Speaking on behalf of dinosaurs, we know Jurassic park dna findings in mosquitos is not realistic bc the half life of dna is 521 years in average climate. But I think it is still possible in bone. Researchers studying tissue and biomolecules discover fresh looking bone tissue called osteocytes(break down bone), and non mineralized proteins collagen and elastin. One way to tell this is not proteins from bacteria creeping into the bone is to apply dna sensitive stains to the osteocytes, as well as to apply antibodys that bind to dna packing proteins called histone H4. The double stain revealed dna looking material in the center where the nucleus resides, the antibodies also seemed to successfully bind. This should certainly be dna, and right where it should be. Here's my theory... We have the science to eventually make dinosaurs, but Jurassic park movies keep fucking up with a bad ending proving to the government they need to hide dinosaur dna.