I don't know if this helps or not but you would want to know the age of the rock (absolute dating) and from there you will be able to know the age of the fossil and what caused it to die.
You can't have a carrier with a dominant pedigree because other wise than individual or organism would be afflicted by the gene and render them incapable of being a carrier. A carrier is an individual/organism that has a normal phenotype (meaning it is not afflicted by said gene) but is carrying the gene that could cause disease or whatever the affect may be. In this case the gene would have to be homozygous recessive to be expressed. Hopefully this helps!
