Abstract
Sponges (phylum Porifera) are exclusively aquatic, sedentary, filter-feeding invertebrates, occupying essentially all benthic marine and some freshwater environments. With a worldwide fauna of at least 15,000 species (Hooper, 1994), poriferans are among the most diverse of sessile marine taxa. Sponges diverged from other animals earlier in evolutionary history than any other known animal group, extant or extinct, with the first sponge-related record in earth history found in 1.8 billion year old sediments, based on a demosponge-specific chemofossil, 24-isopropylcholestane (McCaffrey et al., 1994). The first morphological sponge fossils are known from the Early Vendian Doushantou phosphorites in China ( ;580 Milllion years ago; Li et al., 1998) and the Neoproterozoic (;550 my) Cloudina-Reefs of southern Na
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