How do scientists know there was a particular plant/animal species that existed by now it’s extinct?

Question

I just want to understand how scientists conclude that animal/ plant species existed but has but became extinct a long time ago when we didn’t even exist at that time?

In: Biology

Answer 1

I’m not a scientist, but I feel like they have journals, illustrations, fossils, and bodies to confirm this. Of course, not everyone is 100% sure.