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Project Progress

The application of molecular biomarkers to the study of early metazoan evolution has received relatively little attention, but has much to commend it since primitive, soft-bodied animals are likely to have had poor physical preservation and little potential for leaving a trace fossil record. Sponges, which are almost certainly a paraphyletic grade at the base of the animal tree, are known to synthesize numerous de novo. 24-Isopropylcholesterols are one type of distinctive steroid and a possible molecular marker for sponges since this and related structures appear to be ubiquitous lipid components of the demosponges. Choanoflagellates, the nearest living protistan relative of sponges have not yet been shown to make this sterol (Kodner et al., 2008).

Algal steroids are also of great interest. The Neoproterozoic period marks the inception of steroid production on a massive scale and is a potential indicator of increasing importance of complexity life in the oceans.