Figure S2 Cross-section of a well-preserved spicule from the black shale of the Shuijingtuo Formation from Advanced adaptive strategies in an ancestral body plan: insights from a 510-Ma-old leptomitid sponge

Figure S2 Cross-section of a well-preserved spicule from the black shale of the Shuijingtuo Formation (Cambrian Stage 3), the same locality as the fossils reported in Luo et al.[20](A) Overview of the cross-section. (B–F) A closer view (B) and its elemental maps. The spicule was basically composed of silica (C–F), and the concentric structure is formed by differentiated dissolution of silica (B–C) and the filling of carbon in the dissolved pores (E). The carbon signal outside of the spicule comes from the resin in which the spicule is embedded.