Dinosaur fossils, it was long thought, are simple objects. The fossilization process leaves the overall shape of a dinosaur’s bones intact, but all the microscopic structures inside them — the blood cells, connective fibers, and other sorts of soft tissue — inevitably decay over time.
But that view is changing — and it’s possible that many ancient fossils may preserve more detail than meets the eye. The sort of biological tissue now being found in some fossils could tell us about dinosaur anatomy, behavior, and evolution in ways that weren’t possible just a few years ago.
https://www.vox.com/2015/6/9/8748035/dinosaur-fossil-blood-proteins
