Figure 2.

(A) A suite of steroids coexisting in one fossil corresponds to the assemblage of steroids generated by diagenetic (pale yellow background) and catagenetic (dark yellow background) stages of the evolutionary pathways proposed by Mackenzie et al. (3, 4). A total of 70 individual steroids, including stenols, steradienols, stanols, stanones, sterenes, steradienes, diasterenes, diasteranes, mono- and triaromatic steroids, as well as 4-methyl substituted analogues (see Table 1 for quantification of steroids) occur in parallel. (B) Relative proportion of compound classes within the fossil is dominated by sterols and steranes, representing the bio- and geospheric end-members of a diagenetic sequence, respectively. (C) Ternary diagram of sterols (green) and steranes (blue) differentiate the fossil from the concretion matrix and the host rock. The C₂₇ dominance in the fossil layer is attributed to Crustacean tissue, whereas the matrix and host rock represent common algal input(s).