You might recall the oil and gas company BP (British Petroleum) the same company that destroyed the coastal waters down South, Gulf of Mexico had once upon a time a dinosaur as their logo.
Scientists believe the billions of gallons of petroleum beneath the Earth essential to our mechanized world, was created the same way as coal, as, except in the case of petroleum, the fossilization process occurring on the unimaginably numerous prehistoric creatures, mostly dinosaurs was transformed into petroleum, aka fossilized dinosaur remnants.
Some scientists aren't sold on the fossil fuel theory, claiming none of it is true. They say these fuels are not at all biological in nature, that they came to be in the process which created the Universe, the Earth.
Cartoonists might believe that, but a petroleum geologist and the related fields understand that oil fields are from ocean/lake sediment. That algae and the like, that can have oil squeezed out of it directly, when trapped in sediment and kept away from sufficient oxygen, yields the complex hydrocarbon molecules that we call crude oil.
Heat and pressure, which the abiotic theorists claim form crude oil, actually breaks down crude oil into the simpler, shorter and less complex molecules. We do this in modern refineries every day. Physics, entropy and the like isn't reversed because it is underground.
You may want apply a little analytic thinking to that theory. Why are all the world's commercial oil fields sourced to sedimentary basins? And if oil is magically formed from deep processes, why is it that areas where the deep rock is pushed up to the surface, like Hawaii, have little to no oil at all?
And you are confusing Sinclair with BP. Sinclair's justification of the symbol was the time period from which their oil was formed.