What was the primary component of the main body mass of Wiwaxia, despite its armored exterior?

Soft tissue

A fundamental aspect of Wiwaxia's biology, which explains its scarcity in the fossil record outside of rare sites, is that its main body mass consisted overwhelmingly of soft tissue. Although it possessed protective hard elements—the sclerites covering the body and the prominent spines—the internal structure, including organs and musculature, was pliable and largely unpreserved under normal geological conditions. This reliance on soft tissue for the bulk of its structure highlights the evolutionary experiments of the Cambrian period, where some organisms adopted external partial armor while retaining a largely flexible internal organization, necessitating exceptional preservation conditions like those found in the Burgess Shale.