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-debateAtlas home / References / Fossil steroids record the appearance of Demospongiae during the Cryogenian period
References / paperFossil 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.
Year2009
Source roleprimary-study
DOI / ID10.1038/nature07673
Fitness and scope
range · methods · taxonomy
Reports 24-isopropylcholestanes in South Oman Salt Basin rocks and oils; source attribution is evaluated separately from compound occurrence.
Claim ledger
Cryogenian sterane records used on the Demospongiae route are a contested geochemical attribution to sponge-grade sources; they do not establish a demosponge crown origin, body fossil or global first appearance.
claim:taxon:demospongiaeDemospongiae is displayed at 635–0 Ma only as a contested biomarker-to-living navigation anthology: Cryogenian 24-isopropylcholestanes are not taxonomically exclusive to demosponges and do not establish a body-fossil FAD, crown origin or continuous global occupancy.
claim:taxon:demospongiae:range-boundary-rc50