shark tooth

These well-preserved fossils of an ancestor of the bluntnose six-gilled shark, which lived somewhere between 50 and 250 million years ago. I found them in the same bucket with sand, shells, pebbles and gravel in a dried base for mud and gravel from the Scheldt in Antwerp when they made it deeper. I think they must have lived there. I assume that the ground was never disturbed before that work took place. The teeth in the photo belong to an adult and an adolescent. There can be millions of years between the two and it could also be that the adult saw the smaller one for lunch and lost some teeth while dining.