DNA preserved in bones undergoing fossilization deteriorates up to 50 times faster when stored in a museum than when the bones are buried in the ground.This study shows that in order to improve the quality of paleogenetic analyses, archeological and paleontological remains should be treated like biological samples both during and after excavation.
An extensive study of around 250 fossil bones from 600 to 50 000 year old herbivores showed that mitochondrial DNA from freshly excavated, untreated fossil bones was amplified with a success rate of 46%. However, the rate is a mere 18% for fossil bones from collections which have been washed, dried and stored.
Another finding revealed by this study was that the DNA had deteriorated as much in 57 years as during the previous two thousand years of burial. link