@MISC{Nichols_sponges:new, author = {Scott Nichols and Gert Wo Rheide}, title = {Sponges: New Views of Old Animals1}, year = {} }
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Abstract
Sponges (phylum Porifera) are exclusively aquatic, sedentary, filter-feeding invertebrates, occupying es-sentially all benthic marine and some freshwater en-vironments. 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 evo-lutionary 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-iso-propylcholestane (McCaffrey et al., 1994). The first morphological sponge fossils are known from the Ear-ly Vendian Doushantou phosphorites in China (;580 Milllion years ago; Li et al., 1998) and the Neopro-