Fossil steroids record the appearance of Demospongiae during the Cryogenian period. Love, G. D, Grosjean, E., Stalvies, C., Fike, D. A, Grotzinger, J. P, Bradley, A. S, Kelly, A. E, Bhatia, M., Meredith, W., Snape, C. E, Bowring, S. a, Condon, D. J, & Summons, R. E Nature, 457(7230):718–21, Nature Publishing Group, feb, 2009.
Fossil steroids record the appearance of Demospongiae during the Cryogenian period. [link]Paper  doi  abstract   bibtex   
The Neoproterozoic era (1,000-542 Myr ago) was an era of climatic extremes and biological evolutionary developments culminating in the emergence of animals (Metazoa) and new ecosystems. Here we show that abundant sedimentary 24-isopropylcholestanes, the hydrocarbon remains of C(30) sterols produced by marine demosponges, record the presence of Metazoa in the geological record before the end of the Marinoan glaciation ( approximately 635 Myr ago). These sterane biomarkers are abundant in all formations of the Huqf Supergroup, South Oman Salt Basin, and, based on a new high-precision geochronology, constitute a continuous 100-Myr-long chemical fossil record of demosponges through the terminal Neoproterozoic and into the Early Cambrian epoch. The demosponge steranes occur in strata that underlie the Marinoan cap carbonate (\textgreater635 Myr ago). They currently represent the oldest evidence for animals in the fossil record, and are evidence for animals pre-dating the termination of the Marinoan glaciation. This suggests that shallow shelf waters in some late Cryogenian ocean basins (\textgreater635 Myr ago) contained dissolved oxygen in concentrations sufficient to support basal metazoan life at least 100 Myr before the rapid diversification of bilaterians during the Cambrian explosion. Biomarker analysis has yet to reveal any convincing evidence for ancient sponges pre-dating the first globally extensive Neoproterozoic glacial episode (the Sturtian, approximately 713 Myr ago in Oman).
@article{Love2009,
	Abstract = {The Neoproterozoic era (1,000-542 Myr ago) was an era of climatic extremes and biological evolutionary developments culminating in the emergence of animals (Metazoa) and new ecosystems. Here we show that abundant sedimentary 24-isopropylcholestanes, the hydrocarbon remains of C(30) sterols produced by marine demosponges, record the presence of Metazoa in the geological record before the end of the Marinoan glaciation ( approximately 635 Myr ago). These sterane biomarkers are abundant in all formations of the Huqf Supergroup, South Oman Salt Basin, and, based on a new high-precision geochronology, constitute a continuous 100-Myr-long chemical fossil record of demosponges through the terminal Neoproterozoic and into the Early Cambrian epoch. The demosponge steranes occur in strata that underlie the Marinoan cap carbonate ({\textgreater}635 Myr ago). They currently represent the oldest evidence for animals in the fossil record, and are evidence for animals pre-dating the termination of the Marinoan glaciation. This suggests that shallow shelf waters in some late Cryogenian ocean basins ({\textgreater}635 Myr ago) contained dissolved oxygen in concentrations sufficient to support basal metazoan life at least 100 Myr before the rapid diversification of bilaterians during the Cambrian explosion. Biomarker analysis has yet to reveal any convincing evidence for ancient sponges pre-dating the first globally extensive Neoproterozoic glacial episode (the Sturtian, approximately 713 Myr ago in Oman).},
	Author = {Love, Gordon D and Grosjean, Emmanuelle and Stalvies, Charlotte and Fike, David A and Grotzinger, John P and Bradley, Alexander S and Kelly, Amy E and Bhatia, Maya and Meredith, William and Snape, Colin E and Bowring, Samuel a and Condon, Daniel J and Summons, Roger E},
	Doi = {10.1038/nature07673},
	File = {:Users/abradley/Documents/Mendeley{\_}Library/Love et al/2009/Love et al.{\_}2009{\_}Fossil steroids record the appearance of Demospongiae during the Cryogenian period.pdf:pdf},
	Issn = {1476-4687},
	Journal = {Nature},
	Keywords = {Ancient,Animals,Arabia,Biological Evolution,Biological Markers,Biological Markers: analysis,Biological Markers: chemistry,Cholestanes,Cholestanes: analysis,Cholestanes: chemistry,Cholestanes: isolation {\&} purification,Fossils,Gas Chromatography-Mass Spectrometry,Geologic Sediments,Geologic Sediments: chemistry,History,Hydrocarbons,Hydrocarbons: analysis,Hydrocarbons: chemistry,Ice Cover,Oceans and Seas,Oxygen,Oxygen: analysis,Porifera,Porifera: physiology,Seawater,Seawater: chemistry},
	Month = {feb},
	Number = {7230},
	Pages = {718--21},
	Pmid = {19194449},
	Publisher = {Nature Publishing Group},
	Title = {{Fossil steroids record the appearance of Demospongiae during the Cryogenian period.}},
	Url = {http://www.ncbi.nlm.nih.gov/pubmed/19194449},
	Volume = {457},
	Year = {2009},
	Bdsk-Url-1 = {http://www.ncbi.nlm.nih.gov/pubmed/19194449},
	Bdsk-Url-2 = {https://doi.org/10.1038/nature07673}}

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