Cryogenian-to-Cambrian 24-isopropylcholestanes are measured compounds, but sampled Rhizaria can synthesize their sterol precursors, so these rocks do not uniquely establish Demospongiae.
claim:event:cryogenian-sponge-biomarker-debateCryogenian sponge-biomarker attribution test
Rock-bound steranes establish a chemical occurrence, while living-protist assays prevent a unique demosponge source assignment.
Represented range635–541 Ma
RegionsSouth Oman Salt Basin, Sultanate of Oman
CladesDemospongiae · Rhizaria
Claim ledger
References
- Fossil steroids record the appearance of Demospongiae during the Cryogenian periodLove, 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. · 2009 · DOI 10.1038/nature07673
- Putative sponge biomarkers in unicellular Rhizaria question an early rise of animalsNettersheim, B.J.; Brocks, J.J.; Schwelm, A.; Hope, J.M.; Not, F.; Lomas, M.; Schmidt, C.; Schiebel, R.; Nowack, E.C.M.; De Deckker, P.; et al. · 2019 · DOI 10.1038/s41559-019-0806-5