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Abstract

Sponges are probably the earliest branching animals, and their fossil record dates back to the Precambrian.
Identifying their skeletal structure and composition is thus a crucial step in improving our understanding of
the early evolution of metazoans. Here, we present the discovery of 505–million-year-old chitin, found in
exceptionally well preserved Vauxia gracilenta sponges from the Middle Cambrian Burgess Shale. Our new
findings indicate that, given the right fossilization conditions, chitin is stable for much longer than previously suspected. The preservation of chitin in these fossils opens new avenues for research into other ancient fossil groups.