Leonardo Was Not A Creationist

During a trip to an Apennine mountaintop, [Leonardo da Vinci] had discovered the fossilised remains of shellfish that ordinarily lived on the ocean floor. How did this come about? The conventional theological wisdom was that the Great Flood of Noah had inundated the mountaintops and carried the clams and oysters with it. Leonardo, remembering that the Bible says that the flood lasted only forty days, attempted to calculate whether this would be sufficient time to carry the shellfish with them, even if the mountaintops were inundated. During what state in the life cycle of the shellfish had they been deposited? — and so on. He came to the conclusion this didn’t work and proposed a quite daring alternative; namely, that over immense vistas of geological time the mountaintops had pushed up through the oceans. And that posed all sorts of theological difficulties. But it is the correct answer, as I think it’s fair to say it has been definitively established in our time.

~ Carl Sagan (born:1934-11-09 died:1996-12-20 at age:62) The God Hypothesis

The creationist explanation also fails to account for the various layers of shellfish, each with their own unique species.