There were several supposed animal ancestors dated prior to the Avalon Explosion, but they there are other more likely interpretations. Supposed animal embryos and remains of simple animals are more likely multicellular microorganisms and residues of chemical processes in rock, respectively. Scientists interpreted a chemical signature in ancient rocks (635 Ma) as evidence of sponges, but a microorganism produces the same chemical. Lack of sponge spicules (hard parts of sponges) for the next 100 million years of the fossil record indicates that the chemical is from a microorganism. This causes a significant change in animal evolution models, many of which had sponges at the base. Another proposed animal ancestor is the ctenophore; however, genetics indicates that ctenophores are more distant than sea anemones from triploblastic bilaterian animals such as mollusks, worms, and crustaceans.

Avalon fossils are part of the Ediacaran biota. The interpretation of Ediacaran biota is difficult because this entire group of animal ancestors no longer exists. They look like bags or fronds. One group is the rangomorphs, such as Charnia masoni (566 Ma) (Figure 8‑2).

Oxygen, algae (food for animals), and nutrients increased in seawater just prior to the Avalon Explosion, which provided animals (heterotrophs) a food source and oxygen for respiration. One theory is that Avalon animals might have fed by absorbing nutrients from the water by osmosis, but Nicholas Butterfield determined that osmosis of nutrients from sea water could not provide sufficient food. [1] He identified the 3-dimensional structure in Charnia as compartments filled with water that served as an exoskeleton and as digestion chambers that processed recalcitrant (digest slowly) substrates (food). A microbiome (a set of microorganisms such as in the stomach and intestines of animals) inside the chambers might have processed the food. If there were internal cavities that processed food, then this would be a link to the eventual evolution of sea anemones and moving animals since they have internal cavities with microbiomes that process food; however, the difference between sea anemones and moving animals and these early Avalon organisms is that sea anemones and moving animals use muscles to actively trap and push food into their internal cavity. Charnia might have had two parts: an upper frondlike section (Charnia masoni) that was suspended above the sea floor and a lower holdfast (Charniodiscus) that anchored it to the sea floor.