How did we identify fossil fuels to be remains of fossils, particularly those of dinosaurs?

The article explains the scientific methods used to identify fossil fuels as the remains of ancient life, debunking the common misconception that they primarily originate from dinosaurs. It details how physical evidence (plant imprints in coal), chemical markers (hopanoids, steranes in crude oil), and isotopic analysis (carbon-12 enrichment due to photosynthesis) confirm their organic origin. The article clarifies that oil and natural gas are mainly derived from ancient plankton and algae, while coal comes from ancient forests and swamps. The association of dinosaurs with fossil fuels is attributed to a 1930s marketing campaign by Sinclair Oil Corporation.