The problem with the Ediacaran life forms is that we can't even be sure that they were animals. They may not even have been multicellular. They are so flat that it suggests either the need for transpiration through a single cell membrane or they could have photosynthesized in their tissues. I don't think that they were lichens as one biologist has suggested but they could have been some other sort of symbiotic forms. Some have three-part radial symmetry that is not seen again in the fossil record. I have a pet theory that they did not live on the sandy bottoms where they have been preserved but rather were plastered to the underside of ice floes. I do consider that they were a branch of life that dead ended when large multicellular forms appeared just before the Cambrian Explosion. Had this not happened they may not have evolved much further.