how animal bones can be biodegradable? If so ,then why the fossils of animals, remain buried in the soil for millions of years without decomposition?
Animal bones are also subject to decay. Acids present in the soil are able to reduce a skeleton or bones into unrecognisable components, ​Fossilisation is a special process. Not all bones or other hard animal parts, that are buried in the soil, can turn into a fossil but this process require some unique conditions for a animal part like teeth or bone to get fossilised.