Sterols in a unicellular relative of the metazoans

  title={Sterols in a unicellular relative of the metazoans},
  author={Robin B. Kodner and Roger Everett Summons and Ann Pearson and Nicole King and Andrew H. Knoll},
  journal={Proceedings of the National Academy of Sciences},
  pages={9897 - 9902}
Molecular clocks suggest that animals originated well before they first appear as macroscopic fossils, but geologic tests of these hypotheses have been elusive. A rare steroid hydrocarbon, 24-isopropylcholestane, has been hypothesized to be a biomarker for sponges or their immediate ancestors because of its relatively high abundance in pre-Ediacaran to Early Cambrian sedimentary rocks and oils. Biolipid precursors of this sterane have been reported to be prominent in several demosponges… 

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