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

Because we have fossils preserving those animals remains.

Someone didn’t just come up with a Velociraptor one day, they found bones from one buried in the ground.