Same for fossils. Heavily forested areas often had soil too acidic to create fossils at all. Fossils take some real luck and the right conditions to make. Otherwise, bones just slowly disintegrated. I've seen estimates that 90%+ of species that ever existed left no fossil evidence.

It's also why there's large gaps in the Human and Great Ape fossil records. Australopithecus fossils appear in Chad, Ethiopia, Tanzania, and South Africa... And no where in between. But is not like none of them existed in the lush jungles of central Africa. The soil dissolved the bones. Same with gorillas. There are no gorilla fossils.