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Since we did not analyze their organic remain, we cannot ascertain based on fossil morphology. Despite earlier researchers believed that those fossils are remains of animals,some non-animal single cell colonies or even extinct clade can leave similar fossil traces as well due to factors such as convergent evolution. Nowadays we can confirm dickinsonia is indeed an animal because of certain biochemical, like in this case cholesterol, preserved in the fossil. Since different clade of organism such as red algae, green algae, and animal use different type of steroid for their body structure, discovery of certain steroid like cholesterol in the fossil can confirm phylogeny relationship between the fossil discovery to modern clades if there relative still exists.
Bear in mind, the discovery only confirm that Dickinsonia is an animal while we cannot extrapolate other creatures such as trilobozoa as an animal unless we conduct similar analysis based on organic molecules found inside the fossils.