Ferruginol is a natural phenol with a terpenoid substructure. Specifically, it is a diterpene of the abietane chemical class, meaning it is characterized by three fused six-membered rings and alkyl functional groups. Ferruginol was first identified in 1939 by Brandt and Neubauer as the main component in the resin of the Miro tree (Podocarpus ferrugneus) and has since been isolated from other conifer species in the families Cupressaceae and Podocarpaceae. As a biomarker, the presence of ferruginol in fossils, mainly resin, is used to describe the density of these conifers in that particular biosphere throughout time. Background Ferruginol is a phenolic abietene, a type of tricyclic diterpenoid derived from terrestrial plants. It has a molecular composition of C20H30O with a molecular weight of 286 g/mole. Along with its presence in the Verbenaceae family, it has been found in a variety of conifer families including Podocarpaceae, the ancient Araucariaceae, and the extinct Cheirolepidiaceae. It is particularly useful as a biomarker because of its concentration in the Cupressaceae family. In these conifers, it acts as a plant metabolite, along with some protective and antibacterial roles. Preservation As a polar terpenoid, ferruginol was thought to have poor preservation potential. However, the discovery of resin fossils provided unaltered natural diterpenoids that can be used to understand botanical diversity during a given geological age. Analysis of macrofossils or clay sediments is also used to identify the presence of ferruginol, though these samples may not be fully preserved. Comparing the composition of fossilized coal or clay from the same region as resin fossils can indicate the original biological precursors of these samples. Additionally, the diagenetic alterations of fossils can be used to understand the environmental changes in the time after they were formed. General abietane diterpenoid abietic acids have been connected to the diagenetic products simonellite and retene. Microbial and abiotic degradation make it so most conifer biomarkers cannot be linked to specific species, so it is especially useful to find resinous samples that are able to provide more detailed identification. Due to the improved preservation of ferruginol and other diterpenoids in fossil resin, they have been found to be underrepresented in sediment samples when compared to angiosperms, whose leaf waxes are more free to disperse throughout the sample. Even in regions known to have a high abundance of conifers, sediment samples have been found to contain little to no unaltered diterpenoids. The relative of abundance