Sources of C 30 steroid biomarkers in Neoproterozoic–Cambrian rocks and oils

Nettersheim et al.propose that unicellular Rhizaria are the likely biological source of the C₃₀ steroidal hydrocarbons found abundantly in Neoproterozoic–Cambrian sedimentary rocks. Their hypothesis challenges earlier research arguing that 24-isopropylcholestane (24-ipc) and 26-methylstigmastane (26-mes) are produced by demosponges and, therefore, early animal biomarkers2. Fundamental problems beset the new steroid biomarker data and its interpretation.