologically complex, mostly soft-bodied organisms, and are most commonly found as impressions of their external surfaces. The study of Ediacaran fossils has had a relatively brief history. It was only in the 1950s that they were confirmed to be older than the Cambrian, and the Ediacaran System to which they are now assigned was formally defined only in 2004. Importantly, their often unusual body plans mean that even very basic questions, such as ‘what were the Ediacaran biota?’, are still controversial. We need to answer such questions if we are to understand the early evolution of animals and, more broadly, the diversification and development of multicellular life. This article will briefly describe what we mean by the Ediacaran biota; look at previous suggestions of what they are likely to have been; and summarize the most recent thinking on how their appearance and (apparent) disappearance in the fossil record may relate to geological events.”
http://www.palaeontologyonline.com/articles/2017/fossil-focus-ediacaran-biota/
