Oleanane has been reported in Upper Cretaceous and Tertiary source rocks and their related oils and has been suggested as a marker for flowering plants. Correspondence of oleanane concentrations relative to the ubiquitous microbial marker 17alpha-hopane with angiosperm diversification (Neocomian to Miocene) suggests that oleanane concentrations in migrated petroleum can be used to identify the maximum age of unknown or unavailable source rock. Rare occurrences of pre-Cretaceous oleanane suggest either that a separate lineage leads to the angiosperms well before the Early Cretaceous or that other plant groups have the rarely expressed ability to synthesize oleanane precursors.

The 18S ribosomal DNA molecular phylogeny and lipid composition of over 120 marine diatoms showed that the capability to biosynthesize highly branched isoprenoid (HBI) alkenes is restricted to two specific phylogenetic clusters, which independently evolved in centric and pennate diatoms. The molecular record of C25 HBI chemical fossils in a large suite of well-dated marine sediments and petroleum revealed that the older cluster, composed of rhizosolenid diatoms, evolved 91.5 +/- 1.5 million years ago (Upper Turonian), enabling an accurate dating of the pace of diatom evolution that is unprecedented. The rapid rise of the rhizosolenid diatoms probably resulted from a major reorganization of the nutrient budget in the mid-Cretaceous oceans, triggered by plate tectonics.