Dickinsonia

When Dickinsonia fossils were first described, scientists debated whether they were animals, lichens, giant protozoa, or something entirely separate from known kingdoms. Later work on fossil steroids and growth patterns points most strongly to an animal affinity, likely related to early bilaterians, but the debate forced biologists to confront how much of our taxonomy is based on modern forms. The fossil challenges our assumptions about what early life looked like. It shows that the first large organisms may have had body plans that no longer exist today, representing experiments in complexity that were later replaced by more familiar forms.

Most Ediacaran organisms left only faint impressions in sandstone, and many lineages may have died out without descendants. Dickinsonia is a reminder that the tree of life has whole branches that did not make it to the present. Our picture of evolution is built from rare pages that survived erosion. The fossil shows that extinction is not just about individual species, but about entire ways of being. The Ediacaran world was a different experiment in life, one that was largely replaced by the Cambrian explosion of familiar forms.