In general my understanding is coal was trees, oil was mostly algae and plankton, and mostly started forming well before the first true dinosaurs.

Technically some of that plankton would be considered animals, though probably not something you’d easily recognize as being an animal (side-note: I’d be curious to hear some vegetarians/vegans weigh in on the theoretical ethics of eating zooplankton)

I’m sure there’s some edge cases, traces of more complex animals and such getting mixed in with dead plankton, and at the end of the day carbon is carbon regardless of where it comes from