SSU rRNA secondary structure of the demosponge Amphimedon queenslandica (Haplosclerida). Nucleotides conserved in Demospongiae at the 90% level are shown in black, other nucleotides are in grey. Nucleotides at positions that are present in demosponges above the 90% consensus level but differ from A. queenslandica nucleotides are shown with an arrow pointing to their corresponding position. Specific insertions for A. queenslandica that are atypical for demosponges are displayed in shaded frames. Outlined frames highlight the regions of insertion within Haplosclerida that are displayed as sketches in Fig. 6. Inset: 90% consensus sequence and structure of partial helix 43 for 76 demosponges that do not belong to the marine haplosclerids.