Figure 3 : Structural features of the fossil sponge skeleton.

From: Discovery of 505-million-year old chitin in the basal demosponge Vauxia gracilenta

Figure 3

A selectively isolated fragment (b) of the aspiculate fibrous skeleton of V. gracilenta (a) shows autofluorescence (c) that is characteristic for chitin. The non-homogenous fluorescence can be explained by the presence of a residual mineral phase observed using SEM (d, e).